AVIATION
Flight " Copyright Photo
A remarkable snap-shot of a 6o-h.p. Daperdussin monoplane flying within three yards of
the camera. The staff photographer of Flight secured this picture by standing on No. i
pylone at the Hendon aerodrome while a race was in progress. The pilot on the aeroplane is
N. Slack, and the passenger's seat in front of the pilot is empty. The pilot is in the act of
turning the control wheel for warping the wings in order to level up from the banked turn.
AVIATION
AN INTRODUCTION TO THE
ELEMENTS OF FLIGHT
-
BY
ALGERNON E. BERRIMAN
TECHNICAL EDITOR OF "FLIGHT" AND THE " AUTO "
ASSOCIATE FELLOW OF THE AERONAUTICAL SOCIETY
MEMBER OF THE INSTITUTION OF AUTOMOBILE ENGINEERS
WITH THIRTY PLATES AND MANY DIAGRAMS
LONDON: METHUEN & GO. LTD.
NEW YORK
GEORGE H. DORAN COMPANY
PREFACE
THERE is an ever-increasing number of people who
desire to appreciate the main issues of technical
subjects unconnected with their own professions :
to such, primarily, I address this Introduction to the study
of flight.
There is no evading the fundamental technology of any
real subject, whether commercial, scientific, or political by
nature ; the reader must ever provide the interest if he
would receive any return whatsoever for his purchase of
the author's capital. In this case, as the capital is so small,
the initial interest on the reader's part must be all the
greater.
The scope of the book is indicated by the arrangement
and character of the chapters. I have divided the treat-
ment of the subject into four main parts. The first part
relates to the fundamental principles of flight ; the second
part is concerned with practical accomplishment ; it refers
in detail to the work of certain notable pioneers like Lilien-
thal and the Wrights, and also has chapters on modern
development, as demonstrated, for example, at the military
aeroplane trials of 1912. The third part is mainly historical,
and is placed in this order so that the significance of the
" milestones " may more readily be appreciated.
The fourth part is a collection of appendices that have
no exact sequence or proper place in the body of the book.
Among these I have included several simple numerical
examples that may be of some assistance to the student.
In any case, there is nothing like a few specific questions
and answers as an assistance to fixing ideas on a strange
subject.
361250
vi AVIATION
As far as possible, I have drawn upon the admirable
Technical Report of the Advisory Committee for the results
of experimental research. It is the source to which all
students should first turn for data of this character.
The pictures in this book are a few of the many hundreds
that are prepared in the usual course by the staff of Flight,
and are typical of the illustrations that appear in that
journal every week. It is, of course, on the periodical that
the reader who would remain au fait with current develop-
ments must necessarily rely for immediate information, and
if this book succeeds in assisting those who read it to follow
the later steps of this new movement with greater interest
and appreciation of detail, it will have served its purpose
well.
A. E. B.
LONDON, September, 1913
CONTENTS
PART I
PAGE
I INTRODUCTION . . . « . . xix
An early flight meeting in France— When aeroplanes become common-
place— The Great Unflown — The first time up — High speed in the air —
Sensations in the glide.
CHAPTER I
WHAT AN AEROPLANE IS . . . I
Getting under way — What the wings do in flight — Relative motion —
A railway carriage experiment — The effect of the angle — Why aero-
planes are like yachts — How birds soar — Why power is necessary to
flight — Nature flaps a wing — Man revolves a propeller — What happens
when the engine stops— Gliding on an aerial toboggan — Kites flying in
the wind — Pros and cons of the cambered wing — Natural stability —
The need for a tail — Advantages of flying high.
CHAPTER II
THE INSTRUCTIVENESS OF PAPER MODELS . . . IO
Natural stability in a simple form — Flat v. cambered wings — Why
aeroplanes are broader than they are long — The "T" test — Why an
arrow flies straight— The Centre of Pressure and the Centre of Gravity —
The purpose of the tail.
CHAPTER III
SOME CONSTRUCTIONAL FEATURES OF THE MODERN
AEROPLANE . . . . 17
Aeroplanes compared with birds — Monoplanes and biplanes — Diffi-
culties about length — Span, chord, and gap — Why the centre of pressure
does not stay still— When flight was impossible— W7hat Sir George Cayley
knew — How an aeroplane is steered — What the elevator is for —
Characteristic features of design.
CHAPTER IV
EQUILIBRIUM IN THE AIR * . . 38
Equilibrium and stability— Pitching, yawing, and rolling— Recovery
of balance — The importance of practice — Steadiness in flight.
viii AVIATION
CHAPTER V
PAGE
LATERAL BALANCE . . . ... 46
Direction of pressure and direction of weight — The cause and the cure
of lateral disturbances — Steadiness and large span — Speed and safety —
Wing warping : its object and its effects — Cause and effect of sideslip —
Fins as stabilizers — Upturned wing tips as fins — Stability against gusts —
Negative wing tips and lateral stability.
CHAPTER VI
STEERING . . . . ... 57
The true purpose of a rudder — Its manner of action — How a ship
answers the helm — The balance of power — Instability and the importance
of the rudder — Banking for the turn — The centrifugal couple — The differ-
ential negative warp.
CHAPTER VII
LONGITUDINAL STABILITY . . ... 67
The ballasted flat plate and wing of single camber— The fore-and-aft
dihedral as a speed regulator — Stalled — The dive — An experiment by
Orville Wright —The reversed camber wing — The Fales section.
CHAPTER VIII
PRINCIPLES OF PROPULSION . . ... 79
Propeller in front v. propeller behind — Two screws v. one — Military
requirements — Size and efficiency — Size and speed of flight — Rankine's
theory — Wing v. propeller — Aeroplane v. helicopter — Aero engines.
CHAPTER IX
CONCERNING RESISTANCE . . ... 89
Wing resistance and body resistance — Streamline flow — Relative im-
portance of the head and the tail of a body — Fair-shaped struts — The
gain in lift due to reduction or resistance — Surface friction.
CHAPTER X
THE CAMBERED WING . . . 96
Lilienthal's research — The cambered wing compared with the flat
plate — The tangential — Advantages of uneven distribution of pressure.
PART II
INTRODUCTION . . . ... Io8
CHAPTER XI
THE WORK OF OTTO LILIENTHAL . . . . IIO
Bird flight as the basis of aviation — The invention of gliding — Ex-
periments at Rhinow — The artificial hill — Researches on the cambered
plane — Lilienthal's tangential.
CONTENTS ix
CHAPTER XII
PAGE
THE WORK OF WILBUR AND ORVILLE WRIGHT . . . I2O
The first inspiration — The introduction of wing warping — Experiments
at Kitty Hawk — Camber and the centre of pressure — Testing the glider
as a kite — The ominous wind tap — Building the engine — The successful
flights.
CHAPTER XIII
THE WORK OF VOISIN AND FARM AN . . . 132
Early experiments on the Seine — The first aeroplane factory— Dela-
grange as the first customer — The early Voisin biplane — An English pupil
— Farman's successful circular flight — Farman becomes a constructor.
CHAPTER XIV
THE WORK OF DUNNE AND WEISS .. . . .141
Experiments on the hill-side — Soaring flight in the wind — The Dunne
aeroplane — Its negative wing tips.
CHAPTER XV
THE BRITISH MILITARY TRIALS OF IQI2 . .; . 147
Assembling in fifteen minutes — The three hours' flight — Wind tests —
Measuring the gliding angle — Cody's victory.
•
CHAPTER XVI
HYDRO-AEROPLANES . „ . . . 152
[This chapter is abstracted from a report on the meeting of Hydro-
aeroplanes held at Monaco in April, 1913, prepared by the author for the
Aerial Defence Committee of the Navy League.]
CHAPTER XVII
ACCIDENTS . . , . . . . 161
The importance of debris — Formation of the Investigation Committee
—The Rolls accident— Wind shocks— Trick flying and its dangers-
Upside-down in mid-air — Parke's dive — The risks of flying with an
underpowered engine.
PART III
INTRODUCTION . . " . ... 1 72
CHAPTER XVIII
ROMANCE AND EARLY HISTORY . . . 174
Birds as an inspiration to man — Leonardo da Vinci as a designer —
A bishop as an inventor — The impossibility of man flight.
AVIATION
CHAPTER XIX
PAGE
THE COMING OF THE BALLOON . . . 1 79
Cavendish and hydrogen — The ingenious Dr. Black — The Mont-
golfiers and smoke — Pilatre de Rozier, pioneer pilot.
CHAPTER XX
THE FOUNDING OF THE SCIENCE OF FLIGHT AND THE DEVELOP-
MENTS IN ENGLAND FROM 1809-1893 . . . 191
The toy helicopter — Sir George Caley's calculations — Henson and
Stringfellow's power-driven models — The Aeronautical Society of Great
Britain — Phillips and the dipping front edge — Maxim's great machine.
CHAPTER XXI
SOME PIONEERS ABROAD — THE INVENTION OF THE GLIDER . 203
In France : Penaud — Tatin — Mouillard — Ader — In America :
Langley — Montgomery — In Australia : Hargrave — In Germany :
Lilienihal— The coming of the glider — Pilcher — Chanute — Herring.
CHAPTER XXII
THE CONQUEST OF THE AIR . . . . . 215
Early work of the Wrights — The first long flight— Santos Dumont's
tail-first aeroplane — Henry Farman wins the first Grand Prix — The
American Army contract.
CHAPTER XXIII
THE FAMOUS YEAR . . . ... 223
The Writs in France — An hour in the air — Generosity and prizes —
The first pupils — The restart in England — Cody and Roe — The first
certificates — The first Aero Show.
CHAPTER XXIV
THE CHANNEL FLIGHT . . . ... 231
Latham's splendid failure — Bleriot's great success — The Royal Aero
Club's first aerodrome — The first British flight meeting — The end
of 1909.
CHAPTER XXV
LATTER-DAY PROGRESS . . . . 237
The London-Manchester flight — The second Channel flight — The
Bournemouth meeting — The deaths of C. S. Rolls and Cecil Grace —
The coming of the military flyer.
CONTENTS xi
PART IV
APPENDICES
PAGE
INTRODUCTION . . 247
TERMINOLOGY . .... 248
CLUBS AND INSTITUTIONS . , . . 251
BIBLIOGRAPHY . . . . ... 253
CHRONOLOGY . . . . . . . 257
WORLD'S RECORDS . , . ... 262
THE ROYAL FLYING CORPS . . . . . 264
MILITARY TRIALS, 1912: ABSTRACTS FROM THE OFFICIAL REPORT 272
WIND CHARTS . . . . ... 28l
ACCIDENTS . ; . . ... 283
PILOT'S NOTES . . . . 287
THE WRIGHT PATENT LITIGATION . . . 289
THE PETROL ENGINE . . . ... 292
THE HIGH-TENSION MAGNETO . . ... 297
THE ATLANTIC PASSAGE . . . . 301
NEWTON'S LAWS OF MOTION . . ... 303
PRESSURE AND RESISTANCE CONSTANTS . ... 304
DISTRIBUTION OF PRESSURE ON WING SECTIONS . . . 311
ANALYSIS OF FORCES ON WING SECTIONS . . . 314
THE TRAVEL OF THE C.P. ON WING SECTIONS . . .318
THE SYNTHESIS OF AEROPLANE RESISTANCE ,« . . 320
NOTE ON THE CENTRIFUGAL COUPLE . . . . 323
NUMERICAL EXAMPLES i . . . 325
TABLES AND DATA . . . 344
INDEX . . . . ... 356
LIST OF PLATES
SEEN AT CLOSE QUARTERS. A MONOPLANE IN FULL FLIGHT Frontispiece
FACING PAGE
SCENE AT THE HENDON AERODROME IN 1913 . . 2
STARTING UP • - . . . . . . 6
THE CODY BIPLANE ARRIVING AT THE HENDON AERODROME FROM
FARNBOROUGH . . . . • . . . 10
BANKING . . . . . . . 14
VIEW OF A HENRY FARMAN BIPLANE >
Two VIEWS OF A WRIGHT BIPLANE I
THE PILOT'S SEAT : AVRO AND BLERIOT MONOPLANES . . 22
THE BREGUET BIPLANE \
THE "B.E. 2" ALIGHTING ON PLOUGHED LAND . 26
THE DEPERDUSSIN MONOPLANE STARTING ON PLOUGHED LAND )
UNDERCARRIAGES . . . . . , . 28
Two HENRY FARMAN BIPLANES * . . . 38
THE PILOT'S SEAT : HENRY FARMAN BIPLANE AND BLERIOT MONO-
PLANES . . • . ... 42
HANRIOT, BLACKBURN, DUNNE, AND HANDLEY PAGE MONOPLANES 52
SYDNEY PICKLES BANKING ON A CAUDRON BIPLANE AT THE HENDON
AERODROME . . . .... 60
A BLBRIOT MONOPLANE ABOUT TO ALIGHT . . . . 68
GUSTAV HAMEL MAKING A SPIRAL GLIDE ON A BLERIOT
MONOPLANE
F. P. RAYNHAM BANKING ON A WRIGHT BIPLANE ,
PIERRE VERRIER ON A MAURICE FARMAN BIPLANE IN
LEVEL FLIGHT
TYPES OF ENGINES . . . . ... 84
TYPES OF ENGINES .... . . . 92
LlLIENTHAL ON ONE OF HIS GLIDERS . . . . 112
THE WRIGHT BIPLANE OF 1903 . . . . 128
xiii
xiv AVIATION
FACING PAGE
S. F. CODY ON THE BIPLANE WITH WHICH HE WON THE FIRST
PRIZE IN THE BRITISH MILITARY AEROPLANE TRIALS OF 1912 . 150
HENRY FARMAN'S HYDRO-BIPLANE ABOUT TO RISE AND ABOUT TO ^
ALIGHT - 154
A FLAT-BOTTOMED MOTOR-BOAT AT HIGH SPERD )
Fox BATS AND FLYING FISH . . . . . 182
A MONTGOLFIER AlR BALLOON OF 1783 . . . . l86
THE " AVION" AEROPLANE OF 1890. )
MAXIM'S AEROPLANE OF 1893 . . 204
S. P. LANGLEY'S TANDEM-TYPE MONOPLANE OF 1896 )
TYPES OF GLIDERS . . . . ... 212
PILCHER'S GLIDER "THE HAWK" }
SANTOS DUMONT'S TAIL-FIRST TYPE BIPLANE > ... 220
AN EARLY VOISIN BIPLANE
THE BRITISH-BUILT ROE TRIPLANE OF 1909 )
THE BRITISH-BUILT CODY BIPLANE OF 1909 . . 228
THE FRENCH-BUILT ANTOINETTE MONOPLANE OF 1909 }
SEVEN-CYLINDER AND FOURTEEN-CYLINDER GNOME ENGINES . . 236
THREE HYDRO-MONOPLANES . . 246
A DEPERDUSSIN MONOPLANE FITTED WITH DUAL CONTROL . . 250
LIST OF DIAGRAMS
PAGE
Sketches giving suitable dimensions for a simple paper glider . 10
Diagram illustrating a wing section in a series of different attitudes 15
The Martin- Handasyde monoplane at the 1913 Aero Show. The
Vickers monoplane at the 1913 Aero Show. The Bristol
monoplane at the 1913 Aero Show , . . . 18
The Short hydro-aeroplane at the 1913 Aero Show. The Avro
biplane at the 1913 Aero Show . . . 19
(A) Sketch illustrating the method of attaching the axle by rubber
cord to the skid of a Henry Farman biplane. (B) Sketch
illustrating the elastic suspension on the Bristol aeroplane. A
typical central skid undercarriage . . 27
The Bleriot undercarriage . . . 28
A double skid undercarriage . . ... 29
Pivoted lever control used on the Caudron aeroplane. Control
employed on the Wright biplane . . 32
Wrighi biplane with its planes warped '. . 33
Sketches of tails . . . . 35
Sketches of tail skids . . . ... 36
The flow in the wake of various strut sections . 91
The distribution of pressure over various wing sections . .103
The original designs for a hydroplane. Towed boat with a rounded
stern . - * . . . . . 155
Front float and tail float used on the Short hydro-aeroplane . 1 56
Main central float used on the " Waterhen '' . . . 157
The Goupy undercarriage, with floats for alighting on the water . 158
Types of floats used on the Borel and Nieuport hydro-aeroplanes 159
Cayley's helicopter, parachute, and aeroplane . . .192
Stringfellow's model monoplane and model triplane . 1 .198
Phillips's multiplane . . . ... 200
Elevation and plan of Sir Hiram Maxim's aeroplane . . . 201
Experimental kites . . . ... 205
A model built by Hargrave . . . . . 207
Wind charts . 281-2
xvi AVIATION
PAGE
5o-h.p. Gnome rotary engine . . ... 294
Diagrammatic drawing of a petrol engine . ... 296
Connections for a typical four-cylinder magneto . . . 299
Chart comparing the lifting efforts of three flat-bottomed wing
sections and a flat plate . . ... 306
Chart comparing the lift with the resistance of the wing sections
and flat plate referred to in the preceding diagram . . 307
Wing sections . . . . . . 312
Analysis of the forces on a cambered wing . . . .315
Vector diagram illustrating the tangential . . . .316
Charts illustrating the travel of the centre of pressure on two wing
sections and a flat plate . . . . 319
Diagrams showing the R.A.F. method of preparing estimates of
resistance and power required for experimental aeroplanes . 321
Graphic solution to a problem . . . . 332
Graphic solution to a problem . . ... 335
The centripetal forces that steer an aeroplane when it is banked . 336
Graphic solution to a problem . . ... 342
The trigonometrical ratios . . . . 351
AVIATION
PART I
INTRODUCTION
INTRODUCTION
THE CHARM OF FLYING
An early flight meeting in France — When aeroplanes become common-
place— The Great Unflown — The first time up — High speed in the air —
Sensations in the glide.
THE great charm of flying lies in the extraordinary
fascination of the problem of flight, which has in-
numerable aspects and every one of them interest-
ing. There are tricks to every trade, but where will you
find an occupation so replete with important issues as is
the field of aviation to-day ? It is not alone to the pilot
that this privilege belongs ; the engineer who builds the
aeroplane, and the student who studies the science, are
alike under the same great thrall.
It is the intensity of the interest that tells in flight. No
matter which way you turn, there is always some new point
to whet the intellect and to hold the mind absorbed. Every-
one feels it, once he knows how an aeroplane flies ; but
how few, relatively speaking, do know, when by knowing
is meant the full understanding of what you can see any
day that it pleases you to go to Hendon, or to Brooklands,
or to any other centre of aviation, where the aeroplane is
daily in the air ?
Curiosity was the impulse that formerly took the French-
men by their thousands to see those early efforts at Juvisy
on the outskirts of Paris ; but it is the interest born of
understanding that to-day holds still more thousands of
believers firm-rooted in their conviction as to the future
of flight.
How well I remember one of those Juvisy meetings ! It
xix
xx AVIATION
was a Sunday, and all Paris, with the better half of France,
was there already when my tardy train drew up at the
quiet little station beyond the environs of the metropolis.
In the roads and in the fields were motor-cars and vehicles
of every description, some abandoned, some still occupied by
irate sightseers who had no more chance of getting nearer to
the show than they had of flying. The time-worn metaphor
still applied, but how soon it was to lose its meaning.
Above the green that day men were already in flight.
Big Voisin biplanes loped heavily through the air, while
lighter monoplanes hopped a sprightly measure on the
grass. Fanfares from ceaseless trumpeters kept up a weird
music on the ear, and the dense crowd surged with the
restless motion of the sea, watching and cheering, running
to the palings and standing on chairs, and anon subsiding
for a moment to seek refreshment in a cup of coffee and a
sandwich, for which, if I remember rightly, the restaurateur
disdained to give change for five francs.
It was all truly wonderful ; but how glad I was that I
left early, and suffered myself to be carried by struggling
humanity into a compartment of the last train that re-
turned to Paris. Three hours we occupied on that journey,
but we did reach Paris, which was more than could be said
of those who tried to get home later in the evening. Some
people who left Paris by rail that afternoon never even
reached Juvisy ; for the story went that an over-excited
crowd, unable to find accommodation, amiably invaded
the line by way of passive resistance, to prevent outward-
bound trains from disgorging still more passengers whose
only thought then was how to get home again. Certain it
is, at any rate, that many people had the memory of their
first experience in aviation firmly implanted in their minds
by the unexpected necessity of spending a night under the
open sky.
To-day, flying has become more commonplace, but it
has not become less wonderful. When you see the modern
INTRODUCTION xxi
aeroplane start away so easily, and gradually disappear in
the distance without so much as a flutter from its straight
course, it seems almost uncanny that so much should have
been accomplished in such a short time, and with machines
that have, au fond, been so much alike all through. In a
few more years the general public will not even stop to
think that it does not really know how an aeroplane flies —
it will just take it for granted, as it takes its telephone and
its tube and its taxis.
But for the man and the woman who realize that a new
thing is worth knowing, and who take a serious interest in
the subject now that it is in its infancy, and, therefore,
seems more easily to be understood, there should be no
such apathy of mind. They will be keen to follow every
phase of the game, and the bare news of a short press
paragraph will unfold its own story without further words :
the milestones of aviation's history will have more than
the mere romance of triumph to make them interesting to
those who trouble to study the subject now.
To-day, the great unflown is divided into two camps.
There are those who say with keen anticipated ecstasy,
" I should love to go up " ; there are also those who pessi-
mistically pronounce, " Not I, at any price." But both can
take an interest in flight, and both can have a real appre-
ciation of the progress of the art. It is not necessary that
you should fly yourself in order to be really interested in
flying : that is the great advantage of a subject that pre-
sents so many aspects to the mental view. It might even
be that you would feel disappointed in your first experience
aloft — passengers often do, and in any case the first time up
is not calculated to give anyone a full perception of the
joy of riding the air.
Well do I remember my own first ride with Cody on his
great " Cathedral,"1 the man and his machine alike unique.
1 It is, I think, generally supposed that this nickname was due to the
comparatively large size of the Cody biplane. As a matter of fact, how-
b 2
xxii AVIATION
There was an iron seat behind the pilot, of the kind that
is used on threshing machines and agricultural instruments
of the vehicular kind generally. It was comfortable enough
to sit on, but when we got going over the roughnesses of
Laffan's Plain it was extraordinary how seldom the seat
would hit me in the right place. How Cody himself re-
mained secure with both hands on the control, when it was
all I could do to remain in the machine by clinging with
both hands on to the framework, exercised my mind even
then to the comparative exclusion of the one other thought
of how awkward it would be for both of us if I should
happen to fall out.
Once in the air, and how different it was ! — the extra-
ordinary smoothness of motion and yet withal the feeling
of firmness in this aerial support. I was engaged wholly
with my own sensations, and I think they still predominated
when Cody motioned me that I was to observe how re-
sponsive was his big machine, which he thereupon proceeded
to sway about in the air. On the whole, I must honestly
confess that the real sense of enjoyment came afterwards
on that occasion.
I thought then, and I have thought since, how like an
aeroplane is to the magic carpet of our childhood's days ;
only on some machines one does not perhaps altogether
relish sitting so very near the edge.
In flight, the sense of motion is not in the least what
you would expect from a prior knowledge of the speed
attained. It is the proximity of stationary objects that
gives one the impression of velocity. On an aeroplane, the
ground is so very far away and so very expansive that it
is almost an effort of will to keep the eye on an earth-bound
ever, it was due to a bon mot by F. W. Lanchester, the well-known
author of Aerial Flight. The principle of the upward dihedral angle
(wings sloping upwards from shoulder to tip) was under discussion,
and Cody was explaining how his planes, so far from displaying this
feature, were, in fact, slightly arched. " Ah, yes, I see," said Lanchester,
" you've got a kat(Gr. down)hedral."
INTRODUCTION xxiii
object for sufficient length of time to appreciate that one
is moving relatively to it at all. The speed through the
air is, of course, enormous, and directly behind the pro-
peller the relative wind is so terrific that it is difficult to
see without goggles. The very flesh of one's face seems to
drag at its foundations, it sags and quivers in this astound-
ing draught, which drives the very breath backwards down
your throat until you become accustomed to the art of
breathing under these strange conditions.
There is, indeed, often a curious feeling of standing up
against a solid wall of wind that is trying to blow you
backwards, but never have I experienced quite the same
sensation of rushing through the air that one gets on a
fast car, where the draught is merely an accessory to the
fundamental impression of speed resulting from the motion
over the road, which is always directly in the line of sight.
It is one of the phenomena peculiar to the process of
getting aloft in an aeroplane that the country, which lies
very naturally ahead when you start off on the preliminary
run over the ground, in some mysterious way seems sud-
denly to spread itself out beneath your view like a vast
carpet. The transition takes place almost mysteriously : you
are looking ahead, and then, without realizing that any-
thing definite has happened, you find yourself looking
down.
These impressions do not necessarily come to mind
during the first flight, but after a while you begin to notice
such details. Little peculiarities catch the attention : you
are struck, for example, with the dignified way in which
the machine seems to stride up into the higher levels step
by step, as the elevator is tilted and eased off under the
control of the pilot. Soon you get accustomed to noting
the lie of the land, to watching for the gusts in the hollows
and over the spinneys, where aerial disturbances are sure
to be found whenever the wind is blowing. Perhaps the
machine will sink a little, like a small boat in a lop, and
xxiv AVIATION
then climb out over the crest of some invisible wave, which
you feel is there, even though you cannot see it. Or there
may be an indescribable impression of flying through an
aerial shoal, especially when edging round into the wind
for the landing.
At the end of the flight comes the glide, most exhilarating
of all its episodes, when the aeroplane turns into a toboggan
and you slide down full tilt towards the ground. There is
nothing quite like it for the real joy of an unalloyed sensa-
tion. Mother Earth spreads her green quilt invitingly, and
you slither down an invisible stairway with the confident
abandon with which^ you fling yourself over the balusters
in a dream. How smoothly the wings cleave the air, how
gently the engine ticks round at its ease after its strong-
work aloft ! It is the dignity of repose in motion. Of the
same kind is the suppressed energy of a loco's rolling stride
as it enters the terminus, or the liner's majestic approach
up the fairway to the dock.
Of the same kind, yes ; but how different in detail !
Where is the pompous boiler bursting with steam, where
is the irresistible mass of the gigantic hull, in the fairy-like
grace of a monoplane descending to earth ? And the little
finale : can you not see the flutter of the bird's
wing as it steadies its flight to alight on the bough, in the
br-r-r of the motor as the pilot switches on at the last
moment and cocks up the tail flap to flatten out ere touch-
ing the ground ? It is the consummation, this smooth
flattening out, of that delightful impression of softness that
is presented by the typical green field towards which you
have rushed downwards through space, like a god descend-
ing from some higher plane. In cold blood you know the
impression is false, for even the football ground, on which
you first gained an early preference for falling on grass,
must have disillusioned you from the first on that score.
Besides, it is only necessary to see one aeroplane smash,
where half a ton of timber and steel has tried conclusions
INTRODUCTION xxv
with the earth's surface, to realize how terribly hard is the
hand lying hid in that velvet glove.
But if you let such thoughts as these deter you, you
would be chained to your bed for life, and then live in fear
of fire and earthquake. You would never cross the street,
never travel in tubes and motors, never go abroad in
mammoth liners, and, in fact, never do any of the hundred
and one things that occupy your normal existence and are
cheerfully accepted as part and parcel of life because you
have confidence that, being adopted of the people, they
are above reproach.
The ever-regrettable loss of the Titanic tore the heart-
strings of humanity because of the sorrow that came in its
wake, but just as severe in its way was the public's painful
surprise when it realized that such a thing could be. Modern
civilization has so enfenced our daily existence with pro-
tective legislation that the first principle of public service
is not only that it shall be safe, but that it shall also be
fool-proof. According to our idea of things to-day, it
should not be possible for a man to come to grief through
his own carelessness in misusing conveniences that are pro-
vided by the civilization of which he forms part.
Men rail against the insistency of progress, but their
resistance is of no more avail than would be the holding of
the hands of the clock in an attempt to place a check upon
time. Progress and time are, in fact, synonymous : time is,
and progress continues. Neither the one nor the other can
rest, yet the master of both is for ever at peace with him-
self and the world, and he alone is happy. A novelty
offends you — study it. Think well upon it, and consider
whether or no it is a link in the great chain, or whether
merely an appanage that comes to-day and to-morrow is
gone — a bit of seaweed held up against some ship's side by
the tide. Is the aeroplane but a passing fad, do you think,
when men have searched through the ages for the solution
to flight ? Whoever says so has never seen a flight with
xxvi AVIATION
the full understanding of his mind, has never grasped what
it means to pass over hill and dale, to cross river and road,
to stride forests and lakes as if they were not.
How terribly cold these things seem in print ! But see
them happen with your own eyes, and you will understand.
Condescend for a moment to stand as a simple child before
the wonders that man has worked with Nature's laws.
Forget the telephone and the tube and electricity and all
the things you know so well, but understand so little, and
just think of the physical fact of flight. A man and a
machine, solid material both of them, go up into the air
without visible means of support and fly for miles. Is it
less wonderful than the Indian juggler who climbs the
mysterious rope, and vanishes ? It is more interesting, any-
way, for we do know something of how it is done, and
although the knowledge is small it adds immensely to the
value of the performance.
The study of aviation is a real science, and the business
of aeroplane construction is sound engineering : both are
worthy of the professional interest of men who have already
laid the necessary foundation of technical knowledge. The
former, the scientific side, has perhaps the wider scope of
influence, for it might well be numbered among the pages
made interesting by Sir Edwin Ray Lankester in his Science
from an Easy Chair. Aviation is, in fact, an excellent introduc-
tion to science, because of the breadth and of the intensity
of its interest to those who have never professed to be
scientific. It puts science in a pleasing light, for, starting
in mystery, it ends in simplicity, and yet leaves the student
respect for the wonderful.
More important, in many ways, than any reason yet
mentioned for being interested in flight is its national
significance. The aeroplane and the airship have become
armaments of first-class importance, and have been de-
veloped as such by France and Germany to an extent that
has placed those countries in possession of large aerial
INTRODUCTION xxvii
fleets. British policy has, unfortunately, been to await
the march of events elsewhere, and, in consequence, our
aerial force is woefully small. Lacking the spontaneous
enthusiasm so characteristic of nations farther south, people
in England have been comparatively apathetic towards a
movement that they do not understand and which makes,
to the majority of them, no personal appeal. Living on an
island as we do, however, superiority in the air is as neces-
sary to our safe defence as is the command of the sea, and
for that reason alone every thinking Englishman should so
far study the subject of flight as to arouse in himself an
interest sufficient to ensure his support of the principle of
British aerial supremacy.
AVIATION
PART I
CHAPTER I
WHAT AN AEROPLANE IS
Getting under way — What the wings do in flight — Relative motion —
A railway carriage experiment — The effect of the angle — Why aeroplanes
are like yachts — How birds soar — Why power is necessary to flight —
Nature flaps a wing — Man revolves a propeller — What happens when
the engine stops— Gliding on an aerial toboggan — Kites flying in the
wind — Pros and cons of the cambered wing — Natural stability — The
need for a tail — Advantages of flying high.
EVERYONE, nowadays, is familiar with the appear-
ance of an aeroplane, but many there are, never-
theless, who do not know what, scientifically
speaking, an aeroplane is. They see the machine on the
ground : they observe someone giving frantic tugs at
something that moves in jerks ; they hear a roar, which
they know must come from an engine, although why it
makes such a noise they doubtless fail to understand ; they
perceive that, in starting, the machine runs for a while
along the ground before rising gently, as if lifted by some
invisible moving stairway, into the air ; but, still, they do
not know why the aeroplane flies.
It has something to do with the wings, of course, but
how ? That is the question at which the average lay mind
stops short, not for lack of ability to understand the prob-
lem, but, generally, for lack of some appropriate explana-
tion that will bring what is, fundamentally, a very simple
phenomenon out of its proper sphere of aeronautical science
into the realm of everyday things that are comprehended
by common sense.
2 AVIATION
There is an elusive aspect of the general view, and only
one, that is apt to hide itself from the uninitiated unless
brought prominently into the full light of the mind in the
very first instance, and that is the significance of a simple
scientific expression much used in aviation, namely, " rela-
tive motion."
If the man in the street saw an aeroplane apparently
standing still in the air, it would not occur to him to think
that the machine must be flying through the wind at its
full speed, and that its relative motion in the air is quite
unaffected by its motion relatively to the ground on which
he is standing. Yet the same man knows very well that
if he starts running on a calm day he will feel a slight breeze
in his face, which is solely the result of his own relative
motion through the air. He is also aware that if he puts his
head out of an express railway train he will encounter half
a gale of wind, notwithstanding that the leaves of the trees
may show not so much as a tremor.
If, instead of putting his head out of the window, he
were to take a sheet of stiff cardboard and put that out-
side, he would have a still more practical demonstration of
the force of the relative wind, which supports the aeroplane
in its flight.
The first sheet, having been put out at random, will,
probably, be broken even if it is not wrenched out of his
hands. This will set his mind reasoning that he must be
careful to hold the cardboard edge-on if he wishes it to re-
main outside in safety. A second attempt, on these lines,
will give rise to still more astonishing results. If the train
is moving really fast, the cardboard will exhibit a violent
tendency to flap upwards or downwards with the least
variation from its truly edge-on horizontal position.
It is at this point that the embryo scientist begins to
think really hard. His mind perceives an unsuspected fact
that he senses to be of great importance. He has observed
that by slightly raising the front edge of the piece of card-
board so that it (the cardboard) is at a slight angle to its
line of motion, instead of being truly edge-on, an extremely
strong lifting force acts on the cardboard, although its
" Flight " Copyright Photo
SCENE AT THE HENDON AERODROME IN IQI2
A Bleriot monoplane descending and a Farman type biplane ascending. The bip'ar.e is
flying away from the camera and the monoplane is approaching from above.
WHAT AN AEROPLANE IS 3
resistance to motion through ihe air is but little more than
it was when the cardboard was edge-on.
So pronounced is the preponderating value of the lifting
effort over the resistance at very small angles, that anyone
making this experiment would at once conclude that if he
wished the wind to support a weight he would certainly
arrange some sort of surface beneath it, like a table, but
tilted so as to have only a slight angle of inclination to the
line of its flight through the air.
It is improbable that our railway carriage scientist would
get further than this of his own accord, and particularly so
under the limitations of his environment, but he has
served his purpose in introducing us to an important
principle in a way that lends itself to repetition by the
curious. The speed of a fast railway train has the merit
of demonstrating the various phases of the phenomenon
on a realistic scale, and if the restrictions of space reflect
themselves in the diminutive dimensions of the object
that it is convenient to handle in this way, there should,
nevertheless, be no excuse for the experiment failing to
engender a firm-rooted appreciation and respect for the
nature of the lift that a relative wind will exert on the
surface of a properly arranged aeroplane.
The inclined flat plate exerts a lifting force1 because
it deflects downwards a stratum of air in its flight. If it
deflected the air upwards, the reaction on the plate instead
of being a lifting force would be downwards. When the
plate is set upright, facing the wind, the deflection takes
place in every direction as the wind swirls round it, and
the reaction is neither upwards nor downwards, but just
a straightforward pressure, acting in the line of the wind.
In any event, it will be noticed, the force is always per-
pendicular to the face of the plate. When the plate is
slightly inclined it is a lifting force, when the plate is up-
right it is a resistance. When the plate is edge-on, the
resistance is mostly due to the friction of the air against
the surface of the plate.
An aeroplane has its table-like supporting surfaces so
1 See Appendix on Newton's Laws of Motion.
4 AVIATION
arranged as to get the best lifting effect for the least effort,
having regard, of course, to the conditions under which
the machine is designed to fly. It is clear, merely from a
glance at a number of different aeroplanes, that they are
not all exactly alike in this respect, but it will be noticed
that they all have one point in common, which is that the
surface, instead of being flat, is cambered or slightly bellied
like a sail of a yacht.
This is an important analogy, because a yacht is one of
those commonplace objects that are so familiar that the
man on the quay never stops to ask himself whether or
no he understands how it sails. It will be the same with the
aeroplane in a few years' time, which is why it is worth
while troubling to appreciate an explanation now, in order
that one really may be informed as to the essential facts
by the time aviation, in common with so many other
interesting things, becomes veiled under the ever-spread-
ing pall of public indifference.
A yacht is propelled by the wind into which it sails,
but an aeroplane is pushed forward by its propeller, which,
like the screw of a motor-boat, is driven by an engine. A
real wind needs must blow for the yacht to move ; more-
over, the wind must blow obliquely against the sail, not-
withstanding that a good boat, well handled, can sail within
a few points of the very eye of the wind.
The sail of a yacht is an aeroplane in principle, but its
use differs materially from the purpose of the wing of
an aeroplane. When the wind blows obliquely on the sail
of a yacht, the pressure that it exerts is mostly directed
towards capsizing the boat, but owing to the set and
camber of the sail the force is also directed slightly for-
ward towards the bows, and the amount of this component
is sufficient to propel the boat.
If a real wind were to blow obliquely from beneath on to
the sail of an aeroplane, the same propelling effect would be
produced, and the main force that tends to capsize the yacht
would be turned to the useful purpose of support ing the weight
of the machine, which would continue to fly without using
its engine so long as the conditions remained appropriate.
WHAT AN AEROPLANE IS 5
The phenomenon of flight without any development of
power in the object that is flying is a common occurrence
among many kinds of birds, which may be observed to
" soar " above cliffs, promontories and other physical
obstructions to the horizontal motion of the wind, which
tend to give to the wind an obliquely upward course.
In a steady horizontal wind, soaring flight is impossible ;
likewise is it impossible in a dead calm — the support of
which statement by Lord Rayleigh notwithstanding —
there are often to be seen in print suppositions that imply
the contrary.
Soaring is an art that has been but little practised by
man. The late Wilbur Wright and his brother Orville
have been almost the only exponents up to the present time.
It may be regarded in the nature of superflying, when
practised with machines as now built, for although the
evidence afforded by soaring birds opens up a fascinating
realm of thought, there are many considerations that,
for the time being, keep this kind of flying outside
the boundary of immediate practical possibility. The
object of discussing it here is to emphasize the sig-
nificance of the relative wind in flight ; to show that,
under suitable circumstances, a real wind will maintain
flight, and to argue therefrom that the purpose of the
engine on an aeroplane is primarily to maintain a state
of relative motion between the machine and the air, so
that practical flying can take place in a calm or any other
sort of weather.
At this point let us become thoroughly familiar with the
idea of power in connection with flying. What has been
said above about soaring may have given the notion that
flight was possible without any manifestation of energy,
but nothing is further from the truth. When the wind
blows it often possesses enormous power, and when it
blows suitably against a windmill, or the sail of a yacht,
or the wing of a bird, it may transfer some of its energy
into mechanical movement as grinding, sailing, and flying
respectively in the three instances cited.
When the air itself does not move, or does not move in
6 AVIATION
a suitable way to enable the transformation of its energy
into soaring flight, the power necessary to the continuance
of flying must be supplied by the object that flies. The
bird flaps its wings, the aeroplane starts its engine. Or-
dinarily, a head wind is merely an added resistance to flight ;
only from winds that blow upwards or pulsate in a certain
manner is it even theoretically possible to extract power for
soaring flight.
To the uninitiated there may be little resemblance
between the action of a bird's wing and that of the pro-
peller which is driven by the engine of an aeroplane.
Scientifically, there is a close analogy between them. Nature
builds on a plan and with materials that man cannot
slavishly copy. One of her masterpieces is the perfect
articulation of the joints of an anatomy that permits of
such a smooth-acting to-and-fro movement as is mani-
fested by the legs of an animal when walking and of a bird's
wing when in flapping flight. The material of the moving
members has to be nourished by arteries that must pass
across the joint and so nature is limited to this sort of
action.
Reciprocating motion is anathema to engineering, but
the engineer finds a great compensation in the principle
of rotation, and wherever it is possible to do so the mechan-
ism of mechanical power is confined to the continuously
revolving shaft. Thus, on an aeroplane, you find an engine,
which generates the power, a revolving shaft, which trans-
mits the power, and a propeller on the shaft, which trans-
forms the power into thrust and so pushes the machine as
a whole through the air. Generally, the presence of a shaft
is not visible externally, because the propeller is attached
close up to the engine ; often, too, the engine itself revolves
with the propeller, but these are details that it would be a
digression further to discuss in the present place.
Power is essential to flight truly, but when the engine
stops in mid-air, the aeroplane does not fall to the ground,
nor is the pilot in any need of a balloon, or of a parachute,
or of any other life-saving apparatus in order to reach the
earth safely. The popular idea that some such precaution
WHAT AN AEROPLANE IS 7
as this would be a safeguard against accidents, does but
proclaim its own ignorance of the basic principles of flight,
for the aeroplane itself, when properly designed and flown,
possesses an inherent quality that is far better than any
artifice, and without which, indeed, flying by aeroplane
would be quite out of the question.
A machine tha^is already in mid-air can always con-
tinue to fly for a considerable distance, even if the engine
does stop accidentally, provided that the direction of the
flight is obliquely towards the ground. Roughly speaking,
a modern aeroplane can glide in this manner for a distance
equal to six times its height above the ground : for example,
if it is at one thousand feet up in the air when the engine
stops, the pilot has his choice of landing more or less any-
where within a radius of a mile. He must, of course, im-
mediately make up his mind, from the lie of the land and the
direction of the wind, which spot within sight should best
serve as a landing-ground. The downward path begins
directly the engine stops and there is no means of checking
the descent for a fresh observation.
The speed of gliding is somewhat slower than the normal
fast-flying speed; otherwise, the conditions of gliding are
the same as flying and the machine is equally under control.
A slope of I in 6 is not steep and, except that a landing is
essential and that the pilot has no alternative than to make
the best of a bad ground, if he finds, at the last moment, that
he is mistaken in his choice, the danger of alighting under
necessity is no greater than that of returning to earth in
the ordinary way. A normal descent is in any case accom-
plished by a glide, but the engine is ordinarily kept slowly
rotating so as to be in readiness for instant action if needed.
Let us now make a brief resume of the foregoing points,
which have followed perhaps some slight inconsequence in
their order of presentation. In the first place, there is the
readily demonstrated fact that a suitably arranged surface
in the form of a flat plate, which technically is commonly
called a plane, will support a considerable weight when
slightly tilted to the wind. Secondly, there is the funda-
mental theory, which is equally easily proved to be fact,
8 AVIATION
that this phenomenon depends only on relative motion
between the plane and the air and does not demand that
a wind should blow that can be felt by anyone standing
on the ground. It makes no difference whether the air
blows under a stationary plane, as in the case of a kite
flying in the wind, or whether an aeroplane flies through a
calm atmosphere, the supporting effect of the aerodynamic
reaction between the plane and the air, which is set up by
their relative motion, is identical in principle and similar
in degree for both cases so long as the same relative velo-
cities prevail and other things are equal.
Further, we have established the very important prin-
ciple that power is as essential to flight as to any other
form of motion, and that, under suitable conditions, which,
as yet, do not prevail for modern aeroplanes, the energy
of the wind is available for this purpose. Continuous
flying by the aid of the wind alone is called soaring. In the
absence of a suitable wind and proper means for utilizing its
energy, an engine is, therefore, essential to the mainten-
ance of mechanical flight and all aeroplanes are fitted with
them.
It has been explained, however, that should the engine
fail in mid-air, the aeroplane can still continue to fly for a
considerable, although strictly limited, distance, by gliding
towards the earth, and that in its inherent ability to
play the aerial toboggan lies the natural safety of this
form of machine.
Arising out of the discussion on soaring, or flight by the
aid of the wind, an analogy was drawn between the action of
the sail of a yacht and that of the wing of an aeroplane, an
important detail being indicated in the cambering of the
surfaces. It is significant, too, that birds' wings are in-
variably cambered, which fact was observed and com-
mented upon, as a feature that ought to characterize the
design of aeroplane wings, by Sir George Cayley as long
ago as 1809.
Of the various qualities that make a cambered wing
superior to a flat plate more will be said later ; here it
needs only to be pointed out that it will support more
WHAT AN AEROPLANE IS 9
weight and be the cause of less resistance to motion at any
given speed. Thus, it enables the engine to perform a
greater amount of useful work in a given time for the same
expenditure of power, either by carrying a heavier load, or
by transporting the machine at a higher rate of travel
through the air. It does not follow that there [is any
especial virtue in an excessive amount of camber : the con-
trary may, in fact, be the case. The amount of camber
and other peculiarities of wing-form are technical questions,
the discussion of which must be deferred, as they cannot
readily be dealt with in general terms. There is, however,
one aspect of the principle of cambering that it may be
interesting to consider forthwith and that is its influence
on " natural stability."
CHAPTER II
THE INSTRUCTIVENESS OF PAPER MODELS
Natural stability in a simple form — Flat v. cambered wings— Why
aeroplanes are broader than they are long — The " T " test — Why. an
arrow flies straight — The Centre of Pressure and the Centre of Gravity —
The purpose of the tail.
N" ATURAL stability is a much-abused term, being
far too commonly employed without a qualifying
explanation, and having in itself no very definite
meaning. It is, however, a fact, easily demonstrated by
simple models, that certain forms of surface exhibit in flight
an inherent tendency to recover their equilibrium if dis-
turbed, whereas others exaggerate their initial loss of balance
to a point at which they capsize.
Centre o£
Gravity N. Lead Foil
" Flight " Copyright Sketches
Sketches giving suitable dimensions for a simple paper glider, and showing1 how
to launch it. Plasticine may be used instead of lead foil for the weight. A post-
card cut to shape will serve to stiffen the paper as shown.
Thus a perfectly flat plate, such as, for example, may
be made from a half-sheet of stiff note-paper cut in two
lengthways, will demonstrate a high degree of natural
stability if loaded with a small weight like a split shot in the
10
•
INSTRUCTIVENESS OF PAPER MODELS 11
very centre of its front edge, and launched broadside-on into
the air. By taking a little care in adjusting the weight and
choosing the paper, it may be made to glide in a surprisingly
steady manner across the full length of a room, and even
when dropped vertically will recover itself and glide off in
an almost horizontal direction, provided that there is suf-
ficient room for it to make the initial fall before touching
the ground.
This matter of the necessity for sufficient height in which
to fall, has, by the way, a very practical and a very serious
aspect in real flying, where altitudes in the order of 1000 feet
have long been recognized as realms of comparative safety
for this very reason. During its vertical descent the paper
model gains the velocity required to establish the relative
motion between itself and the air, which alone will support
it in flight. When a real aeroplane has for any reason lost
headway in mid-air, the pilot's only safe course is imme-
diately to point the nose of the machine earthwards, and to
dive downwards until he recovers his proper flight-speed.
Much more can be learned from the use of paper models
than can be described here, but it is not without interest to
refer to another simple experiment that teaches a useful
lesson. Having observed the natural stability of the loaded
flat plate, it is instructive to see the inherent instability of
the same surface when it is cambered. The cambering may
be accomplished, for example, by stretching a silk thread
between the leading and the trailing edges, so that the
paper is bent like a bow.
Launch this modified design with what care you may, it
will inevitably capsize before it has gone far, and in this
simple yet very convincing manner will bring you face to
face with a most interesting phenomenon, which, technically,
is referred to as the travel of the " centre of pressure."
More will have to be said about this matter when we have
progressed further into our subject.
It is difficult to overrate the advantage of studying the
fundamental principles of aviation by the aid of elementary
models such as may so easily be made from the simplest sort
of material. Half a sheet of stiff note-paper, casually
12 AVIATION
dropped from the hand, pursues a zigzag course that is in-
structive. No movement takes place without some guiding
force at the back of it, and the persistent repetition of a
recognizable action is a sure sign of some governing principle
being at work, even when the performance as a whole is
apparently so erratic as is the fluttering of a piece of paper
while it is falling to the ground.
Cut the same piece of paper into the form of the letter
T, and then repeat the experiment by dropping it head
first, and again tail first. If the model has been made from
suitable paper, it will always reverse in the air when it is
dropped head first, and will come to earth stem first. At
first sight, the significance of this result may not be apparent;
actually, however, it affords a very simple and very direct
proof of the advantage of flying aeroplanes broadside-on
instead of end-on.
The end-on aspect, or that position in which the plane
flies with one of its narrow edges leading, would probably
suggest itself to most people as the common-sense way of
arranging the planes on a machine instead of placing them,
as they are at present, broadside-on to the line of flight.
Undoubtedly, the end-on aspect would be a more convenient
position in many respects, but unfortunately it is by no
means so useful in flight. In this connection it is interesting
to observe that the wings of birds always have a greater
dimension in span than they have in the line of flight.
The difference in effect between these two methods of
arranging a similar surface is clearly demonstrated by the
result of the above-described T test, which was, I believe,
first devised for this purpose by Mr. F. W. Lanchester. If
the T piece be so cut that the stem and the cross-bar are of
equal size, then we have two similar planes flying under
identical conditions, except that one is broadside-on and
the other end-on to the line of flight. Were they equally
effective, there would be no reason for the phenomenon
that accompanies the experiment. The fact that the cross-
piece of the T which is flying broadside-on invariably lifts
itself into the uppermost position when dropped head first,
shows that the pressure upon it is greater than is manifested
INSTRUCTIVENESS OF PAPER MODELS 13
on the stem of the T, which is of the same area, but is
flying end-on. Clearly, therefore, the most effective way of
using a given amount of surface for the purpose of supporting
a weight, is to arrange it so that it flies broadside-on, and it
is for this reason that the wings of aeroplanes fly in this
aspect.
Another illustration of the same principle is afforded by
the flight of an arrow. Without feathers, an arrow-shaft
would have no stability of direction, and would in many
cases finish its journey through the air tail first. The feathers
themselves are in end-on aspect, but regarding a pair of them
in respect to the very narrow shaft, they constitute a tiny
aeroplane flying broadside-on like the cross-bar of the T.
The air pressure upon them is always greater than the pres-
sure upon the shaft, consequently any disturbing influence
on the shaft, tending to swerve it from its course, is counter-
acted by a superior force on the feathers, which maintains
the direction of motion unchanged. For the same reason,
the steering of dirigibles on a straight course is much facili-
tated by the presence of fin surfaces well aft.
It may be desirable to explain in respect to these tests
with paper models that even an apparent calm is full of
disturbances, which prevent light objects, such as a sheet
of paper, from pursuing a truly edge-on motion for any
considerable distance. You may drop a flat sheet of stiff
paper, edge-on, with great precision, but it will certainly be
disturbed before it has fallen more than a foot or two.
Directly the paper ceases to follow a perfectly edge-on
course, it assumes an inclination to its line of motion, and
becomes an aeroplane in full flight.
There is a very important phenomenon associated with
the air pressure on an inclined plate, to which it may be as
well to direct attention at once. This is that the centre of
pressure, or spot where the lifting force of the air seems to
be concentrated, lies close to the front edge of the plate
when the angle of inclination to the line of flight is very
small. When, for any reason, the plate becomes more
tilted, so that its angle of inclination to the line of flight is
coarse instead of fine, then the centre of pressure travels
14 AVIATION
backwards towards the centre of the plate. If the plate were
held vertically upright facing its relative wind, the centre of
pressure would coincide with the centre of figure.
If the location of the centre of 'pressure (often written
C.P. for short) is near the leading edge of a plate that is
falling edge-on vertically through the air, it is evident that
the lifting force will tend to turn the plate into a horizontal
position. This is precisely what happens when the sheet of
note-paper makes its first flutter into its zigzag path. The
energy of its motion acquired during the fall expends itself
on a brief horizontal flight, during which the plate loses
headway, and ultimately falls backwards. The repetition
of these phenomena in definite sequence is the simplest
explanation of an apparently erratic performance.
If the plate carries a little weight on its front edge, such
as a pellet of buck-shot, a piece of plasticine, or even an
ordinary pin if the model is very small, a coincidence may
be established between the centre of pressure and the centre
of gravity (the point where the weight seems to be con-
centrated) so that the levelling of the plate towards a
horizontal position is checked at a critical angle. Under
these conditions the plane will proceed to glide in a beauti-
fully smooth manner, and will, in fact, have become an
elementary aeroplane under the automatic control of its
own inherent stability. The success of the experiment
depends on the selection of a weight proper to the size of
the plate, and demands considerable care and patience.
The nature of the inherent stability of the loaded flat
plane is now easy to see, for it evidently depends on the
variable leverage that is exercised about the fixed centre
of gravity by the movable centre of pressure as it travels to
and fro under the influence of the changing angle or attitude
of the plane in flight.
It has been explained how a change in the angle is
initially due to some slight disturbance in the air, and how,
at very small angles, the centre of pressure is quite near the
leading edge of the plane. At first ^therefore, the centre of
pressure will be in front of the centre of gravity, which never
changes its position, but as the front edge of the plane is
" Flight " Copyright Photos
BANKING
The top photograph shows Chevillard executing a banked turn with the Henry Farr
jiplane over the Brooklands Aerodrome, 1913. The lower photograph is of Verrier on
Maurice Farman turning at a comparatively low altitude. The foreground in the lo
biplane over the Brooklands Aerodrome, 1913. The lower photograph is of Verrier on the
Maurice Farman turning at a comparatively low altitude. The foreground in the lower
view gives an accurate horizon from which to judge the angle of the machine, but the upper
photograph was also taken by the same staff photographer of Flight, and the attitude
is in no way an exaggeration of the position that Chevillard frequently assumed.
INSTRUCTIVENESS OF PAPER MODELS 15
tilted upwards, the centre of pressure will travel backwards
until it coincides with the centre of gravity, and so tem-
porarily establishes a condition of equilibrium. This state,
however, is only momentary, for as the plane has already
commenced to swing upwards, it is certain to swing beyond
the neutral position of balance, and so the centre of pressure
will be caused to travel still further towards the rear, until
the upward swing of the front edge has stopped.
" Flight " Copyright Drawing
Diagram illustrating- a wing" section in a series of different
attitudes, showing-, by the position of the arrow, the retro-
gression of the centre of pressure as the angle of incidence
becomes finer.
The centre of pressure is now well behind the centre of
gravity, and the plane has lost headway, so that it tends
once more to fall headlong in order to regain its velocity.
This process is repeated as an undulating motion during
the first portion of the flight of the model, but by degrees
the undulations damp themselves out, and the attitude of
the plane remains steadily in one position, slight disturb-
ances being immediately counteracted by slight move-
ments of the centre of pressure as above described.
16 AVIATION
When this experiment is tried with a cambered plane
of single curvature it results in failure every time, because
the centre of pressure plays a trick that totally destroys
its former good effect. Within the range of angles
commonly used in flight, the centre of pressure travels
backwards as the angle of incidence decreases. This is dia-
metrically opposite to the phenomenon that occurs with
a flat plate, consequently any disturbance of a cambered
wing in flight is accompanied by a movement of the centre
of pressure that itself augments the disturbance. Instead
of being like the flat plate, inherently stable, the cambered
wing is inherently unstable, for an augmented disturbance
must ultimately culminate in capsizing the model.
The above applies to all wings at present used on aero-
planes ; it does not follow that it is impossible to find a
wing section without this characteristic. More, however,
is said upon this subject in another chapter. For the
moment it is all-important to recognize the prevailing
principle, and to realize that there is only one way in which
to correct this unfortunate tendency, and that is to provide
the cambered plane with a tail, or with the equivalent of a
tail, and this brings us to the consideration of the principal
parts of a real aeroplane, which is the subject-matter down
for discussion in the next chapter.
CHAPTER III
SOME CONSTRUCTIONAL FEATURES OF THE
MODERN AEROPLANE
Aeroplanes compared with birds — Monoplanes and biplanes — Diffi-
culties about length — Span, chord, and gap — Why the centre of pressure
does not stay still — When flight was impossible — What Sir George Cayley
knew — How an aeroplane is steered — What the elevator is for —
Characteristic features of design.
E[E birds, aeroplanes possess bodies, wings, and
tails ; they also have undercarriages that serve
the purpose of legs when alighting. The class of
machine that most closely approximates to the bird type
is the typical monoplane of the present day ; biplanes
often having no resemblance whatever, in appearance, to
Nature's best flyers.
The technical difference between a monoplane and a
biplane, however, is merely that a monoplane, in common
with the bird, possesses only one pair of wings, while the
biplane is provided with two main supporting surfaces,
one situated above the other.
The main supporting surfaces of a machine, which in a
monoplane are commonly called wings and in a biplane are
more usually called planes, are always readily identified
because they are by far the largest and most prominent
objects visible to the eye at a casual glance. This is not
surprising when one realizes that the span or measurement
of the wings from tip to tip is seldom less than 30 ft., while
some measure over 60 ft. across.
There is apt to be considerable confusion about the use
of the term "length " when applied to aeroplanes, owing to
the already mentioned fact that the wings fly through the
air broadside-on. It is natural, when speaking of the
2 17
18
AVIATION
wings alone, to refer to their longest dimension as their
length, as one would do when speaking of any other object ;
but, when the machine is in flight, one might equally well
remark how short is the length of the wings compared with
that of the machine as a whole, meaning thereby the
The Martin-Handasyde monoplane at the 1913 Aero Show.
The Vickers monoplane at the 1913 Aero Show.
' ' Flight " Copyright Sketches
The Bristol monoplane at the 1913 Aero Show.
measurement of the wing from its leading edge to its trailing
edge. For this reason, it has become customary to apply the
terms " span " and " chord " in this connection, and having
an obvious derivation they justify their existence as tech-
nical words and are deserving of general use. One speaks
of the span of a bridge and of the chord of the arc of a circle :
SOME CONSTRUCTIONAL FEATURES 19
both expressions have an analogous significance in refer-
ence to the aeroplane.
Thus, the wings, which are the supporting members of
the machine, form a kind of bridge that spans the air in
order to hold aloft the weight ; the wings themselves, as
has already been mentioned, are cambered so that a string
stretched between the leading edge and the trailing edge
would occupy the position of the chord to the arc that is
formed by the wing surface. This arc, by the way, is not
circular, but is of such contour as is found best by ex-
The Short hydro-aeroplane at the 1913 Aero Show.
" Flight ' Copyright Sketches
The Avro biplane at the 1913 Aero Show.
periment on models that are tested in an artificial wind.
The highest point of the curvature of any wing section is
always nearer the front edge than it is to the trailing edge
of the wing.
It has been pointed out that the cambered wing was
recognized as a possibly better form of supporting surface
than a flat plate by Sir George Cayley more than a hundred
years ago, and his conception of other proper features for
an aeroplane was singularly prophetic of the modern
machine. He included as two of its most important ac-
cessory features an elevator and a rudder. Cayley, having
20 AVIATION
satisfied himself that an aeroplane was a reasonable con-
ception, imagined it in a reasonable and simple form. He
argued that since it would sail in instead of on the aerial
ocean, it must be equipped with two sorts of rudder, one
for steering to the right and to the left in the ordinary way
and another for steering up or down. This latter we now
call an elevator in order to avoid confusion of terms ; actually
it is merely a pivoted plane just like a rudder, but arranged
horizontally instead of vertically.
In a monoplane, the rudder and the elevator form part of
the tail of the machine. The term " tail " applies to a group
of organs of which the two just mentioned are hinged and
movable to perform directional functions under the pilot's
control. A third plane, horizontally arranged like the
elevator, but rigidly fixed, is commonly added in order to
confer some degree of natural " longitudinal stability " in
flight.
In those aeroplanes that have long boat-like bodies
extending the full length of the machine, this fixed tail
plane is often a mere fin-like excrescence. On other types,
however, the rigid portion of the tail is a much larger
affair ; in either case, it commonly carries the elevator as
an extension in the form of a hinged flap. The purpose of
the fixed tail-piece has already been indicated ; it will be
remembered that, when discussing the natural instability
of the cambered plane, mention was made of the fact that
the missing quality could be incorporated by equipping
the plane with a suitably arranged tail member.
One principle involved in a suitable arrangement is
that the effective angle of the fixed tail must be less than
the effective angle of the main wing. This is to say that
if the two were extended they would make an angle with
one another ; the angle is so slight, however, as to be
invisible to the eye, but the principle is there and it is
commonly referred to as the fore-and-aft " dihedral."
Its object is, as has been mentioned, to confer stability
in flight, but for the further discussion of this aspect of the
subject it will be desirable to refer to another chapter.
As this book is written to be as far as possible an in-
"Flight" Copyright Photo
View of the Henry Farman biplane showing the balancing flaps on the upper plane. The upper
plane has a much greater span than the lower plane. The particular machine illustrated was one
much flown by Grahame-White during 1912.
"Flight" Copyright Photos
Two views of a Wright biplane, built originally by Burgess in America, but reconstructed later
by Sopwiih at the Brooklands Aerodrome.
SOME CONSTRUCTIONAL FEATURES 21
troduction to the subject, it has been necessary to assume
that the reader is unaware of the purpose of many out-
standing characteristics of modern aeroplanes, which must,
nevertheless, in fact, be familiar by sight. At this stage of
the description it would be as well, therefore, if some par-
ticular attention were paid to the illustrations. They have
been chosen especially for the purpose of making clear the
more important distinctions between machines and also
to show some of the chief phases of flight to which refer-
ence is made in other chapters.
The presence of the two main planes as the distinguishing
feature of biplanes is apparent at a mere glance and any
confusion as to type should, therefore, be impossible to
anyone who has once appreciated the simple distinction that
exists between biplane and monoplane. The appropriate-
ness of the term "wings," when applied to the supporting
members of monoplanes, should also be sufficiently self-
evident from the pictures to call for no further comment.
Moreover, after previous explanations it should be un-
necessary to remark that the wings do not flap.
Instead of flapping its wings, to do which would involve
constructional difficulty, the machine carries a propeller.
This is usually a two-bladed object built of timber, and it
measures about 8 ft. 6 in. or more in diameter. Owing
to its high speed of rotation, which commonly is between
900 and 1200 revolutions per minute, the propeller is in-
visible in some of the machines that are photographed in
flight.
It is common practice to put the propeller in front
and to mount it upon the engine crankshaft. A general
study of the designs of the machines makes it very clear
that the forward position — or " tractor screw " as the
propeller in front is often called — is structurally con-
venient.
Monoplanes were from the first designed with long
girder-like bodies, which necessitates a single air screw
being placed either in front of the wings or behind the tail.
When this form of the body became more common on
biplanes the tractor screw accompanied it, and in most
22 AVIATION
of the machines illustrated the propeller will be seen in
front.
Those that are exceptions include the Farman biplane,
in which the propeller is situated between the main planes
and the tail. Its presence in this position draws attention to
the dimensions of the outrigger framework supporting the
tail, which has to be large enough to clear the propeller on all
sides. Yet another interesting thought that arises from a
consideration of the propeller being in this position is that
its draught blows only on the tail. When the propeller stops
in mid-air, therefore, the tail suffers an immediate reduction
in relative speed, which may cause it to sag and so tilt the
machine nose upwards into a position that is called cabre.
With the propeller in front the draught affects both
wings and tail, and although not necessarily to an equal
extent its cessation would in this case cause a less marked
difference of the effect on the two members.
The only machine illustrated having two propellers is
the Wright biplane, which has been thus characterized
from its original design. In another chapter some attempt is
made to explain the action of propellers in an elementary
way, and it is there shown that large diameters tend towards
higher efficiency, especially in low-speed flight. The Wright
biplane is designed for comparatively slow speed, and the
makers thereof have always been strongly in favour of
using the largest propellers that it is possible to fit to the
machine. From the pictures it is evident that the builders
have incorporated the idea to the fullest limits of practical
possibility, for not only are there two propellers, but each
has a diameter as large as the ground clearance will permit.
Chains are used to drive these propellers, and a chain
is also used to drive the -very large single propeller on the
Cody biplane.
Timber, as has been mentioned, is used exclusively for
propellers at the present time and in most instances there
are only two blades. Some exceptions to this will, how-
ever, be noted among the various machines illustrated, the
Royal Aircraft Factory's biplane, B.E. 2, for instance,
having a four-bladed propeller of a design that has ap-
" Flight " Copyright Photos
THE PILOT'S SEAT
In the lower illustration the pilot is seen seated in a Bleriot monoplane, which is about to
start. I he mechanics are holding on to the fuselage against the pull of the propeller. The
upper photograph shows a totally enclosed Avro monoplane, the pilot being completely sur-
rounded by the body. These machines were in use in 1912.
SOME CONSTRUCTIONAL FEATURES 23
parently been very successful in use. In the construction
of wooden propellers several layers of timber are carefully
glued together so as to form a laminated block out of which
the propeller is carved to its proper form.
Of the engines used to drive the propellers, the Gnome
very properly deserves first mention owing to the un-
doubted stimulus that its properties gave to the develop-
ment of aviation during the period when it was exceedingly
difficult to obtain any other motor of a sufficiently light
weight for its actual power. Its peculiarity is that the
engine itself revolves instead of the shaft : the propeller
is, of course, fastened to a sleeve that is integral with the
engine casing. Its cylinders, of which there are either
seven or fourteen according to the power, are machined
from solid pieces of steel and are set radially about the steel
crank chamber.
This is, however, not the only type of radial engine,
nor are all those that have their cylinders so arranged
of the rotary kind. The Anzani on the Avro, illustrated
opposite page 22, is a stationary engine ; that is to say, its
cylinders are fixed to the body of the machine, while its
shaft, which carries the propeller, revolves.
Light weight is essential to successful aeroplane con-
struction and the primary reason underlying the design of
radial engines, as such, is the fact that cylinders so arranged
are compact and, therefore, economical of material.
Stationary engines, that is to say those in which it is
the shaft that revolves, are, for aviation work, often made
with their cylinders arranged in V formation. The Renault
engine on the Maurice Farman and on the B.E. 2, is a
popular example of the V type. Among the stationary
upright engines with vertical cylinders all in line, the
Austro Daimler on the Cody and the Green on the Dunne
monoplane are illustrated in the photographs.
The names of the engines, it will be noticed, differ from
those of the aeroplanes on which they are used. The
business of engine building is, very naturally, an under-
taking demanding specialization, so it originated as and
still remains a separate branch of the industry.
24 AVIATION
The engine, being the heaviest object carried by the aero-
plane, determines by its position the arrangement of some
other parts of the machine. The propeller, too, needs con-
siderable space in which to revolve and so determines the
height of the undercarriage necessary to provide adequate
clearance between the propeller tips and the ground. Nor
can this height be greatly curtailed by raising the propeller-
shaft, for the axis of the propeller represents the line of its
thrust, which cannot usefully be raised indefinitely above
the other principal objects of the machine.
In monoplanes the propeller-shaft is ordinarily on a
level with the middle of the body, in biplanes it occupies a
position about midway in the gap between the planes. It is
very clearly indicated in this position in one of the pictures
of the Cody biplane in flight, for on the Cody the propeller-
shaft is separate from the engine, and its elevated position
causes it to become a very prominent object in a side view of
the machine. The shaft in this case is, as has been men-
tioned, driven by a chain.
In the picture of the biplane B.E. 2, it will be observed
that the propeller-shaft is raised above the centre of the
body so as to be more nearly in the centre of the gap.
Alternatively, it will be noticed in the photograph of the
Dunne monoplane how the shaft lies below the level of the
wings because in that machine the heavier objects, including
the pilot, are also beneath the wings.
When the machine is flying level, the chord line of the
wings ordinarily makes a slight positive angle with the
horizon, and according to the angle, the shape of the wings
and the speed so does the lift vary per unit of wing area.
It is from data connecting these three factors that the size
of the wings is calculated. If pictures showing various
machines in side view are compared one with another,
some idea of the angle of incidence of the wing will establish
itself in the mind.
The angle of incidence is the angle made by the chord of
the wings with the line of flight, which in most cases may
be assumed to be represented by the propeller-shaft.
It has been explained that the chord is the line joining
SOME CONSTRUCTIONAL FEATURES 25
the leading edge of the wing with the trailing edge, and it
will be observed that the under side of the wing surface is
cambered so as to be concave to the chord.
Owing to the presence of the wing framework between
the surfaces, the upper face of the wing is more cambered
than the lower face. It is the upper side that contributes
most to the lifting effort of the wing in flight.
Another picture of interest to which it is necessary to
draw attention is that of the Breguet biplane, which is seen
standing on the ground in the photograph facing page 26.
Most machines when at rest occupy positions that differ
considerably from their flying attitudes owing to variations
in the height of the support under the tail. The tail-skid
is comparatively an insignificant member of the design :
provided it serves its purpose as a protection, the precise
position in which it causes the machine to stand is a matter
of small consequence. It is necessary, therefore, to be
cautious about judging the angle of incidence by the general
attitude of the wing as the machine stands at rest.
In the case of the Breguet biplane, moreover, there is
need to remember that the wings themselves are attached
to their spars by springs. These springs " give " under the
air pressure in flight and so cause the wings automatically
to change their angle of incidence. From the picture of the
machine on the ground it might be thought that the angle
of incidence was abnormally large, for the wings> when not
supporting the weight of the machine, do assume a very
steep pitch.
A peculiarity of this machine is that it has only one
spar to each wing. This spar is a steel tube. Ordinarily,
as at present constructed, the wings of aeroplanes, whether
monoplanes or biplanes, contain two spars each and they
are usually made of timber.
Wing surfaces, as at present used, invariably consist of
varnished fabric, which is tightly stretched over and
fastened to the wing framework. This framework ordinarily
consists of the two spars already mentioned and a series of
curved ribs joining them at intervals. These ribs produce
the camber of the wing : the interior structure is, or should
26 AVIATION
be, properly braced by steel wire ; otherwise, special
stresses are thrown upon the fabric and its fastenings.
It has been explained that the angle of incidence of the
wing and its camber determine its lifting effort per square
foot of surface at any particular speed. The speed is
limited by the resistance in relationship to the engine power;
the resistance is ordinarily expressed as a fraction of the
weight. Owing to the variation of lift with speed being such
as to provide a much greater effort at high speeds than at
low speeds, less wing surface will suffice for machines that
are designed solely to fly very fast. The relationship
between the lift per unit of surface and the speed is, with
ordinary wing-forms, such that if the speed is doubled the
lift per unit of surface rises to four times its original value
for the same angle of incidence.
For machines intended to be able to fly slowly with ease,
large surfaces are essential. When the weight to be carried
in flight is also heavy, the total wing area reaches an amount
that is preferably constructed in two units. These being
superimposed, cause the machine to be called a biplane.
Reverting to the subject of undercarriages, it is interesting
to study the various designs, and to observe the prevalence
of those that combine wheels with skids. This type of
landing chassis was originally evolved by Henry Farman,
and various modifications as well as the original form are in
extensive use.
As fitted to the Farman biplanes, each skid carries a pair
of wheels, which are joined by a short axle that is lashed to
the skid by elastic. A steel radius rod hinged to the axle
and the skid serves to limit the stretch of the elastic to its
proper range of action. If the elastic were to break under
the strain of a very rough landing, the skids and the under-
carriage struts still remain as a protection to the machine.
In several cases the breaking up of these undercarriages
has absorbed the shock of a faulty landing sufficiently to
save both pilot and the machine from what otherwise
might have been very serious consequences.
On the Bleriot monoplanes an altogether different type of
undercarriage is employed. It has no skids, and the wheels
,'
/TV
"•Flight" Copyright Photos
1. The Breguet biplane.
2. The " B.E. 2 " alighting on ploughed land.
3. The Deperdussin monoplane starting on ploughed land in the Military Aeroplane Tr'als.
SOME CONSTRUCTIONAL FEATURES 27
A. B. " Flight" Copyright Sketches
(A.) Sketch illustrating the method of attaching the axle by rubber cord to the skid of
a Henry Farman biplane.
(B.) Sketch illustrating- the elastic suspension on the Bristol aeroplane exhibited at Olympia,
1913. A brake drum is fitted to the wheel for pulling-up on the ground.
' ' Flight " Copyright Sketch
A typical central skid undercarriage, as exemplified on the
Handley Page monoplane.
28
AVIATION
have a great range of movement against the action of strong
elastic springs placed just outside the supporting columns
by which the wheel brackets are attached to the body of the
machine. While the softness of such a suspension has, of
course, many advantages, it is necessary to effect a skilful
landing in order to avoid bouncing.
"Flight ' Copyright Sketch
The Bleriot undercarriage.
For the support of the Cody biplane, steel springs are
used in conjunction with one pair of wheels and a strong
central skid. At the rear, this skid joins a member some-
what resembling a kangaroo's tail, which scrapes along the
ground to serve as a brake when the machine is coming to
rest. Ordinarily, no special mechanical device is provided
UNDERCARRIAGES
"Flight" Copyright Photos
The upper photograph shows the central portion of the undercarriage of the Cody biplane
used in 1912. The lower photograph illustrates a Bleriot monoplane of the same date.
SOME CONSTRUCTIONAL FEATURES 29
on an aeroplane for the purpose of checking its ground
speed after alighting.
Regarded as an appanage of the machine in the air, the
undercarriage is merely a nuisance, for it adds weight and
resistance. For the beginner, a substantial landing chassis
is a safeguard of some importance, but on machines built
for skilled pilots the undercarriage might often be less
conspicuous, were it not for the presence of the propeller.
Wheels are, of course, essential in order to enable the
"Flight" Copyright Sketch
A double skid undercarriage used on the Blackburn monoplane.
machine to run over the ground when starting, but it is
interesting to recall that the early Wright biplanes were
designed without wheels in order that they might carry as
little unnecessary weight into the air as possible.
Originally, a temporary track was laid on the ground for
starting purposes in connection with the Wright biplane.
It consisted of a series of planks standing on edge, and set
end to end. A thin steel rail protected the edge of the plank,
and in contact with this ran a trolley supporting the machine.
In order to facilitate initial acceleration, the trolley was
connected by a cord to a weight, which was released from
30 AVIATION
the top of a portable tower when the pilot was ready to
start. The falling weight pulled steadily on the machine,
and ensured that it should acquire sufficient velocity before
coming to the end of the rail. It will be understood, of
course, that it is essential to accelerate to flying speed
by running over the ground before it is possible to rise
permanently into the air.
It was not for some time afterwards that the Wright
biplanes were built with wheels on their landing carriages,
but the tower was abandoned by most of those who learned
to fly these machines, as it was found possible to obtain the
necessary acceleration from the propeller thrust. The
engine was started and accelerated to its proper speed in
advance, while the machine was held back by a catch that
the pilot could release from his seat.
Several of the illustrations have also been chosen for the
manner in which they bring the tail organs into prominence,
and it is instructive to compare them one with another.
Those machines that have boat -like bodies also exhibit a
general similarity about their tails. The fixed plane is
sometimes cambered so as to carry weight, as in the Deper-
dussin above mentioned, and sometimes is a flat plate, as in
the Hanriot monoplane illustrated on page 52. When it is
of this kind, the tail plane does not contribute to the support
of the weight. It is there merely in order to confer longi-
tudinal equilibrium and steadiness on the machine in flight.
The elevator usually forms a hinged extension of the
tail plane, and is often divided to make room for the rudder
in the manner that is clearly illustrated in the picture of
the Hanriot. The Breguet tail, which will be seen on page
26, is peculiar in having no fixed plane. Its horizontal
member is entirely elevator, and the vertical member is
entirely a rudder. They are supported upon a pivot, and
move together ; when the rudder is moved the elevator
also moves in its own neutral level.
Another modification of great interest appears in the
Cody biplane, on which the tail element consists of two
rudders, each of them carrying a small fixed horizontal
fin, These fins, which correspond to the fixed tail planes
SOME CONSTRUCTIONAL FEATURES 31
of the other machines, are of comparatively small area.
They are only just visible in the photograph on page 10.
The very large elevator in front is, however, a prominent
feature. It is supported on an outrigger framework of
bamboo, and is divided into two portions, which move
in sympathy with the warp.
"Flight" Copyright Sketch
Sketch illustrating: the control used on the Blackburn aeroplanes.
Turning1 the control wheel on its own axis operates the rudder through
the agency of pulleys and cables. Pushing the wheel to and fro controls
the elevator through the agency of the rocking shaft and the levers which
are attached to cables. Moving the wheel bodily sideways actuates the
warp through the direct attachment of cables to the control column.
It will be understood, of course, that the elevator and
the rudder are both organs under the direct control of the
pilot. In some machines, the rudder is operated by wires
from a pivoted bar under the pilot's seat ; in others it is
connected by a steel cable to a drum attached to a hand
wheel arranged in much the same way as it often is on
motor-boats. There are many modifications of detail
in the systems of control in present use, and in due course
there will doubtless be some attempt to encourage uni-
formity in such an important matter. For the moment it is
32
AVIATION
of greater importance to allow the various systems every
opportunity to prove their practical value in flight.
When the rudder is operated by hand, it is usual for the
column supporting the wheel to be pivoted at its base so as
to be movable as a lever in any direction. A to-and-fro
motion of the head of the lever is employed to operate the
elevator and a sideways motion controls the warp.
H&NO-LEVER. CONTdOLUNG
RUDDER: A. W\NC -
"Flight" Copyright Sketches
On the left, a simple pivoted lever control used on the Caudron aeroplane. Moving-
the lever to and fro operates the elevator through the direct attachment of cables to
the lever. Moving the lever sideways actuates the warp through the agency of a
rocking shaft. The rudder is independently controlled by a pivoted bar under the
pilot's feet. On the right is the control employed on the Wright biplane. The
handle of the lever is pivoted so that it can be independently moved at right angles
to the motion of the lever as a whole. This independent motion of the handle
operates the rudder. The movement of the lever as a whole to and fro actuates
the warp. A separate lever is employed to control the elevator.
In a photograph on page 42 can be seen the control of
the Bleriot monoplane, but the pivoted rudder bar is only
just visible. Although a hand wheel is fitted to the top of
the lever that normally stands upright between the pilot's
knees, this is only for convenience of manipulation. It is
not a wheel in the sense that a wheel implies rotation on its
own axis ; it is rigid with the lever proper and the control
SOME CONSTRUCTIONAL FEATURES 33
movements are made by moving it bodily. In order to
work the elevator, the motion is either forwards or back-
wards, and in order to operate the warp the motion is
either to the left or to the right of the neutral point.
A full understanding of the action of the warp necessitates
knowing something of the construction of the wings. They
consist of an exterior surface of fabric stretched tightly
over an interior framework of wood. The framework of
each wing of a monoplane consists firstly of two main
spars projecting from the side of the body of the machine
and extending to the wing tips.
Each spar is supported at intervals by wires that run
overhead to a mast or cabane above the pilot's seat, and
beneath either to another mast, or, more usually, to a
point on the chassis. Those wires that support the front
spar are fixed both to the overhead mast and to the chassis,
but those that belong to the rear spar pass over a pulley
or its equivalent on the upper side, and are attached to an
operating mechanism below the body.
The rear spar itself is hinged to the body of the machine,
and when the pilot moves sideways the lever that ordinarily
stands vertically between his knees, the wires leading to
" Flight" Copyright Drawing
Sketch from a photograph showing a Wright biplane with its planes warped.
the real spars are operated in such a manner as to cause
the end of one spar to be raised while the end of the other
spar is depressed by an equal amount.
Between the spars, at intervals of 12 inches or so, are curved
ribs of wood. It is to these ribs that the fabric is fastened,
and it is from their shape that the wing obtains its camber.
When the rear spars are moved in the manner thus described,
the effect is to alter the angle of incidence progressively from
3
34 AVIATION
shoulder to tip. The angle of incidence of the wing in which
the rear spar is lowered is increased, particularly towards the
tip, while in the other wing, in which the rear spar is raised,
the angle is correspondingly diminished.
Instead of warping the wings, some machines are fitted
with flaps in the trailing edges of their planes near the ex-
tremities. An excellent illustration of this system may be
seen in the photograph of the Farman biplane on page 21.
When at rest, the flaps hang down of their own accord ; in
flight they fly out in the wind, and are level with the wing
surfaces. A sideways movement of the control lever causes
one or other of the flaps to be drawn down against the wind
pressure, while the wire to the opposite flap is correspondingly
slackened.
Roughly stated, the rudder is for steering in the same
sense that a boat is steered ; the warp is for keeping the
wings level and for control against rolling in general ; the
elevator is for keeping the machine on an even keel and for
control against pitching in general. The indirect effects of
the use of these controls and the need for combined actions
under various circumstances are somewhat complicated, and
in order properly to understand this side of the subject, it is
necessary to discuss at some length the general problem of
the balancing and control of aeroplanes in mid-air.
Although the balance of an aeroplane in flight may be
maintained by human control of the various organs thus
described as characteristic of the design of modern machines,
the conditions of present-day flying are frequently so dis-
turbing as to render any craft extremely dangerous, even
for the expert pilot, unless possessed of some inherent steadi-
ness as a mere result of its proper design.
In order to arrive at reasonable conclusions regarding
this matter, it is clearly necessary to be careful to consider
in the first instance only those features of design that are
most obviously possessed in common by a variety of different
types that are known to fly well. If a number of well-
known standard makes of biplanes and monoplanes were
to be considered collectively, it would be observed in the
first place that every one of them is of considerable length,
SOME CONSTRUCTIONAL FEATURES 35
notwithstanding the fact that the wings themselves are
short from front to rear, and that the pilot and the engine
seem to need but little more room than is afforded by this
same dimension.
" Flight" Copyright Sketches
Sketches of tails as shown on machines exhibited at the 1913 Aero Show. The
Breguet tail is particularly notable inasmuch as it has no fixed plane. The
elevator and the rudder together form one unit, having- a motion in two separate
directions according as it is controlled for steering or elevation.
It will further be noticed that the engine and the pilot
are in all cases fairly close together, and that the under-
carriage is likewise compactly arranged when compared
36
AVIATION
with the immense span of the wings. In fine, the massing
of the objects that weigh most about a common centre in
"Flight" CopyrightSketch.es
Sketches of tail skids to be seen at the Olympic Aero Show of 1913.
the middle of the wings will be one of the first characteristics
to be noted as common to all machines.
In the case of biplanes the bulk of the weight so carried
SOME CONSTRUCTIONAL FEATURES 37
is located between the planes, and in some cases it will be
observed that the engine and the pilot's seat are raised
somewhat above the lower plane, in order to bring them
more nearly into the centre of a high gap. For obvious
reasons the undercarriage must lie below the rest of the
machine, but it is none the less evident that the designers'
endeavour is to keep it as short and as light as possible.
This concentration of the larger masses about a common
centre, which thus becomes the centre of gravity of the
machine, serves to emphasize the significance of the extreme
length of the machine. Merely judging the distance by eye,
it is evident that from front to rear most aeroplanes measure
about 30 ft. or more. With equal facility it may be esti-
mated that the span of the wings is even greater.
At the rear of the machine there is always a tail, which
has already been described as a group of organs ordinarily
comprising a fixed horizontal plane with a flap extension
called the elevator and a vertical plane that serves as a
rudder. The elevator and the rudder are under the pilot's
control, the tail plane proper does not move. The tail
portion of the machine is supported by a light skid when
on the ground.
Although not necessarily obvious to the eye, it is im-
portant to mention as a fact that the tail plane is invariably
set at a lesser effective angle of incidence than the main
wings. This arrangement is commonly described as the fore-
and-aft dihedral. If both tail and wings consisted of flat
plates, and sometimes the tail is a flat plate, the arrangement
would roughly represent the letter V, dismembered, opened
out, and turned on its side, thus / , but still
recognizable as a dihedral angle when speaking of planes.
The same feature, but far more pronounced, sometimes
characterizes the arrangement of the wings relative to each
other, in which case the principle is described as the trans-
verse dihedral, and may be represented thus \./
CHAPTER IV
EQUILIBRIUM IN THE AIR
Equilibrium and stability — Pitching, yawing, and rolling — Recovery
of balance — The importance of practice — Steadiness in flight.
IT has been the object of preceding chapters to present
side by side a picture of the aeroplane as a visible
machine and some conception of the invisible function
that is performed by the chief of its organs. In flight,
the weight of the aeroplane is supported by the reaction
between the wings and the relative wind created by their
motion through the air. So long as the proper relative
motion continues, the wings perform their function of
maintaining an upward pressure, but it depends on a variety
of circumstances whether that pressure continues to be
applied in exactly the correct way.
Some previous use has been made of two important
technical terms, the centre of gravity (C.G.) and the centre
of pressure (C.P.). It will be as well that the reader should
become thoroughly familiar with their meaning, for they
are as important to a proper understanding of how an
aeroplane is balanced as is a full conception of the idea of
relative motion to the realization of the fundamental
principles of its support.
The centre of gravity is the point where the weight of
the machine seems to be concentrated, and the centre of
pressure is the point at which the lift of the wings seems to
be focussed. Any object that is supported exactly at its
centre of gravity is always balanced in any position in which
it may be set. When it is not so supported, it tends to fall
into such a position as will bring the point of support
vertically in line with the centre of gravity.
38
"Flight" Copyright Photos
The upper view shows a Henry Farman biplane, of the later 1912 pattern, climbing ; the lower
picture illustrates a similar machine banking while turning about one of ihe pylones at the Herdon
Aerodrome.
EQUILIBRIUM IN THE AIR 39
A perfectly symmetrical wheel on an axle is in balance
irrespective of which spoke is uppermost, but the mere
presence of the valve on a bicycle wheel is sufficient to dis-
place the C.G. from the axis of the hub, and the wheel turns
round of its own accord until the valve is the lowest point.
The centre of support is the axis of the hub, and the C.G.
then lies vertically beneath it. Another position of equi-
librium exists when the wheel is turned so that the valve is
uppermost, but there is a distinct difference between the
stability of the two extreme positions. The slightest move-
ment of the wheel in the latter case (when the valve is
uppermost) is sufficient to capsize the arrangement ; on
the contrary, if the wheel is turned when the valve is the
lowest point, the original conditions automatically re-
establish themselves when the disturbance ceases.
Both positions, it should be observed, represent states
of equilibrium : but only one of them is stable. The
criterion of stability in such a system is whether the C.G.
is raised or lowered by the disturbance. If, as in the case
where the valve is undermost, the C.G. of the system is
raised by turning the wheel slightly, then the system is
stable because the C.G. naturally falls back again to its
original position.
An ordinary table is stable for this reason : when tilted,
the C.G. is raised ; when released, it falls back into position.
A tall stand on a narrow base is less stable than a low
table with its legs wide apart, because the C.G. rises less
when tilted and may more readily be pushed beyond the
limit .
It is necessary to refer to these elementary facts relating
to ordinary objects in order that the use of the terms
" equilibrium " and " stability " in reference to aeroplanes
may more adequately be appreciated. No word, perhaps,
has been more misused or is less clearly denned as to an
accepted meaning, than is the expression " stability " in
the terminology of aviation.
Like ships, aeroplanes are potentially liable to pitching,
rolling and yawing, and it is essential from the beginning
to recognize that some of these acts may at times be essential
40 AVIATION
to the guidance of the machine from one point to another
through space. If, for example, an aeroplane were incap-
able of being made to swerve at will, it could not be steered ;
on the other hand, a tendency to make erratic changes
of direction of its own accord would be described as direc-
tional instability. It is, then, evidently necessary clearly
to fix in the mind what qualities it is desirable that an
aeroplane should exhibit when in flight : not less is it
essential to consider what characteristics may reasonably
be expected of a machine situated as is an aeroplane in
the air.
In the first place, it is important to bear in mind that
the air does not provide a fixed platform as does the floor
in the case of the table just mentioned as an illustration of
stable equilibrium. When an aeroplane is canted, so that
one wing is lower than the other, the C.G. of the machine
has not necessarily been disturbed ; nor, even if it had
been raised, would it necessarily have cause to fall back
again to its former level.
Although by no means an accurate analogy, the diffi-
culty of balancing a marble exactly in the centre of a plate
gives a somewhat better idea of the situation than is to be
obtained from any point of view originating from a con-
ception of what ordinarily is understood by stability on
land. There is also a very ingenious sideshow, often to be
found at large exhibitions, that may assist the imagination
in grasping the breadth of the subject. It consists of a
flexible track that ceaselessly undulates in supposed re-
presentation of the waves of the sea. The usual sixpence
admission gains for the enthusiast the right to try to
pilot a raft -like trolley round the course, and serves inciden-
tally as a very good object-lesson in two forms of stability.
The machines in question are stable in the ordinary sense
to the degree of absolute security, for they cannot con-
ceivably capsize by any accident that might befall them
en route. On the contrary, the instability of their direction
is, so to speak, the very basis of the success of the show.
They scarcely move three yards without making sudden
swerves into one barrier or the other, yet those who practise
EQUILIBRIUM IN THE AIR 41
the art of steering them can negotiate the circuit without
collision, or would be able to do so were other pilots equally
expert with themselves.
When an aeroplane is canted, the forces brought into
play correspond with those that make the trolley run into
the barrier, and their effect is equally to tend to make the
aeroplane slip down sideways through the air. This motion
will be noticed as a characteristic of the flight of the paper
models described in a previous chapter, and it is important
to realize that it is solely because the models are free to
slide that they recover their equilibrium. When the
initial cant is due to a draught, the model slips rapidly
down an oblique path to leeward, and will probably bring
its flight to a premature conclusion on the floor unless
there happens to be sufficient height for the manoeuvre
of recovery.
Inasmuch as the obliquely sideways motion does tend
to restore the lateral balance, features of design that help
to emphasize the effect are frequently described as principles
of inherent stability. The most common of these is the use
of dihedral wings, that is to say, wings sloping upwards
from shoulder to tip. A very marked example of dihedral
wings is to be seen in the photograph of the Blackburn
monoplane facing page 52.
Again reverting to the paper model, another character-
istic phase of its flight is an undulating motion during the
earlier stages. When the motion dies out of its own accord,
the model is said to be longitudinally stable. With cambered
planes of single curvature, it will be found necessary to fit
a horizontal tail and to set this tail at a lesser effective
angle than the main wings in order to secure inherent
longitudinal stability of this order. It is important to
observe that although the pitching of an aeroplane may
cure itself while the machine pursues its general course
unchanged, the wings themselves possess no such power
of inherent recovery from rolling. It is essential, in order
to cure a canted position without personal control, that
there should be a sideways component of motion.
It is also very important to bear in mind what has above
42 AVIATION
been mentioned, because some confusion of thought on the
subject is at present rather prevalent. Principles such as
the transverse dihedral are sometimes described as having
the power to re-establish equilibrium of their own accord
while the machine pursues an axial course. But, as the
pressure on each wing is always at right angles to the wing
spar, the pressure on one wing is also balanced by the
pressure on the other wing, irrespective of their relative
positions. Consequently, there is no couple capable of
turning the machine about its longitudinal axis, which is
essential if the wings are to be put level again. It is when
the machine slides sideways, which it does as soon as it is
canted, that the pressure under one wing exceeds that of
the other and so brings into existence a restoring force.
All these movements would naturally seem to a spectator
on the ground to be evidence of instability rather than
otherwise, which points to the necessity of differentiating
between what I generally describe as weathercock stability
and stability in the absolute sense. A wind vane, which
may move all over the place, remains stable in its attitude
to the relative motion of the air in its vicinity : when the
wind veers or backs, the weathercock moves in sympathy.
Of this order is the longitudinal stability of the paper
model above described. It rocks of its own accord about
its transverse axis and so tends to preserve a constant angle
of incidence to the relative wind. When sliding obliquely
sideways, it displays what I call " compass " directional
stability inasmuch as its longitudinal axis remains parallel
to its original position, like the needle of a magnetic compass
that is moved from one place to another. If the model is
fitted with a vertical tail plane so as to give it weathercock
stability of direction to the relative wind, it will lose its
power of recovering its lateral equilibrium. Immediately
it begins to slide sideways, the tail fin acts like a rudder and
steers the plane so as to face along its new line of motion.
The oblique position, which is essential to recovery from
a canted position, is rendered impossible, and the model
speedily capsizes in a head-first dive.
This draws attention to a consideration of evident im-
1 Flight " Copyright Photos
THE PILOT'S SEAT
In the upper view is shown the Henry Farman type biplane and in the lower view the Bleriot
monoplane, both as used in 1912. In the lower view can be seen the control wheel in front of which
is a map holder. On ihe right is a compass. Louis Noel is the pilot in the upper view.
EQUILIBRIUM IN THE AIR 43
portance, namely, that the possession of one form of stability
may prevent the simultaneous existence of stability of some
other kind. It is evidently a question, therefore, of ascer-
taining what combinations are possible and of choosing
those best suited to the purpose of practical flight. The
early gliding experiments of the Wrights described on
page 128 have an especial interest in connection with this
aspect of the subject.
The whole problem of stability in air is a vast subject
that has as yet been but little investigated. There is reason
to hope, however, now that much of the more fundamental
laboratory research has been completed, that it will not be
long before a systematic series of experiments puts the
matter on a more satisfactory basis.
To those who have read thus far, the difficulties of the
subject should in some measure be apparent. But, to
some of the earlier pioneers who were unable to realize
their dreams of flight, the very existence of the problem
itself seems to have been unsuspected.
A German named Lilienthal, whose work is referred to
later, was perhaps the first to appreciate the situation in all
its bearings, to realize that even a few minutes' actual ex-
perience aloft would do more to advance aviation than
could possibly be accomplished by a whole lifetime of
thought. Whether he was the first to realize it or not,
however, is of small moment compared with the unquestion-
able fact that he was the first to put his belief systemati-
cally into practice, to perceive that brief flights were already
possible in spite of the absence of an engine and to build
for himself a little gliding machine, which he proceeded to
use as an aerial toboggan by flying down the side of a
hill. Perseverance, not priority, was his real merit.
It was real flying and Lilienthal soon had very good
reason to understand, as others have done since, that his
ideas as to the primary importance of the problem of
balancing were only too certainly correct. He realized
that the air pressure supporting an aeroplane is virtually
centred at a point and that as the machine has, so to speak,
no other leg to stand on, there might well be difficulty in
i
44 AVIATION
keeping it properly balanced under the varying conditions
of flight. Lilienthal, however, was thinking more par-
ticularly of the pilot's control of the machine than of the
machine's control of itself. The human element is, of course,
the determining factor in the situation in respect to any
form of vehicle, and more so in an aeroplane than in most.
It is essential, therefore, to introduce the subject of personal
control, and to realize the purpose and possibilities of
the various organs with which modern machines are pro-
vided.
In this connection, too, there is a factor that is perhaps
of more importance than any other in the modern machine,
and that is the steadying as distinct from stabilizing
influence of certain characteristics of the design. By a
steadying influence is meant the quality of checking the
oscillations in the sense of putting on the brake : it does
not imply the power of recovery. Moving the hand about
under water gives rise to more resistance than do similar
movements in air. If the hand is held edge-on under
water while one is travelling in a fast motor-boat, the
resistance to lateral movement is noticeably exaggerated as
compared with the conditions obtaining when the boat
itself is at rest.
The keel of a yacht, for instance, is far more potent to
resist a puff of wind on a sail when the boat is moving
quickly through the water than when it is at rest. The
resistance, however, is only maintained during the applica-
tion of the pressure, and as the result of the lateral dis-
placement of the keel : of itself, it is incapable of entirely
preventing the disturbance and it is impotent to restore
the initial conditions.
It seems conceivable that the wings themselves may
thus damp the tendency of an aeroplane to roll, but more
will need to be said upon this point in another place. Other
things need to be considered in design, as affecting the
control and steadiness in flight, quite apart from the sub-
ject of stability pure and simple.
It should be useful, therefore, to recapitulate the various
divisions of the subject in order that it may arrange itself
EQUILIBRIUM IN THE AIR 45
more systematically in the mind. Firstly, there is the
human control of the balance as performed by the manipu-
lation of various organs. Secondly, there is the need to
consider how far certain characteristic features of the
design may tend to steady the machine, although not
possessed in themselves of any inherent power to restore
balance. Thirdly, there are the principles of stability that
restore balance as the result of the motion of the machine.
Fourthly, there remains to be investigated whether the
aeroplane may be made stable to the point of being un-
disturbed by a real wind. Such stability might appropri-
ately be termed " platform " stability, in order to imply
steadiness and to distinguish the quality from the power
of recovery inherent in " rolling " stability.
In each section it is necessary to consider separately
the question of pitching, rolling and yawing ; then to
consider how one movement may affect another, and,
finally, to bear in mind the possible need for being able to
promote such movements at will for the purposes of directing
the path of the machine in flight.
In the broader use of the term, what ordinarily is called
longitudinal stability has to do with the prevention and
cure of pitching. Lateral stability is similarly related
to rolling, and directional stability to yawing from the
course. Of these three divisions, sufficient has been said
already to emphasize the especial significance of lateral
stability owing to the fact that any lack of balance involves
a sideways sliding of the machine from its proper course.
It will, therefore, perhaps be advisable to devote some
further space to a consideration of lateral equilibrium in
a separate chapter.
CHAPTER V
LATERAL BALANCE
Direction of pressure and direction of weight — The cause and the cure
of lateral disturbances — Steadiness and large span— Speed and safety —
Wing warping : its object and its effects — Cause and effect of sideslip —
Fins as stabilizers — Upturned wing tips as fins — Stability against gusts —
Negative wing tips and lateral stability.
WHEN an aeroplane is seen advancing from
directly in front, the upward pressure or lift
of its wings may always be assumed to be
acting in a direction perpendicular to the spars. The
downward force of the weight acts always vertically to-
wards the earth. If, therefore, the wings are canted,
their pressure is no longer precisely in line with the weight,
and there is, necessarily, a sideways component tending to
make the machine swerve off its former course.
On the assumption that the machine ascends into the
air with its wings level, it is necessary to account for the
disturbance of the balance by the introduction of some
extraneous force. This, however, is readily supplied by
supposing that the machine is struck by a gust. A gust,
for present purposes, is assumed to be a sudden veering
or backing of the relative wind.1
It is not necessary that the machine should be possessed
of vertical fin surfaces, against which the oblique wind
1 Special attention is drawn to this hypothesis because, while it is
fundamental to much of the argument that follows, it is presented only
as a personal line of thought and not as a generally accepted definition.
I am, in fact, assuming that atmospheric disturbances, so far as they
relate to the machine, cause angular oscillation of the vector representing
the relative wind. Such oscillations may be in any plane, but I assume
that the components of the movement in the horizontal and vertical
planes may be considered separately. It is the component in the hori-
zontal plane that is here referred to as a veering or backing of the relative
wind.
46
LATERAL BALANCE 47
may strike, in order to account for the tendency of a gust
to cant an aeroplane. The characteristics of wing-forms
as ordinarily employed suffice in themselves to explain
the occurrence, for if a gust is a sudden veering of the wind,
it is equivalent to a sudden spinning of the wings about
their vertical axis, as a propeller might spin on a vertical
shaft. Under such conditions there is an obvious tendency
for one wing to lift more than the other, and so to upset the
balance.
The consequence of canting the wings is immediately
to bring into existence a force tending to make the machine
slide obliquely sideways downhill to leeward.
As these are the conditions that tend to materialize on
modern machines, it is first of importance to consider in
what manner and to what extent they are actually cured in
practical flight, before discussing possible means for their
prevention. The subject, as has been explained, falls
naturally under a series of separate heads.
Firstly, there is the outstanding fact that machines
of many different types are flown with apparently equal
security by reasonably expert pilots, and that there is,
it would seem, some degree of inherent steadiness in them
that is distinct from the human element. Such steadiness
does not restore balance, but merely checks the severity of
the disturbance.
Secondly, there is the pilot with the controls at his
command.
Thirdly, there is the necessity of considering the effect
of allowing the machine to slip downwards to leeward, and
to inquire what principles, if any, are present that will
tend to restore the wings to their proper balance.
Fourthly, it is a matter of interest and importance to
discuss what means, if any, suggest themselves as possible
systems of prevention, as distinct from cure.
Some of the natural transverse steadiness of the modern
aeroplane is due, it has been suggested, to the fin-like action
of the wings themselves, which conceivably resist displace-
ment from their line of flight by dynamic reaction, just as
the keel of a yacht resists a sudden gust on the sail. In
48 AVIATION
this respect all well-designed aeroplanes should possess
the basic quality in common, although doubtless in varying
degree, and such would, in fact, appear to be the case in
practice.
Arising out of this point of view, there is reason to direct
particular attention to machines of relatively large wing
area and span. If it is in the keel effect of the wings them-
selves that the inherent lateral steadiness of the machine is
mainly centred, then one of the most direct methods of
enhancing this quality would apparently be to increase the
size and particularly the span of the wings.
This steadying effect of the wings is based on the fact
that a plane that descends while moving horizontally
is actually moving obliquely, and, therefore, makes an
angle of incidence to its line of flight. Thus, when a machine
rolls, the wing tip on one side has its angle virtually in-
creased, and vice versa on the other side. Such an effect
would tend to check the roll, but would have no power to
restore balance.
To do this it is necessary to make an actual difference
between the wing tip angles, and this is the purpose of the
warp. The wings are constructed, as has been explained,
so that they can have the angle of incidence at the wing
tip altered by a movement of a lever. The effect is to
establish a temporary difference in the lifting efforts of the
two wings in such a way as to restore the balance of the
machine.
It is, of course, the lower wing of a canted aeroplane that
has its angle of incidence increased by the warp. The centre
of pressure, therefore, tends to move on to the lower wing,
and in so doing it brings about a restoration of balance.
There is need for considerable discretion in the use of the
warp. The increase of lifting effort in a vertical direction
may be accompanied by an increase in the horizontal resist-
ance to motion. At large angles, the greater the lift the
greater also is the resistance that the wing experiences to
its flight through the air.
For very fine angles, the resistance may remain nearly
constant or even slightly decrease with an increase of angle ,
LATERAL BALANCE 49
but as the increase is continued the resistance ultimately
increases also.
Let us then apply this reasoning to the case of the warped
wings, and see how it may be expected to affect the machine
in the air. On the one side, we have an increased lifting
effort accompanied by an increased drag ; on the other, a
decreased lift, and, in consequence, less resistance to motion.
The engine as ordinarily installed on an aeroplane with a
single propeller is pushing the machine forwards by a thrust
applied at a point immediately between the wings. If,
therefore, the resistance of one wing is made greater than
that of the other, it follows that the machine as a whole
must at once tend to spin about its own vertical axis in
space. In fine, the first effect of wing warping is ordinarily
to engender a " spin" ; i.e. to make the aircraft yaw.
This is extremely important, not only from the navigator's
point of view, but from its consequences in the aerodynamic
sense. The lifting effect of a wing depends even more on its
relative velocity than it does on its angle of incidence. If,
therefore, the effect of the greater drag on one wing is to
cause it to slow down in speed while the other begins to
move faster than before — which it necessarily does if the
machine begins to yaw — an immediate consequence of
this relative difference in speed is to cause the lift of the
slower wing to be diminished while the lift of the faster
wing is increased.
If this happens, the faster wing rises and the slower
wing falls. But it is the slower wing to which the warp was
applied in such a way as to increase its angle in order that
it might experience an increased lift thereby, and so be
raised. We are thus faced with the situation that wing
warping may do precisely the opposite of what was in-
tended.
If we assume that the purpose of warping on some par-
ticular occasion is to restore the natural balance of a machine
that has been canted, then there is no doubt as to the dis-
advantage of its yawing effect. If the machine tends to
yaw while already canted, the balance will be still further
disturbed.
50 AVIATION
Clearly, this effect of the warp needs the simultaneous use
of the rudder as a counteracting couple. If, when the wings
are warped, the rudder is employed at the same time, so as
to tend to steer the machine in a sense contrary to the drag
of the lower wing, the original course may be maintained,
and the warp itself rendered effective in the manner de-
scribed. It is evident, however, that the success of the
operation depends on the skill with which the pilot handles
his levers.
It has been remarked that the practice of wing warping
originated with the Wrights, and it is equally interesting to
observe that they made subject-matter for a master patent
out of the necessity for the combined action of the warp and
the rudder. A note on their legal position appears in the
Appendix.
Although wing warping, or its equivalent, is universal to-
day, the early Voisin biplanes used in France by Delagrange,
Farman, and other pioneers, had no such means of lateral
control. These large " box kites," as the larger biplanes
are nicknamed, were fitted with elevators in front and
rudders at the rear. The latter organ was partially enclosed
inside a huge box-like tail. According to Hargrave, who
invented the box kite in Australia, and recommended it
as a principle of aeroplane construction long before it was
actually so used, the system ought to possess strong powers
of recovering its balance. In any case, the pilot could always
assist recovery by steering outwards with the rudder.
This, by increasing the relative speed of the lower wing,
imparted to that side of the machine a greater lifting force,
and thereby tended to restore equilibrium.
It is of the utmost importance to realize how inti-
mately steering movements are associated with lateral
balance.
Even when we pass on to consider the consequences of
allowing an aeroplane to sideslip to leeward, the first point
that it is of importance to observe is that the machine has
changed its course.
An explanation of the force causing sideslip to leeward
has already been given, namely, that it is due to the wing
LATERAL BALANCE 51
spars being canted and so tilting the direction of the wing
pressure from the vertical.
This tilt introduces a horizontal force in addition to the
vertical lift, and the machine commences to turn in a
circle as if it had been purposely tilted for that purpose.
At the same time, however, it slides downwards, for the
tilting of the wings reduces the vertical component of
the force to a value that is insufficient entirely to support
the weight of the machine.
As, for the moment, we are considering only the initial
disturbance and immediate recovery therefrom, it is con-
venient to ignore any reference to the circular path and
to consider the downward slide as a simple lateral com-
ponent of the motion taking place along the axis of the
wing spar.
In order ^ to understand the origin of the forces that
restore balance, it suffices to consider this lateral com-
ponent of the movement as a motion apart. Suppose the
wings to be represented by the ballasted flat plate that
serves so well as a basic experiment in aerodynamics. It
is apparent that although the sideways motion is one in
which the plate proceeds narrow edge first, it is none the
less an aeroplane, and it will equally have its C.P. nearer
to the leading edge than to the trailing edge. The C.G.
being central, the leading edge will, therefore, tend to rise,
and as the leading edge represents in this case the lower
wing tip of the aeroplane, the action is one that restores
lateral balance.
From a consideration of the fact that a gust may be
of very brief duration, it would seem that in practice the
majority of disturbances may be reduced to a mere flicker.
But if the disturbance were such as to cause a severe loss
of equilibrium, the distance that the machine might have
to sideslip before righting itself would be so great as to be
highly dangerous at all ordinary flying altitudes.
And while on this subject, attention may well be drawn
to the necessity for keeping the lowermost wing well to
the front during a sideslip. It is only by virtue of its
relatively advanced position that it can hope to entice the
52 AVIATION
C.P. on to its surface. Steering inwards, that is to say
towards the direction of the sideslip, would cause the lower
wing to retreat and the upper wing to advance through
the air. Such action would, therefore, tend to augment the
loss of balance. Equally, an excessive amount of fixed
vertical tail surface, such as would give weathercock direc-
tional stability, and tend, thereby, to make the machine
swing into line with its relative motion, would be a
disadvantage once such a sideslip had started.
It is on its inherent absolute or compass-like directional
stability, that the ballasted flat plate depends for its re-
covery of balance. In a system such as the aeroplane,
which does not possess the same simplicity of form, it is
apparent that some feature is needed to counteract the
tendency of the rudder to promote a weathercock spin.
The use of a forward fin naturally suggests itself, but
is also seen to be a possible structural difficulty in its
elementary form, owing to the necessity of avoiding for-
ward projections on certain types of aeroplanes.
One way of acquiring a forward fin is to slope the wings
upwards (the lateral dihedral) and to arrange the C.G.
of the system slightly behind the C.P. on the wings. This
involves carrying load on the tail or raising the axis of the
propeller.
Another method is to turn up the wing tips only, and
then swing the wings backwards slightly, which causes the
upturned portion to face somewhat forwards, and so to
project its virtual fin above and in front of the machine.
Turning up the trailing corners of the wings is, in effect,
doing the same thing.
In addition to looking after the compass directional
stability, these virtual fins, being above the C.G., also
enhance the quickness of recovery. Dihedral wings .are
notable in this respect owing to the fact that their virtual
fin is well above the C.G. Upturned wing corners, on the
other hand, tend rather to enhance the compass directional
stability, by projecting their fins well in front of the C.G.,
and such machines might, therefore, be expected to have
some inclination to roll.
-
\ \ -
"Flight" Copyright Photos
1. A Hanriot Monoplane of igi2.
2. An example of the dihedral angle in a front view of the Blackburn monoplane.
3. An example of negative wing tips on the Dunne monoplane.
4. View from above of the Handley Page monoplane, which has crescent-shaped wings with
their tips slightly upturned at the trailing edge.
LATERAL BALANCE 53
It is evident that the best position and size of such
fins would be a matter for elaborate investigation. To the
mathematical aspect of this phase of the subject, Professor
Bryan and Mr. E. H. Harper, of the University of North
Wales, have devoted considerable time and attention,
and Professor Bryan's book should be studied by all who
have mathematical minds. The importance of their work
lies in the method that it lays down for the treatment of
this phase of the subject : The " mathematical machine "
provides results in accordance with the material supplied
to it, and must not be blamed if inadequate data produce
unpractical solutions. The science of the mathematician
is essentially limited to remodelling the facts that consti-
tute his hypothesis.
While the subject of stability in still air forms an im-
portant introductory field of research, practical flying
takes place in winds, and any still-air stabilizing device,
such as a fin, at once becomes a target against which a
gust can strike to disturb the balance of the machine.
The absence of fins does not prevent the disturbance,
for it has already been explained that the C.P. moves in
sympathy with a veering wind. Nevertheless, if the fin
augments still-air stability, that is good prima facie evidence
why it should also increase the disturbing effect of a gust.
A ballasted flat plate of the kind described in a previous
chapter, if flown in still air, manifests considerable steadi-
ness of balance and direction. Should it enter a region
of draught, however, it will cant and slide down obliquely
sideways with great rapidity. If there is sufficient room,
it will recover its balance, but from the heights at which
such models are ordinarily launched, it will more often
strike the floor.
This and other considerations seem to emphasize the
fundamental importance of trying to prevent entirely the
loss of lateral balance in windy weather, notwithstanding
the fact that most well-designed machines appear to recover
their balance with a mere flicker of movement, and are
ordinarily extremely steady in the hands of expert pilots.
One system that has been tried may be described as the
54 AVIATION
"automatic warp," in which the wing spars are so dis-
posed as to make a gust tend to warp the wing of its own
accord in such a way as to "spill the wind."
As this action is communicated to the pilot's hand, it is
apparent that its popularity depends in a large measure
on individual taste. Some expert pilots like the system
very much, others are less favourably disposed towards it.
It will be observed that it is a principle that tends to
neutralize the efficacy of the dihedral angle, for the
dihedral essentially depends on the wings being subjected
to a difference of pressure, which it is the purpose of the
automatic warp to prevent.
It may now be of interest to consider how far it would
seem possible to make an aeroplane inherently laterally
stable in the absolute sense ; that is to say the prevention
of the sympathetic travel of the C.P. with a veering wind
on rigid wings.
Thus far a gust has been denned as a veering or a backing
of the wind, and in the argument that follows, it is important
to remember the limitations of this hypothesis. From
the fundamental conception of relative motion, it is evident
that a veering wind may be replaced in still air by a clock-
wise spin of the wings about a vertical axis passing between
their shoulders.
If the vertical axis is assumed to be fixed in space, so as
to facilitate a clearer mental picture of the process, the
rotation of the wings thereon will resemble the rotation of
a propeller on a vertical shaft. There is, however, the very
important difference that while each blade of the propeller
is properly inclined to its direction of motion, in the case
of the aeroplane wings only one of the pair is in a correct
attitude for either direction of rotation. The other wing
makes, in fact, a negative angle of incidence to its path.
It is thus very clear that the wing having the positive angle
of incidence will lift while the other will tend to fall, in
short, the wings will become canted.
In flight, the conditions may be mentally pictured by
supposing the vertical axis to be advancing in an upright
position and the rotation of the wings thereon to be taking
LATERAL BALANCE 55
place slowly at the same time. The wing that advances in
the direction of motion will obviously tend to rise, while
the wing that is retreating tends to lose its lift. It is this
action that causes a boomerang to " bank " and so to steer
itself back to the thrower.
From the above argument it seems evident that if a
pair of wings rotating about a vertical axis in still air did
not exert any lift at all, then neither would their balance
tend to be disturbed by a veering wind.
The only form satisfying this condition is one in which
the wing tips are permanently negative. When such wings
rotate about a transverse axis, the negative tip of the
advancing wing may neutralize the increasing lift of its
positive part ; on the other side, the negative tip of the
retreating wing will have become positive to its own direc-
tion of motion and will, therefore, tend to lift.
By suitably proportioning the angle from shoulder to
tip, it seems possible that a pair of wings might be made
laterally stable against veering and backing winds within
useful limits.
When advancing in ordinary flight, the centre portion
of the pair of wings would present a surface positively in-
clined to the direction of motion and to this would be due
the support of the machine.
The negative tips would represent an added load to be
carried, and to that extent the machine would be relatively
uneconomical of power. Some lack of economy might,
however, well be tolerated upon occasion for any real
measure of inherent lateral security of balance.
Owing to the wing tips being furthest from the vertical
axis, their relative velocity when turning about that axis
is greater than that of parts nearer to the centre : it is
feasible, therefore, that the extent of the negative surface
should be less than the area set at a positive angle, for the
relative effect will be in the ratio of the squares of their
relative speeds.
When advancing together in flight, the relative speeds
of all sections of the wings are the same, consequently the
larger area of the positive part will predominate, and its
56 AVIATION
surplus lift over and above that required to neutralize the
load due to the negative tips will be available for the support
of the machine.
The stablizing influence of negative wing tips has been
discussed mathematically on the Bryan method by Mr.
J. H. Hume-Rothery in an article in Flight, Vol. V,
page 64.
A question of evident importance that arises in the
mind after some little consideration of the foregoing argu-
ment is how such a machine may be steered. It has been
shown to be fundamentally necessary that it should not
cant when it turns on its own vertical axis, yet such a turning
motion is precisely what a rudder effects, and it is ordinarily
because the wings automatically make their own bank
that the use of the rudder becomes an effective organ of
steering control.
Steering possesses so many problems of interest, how-
ever, that it may be well treated separately in a chapter by
itself.
CHAPTER VI
STEERING
The true purpose of a rudder — Its manner of action — How a ship
answers the helm — The balance of power — Instability and the importance
of the rudder — Banking for the turn — The centrifugal couple — The differ-
ential negative warp.
THERE is perhaps no object of a technical nature
so universally familiar by name, appearance, and
purpose as the rudder. Everyone knows that a
rudder is used to steer the craft to which it is attached ;
few, comparatively speaking, clearly realize the precise
means by which the rudder accomplishes its object.
Newton defined as the first law of motion that a mass
moving in a straight line would not change its course unless
a force were applied to it along the direction in which it is
desired that it should accelerate. A rudder, owing to its
usual position some considerable distance behind the centre
of gravity of the craft to which it is attached, has no in-
herent ability to apply such a steering force, and its utility
for the purpose for which it is intended depends wholly on
the indirect consequences that attend its own direct action,
which is of another kind.
The direct effect of a rudder relates to the control of
movements about the vertical axis of the craft. Such
movements may conveniently and appropriately be referred
to under the general term " yaw." It is the tendency of the
craft to yaw on its own vertical pivot that the rudder is used
either to check or to initiate as the case may be.
When steering a straight course, the rudder is used to
counteract disturbances that otherwise might give rise to
yawing. Observe, for example, the behaviour of flotsam in
a stream, how each little piece gyrates as it moves onwards.
57
58 AVIATION
Consider also how unstable would be an arrow without the
steadying influence of its feathers, which form a neutral
rudder, and the action of which is this sense has been
referred to in a previous chapter.
In its initiative capacity, the rudder causes that to happen
which formerly it helped to prevent. When the rudder is put
over, the immediate and direct effect is that the craft begins
to yaw ; the craft as a whole tends to continue its straight-
line motion under the influence of its own momentum.
In the case of a ship, the consequence of a slight yaw
is that one side is thereby presented obliquely to the
direction of motion, and the reaction thereon is itself
oblique, and so possesses a component force at right angles
to the original course. This lateral component of the re-
action acts through the C.G. of the system, and initiates
acceleration at right angles to the original velocity ; their
compounded effect produces a curved path of motion that
persists so long as the helm is held over and an axial driving
force is applied to maintain propulsion.
Incidentally, it is of interest to remark that according to
the design of the boat so may the centre of the pressure re-
action on the hull be in advance of or abaft of the C.G. When
it is located forward of the C.G. it has the effect of augment-
ing the yawing, andthus of enabling the boat to be manoeuvred
more readily ; on the contrary, it makes the steering of a
straight course more difficult. When the C.P. is behind the
C.G. it opposes the rudder, and makes the ship less easy to
put about, but such a boat will steer a straight course of
its own accord, owing to the inherent weathercock direc-
tional stability of the system.
In the case of an aeroplane, which has no appreciable
extent of vertical surface in the vicinity of the C.G., a
slight yaw will of itself present nothing equivalent to the
side of a ship against which the air can react in the above-
described manner. But, when an aeroplane with positive
wing tips is caused to yaw, one wing tip is thereby accelerated
while the other is retarded, and so a bank is established
thereby, which in turn tilts the direction of the air pressure
on the wing.
STEERING 59
It is this tilting of the air pressure by canting the wings
that provides the steering force in the case of an aeroplane ;
which being so, it is at once apparent that if other means
than the rudder were available for tilting the wings the
rudder itself might be dispensed with as a steering organ.
One alternative method of initiating a bank is to warp
the wings. The manner in which the wings of aeroplanes
are at present warped is such that the positive angle of one
wing tip is increased while the positive angle of the other
wing tip is diminished. With any aeroplane surface at a
positive angle of inclination to the line of flight, the pressure
reaction is obliquely upwards and backwards, and if the
angle is increased, both these component forces will, ordi-
narily, also be increased. The wing tip that has its angle
of incidence increased by the warp will thus usually tend
to rise and to retreat ; a combination that is in opposition
to the requirements of steering, as may readily be seen by
reviewing the essential conditions that attend thismanceuvre.
While travelling on a curved path it is evident that the
inner wing tip must be flying at a slower speed than the
outer wing tip. It is equally self-evident from their banked
attitude that the inner wing tip must be the lower one of the
pair. While banking, it is, therefore, clear that the tendency
of the inner wing should be to descend and to decelerate,
which is an effect that cannot, in general, directly be induced
by the warping of a wing tip so as to increase the positive
angle. When a positive angle is increased, the tendency to
rise is mostly accompanied by a tendency to retreat ; if the
rise is otherwise prevented, the retreat, representing a loss
of velocity, may result in descent, but the descent is not a
direct consequence of the force first brought into play by
the warping of the wing.
In connection with these tendencies to retreat and to
advance it is of fundamental importance to realize the
significance of what may be termed the balance of power
on the two wings.
Suppose a flat -sided pencil is placed on the surface of a
table, and an attempt is made to propel it broadside-on by
pushing it with another pencil applied to the middle of its
60 AVIATION
length ; the pencil so pushed will oscillate about its vertical
axis with pronounced directional instability.
The causes that initiate the yaw on the part of the pencil
so propelled are local irregularities in the surface of the
table, which represent a variable resistance to motion.
The power applied to the purposes of propulsion is divided
equally between the halves of the pencil, and if the re-
sistance experienced by one part exceeds that opposing
the other, the balance of power will not permit of both
parts travelling at the same speed. To assume that they
did continue to travel equally fast would be to specify
that one-half of the pencil was receiving more power than
the othe.r half, which would not be possible in the system
of propulsion described ; such an assumption would thus
be an evasion of the hypothesis.
This simple experiment is instructive inasmuch as it re-
presents to some extent the relationship of the wings to the
power plant of an aeroplane. It is not possible that a single
engine and propeller situated on the longitudinal axis should
supply unequal proportions of power to the two wings ;
consequently any lack of equality in the resistances that they
experience in flight must immediately be reflected in the
commencement of yawing.
Directional stability in such a system as an aeroplane,
which has its wings broadside-on and its power applied at
a point midway along the transverse axis, does not depend
primarily on the presence of a rudder at the rear end of the
longitudinal axis, but upon the equality of the resistances
opposing the broadside motion of each wing spar. Tem-
porary disturbances that tend to engender yawing may,
however, be damped by the inertia effect of the rudder
plate, and indeed a rudder tends to assume a position of
first-class importance as an organ of control in a system
that lacks inherent lateral and directional stability in the
wings themselves.
The intimate connection between lateral and directional
stability has been emphasized in the preceding chapter,
and it may be made more apparent here by considering the
process of establishing a bank and steering a curved course.
STEERING 61
The warping of positive wing tips does not in itself directly
serve the purpose of banking, because, as has been explained,
the component forces engendered on opposite sides of the
machine do not harmonize with the precise requirements.
From a consideration of the problem from the point of view
presented by the balance of power, it is apparent that the
wing so warped as to have its angle increased will ordinarily
retreat. On the other side, the wing will advance ; but its
diminished angle of incidence will require a higher relative
velocity in order to support the same weight, and so its
acceleration will not at first tend to make that wing rise.
Thus, it is evident that even if the machine is ultimately
caused to bank by the acceleration of the outer wing, a dis-
proportionate spin will have accompanied the manoeuvre
and this extra spin will in itself be evidence of instability.
That this is so, may perhaps be more readily shown by the
aid of a simple artifice that I find of some service when
mentally picturing conditions of steering on a circular
course.
Imagine the machine to be proceeding around a maypole
on the top of which one is sitting. From this vantage point
there is obtained a perfect plan view of the aeroplane, and
it helps to fix ideas if it be supposed that there is a thread
from the top of the pole to the button on the pilot's cap.
Also let another thread be stretched from the inside wing
tip to a point lower down the pole. The wing spar itself
must be in line with this latter thread while the upper
thread is at right angles thereto.
As the machine continues to fly on its circular course,
both threads, which may be supposed to be attached to
rings riding on the pole, make the same angular motion
about the axis of the pole, and any stretching of either
thread would thus be a sign of instability.
Such stretching of the threads might be caused by an
alteration of the bank or by yawing, neither of which move-
ments should be possible save under the pilot's control in
an aeroplane that is regarded as inherently stable.
To assume, as was done just now, that the aeroplane
initiates its circular course by a disproportionate spin is to
62 AVIATION
break the lower thread at the very commencement of the
manoeuvre. Evidently, what is required when banking for
a turn is to avoid such spin ; with positive wing tips this is
usually only possible by applying the Wrights' practice^f
simultaneously using the rudder and the warp. J£ .the
rudder is used alone, the bank is again due to the dispro-
portionate spin, and the position is only an improvement
on the warp alone in so far as the advancing wing possesses
its natural angle, and so begins to rise at once.
By ruddering against the resistance of the warped wing,
that is to say by increasing the angle of the wing that tends
to be caused to advance by the effect of the rudder, a proper
banking movement is accomplished. In this case, the wing
with the greater angle rises ; moreover, it continues to rise
indefinitely, and will capsize the machine unless the rise is
checked by a reversal of the warp so as to diminish the angle
to an extent corresponding with the relative speed at which
the wing has to fly on its circular path. As the relative speed
depends on the radius, and as the radius depends .on the
bank and speed of flight, it is evident that the manoeuvre of
establishing and maintaining a circular course with positive
wing tips is ordinarily one calling for considerable skill and
experience.
Equally is it clear that in the proper use of the rudder by
the pilot lies the safety of the situation ; indeed, many
pilots prefer not to use the warp at all if the machine will
bank sufficiently under the action of the rudder alone.
In the original Wright biplane, the rudder and the warp
were connected to a universally pivoted lever, so that one
was operated by a to-and-fro motion, while the other was
operated by a sideways motion of the lever. A diagonal
movement of the lever thus operated both simultaneously.
In a later design the handle was hinged to the warp lever so
as to provide independent rudder control in a more con-
venient form. It is usual on other machines to operate the
rudder by a pivoted foot rest, or by pedals, or by the rotation
of a hand wheel.
That the steering of a closed circuit was early recognized
as a crucial test of the pilot's ability to really fly, may be
STEERING 63
judged by the fact that the first Grand Prix d' Aviation of
50,000 francs was offered by M. Deutsch de la Muerthe and
M. Archdeacon for the first one -kilometre circuit. This
prize was won on 13 January, 1908, by Henry Farman on a
Voisin biplane, and his feat undoubtedly marked the be-
ginning of a new phase in the serious development of the art.
That the Wrights in America had four years previously
brought the mastery of their own machine to a state of far
superior perfection was a fact either doubted or forgotten
by the enthusiasts on the aerodromes of France, and it dis-
counted neither the merit nor the encouraging effect of these
later achievements.
If the manoeuvring of a circuit was regarded as a test of
the pilot's ability to take care of his machine, so, it seems to
me, might the steering of a circular course with fixed con-
trols be considered as a criterion of the aeroplane's ability
to take care of itself ; in fine, as a test for inherent stability.1
Reverting to the main problem of steering, it has been
shown that none of the means now available is quite satis-
factory for the initiation of the banked attitude that is
proper to the condition of flying on a circular course. It
will also have been apparent, as it was when considering the
problem of balancing during straight flight, that it is the
positive wing tips that are the seat of the trouble. In the
previous chapter I endeavoured to show that negative
wing tips potentially afford means for stabilizing the wings
during straight -line flight ; it remains now to consider if
they equally seem able to remove the objections to positive
tips when steering.
The reaction of the air pressure on a negative tip is down-
wards and backwards, and in straight -line flight these com-
ponents would be in equilibrium about the horizontal and
vertical axes of the machine, by warping the wings so as to
increase the negative angle of one tip relatively to the other,
the equilibrium is momentarily disturbed in such a way as
to make the wing having the greater negative angle tend
to descend and to go more slowly.
While in the act of descending, its negative angle is
i See page 145.
64 AVIATION
virtually diminished. This tends to check the descent.
By flying more slowly, the down pressure on the wing tip
is reduced, which also tends to check the retardation, for
there is always the balance of power available to maintain
the speed of that wing at the highest value compatible with
the load that it carries.
It would seem, therefore, that the effect of the differential
negative warp should be dead beat, that is to say the
machine should automatically assume a canted attitude
appropriate to the new conditions established by the warp,
and should be capable of staying thus without culminating
in a dangerous position.
It has been explained that the differential positive warp
either tends to destroy the bank or to culminate dangerously.
If the lower wing has the lesser resistance, the balance
of power tends to accelerate it, and so to increase its lift,
which will ultimately destroy the bank. Alternatively, if
the lower wing has the greater resistance, the tendency is
for the outer wing to accelerate and to rise indefinitely.
With negative wing tips, the acceleration of the lower wing
tip would increase the air load on it, and so maintain the
bank, while in the other case either the acceleration or the
rise of the outer wing tip would increase the top pressure,
and prevent the continuation of the movement.
It appears to me, therefore, that the differential negative
warp potentially affords a safe control, by which I mean that
any possible movement of it, whether intentional or other-
wise, causes the machine to perform a true steering manoeuvre
that will not culminate dangerously.
A rudder should, of course, be unnecessary on a machine
controlled by the differential negative warp, for the action of
a rudder, as has been explained, is merely to initiate or check
a spinning or yawing of the machine, and neither action is
required in the full realization of such a system.
Inasmuch as it is necessary to provide for the personal
direction of any aeroplane, and in so far as the actual ex-
perience involves banking the machine — which is in itself
potentially dangerous if there is inadequate power — it seems
to me at present that a safe control as above defined is
STEERING 65
about as near as one may readily attain to the practical
solution of the stability problem.
A safe control, I think, might very well satisfy the
requirements of experienced pilots without any resource to
permanent negative wing tips for the sake of endowing the
machine with inherent stability at all times. Washed-out
wing tips capable of being made negative at will would
improve the speed and climbing qualities of the aeroplane,
and provided that the pilot could not make a mistake in its
control, there would not necessarily be any very serious
objection to being liable to be caught by a gust.
In windy weather it would always be open to the pilot to
stabilize his machine in straight flights by making both
wing tips equally negative. The control mechanism would,
of course, have to be re-designed, and preferably made so as
to be capable of single-handed operation.
In connection with the subject of the negative warp, it is
interesting to refer to the investigations of Dr. E. H. Hankin,
who studied with the greatest care the soaring flight of birds
in India. His observations were published in full in Flight
during August, 1911, and from them the following quota-
tions have been taken :
" I first obtained a clue to the nature of steering move-
ments by observing the flights of the black vulture. . . .
Occasionally the tip of one wing will be seen to be depressed
downwards momentarily and then raised at once to its
original position. . . . After the movement there is almost
time to formulate in words which way the bird is going to
turn before the commencement of the turn can be recognized.
In my notes I originally described this movement as a
dipping downwards of the wing tip. This phrase was soon
abbreviated to dip, by which term I propose to refer to the
movement in future.
" It is necessary to consider how the dip is brought about.
The first possibility that suggested itself to me was that it
was caused by some intrinsic muscles of the wing. But on
examining the wing of a dead bird, it appeared to me that
the range of possible movement at the carpal-joint was less
than my observations had led me to expect. It then
occurred to me that perhaps what really happened was
'
66 AVIATION
that the whole of the wing was rotated until the air pressed
on its upper surface instead of on its under surface. . . .
In order to decide between these two possibilities I dissected
the wing of a black vulture and found that neither of the
above suggested explanations is an adequate statement of
the facts of the case.
" None of the intrinsic muscles of the wing have any power
of making a dip movement by any direct action. But, on
the other side of the ulna, I found three muscles that have
the power of rotating the front edge of the outer part of the
wing. Supposing the wing is extended horizontally, then
if these three muscles come into action, the front edge of
the wing tip becomes depressed. That is to say, the wing
tip is rotated round the axis of the wing. The rotation is in
such a direction that the air ceases to press on the underside
of the wing tip feathers. Instead, it presses or tends to press
on their upper surfaces. Hence the tips of these feathers are
bent downwards, producing the appearance of the dip
movement. From the dorsal aspect of the wing, two muscles
may be seen that have the power of rotating the front edge
of the wing tip in the opposite direction. These muscles
come into action to return the wing tip to its original
position. I have also found these muscles in the wings of
the common vulture, the adjutant, and the sarus."
In Chapter XIV will be found some brief account of the
Dunne aeroplane, which actually possesses negative wing tips
and makes use of a differential negative warp control without
a rudder.
CHAPTER VII
LONGITUDINAL STABILITY
The ballasted flat plate and wing of single camber — The fore-and-aft
dihedral as a speed regulator — Stalled — The dive — An experiment by
Orville Wright — The reflexed wing — The Fales section.
EJGITUDINAL stability, it has been explained
in a preceding chapter, is concerned with the
pitching of the aeroplane in the air. Such motion
takes place in the form of a partial rotation about the
transverse axis, which, for the sake of argument, may be
supposed to be coincident with one of the wing spars of a
monoplane.
In the absolute sense, longitudinal stability would
imply that the fore-and-aft axis of the machine was never
disturbed from an attitude parallel to the horizon ; and if
such were the case, ah1 movement, including that of ascent
and descent, would necessarily be accomplished on a level
keel. Instead of the modern glide with the head of the
machine pointing towards the earth and the tail towards
the sky, the aeroplane would merely subside obliquely
downwards through the atmosphere as the result of switch-
ing off the power.
Such absolute stability as is hereby implied, would involve
a system of planes in which the C.P. never moves from its
coincidence with the C.G. for any angle of incidence within
the limits needed to cover the conditions of practical
flight.
A flat plate slightly inclined to the direction of its relative
motion has its C.P. situated towards the leading edge.
When the angle is increased, the C.P. retreats, and vice
versa. It follows, therefore, that the ballasted flat plate
would not satisfy the conditions implied by longitudinal
67
68 AVIATION
stability in the absolute sense. It has, nevertheless, a
form of stability of the weathercock kind that may very
well be suited to the purpose of practical flight.
Indeed, preceding descriptions of elementary experi-
ments with this simple model have sufficed to show that
as a system its power of recovering balance is excellent.
Moreover, in the remarks in a former chapter relating to
absolute lateral stability by means of negative wing tips, the
existence of weathercock longitudinal stability was laid
down as part of the hypothesis. It is, therefore, to a con-
sideration of the qualities of modern aeroplanes in relation
to this principle that the present chapter is devoted.
In the first place, modern aeroplanes use wings of single
camber, that is to say, wings in which the surface is wholly
concave to the chord, and the phenomena associated there-
with are diametrically opposite to the qualities displayed
by the ballasted flat plate. For instance, when the angle
is very fine indeed, the C.P. may be nearer to the trailing
edge than to the leading edge. As the angle is increased
the C.P. moves forward, but when a certain critical angle is
reached, the C.P. begins to retreat. Finally it coincides
with the centre of the surface when the wing stands upright
against the wind.
In flight, it is only with the finer angles, those below the
critical angle, that the aeroplane designer is concerned ;
and the essential point of importance that needs con-
stantly to be borne in mind is that the cambered wing of
single curvature is inherently unstable longitudinally.
Thus, if the C.P. moves forwards from the position in
which the aeroplane is in equilibrium, the tendency is to
tilt the head upwards, which will, of course, cause an
increase in the angle of incidence to the line of motion.
But, with a cambered wing of single curvature, an advance
in the C.P. can only be itself brought about by a preliminary
increase in the angle of incidence. Consequently, the'
nature of the movement is such as to augment the initial dis-
turbance.
With a flat plate, on the contrary, a disturbance tending
to increase the angle of incidence would tend to cause the
LONGITUDINAL STABILITY 69
C.P. to retreat, which would be a movement in opposition
to the disturbance and so one making for stability.
By fitting the cambered wing of single curvature with a
tail carrying a lighter load per square foot, the system as a
whole may be made to possess the characteristics of a flat
plate in respect to the travel of the C.P. with changes of
angle.
A tail set at a lesser angle of incidence than the main
planes introduces what is known as the longitudinal dihedral
angle, which may be illustrated diagrammatically thus . . ./
The tail member, if a flat plate, is normally neutral. When
it rises, the wind strikes its top surface and blows it back
again ; vice versa when it tends to fall. The principle
presents, in short, an example of weathercock stability.
On some machines, the tail planes are cambered like the
wings and help to support the weight in flight. The angle
of incidence of the tail is less than that of the wings, how-
ever, and the principle above described applies equally to
such cases.
The practical realization of the principle of the fore-and-
aft dihedral depends on the leading plane of an aeroplane
having a heavier loading (pounds per square foot) than the
tail plane. In the case of a tail-first type of machine, the
main planes occupy the position of a tail and must be less
heavily loaded than the stabilizing plane in front. In the
case of an ordinary aeroplane, the main planes being in
front, must be more heavily loaded than the tail.
The distribution of the weight of the machine is such that
the aeroplane is balanced fore and aft in its normal flying
attitude. If the attitude of the machine changes by a small
amount, so that the angle between its axis and the relative
wind is, say, two degrees less than formerly, then both the
main planes and the tail plane will have suffered an equal
diminution in their angles of incidence.
Assuming that the effect of this diminution is an equal
absolute loss of lift per square foot on both planes, then the
proportionate loss is less on the leading plane, because it has
the higher initial loading. For example, if its initial load-
ing is 5 Ib. per sq. ft. and it loses lib. per sq. ft., the
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reduction is 20%; if the tail plane initially carried 3 Ib.
per sq. ft. the loss is 33 \°/Q. The consequence of this differ-
ence is the creation of a couple tending to restore the
normal attitude in flight.
When the main planes are very lightly loaded, there is
greater latitude for the design of a stabilizing plane that is
to go in front. Here it must be more heavily loaded than
in the rear, where it would be less heavily loaded than the
main planes. This argument is sometimes advanced in
favour of the tail-first type of aeroplane. In principle, its
stabilizing action is, as has been shown, of the same
weathercock kind in both cases.
Weathercock stability results in the maintenance of
equilibrium in respect to the trend of the relative wind :
that is to say, longitudinal stability of the weathercock
order tends to maintain a constant angle of incidence
under all conditions. Inasmuch as a constant angle of
incidence requires a constant relative speed, the longi-
tudinal dihedral may be regarded as an automatic speed
regulator. As such, it draws attention to the significance of
speed as a factor in maintaining longitudinal stability.
If a real wind gives to the relative wind an upward trend,
weathercock longitudinal stability tends to make the
machine raise its tail until it is again neutral to the stream.
Similarly, if the path is one of descent in calm air towards
the earth, the tail rises into line with the direction of motion.
On the contrary, if the machine is climbing, the obliquely
upward path tends to put the tail on a lower level than
the head. As seen by a spectator on the ground, weather-
cock stability thus has the quality of making the machine
seem to " look where it is going." Yachtsmen may see
some connection between the longitudinal dihedral on an
aeroplane and the use of a jib-sail on a boat.
Also, tending to keep the angle of incidence unchanged,
it tends to limit the horizontal flight speed to a fixed velocity.
If, with a given angle, the speed is increased by increasing
the power output from the engine, the lift will exceed the
weight and the machine will climb. Conversely, if the
relative speed is decreased by closing the engine throttle,
LONGITUDINAL STABILITY 71
the machine will descend. It is of fundamental importance
to bear in mind that any raising of the machine to a higher
level in space involves the expenditure of power over and
above that necessary for support in horizontal flight.
Whether possessed of longitudinal stability or not,
therefore, a machine that is to be made to climb must
expend more power in the operation, for it is impossible
to continue to steer the machine upwards by any system
of control unless the manoeuvre is accompanied by an
increase in the power output.
Conversely, so long as the power output is sufficient to
support horizontal flight, the machine that is longitudinally
stable in the weathercock sense will not descend. On such
a machine, steering from one altitude to another would,
therefore, be accomplished by manipulating the throttle
of the engine. This point in the argument has an especial
interest in so far as some engines have not been noted for
their susceptibility to throttle control.
Weathercock equilibrium not being stability in the
absolute sense is liable to oscillation, and the presence of
some suitable organ under the pilot's control naturally
suggests itself as a desirable adjunct. It is, in fact, a feature
of all modern aeroplanes, and it is called the elevator.
Ordinarily, the elevator is a hinged flap forming an ex-
tension of the fixed tail plane. Sometimes it is a separate
member carried in front of the main planes. The name is
apt to be misleading in so far as it may give rise to an
impression that the elevator itself possesses some quality
that enables it to lift the aeroplane to a higher level in
space. It is for this reason that emphasis was laid just now
on the need for bearing in mind that an increase in the
engine power output is an essential to all continued climbing
operations. Momentary " jumps " may be accomplished
by using the elevator, but it is at the expense of the energy
stored in the machine's own mass and motion, and so
inevitably reduces the relative speed.
Originally the elevator was often called the horizontal
rudder, a term that was not only open to criticism on the
same score as is the word " elevator," but was also a word that
72 AVIATION
gave rise to much confusion as to which of the two rudders
was implied. The elevator, as a physical object, consists
of a horizontal plate, but its field of operation is vertical.
On the other hand, the ordinary steering rudder is a vertical
plate controlling horizontal movements of the machine.
The use of the term "elevator" has, therefore, at least, the
merit of avoiding this confusion.
As an elevator is fitted to all modern machines it is neces-
sary to consider the extent to which it may conceivably be
used for purposes beyond the scope of its initial duty, which
is to enable the pilot to damp out the oscillations of weather-
cock longitudinal stability.
In the first place, it is necessary to observe that as the
elevator is normally neutral, the initial effect of giving it
an angle of incidence is to alter the centre of pressure in
the system. If the elevator forms an extension of the tail,
the effect of depressing it is temporarily to increase the
lift under the tail end of the machine, which thereupon
rises.
For a small deflection of the elevator, the tail will not
rise indefinitely, because there will come a time when the
further ascent is prevented by the now negative angle of the
fixed tail plane itself. Thus, the resetting of the elevator
angle causes a change in the longitudinal axis of the system
about which the aeroplane is stable, which in turn repre-
sents, for the case in question, a finer angle of incidence on
the part of the wings.
If the machine is to be supported in horizontal flight
with the wings thus set, it is essential that the speed should
be increased. Provided, however, that the engine has
requisite reserve power there is no fundamental objection
to the assumption. Indeed, it is on this principle that
modern aeroplanes demonstrate the quality of variable
horizontal speed with their reserve engine power
It is self-evident, however, that there must be a limit
to this practice, for the range of angles suitable for flight is
none too extensive. Moreover, the very existence of these
limitations suggests at once that there is some liability of
the elevator control being abused in practice, both through
LONGITUDINAL STABILITY 73
lack of appreciation of the consequences and through
over-confidence of the pilot in his own personal skill.
One limiting condition is reached when the speed has
been reduced to a minimum by making the angle of inci-
dence extremely large. Such a tail-down attitude is called
by the French cabre and, in the limit, the machine so situated
is said to become " stalled/'
In order to recover his normal flying speed, the pilot
must dive, and it would seem that the height needed to
obtain the requisite velocity and to flatten out into a
horizontal path again is often far more than is commonly
supposed. An experiment by Orville Wright relating to
this very point is recorded in a private letter dated
26 November, 1912, from Mr. Griffith Brewer to Mr.
Alec Ogilvie, from which I have their permission to publish
the following abstract :
" Orville has been going into the cause of a number of
accidents, where for some unexplained cause the machine
has suddenly pointed downwards and has not been corrected
before coming into contact with the ground. This type of
accident has occurred in several cases after gliding down from
a considerable height, and after being straightened out at
perhaps fifty feet from the ground, the machine is seen to
turn downwards and to continue to turn down until it
strikes the ground.
" In some cases such accidents have been attributed to
the fouling of the control wires, but in an inquest held by
the American authorities on the wreck of an army machine
the control wires were found to be intact.
' The conclusion that Orville has come to is that these
accidents are caused by the stalling of the machine, and
he has been making experiments in the air in order to
test the effect of stalling in actual practice. He went to a
height of 300 ft. and stalled the machine, and as he had
expected the machine turned slowly downward, and for a
period of at least five or six seconds after first stalling, the
elevator tail was useless and the moving of the lever had
no effect on the inclination of the machine whatever. The
machine pointed downward at a very steep angle, possibly
60 degrees, before it had gathered sufficient speed to bring
74 AVIATION
it under control. Instead of dropping 50 or 60 ft. in this
recovery, however, he dropped about 200 ft. before he could
straighten her out, and he says that he did not stall her to
the worst position possible, and he would not be surprised
if it would be necessary in some instances to have 300 ft.
clear below to enable the stalling to be corrected in time to
save a smash."
The problem is one of the greatest interest and im-
portance, but does not appear to render itself readily to a
simple solution. It is, I think, commonly supposed that
the recovery depends on the measure of control available
in the elevator, but it seems to me that there is a limiting
rate at which the velocity acquired by the head-first descent
can be changed into a horizontal direction of flight without
loss of speed. If it depended only on the elevator, then
consider the case of the early Wright biplanes which had
the elevator in front and no horizontal tail plane.
The fore-and-aft dihedral depended on the pilot's control
of the elevator angle, although it was the practice of the
constructors of the machine to provide the elevator lever
with a friction brake attachment so that it would stay
in any position that it was set. In the case of a dive,
it was within the bounds of possibility that the pilot
might exaggerate the use of the elevator to such an extent
that it might take charge and turn the machine completely
upside-down. Thus, the elevator would finally assume the
position behind the transverse axis, which should properly
be occupied by a tail. With the elevator in front, it was
thus certainly possible to turn the machine into a horizontal
attitude at any moment, while diving, but it would by no
means be equally certain that the machine would fly off
horizontally in consequence.
The other extreme limiting condition in the use of the
elevator occurs when the angle of the planes has been made
so fine that they require the utmost speed available from
the engine to obtain the necessary lift for the support of
the machine in horizontal flight. Beyond this point, the
path must of necessity be downward. In this case it would,
indeed, seem as if the danger depended primarily on the
LONGITUDINAL STABILITY 75
range of the elevator and the brusqueness with which it is
used. Thus, again consider the case of the early Wright
biplanes with the elevator in front : it was presumably
possible to turn the machine head-first downwards in an
instant, but it is evident that doing so would not all at once
obliterate the momentum of the machine in a horizontal
direction.
A bullet shot horizontally from a rifle, or a stone thrown
horizontally from the hand, begins to descend at once
under the influence of gravity, but the horizontal component
of the motion causes the path pursued to be a curve
approximately in the form of a parabola.
In the case of an aeroplane with sufficient range of
elevator control it may be assumed possible to turn the
head downwards so much as to receive air pressure on the
top side of the wings. But if this happens the machine will
tend to slow down in its horizontal motion more quickly
than the pilot, who, in consequence, will be caused to
leave his seat. It seems fairly safe to assume, therefore,
that no pilot will voluntarily use the elevator to this extent
under such circumstances.
Assuming that there is to be no top pressure on the
wings, then the path of flight is a curve depending on the
speed itself, and the height requisite to recover the hori-
zontal depends, I suspect, on the steepness of the angle of
descent to which the dive is carried.
Sufficient has been said to show that such extreme
conditions of flight are primarily due to the exaggerated
use of the elevator as an organ for acquiring variable
horizontal speed. If the normal longitudinal stability of
the system were untampered with, the machine would
neither become stalled nor would it dive of its own accord.
On the other hand, neither would it have a variable range
of horizontal speed unless means were found for altering
the area of the wings in flight, which would be a more
efficient method although one involving considerable
mechanical difficulty in its execution.
It is, indeed, the procedure followed by nature in the
design of birds, which have feathered wings that they can
76 AVIATION
extend and contract at will. Dr. Hankin, who has made
such interesting observations of the detail movements of
birds in the air, describes how the wings are half folded in
what he terms " fast flex gliding." Sparrows and other small
birds while flying fast may be observed completely to close
their wings periodically when performing what Lanchester
has termed " leaping flight." Dr. Hankin has also de-
scribed how soaring birds will dive with partially folded
wings and then suddenly extend them aloft in a transverse
dihedral so as to swing themselves into a horizontal attitude
by temporarily raising the centre of resistance above the
centre of gravity.
It must be remembered, however, that the speed in this
case is above that required for horizontal flight, and so the
flattening out can be performed with great rapidity. The
same applies to an aeroplane that has acquired an ex-
cessive speed by a dive from a great height, the problem
being, I think, largely different from that related to the
least height in which it is possible to recover the horizontal
flight speed after being stalled. But there is just one point
that is worthy of attention in this matter, which is that
some forms of aeroplane may conceivably become locked
in a head-first attitude by disproportionately great resist-
ance of the undercarriage as compared with that of the
wings at very high speeds, and especially on steep slopes.
On such machines, it would seem desirable to have means
whereby a resistance surface might in emergency be raised
above the pilot's seat so as to introduce a turning couple
about the transverse axis of a kind that will augment the
elevator action.
Speaking of excessive speed with wings full spread raises
the question of the effect that might be produced by flexible
wing surfaces, such as are sometimes advocated. It would
be very awkward if there were any tendency on the part
of such sections to flatten excessively during a dive to such
an extent as to delay the recovery.
The presence of a fixed tail on modern machines is due,
it has been explained, to the inherent instability of the
cambered wings of single curvature. If a wing-form of
" Flight" Copyright Photos
1. Gustav Hamel making a spiral glide on a Bleriot monoplane.
2. F. P. Raynham banking on a Wright biplane.
3. Pierre Verrier in level flight on a Maurice Farman biplane.
LONGITUDINAL STABILITY 77
adequate lift -resistance ratio were available that also was
in itself stable in longitudinal equilibrium, there would
theoretically be less need for the tail. From the latest
research of Eiffel, who has been investigating the qualities
of the reflexed wing, in which the trailing edge curls up-
wards, it would appear that longitudinal stability is poten-
tially available in such a form. Mr. W. R. Turnbull also
had this section under observation in his laboratory at
Rothesay, Canada, as long ago as 1905, and recorded the
same fact.
Other very interesting experiments on this aspect of the
subject were made by Mr. E. N. Fales at the Massachusetts
Institute of Technology in 1912, and the results draw
special attention to the importance of the position of and
magnitude of the maximum camber. From the article con-
tributed by Mr. Fales to Engineering of 28 June, 1912, it
appears that a flat-bottomed wing having a maximum
camber of 0*125 situated 0-145 of the chord from the leading
edge had a travel of the C.P. that was in the direction for
inherent stability between the angles of 2° and 10° incidence.
Other similar wing sections, but with different maximum
cambers, were found to possess natural longitudinal stability
for a small range of angles in the flight region, but the
example quoted seems to be the best of the series.
The importance of these tests lies, of course, in the fact
that the stable portion of the range covers angles of in-
cidence commonly used in flight.
If a wing section of some such form as this proved to be
reasonably good from an aerodynamic standpoint, it would
potentially serve as a means of eliminating the long fuselage
that characterizes modern aeroplane design. In doing so
it would also relieve the machine of appreciable weight and
reduce its rotational inertia about the transverse axis. In
fine, it would promote sensitive longitudinal stability of
the weathercock order. A tail flap of sorts would pre-
sumably be necessary in its fundamental capacity of a
damping organ under the pilot's control ; if used for vary-
ing the horizontal speed by altering the angle of attack it
would still render the machine liable to be stalled.
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Attention has already been drawn to the intimate rela-
tionship between speed maintenance and longitudinal
stability, and in one form or another most devices that
have been invented as longitudinal stabilizers have been
based on the principle of regulating the velocity of the
machine. It is, therefore, important to recognize that this
function is simply and conveniently performed by the
longitudinal dihedral, which in some form or another is a
characteristic feature of all successful aeroplanes, and that
any form of hand control enabling this principle to be
neutralized must inevitably be attended with risks to any
pilot who is not fully appreciative of its purpose and limita-
tions.
CHAPTER VIII
PRINCIPLES OF PROPULSION
Propeller in front v. propeller behind — Two screws v. one — Military
requirements — Size and efficiency — Size and speed of flight — Rankine's
theory — Wing v. propeller — Aeroplane v. helicopter — Aero engines.
N" OTHING moves unless it is pushed, for even falling
bodies need the impetus of gravity to urge them
earthwards. Aeroplanes, therefore, must be driven
by other force than their own weight if they are to fly in-
definitely, and the instrument used for this purpose is the
propeller, which is, of course, driven by the engine.
The propeller exerts a thrust x on the machine by virtue
of the reaction derived from the draught that it creates
when it revolves. In principle it is a fan ; in blowing the
air backwards it drives the aeroplane forwards. It is per-
missible and proper to regard each blade of a propeller in
the same light as the wing of an aeroplane. Each blade
deflects air backwards as it moves ; the combined effect
of both blades operating always in the same region when the
machine is standing still produces a concentrated flow of air,
which becomes a very pronounced draught. Technically,
this draught is called the slip stream. When the aeroplane
is in flight the propeller screws itself continually into fresh
air, and maintains its thrust without creating so much
draught. That is to say, it deflects a greater mass of air
without accelerating it to such a high velocity.
In some aeroplanes, the propeller is situated in front, at
the very nose of the machine ; in others, it is placed behind
the main planes. Ordinarily there is only one propeller,
but from the first the Wright biplane was fitted with two,
and this uncommon feature is still retained in the modern
1 See Appendix on Newton's Laws of Motion.
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80 AVIATION
design of this machine. A very interesting biplane in-
corporating three propellers and two engines has also been
evolved by Messrs. Short Brothers.
The question of propeller position is one that hitherto
has mainly been governed by structural convenience . On the
conventional type of monoplane, for example, a single pro-
peller must be situated at one end of the fuselage or the
other, and consensus of opinion has elected to place it in
front. Fishes propel themselves from the tail, and propellers
on boats are also placed astern, so it is not for lack of ex-
ample that the screws of monoplanes fail to find themselves
thus situated. A propeller at the rear extremity of a mono-
plane fuselage, however, would quite obviously be an in-
convenience for several reasons. Such a machine was,
however, once built.
Considerations of equilibrium prevent the engine being
placed on the tail, while the separation of engine and pro-
peller by any considerable distance involves the use of
shafting that adds otherwise unnecessary weight. Also,
even a moderate-sized propeller measures 9 ft. in diameter,
and the clearance necessary to prevent its striking the
ground on landing would call for a more substantial under-
carriage beneath the tail than is at present necessary.
Many other considerations might be mentioned in this con-
nection, but really the only reason for drawing attention
to the matter is that the use of aeroplanes for military
purposes has given rise to much discussion out of which
there has been formed an opinion, which meets with con-
siderable support, to the effect that the propeller on any
military machine should preferably be behind the pilot and
the observer. It is apparent that a stern-driven monoplane
of the modern type, which has a long box-girder backbone,
is a design of considerable difficulty, but assuming a
departure from this type, a monoplane with its propeller
behind is not only a possibility, but already an accomplish-
ment.
If, as seems probable, the quality of high speed is
specialized in monoplane design with a view to employing
them for military purposes solely in the capacity of scouts,
PRINCIPLES OF PROPULSION 81
the inconvenience of the present position of the propeller,
regarded from the point of view of being an obstruction
to shooting with a gun, may continue to be of secondary
importance. Where the chances of evading capture may
depend on the ability to fly faster than the enemy, capacity
for speed is naturally a quality of first -class importance.
On the other hand, a machine that is designed to carry
a gun with a reasonable amount of ammunition and is ex-
pected to be able to cruise about at moderate speeds for
long periods of time, is far more likely to be a biplane than
a monoplane on account of the large wing area that would
be necessary to support the weight under such conditions.
The mere specification of the ability to carry a gun involves
the absence of any vital structure from in front of the
machine, and if the box-girder backbone continues to be
used as it now is, even in biplane construction, the removal
of the propeller to the rear of the main planes also involves
its duplication and the introduction of an intermediate
transmission between the engine and the two screws.
The question as to whether a gun is or is not necessary
on an aeroplane for military purposes is one that will prob-
ably have to find its final solution in war, but from hearing
the subject discussed among army officers I am left with the
impression that the aeroplane pilot need fear but little from
any land artillery. This may not, in fact, prove to be the case,
but I have heard several artillery officers express the opinion
that it would be almost impossible to hit an aeroplane with
any sort of weapon at present in use. If such is the case,
then it is apparent that aeroplanes must be fought in the
air, and that in addition to the high-speed scouts it will
also be necessary for armies to possess a squadron of aerial
destroyers.
For relatively slow speeds and the efficient utilization of
high power, two propellers are not only advantageous but
may prove necessary, for there is a limit to the diameter of
a single screw that conveniently can be employed on a
machine of even large size. At any rate, the problem of
propulsion in its broader aspect resolves itself into laying
hold of as much air as possible in a given time. High flight
6
82 AVIATION
speeds facilitate this to an extent that renders comparatively
small propellers efficient, but when the necessary volume
of air is not brought under the action of the propeller blade
by the high velocity of the machine itself, the only efficient
alternative is to increase the effective diameter, for it is
an extremely wasteful process to augment the thrust by
accelerating the velocity of the slip stream.
This procedure applied to a single propeller is limited by
considerations such as the ground clearance afforded by a
reasonable height of undercarriage when the machine is a
monoplane, and also to some extent by structural difficulties
in the propeller itself. A single propeller of about 12 ft.
in diameter is, however, successfully used in the Cody bi-
plane.
If the choice of a small-diameter propeller forms an arbi-
trary detail in the design of a slow-speed machine, the use
of twin screws is indicated as the proper course to pursue for
efficiency. The thrust that is available from a propeller
depends on the mass of air dealt with in a given time and
on the acceleration imparted thereto.
A fan standing stationary experiences a thrust due to the
reaction of the draught that it creates, and its energy is
entirely utilized in creating that draught. On an aeroplane,
the purpose of the propeller is to move the machine, and
the power lost in the propeller draught, which is commonly
called the slip stream, is only so much wasted energy.
It is necessary to create a draught in order to experience
any thrust at all from a propeller, but while the lost power
is proportional to the mass of the air in motion, it is also
proportional to the square of the slip-stream velocity.
Any increase in the speed of the propeller draught is thus
comparatively wasteful, but any increase in the speed of
the machine, which would obviously bring a greater mass
of air under the action of the propeller in a given time,
is obviously a move towards efficiency. There is, therefore,
an elementary relationship between diameter and speed of
flight, thrust, and efficiency.
If the same thrust is required at a slower speed of flight,
it can only be obtained by a relatively higher velocity in
PRINCIPLES OF PROPULSION 83
the slip stream or by increasing the propeller diameter ;
the latter is potentially the more efficient method.
It was Rankine who first clearly enunciated the true
theory of propulsion in fluids, and the opening paragraph
of the classic paper that he read at a meeting of the Insti-
tution of Naval Architects in 1865 was as follows :—
" Every propelling instrument, whether a paddle, a screw,
or a pump, drives a ship by means of the forward reaction
of the current of water which it sends backwards. That
reaction is transmitted by the propelling instrument to the
ship, and when the ship moves uniformly it is equal and
opposite to her resistance."
Before Rankine 's time, apparently, theory assumed the
propulsive effort derived from a propeller to be the equiva-
lent of the resistance that the instrument itself would ex-
perience if dragged inertly through the water. In fine, it
assumed that the mass accelerated by the instrument in
its capacity of propeller was only equal to the mass that it
was capable of bringing to rest as an obstruction. In
reality there is an immense discrepancy between the forces
in the two cases, and it is very much in favour of the pro-
peller. Theory thus, for once in a while, provided an under-
estimate instead of an overestimate of the limiting case.
If for water we substitute air, Rankine 's theory sums up
the case of the aeroplane with equal conciseness. It serves
no useful purpose, however, to consider the paddle, for
the flapping wing is the only form in which it would be likely
to exist, and such a mode of propulsion on an aeroplane
would involve considerable mechanical difficulty in its
execution.
There are two equally important points of view from
which to regard a propeller ; one already mentioned concerns
the relationship between disc area (area swept out by the
blade in rotation) and speed. The other is the analogy
between the blade of the propeller and the wing of an aero-
plane. The blade of a propeller is an aeroplane in principle,
but its flight path is a helix, and so the shape of the blade
varies from shoulder to tip. In this respect only does it, in
84 AVIATION
principle, differ from the wing of an aeroplane, which is
designed to fly straight. The design of a good propeller is,
however, a matter requiring special experience, as well as
an appreciation of theory, and, like many another important
subject that has been mentioned, its detail discussion would
be outside the scope of this book.
What, however, it is within the scope of these pages to
emphasize is that there is no difference in principle between
the means whereby a propeller exerts its horizontal thrust
and those whereby an aeroplane wing exerts its vertical lift.
Both forces are reactions due to the same fundamental
cause, which is the continuous acceleration of fluid mass.
A bird's wing is aeroplane and propeller combined, its
flapping motion relative to the bird's body giving the pro-
pulsive effort, while its mere presence as an extended surface
in motion suffices for the aerodynamic support. Birds
frequently glide long distances on outstretched rigid wings,
in which case these organs of flight are no longer propellers.
Two advantages of the flapping wing over the propeller
are its large area and more convenient position. Its most
serious drawback as a piece of mechanism would be the
structural complication of having moving parts in a vital
place and the fundamental objection to reciprocating
motion in engineering generally. Nature is limited to
reciprocating motion because arteries of necessity cross
the joint.
While discussing propellers a word may well be said on
the subject of the use that it is sometimes proposed should
be made of propellers mounted on vertical shafts so as to lift
the machine directly into the air. Several helicopters, as
they are called, have been built at one time or another, but
none has been successful, nor have I any authentic record
of any such device remaining air-borne for any appreciable
length of time. It appears to me that those who profess to
believe in the helicopter as a possible flying machine tend
rather to ignore, as did the would-be pioneers of the aero-
plane in the olden days, the fact that the troubles may be
expected to begin from the moment that they first succeed
in getting the machine itself aloft. There is no reason that
r. The four-cylinder British-built Green engine.
3. The nine-cylinder Anzani ; a stationary radial
engine of 100 h.p.
2. The three-cylinder Anzani.
' Flight " Copyright Photos
4. The nine-cylinder water-cooled Canton-Unne
radial type engine.
PRINCIPLES OF PROPULSION 85
I can see why such an apparatus should be easier to fly, i.e.
control in respect to stability and direction, than is an
aeroplane.
In so far as the helicopter is supposed to represent a
machine capable of hovering over a fixed point, the argu-
ment takes on a special aspect that naturally introduces
the airship into -the comparison as an alternative, and
possibly preferable, means of performing the same purpose.
The aeroplane accomplishes a journey while supporting itself
in the air, and in principle it may be said that the journey
is merely incidental to this mode of support. If the purpose
of flying were to stand still in space, the aeroplane might
well be criticized for its limitations on this score. On the
other hand, if the journey is useful, then the aeroplane is
undoubtedly the more economical machine, and even if the
journey itself is of no consequence, it may equally be shown
that this mode of flight offers better prospects of economy
in the utilization of power for the purposes of support than
does the helicopter.
From what has been said on the subject of propellers it
will be apparent that the " aerial umbrella " must be of
very large diameter in proportion to the weight supported if
it is not to be unnecessarily wasteful of power.
It is no part of the purpose of this book to deal fully with
the mechanism of aeroplane engines, but it would neverthe-
less seem proper in an introduction to the subject at large
to say something with reference to the action of so important
a member of the aeroplane's anatomy, and the chapter on
the principles of propulsion seems the best place for this
purpose.
It must always be realized that the evolution of the
successful aeroplane had of necessity to await the develop-
ment of a satisfactory engine. Long, long ago, when engines
were unknown, man had no other thought than that he
would have to fly by his own muscular effort if he ever flew
at all. When the steam engine was introduced, Sir George
Cayley was at pains to calculate how nearly plausible was
the idea of self-propelled flight with the prime movers then
at hand. What really made the aeroplane possible, however,
86 AVIATION
was the motor-car. The introduction and development of
the self-propelled vehicle perfected the high-speed internal
combustion engine to a point at which it could be adapted
to the requirements of aeroplane flight.
While it is true to say that the automobile was the fore-
runner of the aeroplane in this respect, it would hardly be
accurate to suggest that all the would-be flyer had to do was
to take the engine out of his motor-car and put it on board
an aeroplane in order to be able to fly. More than one
early pioneer tried, in fact, to do so, but the result was not
such as one might describe as an unqualified success.
When the Wrights had developed their glider to a point
at which they considered themselves justified in building
a power-driven aeroplane, they were at a loss to find a
satisfactory engine for their purpose, so with characteristic
enterprise they set to work to design and construct one for
themselves, and it is only fair to say that all the really
successful aeroplane engines have been specially designed
in the first instance for their particular work.
This, however, does not affect the principle of their
operation, for the petrol engine that drives the aeroplane
works in precisely the same way as the petrol engine that
drives the motor-car. The difference is one of construction,
mainly in respect to the relative disposition of parts with
the object of saving weight. It is very important that the
aeroplane engine should be as light as possible for the power
that it develops, which object has led designers to contrive
various means by which the maximum use is made of a
minimum amount of material. Thus, for example, in the
famous Gnome rotary engine, the successful working of
which at one time did .more than any other single thing to
develop flying, the cylinders are placed radially round the
crank chamber, which much shortens the overall length of
the engine. The cylinders and casing of the motor are
caused to revolve instead of the shaft, and being the heavier
part they save the weight of a fly-wheel. In its principles of
operation, however, the Gnome engine works just like any
other engine. A note on this subject appears in the Appendix.
The best -known British-built engine that is at the present
PRINCIPLES OF PROPULSION 87
time most nearly allied to motor-car practice in its design is
the Green, which has upright cylinders in line. In detail
construction, one of its most pronounced features is the use
of copper water-jackets instead of jackets cast integrally
with the cylinders themselves as is common practice with
engines built for use on motor-cars.
Many engines built for aeroplane work are air-cooled,
that is to say they have radiating fins outside their cylinders
and depend on the relative wind to prevent their cylinder
walls and valves from becoming overhot. An interesting
novelty produced by the Wolseley Co. at the Aero Show of
1913 was an engine in which the exhaust valves only were
water-cooled. Many considerations, which it would be out-
side the scope of this book to discuss, enter into the question
of air versus water-cooling. There is, for example, the
question of lubrication and also the question of fuel economy,
which raises in its turn the question of compression pressure.
Other things being equal, a high compression pressure prior
to explosion tends towards economy in fuel consumption
and to a high power output from a given size of cylinder.
Most engines that have been designed for aeroplane use
have differed from typical motor-car practice in having
their cylinders arranged in two rows set at an angle to each
other ; such motors are generally referred to as belonging
to the V type. It will be understood that a multiplicity of
cylinders is necessary in order to smooth over the inter-
mittent operation of each cylinder separately. The cranks
on the crankshaft are set at suitable angles, so that the ex-
plosions in the different cylinders occur as nearly as possible
at equal intervals of time. When an engine has four
cylinders in line an explosion occurs once every half
revolution of the crankshaft.
One of the most important considerations affecting the
practical success of an aeroplane engine, from the stand-
point of its popularity with pilots, is absence of vibration.
In this connection, those who advocate ordinary four-
cylinder vertical engines with high compression often, I
think, forget the standard of smoothness to which pilots
have from the first been accustomed in the low-compression
88 AVIATION
Gnome engines, which have seven or even fourteen cylinders
contributing to an even-turning moment. Moreover, an
engine on an aeroplane occupies a somewhat different
position from that of the prime mover of a motor-car, and it
is such as to exaggerate rather than diminish the effect of
irregular operation.
CHAPTER IX
CONCERNING RESISTANCE
Wing resistance and body resistance — Streamline flow — Relative im-
portance of the head and the tail of a body — Fair-shaped struts — The
gain in lift due to reduction or resistance — Surface friction.
SUBMARINES, torpedoes and fishes have this much
in common, that their bodies offer the least resistance
to motion through the water that is compatible with
their primary purpose of enclosing a variety of vital parts.
If man found it as uncomfortable to remain exposed at high
speeds in the atmosphere as he does to being submerged
in the sea, aeroplanes would have had bird-like bodies from
the first. On the whole, it is fortunate, however, that
pioneer constructors did not have this further necessity
added to the numerous difficulties that they have had to
surmount.
It is a reasonable presumption, nevertheless, that the
bird is the ideal flying form. Its body, one may suppose, is
the proper shape for low resistance in air, its wings are
devoid of struts and wires, its tail is without rigging and its
landing chassis, which consists of a pair of delicate legs,
ordinarily folds away when in flight.
Above all, Nature's wonderful gift for making a good
mechanical job of joints for oscillating motion enables the
bird to use its wings for propulsion by simply flapping them.
This is an economy indeed, for not only does it make use
of the whole of the supporting area for propulsive purposes,
but it avoids the extreme inconvenience of an object like a
propeller, which makes it necessary to hold the body of an
aeroplane at a great height above the ground. Indeed, the
mere presence of the propeller in the design of an aeroplane
involves a departure from natural lines that brings much
89
90 AVIATION
difficulty in its train. There is small prospect of successful
artificial flapping flight, however, so it is necessary to make
the best of the situation.
The limitations in propulsion, which have to some extent
been discussed in the preceding chapter, render it all the
more important to be chary of introducing unnecessary
resistance. The resistance to flight is preferably considered
as consisting of two separate but equally essential parts.
One part is the resistance of the wings pure and simple ; the
other part is the resistance of the body and of the super-
structure by which the wings are attached to the body.
There is very good reason for so dividing the study, for
while the size of the wings depends on the speed at which
they are intended to fly, the size of the body depends only
on what it has to carry, which, for the sake of comparison,
may be supposed to remain a constant quantity.
In the chapter devoted to the cambered wing, some
detailed consideration is given to its resistance and lift.
There is, for any particular section at a given angle of
incidence, a fixed relationship between these two factors,
and the relationship is independent of speed. For a given
weight to be supported at a given speed there is thus a certain
wing area that will satisfy the conditions for a given expendi-
ture of power.
It is modern practice, however, to aim at a wide range
of horizontal speed, and so the wing is required to support
its load at a variety of angles of incidence which in them-
selves correspond to different ratios of lift to resistance.
Thus, suppose a wing is used that has a best ratio of lift to
resistance of 12 J to i at, say, 4 degrees angle of incidence.
When flying very fast, the angle of incidence will be finer,
and when flying slowly it will be more coarse. At each end of
the range we may suppose, for the sake of example, that
the resistance is one-tenth of the load. For any given wing
section to be used, tests such as are referred to in the chapter
above mentioned will enable a chart to be drawn showing
the wing resistance for any speed throughout the range.
In this chapter, therefore, it remains only to consider the
resistance of the body and of the superstructure generally.
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92 AVIATION
Moreover, as totally enclosed bodies are not yet commonly
in vogue it is the superstructure that more particularly calls
for attention, although the principles underlying low
resistance in the one will apply equally to a design for low
resistance in the other. In the main, the superstructure
resolves itself into a study of the resistances of struts and
wires.
When a solid object is a partial obstruction to a fluid
stream, the stream divides at some point in front of the
obstacle and passes around it in a series of well-defined lines
that ultimately close together again at some point behind
the obstacle. By suitably colouring the fluid, these stream-
lines, as they are called, can be rendered visible. They show
clearly and distinctly on a time-exposed photograph, which
indicates that the direction of motion of the fluid particles
at any fixed point remains constant.
In some cases these streamlines conform to the profile
of the obstruction itself for the greater part of its length :
such objects are then said to be of fair shape or good stream-
line form. They offer the least possible resistance to motion
in the fluid, having regard, of course, to the size of the
obstruction.
Obstructions that are not of streamline form give rise to
surfaces of discontinuity. The streamlines in the fluid
diverge from contact with the walls of the object and
enclose a region of turbulence between themselves and the
solid wall. Such a pocket of 'eddies and dead water always
exists immediately behind the obstacle, and being a place
of negative pressure (suction) it exerts a drag on the object
over and above the frictional resistance of the fluid in contact
with its sides. Shapes that give rise to excessive regions
of turbulence thus experience a disproportionately high
resistance to flight.
It is by no means easy to specify off-hand a profile for
a good streamline form, and it is equally difficult to select at
sight from a number of shapes those that are likely to prove
of least resistance when tested. The problem of choosing
the best section for aeroplane struts and the like is still
further complicated by the need to consider weight and
" Flight" Copyright Photos
1. The loo-h.p. six-cylinder two-stroke N.E.C. engine birlt towards the latter part
of 1912. The 5o-h.p. four-c.. Under model has been used successfully on Alec Ogilvie's
Wright biplane.
2. A Wolseley eight-cylinder V type engine introduced in 1913. The cylinders are
air-cooled, but the exhaust valves are water-cooled.
3. The twelve-cylinder V type air-cooled Renault engine with fan attachment for
cooling the cylinders. The model of this make most in use in England during 1912
was the eight-cylinder yo-h.p.
CONCERNING RESISTANCE 93
strength, which is, of course, the basis of all design intended
for structural purposes.
That the subject is of first -class importance is apparent
from many points of view. In the first place, it must be
borne in mind that every pound saved in resistance of the
superstructure means an increase of six pounds or more in
carrying capacity of the machine, and vice versa. This
statement is based on the fact that modern aeroplanes
experience an inclusive resistance to flight of one-sixth of
their weight or thereabouts. The power available for the
purposes of comparison is, of course, assumed to be constant,
and it follows that if one of two similar machines has its
head resistance diminished by, say, 20 Ib. it can in principle
carry 120 Ib. more useful load inside its body, where the
presence of the extra weight will not give rise to other
resistance than an extra load on the wings. If, actually,
the added weight were taken solely in the wings the advan-
tage would be .even greater than this, for the wings, without
their rigging, ordinarily offer a resistance of less than one-
tenth the weight that they carry.
It is clear, therefore, that a reduction in head resistance
is worth attaining ; the question arises, however, whether
the amount to be saved is an appreciable quantity. To
answer this question in the affirmative it suffices to record
the result of tests made on strut sections at the National
Physical Laboratory, the most complete series of which thus
far completed are those that were made for Mr. Alec Ogilvie
and presented by him to the Aeronautical Society in order
that they might be published for the benefit of those
interested in aeroplane construction.
This series included a wide range of shapes, numbering
57 in all. Each was most carefully made and was exactly
1 in. wide at its maximum beam. They were all tested at a
uniform speed of 20 miles per hour, and the resistances were
then calculated on a basis of 100 ft. of strut at 41 miles per
hour.
The section of greatest resistance was a rectangle of
2 to i ratio, which had a resistance of 46-4 Ib. per 100 ft. at
41 miles per hour. The next highest resistance was a
94 AVIATION
circular section, which represented 36-4 Ib. per 100 ft. at
41 miles per hour. From these two tests alone it is clear
that the circle and the rectangle are to be studiously avoided,
for a rectangle of 2| to i ratio suitably whittled away into
a fair shape had its resistance reduced to 5-7 Ib. !
The high resistance of the circular section draws special
attention to the disproportionate resistance of single
wires, which are also of circular shape. It should be worth
while arranging wires in pairs one behind the other and
carefully binding them with tape into a fair shape, for
although this artifice may not give the least resistance
possible there is good reason to regard it as a probable
improvement on the single wire alone. In any case, the
duplication of vital wires is dictated on the score of safety.
From what has been said about streamlines and the flow
of a fluid round an obstacle it will be recognized that the tail
end of the section is fundamentally more important than
its head. The blunt edge should always be in front when
cutting through fluids.
Any sort of entry will necessarily suffice to divide the
stream, and it is not difficult to devise a reasonably good
shape. Aft of the maximum beam, however, the tail must
taper gradually. The feature most to be avoided is any
sudden change in the curvature. There should be a gradual
joining of the head to the body and a gradual falling away
of the body into the tail. When the object is long compared
with its diameter, the sides may be parallel.
If a shape is less than, say, four diameters long, it seems
preferable to use flat tips rather than introduce sharp
changes of curvature in the sides for the sake of forming a
sharp point fore and aft.
From an investigation of the streamline flow illustrated
by various examples in the Technical Report of the Advisory
Committee, it appears that the convergence of the stream
at the extremity of the tail is not unaccompanied by
turbulence even with the best forms. It would seem, there-
fore, that the very tip of the tail may in most cases be cut
off with advantage, for its presence adds weight without
improving the flow.
CONCERNING RESISTANCE 95
A theoretical streamline form properly experiences only
frictional resistance, but such perfection is not attained in
practice. It is interesting, however, to consider the nature
of surface friction, at least to the extent of recognizing
that in one part it consists in cutting through the viscous
cohesion of the fluid particles and in another to the spin-
ning of those particles as if they were rolling against the
surface of the body with which they are in contact. If
the friction were solely of the first kind it would increase
directly as the speed ; if solely of the second kind it would
increase directly as the square of the speed, as does the
wind pressure on the face of a flat plate. Being partly of
one kind and partly of the other, its rate of increase is, for
ordinary velocities, represented by some power of the speed
that is less than two.
The experimental determination of the surface friction
coefficient is less simple than it might appear, for there is
considerable difficulty in eliminating effects that are not
due to friction proper. To Dr. Zahm in America is due the
credit for conducting the first important series of experiments
on this subject. His coefficient is discussed in the Appendix.
•
CHAPTER X
THE CAMBERED WING
Lilienthal's research — The cambered wing compared with the flat
plate — The tangential — Advantages of uneven distribution of pressure.
MUCH has been said in preceding chapters about the
advantage of the cambered wing as compared
with a flat plate, when used as a supporting surface
for aeroplanes. The broad fact of its superiority has long
been known, but its qualities in detail still leave much to be
investigated. Much has, however, already been ascertained
by the research conducted in various laboratories, notably
by Eiffel in Paris and by the National Physical Laboratory
at Teddington, whose work in this department is under the
direction of the Advisory Committee for Aeronautics
appointed by the Government.
Lilienthal was one of the earliest investigators of the
cambered surface, and he it was who first drew attention to
one of the most important phenomena contributing to its
superiority for lifting purposes. (When the wind strikes an
inclined flat plate, the resultant pressure remains perpen-
dicular to the surface for all angles of incidence. If the
plate is upright and faces the wind, the pressure is wholly
a resistance to motion, but when the angle is less than a right
angle the pressure, which is tilted in sympathy with the
plate, may be regarded as partially lift and partially resist-
ance.
Of these two components, the upward pressure or lift
may be regarded as represented by the cosine of the angle,
while the resistance corresponds to the sine. Thus the
resistance in terms of the weight supported is represented
by the tangent of the angle ; conversely, the ratio of the lift
96
THE CAMBERED WING 97
to the resistance cannot exceed the cotangent of the angle.
Although the numerical values of lift and resistance do not
necessarily bear a constant proportion throughout the full
range of inclinations to the cosine and the sine of the angle
respectively, the cotangent limit to the lift resistance ratio
of a flat plate holds good as a law. Under actual test, the
flat plate does not show a ratio of lift to resistance that is
anywhere as much as the cotangent of the angle of inclina-
tion, owing to the frictional resistance of the air flowing over
the surface of the plate ; but it is none the less important
to recognize the cotangent as a theoretical limit to the ratio
of component pressures that might obtain if the plate were
frictionless.
It is important to recognize this limit to a flat plate,
because so doing facilitates a proper appreciation of the
significance of the qualities of the cambered wing, which
does actually demonstrate ratios of lift to resistance that
exceed in magnitude, at certain angles, the cotangent of
the angle of inclination. In fine, the cambered wing exceeds
even the theoretical limit to the lift resistance ratio of the
flat plate over one part of its useful range of angles.
When a cambered wing is tested against a flat plate for
lift and resistance, the comparison establishes three broad
conclusions beyond all doubt. Firstly, the cambered wing
exerts an appreciable lift when the chord is horizontal to
the relative wind, whereas the flat plate is neutral in this
attitude. Secondly, the absolute lift is superior to that
of the flat plate at all useful inclinations. Thirdly, the ratio
of lift to. resistance is also superior throughout the same
range.
Detailed investigation of these qualities also reveals two
further points of first-class importance. One is that the
cambered wing continues to lift upwards while inclined
downwards to the relative wind until the negative angle
of inclination is several degrees below the horizontal. The
precise angle of zero lift increases in negative value with
an increase of camber ; for wing sections in common use
it is in the order of 2 degrees. The second further point of
importance is that the resultant pressure on the surface is
7
98 AVIATION
inclined forward from the perpendicular to the chord
throughout part of the range of useful angles of inclination.
This latter feature is the most important of all the
qualities associated with the action of the cambered wing,
for the forward inclination of the resultant occurs at angles
of inclination that are of great service in flight. In a series
of sections of different cambers tested at the National
Physical Laboratory, it was found that the curves graphi-
cally illustrating the ratio of lift to resistance crossed the
curve of cotangents in the neighbourhood of 5 degrees. The
greatest extent of the forward inclination, indicated by the
presence of these curves on that side of the curve of co-
tangents, was reached for most of these sections at angles of
inclination between 10 and 12 degrees. Some of these
graphs are shown on page 307.
Although the resultant pressure is inclined forward of
the normal to the chord, it still slopes backward, of course,
from the perpendicular to the line of flight. Were it other-
wise, the wing would have less than no resistance and so be
an example of perpetual motion, which is against the laws
of Nature. It is, indeed, sufficiently paradoxical that it
should be possessed of the quality of being able to help pull
itself along, so to speak, by developing an up-wind com-
ponent force. It was this force that Lilienthal called by the
name " tangential."
As this reduction of esistance is most marked between
angles of 5 and 12 J degrees inclination, which represent the
upper range of angles used in flight, it is obviously of great
practical importance, especially when the nature of the curve
of cotangents that limits the lift resistance ratio of the flat
plate is borne in mind.
With a flat plate, at the finer angles the lift itself is feeble
and the lift resistance ratio is poor. When the lift resistance
ratio assumes its greatest magnitude, which is in the order
of 7^ under actual test, the angle of incidence is still
only 3 or 4 degrees and the lift coefficient is still too
small for practical purposes. Its value is about o-i or
thereabouts, whereas at the same angle of incidence, i.e.
between 3 and 4 degrees, the lift coefficient of a cambered
THE CAMBERED WING 99
wing section suitable for aeroplane use is more likely to be
in the order of 0-25, or 2j times as much as the flat plate.
At the same time, the lift -.resistance ratio will be nearer 12^
than 7j, so there is not only a gain in lift but also a reduc-
tion in resistance by using a cambered wing in place of a flat
plate at this angle of inclination.
But, for angles greater than 3 or 4 degrees, the advantage
of the cambered wing is still more pronounced. Although
the flat plate continues to increase its lift coefficient with
increasing angles up to about 0*5 for an angle of 12 J degrees,
the accompanying resistance increases in greater proportion,
and so the lift resistance ratio falls rapidly as is indicated by
the characteristic curve of cotangents. With cambered
wings, on the contrary, not only does the lift coefficient
increase to about 0-65 for an angle of 12 J, but the lift:
resistance curve crosses the curve of cotangents in the
neighbourhood of 5 degrees, and although the ratio there-
after falls off considerably, the rate at which it does so is
much less rapid than is the case with the flat plate. This
is due, as has been explained, to the advantageous effect of
the up-wind component, which tilts the resultant pressure
forward of the normal to the chord throughout a range of
angles extending from about 5 degrees to 12 J degrees
inclination.
These lift coefficients are absolute constants and so do
not vary with the atmospheric conditions. In order to con-
vert them into "pounds lift per square foot of wing area"
they may be multiplied by the factors on page 344. The
values thus obtained are correct only for a particular atmo-
spheric density, etc. (factor connecting lift and speed)
Beyond about 12 J degrees inclination, the cambered wings
tested at the N.P.L. decreased in lift '.resistance ratio very
rapidly and they also decreased their lift coefficients.
Obviously, the point at which this happens may well be
termed the critical angle. Its exact value depends on
the section of the wing and notably on the position of
the maximum camber. It varies considerably as between
one wing and another of different form.
None of the numerical quantities thus far quoted must
100 AVIATION
be taken as applying indiscriminately to all wing sections,
but it helps, I think, to fix ideas about general statements if
figures are given where possible.
It will be clear from the preceding explanation that the
great practical advantage of the cambered wing over the
flat plate is its wide range of useful attitudes, which extend
over several degrees of inclination where a high ratio of lift
to resistance is well maintained. In aeroplanes, where
alterations in the attitude of the machine are contrived by
the use of the elevator for the purpose of altering the angle of
incidence of the wings so that the machine may be supported
in the air at different speeds, this quality is important to
the extent of being essential. Thus, the most suitable wing
for practical purposes on modern machines is not one with a
mere peak of very high lift '.resistance ratio at some par-
ticular angle, but rather one that has a good broad top to
its characteristic curve of lift resistance ratios.
Having discussed the broader distinctions between the
cambered wing and the flat plate, it will be of interest to
consider the operation of the wing in greater detail. What
is without doubt the most important phenomenon associated
with the forces exerted by wing or a flat plate is that the
upper surface is much more effective to produce lift than the
lower surface. Variations in its camber practically govern
the characteristics of the wing section as a whole, and, in
general, the upper surface contributes about three-quarters
of the total lift.
It is, therefore, proper practice to design wing sections
with the contour of the upper surface as the starting-point
and to adjust the lower surface to suit structural con-
venience. Indeed, the lower surface might even be flat
without very seriously affecting the more important qualities
of the wing.
In models, where wing surfaces often consist of one
thickness of silk laid on an exposed frame, the frame itself
should be on the under side, where its projection is of less
consequence.
Against the lower face of the wing the air strikes by
impact, and there is a theoretical limit to the magnitude of
THE CAMBERED WING 101
the positive pressure caused thereby, which cannot have a
coefficient exceeding 0-5. This limiting value is, however,
attained at one spot only along the cross-section of the wing.
Somewhere, just under the leading edge, the relative wind
may be supposed to have its motion arrested, but elsewhere
the effect of the surface is merely to deflect the air stream.
The pressure reaction due to the downward acceleration of
the mass is thus, as a whole, much less than the limiting
value 0-5.
Actually, at about 12^ degrees angle of incidence the
positive pressure normal to the surface on the under side of
a flat plate reaches a maximum coefficient of about 0-17, and
remains constant up to about 20 degrees angle of incidence.
If the under face of the wing is concave, as is usual in modern
practice, the positive pressure may rise to higher values,
say, in the order of 0-2 for an angle of incidence of 15 degrees.
At 5 degrees angle of incidence, the coefficient of normal
pressure on the under side of a wing such as is used in flight
is probably in the order of 0-07.
The lifting effect of the upper surface is, of course,
necessarily due to the existence of a region of negative
pressure (suction) above the section.
This partial vacuum is most pronounced over the leading
edge of the wing, which ordinarily dips below the line of
flight so that the upper surface in front appears to face the
relative wind. The existence of a suction on a portion of the
wing surface that appears as if it should be subjected to direct
pressure is a paradox that is explained by the existence of a
cyclic or eddying disturbance around the leading edge of
a wing in flight. This has the effect of causing the true
relative wind to approach the wing with an upward trend.
In a wing tested at the National Physical Laboratory, a
point on the upper surface adjacent to the front edge was
found to be facing the line of flight at 20 degrees negative
angle of incidence when the wing as a whole was inclined at
about 12 \ degrees positive angle of incidence. Had the
relative wind been parallel to the line of flight at the point
under observation, there would obviously have been a local
down pressure due to the 20 degrees negative angle of
102 AVIATION
inclination of the surface at that point. In actual fact,
however, there was a strong local suction having a lift
coefficient of 1*5. It was apparent, therefore, that although
the local surface faced the line of flight, it was, in fact, in the
lee of the local relative wind, owing to the upward trend of
the relative wind when approaching the leading edge.
Similarly, a corresponding point on the lower surface,
which was apparently shielded from the line of flight by the
leading edge of the wing itself, was found to be located in a
region of positive pressure having a lift coefficient of 0-5.
It will be observed that the lift coefficient at this point
attained to the maximum theoretical limit, but it will also
be observed that the lift due to suction on the upper surface
was three times as great. There is no theoretical limit to the
numerical magnitude of the coefficient for the suction on
the upper face.
The distribution of pressure from leading to trailing edge
is far from uniform, and to this lack of uniformity the
remarkably high lift resistance ratios of the cambered wing
are due.
From what has already been said of the conditions in the
vicinity of the leading edge, it should seem natural that
the greatest intensity of pressure and suction should occur
at that point. This is, in fact, the case whether the aerofoil
is a cambered wing or a flat plate, but whereas the flat plate
cannot possess a dipping front edge it gains nothing in
efficiency from the irregular distribution of the pressure.
The cambered wing, on the other hand, has the normal
local direction of the forces on its dipping front edge tilted
up-wind, and so the greater the local suction the greater is
the up-wind component of the lift and the more does the
wing help itself along through the air. If the pressure
distribution were uniform from leading edge to trailing
edge, the drag of the suction on the surface aft would balance
the pull of the suction on the dipping front face, and there
would be no force parallel to the chord other than the
resistance due to friction. The resultant pressure would
then be normal to the chord and, therefore, devoid of
Lilienthal's tangential up-wind component, which is the
"Flight" Copyright Dra-w ings
Diagrams illustrating1 the distribution of pressure over various wing sections in-
clined at an angle of 6 degrees incidence. The wing sections are those of Eiffel's
series, but the diagrams have been drawn in a modified form to that in which they
are presented in Eiffel's book. The shaded portion above each section indicates
suction, while the shaded portion beneath the section is pressure. The wing is sup-
ported in flight by the combined suction and pressure on its surfaces. The forward
tilt of the diagrams accompanying the cambered sections illustrates graphically the
presence of the up-wind component, which Lilienthal called the "tangential," that is
one of the causes contributing to the greater merit of the cambered wing as com-
pared with the flat plate. In the flat plate No. i it will be observed that there is no
forward tilt, consequently the ratio of lift to resistance cannot possibly exceed the co-
tangent of the angle of inclination.
104 AVIATION
making of the cambered wing from the standpoint of lift:
resistance ratio.
It is self-evident that there can be no other than a
frictional force parallel to the chord of a flat surface.
In a cambered wing, too, the uneven distribution of
pressure on the upper surface only lasts throughout a range
of angles. At the critical angle the character of the fluid
flow over the surface suddenly changes. It becomes
extremely unsteady as the angle of incidence increases from,
say, 12 J degrees to about 20 degrees, and afterwards the
distribution becomes uniform over the whole upper surface,
which thereafter demonstrates a constant coefficient of
suction in the order of 0-3.
When this happens, the up-wind component disappears
entirely and the resistance is thus increased enormously.
With this loss of high lift: resistance ratio there is also a
reduction in the lift coefficient, as has been explained.
On the lower surface, if flat, the lift coefficient ceases to
increase at about I2j degrees and tends to fall after about
20 degrees angle of incidence. In this region, i.e. from I2j
to 20 degrees, the local pressure near the trailing edge may
become negative, that is to say there may actually be a
suction downwards on this part of the wing.
When the under surface is concave and the angle of
incidence is progressively decreased from about 12 J degrees,
the local pressure will be observed to drop suddenly at a
point commencing just behind the leading edge. When the
angle is very fine, the pressure distribution is appreciably
uniform over the lower surface, which then demonstrates a
lift coefficient of about 0-25.
From the similarity between this value and the coefficient
0-3 for the upper surface at angles of incidence about 12 J
degrees, it is supposed that a pocket of dead water forms
under the lee of the dipping front edge and gradually spreads
over the whole lower surface as the angle of incidence
becomes finer. It is, at any rate, the existence of a dead-
water region on the lee side of the wing at steep angles of
incidence that causes the steady suction coefficient and its
uniform distribution over the upper surface to occur.
THE CAMBERED WING 105
Further details of the analysis of the forces on a cambered
wing appear in the Appendix.
Other questions that have been investigated at the
National Physical Laboratory include the effect of aspect
ratio on the lift coefficient and lift: resistance ratio. Aspect
ratio is the ratio of the span to the chord, and a series ranging
from 3 to i to 8 to i was tested with the following results.
The maximum lift coefficient remains practically constant in
value while occurring at finer angles with increasing aspect
ratios. The lift resistance ratio, however, increased from
io-i to 15-5 as the aspect ratio increased from 3 to 8. For
these maxima, the corresponding lift coefficients are practi-
cally constant ; hence, the effect of aspect ratio is mainly
related to a change in resistance.
By comparison, a series of flat plates with aspect ratios
ranging from 3 to i to 5 to i showed increasing maximum
lift coefficients with increasing aspect ratios, but did not
indicate any change in lift resistance ratio — a result that
is in both respects opposite to those obtained with cambered
wings.
It may be remarked that whereas the maximum ratio of
lift to resistance for a flat plate might be expected to be
about 12 to i from the known value of the coefficient of
friction, the best actual lift resistance ratio demonstrated is
less than 8 to i. The difference is presumably due to the
effect of the edges, for a real plate cannot be an infinitely
thin plane.
In the use of wings on aeroplanes it has been explained
that they are sometimes set so as to have a dihedral angle,
that is to say so that they slope upwards from shoulder to
tip. According to tests made at the N.P.L. over a range of
dihedral angles from 166 degrees to 193 degrees the lift and
resistance coefficient showed no appreciable change It
will be observed that the range of dihedral angles covers the
condition in which the tips point downwards, or rather the
wings slope downwards from shoulder to tip as well as when
they slope upwards.
A very important investigation among the series of tests
conducted at the N.P.L. is that related to the interference
106 AVIATION
of one wing with another when one wing is placed over the
other as in biplane construction. It will be understood that
in principle an aerofoil derives its upward lift from the
downward acceleration of a mass of air. The suction or
region of negative pressure over the upper surface and the
pressure region under the lower surface are incidental details
revealed by the analysis of the forces. In broad principle,
the cambered wing, like the inclined flat plate, or the sloping
roof of a house, is a deflector of the air en masse and it
derives its lift from the reaction due to the continuous
deflection of a stratum in a downward direction.1 In
flight, it continues so to accelerate downwards a certain
mass of air per second, and it is apparent that its disturbance
in the atmosphere extends upwards as well as beneath the
wing.
It has been common practice, originating with the
Wrights who made some experiments on the matter, to
make the gap between the planes of a biplane equal in height
to the chord length of the plane. It would appear,
however, from the N.P.L. test that there is an appreciable
reduction in the lift coefficient when the gap is only of this
height, the loss being in the order of 17 per cent. Even
with a gap equal to 1-6 times the chord the reduction
in lift coefficient is still as much as 10 per cent. On
the other hand, the resistances of the planes of a biplane
do not suffer the same effect. Thus, the lift resistance
ratio of the system is reduced in approximately the
same proportion as is the reduction in the lift of the planes
themselves.
There is a slight advantage amounting to about 5 per cent
both in the lift and the l.:r. ratio of a biplane system in
which the upper plane is advanced relatively to the lower
plane to a distance equal to about 0^4 of the gap. This
staggered-plane system has been employed in the con-
struction of a few machines, but mainly from the point of
view of a less restricted outlook that it affords the pilot and
passenger. There is also some reduction in the resistance of
the struts thus set obliquely in a staggered biplane. In this
1 See Appendix on Newton's Laws of Motion.
THE CAMBERED WING 107
connection it may be remarked that increasing the gap of a
biplane in order to increase its lift resistance ratio is to
some extent discounted by the increase in resistance
that will accompany the increased length and weight of
the struts.
PART II
INTRODUCTION
THUS far this book has been devoted to the prin-
ciples of flight and to the operation of aeroplanes in
general. It has also referred to some of the salient
features of various machines commonly to be seen by those
who visit aerodromes, but it has scarcely more than men-
tioned by name the men by whose ability and perseverance
these successful craft have been evolved.
Contrary to custom, I purpose concluding this attempt
at an introduction to the study of flight by a resume of the
history of its development, which ordinarily would be placed
first in such a book. My reason for so doing is that the full
interest of the work performed by those who " lived before
their time " can only be appreciated by those who under-
stand something of the reasons that militated against
success. History is fascinating indeed, but only when the
mind approaches the subject with an intelligent interest
in the details of what is afoot. Otherwise, the chrono-
logical sequence of events presents to the reader nothing
more attractive than a bare ladder in which the rungs are
all more or less alike. When the past is reviewed from the
standpoint of some little knowledge of the present, however,
each rung stands out with a well-defined individuality,
shows itself in fact to be the life's work of a pioneer.
By the same reasoning, I have thought it well to preface
the history of the subject at large by some particular account
of the work of those whose influence has been especially
pronounced, and whose accomplishments ought always to be
remembered by the present-day student. It is, therefore, to
the work of pioneers like Lilienthal, the Wrights, the Voisins
108
INTRODUCTION 109
and Henry Farman that the ensuing chapters are mainly
devoted. There is also some brief reference to the work of
Dunne and Weiss, who have devoted themselves to the study
of natural stability.
The remarkable, but comparatively little-known work of
Prof. J. J. Montgomery, who made some successful glides
in California in 1884, and whose subsequent designs of 1905
were sufficiently stable to enable the parachute jumper
Maloney to make several glides from altitudes of upwards
of 1000 ft., is referred to in Part III.
This second part of the volume contains an account of
the Military Aeroplane Trials, which serves in some measure
as a standard of performances for modern machines. An-
other chapter is devoted to some mention of the hydro-
aeroplane, as representing the latest phase of aviation, and
the section concludes with a chapter related to accidents
and the lessons they teach.
CHAPTER XI
THE WORK OF OTTO LILIENTHAL
Bird flight as the basis of aviation — The practice of gliding — Ex-
periments at Rhinow — The artificial hill — Researches on the cambered
plane — Lilienthal's tangential.
F
IIRST among those whose work stands out as being of
pre-eminent importance is Otto Lilienthal. His per-
severance in the art of gliding opened the door to the
practice of flying before engines suitable for aeroplanes were
available. Born on 24 May, 1848, at Anclam in Pomerania,
he died on 9 August, 1896, from a fall during one of his
experiments. His interest in flight developed at the early
age of thirteen, when with the aid of his brother Gustavus
he tried to make practical experiments at school. Their
initial attempts, like those of so many others, related to the
use of flapping wings. The advent of the Franco-Prussian
War in 1870, however, demanded Lilienthal's attention in
another and less pleasant direction. Before the end of
1871, nevertheless, he was again at work on his hobby of
flight.
Realizing that his past failures were largely due to an incom-
plete study of first principles, he set himself very closely to
examine the shape and resistance of birds' wings in motion
through the air, and he satisfied himself as to the unquestion-
able advantage of the cambered plane when compared with
the flat plate. He also arrived at the conclusion that the
probable explanation of the soaring flight of birds was due
to the existence of winds with an upward trend. His
observations led him to remark that such air currents had
an average upward slope of 3j degrees with the horizon.
In 1889 he published his first pamphlet, entitled Bird
Flight as a Basis of Aviation.
no
THE WORK OF OTTO LILIENTHAL 111
Two years later, in 1891, he decided that it was time to
resume his practical experiments, and for this purpose
he constructed his famous gliding apparatus. This consisted
of a pair of rigid outstretched wings formed by cambered
planes. The span from tip to tip was 23 ft., and after various
modifications the area was adjusted to 86 sq. ft. The
planes were formed by cotton twill, stretched over a
framework of willow, and varnished with a preparation of
wax. The machine weighed about 40 Ib. and had neither
a tail nor a motor.
In adopting the principle of trying to obtain some
experience in the air with the use of a motorless machine,
Lilienthal recognized the true route to the conquest of
the air, which man had been seeking for centuries without
success. Almost everyone, not even excepting Lilienthal
himself at first, had supposed that it would be necessary
either to fly by muscular exertion or by the aid of an engine.
A man's muscles are unsuitable for the purpose of flapping
wings, even supposing them to be strong enough in the first
instance, but, up to Lilienthal's time, a suitable engine had
not been forthcoming, notwithstanding the wonderful
achievements of one or two who had specialized in this
direction.
Lilienthal was able to see clearly that flight could be
achieved, within limits, without a material engine, by using
gravity as the motive power. He realized that if he were
content to fly always downhill he might obtain considerable
scope for practice in the art of aviation and it was by his
perseverance in this simple and clear-minded conception of a
practicable solution to the problem that Lilienthal did more
for the progress of flight than any man up to his time.
His first experiences were obtained by jumping off a
spring-board in his garden, with his glider arranged under
his arms. Afterwards he practised jumping off mounds in a
field between Werder and Gross-Kreutz. It was at this
place that he found the fluctuations of the wind so disturbing
that he decided to fit a tail to his glider in order to give it
more stability of direction. Hitherto, he had confined
himself to practising in a calm. The culminating point of
112 AVIATION
these experiences was the accomplishment of glides of about
80 ft. in length from a height of about 19 ft. His gliding
angle was thus a slope of i in 4.
Next year, in 1892, a still better practice ground was
found between Steglitz and Siidende, where the hills were
some 30 ft. in height. A new glider was built having an
area of 171 sq. ft. and a weight of about 53 Ib. With this,
glides were made in winds up to 16 miles per hour velocity ;
the flight speed through the air being about 33 miles per
hour. At the best, the gliding angles had a tangent of i in 8.
Once again Lilienthal decided to move his quarters, and
in the middle of 1893 transferred his apparatus to Maihohe,
which also was near Steglitz. It was here that he built his
first gliding tower, which consisted of a shed for housing
the glider. The roof was about 33 ft. above the ground, and
so afforded a sloping start for the glide. The glider used
during these experiments differed from the preceding
machines in being so made that the wings could fold up
for convenience in housing. Unfortunately, the climatic
conditions in this locality were not very suitable for such
experiments, so during the same year Lilienthal moved
over to the Rhinow Mountains, near Rathenow, where there
exists a fine range of hills some 200 ft. in height, having
slopes in every direction from 10 to 20 degrees.
As it is necessary that glides should be started head to
wind, a hill open on all sides is almost essential to continued
progress. If limited to gliding in one direction, the experi-
menter is tediously kept waiting for a favourable day. It
was at Rhinow that Lilienthal made some of his best glides
with a machine weighing about 44 Ib. The total weight in
flight was 220 Ib., with himself on board. The span was 23 ft.
and the area 150 sq. ft. With this apparatus glides of 800 ft.
were accomplished from a starting-point 100 ft. above the
ground.
It was at Rhinow that Lilienthal met with his first and,
with the exception of the last and fatal calamity, only
serious accident. He thus describes his experience in the
Aeronautical Annual, edited and published by James Means
at Boston :
THE WORK OF OTTO LILIENTHAL 113
" In my experiments made before Easter from the still
higher mountains near Rhinow, I perceived that I had to
bear with the upper part of my body a good deal towards
the back to prevent my shooting forward in the air with the
apparatus. During a gliding flight taken from a great height
this was the cause of my coming into a position with my
arms outstretched, in which the centre of gravity lay too
much to the back ; at the same time I was unable — owing
to fatigue — to draw the upper part of my body again
towards the front. As I was then sailing at about the
height of 65 ft. with a velocity of about 35 miles per hour,
the apparatus, overloaded in the rear, rose more and more,
and finally shot, by means of its vis viva, vertically upwards.
I gripped tight hold, seeing nothing but the blue sky and
little white clouds above me, and so awaited the moment
when the apparatus would capsize backwards, possibly
ending my sailing attempts for ever. Suddenly, however,
the apparatus stopped in its ascent, and, going backward
again in a downward direction, described a short circle and
steered with the rear part again upwards, owing to the
horizontal tail which had an upward slant ; then the
machine turned bottom upwards and rushed with me
vertically towards the earth from a height of about 65 ft.
With my senses quite clear, my arms and my head forward,
still holding the apparatus firmly with my hands. I felL
towards a greensward : a shock T a crash, and T 1ay witk~*hp
^
" A flesh wound at the left side of the head, caused by
my striking the frame of the apparatus, and a spraining of
the left hand, were the only bad effects of this accident.
The apparatus was, strange .to say, quite uninjured. I
myself, as well as my sailing implements, had been saved by
means of the elastic recoil-bar, which, as good luck would
have it, I had attached for the first time at the front part
of the apparatus. This recoil-bar, made of willow wood,
was broken to splinters ; it had penetrated a foot deep into
the earth, so that it could only be removed with difficulty.
" My brother, who also took part in these experiments
and had been able to get a perfect side-view of my un-
successful flight, said it had looked as if a piece of paper
had been sailing about in the air at random. In my thou-
sands of experiments this is the only fall of that kind, and
this I could have avoided if I had been more careful."
8
114 AVIATION
In 1894, that is to say the very next year, Lilienthal
decided on yet another change of head-quarters, mainly
owing to the inconvenient situation of his existing practice
ground. In order that he might have just what he required,
he had an artificial hill constructed at his place in Gross-
Lichterfelde, near Berlin. The hill was 50 ft. in height and
had a base of 230 ft. in diameter. On the top of the hill was
a roofed cavity forming a shed for the gliders. Here
Lilienthal commenced experiments with an entirely new type
of glider, this machine being a biplane of which the upper and
lower planes were, however, constructed on similar lines
to his original monoplane gliders, with which he had hitherto
been making trials, and the way in which his biplane was
evolved is thus explained in an article that he wrote specially
for the Aeronautical Annual in 1896.
" My experiments in sailing flight have accustomed me
to bring about the steering by simply changing the centre
of gravity.
" The smaller the surface extension of the apparatus is
the better control I have over it, and yet if I employ smaller
bearing surfaces in stronger winds, the results are not more
favourable. The idea therefore occurred to me to apply two
smaller surfaces, one above the other, which both have a
lifting effect when sailing through the air. Thus the same
result must follow which would be gained by a single surface
of twice the bearing capacity, but on account of its small
dimensions this apparatus obeys much better the changes
of the centre of gravity.
" Before I proceeded to construct these double sailing
machines, I made small models in paper after that system,
in order to study the free movements in the air of such
flying bodies and then to construct my apparatus on a
large scale, depending on the results thus obtained. The
very first experiments with these small models surprised me
greatly on account of the stability of their flight. It appears
as if the arrangement of having one surface over the other
had materially increased the safety and uniformity of the
flight. As a rule it is rather difficult to produce models
resembling birds, which, left to themselves, glide through
t-he air from a higher point in uniformly inclined lines. . . ,
THE WORK OF OTTO LILIENTHAL 115
I myself doubted formerly very much that an inanimate
object sailing quickly forward could be well balanced in the
air, and was all the better pleased in succeeding in this
with my little double surfaces.
" Relying on this experience, I constructed first a double
apparatus, in which each surface contains about 97 sq. ft.
I thus produced a comparatively large bearing surface of
about 194 sq. ft. with but about 18 ft. span.
" The flights undertaken with such double sailing surfaces
are distinguished by their great height. ... I often reach
positions in the air which are much higher than my starting-
point. At the climax of such a line of flight I sometimes
come to a standstill for some time, so that I am enabled
while floating to speak with the gentlemen who wish to
photograph me, regarding the best position for the photo-
graphing.
' At such times I feel plainly that I would remain floating
if I leaned a little towards one side, described a circle and
proceed with the wind. The wind itself tends to bring this
motion about, for my chief occupation in the air consists in
preventing a turn either to the right or left, and I know that
the hill from which I started lies behind and underneath
me, and that I might come into rough contact with it if I
attempted circling."
At this point Lilienthal had acquired considerable ability
in his accomplishment of gliding flight, and he decided that it
was well worth while trying to introduce the power element
into his machine. His object was, it seems, not so much
to be able to fly a greater distance in a straight line as to be
able so to control the direction of his apparatus as to take
advantage of changes in the wind, with a view to soaring
more or less indefinitely.
For this purpose, he built a light machine weighing about
88 Ib. fitted with a motor capable of developing 2j h.p. for
about 4 min. The mechanism was designed to move the
wings in such a way as to imitate the wing action of a bird,
but although the apparatus was actually constructed and
tested exact details of it do not appear to have been
published, for Lilienthal unfortunately met his death before
he had had time to develop this side of his work.
116 AVIATION,
Lilienthal thus describes, in the above-mentioned article
to the Aeronautical Annual, his reasons for wishing to fit
an engine on his machine :
" My experiments tend particularly in two directions.
On the one side I endeavour to carry my experiments in
sailing through the air with immovable wings to this extent ;
I practise the overcoming of the wind in order to penetrate,
if possible, into the secret of continued soaring flight. On
the other hand, I try to attain the dynamic flight by means
of flapping the wings, which are introduced as a simple
addition to my sailing flights. The mechanical contrivances
necessary for the latter, which can reach a certain perfection
only by gradual development, do not allow yet of my making
known any definite results. But I may state that since my
sailing flights of last summer, I am on much more intimate
terms with the wind.
" What has prevented me till now from using winds of
any strength for my sailing experiments has been the danger
of a violent fall through the air, if I should not succeed in
retaining the apparatus in those positions by which one
insures a gentle landing. The wildly rushing wind tries to
dash about the free floating body, and if the apparatus
takes up a position, if only for a short time, in which the
wind strikes the flying surfaces from above, the flying body
shoots downward like an arrow, and can be smashed to
pieces before one succeeds in attaining a more favourable
position in which the wind exercises a supporting effect.
The stronger the wind blows, the easier this danger occurs,
as the gusts of wind are so much the more irregular and
violent.
" As long as the commotion of the air is but slight, one
does not require much practice to go quite long distances
without danger. But the practice with strong winds is
interesting and instructive, because one is at times sup-
ported quite by the wind alone. The size of the apparatus,
however, unhappily limits us. We may not span the sailing
surfaces beyond a certain measure, if we do not wish to make
it impossible to manage them in gusty weather. If the
surfaces of about 150 sq. ft. do not measure more than about
23 ft. from point to point, we can eventually overcome
moderate winds of about 22 miles per hour velocity, pro-
THE WORK OF OTTO LILIENTHAL 117
vided one is well practised. With an apparatus of this size
it has happened to me that a sudden increase in the wind has
taken me way up out of the usual course of flying, and has
sometimes kept me for several seconds at one point of the
air. It has happened in such a case, that I have been lifted
vertically by a gust of wind from the top of the hill, floating
for a time above the same at a height of about 16 ft., whence
I then continued my flight, against the wind.
" Although, while making these experiments, I was
thrown about by the wind quite violently and was made to
execute quite a dance in the air in order to keep my balance,
I yet was always enabled to effect a safe landing, but still I
came to the conviction, that an increase in the size of the
wings or the utilizing of still stronger winds which would
lengthen the journey in the air, would necessitate something
being done to perfect the steering and to facilitate the
management of the apparatus. This appeared to me to be
all the more important as it is very necessary for the develop-
ment of human flight that all, who take up such experiments,
should quickly learn how to use the apparatus safely and
understand how to use the same even if the air is disturbed.^
It is in the wind that this practice becomes so exciting and
bears the character of a sport, for all the flights differ from
each other and the adroitness of the sailing-man has the
largest field for showing itself. Courage also and decision
can be here shown in a high degree."
Before Lilienthal had had time properly to develop his
power-driven machine to a degree that would have made him
feel justified in publishing particulars of his scheme he was
unfortunately cut off from further active work in this world
by a fatal accident that took place during a glide at Rhinow
on 9 August, 1896. So far as can be ascertained, Lilienthal
was then using a rather worn-out machine that was about
to be discarded. At the moment, it was being employed for
the purpose of testing the action of a new member that was
presumably an elevator.
He had intended making as long a flight as possible, and
hoped to exceed the 12 or 15 seconds duration that was
commonly the limit of his glides. Whilst at a height of some
50 ft. from the ground, however, some part of the machine
118 AVIATION
broke and the apparatus fell headlong, burying Lilienthal
beneath the debris. Lilienthal's spine was broken, and he
died within 24 hours, thereby rendering the world poorer to
an extent that is only faintly measured by his own apparent
accomplishments up to that point.
Like all the pioneers of flight, Lilienthal was generous to
his co-workers in freely publishing the results of his ex-
periences. His most notable researches are those from
which he compiled his table of lift and resistance values for
cambered planes. (The important feature of these investiga-
tions was the experimental evidence thereby provided to
the effect that a cambered plane has the direction of its
resultant pressure inclined forward of the chord throughout
a range of angles of inclination. The horizontal component,
in the line of the chord Lilienthal called the " tangential."]
It will have been evident from what has already beeir
said that Lilienthal was deeply interested in the subject of
bird flight. According to his own accounts, some of his most
interesting and instructive observations in this direction
took place at a comparatively late period of his work, when
he visited the village of Vehlin near Glowen on the Berlin-
Hamburg Railway. In this quiet little spot, storks make
their nests on the roofs of almost every cottage and afford
what is probably a unique opportunity for close and, so far
as is possible, accurate observation of soaring flight. Here
is a paragraph that Lilienthal wrote after his Easter holiday
at Vehlin :
' Three things are essential for soaring : a correct shape
of wing, the right position of wing, and a suitable wind. In
order to judge of these three factors and their changeable
effect, we have nothing but our practised eye to depend upon.
" Just how much the cross-section of the wing is arched
when the stork is resting on the wind can be determined
only by eye measurement ; similarly, the position of the
wing to the direction of the wind and to the horizon. But,
when hundreds of storks give one the opportunity to observe
the same in clear weather close at hand, what is seen is
impressed so indelibly on the mind that it enables one to
draw correct conclusions as to the existing laws.
THE WORK OP OTTO LILIENTHAL 119
" In general, one can say that when the stork flies with
wings spread horizontally and allows itself to be borne by
the wind alone, it is but seldom that a stronger gust of wind
causes the stork to draw in its wings.
' The parabolic profile of the wings has a depth which I
consider to be about one-twentieth of the breadth of the
wing. The pinions are mostly spread out, but do not lie in
one plane ; but the more they are to the front, the higher are
the points, certainly because they would otherwise hinder
one another in their bearing capacity.
" When in this position the stork passes slowly against the
wind above the observer, the head and neck are, as a rule,
stretched straight out ; but if one imagines that soaring is
possible in this position, that it causes little resistance, he
will be surprised to see a stork, sailing in this manner,
suddenly, without changing its position, lay its head back
and rattle joyously. While we human beings are striving
to find the proper shape for the wings, building theory on
theory, flying takes place in nature in a wondrously simple
way, quite as a matter of course."
CHAPTER XII
THE WORK OF WILBUR AND ORVILLE WRIGHT
The first inspiration — The introduction of wing warping — Experiments
at Kitty Hawk — Camber and the centre of pressure — Testing the glider
as a kite — The ominous wind tap — Building the engine — The successful
nights.
THE Wrights commenced their own gliding experi-
ments four years after Lilienthal's death, and
they so improved the control and design of the
aeroplane that its use became comparatively safe instead of
highly dangerous. Starting in 1900 they made experimental
flights downhill against the wind over the sand dunes on the
North Carolina coast.
These practical trials alternated with laboratory research
and lasted three years. In 1903 they designed and con-
structed a larger machine to take an engine, which also they
built in their own workshop.
On 17 December of that year they succeeded in making
four free flights, rising from level ground against the wind.
It was a triumph of systematic progress, and so thoroughly
did they continue to do their work that by the end of 1905
they had made several flights exceeding 20 miles in length,
lasting more than half an hour in duration.
So far ahead were the Wrights in the new art, that more
than two years elapsed before anyone else flew a circular
course of five-eighths of a mile. It is impossible to over-
estimate the service rendered to aviation by the Wrights'
systematic methods. They progressed in an entirely un-
known art without accident through scientific forethought
and a capacity for taking infinite pains. They attempted
no new experiment without a reason, and they passed
through no new experience without investigating its cause.
120
WILBUR AND ORVILLE WRIGHT 121
To the day of his death, which terminated an attack of
typhoid fever, on 30 May, 1912, Wilbur Wright knew more
than any man of the practical science of flight, and it was as
a scientist that the Aeronautical Society desired to honour
his memory when the Wilbur Wright Memorial Fund was
created specifically for the endowment of a scientific lecture
to be delivered annually under its aegis. Wilbur Wright was
a member of the Society and, with his brother Orville, was
recipient of its Gold Medal.
The following is Wilbur Wright's own story of how he came
to take up the study of aviation :
" My own active interest in aeronautical problems dates
back to the death of Lilienthal in 1896. The brief notice of
his death which appeared in the telegraphic news at
that time, aroused a passive interest which had existed
from my childhood, and led me to take down from the
shelves of our home library a book on Animal Mechanism,
by Prof. Marey, which I had already read several times.
From this I was led to read more modern works, and as my
brother soon became equally interested with myself, we
soon passed from the reading to the working stage.
" It seemed to us that the main reason why the problem
had remained so long unsolved was that no one had been
able to obtain any adequate practice. We figured that
Lilienthal in five years of time had spent only about five
hours in actual gliding through the air. The wonder was
not that he had done so little, but that he had accomplished
so much. It would not be considered at all safe for a bicycle
rider to attempt to ride through a crowded city street after
only five hours' practice, spread out in bits of ten seconds
each over a period of five years ; yet Lilienthal with his
brief practice was remarkably successful in meeting the
fluctuations and eddies of wind gusts."
Having made such calculations as were possible in the
light of the knowledge of the time, Wilbur Wright and his
brother Orville decided to build a glider of 200 sq. ft. area
capable of support at about 18 miles per hour, and it was
their intention to try to fly this machine in the wind on the
side of a hill as a kite with the pilot on board so that ex-
122 AVIATION
perience in riding the air might be obtained without actual
motion over the ground. This was an entirely new idea on
the subject of practising aviation and was the direct outcome
of Wilbur Wright's appreciation of the limitations that had
impeded Lilienthal's progress, rapid, nevertheless, as that
had been.
They built their first machine in 1900, but being unable
to obtain suitable material they made it only 165 sq. ft. in
area. It was a biplane constructed on the trussed bridge
principle introduced by Chanute, but differing from the
Chanute biplane in several respects. Its front main spar
formed a bluff entering edge, its planes were double surfaced
and had a special arrangement of the tie wires that enabled
them to be all tightened simultaneously by merely shorten-
ing two of them. In addition, the Wright glider introduced
certain entirely new ideas of a radical kind ; thus, for
example, the pilot was to lie prone on the lower plane in order
to reduce the body resistance, and as he would then be no
longer able conveniently to move about in order to maintain
the balance, the apparatus was equipped with an elevator
and a system of wing warping control. In any case, the
Wrights would have introduced some such system of control,
for, apart from the question of body resistance, they had
come to the conclusion that Lilienthal's method of balancing
was neither so quick nor so effective as was necessary.
A movement of the body to one side or other of the centre
of the machine, which was Lilienthal's method of balancing,
afforded only a very small restoring couple at its best. In
Wright's system the effect of warping the wings increased
with the velocity of flight and, moreover, the warp itself
had its maximum value at the tips of the wings and there-
fore possessed the greatest possible leverage over the centre
of gravity of the machine.
From the very beginning, the Wrights decided to build a
machine without a tail, for the very simple reason that they
considered such a member likely to be more bother than it
was worth. This, at any rate, was the conclusion that
they had arrived at after studying the experiences of
Lilienthal and Chanute. Their first trial with the 1900
WILBUR AND ORVILLE WRIGHT 123
machine took place at Kitty Hawk, North Carolina, in
the summer of that year. Some trials were made by
flying the glider as a kite, with the pilot on board, and the
machine was also flown alone, with the control mechanism
operated from the ground by cords.
In general, the results were satisfactory and particularly
so in respect to the system of control. But the calculations
for area and velocity appeared to be at fault inasmuch
as the machine and pilot were only supported in a wind of
about 25 miles per hour when the angle of incidence was 20
degrees instead of at the anticipated value of 3 degrees.
They also made some tests of lift and resistance, and found
that the machine would support a weight of 52 Ib. with a
pull of only 8-5 Ib., which, in conjunction with the deficiency
in total lifting power that they had observed, led them to
suppose that they might have made the camber of thJr
planes too small, as it was only about 0-045. They also
thought that the fabric of the surfaces might be too porous, as
it was not " doped."
Having made these preliminary experiments they took
the machine to a point four miles south known as the Kill
Devil Sand Hill, which has a lo-degree slope towards the
north-east. Here they made a few actual glides at flight
speeds through the wind of from 25 to 30 miles per hour.
The tangent of the gliding angle was about one in six and
they satisfied themselves that the machine was capable of
gliding at a somewhat less angle than' 9^ degrees. These
tests concluded their work for 1900 and they at once set
about building a new machine for next year.
The 1901 model had its area increased to 308 sq. ft . and the
camber of the planes increased to 0-083. It was estimated
that the machine and the pilot would be supported at 17
miles per hour with an angle of incidence of 3 degrees. In
the summer of 1901 they again went into camp, where they
were joined by E. C. Huffaker, Dr. G. A. Spratt, and, for a
period of a week, by Octave Chanute. The initial trials
with the new machine were not very satisfactory, and it was
some little while before they could make a glide at all, for
their estimated position for the centre of gravity was nearly
124 AVIATION
a foot misplaced from where the pilot ultimately had to
locate his body.
Even when a glide of some 300 feet was accomplished,
Wilbur Wright experienced the greatest difficulty in 'keeping
the machine steady, having to use the elevator in a far more
vigorous manner than on the earlier model. Once or twice
the machine tilted as Lilienthal's glider once did and lost
headway in mid-air, but on each occasion the operation of
the elevator saved the situation and brought the machine
safely to earth. On one of these occasions it had even
commenced to slide backwards in the air before it recovered
itself. These experiences the Wrights naturally considered
to be of extreme importance and to justify their contention
that the front elevator was a far safer device than the tail.
The difficulty of getting the machine to glide steadily
bothered them considerably for some time, for although
they were forced to suppose that it was due to a reversal in
the travel of the centre of pressure at small angles of
incidence, they were loath to adopt this explanation,
believing that they had already guarded against this effect.
Wilbur Wright's observations on this point were as follows :
" In deeply curved surfaces the centre of pressure at
90 degrees is near the centre of the surface, but moves
forward as the angle becomes less till a certain point is
reached varying with the depth of curvature. After this
point is passed, the centre of pressure, instead of con-
tinuing to move forward with the decreasing angle, turns
and moves rapidly towards the rear. The phenomena are
due to the fact that at small angles the wind strikes the
forward part of the surfaces on the upper side instead of
the lower, and thus this part altogether ceases to lift, instead
of being the most effective part of all as in the case of the
plane.
" Lilienthal had called attention to the danger of using
surfaces with a camber as great as one-eighth of the chord,
on account of this action on the upper side ; but he seems
never to have investigated the camber and angle at which
the phenomena entirely cease. My brother and I had never
made any original investigation of the matter, but assumed
that a camber of one-twelfth of the chord would be safe, as
WILBUR AND ORVILLE WRIGHT 125
this was the camber on which Lilienthal based his tables.
However, to be on the safe side, instead of using the arc of a
circle, we had made the camber of our machine very abrupt
at the front so as to expose the least possible area to this
downward pressure.
" While the machine was building, Messrs. Huffaker and
Spratt had suggested that we should find this reversal of
the centre of pressure, but we believed it sufficiently guarded
against. Accordingly, we were not at first disposed to
believe this reversal actually existed in our machine,
although it offered a perfect explanation of the action we
had noticed in gliding."
In order to test their theory on the reversal of the
travel of the centre of pressure they carried out some
experiments with a glider used as a kite and were able
to observe in a very marked way that the centre of
pressure did reverse its direction of travel as suggested.
Accordingly they proceeded to reduce the camber of their
planes. This change proved entirely satisfactory, the glides
being steady and the machine answering the elevator
movements perfectly. Their confidence in the machine
soon became such that they were able to glide in winds as
high as 27 miles per hour. Many further tests were also
made with the glider as a kite and particularly were these
useful in comparing estimates of the lift and drift. Incident-
ally, they served to corroborate Lilienthal's theory of the
forward inclination of the resultant pressure on cambered
planes at small angles, although they gave numerical results
at variance with Lilienthal's data. The following is Wilbur
Wright's summary of some of the tests :
' While at Kitty Hawk we spent much time in measuring
the horizontal pressure on our unloaded machine at various
angles of incidence. We found that at 13 degrees the hori-
zontal pressure was about 23 Ib. This included not only the
drift proper, or horizontal component of the pressure on the
side of the surface, but also the head resistance of the framing
as well. The weight of the machine at the time of this test
was about 108 Ib. Now, if the pressure had been normal
to the chord of the surface, the drift proper would have
126 AVIATION
been to the lift (108 Ib.) as the sine of 13 degrees is to the
cosine of 13 degrees, or —=24-6 Ib. ; but this
slightly exceeds the total pull of 23 Ib. on our scales. There-
fore, it is evident that the average pressure on the surface,
instead of being normal to the chord, was so far inclined
towards the front that all the head resistance of framing
and wires used in the construction was more than overcome.
" In a wind of 14 miles per hour, resistance is by no means
a negligible factor, so that ' tangential ' is evidently a force
of considerable value. In a higher wind which sustained
the machine at an angle of 10 degrees, the pull on the scales
was 1 8 Ib. With the pressure normal to the chord, the drift
• ~TtJ VX Qft 1
proper would have been — - — ~ — = 17 Ib., so that although
•98
the higher wind velocity must have caused an increase in
the head resistance, the tangential force still came within i Ib.
of overcoming it. After our return from Kitty Hawk we
began a series of experiments to accurately determine the
amount and direction of the pressure produced on curved
surfaces when acted upon by winds at the various angles from
zero to 90 degrees. These experiments are not yet concluded,
but in general they support Lilienthal in the claim that the
curves give pressures more favourable in amount and
direction than planes ; but we find marked differences in
the exact values, especially at angles below 10 degrees.
We were unable to obtain direct measurements of the hori-
zontal pressures of the machine with the operator on board,
but by comparing the distance travelled in gliding with the
vertical fall, it was easily calculated that at a speed of
24 miles per hour the total horizontal resistances of our
machine, when bearing the operator, amounted to 40 Ib.,
which is equivalent to about 2\ h.p."
Among other points investigated was the problem of
soaring in winds with an upward trend, and although they
considered themselves too inexpert actually to attempt
anything of this nature on their own part, they would
1 The travel of the centre of pressure made it necessary to put sand on
the front rudder to bring the centres of gravity and pressure into coinci-
dence, consequently the weight of the machine varies from 98 Ib. to 108 Ib.
in the different tests.
WILBUR AND ORVILLE WRIGHT 127
frequently make the glider soar at the end of two vertical
ropes attached to the forward spar at each extremity of the
machine. This method they found to be very useful as a
means of testing any alteration in the machine, but Wilbur
Wright drew attention to the danger of making numerical
calculations from the slope of the hill and the wind velocity
for any other conditions than those in which the ropes
attached to the machine are vertical to the horizon ; in other
words, allowances for obliquity of kite line are open to
serious error.
As the result of their experiments for 1901 they came to
the following conclusions :
" In looking over our experiments of the past two years,
with models and full-size machines, the following points
stand out with clearness :
" I. That the lifting power of a large machine, held
stationary in a wind at a small distance from the earth, is
much less than the Lilienthal table and our own experiments
would lead us to expect. When the machine is moved
through the air, as in gliding, the discrepancy seems much
less marked.
"2. That the ratio of drift to lift in well-shaped surfaces
is less at angles of incidence of 5 to 12 degrees than at an
angle of 3 degrees.
"3. That in arched surfaces the centre of pressure at
90 degrees is near the centre of the surface, but moves
slowly forward as the angle becomes less, till a critical angle,
varying with the shape and depth of the curve, is reached,
after which it moves rapidly towards the rear till the angle
of no lift is found.
" 4. That with similar conditions, large surfaces may be
controlled with not much greater difficulty than small ones,
if the control is effected by manipulation of the surfaces
themselves, rather than by a movement of the body of the
operator.
"5. That the head resistances of the framing can be
brought to a point much below that usually estimated as
necessary.
" 6. That tails, both vertical and horizontal, may with
safety be eliminated in gliding and other flying experiments.
" 7. That a horizontal position of the operator's body
128 AVIATION
may be assumed without excessive danger, and thus the
head resistance reduced to about one-fifth that of the
upright position.
"8. That a pair of superposed, or tandem surfaces, has
less lift in proportion to resistance than either surface
separately, even after making allowance for weight and head
resistance of the connections/'
In the interim between the experiments of 1901 and those
of 1902 the Wrights conducted laboratory experiments,
the results of which have not yet been made public.
Their 1902 glider was again a biplane having an area of
305 sq. ft., a span of 32 ft. and a chord of 5 ft. The elevator
had an area of 15 sq. ft. extra, and there were two vertical
tail planes carried on an outrigger at the rear measuring
6 sq. ft. in area each. Initially these tail planes were rigidly
attached to the outrigger and not used as a rudder. At a
later period, when the tail plane was reduced to half its
original value, the tail in question was pivoted to act as a
rudder.
They again took their machine out to Kill Devil Sand
Hill and again found it to have idiosyncrasies of its own that
had not been noted in either of the preceding models. This
time the machine tended to be rather unstable laterally. In
both the earlier types, the spars of the main planes were
arched slightly, and as the 1902 model had straight spars
it was supposed that the trouble might be due to this cause,
so the necessary alterations were made to reproduce the
arching. The first glide subsequent to this change was made
by Orville Wright and had an alarming result, for seeking
to balance the machine laterally the pilot neglected to pay
attention to the elevator, so that the machine tilted badly
and finally fell backwards to the ground, where it was
smashed.
Subsequent tests showed that the machine was still
unstable, and various reasons led to the tail being regarded
as the offending member. Sometimes it was found useful,
but more often than not it was considered disadvantageous.
Consequently one of the vertical planes was removed and
the remaining one mounted on pivots so that it could be
K)
o
0)
H
O
5
WILBUR AND ORVILLE WRIGHT 129
used as a rudder. With this change their troubles ended,
and they were able to set to work seriously in the gaining
of further experience in actual gliding flight. On this period
Wilbur Wright observes as follows :
" During a period of five weeks, glides were made when-
ever the weather conditions were favourable. Many days
were lost on account of rain. Still more were lost on account
of light winds. Whenever the breeze fell below 6 miles per
hour, very hard running was required to get the machine
started, and the task of carrying it back up the hill was
real labour. A relative wind of at least 18 miles per hour
was required for gliding, while to obtain a speed of 12 miles
by running required very severe exertion. Consequently,
unless the wind blew in our faces with a speed of at least
6 miles, we did not usually attempt to practice ; but when
the wind rose to 20 miles per hour, gliding was real sport,
for starting was easy, and the labour of carrying the machine
back uphill was performed by the wind.
" On the day when the wind rose to over 16 metres a
second we made more than a hundred glides with much less
physical exertion than resulted from twenty or thirty glides
on days when the wind was light. No complete record was
made of all the glides made during the season. In the last
six days of experiment we made more than 375, but these
included our very best days. The total number for the
season was probably between 700 and 1000. The longest
glide was 622^ ft., and the time 26 seconds.
" On the last day of experiment we made a few attempts
at records. A line was drawn a short distance up the slope
as a starting mark, and four trials were made. Twice the
machine landed on the same spot. The distance was 165 J ft.,
and the angle of descent exactly 5 degrees ; time 6J sec.
From a point higher up the slope the best angle was 5
degrees 25 min. for a glide 225 ft. ; time ioj sec. The wind
was blowing about 9 miles per hour. The glides were made
directly to windward and straight down the slope. Taking
7 degrees as a conservative estimate of the normal angle of
descent, the horizontal resistance of the machine was
30 lb., as computed by multiplying the total weight, 250 lb.,
by the tangent of the angle of descent. This resistance
remained nearly constant at speeds between 18 and 25
130 AVIATION
miles per hour. Above or below these limits there was a
somewhat rapid increase. At 18 miles the power consumed
was i to if h.p. ; at 25 miles, 2 h.p. At the slower speed,
1 66 Ib. were sustained for each horse power consumed ;
at the higher speed 125 Ib. per h.p. Between 18 and 25
miles the h.p. increased almost in exact ratio to the increase
in speed, but above or below these limits the power increased
rapidly, and with a constantly accelerating ratio.
" On two occasions we observed a phenomenon whose
nature we were not able to determine with certainty. One
day my brother noticed in several glides a peculiar tapping
as if some part of the machine were loose and flapping.
Careful examination failed to disclose anything about the
machine which could possibly cause it. Some weeks later,
while I was making a glide, the same peculiar tapping began
again in the midst of a wind gust.
" It felt like little waves striking the bottom of a flat-
bottomed row-boat. While I was wondering what the cause
could be, the machine suddenly, but without any noticeable
change in its inclination to the horizon, dropped a distance
of nearly 10 ft., and in the twinkling of an eye was flat on
the ground. I am certain that the gust went out with a
downward trend which struck the surfaces on the upper side.
The descent was at first more rapid than that due to gravity,
for my body apparently rose off the machine till only my
hands and feet touched it. Towards the end the descent
was slower. It may be that the tapping was caused by the
wind rapidly striking the surfaces alternately on the upper
and the lower sides. It is a rule almost universal that gusts
come on with a rising trend and die out with a descending
trend, but on these particular occasions there must have
been a most unusual turmoil during the continuance of the
gust, which would have exhibited a very interesting spectacle
had it been visible to the eye."
His experiences up to this period Wilbur Wright made
public in two papers read before the American Western
Society of Engineers, but his subsequent work in 1903,
which culminated in the achievement of continuous flight,
took place as far as possible in seclusion and was for a long
time shrouded in mystery.
Having brought their gliding experiments to a pitch of
WILBUR AND ORVILLE WRIGHT 131
perfection so that they could not very well hope to gain
much more experience along these lines, they decided to take
the next and most important step of all, which was to build
an engine-driven machine that would make them indepen-
dent of the winds and of the contour of the ground.
Although at this period automobiles had developed the
high-speed petrol motor in a manner that made it obviously
the type of prime mover they needed, nevertheless, the
Wrights, like Langley, who at this time was engaged in trie
construction of the machine for the American army, were
unable to buy exactly what they required. They set to
work, therefore, to construct an engine for themselves. It
consisted of a four-cylinder four-cycle motor designed on
simple but in some respects very original lines. This power
plant when complete on the machine included two chain-
driven wooden propellers revolving in opposite directions.
It was December, 1903, when they attained success. On
the I7th of that month they made four free flights from
level ground against the wind. This performance took
place in secret and many doubted its accomplishment when
the rumours of the happening began to spread. An in-
teresting and rather sad contemporary event that is often
forgotten is that nine days previously Langley had made
his final attempt to launch his own machine at Arsenal
Point near Washington, and was unsuccessful.
In 1904 the Wrights made many more successful flights,
and in 1905 they improved the control of their machine to a
point at which they felt confident in introducing it to the
public. Their subsequent achievements are matters of well-
known history and may be studied in relationship to the
record of the movement at large elsewhere in this volume.
CHAPTER XIII
THE WORK OF VOISIN AND FARMAN
Early experiments on the Seine — The first aeroplane factory — Dela-
grange as the first customer — The early Voisin biplane — An English pupil
— Farman's successful circular flight — Farman becomes a constructor.
WHEN, in the early days of the new art in France,
the aerial exploits of Henry Farman and Leon
Delagrange were exciting the attention of the
whole world, few people knew who were the real designers
of the flying machines that these pilots were doing their
best to use. The men in the background to whom due
credit did not come until later were, in fact, the two brothers
Voisin and their engineer M. Colliex. It was at their factory
that they had established on the outskirts of Paris at
Billancourt-sur-Seine that the first really successful French
aeroplanes were built.
Several years prior to the time when Delagrange and
Farman took to the air, the Voisin brothers were already at
work on aviation. In 1904 they constructed for M. Arch-
deacon, who was a great patron of the science and by whose
encouragement early progress was much assisted, some
large box kites, and it is very clear that their later work,
that is to say the machines they built for Farman and
Delagrange, was based upon the results of those kite
experiments. There was a resemblance, at any rate, between
the two types of aircraft, and to this day the large biplane
with vertical side panels is familiarly known as a " box
kite " among pilots.
Experiments were conducted over the Seine with the
early Voisin kites by towing them behind a fast motor-boat.
On these occasions M. Voisin himself was the pilot. Much
time was necessarily occupied over an apparently small
amount of progress, but it must be remembered that in
132
WORK OF VOISIN AND FARMAN 133
those days the work had to begin at the very beginning and
one of the greatest difficulties, which is not always realized
by those who now look back on the past, was to find any
suitable place where it was possible to make any sort of
practical trial with a full-sized man-carrying machine.
Archdeacon, Voisin, Bleriot, Santos Dumont and Esnault
Pelterie were all doing their level best to solve the problem
of flight, and each naturally set about the task in his own
particular way. During the latter part of 1904 and the
early part of 1905 Archdeacon, Bleriot and Voisin appear to
have been very closely associated in their research, and
Voisin, it seems, ought properly to have the credit of being
the constructor of the early aeroplanes that went by the
name of Archdeacon and Bleriot. One of the early Bleriot
biplanes built by Voisin looked from the front like a flattened
ellipse, for at the extremities the upper and lower planes
joined one another by a curved panel. The same box-kite
principle, however, was still apparent, and it was evidently
supposed that the new form of extremity would help to
stabilize the machine. From a photograph of the apparatus,
it appears that two propellers were fitted, and unless the
photograph is deceptive it would seem that the angle of
incidence between the planes and the propeller shaft was
enormous, far greater than would be feasible for really
successful flight.
Most of the early work, however, was carried out on
machines that had no motors, the idea being to tow them
either behind a motor-car or a motor-boat. As Esnault
Pelterie soon found out to his cost, however, towing an
aeroplane by a motor-car is a dangerous business, especially
when you happen to have forgotten to install any means of
communication between the pilot on board the kite and the
driver of the car. It is very doubtful, too, whether Voisin
would have lived to build the successful aeroplanes that
he subsequently constructed had it not been for the fact
that he made his experiments over water instead of
over the land. On one occasion the machine took a header
into the Seine, and it was several anxious moments before
the pilot was seen to emerge none the worse for his ducking.
134 AVIATION
Experiment by trial and error of this sort may teach
slowly, but it teaches its lesson in a way that is not readily
forgotten, and by the time the Voisins had decided to make
a business of building aeroplanes they were also in a position
to be able to give their customers some sort of a guarantee.
There was, needless to say, a subtle distinction between
guaranteeing that the aeroplane could fly and making any
similar assurance as to the ability of the pilot, but there is
no doubt that the first firm of aeroplane constructors made
good their title from the day that they went into business.
The first order they obtained was one from M. Delagrange,
the second was from Henry Farman, who bought a duplicate
machine, except in respect to certain minor details.
One of those details proved of some importance in the
relative progress made by these two pioneer pilots. The
early Farman machine had its landing carriage wheels
mounted on castors, while the Delagrange aeroplane was not
thus equipped. It was, however, found very necessary to
allow this freedom of movement to the wheels in order that
they might adjust themselves more readily to inequalities
of the ground and also to any slight leeward drift of the
aeroplane when landing.
Another consideration that helped Farman to make suc-
cessful flights before Delagrange, was that he took the pre-
caution of making adequate arrangements for the use of
an aerodrome. He succeeded, in fact, in obtaining permis-
sion to make his trials on the army manoeuvre ground at
Issy les Moulineaux, and it soon became very evident that
anything less commodious than a field of these dimensions
was of comparatively small use to the budding flyer. When
a man is attempting to teach himself how to fly he needs to
be as free as possible from the worries of other things, and he
does not want to have to bear in mind that there is a hedge
or ditch some yards ahead which he must of necessity fly
over or fall into.
The Voisin aeroplanes supplied to Farman and to Dela-
grange were, as has been mentioned already, of the box-kite
kind, that is to say they were biplanes and they had vertical
panels between those planes, which produced a cellular
WORK OF VOISIN AND FARMAN 135
form of construction. In all there were four such panels
between the main planes, two at the extremities and two
about midway between the centre of the machine and the
extremities of the wings. The centre part of the space
between the planes was occupied by a girder-like construction
supporting the engine and pilot, the pilot sat in front of the
engine and the engine drove a propeller by a direct extension
of its crankshaft. The propeller was thus situated im-
mediately behind the main planes, and a portion of the
trailing edge was cut away so as to clear the propeller
blades.
The same girder member that supported the engine and
pilot was continued forwards in order to carry the elevator ;
this projecting portion was covered in with surfacing
material. Extending behind the main planes were four long
booms braced together by thin ash struts and steel wire ; at
the extremity of this outrigger was the tail. The tail was
similar in construction to the main planes, but consisted
of a single cell. Standing upright in the middle of the
tail cell was the pivoted rudder plate, which was under
control from the pilot's seat by means of wires coupled up
to a drum that was operated by a wheel arranged in much
the same way as a wheel is often used for steering motor-
boats. The elevator was operated by jointed rods, which
were also coupled up, through a sliding collar on a shaft, to
the same wheel. The elevator was operated by pushing the
wheel as a whole bodily forwards, which depressed the
leading edge of the elevator plane.
There was no wing warping or any other form of direct
lateral control. The aeroplane was designed to be stable
laterally ; if canted, the pilot was supposed to steer in such
a way as to accelerate the outer wing tip so as to increase
its relative lift and thereby restore balance. For the same
reason, it was necessary to steer wide and proceed leisurely
when trying to turn a corner, otherwise the outer wing tip
would accelerate too much and the machine would be liable
to slide inwards towards the ground. As nobody who
practised in those early days cared about flying too high, or
was indeed able to climb very much with the engine power
136 AVIATION
available, machines did not have to slip very far before
they hit the earth : consequently, however great their power
of recovery may have been in principle, the fact remains
that they seldom had an adequate chance of demonstrating
it in practice.
When on the .ground, the early Voisin biplane rested on a
pair of pneumatic -tyred wheels carried in brackets not
unlike the back bracket of a bicycle in general appearance ;
they were so arranged, however, as to afford a spring
suspension and also a free pivoting movement about the
columns supporting them. This landing chassis was
arranged immediately under the main planes. The tail
rested on a pair of much smaller wheels.
The total weight of the machine with fuel, etc., was about
1400 Ib. and the total supporting surface, including the tail,
which carried part of the weight, was about 535 sq. ft.
Allowing 150 Ib. for the pilot, the loading of the surfaces
was a little less than 3 Ib. per sq. ft. The span of the main
planes was about 33 ft. and the chord 6 ft. 6 in. The tail
was about 8 ft. span by the same chord as the main planes.
Various engines were tried in these machines at different
times, but the first aviation engine of note was the " Antoi-
nette " and it was with one of these that the Voisin biplane
used by Farman was originally fitted. The engine had eight
cylinders of no X 105 mm. bore and stroke : it was nomin-
ally rated at about 50 h.p. at uoo revolutions per minute.-
The weight of the engine was stated to be 265 Ib. The
propeller, which was made of steel, had a diameter of 7 ft.
6 in. and a nominal pitch in the order of 3 ft. The pitch
was adjustable by resetting the blades in the boss. At its
best, the gliding angle of the machine was supposed to be
between i in 6 and i in 7.
One of Voisin Freres' earliest customers was J. T. C.
Moore-Brabazon, a member of the Royal Aero Club, who
transferred his enthusiasm for motoring to a pastime that he
thought would possess a far greater fascination. He went
to France, and there learned to fly. Having obtained some
degree of competency in the air, he brought his Voisin
biplane, which was known as the " Bird of Passage," over
WORK OF VOISIN AND FARMAN 187
to England and established himself at the aerodrome that
the Royal Aero Club had then recently acquired in the Isle
of Sheppey.
As that particular machine was weighed in detail
it may be interesting to record some of the figures,
which are as follows : Planes, 180 Ib. ; chassis, 250 Ib. ;
tail planes, 55 Ib. ; tail wheels, 13 Ib. ; outrigger framework
carrying tail, 40 Ib. ; rudder, 10 Ib. ; elevator, 32 Ib. ; engine
and propeller, 320 Ib. ; radiator and water, 80 Ib. The
chassis portion included the girder and engine-bed, as already
described. The engine was an 8-cylinder E.N.V. rated at
50 h.p. The total weight of the machine, according to the
details, was thus only 980 Ib. The area of the main planes
was 445 sq. ft., the elevator had an area of 45 sq. ft., and the
tail an area of 107 sq. ft. The rudder area was 16*5 sq. ft.
The span was practically 33 ft., the chord 6 ft. 9 in., the front
edge of the elevator was 7 ft. 7 in. from the leading edge of
the main planes, and the front edge of the tail 13 ft. 4 in.
behind the trailing edge of the main planes.
Most of the constructional work was of ash, with the
exception of the steel tubing employed in the chassis. Being
flexible, the ash was very liable to bend, and it was, on the
whole, somewhat difficult to keep these early Voisin machines
in shape. The main planes consisted of two spars across
which light ash ribs were placed at intervals. The ribs were
placed in pockets formed in the surfacing fabric, of which
there was only a single layer. The planes were not hollow
as they are in the system of double surfacing that is now
commonly employed in aeroplane construction.
In order to appreciate what Voisin accomplished it is
necessary to remove from the mind the almost commonplace
character that aviation has already assumed to-day.
Previous to 1908, it may be said that flying did not exist
as an accomplishment so far as the world at large was
concerned. Wilbur Wright and his brother had flown in
America, but their success had passed from the public mind,
for so soon as they could really fly properly the Wrights
packed up their machines and came over to Europe to
make negotiations of a commercial character. The early
138 AVIATION
struggles of Delagrange and Farman on the flying-grounds at
Issy thus possessed all the realism of pioneer work, as indeed
they were . Day by day they made progress, but the progress
consisted at first in a series of hops. Then they would be
in the air for a few seconds at a time. Gradually the flights
get a little longer, and by degrees the pilots essayed to turn
round in the air, which was always recognized as the crucial
point in the development of the art.
So strongly was this felt to be the case, that M. Deutsch
de la Meurthe and M. Ernest Archdeacon jointly offered a
prize of 50,000 fr. for whosoever should accomplish a closed
circuit in the air of one kilometre in length. This prize Henry
Farman won on 13 January, 1908, and the event very
naturally aroused the greatest enthusiasm. It was, as those
who had given the prize anticipated, the beginning of a new
era in flying, for during the year 1908 aviation developed, as
has been shown elsewhere, in a truly phenomenal manner.
On 31 October of that year Farman himself flew from Chalons
to Rheims, a distance of 27 kilometres.
As was only to be expected, the practical experience of
flying taught Farman much about the desirable and un-
desirable points in aeroplane design, and it was not long
before he began to suggest alterations which in many cases
turned out to be improvements. In the course of time, too,
he entered upon constructional work himself and established
a factory of his own. The modern Farman aeroplanes are
very different from the early Voisin on which Farman learned
to fly, but in the history of aviation due credit essentially
belongs to Voisin as the founder of the first aeroplane factory
in the world.
Although the Farman machines of the present day have
no sort of resemblance in appearance to the early Voisin
biplanes out of which they were originally evolved, they
have one factor in common in that they have always been
characterized by a large wing surface in proportion to their
weight. Taking the Maurice Farman of the Military Aero-
plane Trials as an example, the area was no less than
666 sq. ft., of which 130 sq. ft. represented the area of the
tail. The weight of the machine, empty, was 1318 lb., and
WORK OF VOISIN AND FARMAN 139
it carried in flight a total weight of 1931 Ib. The loading
'was thus only 2-9 Ib. per sq. ft., which was practically
identical with that of the early Voisin, which, however,
carried far less useful weight.
The engine on the Maurice Farman in the Military Trials
was a 7o-h.p. air-cooled Renault. The main planes differed
from each other in span, the upper member measuring
50 ft. 6 in. and the lower member 37 ft. exactly. The chord
of both was 6 ft. 6 in. An elevator measuring 12 ft. by 2 ft.
3 in. was carried by an outrigger framework extending
12 ft. 3 in. from the leading edge of the main planes. Behind
the main planes, at a distance of 14 ft. 7 in. from the
trailing edge, was the biplane tail having a total area of
130 sq. ft. One very important difference between the later
Farman aeroplanes and the early Voisin biplane was the
absence of any vertical panels. The main planes were thus
no longer cellular in formation except so far as the construc-
tion of the framework might be considered in this light.
Hinged flaps were also introduced into the trailing edges
of the main planes, and these were coupled up to the control
lever so as to permit the pilot to increase the effective angle
of incidence of one wing tip or the other. A flap was also
added to the trailing edge of the tail in order to assist the
front elevator, and these two members were coupled up to
work in unison.
This involved a modification of the control itself, and
Farman introduced the vertical lever system in which the
balancing flaps on the wing tips are operated by a sideways
movement of the lever while the elevator was operated by
moving the lever to and fro. The rudder on the Farman
aeroplanes was controlled by a pivoted bar under the pilot's
feet. In the Maurice Farman, as flown in the Military Trials,
pedals take the place of a bar.
Another Farman detail much used by other designers is
a form of landing carriage in which skids are combined with
wheels so as to afford protection to the machine in the event
of a wheel being buckled or coming adrift in a rough descent.
The Maurice Farman machine has its skid members extended
forwards so that they assist in the support of the elevator ;
140 AVIATION
they are thus available to take the first shock even if the
machine were to pitch on its head. Normally, the wheels,
of which there are four, two to each skid, take the load.
Each pair of wheels is coupled together by a short axle, and
the axle is attached to the skid by an elastic strap and a
radius bar.
Having such a light loading, the machine is capable of
flying at comparatively low speeds and in the Military Trials
it demonstrated that it could fly at just under 37 J miles per
hour. Its fastest speed was 55-2 miles per hour. When
gliding, its speed was 38 miles per hour and its slope of
descent i in 6-8 ; it also showed itself to be capable of
climbing upwards at a rate of 207 ft. per minute for the first
1000 feet of its ascent.
To mention all the successes that have been obtained by
the Farman aeroplanes would be impossible, but to English
readers one event in particular must always stand out very
prominently, and that is the occasion of the London to
Manchester flight. When the Daily Mail offered the ex-
tremely generous prize of £10,000 for a flight from London
to Manchester everyone thought that it would be years
before the event could possibly be accomplished. A sum
of this magnitude, however, is no mean incentive to effort,
and within a very short time there were evident signs that
someone or other was likely to at least make the attempt.
Two pilots in particular, Claude Grahame-White and Louis
Paulhan, speedily made up their minds on the subject,
and this remarkable event almost started as a race. Both
competitors used Farman biplanes, but in those days Louis
Paulhan had had very much more experience in the air than
Grahame-White, who, comparatively speaking, was then a
beginner. His pluck, however, was of an uncommonly well-
seasoned kind, as many incidents in his attempt went to
prove. Paulhan, as history has recorded, succeeded in
accomplishing the journey and in winning a thoroughly well-
deserved prize. His success formed another notable step
in the progress of aviation, and it served in consequence
as a great stimulus to future effort on the part of all who were
engaged in the subject.
CHAPTER XIV
THE WORK OF DUNNE AND WEISS
Experiments on the hill-side — Soaring flight in the wind — The Dunne
aeroplane — Its negative wing tips.
SIDE by side with those who pioneered the successful
aeroplane as it is known to-day there has worked a
small and scattered school of students whose object
has more particularly been to devise a machine that should
be comparatively independent of the pilot's control for its
security of balance. In England, the names of Dunne and
of Weiss are intimately associated with this field of research,
and it seems proper to refer especially to the nature and
results of their labours.
It was on the steep hill-side near his home in the south of
England that the Weiss bird-like models used to be flown
day after day in the wind with the object of teaching the
experimenter how he might design a self -balancing craft.
Hundreds of different gliders, some of which were large
enough to carry several pounds' weight, were made and tried
until at length he learned how to proportion the wings and
the body so as to ensure stable flight. When the wind blowing
up the hill-side was strong enough, these imitation birds
would frequently soar upwards and backwards to a con-
siderable height before gliding down into the wind towards
the earth.
Having attained to a sufficient degree of confidence in
his methods and in his design, Jose Weiss built a machine
just large enough to carry a man. A frail-looking little
object it was, too, just a pair of wings attached to a tiny
coracle-like body that contained neither engine nor control.
Underneath, was a kind of chassis on which the machine
141
142 AVIATION
could stand upright or run along the ground. It seemed to
me that anyone who flew in this device would need much
confidence and even more pluck, but Gordon England, who
became the pilot in question, evidently had sufficient of both
qualities, notwithstanding that he took his risks smilingly.
Sitting in the little body of the machine he would be
pushed off down the hill-side and gather way until such time
as the relative wind was strong enough to bear his weight.
Then the little aeroplane would gently leave the ground and
glide steadily and securely through the air. In windy
weather, soaring flight would to some extent often take place,
the machine remaining over the same spot above the ground
although flying all the time full speed through the opposing
wind.
As this particular machine had no controls, or none that
the pilot found of any use, his safety depended entirely on
its natural weatherliness. To a limited extent he might
influence the attitude of the machine by leaning his body
this way or that, but as a means of control it would have
been futile, for in the sort of weather that alone made these
experiments possible any aeroplane not inherently capable
of retaining its balance must inevitably have capsized in a
few seconds.
It was necessary to fly in a high wind and on the side of
a steep hill because the aeroplane possessed no engine. To
have attempted to glide in a calm would have involved great
difficulty in acquiring sufficient initial speed over the ground.
Also, it would have involved great danger on landing, since
the momentum (quantity of motion or product of weight
and velocity) of the machine would be excessive, and any
sudden contact with the earth's surface might have broken
it to pieces and injured the pilot.
To have attempted to fly in a wind without using the
side of a hill would have been equally futile, because there
would have been no means of ascending to a useful height
off the ground unless the machine had been towed like a
kite by a rope attached to a motor-car, which is a very
dangerous procedure.
The Weiss models were all very bird-like. Indeed, their
THE WORK OF DUNNE AND WEISS 143
designer was in the habit of experimenting on dead birds,
the wings of which he would stiffen by various means of his
own so as to cause them to remain extended in the attitude
of flight . In this way he succeeded in making some specimens
perform gliding flight. He also investigated the balancing
property of the bird's head by using paper collars to extend
the neck.
Others besides Weiss doubtless did as much or more in
other parts of the world and their names equally deserve
mention, Ettrich and Montgomery among them. It happens,
unfortunately, that the detail of their work is not equally
well known to me, which must serve as an apology if it is
no excuse. It is not, however, so much with a view to
drawing particular attention to the accomplishments of
any one man that the work of Weiss is here mentioned,
as with the object of illustrating the idea that inspires a
certain school of thought in the realm of flight to-day.
How far the solution of the difficulties in this case may
have been particular to the prevailing conditions rather
than general to the broader problem of flight, may itself be
an undecided question, but that only emphasizes the interest
of the subject at large. It serves, too, as a reason for
watching with particular interest the progress of those who
are still working in this field : of men like J. W. Dunne, for
example, who has developed quite a unique type of aeroplane
as the result of his own particular line of research. His
work is of especial value because it has been applied to the
construction of full-sized aeroplanes of both the biplane and
the monoplane class.
In the Dunne aeroplane the wings make a V in plan, each
wing has a variable camber and angle from shoulder to tip.
At the tips, the angle is negative and the leading edge of the
wing dips considerably below the normal line of flight. The
change of angle is gradual from shoulder to tip, and the
front wing spar slopes downwards from the body. The
surface of the wing is in part generated upon the surface of
an imaginary cone, which serves as the basis on which
the changes of curvature vary with the position along the
span.
144 AVIATION
Owing to the V plan form of the wings, the wing tips
lie considerably behind the shoulders. Their negative angle
of incidence is very pronounced in normal flight and on the
monoplane the extremities of the wings are downturned to
a very marked extent, as may be seen from the photograph of
this machine on page 53. It is important to realize that the
extent to which the wing tips are retreated is very consider-
able. In the biplane, for example, the rear extremities of
the wings lie more than 20 ft. behind the point of the V :
the span of this machine is 46 ft. There is, therefore, every
reason to regard the wing tips as representing the tail, which
otherwise is not present as a definite member.
From the foregoing brief description it will be apparent
that the Dunne aeroplane represents an actual example of
the use of negative wing tips for stability, which was
discussed in a previous chapter (p. 54). The theory of the
subject that is there presented, however, is a purely personal
one, and I do not presume to advance it as an adequate
explanation of the inventor's claims in respect to this
particular machine.
The control of the Dunne aeroplane is also an example of
the differential negative angle, for the flaps on the wing tips
alter the magnitude of the negative angle but never make it
positive. Steering is effected by moving the flaps in opposite
directions by the aid of separate levers, one on either side of
the pilot. At one extremity the attitude of the flap increases
the permanent negative angle of the wing tips, at the other
extremity it diminishes the amount . The machine banks and
steers its appropriate course without the aid of a rudder,
One pilot, Major Garden, has already secured his certificate
on the Dunne aeroplane, and that this machine has in fact
some real measure of stability in its design is shown by the
following official notice issued by the Royal Aero Club in
respect to a test conducted under its observation :
THE WORK OF DUNNE AND WEISS 145
"ROYAL AERO CLUB OF THE UNITED KINGDOM.
CERTIFICATE OF PERFORMANCE. No. i.
(Under the Competition Rules of the Aero Club.)
Flight of Aircraft Uncontrolled by Pilot.
" THIS is TO CERTIFY that on the nth December, 1912, a
Dunne biplane was entered for trial by the Blair Atholl
Aeroplane Syndicate, Ltd., the object of the trial being
to show the behaviour of this biplane when flying without
being controlled in any way by the pilot.
Particulars of Aircraft —
Type : Dunne Biplane, two seater. Overall span 46
feet. Total Lifting Surface 552 square feet.
Motor : 50-60 h.p. 4~cy Under Green.
Controls : Hand levers only, no automatic controlling
mechanism, gyroscopic or otherwise, fitted.
" Description of the Trial. — The trial took place on Salisbury
Plain on the 16th and I7th December, 1912. On the first
flight on the i6th the wind was blowing in gusts up to 20
m.p.h., and the pilot ceased to manipulate all controls for
a period of i min. 5 sees, whilst flying over a spot where
irregular disturbances of the air were, from the actual
experience of the official observer, known to prevail. The
pilot only resumed operation of the controls at the request
of the official observer, who was the passenger in the aircraft.
During this period, the aircraft was quite stable laterally,
there being an absence of both quick jerky movements and
periodical rolling. The apparent effect of a gust was to
cause the aircraft to turn steadily to the right or left.
"The second flight on the iyth was made under slightly
better weather conditions, and the pilot ceased to manipu-
late all controls for two periods of one minute each. During
one of these periods the controls were locked, and the aircraft
described a complete circle of 360°, banking of its own accord
at the correct angle. There was no feeling of side wind on the
face of the Official Observer, thus showing absence of
sideslip either inwards or outwards.
(Signed) " C. D. ROSE, Chairman.
(Signed) " HAROLD E. PERRIN.
February 4th, 1913."
10
146 AVIATION
It is interesting to observe, in the light of the decision of
the foreign courts on the Wright patent case, that the
Dunne aeroplane is practically the only actual flying machine
that evades the rudder cum warp combination.
The essential difference between the Dunne aeroplane and,
so far as I know, any other machine designed for inherent
stability is that whereas several types have had upturned
wing tip trailing edges, the Dunne obtains a very marked
negative angle at the tip by depressing the front edge of the
wing.
It might be argued that the virtues of the negative wing
tip cannot very well be affected by whether it has an up-
turned trailing edge or a downturned leading edge. There
is, however, another aspect of the situation that is best
demonstrated with a paper model. If a postcard is held by
its corners between the thumb and first finger of each hand,
it will warp naturally so as to produce the Dunne type of
wing with the downturned leading edge. One diagonal
remains straight, while the other assumes a simple curve.
It is only with difficulty that the cardboard may be warped so
as to give an upturned trailing tip in conjunction with a
cambered shoulder, and it will be observed that this effect
is accompanied by a flattening of the middle portion of the
wing thus represented, which thereby loses the advantages
of a cambered section over that portion.
CHAPTER XV
THE BRITISH MILITARY TRIALS OF 1912
Assembling in fifteen minutes — The three hours' flight — Wind tests —
Measuring the gliding angle — Cody's victory.
WHEN, as the result of somewhat tardy delibera-
tion, H.M. Government at last decided seriously
to develop aviation as a new arm in national
defence, a competition was decided upon as the best means
for ascertaining what types of aeroplanes were most likely
to be useful . The event was thrown open to the world, and took
place on Salisbury Plain not far from Stonehenge during the
month of August, 1912. Thirty-two aeroplanes were entered,
and 24 took up residence in the sheds that the Government
had had built to receive them. The site selected had been
the head-quarters of military aviation for some time, and
was also one of the depots of the " Bristol " Flying School, so
it was already an aerodrome well known to many pilots.
Of the thirty-two machines entered, twenty were British,
ten were French, one was Austrian and one was of German
construction. Of those that actually attended, seventeen
were British and seven were French. The German and the
Austrian machines did not materialize, having, it was said,
already been purchased abroad. Of the seventeen British
aeroplanes that were nominally in evidence, at least seven
of the newer makes were either unfinished or untested on
the opening day, and thus some of the very firms for whose
benefit the trials had, in a measure, been organized, spoiled
their own chances in competition with the older constructors
who, for the most part, had entered well-tried models.
The aeroplanes arrived in packing-cases, in accordance
with the rules, and the first episode in the event was their
assembly under official observation against time. Two
148 AVIATION
machines, the Avro biplane and the Hanriot monoplane,
were put together and flown in less than fifteen minutes,
the Bristol monoplane was similarly in the air in less than
eighteen minutes, but the majority of machines took over
an hour to erect. A few of the entries, as already remarked,
were so far from being in a position to fly that their un-
finished parts were quietly transferred to their sheds for
completion, which process lasted in some cases several
weeks and caused the sheds in question ironically to be
described as factories by those whose business or pleasure it
was to await the course of events.
During the whole of the month of August — the Trials
commenced on the 2nd, and were not declared over till
the 27th — the officers of the Royal Flying Corps were in
attendance on the entrants, who were allowed to suit their
own convenience about flying, provided that they notified
the secretary of the meeting, Major F. H. Sykes, of their
decision to undergo a test. Whenever the weather was
officially suitable for flying, a blue flag was run up on the
flagstaff as a sign to those who were ready that they would be
permitted to come out and fly, but the weather was so bad
and the prospect of three hours in the air so unpleasant that
far less flying was accomplished than might have been the
case had the three hours' qualifying test been optional as
the first event, or had the competitors realized that the
mere demonstration of the ability of their machines to go
out in any weather would have done them much credit in
the eyes of the judges.
In the memory of oldest inhabitants, England had never
seen such an August since she became an island, and
certainly Salisbury Plain during the Military Trials was the
place of places in which to appreciate the probability of the
estimate being a very true statement. It was a weary period
of false hope . The wind blew incessantly and the rain , having
converted the ground in the vicinity of the sheds into a deep
quagmire, whipped a fresh top-dressing of creamy mud for
each day's portion. Every morning at four o'clock many a
weary head was raised heavily from the magnetic pillow to
blink a sleepy eye at the tree-tops for any sign of a breeze.
BRITISH MILITARY TRIALS OF 1912 149
The weather changes with startling suddenness on the Plain,
and in the first light of dawn the air is apt to be calmer than
at any other period of the day. To lie abed was to be certain
of missing the best flight of the meeting, to go up to the sheds
was to be still more sure of spending a freezingly cold hour
or so sliding about in gum boots on the insecure surface of
terra firma.
It was one of the conditions of the Trials that competing
machines were to be put through a three hours' flight as a
preliminary qualifying test, and it was the uncertain
character of such an undertaking in such weather that
delayed progress in the beginning. Some of the entrants
had been smart enough to get their three hours' flight com-
pleted on the very first day, which was gloriously fine, and
they, therefore, were able as occasion offered to make some
headway with the other items that required less time. Later,
when the judges decided that entrants might take their tests
in any order they pleased, the business of the meeting
proceeded apace and all the pilots who were able to demon-
strate their machines as real flyers in the shorter tests also
found an opportunity before the close of the event to com-
plete the three hours' duration in the air.
It was an exhaustive trial in many respects, for the
conditions set a high standard and left few aspects of the
aeroplane in the dark. Every machine had to carry a pas-
senger whose weight with that of the pilot had to be made
up by ballast to a total of 350 Ib. In addition, fuel and oil
sufficient for a flight lasting 4-5- hr. had to be carried, the
weight of which, roughly speaking, represented another
350 Ib. Thus, there was a load in the order of 700 Ib. on
board every machine.
During the three hours' qualifying flight, the pilot had
to attain an altitude of 4500 ft. and maintain a height of at
least 1500 ft. during one hour of the test. It was also
essential that the machines should be shown to be capable
of climbing to an altitude of 1000 ft. from the ground at a rate
of not less than 200 ft. per minute, which test most of the
competitors successfully accomplished when setting out for
their three hours' flight.
150 AVIATION
The machines were also tested for speed with and against
the wind, and besides having to fly their fastest they were
also required to fly as slowly as the pilot considered to be
safe. Competitors had, moreover, to show that if their
engines were switched off in mid-air at an altitude of 1000 ft.
their machines would cover a distance of 6000 ft. in gliding
flight before alighting. Another test was to alight in a
ploughed field and to ascend therefrom. Also, it was
necessary to demonstrate in what distance each aeroplane
could be brought to rest after alighting on the grass.
Similarly, the aeroplane had to be capable of being steered
while running on the ground, the ability to do which is in
most machines derived from the blast of the propeller
blowing on the rudder : some machines are, however, fitted
with a pivoted skid under the tail, which is interconnected
with the rudder mechanism. The final incident of the Trials
was the dismantling of the machine and its attachment
behind a motor-car for road transport, after which it was
again assembled and flown for the last time.
No definite marks were awarded for performances in
the various events, which were intended mainly to provide
a uniform basis on which the judges could estimate the
usefulness of the different types from the military point of
view. Many other considerations besides actual achieve-
ments were in fact weighed in the balance before the award
of the prizes, which amounted to £8900, was made.
Of that sum the Cody biplane won the first prize of £4000
open to the world and also the first prize of £1000 open to
British subjects for machines manufactured wholly, except
the engine, in the United Kingdom. The second prize of
£2000 open to the world was secured by the French Deper-
dussin : a second prize was not awarded in the British
section. Three third prizes of £500 each were won by
British aeroplanes, two by the Bristol monoplanes and one
by the British Deperdussin. Awards of £100 each were also
made in respect to the performances of the Hanriot mono-
plane, the Maurice Farman biplane, the Bleriot monoplane
and the Avro biplane.
The double victory of the Cody was a notably pop-
BRITISH MILITARY TRIALS OF 1912 151
ular win, for not only had Cody himself been a most
persevering pioneer, but his close association with the army
in connection with his well-known man-lifting kites had
shown him many military requirements that he set himself
to realize in the design of his very first machine. Although
so large, the Cody biplane proved a handy craft under Cody's
control, and it showed itself to be possessed of a remarkable
range of speed. At its slowest, it flew at 48-5 miles per hour
and its fastest speed was 72-4 miles per hour, which repre-
sents an increase of nearly 50 per cent on the minimum.
The fastest machine in the Trials was the Hanriot mono*
plane, which was timed to do 75*4 miles per hour ; the
slowest was the Maurice Farman, which made 55-2 miles
per hour. The speed range of the Farman was considerable,
however, for it showed itself to be able to fly at 37-4 miles per
hour, which was a slower speed than any other slow speed
demonstrate^ in the competition. A slow speed of this
order has marked advantages when alighting, and it is
especially useful for beginners. This ability to fly slowly
on the part of the Maurice Farman is due to its immense area
in proportion to its weight, the wing loading being less than
3 lb. per square foot : one machine, the Bristol monoplane,
carried as much as 9 lb. per square foot.
The speed range of a machine is an indication of the
reserve power available over and above that required to fly
under the conditions of least resistance. It does not follow
that the slowest speed possible on the part of a machine is
necessarily its speed of least resistance ; rather the contrary.
The variation of speed is brought about by a variation in
the angle of the wings and is made by an adjustment of
the fore-and-aft balance with the elevator.
A wide margin of power is most important, as has already
been explained, and it has also been pointed out that there
are advantages in large lightly loaded wings of considerable
span. In general, the monoplane is always more heavily
loaded on its wing surface than is the biplane, and if one of
the objects of its design is to fly as fast as possible with
the power available, it therefore employs only so much wing
area as may actually be required for the purpose.
CHAPTER XVI
SEA-PLANES
[This chapter is abstracted from the introduction to a report on the
meeting of Hydro-aeroplanes held at Monaco in April, 1913, prepared by
the author for the Aerial Defence Committee of the Navy League.]
HYDRO-AEROPLANES, or sea -planes, differ
only from land aeroplanes in that they are de-
signed to ascend from and alight on the water
instead of on land.
Directly, this distinction affects only one part of the
machine ; indirectly, it may affect structural detail in many
parts, and even cause distinctions of importance to arise
concerning the pilot's art of control.
Ordinary land aeroplanes are equipped with wheels on
which they can gather speed preparatory to ascent into
their proper element. Hydro-aeroplanes, or sea-planes as
the Admiralty has decided to call them, have floats
designed to permit of the same manoeuvre on water.
It is an essential preliminary to flight, this getting up
speed on the ground or on the water as the case may be,
for an aeroplane is air-borne solely by virtue of its motion
relative to the atmosphere.
The machine is driven over the face of the earth by the
force of its propeller in order that it may make its own wind
under the wings. The wings being set at an angle deflect
this relative wind downwards, and so there is, by Newton's
first law of motion, an upward reaction tending to lift the
machine.
Not until the speed exceeds a predetermined minimum
which depends on the size of the wings in proportion to the
weight of the machine and its load, is the force under the
wings sufficient to support continuous flight. Until that
152
SEA-PLANES 153
speed is attained, the aeroplane, in common with all other
physical objects, is held down by the earth's attraction.
And so it is that one must speed up over the ground or
over the water before it is possible to fly. Some machines
require more room for starting than others, owing to the
greater weight carried per square foot of wing area, but
the large biplanes, which although heavy themselves are
often very lightly loaded in respect to their wings, can
generally ascend in a very short distance. Machines that
have extremely powerful engines in proportion to the weight
carried can also rise in a fairly short distance, because they
are able to acquire their high speed at a relatively fast rate
of acceleration.
The existence of a real wind also materially affects the
situation, for a wind is a movement of the atmosphere in
respect to the earth, and, therefore, it influences the
distance that the aeroplane must travel in contact with
the earth before it can acquire the velocity relative to the
atmosphere on which it depends absolutely for its ability
to fly.
For example, a head wind blowing against the machine
in itself provides a certain amount of relative motion in
respect to the wings, and the machine need not necessarily
move so fast over the ground in order to acquire its proper
flight speed through the air. On the contrary, a following
wind makes it more difficult to rise quickly, because the
machine must travel over the ground at the speed of the
wind plus its own flight speed, before it can establish that
relative motion in the atmosphere on which it depends for
its aero-dynamic support.
The ability to rise readily is important, whether it be
from land or water. In both cases a long run is likely to
be intercepted by obstacles and so to terminate ineffectu-
ally, while, by subjecting the machine for a long period of
time to the jolting of an uneven surface, the risks of struc-
tural damage are naturally increased.
Machines designed with undercarriages for alighting on
land as a rule have elastic suspension devices for the at-
tachment of the wheels, which absorb some of the shocks.
154 AVIATION
Hydro-aeroplanes, on the contrary, for the most part have
their floats rigidly attached to the machine, which thus
receives the full impact of the waves.
The water can be very hard under certain conditions,
and the problem of designing an aeroplane that shall* be
reliable for use over water is far less simple than some
people might suppose. It is not only necessary that it
should be strong, it must also be light. Floats must not
only be large enough to give buoyancy to the machine, but
they must be so contrived as to reduce the resistance to
motion on the water to a minimum.
The former condition could be satisfied by any sort of
water-tight box of sufficient capacity, but the resistance
to its motion through the water would altogether preclude
the effective use of an ill-designed contrivance of this sort.
Many of the floats actually in use on waterplanes have the
appearance of being mere boxes, but in fact they are in-
tended to have other qualities besides that of buoyancy.
Instead of ploughing through the water like an ordinary
boat, the proper sort of float for the hydro-aeroplane should
have the quality of rising to the surface when at speed.
Such behaviour diminishes the resistance to motion very
much indeed.
The ability to skim over the surface of the water is due
in part to the support of the wings and in part to the in-
clined flat bottom of the boat, which wedges itself out of
the water when the machine attains to a sufficient speed.
It is possible for boats themselves to be so built that they
will skim the surface of the water, and such craft, which are
known as hydroplanes, are remarkable for their high speed.
They are at present built only in comparatively small
sizes, but of late years they have achieved considerable
popularity among enthusiasts in motor-boating circles. As
some hydro-aeroplanes are fitted with hydroplane boats
to accommodate the pilot and passenger, instead of box-like
floats that behave as mere " webbed feet/' it may not be
altogether inappropriate to recall some interesting circum-
stances relating to the invention of this very modern type
of watercraft.
The Henry Farman hydro-biplane about to rise and about to alight. Below is a fast flat-
bottomed motor-boat, showing how the bows rise from the water at high speed.
SEA-PLANES 155
It was in 1872 that the Rev. C. M. Ramus, who then held
the living of Playden, near Rye, in Sussex, wrote a letter
to the Admiralty informing them of certain experiments he
had made that led him to suggest a radical departure from
the orthodox design of ships. Interviews with the Director
RCSA CM- RAMUS1 FIRST MODEL 1572 »* J I THORNICROFT 3 DCS16N 1577
INCLINE. >&
REV CM. RAMUS DESIGN 1572
"Flight" Copyright Drawings
Sketches of the original designs for a hydroplane made by the Rev. C. M. Ramus
in iSya. Sir John Thornycroft's first design is also shown, together with a sketch
made by him to illustrate the forces that cause a towed boat with a rounded stern to
rise up at the bows. A square stern for a hydroplane is essential. The notch in the
bottom of most hydroplanes is a kind of intermediate square stern.
of Naval Construction took place and the following memor-
andum, signed by that official, was issued two days later :
" Rev. Mr. Ramus has to-day communicated to me the
plan of designing steamships for great speed referred to in
his letter of the 5th instant.
" It consists in forming a ship of two wedge-shaped
bodies, one abaft the other.
' The object of this invention is to cause the ship to be
lifted out of the water by the resistance of the fluid at high
speeds.
" The double wedge provides that while the bow is lifted
by the foremost of the inclined surfaces, the stern is lifted
by the after one, and these may be so placed with regard to
each other that the ship shall always keep her proper
trim."
It will be observed that Mr. Ramus's invention related
to the use of a flat -bottomed boat in two lengths, that is to
say the bottom sloped upwards from the stern to the centre
of the boat and then began again at a lower level, whence
it sloped upwards to the bows. In the centre there was,
156 AVIATION
therefore, a sharp step or change of level from the front
end of the stern portion to the rear end of the bow portion
of the bottom of the boat, and it is this step that charac-
terizes the hydroplane as a distinct type of watercraft.
Sketches herewith show the Ramus design.
The object of the step is to assist the boat to skim the
water on a level keel. A flat -bottomed boat pure and simple
is in a sense half a hydroplane ; it automatically assumes
an inclined attitude for the purpose of skimming the sur-
face, and in so doing the bows rise clear out of the water.
The somewhat curious spectacle of a fleet of small motor-
boats proceeding round the course with their bows in the
air is often a characteristic feature of modern high-speed
racing.
The floats of the hydro-aeroplane of to-day are for the
most part in a category corresponding to the flat -bottomed
boat rather than to the class of the hydroplane proper, for
" Flight" Copyright Sketches
Front float and tail float used on the Short hydro-aeroplane exhibited at Olympia
'13-
avy.
1913. Messrs. Short Bros, have constructed many hydro-aeroplanes for the British
N£
owing to their short length it is the exception rather than
the rule to find the distinguishing step in their construc-
tion. At the Monaco meeting of waterplanes in April, 1913,
there was but one make of machine employing stepped
floats ; all the others had floats with simple flat bottoms
turned upwards at the bows.
The stepped float alone, it seemed to me, demonstrated
the hydroplaning quality of skimming the surface on a
level keel. The other floats for the most part dug their
heels into the water to a much greater degree, and usually
created a stern wave of such size as to suggest the exist-
ence of much unnecessary resistance.
SEA-PLANES
157
It is to be remembered that speeds that would be con-
sidered very fast for any sort of boat are very slow for flight.
In consequence, it is not easy to acquire a proper flight-
speed while trying to rise from the water, and it is only
with considerable difficulty that pilots are able to get some
machines " unstuck."
Anything that is potentially capable of reducing the re-
sistance on the water is obviously a measure worthy of
experiment, and I think the stepped float is properly to be
regarded in this category.
A stepped float to be effective would necessarily be
longer than most floats now in use, and preferably, I think,
should be long enough to render a tail float unnecessary.
"Flight " Copyright Sketch
Main central float used on the " Waterhen," a machine built by the Lakes Flying Co.,
and flown for trial purposes over Lake Windermere.
They must also extend far enough forward and be so de-
signed in the bows as to prevent them from diving under
the surface if the machine descends rather steeply. This
latter quality may in some measure be opposed to the
realization of a fine cut -water such as some pilots consider
desirable in order to reduce the impact of a rough sea.
By the aid of a proper float, a high water speed could be
obtained with the wings of the machine at a fine angle, in
which altitude they offer least resistance. Having accele-
rated to the utmost, the attitude of the wings must be
158 AVIATION
quickly changed to a coarser angle in order to lift the
machine into the air, and it should be possible with a suit-
ably designed stepped float to facilitate the separation of
the float from the water surface.
A float without a step tends to hinge on its stern in the
water and so to hold down the machine. In order to over-
come this, it seems to me that the rear step should be at
such a level and of such an area as to tend to give an
increasing resistance to immersion when the nose of the
machine is being tilted up for ascent into the air.
GOUPY
" F Light" Copyright Sketch
The Goupy undercarriage, with floats for alighting on the water.
Owing to alterations in the character of the wave at
different speeds, I should expect it to be important to avoid
placing the steps too close together, and I was rather sur-
prised to observe the comparatively short pitch of the steps
on the Nieuport floats used at the Monaco meeting.
In some stepped floats, air is admitted through a vent to
the instep with the object of " lubricating " the after sec-
tion with an air film. I have no information as to its
efficacy.
Timber was used exclusively for the construction of the
SEA-PLANES 159
floats on the machines at Monaco, and apparently there
were some instances of the employment of ordinary three-
ply material. Experience in other directions does not
suggest that ordinary three-ply wood is likely to prove
durable for hydro-aeroplanes' floats. The best practice is
more likely to follow the method adopted in modern high-
speed boat construction, where the hull virtually consists
of three shells interleaved with water-proof material.
The shells are fastened together either by sewing with
copper wire, or by riveting, or by fastening with nails that
are turned over into the wood.
"Flight" Copyright Sketches
Types of floats used on the Borel and the Nieuport hydro-aeroplanes.
It was not possible to obtain exact information relating
to the weight of the floats. Those used on the Henry
Farman were stated to weigh about 140 Ib. each. I was
informed that the two floats on Pre vest's Deperdussin
weighed 130 Ib. each. Judging by appearances, and the
evidence of these figures, I should say that no float weighed
less than 100 Ib. and that some probably weighed nearly
200 Ib. each.
With the exception of the Farman and Nieuport machines,
all the floats employed at Monaco were rigidly attached to
the framework of the machine. The suspension of the
Farman floats was effected by means of elastic bands, this
suspension being inside the floats on one of the two machines
and outside on the other.
The Breguet machines employed rubber tension springs
in one instance and steel helical springs in another.
For the most part, the tail floats were rigidly fixed to
160 AVIATION
the backbones of the machines, but in one or two cases they
were pivoted so as to turn in unison with the rudder. One
such example was the Borel, and M. Borel, the designer,
stated that, so far as his experiments had gone, he con-
sidered it to be an improvement that justified the com-
plication. Some instances of machines having broken
their backbones draw attention to the severe stresses in-
duced by a tail float and raise the question of the desir-
ability of trying to avoid its use altogether.
CHAPTER XVII
ACCIDENTS1
The importance of debris — Formation of the Investigation Committee
— The Rolls accident — Wind shocks — Trick flying and its dangers —
Upside - down in mid - air — Parke's dive — The risks of flying with an
underpowered engine.
ACIDENTS, to which vehicles of any description
are liable, are so terrible in their power to bring
suffering that the least civilization can do in memory
of the victims of its progress is to take pains to learn the
causes of the disasters and to apply the lessons they teach
in such a way as shall minimize similar risks in the future.
The theory is admirable, but the practical accomplishment
of the task, which alone makes the idea worthy of any more
respect than is due to the average pious wish, is no easy
matter. Particularly is this true of accidents that take
place in the air.
Trouble may overtake a flyer when he is far beyond the
accurate observation of casual spectators on the ground,
and if, as is too frequently the case, the result is fatal,
there remains nothing but the debris out of which to re-
construct the event. How useful those poor fragments
of a shattered machine may be, however, none who has
not pursued an inquiry into the cause of an aeroplane
disaster can possibly realize. The morbid interest in these
melancholy affairs that makes some people take little
1 Having the privilege of membership of the Public Safety and Acci-
dents Investigation Committee of the Royal Aero Club and having
served on the Departmental Committee on the Accidents to Monoplanes,
1912, I feel that it is proper to acknowledge the advantages that I have
received from these positions, which have enabled me to hear the personal
views of others under circumstances that would not ordinarily have
occurred.
II 161
162 AVIATION
pieces of wood and the like as mementoes of the occasion
is well-nigh criminal in its disregard of the value that
may attach even to the most insignificant part.
An instance in point may be cited in a case where two
little brass wood screws were missing from an object of
importance, and were ultimately recovered from a man
residing in Liverpool ; the accident took place within fifty
miles of London ! In connection with the same case a
pond had to be dragged in order to recover a small piece
of iron that had been thrown away by someone who had
picked it up when the accident occurred. The evidence
afforded by the parts in question proved to be of first-class
importance in the reconstruction of the causes of the
mishap.
The necessity for systematically investigating aero-
plane accidents is obvious, and there already exists certain
machinery that works to this end under the aegis of a
committee known as the Public Safety and Accidents
Investigation Committee of the Royal Aero Club. This
Committee was formed in the year 1912, in order to meet
the evident need for inquiry in such a way as would avoid
the overlapping of the energies of separate organizations.
The Royal Aero Club, as representing Great Britain on
the International Aeronautic Federation, had already
been filing particulars of aeroplane accidents during a
considerable period of time, and were on the point of ex-
tending this work. At the same time, the Council of the
Aeronautical Society, which devotes itself more par-
ticularly to the scientific side of aviation, was particularly
anxious to give practical expression to the views of its
Chairman, Major-General R. M. Ruck, C.B., who advocated
that the technical aspects of each individual case should
be examined by representatives of an authorized body.
The Society, therefore, unanimously accepted the invitation
of the Royal Aero Club to nominate representatives to
serve on the special committee that the Club had decided
to form under the chairmanship of Colonel H. C. L.
Holden, C.B., F.R.S.
Obviously, the point of first importance in the investi-
ACCIDENTS 163
gation of accidents is to ensure the collection of reliable
data. To this end the Committee proceeded to appoint
representatives in all the principal centres, whose voluntary
duty it is to proceed immediately to the scene of disaster,
and, as far as may be necessary, take charge of the pro-
ceedings. The status of the committee in this matter has
been recognized by the Home Office in the form of instruc-
tions to the police throughout the country, ordering them
to prevent interference with aeroplane wreckage, pending
the arrival of a Club representative. In this way an
excellent start has been made towards the accomplishment
of really useful work, and from the time of its incep-
tion the committee has unfortunately been only too
busy.
One of the greatest difficulties associated with the in-
vestigation of an aeroplane accident is to establish facts
relating to what was seen to occur by those on the ground.
Eyewitnesses often differ as to essentials, and even as to
the sequence in which things happen ; it is for this reason
that solid objects picked up near a wrecked machine often
afford most valuable clues. It has occasionally happened
that certain things have come adrift in mid-air and have
fallen from the machine while it was yet flying ; their
relative positions along the line of flight may thus afford
evidence as to the origin of the disaster and sequence of
events that culminated in the final fall. Those whose
misfortune it is to witness such accidents should thus be
particularly careful to disturb nothing that they may find
without first making in writing a note of the exact location,
together with such other particulars as may seem to be of
significance.
It is not surprising that eyewitnesses should often be
unreliable ; few people train themselves to observe ac-
curately, even under normal conditions, and the sight of
an aeroplane accident is sufficiently disturbing to suspend
the process of ordinary thought. A vivid recollection of
the regrettable day when the Hon. C. S. Rolls was killed at
Bournemouth, during the third flying meeting held in
England, still remains with me ; with it also stays the re-
164 AVIATION
collection of the innumerable versions of the calamity that
passed current during the day. Being an eyewitness
myself, it interested me to hear the accounts of others
who also said that they had seen everything ; and from that
hour I came to the conclusion that even first-hand reports
must be subjected to the utmost scrutiny.
On this particular occasion I happened to have very
good reason for watching the machine in flight, for I be-
lieved that the pilot was about to make a performance
liable to be fraught with danger. His purpose was to alight
in a ring marked on the ground, and the wind was blowing
in such a direction as to make it necessary for him to fly
over the grand-stand when finally approaching the mark.
The ring being at no great distance from the barrier would,
I thought, involve a sharp descent, and I was anxious to
see how so able a pilot would manoeuvre his machine under
these circumstances.
To anyone flying over the grand-stand the ring may
have seemed unexpectedly close, and I was not surprised
to see the pilot make a quick dive towards it. While still
some height from the ground he tilted his elevator to flatten
out ; the next moment the machine fell headlong, and
poor Rolls was beneath it. In him, flight lost one of its
most sincere and accomplished students. The cause of the
disaster, there is small reason to doubt, was the springing
of the booms that supported the tail of his machine, which
were struck by the propeller and broken. The mere presence
of the tail on this machine, which was a French-built
Wright biplane, was an experiment at that time. Their
failure was due to lack of structural stiffness, for they bent
under the extra stress of the sharp manoeuvre of flattening
out, and so fouled the propeller blades.
When the elevator was used to reduce the steepness of
the descent, the forces brought into play would tend to
make the machine rotate about its transverse axis, which
tendency would be resisted by the damping effect of the
tail plane. Under ordinary circumstances, the Wright
biplanes of that time had no horizontal tail planes, and so
the inertia to rotation under the action of the elevator was
ACCIDENTS 165
small. Whether the pilot elevated to an extent likely to be
dangerous under ordinary circumstances is beside the point.
In his case, the effect of using the elevator was to throw a
stress on the machine in mid-air that it had not properly
been designed to withstand.
It is, of course, sometimes impossible to prevent fractures
when an aeroplane makes a rough landing, for the sudden
arrest of a moving mass may give rise to stresses that
no reasonable structure could withstand. Even in mid-
air, should the pilot completely lose his control at a great
height, and the machine acquire a very excessive velocity
of its own accord, stresses may be set up that may have
fatal consequences. It is certain, however, that there is no
excuse for failure under any normal condition of flight in
which the pilot retains his command of the machine.
That parts of aeroplanes have given way in flight, the
investigations of the Accidents Committee have shown
beyond all doubt. There have been some cases of wings
collapsing, and attention has thus been drawn particularly
to the question of adequate bracing, both externally and
internally, and to the strength of spars and ribs.
Some pilots of experience have spoken of having had
their machines occasionally struck excessively sharp blows
by the wind, but whether aeroplanes are in fact liable to
be stressed to breaking-point by such sudden and in-
calculable forces remains an undecided point.
Several accidents have resulted from the deliberate
performance of tricks in the air, such as were at one time
notorious in America, where several pilots have been killed
in front of the spectators. Catering to the sensations of
the crowd, these men would display the most amazing
nerve in making steep dives followed by banked turns
in which -the wings would approach to a vertical position.
On one occasion a machine actually turned turtle through
over-banking under such conditions, and the pilot was
killed.
Much as the taking of useless risks is to be condemned
as a disservice to the cause of aviation, it is important to
recognize the potential value of dangerous practices that
166 AVIATION
increase the individual pilot's skill in the handling of his
craft. Dangerous flying is not in itself unjustifiable, but it
is to be expected that anyone wittingly attempting feats of
an especially risky character should make it a point of
honour to avoid flying in places where a false move might
involve danger to others.
One of the most remarkable escapes of which I have
ever heard befell Captain H. R. P. Reynolds, of the Royal
Flying Corps, while flying from Oxford towards Cambridge,
on 19 August, 1911. Having started his flight in the
morning, he was forced to descend near Launton, owing to
a thick mist, but he restarted soon after seven o'clock in
the evening, when the weather was both warm and fine.
There was a suggestion of thunder in the air, which was so
perfectly still that, describing his experience in a letter,
Captain Reynolds remarks :
" I scarcely moved my control lever until I got to Bletch-
ley, where it began to get rather ' bumpy.' I thought
nothing of it at first, but suddenly it got so much worse
that I began to think of coming down. There was a big
black thunder-cloud coming up on my right front, which
did not look reassuring. Below me there was what appeared
to be very good landing-ground.
" At the time, I was flying about 1700 ft. altitude by my
aneroid, which had been set at Oxford in the morning. I
began to make a glide with the object of alighting in the
field below. Directly I switched off the engine, however, I
felt the tail of the machine suddenly wrenched upwards as if
it had been hit from below, and I saw the elevator go down
perpendicularly below me. I was not strapped in, and I
suppose I clutched hold of the upright at my side.
" Before I realized anything more, I found myself in a
heap on the top plane. I stood up, held on and waited.
The machine, which was upside-down, just floated about
in the air, sliding from side to side like a piece of paper
falling. Then it overswung itself, so to speak, and went
down more or less vertically sideways, until it righted itself
momentarily the right way up. Then it slid down tail first
and turned over upside-down again, whereupon it recom-
menced the old floating motion.
ACCIDENTS 167
" We were still some way from ground and took what
seemed like a long time to reach it. I looked round some-
what hurriedly, the tail was still there, and I could see
nothing wrong.
"As we got close to the ground the machine was doing
long swings from side to side. In the last swing we slid
down, I think, about 30 ft. and hit the ground pretty hard.
When quite high up my idea had been to jump and get
clear of the wreckage. Fortunately, I hung on until
practically the end, only jumping off, according to eye-
witnesses, when about 10 ft. from the earth. Something hit
me on the head, causing a slight scratch, but what it was I
did not stop to inquire, being in far too much of a hurry to
get away from the machine.
" When I went out to examine the wreck next morning,
the tail and the elevator were practically unhurt. The
undercarriage being uppermost in the air was quite un-
touched and the propeller was also undamaged. My own
impressions o,f what occurred corresponded very well with
what eyewitnesses told me they saw, but it was a pity that
there was no one about who could give a technical account
of exactly how the machine behaved. I was told that just
before the smash there were two or three ' whirlwinds ' in
Bletchley and that one of these took all the leaves off a
tree."
A somewhat similar accident occurred to Captain Aubry,
of the French army, who was turned upside-down while-
driving a monoplane. His machine glided for perhaps
200 yards in this position, and then righted itself. The
pilot regained control and made a safe descent !
Another pilot who looked death in the face and lived
to recount his feelings was the late Lieutenant Parke, who
passed through a singular experience during the Military
Trials in August, 1912. Having finished the three hours'
flight on his biplane one morning about breakfast-time,
he proceeded to descend over the ground immediately in
front of the sheds. His object was to make a spiral glide,
but wrhen he had descended a little way he thought that he
wras going rather faster than he had intended, and thereupon
he raised his tail elevator so as to flatten out slightly.
168 AVIATION
He was surprised to find, however, that this action aug-
mented his velocity, and after repeating the attempt he
realized that he had lost control of his machine. According
to eyewitnesses, the aeroplane dived head first in a steep
spiral, and everyone who saw it felt certain that the next
moment it would be dashed on the ground. To the as-
tonishment of all, however, it suddenly flattened out in
the most perfect manner, and flew off quite normally just
as if the pilot had performed the manoeuvre on purpose.
But the pilot himself thought the end had come just as
much as the spectators, and was as surprised as they were
at his escape. This he owed to not losing his presence of
mind in an apparently hopeless position. Having done
everything that he considered proper by way of a control
movement, he decided as a last resource to put the rudder
hard over in the opposite direction to that in which he was
holding it. The machine responded with amazing alacrity,
and being well built did not fail structurally at the critical
moment. Nor was the pilot overcome in the least at this
sudden reversal of fortune, for he flew round the ground
and landed up-wind in the approved manner with such
apparent serenity that many of the paralysed spectators
really thought they must have witnessed a stupendous
"stunt."
Parke's dive, as it came to be known, drew particular
attention to the manner in which the elevator may usurp
the function of the rudder and vice versa when the machine
is canted. It appears probable that the circumstances
were such that the rudder and the elevator combined were
in effect acting jointly as a rudder, owing to the canting
of the machine. They thus locked the aeroplane in a spiral
nose dive. Ruddering outwards at the last moment brought
the machine into an attitude in which the elevator could
act properly, and the aeroplane immediately responded to
its influence. From considerations that have been dis-
cussed in the chapters on stability, it would seem proper in
principle altogether to avoid ruddering inwards in emergency.
Lieut. Parke was subsequently killed by a fall while fly-
ing over the Wembley golf course, and his fatal accident
ACCIDENTS 169
was fundamentally due to leaving the Hendon aerodrome
with an engine that was not then giving a sufficient margin
of power. When he decided to return, he was flying at a
low altitude, and his turn in the air brought him into the
lee of some trees where he encountered atmospheric con-
ditions that capsized his machine.
The dangers of flying with underpowered engines,
or overloaded machines, which is the same thing, cannot
be overestimated. Many accidents have been due to this
cause, and it is one to which pilots of experience, who
have every reason to know better, seem prone to succumb.
They too often take the risk of leaving the aerodrome
with an engine in a poor condition, on the off chance that
it will pick up after a minute or so in the air.
So long as they keep within the confines of the aero-
drome it is hardly possible to criticize such flying, inasmuch
as it might often come within the scope of justifiable ex-
periment. Aeroplanes must be tested, and those who test
them must sometimes be prepared to take risks of this
order. But it is neither safe nor justifiable to cross the
boundary of the aerodrome in such a condition, and particu-
larly is this true when the pilot carries a passenger.
It is not as if there could ever be any doubt in the pilot's
mind as to the state of his engine, for it is merely necessary
that he should make an invariable rule of ascending to
an altitude of several hundred feet before leaving the
precincts of the ground, in order to find out in time if it
is pulling properly. The reasons why it is so dangerous
to fly across country with a weak engine are twofold.
In the first place there is no margin of power with which to
combat bad weather, and in the second place the pilot
may get trapped into the necessity of alighting on dangerous
ground.
A weak engine implies that the machine is flying at a
low altitude, and it may be that the pilot will thus fly
over some boundary, and will have no means of safe re-
turn. The manoeuvre of turning, as has been explained
in the chapter on steering, involves extra power if it is to
be carried out on the same level.
170 AVIATION
If the engine is weak, the machine necessarily descends
while turning, and thus may be trapped behind the boundary
that it has just crossed. A row of trees, a river wall, or a
railway bounded by telegraph wires are all sufficient upon
occasion to trap the unwary under such circumstances.
It is especially dangerous, for instance, to venture into
the lee of trees and the like with a weak engine. In general,
it is also risky in such cases to turn down-wind. Rivers
and lakes are also likely to prove a trap to those who fly
over them with an insufficient margin of power, for they
are places where down-currents are apt to be prevalent
through local differences of temperature between the land
and the water.
In tropical climates heat eddies assume a really dangerous
character even to a pilot flying a machine in full power.
G. M. Dyott, who, with the late Capt. Hamilton, visited
Central America with his monoplane, met with some very
remarkable experiences over the plains of Mexico. There
the sunshine is so hot that shadows cast by the clouds
suffice to disturb the atmosphere in such a way as to pro-
duce whirling chimneys of ascending air. A machine
passing through one of these chimneys may be lifted
bodily some 20 or 30 ft. upwards. At other times, the
whole atmosphere seems to be rising. In the evening,
when the sun disappears behind the mountains, down-
currents set in with dangerous suddenness. On one
occasion Dyott was nearly trapped outside his aerodrome
by a row of tall trees, although he was flying quite high
at the time. Through the same cause Capt. Hamilton
was once tossed upside-down in the air.
Across his knees was the control bridge, which helped
him to keep in the machine, and above his head was the
tripod mast carrying the stay wires to the wings. The
machine landed on its nose upside-down, and the mast
saved the pilot, who extricated himself from this extra-
ordinary predicament unhurt !
While flying in the military manoeuvres of 1912 Capt.
Hamilton, who was then a member of the Royal Flying
Corps, was killed by a derangement of the engine in mid-
ACCIDENTS 171
air. Aeroplanes should, of course, be so designed that the
failure of the engine will be most unlikely to produce vital
consequences. In this case, however, the wing stays were
in some way broken by a fault originating in the power
plant, and the pilot lost his life in the subsequent fall of
the machine. Unfortunately, a brother officer who was a
passenger on the aeroplane was killed at the same time.
It has been one of the most serious, as well as one of the
saddest phases of latter-day disasters that two lives have
so often been lost in the same accident. When, in the early
days of flying, the pioneers used to tumble about with
their machines, there were many bruises but few deaths.
The tables seem to have turned against the flyer, for
misfortune now points a most insistent finger to the necessity
of making the art safer than it has been in the past. To
this end there is no surer way than the systematic investi-
gation of mishaps as they occur, which work the Com-
mittee of the Royal Aero Club does its best thoroughly to
accomplish.
Accidents over water differ from accidents over land in
the important particular that the more compact parts of
the machine are not necessarily damaged by falling on to
the water. On the other hand, the water readily damages
the wing structure and lighter parts of an aeroplane. In
view of this distinction, it seems important to take advantage
of the opportunity thus offered of saving the power plant
intact. If the power plant and the pilot occupy what is
tantamount to an independent body, this member might
conceivably be made water-tight, and even self-righting.
It is not only important to consider the saving of life,
which in connection with military reconnaissance potentially
means the acquisition of important information, but the
salvage of a self-contained unit including the power plant
would materially facilitate the re-erection of another
complete machine. Whatever the characteristic design
adopted may be, it seems to me that the above principle
might usefully be regarded as one of the governing factors
in the construction of waterplanes.
PART III
INTRODUCTION
IN the following chapters, the history of the conquest
of the air is discussed as far as possible in chronological
sequence, but at the same time with due regard to the
contemporary influence of events. Very often it happens
that those who work as pioneers in a new field of activity
go over ground that has already been ploughed, and it is
important therefore that those who subsequently record
the doings of the period should as far as possible try to
ascertain the extent to which knowledge gained in one part
of the world has been known to experimenters elsewhere.
Although this book is, in other respects, strictly devoted
to aviation — that is to say, to the branch of aeronautics that
is related to aeroplanes as distinct from airships — it is
inevitable that the development of both kinds of aerial
navigation should come under review in any attempt to
record the earlier history of man's invasion of the air. To
ignore the coming of the balloon would be to leave un-
mentioned the first great stimulus of success that did so
much to encourage others to work along the parallel line
of research that ultimately led to the evolution of the
aeroplane. Nevertheless, out of respect for the scope of
the present book, the digression from aviation into aerosta-
tion has been limited to a single chapter giving only so
much as seems of particular interest relating to this con-
necting link.
The more significant years in the history of flight run
somewhat as follows. In 1848 Stringfellow first succeeded
in demonstrating horizontal flight with a self-propelled
model. From 1891 to 1896 Lilienthal made his gliding experi-
172
INTRODUCTION 173
ments, and was the first really to persevere in the systematic
practice of the art of riding the air. In 1903 the Wrights,
after three years' gliding and research, built and successfully
flew their engine-driven aeroplane, which was the first
practical flying machine that had ever been made.
That event happened ten years ago at the time of writing
(1913). The intervening period is divisible into two parts.
From the end of 1903 to the beginning of 1908 forms the
first part : it was a preparatory period for the subsequent
development that took place with such phenomenal rapidity.
The year 1908 was the great year in the annals of avia-
tion, for the activities of that period constituted the real
starting-point of modern advance. In January, Farman
won the Grand Prix for the first circular flight accomplished
under official observation. Wilbur Wright, whose work
was previously but little known, flew in France during the
summer of that year, and greatly encouraged others by his
ability.
In 1909 Bleriot flew across the Channel. In 1910 Paul-
han flew from London to Manchester. In 1911 there was
the historic flight round Britain, in which Lieut. Conneau
and Vedrines competed so strenuously. In 1912 the
Military Aeroplane Trials on Salisbury Plain afforded con-
crete evidence of the first of the useful purposes for which
the aeroplane is destined.
In the recording of history, it is undeniably difficult to
know what to leave out, yet it is essential that much should
be omitted, not only for lack of space, but in order that the
mind may not be confused with many details that occupy no
proper place in the sequence of events although meritorious
enough in themselves. In what follows, I have endeavoured
to hold the scales as justly as my knowledge of the circum-
stances will permit.
CHAPTER XVIII
ROMANCE AND EARLY HISTORY
Birds as an inspiration to man — Leonardo da Vinci as a designer —
A bishop as an inventor — The impossibility of man-flight.
HAVING discussed the flying machine as at
present it exists, and having detailed both its
principles of action and the work of those more
directly responsible for its success, it will be easier to
appreciate in their proper light the early efforts of those
who by slow degrees prepared the way for the accomplish-
ments of the present age.
From a profusion of fable and myth, little of which,
with the exception of the story of Icarus, has even become
classic, it is difficult to select a suitable starting-point
in antiquity from which to reconstruct anything in the
nature of a chronological history of aeronautics. There
is not the least doubt that man wanted to navigate the air
from the earliest times, and it also appears that the two
branches of the art, which are now related to the use of
dirigibles and aeroplanes, were at first chosen indifferently
as plausible fields wherein to seek a solution of the problem.
It should be recognized, however, that the fundamental
idea of navigating the air by balloons is properly to be re-
garded as having been a more advanced thought in those
days than the idea of flying, for in birds man had, from the
very beginning, a visible example of the conquest of the air,
and it was only natural that he should see in the imitation
of their actions the first and brightest prospect of realizing
his desire.
On the other hand, it would be a mistake to say that
aviation was the only field of early thought, for several
of the ancient, if probably unreliable, tales suggest buoyancy
ROMANCE AND EARLY HISTORY 175
rather than dynamic support of the machines that are said
to have flown. Thus, even in that very early legend,
which dates back to 400 B.C., of Archytas, a philosopher of
Taranto, who " constructed a wooden pigeon, which could
fly by mechanical means. To wit, it was thus suspended
by balancing, and was animated by an occult and enclosed
aura of spirit,"1 there is as much suggestion of flotation
by means of some light gas as there is of sustentation by
dynamic force.
Little profit, however, is to be gained by laborious
inquiry into such very vague details, and indeed we may
pass without hesitation to the well-known name of Leonardo
da Vinci (1452-1519) as the first whose interest in the
subject is authenticated by records that are still extant.
The fertile mind of this many-sided genius sought to solve
the problem by the design of a man-operated machine,
but although it would be permissible to smile at such an
idea if suggested in the light of present-day knowledge, it
must be remembered that in da Vinci's time no engines
were in existence, consequently anyone who thought of
flying had necessarily to suppose that it could be achieved
by his own muscular exertions.
Leonardo da Vinci's claim to fame is due to the fact
that he was the first to prepare drawings representing
definite ideas of how the artificial wings should be con-
structed and attached to the human body. His machine
called for the use of the legs as well as the arms of the
operator. It did not, of course, ever come to anything,
but it is well worthy of note that his drawings are at least
two centuries earlier than any other authentic record
of a definite, even if impracticable, scheme for a flying
machine.
The main interest in these earlier ideas lies primarily
in the evidence that they bear of their author's conviction
of the ultimate achievement of flight. The names of men
who made public their notions on the subject deserve-
especially when, like da Vinci, they had already established
themselves in fields of orthodox work — to be handed down
1 Aulus Gellius, Nodes Attica, Lib. X, Cap. XII.
176 AVIATION
to posterity, for in those times ridicule was neither the
only nor the least of the penalties liable to be suffered by
men of advanced minds. It may be assumed that da Vinci's
ideas were known to men of his own time, but it is important
to observe that his writings could have had no influence on
subsequent thought, for his manuscript and sketches were
never published until more than three centuries afterwards.
Towards the end of the seventeenth century the navi-
gation of the air was again brought forward by Francis
Lana (1670), John Wilkins (1672), Besnier (1678), and
Borelli (1680). Of these, the first mentioned, Francis Lana,
a Jesuit priest, applied his knowledge of physics and mathe-
matics to a quantitative analysis of the problem of the
balloon. He was, it seems, the first to obtain a concrete
idea of the requirements, and although his suggestion
to use copper vacuum globes was, and still is, impracticable
for mechanical reasons, it was, like da Vinci's, a definite
conception. In any case, the fact that his calculations
were sound in principle, besides being the earliest of their
kind, gives Francis Lana an unquestionable claim to be
remembered. Had Lana's vows of poverty not prevented
him, he would have devoted money towards the practical
application of his investigations on the subject, and in
his writings he makes a touching appeal for someone
to put his ideas to the test.
John Wilkins, Bishop of Chester, reviewing the subject
of aerial navigation in his Dedalus, gave it as his opinion
that a flying chariot having wings operated by some sort
of spring offered the best chances of success. The import-
ance of this reference lies in the suggestion that a spring
should be used, for a spring in those days was about the
only sort of mechanical prime mover known to civilization.
John Wilkins, in having advocated its use, would thus
appear to have been the first to appreciate the necessity
of employing an engine to achieve flight. There is no
account of the Bishop of Chester having made any practical
experiments to corroborate his views on the subject.
Besnier, whose name will invariably be found in re-
ferences to early ideas on flying, may be said to have
ROMANCE AND EARLY HISTORY 177
obtained his fame through the Press, for his principal
achievement seems to have been the publication of a
design for a man-operated flying machine in the Journal
des Savants of 12 December, 1678. His proposal was
crudely simple and quite impracticable. It served, how-
ever, the useful purpose of drawing attention to this aspect
of the subject again, and thereby of giving a point to the
argument of J. A. Borelli, as set forth in his De Motu
Animalium, published in Rome in 1680. This Neapolitan
scientist discussed the flight of birds, and deduced from
their anatomy that it would be impossible for a man to
fly artificially by means of his own energy.
Coming from such a source at a time in the world's
history when there was no sort of engine other than a
spring, this dictum of Borelli's was generally regarded
as being, in effect, a statement that flight was impossible.
His verdict appears to have been very generally known,
and this expanded version of it was no doubt received with
considerable favour by those people whose narrow minds
lead them to regard any thought on such a subject as flying
as a mere waste of time, if not as positive proof of insanity.
The damping effect of Borelli's views on students of flight
lasted for a long time after his death, for the subject of
aeronautics appears to have been dropped for at least
a century ; it is interesting to observe, moreover, that
Borelli's deductions on the inadequacy of man's muscular
power to achieve flight still hold good.
Most flyers, even of later times, found it easier to lose
money on the art than to practise flying to their own
profit, so it may not be without interest to put on record
the name of a man who in all probability was the first to
obtain any material advantage from his connection with
the subject. On 17 April, 1709, the King of Portugal
made out the following order, in favour of a certain friar,
Bartholomew Laurence de Gausman : " Agreeably to the
advice of my Council, I order the pain of death against the
transgressor. In order to encourage the suppliant to apply
himself with zeal towards improving the new machine,
which is capable of producing the effects mentioned by him,
12
178 AVIATION
I grant unto him the first vacant place in my college of
Barcelos or Santarem and the first Professorship of Mathe-
matics in my University of Coimbra, with the annual
pension of 600,000 reis during his life. Lisbon, I7th April,
1709."
What records there are of de Gausman's machine speak
of the use of the attractive force of magnets and of pieces
of amber, and in general reveal the inventor thereof to have
been a visionary at the best, albeit one who introduced his
impossible projects to some purpose, if he ever really
obtained his post and his pension.
CHAPTER XIX
THE COMING OF THE BALLOON
Cavendish and hydrogen — The ingenious Dr. Black — The Mont-
golfiers and smoke — Pilatre de Rozier, pioneer pilot.
IN spite of legends to the contrary, it is extremely
doubtful if any serious practical experiments on
the navigation of the air had ever been made up to
the beginning of the eighteenth century, nor would there
seem to be any real likelihood of doing an injustice to anyone
if we skip another half-century from the date of the closing
record of the. last chapter. By so doing we arrive at the
time when Henry Cavendish made the civilized world
acquainted with the existence of an extremely light gas
that he called " inflammable air," but which we now know
as hydrogen.
At this point it is impossible to do better than to quote
the following passages from The History and Practice
of Aerostation, written by Tiberius Cavallo, F.R.S., in
1785, less than twenty years from the date (1766) when
Cavendish made known his researches in the 56th volume
of the Philosophical Transactions.
" Soon after this discovery of Mr. Cavendish, it occurred
to the ingenious Dr. Joseph Black, of Edinburgh, that a
vessel might be made, which, when filled with inflammable
air, might ascend into the atmosphere, in consequence of its
being altogether lighter than an equal bulk of common air.
This idea of the doctor's has been mentioned to me by two
or three different persons. But ... it appears that Dr.
Black never actually tried the experiment ; nor do I know
that any other person attempted it, before my experiments
on this subject, which were made in the year 1782. The
possibility of constructing a vessel, which, when filled with
inflammable air, would ascend into the atmosphere had
179
180 AVIATION
occurred to me when I first began to study the subject of
air and other permanently elastic fluids, which was about
eight years ago ; but early in the year 1782 I actually
attempted to perform this experiment ; and the only
success I had was to let soap balls, filled with inflammable
air, ascend by themselves rapidly into the atmosphere,
which was perhaps the first sort of inflammable air balloon
ever made. I failed in several other attempts of a like
nature ; and, at last, being tired of the expenses and loss
of time, I deferred to some other time the prosecuting of
those experiments and contented myself with giving an
account of what I had done to the Royal Society, which was
read at a public meeting of the Society on the 20th June,
1782."
It may seem rather strange, having regard to what had
gone before and what was to come, that the demonstration
of the principle of buoyancy in air should have been viewed
with such apparent apathy by men like Black and Cavallo,
but it is extremely characteristic of the strictly limited
interest that is often displayed by those who occupy
pinnacles of their own special sciences. Here, in the dis-
covery of hydrogen, was a means of overcoming the one
practical disadvantage of the scheme proposed by the
worthy friar Lana, whose copper globes would have been
crushed out of all recognition long before they were ex-
hausted to a degree sufficient for self-support. In Lana's
day, however, no one knew of any sort of gas that was
lighter than air with which the globes might have been
filled, so that Lana really made the only suggestion that
was possible, having regard to the limited knowledge of
the period.
Thus matters stood in 1782, and the public at large
remained totally unconscious of the means by which air
had been brought within prospective invasion. Science
had succeeded in leading man to the very threshold of the
kingdom he desired to conquer, and yet he must needs
have the assistance of an accident to enable him to set
foot within the aerial world that was in due course to
become his.
THE COMING OF THE BALLOON 181
The historical experiments of the brothers Montgolfier
are familiar to all, but it is not so generally recognized that
although their balloon was essentially a premeditated in-
vention, the true principle upon which it entirely depended
for its success was a subsequent discovery, and to this
extent the success of these experiments may be said to
have been accidental. The Montgolfier balloons lifted
themselves in the atmosphere because they were full of
hot air, which is lighter than cold air, but Montgolfier
imagined that the effect was caused by the smoky " sub-
stance " produced by the fires over which the balloons
were inflated. The use of heat, which was incidental to
the production of the desired smoke, thus appears to have
been quite an accident, although, as a matter of fact, it
was, of course, the sole cause of the successful result.
It is indeed strange that this truth should have remained
unrecognized for so long, not only by the Montgolfiers,
but by the scientists of the day ; in fact it is somewhat
remarkable that men should have been blind to this simple
solution of the problem through all those years, seeing that
the ascensional force of hot air is visibly demonstrated
in many natural phenomena of daily occurrence. To any
student of evolution the situation is not without its lesson —
the picture of man forced to find the simple beginning
among the things ready to hand, by being persistently
denied success in his initial efforts to commence in those
heights whither his imaginative mind so delights to wander.
It is a point well worthy of reflection that there was
scarcely a period in history when some form of hot-air
balloon might not have been devised with reasonable success.
Popular belief is that the Montgolfiers were attracted
to devote themselves to a study of the subject as the result
of having read. Dr. Priestley's Experiments Relating to
Different Kinds of Air, and the traditional story of their
invention of the hot-air balloon is that they observed
the buoyancy of clouds in the atmosphere, and thought
that they might reproduce the phenomenon by the aid of
some corresponding cloudy substance that they might be
able to manufacture. It occurred to them that smoke
182 AVIATION
might be suitable, and according to Cavallo's history,
" Stephen Montgolfier, the elder of the two brothers, made
the first aerostatic experiment at Avignon, towards the
middle of November, 1782. The machine consisted of
a bag of fine silk, in the shape of a parallelopipedon, the
capacity of which was equal to about 40 cu. ft. Burning
paper applied to its aperture served to rarefy the air, or to
form the cloud ; and when this was sufficiently expanded,
the machine ascended rapidly to the ceiling. Thus the
discovery was made ; and the reader may imagine the
satisfaction it must have given the inventor." The success-
ful result of this experiment is referred to in a report of the
Academy of Sciences, dated 23 December, 1783, and signed
by several members.
Having returned to their home at Annonay, situated
about 36 miles from Lyons, the Montgolfiers proceeded
to repeat the experiment in the open air. Encouraged
by the success of their efforts, they then constructed large
spherical paper-lined linen bags, one of which having a
diameter of 35 ft. ascended to a height of about 1000 ft.
on 25 April, 1783, and travelled a distance of about three-
quarters of a mile before, the hot air being cooled, it settled
to earth. Another experiment with the same balloon was
repeated in public on 5 June, 1783, and as this really
marks the birth of general interest in aerial navigation,
Cavallo's account of the details is here reproduced :
" On Thursday, 5th June, 1783, the States Vivarais, being
assembled at Annonay, MM. Montgolfier invited them to
see their new aerostatic experiment. An immense bag
of linen, lined with paper, and of a shape nearly spherical
had its aperture, which was on its inferior part, attached to
a wooden frame of about 16 ft. surface, upon which it lay
flaccid like an empty linen bag. When this machine was
inflated, it measured 117 English feet in circumference.
Its capacity was equal to about 23,430 cubic ft. ; and it had
been calculated, that when filled with the vapour proper
for the experiment, it would have lifted up about 490 Ib.
weight, besides its own weight, which, together with that
of the wooden frame, was equal to 500 Ib., and this calcula-
s.
1. A Moluccan fox bat exhibited at the Natural History Museum, South Kensington.
2. A Collard fox bat exhibited at the Natural History Museum, South Kensington.
3. A pteranodon occidentalis from the chalk of Kansas, U.S.A. Model of a restoration
exhibited at the Natural History Museum, South Kensington.
"Flight" Copyright Photos
Types of flying fish at the Natural History Museum, South Kensington. The upper
photograph shows the exocetus cahiensis which inhabits the Atlantic Ocean. The lower
photograph is a specimen of the exocetus spilapterus from the Indian Ocean.
THE COMING OF THE BALLOON 183
tion was found to be pretty true by experience. The bag
was composed of several parts, which were joined together
by means of buttons and holes ; and it is said that two men
were sufficient to prepare and fill it ; though eight men were
required to prevent its ascension when full.
" MM. Montgolfier began the operation of filling the
machine, which was done by burning straw and chopped
wool under its aperture ; and the spectators were told that
this bag would be soon swelled into a globular form, after
which it would ascend by itself as high as the clouds. The
expectations of the whole assembly, the incredulity of some,
the predictions of others, and the confusion of opinion, may
be easily imagined, especially by those who had been
present at experiments of this nature when the certainty of
the success had been well established. The machine,
however, immediately began to swell, it soon acquired a
globular form, stretched on every side, made efforts to
mount, and at last, the signal being given, the ropes were
set free, and the aerostat ascended with an accelerated
motion into the atmosphere ; so that in about ten minutes'
time it had reached the height of about 6000 ft. The dis-
cordant minds of the spectators were instantly brought to
an equal state of silent astonishment, which ended in loud
and unfailing acclamations, due to the genius, and mostly
to the success of Stephen and John Montgolfier.
" The aerostatic machine, after having attained the
above-mentioned elevation, went in a horizontal direction
to the distance of 7668 ft. and then fell gently on the
ground."
Montgolfier's success with his hot-air balloons succeeded
in arousing the scientists of the day to an appreciation
of the necessity for experimenting in a determined way with
hydrogen. Although they were unaware of the common-
place character of what was then called " Mr. Montgolfier's
gas," they had been sufficiently interested to find out by
experiment that it could not possibly be the same thing
as the inflammable air (hydrogen) with which they were
already familiar in their laboratories.
Having remarked that this smoky substance was not
nearly so light as hydrogen, they came to the very natural
conclusion that the use of inflammable air in its place
184 AVIATION
ought to give proportionately better results, and it was
thereupon decided, in Paris, to experiment on a practical
scale. The expenses of such an undertaking being heavy,
a subscription to defray them was opened by M. Faujas
de St. Fond, and the brothers Robert received a contract
to construct a balloon under the superintendence of M.
Charles, a professor of experimental philosophy. In due
course, a ball-like bag (from which shape the term balloon
is derived) was constructed of silk varnished with rubber
solution. The diameter of the balloon was about 13 ft.,
and its weight, together with a stop-cock attached to the
aperture, was 25 Ib. The first attempt at inflation took
place on 23 August, 1783, the hydrogen being generated
from a mixture of iron filings and vitriol contained in " an
odd sort of an apparatus, somewhat like a chest of drawers,
lined with sheet lead, every one of the drawers communi-
cating with a common pipe, to which the stop-cock of the
balloon was adapted."
After working all day and experiencing innumerable
difficulties that will at once suggest themselves to the minds
of chemists, the experimenters only succeeded in inflating
their balloon about one-third full, and it was not until
27 August that it was at last made ready for the public
ascent, which successfully took place in the Champ de
Mars. The balloon rose to an altitude of 3123 ft., and
descended after a voyage of three-quarters of an hour in
a field near Gonesse, about 15 miles away. The lift of
the balloon at the time of its release was 35 Ib., and the
envelope was discovered in a torn condition when picked
up after its descent.
On ii September, 1783, the first balloon having an
envelope of gold-beater's skin was successfully launched.
The substance was suggested by M. Deschamps to the Baron
of Beaumanoir, who had a balloon made of several pieces
of it glued together, so that the finished envelope was about
19 in. in diameter. This was followed by a general craze
for toy balloons, and soon all Paris became more than
familiar with the invention.
In the meantime, the Montgolfiers were engaged in the
THE COMING OF THE BALLOON 185
construction of an air balloon for demonstration before
the Academy of Sciences, which was successfully made on
12 September, 1783, in a private garden belonging to M.
Revillon, a paper manufacturer of Paris, and in all proba-
bility an old friend of the Montgolfiers, who were engaged
in the same trade. Another demonstration took place
before the King and Queen of France on 19 September,
1783, and on this occasion three animals — a sheep, a cock,
and a duck — ascended with the balloon as the first living
passengers.
Thus far no man had attempted to make an ascent,
and it remained for M. Pilatre de Rozier, who publicly
offered himself to be the first adventurer, to have this
distinction. Of the details of the event, which took place on
15 October, 1783, Cavallo gives the following account :
' The accident which happened to the aerostatic machine
at Versailles, and its imperfect construction, induced Mr.
Montgolfier to construct another machine of a larger size, and
more solid. With- this intent, sufficient time was allowed
for the work to be done ; and by the loth October, 1783,
the aerostat was completed, in a garden in the Fauxbourg
St. Antoine. It had an oval shape, its diameter being about
48 ft., and its height about 74. The outside was elegantly
painted and decorated with the signs of the zodiac, with
cyphers of the king's name, fleurs-de-lis, etc. The aperture
or lower part of the machine had a wicker gallery about
three feet broad, with a balustrade both within and
without, about three feet high. The inner diameter
of this gallery, and of the aperture of the machine,
the neck of which passed through it, was near 16 ft.
In the middle of this aperture an iron grate, or brazier,
was supported by chains, which came down from the
sides of the machine. In this construction, when the
machine was up in the air, with a fire lighted in the grate,
it was easy for a person who stood in the gallery, and had
fuel with him, to keep up the fire in the mouth of the machine
by throwing the fuel on the grate through port-holes made
in the neck of the machine. By this means it was expected,
as indeed it was found agreeable to experience, that the
machine might have been kept up as long as the person in
186 AVIATION
its gallery thought proper, or whilst he had fuel to supply
the fire with. The weight of this aerostat was upwards of
1600 pounds.
" On Wednesday, the I5th October, this memorable
experiment was performed. The fire being lighted, and the
machine inflated, Mr. Pilatre de Rozier placed himself in the
gallery, and, after a few trials close to the ground, he desired
to ascend to a great height ; the machine was accordingly
permitted to rise, and it ascended as high as the ropes, which
were purposely placed to detain it, would allow, which was
about 84 ft. from the ground. There Mr. de Rozier kept
the machine afloat during 4 minutes and 25 seconds, by
throwing straw and wool into the grate to keep up the fire :
then the machine descended exceedingly gently ; and such
was its tendency to ascend, that after touching the ground,
the moment Mr. de Rozier came out of the gallery, it
rebounded up again to a considerable height. The intrepid
adventurer, returning from the sky, assured his friends and
the multitude, which had gazed on him with admiration,
with wonder, and with fear, that he had not experienced the
least inconvenience, either in going up, in remaining there,
or in descending : no giddiness, no incommoding motion,
no shock whatever. He received the compliments due to
his courage and activity ; having shown to the world the
accomplishment of what had been for ages desired and
attempted in vain."
In subsequent captive balloon ascents of the same nature
Pilatre de Rozier was sometimes accompanied by a passen-
ger, the first of whom was M. Girond de Villette, the second
being the Marquis d'Arlands. As the result of these
numerous successful experiments the French Academy of
Sciences printed and publicly published a report of them,
and awarded a certain annual prize at its disposal, valued
at 600 livres, to MM. Montgolfier for the year 1783.
Although this most memorable year 1783 was drawing
to a close, it was not destined to pass before the new art
that it had so auspiciously ushered into the world had
culminated in an aerial voyage, which event took place
on 21 November, 1783, when M. Pilatre de Rozier and the
Marquis d'Arlands were again the aeronauts. The balloon
MONTGOLF1ER
1782
"Flight" Copyright Sketch Jrom an old print
A MONTGOLFIER AlR BALLOON OF 1783
The passengers were accommodated in a gallery surrounding the orifice.
THE COMING OF THE BALLOON 187
employed was that in which they had already made their
captive ascent, and the whole weight of the machine
and travellers was between 1600 and 1700 Ib.
According to Cavallo,
' ' The aerostat left the ground at 54 minutes past one o'clock,
passed safely over some high trees, and ascended calmly and
majestically into the atmosphere. The aeronauts having
reached an altitude of about 280 ft. took off their hats
and saluted the surprised multitude. They then rose too
high to be distinguished, so that the machine itself was
scarcely distinguishable. When they rose, the wind was
very nearly north-west, and it is said that the machine in
rising made half a turn round its own axis. The wind drove
them horizontally over the River Seine and over Paris.
They passed between the Hotel des Invalides and Ecole
Militaire and approached St. Sulpice, but as they were rather
low the fire was increased in order to clear the houses, and
in rising higher they met with a current of air which carried
them southward. They passed the Boulevard ; and at last,
seeing that the object of the experiment was fully answered,
the fire was no longer supplied with fuel and the machine
descended very gently in a field beyond the new Boulevard
about 9000 yards distant from the Palace de la Muette,
which distance they ran in between 20 and 25 minutes' time."
Writing to M. Faujas de St. Fond afterwards, the
Marquis d'Arlands refers as follows to one or two of the
incidents en route.
" At this time M. Pilatre said, * You do nothing and we
shall not mount.' ' Pardon me,' I replied. I threw a truss
of straw upon the fire, stirring it a little at the same time,
and then quickly turned my face back again, but I could no
longer see la Muette. Astonished, I gave a look to the
direction of the river. M. Pilatre then said, ' Behold, there
is the river and observe that we descend.' ' Well, then, my
friend, let us increase the fire,' and we worked away. . . ."
As is not infrequently the case in connection with de-
velopments of new movements in England, the news of
the Mont golfiers' experiments failed to arouse any immediate
activity in this country, but in November, 1783, an Italian,
Count Zambeccari, who happened to be in London, made
188 AVIATION
a balloon of oiled silk, 10 ft. in diameter, weighing n Ib.
It was inflated three-quarters full with hydrogen, and
released in public from the Artillery Ground on the 25th
of that month, having been exhibited for several days
previously. It fell at Graffam, near Petworth, in Sussex,
28 miles distant from London, where it was picked up 2 J hrs.
after the ascent.
In the same month of the same year the Journal de Paris
opened a subscription to defray the expenses of constructing
a hydrogen passenger balloon, then being built by the
brothers Robert. This balloon, when finished, had a
diameter of 27 ft., and the total weight, including the car,
was 130 Ib. ; the lifting effect of the hydrogen that it
contained was 604^ Ib. An ascent was made on i December,
1783, M. Charles and one of the Roberts being the aeronauts.
The descent occurred in a field near Nesle, about 27 miles
from Paris. After M. Robert had left the car, M. Charles
made a reascent, and probably attained an altitude of
10,500 ft., at which elevation he suffered from the cold
and also from pain in the ears. The voyage lasted about
33 min., and was concluded by a successful descent in a
ploughed field near the wood of Tour du Lay.
Early in 1784 the Montgolfiers finished the construction
of a large balloon having a diameter of 104 ft., which as-
cended on 19 January from Brotteaux, near Lyons, with
seven passengers. A rent in the envelope forced a rather
hazardous descent some 15 min. after the start, but no
one was hurt. In February of this year a free hydrogen
balloon, unmanned, was launched from Sandwich in Kent,
and was blown across the Channel into France, and in the
same month a new aeronaut, M. Blanchard, destined to
become famous in connection with a similar journey,
made his appearance in Paris. Balloon ascents at this time
were becoming common in France, and four ladies, the
Marchioness and the Countess de Montalembert, the
Countess de Podenas and Mademoiselle de Lagarde, made
an ascent in a captive Montgolfier on 20 May, 1784.
According to a letter dated from Edinburgh 27 August,
1784, and published in the London Chronicle, a Mr. Tytler
THE COMING OF THE BALLOON 189
would appear to have been the first person to ascend in a
balloon in Great Britain. The event is reported to have
taken place on the morning of that day at Comely Garden,
and to have resulted in a journey of about half a mile.
On 15 September of the same year an Italian, Vincent
Lunardi, ascended from the Artillery Ground, London,
with a hydrogen balloon 33 ft. in diameter. The event was
successful, except in so far as the lift of the balloon was in-
sufficient to enable a Mr. Biggin to travel as passenger.
Lunardi made a temporary descent on the common of
South Mimms, where he landed a cat that he had taken as
a companion, together with a dog, and a pigeon ; the
final descent was made near Ware, in Hertfordshire. A
feature of this voyage, which had also characterized some
of those made by Blanchard, was an attempt to manoeuvre
the balloon by means of oars.
The next voyage in England took place on 16 October,
when M. Blarichard made an ascent accompanied by Mr.
Sheldon, professor of anatomy at the Royal Academy.
In the meantime, the Roberts had achieved a voyage of
150 miles in France. On 30 November, 1784, Blanchard
made another ascent in England, and was this time ac-
companied by an American, Dr. Jeffries, who subsequently
attained to still greater prominence by crossing the Channel
with Blanchard on 7 January, 1785.
Of both voyages Dr. Jeffries published his own narrative,
and that relating to the Channel crossing is especially
entertaining. It appears that Dr. Jeffries undertook to
defray the expenses, and in addition bound himself, by an
agreement with Blanchard, to jump overboard in case of
necessity. An aspect of the impending experiment that it
is difficult to appreciate at the present day, was the attitude
of the general public towards the two pioneers. It appears
that busybodies did all they could to persuade Dr. Jeffries
to abandon the attempt, and in the end he had to apply
to the Governor of Dover Castle for assistance to carry out
his plan. January 7 being a fine day, a start was made
at i o'clock, the balloon lifting 30 Ib. of sand ballast, in
addition to the passengers. Half-way across the Channel
190 AVIATION
they had to throw overboard 15 Ib. of ballast, and shortly
afterwards the remainder was jettisoned, together with a
bundle of pamphlets. More pamphlets, together with
various little articles of ornament, also had to be thrown
overboard, and among the latter was a bottle, about which
Dr. Jeffries relates the following curious incident : " After
which we cast away the only bottle we had taken with us,
which, in its descent, appeared to force out a considerable
steam, like smoke, with a hissing or rushing noise ; and
when it struck the water we very sensibly (the instant
before we heard the sound) felt the force of the shock on
our car ; it appearing to have fallen directly perpendicular
to us, although we had passed a considerable way during
its descent."
Even thus the natural laws of gravitation were not
appeased, and after casting away everything they could
lay their hands on, " we began to strip ourselves, and cast
away our clothing, M. Blanchard first throwing away his
extra coat with his surtout ; after which his other coat and
trousers ; we then put on and adjusted our cork jackets,
and prepared for the event." But, happily for them, the
" event " never took place, for just at the last moment the
balloon ascended sufficiently to carry them over the French
coast and deposit them in the forest of Guines, in Artois.
Here the two aeronauts met with a very enthusiastic
reception, and Blanchard was not only presented by the
French Government with a sum of 12,000 livres, with a
pension annexed of 1200 livres per year, but as a perpetual
memorial of this event, the place was to be called by his
name.
This crossing of the Channel may be said to have demon-
strated the application of the balloon to the kind of travel
that has always been more particularly associated with
aerial navigation, and at this point we may leave the
progress of aerostation. The art increased in popularity,
but no very remarkable development took place in the
design and construction of balloons, those made by the
brothers Robert having had, from the first, most of the
essential features of a good aerostat.
CHAPTER XX
THE FOUNDING OF THE SCIENCE OF FLIGHT AND THE
DEVELOPMENTS IN ENGLAND FROM 1809-1893
The toy helicopter — Sir George Cayley's calculations — Henson and
Stringfellow's power-driven models — The Aeronautical Society of Great
Britain — Phillips and the dipping front edge — Maxim's great machine.
THE invasion of the air by static means naturally
reawakened interest in the dynamic side of the
problem, and within a year of the first balloon
ascent the French Academy of Scientists were invited,
in 1784, to witness the ascent of a toy helicopter con-
structed by Launoy and Bienvenu. The device consisted
of two propellers formed by feathers stuck into corks,
which were rotated by means of a spindle operated by a
string that was unwound by a bow.
An English scientist, Sir George Cayley, repeated this
experiment in 1796 with a similar apparatus, a sketch
of which was included in an article that he wrote on Aerial
Navigation for Nicholson s Journal in 1809. It is interesting
to observe that the helicopter or direct -lift ing screw was,
apparently, the first conception of a dynamic flying machine
among most scientists of this period. As a toy it was
successful from the first, but on a large scale it has been
a failure, although there have not been wanting enthusiasts
who have spent time and money on attempts at its per-
fection. It would be out of place here to enter into a tech-
nical examination of the causes that have been uppermost
in preventing success, but there is one point that appears
to have escaped the notice of advocates of the helicopter
principle, which is that the difficulties of navigating the
air would in all probability be as great, if not greater,
with a machine of this type, even supposing the initial
191
192
AVIATION
problem of effecting a vertical ascent into the air to have
been satisfactorily solved.
Twelve years after these experiments, in 1808, a curious thing
happened, which had a very important effect in bringing the
subject of aviation to the fore in England, and incidentally in
establishing Sir George Cayley as the founder of aerodynamic
science. There was a certain Viennese watchmaker, named
Degen, who decided to abandon his trade for the pursuit
of aeronautics, and being imbued with the usual crude
ideas of a flapping-wing machine, he attracted considerable
CALEY
1809-
' ' Flight " Copyright Sketches
Sketches used by Sir George Cayley to illustrate his articles
in Nicholson s Journal in 1809. They represent a helicopter, a
parachute, and an aeroplane with a tail.
attention at that time by appearing in public with a
mechanism of this sort suspended beneath his balloon.
Whatever may have been the effect of these attachments
on the behaviour of the balloon, it is certain that he never
succeeded in lifting himself off the ground by their aid
alone. It happened, however, that a report to the effect
that he had accomplished this feat became current, and
was given publicity in Nicholson's Journal among, other
places. Among those who read and believed the account
were Sir George Cayley and Thomas Walker, both York-
shiremen, and both keenly interested in the subject of
flight, although entirely unaware of each other's work.
THE SCIENCE OF FLIGHT 193
Both were inspired by Degen's reported success to write
treatises on the subject of aviation, but whereas Walker
was mainly concerned with describing a man-operated
flying machine of his own design, Cayley took a much
broader and more scientific view of the whole subject.
Cayley lived in the era of steam. On his horizon the
potency of the engine as the helpmate of man loomed
large. Power-driven flying machines he considered to be
theoretically possible so soon as an engine could be pro-
duced that would develop more power in proportion to its
weight than man was capable of producing by muscular
exertion. He considered that the steam plant of his day
could be made, with certain modifications, to satisfy these
requirements, and although in the light of present-day
knowledge we are aware that it would have been practically
impossible to have achieved success under the circumstances,
this in no way destroys the merit of Cayley 's own apprecia-
tion of the outlook. It is only by following chronologically
and in detail man's attack on some specific problem, like
flight, that we can properly appreciate the enormous
importance of the more famous inventions. Everyone
allows, of course, that the steam-engine revolutionized
civilization, but such statements are regarded as mere
platitudes nowadays, and so we tend to lack sympathy with
earlier points of view. It is because the history of the
conquest of the air throws so many interesting periods on
to the screen that its study is thus full of fascination.
Cayley possessed a mind that would have tackled the
problem of flight had he existed on earth a century before
his time, and it is not difficult to realize with what avidity
an intelligence of this order seized upon the possibilities
of Messrs. Boulton and Watt's engine, nor to sympathize
with the unique satisfaction Cayley must have felt in his
realization that flight was theoretically possible with the
means then available.
Not only did Cayley attempt to give a mathematical
explanation of the action of the inclined flat plate in motion,
but he also observed that birds' wings have cambered
sections, and noted that in many instances the chord of
13
194 AVIATION
a bird's wing in flight is horizontal, so that the front edge
dips. From these data, crude though they were, Cayley
made an estimate of the lift of a cambered plane for a
specific speed ; his figures were more or less in line
with present-day values. He was the first to present aero-
dynamics in this well-ordered form, and there is no doubt
whatever that he thoroughly deserves to be regarded as
the father of the science.
• Although a practical motor-driven, man-carrying aero-
plane was an impossibility in Cayley 's time, for mechanical
reasons, there is little doubt, nevertheless, that had Cayley
been urged by necessity he would have succeeded in de-
monstrating most of the principles of modern flight to the
world at large, for it is, as was subsequently proved by
later 'experimenters, possible to do this without the aid of
an engine. Curiously enough, too, Cayley himself appears
to have been on the threshold of gliding flight, but, like
so many others who have been interested in aviation, he
seems not to have recognized its entire significance. In his
writings it is recorded that he built a large aeroplane,
" large enough for aerial navigation," which would " sail
majestically from the top of a hill to any given point of the
plain below it with perfect steadiness and safety, according
to the set of the rudder, merely by its own weight descending
in an angle of about 8° with the horizon," and that " when
any person ran forward in it with his full speed, taking
advantage of a gentle breeze in front, it would bear upwards
so strongly as scarcely to allow him to touch the ground,
and would frequently lift him up and convey him several
yards together."
In Yorkshire the tradition is that it was either his gardener
or his coachman who tried to pilot Cayley's flyer, and that he
sustained a broken leg for his daring. From the above
references it would scarcely appear as if any -attempt was
made to practise gliding as an art or as if the possibility
of practising flying by means of a glider was realized.
A gust may have occasionally lifted man and machine
well clear of the ground, and one of the descents may, as
seems to be believed in the county, have resulted in an
THE SCIENCE OF FLIGHT 195
accident, but it is very clear from Sir George Cayley 's
own writings that he regarded an engine as a sine qua
non to the furtherance of useful experiments.
This was the point of view apparently of all pioneers up
to the time of Montgomery and Lilienthal, and it is all the
more interesting to reflect that just as in the case of the
balloon, so in the development of the aeroplane would it
have been possible to have constructed a successful glider at
almost any period in the history of man.
Possibly motor-driven machines would have come to pass
no sooner than they have done, but it is nevertheless
instructive to reflect that aeroplane gliders might have
been in use for centuries before any sort of engine was
known. And if the braver spirits of those times had sought
to emulate the soaring feats of birds, there is very little
doubt that a man at the present day would be as much
at home in the air as he is, for example, in \vater. Imagine
for a moment what the present state of the art would have
become if youths of preceding generations had been in
the habit of varying their high-diving achievements into
deep water with similarly bold attempts at launching
themselves into the air from the same rocky eminence
on the rigid pinions of a home-made glider. Very soon
they would have become adepts in the art of control
and manoeuvring, and the more scientific would soon have
learned the trick of making their machines naturally safe.
By to-day we should all be flying as a matter of course.
Cayley himself found out many of these practical points
in design. The rudder to which he refers was a movable
horizontal tail plane, or what we should now call an "ele-
vator," and he appreciated its use as a means of correcting
the variations in the centre of pressure on the main planes.
He also believed that dihedral wings (wings that slope
upwards from the body) and an underhung load constituted
features of natural stability. It would appear, therefore,
as if Cayley was possessed of adequate theoretical and
practical knowledge to build a successful man-carrying
glider, and it is a profound pity that he did not fully realize
the enormous importance of developing his machine along
196
AVIATION
these lines. His own regret was that his machine was
accidentally broken before there was an opportunity of
trying the effect of any propelling apparatus, for, like
every beginner, he had that intense desire to run before
he could walk. In his case, however, this was more ex-
cusable, inasmuch as he was the first to have any plausible
reason for even trying to run at all.
Even as it was, however, Cayley obtained such a thorough
insight into the practical side of the subject as to have in-
" Flight" Copyright Sketch from an old print
Sketch of the aeroplane proposed by Henson in 1842. There are many old prints
still in existence showing- this machine on its way to China and the like. It is interest-
ing to compare the wing- bracing- with that used in what is generally known as the
Antoinette type aeroplane.
vented almost every leading feature that characterizes
the modern aeroplane now in use over a century later. He
suggested the cambered plane, the elevator tail, dihedral
wings, and the ascentric position of the centre of gravity,
which latter, however, is in little favour. Almost the only
important features of the present-day machine that he did
not discuss are the principles of superposed planes, high
aspect ratio, and wing warping.
From Cayley's time, the still undiscovered art of flying
takes on an entirely different aspect, for Cayley's articles
once and for all removed any further excuse for vague and
THE SCIENCE OF FLIGHT 197
visionary ideas. He laid down some very workable theories,
and gave sufficient evidence of their practical value to
make them most decidedly the proper lines for future
development. There was an interval of over thirty years,
however, before anything was done, but in 1842 another
Englishman, W. S. Henson, filed a patent specification for
" the aerial steam carriage," which contained designs for a
monoplane of 4500 sq. ft. surface, and in March, 1843,
Mr. Roebuck moved for leave to bring in a Parliamentary
Bill to incorporate the Aerial Steam Transit Co. It was
from Henson 's patent drawings that the well-known old
print, representing a monoplane in full flight to China, was
prepared.
Henson was a resident of Chard, in Somersetshire, and in
1843 he joined J. Stringfellow, also a resident in the same
place, and together they built models for experimental
purposes. The first was one designed to be operated by a
spring, and the second was a larger model of 20 ft. span,
which was equipped with a small steam plant. In 1847
this large model was taken out on to Bala Downs for a trial,
but proved unsuccessful. A copy of this machine can be
seen at the South Kensington Museum, London, and it is
worthy of inspection, owing to the remarkable similarity
of its appearance with a typical monoplane of the present
day.
In 1848 Henson left England for America, but J.
Stringfellow continued to work alone, and early in the same
year produced a model of his own design. This machine
differed from the Henson design in having tapered wings
of cambered section. Trials were made with it in a large
empty hall measuring 22 yards in length, and the launching
was effected by allowing the model to run along a horizontal
wire. In this way free flights of about half the length of
the room were frequently accomplished, many of them
taking place in the presence of spectators. They are of the
greatest historical importance, being the first actual de-
monstration of dynamic support with a power-propelled
aeroplane, but the technical interest of Stringfellow's
model lies principally in the lightness of the steam plant
198
AVIATION
with which it was equipped, this in itself being quite a
remarkable engineering feat. Thus was demonstrated
the principle that Cayley had teen the first to present
to the public in the form of a logical argument, and a sus-
1343
" Flight" Copyright Sketch
The upper sketch shows a model monoplane constructed by Stringfellow in 1848,
after collaboration with Henson. It was fitted with a small steam-engine, and was
the first power-driven model to make a free flight. It is now exhibited in the
Victoria and Albert Museum. The lower sketch is an illustration of a model triplane
built oy String-fellow and exhibited at the Crystal Palace in 1868. It was fitted with
a light steam-engine, and demonstrations were made in the presence of King" Edward
VII, then Prince of Wales. Its flights were restricted by a suspension wire track,
along which it travelled. Having been bought by Prof. Langley in 1889, it was
removed to America, and is now exhibited in the Smithsonian Museum at Washing-
ton, D.C.
tained flight on the part of a power-propelled aeroplane
having been accomplished, it only remained to develop
the same type of machine on a sufficiently large scale to
carry a pilot. The successful achievement of this end
occupied a period of many years.
Eighteen years after Stringfellow's success, which of
THE SCIENCE OF FLIGHT 199
itself failed to arouse any very marked enthusiasm, pre-
sumably because those who were aware of it were unable
to appreciate its importance, a definite movement was
made toward the encouragement of aeronautics by the
foundation of the Aeronautical Society of Great Britain
in 1866. At this time there was considerable interest in
the subject of ballooning for scientific purposes, due mainly
to the work of James Glaisher, who had made several
ascents in order to investigate the higher atmosphere.
He and a few others were instrumental in founding the
Society, of which he became the treasurer. The Duke of
Argyll was about to publish his book, The Reign of Law,
in which the flight of birds and the possibility of artificial
flight were studied, and it was only natural that he should
be offered the first Presidency of the Society. Other leading
men of the day who supported the movement and became
first Vice-Presidents were the Duke of Sutherland, Lord
Richard Gro^venor and Lord Dufferin. Hatton Turner,
who had just published his famous work, Astra Castra,
was elected to the Council, which included Sir Charles
Bright, William Fairbairn, and several other well-known
engineers. Frederick Brearey was the first Honorary
Secretary.
Of the founder members, perhaps the most prominent
was F. H. Wenham, who read an address on Aerial Loco-
motion at the opening meeting of the Society held at the
Society of Arts on 27 June, 1866. Wenham was an engineer
by profession, and obtained his inspiration to study flight
during a trip up the Nile seven years earlier. It was im-
mediately on the return from this trip, that is to say in
1859, that he really wrote the paper for which he is princi-
pally famous. It can scarcely be said that Wenham really
added much that was original to the knowledge of his
time, but he did what is often more useful in laying em-
phasis on points that were apt to escape attention. In
particular, he urged the importance of recognizing the
advantages of high aspect ratio and superposed planes,
both of which ideas had already found expression in the
Henson and Stringfellow models, but had been ignored
200
AVIATION
in Sir George Cayley's writings. Wenham's active work
was mainly associated with the carrying out of certain
early experiments on the lift and resistance of planes,
under the auspices of the Aeronautical Society.
Among those whom the mere foundation of the Aero-
nautical Society inspired to energetic research in aviation
was Horatio Phillips, then a youth who had just attained
his majority, and had already been making model flyers
for a couple of years or so. As is often the case, however,
"Flight" Copyright Sketch from a photograph
Philips's multiplane, which was tested on a circular track at Harrow in 1893. It had
numerous very thin planes arranged somewhat in the appearance of a Venetian blind.
the effect of this public enterprise by others tended at first
to induce a desire for secrecy in the mind of this young
pioneer, who in 1870 fondly imagined that he was about to
electrify the world with a successful flying machine in the
form of a helicopter. The roseate hue of these earlier
visions gradually faded in the inventor's mind as failure
took the place of success in this particular direction, and
when, having reverted to experiments with model aero-
planes, he was finally led to investigate experimentally
the qualities of cambered sections, he likewise decided
to give the world at large the benefit of his research. His
first effort in this direction was the publication of an article
THE SCIENCE OF FLIGHT
201
in Engineering on 14 August, 1885. From that day
until the year 1900 Mr. Phillips^ kept up a regular corre-
spondence with the journal in question, and nothing that
he deemed of importance was withheld from those who
" Flight " Copyright Drawing
Elevation and plan of Sir Hiram Maxim's aeroplane which
was tried in Baldwin's Park, Kent, in 1893.
might, but seldom did, make better use of the knowledge
than himself.
It will be remembered that Sir George Cayley was the
first to draw public attention to the advantage of cambered
sections, and to notice that they could be used with a
horizontal chord, or in other words with a dipping front
edge. It remained for Horatio Phillips, however, definitely
202 AVIATION
to put this question on a scientific footing by means of his
experiments, and it is certainly with his name that this
feature of modern aeroplane wings ought to be associated,
more particularly as he was distinctly the first to point
out the advantage of having the maximum camber situated
toward the forward edge of the plane instead of in the
centre. Another point that showed how carefully Phillips
had studied his subject was his advocacy of extremely
high aspect ratios.
Putting these various principles into practice, he pro-
ceeded to build a large model multiplane somewhat
resembling a Venetian blind in appearance, with which ex-
periments were conducted on a prepared circular track
at Harrow in the early part of 1893. A report of a successful
flight of this model, unmanned, appeared in Engineering
of 10 March, 1893, and a still more successful experiment,
resulting in a circular flight of 1000 ft., is recorded in the
same journal of 19 May, 1893.
In the same year Sir Hiram Maxim carried out experi-
ments at Baldwin's Park, in Kent, with a very large
machine of 4000 sq. ft. surface, and on one occasion it
broke away from its guide rails and made a short accidental
flight with two of his mechanics on board. It is interesting
to note that this machine was much the same size as that
proposed by Henson in his original .patent, and it is also
instructive to observe that the characteristic arrangement
of its surfaces is diametrically opposed to that of Phillips 's
machine, for whereas Phillips used a great number of planes,
Maxim used very few. Sir Hiram Maxim also carried out
independent experiments on lift and resistance of different
sections, including cambered planes, and had generally
studied various aspects of the problem of flight for several
years before he commenced the construction of his large
machine in 1889.
CHAPTER XXI
SOME PIONEERS ABROAD
THE INVENTION OF THE GLIDER
In France : Penaud — Tatin — Mouillard — Ader — In America : Langley
— Montgomery — In Australia : Hargrave — In Germany : Lilienthal —
The coming of the glider — Pilcher — Chanute — Herring.
A this stage we must transfer our attention once
more to France, but it is a change of scene that
can be made with the less regret inasmuch as
practically the whole of the progress recorded in the previous
chapter was o'riginated and developed in England, and it
represents without doubt the foundation of the science of
flight.
England, having viewed the enthusiasm of France over
the balloon with almost unnatural apathy, seized hold of
the problem of aviation with a characteristically tenacious
grip, and for three-quarters of a century made the subject
her own. Not that France had ignored the art ; on the
contrary, there were those across . the Channel who had
done excellent work, but in reviewing the history of a
development like this it is always essential to temper
strict chronological sequence with due regard to place
as well as time. In these days the effect of distance has
been eliminated so much by the telegraph that a man
can scarcely walk backwards in his own garden but the
Press hear of it, and give the news of his experiment to the
world the next day. Twenty or thirty years ago, however,
daily journalism was of an entirely different character
from what it is at the present time, and there is at any
rate very little evidence that the flight experiments in
one country were in any way widely known to the pioneers
of the same art in another. The contemporary influence of
203
204 AVIATION
individual research is seldom very widespread until the
subject in question has taken sufficient hold upon popular
fancy to ensure a regular dissemination of such news in
the periodicals of the time. And, even when flying became
the talk of the day, it was sufficiently difficult to glean
any sort of intelligent technical information from the
majority of news that appeared in the general Press.
Much that is of undoubted importance took place in
France during the period under review. In 1871 Penaud
hit upon the idea of employing twisted elastic as a motor
for small models, and his ingenious model monoplane of
that date is the prototype of the toys that are so popular
to-day. Merely as a toy, Penaud's invention has been of real
service to the movement, but his models were also of great
value to scientists who wished to make investigations on a
small scale. A little later, in 1879, Victor Tatin drew public
attention to the subject of aviation by making some ex-
periments with a model aeroplane on a circular track in
the Chalais Meudon riding school, and also about this ,
time L. P. Mouillard was engaged on a somewhat similar
line of research. These latter pioneers, however, mainly
take their place on the roll of fame for their contributions-
to aeronautical literature, rather than for their practical
work in the construction of flying machines.
The practical side of the subject is better revealed in
the work of Ader, who experimented in comparative
obscurity behind his fame as an electrical engineer. Ader
built a very remarkable bat -like man-carrying monoplane,
and with this he is said to have achieved, on 9 October,
1890, in the grounds of the Chateau d'Armainvilliers, a
glorified jump of about 50 metres. In itself this was ap-
parently a performance of somewhat the same order of
importance as that achieved later by Maxim.
There is, however, one thing in particular that must
always stand out prominently in connection with Ader's
experiments, to the credit of the inventor and to the credit
of France. The French Government of that day, true to
the characteristics of the race as a society of encourage-
ment, subsidized Ader in the furtherance of his work.
"Flight" Copyright Sketches
1. The "Avion" built by Ader, the noted electrical engineer, in 1890. An attempt to fly this
machine was made in the presence of French Government officials at Sartory in 1897.
2. Maxim's aeroplane with which experiments were made in Baldwin's Park, Kent, in 1893. It
was driven by a steam engine, and on one occasion it broke away from its guide rail and performed
a short free flight.
3. S. P. Langley's No. 5 model tandem-type monoplane, which was flown with a small steam
engine over the Potomac River, U.S.A., in 1806. A man-carrying machine of somewhat similar
•design was built for the American Government in 1903. It was twice disabled on launching, and
the trials were abandoned. The second trial took place at Arsenal Point, near Washington, on
December 8th. On December ijth of that year the Wrights made their first motor-driven flights.
SOME PIONEERS ABROAD
205
Thus assisted, Ader built two more machines, with the
second of which he made an official demonstration before
a committee of army officers at Sartory on 14 October,
1897. The test was to fly round a circular track, and it is
scarcely surprising that the inventor was unable to fulfil
such a severe undertaking. On the other hand, Ader's
machine is said to have risen from the ground and flown
a distance of 300 metres, more or less in a straight line,
before coming to earth. The delegates of the Government
failed to take the broader view that the situation demanded,
" Fljg*f Copyright Sketches
Sketches of some of the experimental kites used by Hargrave in Australia.
Lawrence Hargrave invented the "box-kite" in 1893, ana- advocated the principle as
a means of stabilizing aeroplanes. The early Voisin biplanes of 1907 were built on
box-kite lines.
and their gloomy reports deprived Ader of further financial
aid. It was a severe blow to the patriotic and enthusiastic
Frenchman, who had from boyhood spent his leisure studying
flight in nature and in pondering over the possibilities of
the conquest of the air by artificial means. Moreover, as
is unfortunately often true in such cases, the well-meaning
caution of the authorities who decided Ader's fate exercised
a damping influence on progress generally, for there is a
marked hiatus in the development of flying in France after
Ader's experiments came to an end.
Among the pioneers in the science of aviation it would
be extremely improper not to give Lawrence Hargrave a
prominent place for the work that he accomplished in
206 AVIATION
Australia. His name is best known for his introduction of
the " box-kite " in 1893, but, in spite of the undoubted
practical importance of this invention, which has been
most usefully developed, his earlier experiments in pro-
pulsion are even more interesting.
Once a year, from 1884, if not at more frequent intervals,
Hargrave read a paper, embodying the results of his in-
vestigations, before the Royal Society of New South Wales,
and it is perhaps in part due to the fact that the proceedings
of scientific societies attract relatively little outside at-
tention that Lawrence Hargrave 's remarkable contributions
to knowledge have been so little known.
His first paper of the series bore the unattractive title
" The Trochoided Plane," and its context, at first reading,
is inclined to seem abstruse to a degree. Closer investigation,
however, reveals a remarkably able thesis on the principles
of wave and vortex motion, together with a consideration
of various mechanical means for producing this kind of dis-
turbance in fluids. The point brought out in this paper
was that the action in question — examples of which are
to be found in nature in the sinuous flexing of the body
of a swimming eel and the flapping of a bird's wing — pro-
duces a propulsive force of high efficiency.
Applying his theory to practice Hargrave constructed
a number of very interesting mechanical models, and
ultimately devoted his attention more particularly to
model flapping- wing flying machines. On 3 June, 1885,
he read another paper before the Royal Society of New
South Wales, in which he described and demonstrated
several flapping- wing models driven by elastic, which
made successful flights. These models were extremely
simple in construction and operation. The wings were
pivoted to a fore-and-aft boom carrying a fixed horizontal
plane in end on aspect. About one-third of this plane was
forward of the wings. The wings were operated by con-
necting-rods from cranks, and the essential feature of the
connection, which made the wings " trochoided planes,"
was the attachment of the connecting-rods to the wing
spars by a fork and pin. By this means the plane of the
SOME PIONEERS ABROAD
207
wings remained at right angles to the connecting-rod, and
consequently varied its attitude in space according to the
position of the crank. In other words, a kind of "feathering"
action was produced whereby the chord of the wing obtained
a negative angle during the downstrokes and a positive
angle during the upstrokes, being horizontal at each dead
centre of the crank. The crank shaft was rotated by the
unwinding of a cord from a drum under the tension of an
elastic spring.
HARGRAVE • 1885
"Flight" Copyright Sketch
A model built by Hargrave and successfully flown before the Royal Society of New
South Wales in 1885. It was supported by a fixed aeroplane surface, and propelled
by flapping- wings. The crank motion controlling: the wings was driven by a
stretched elastic band unwinding a cord from a drum. The longest flights were
about 200 ft. Subsequently, models driven by compressed-air engines were built
and flown.
Subsequently, Hargrave built other and more elaborate
models equipped with compressed-air and steam-engines,
and, like other investigators who experienced difficulty
in obtaining a sufficiently light motive power, he spent
much valuable time in the design and construction of
suitable plant.
Fair success attended his efforts, however, for with the
two compressed-air flapping- wing machines he obtained
flights exceeding 350 ft. The longest flight with the elastic-
driven models was a little over 200 ft.
208 AVIATION
In all cases the wings of his models were forward of the
centre of gravity, and were used for propulsion, not for
support.
In the middle of his experiments with steam-engines
in 1893, Hargrave decided that it would be advisable to
see whether a better disposition of the planes could be
arranged, and also as to whether there was any foundation
for the assertion that birds utilized the wind in soaring.
He decided that the expense of constructing a large whirling
table similar to those used by Langley and Maxim was too
great, and thereupon determined that the use of kites would
serve the best means of acquiring the desired data. It was
in this way that the well-known box-kite associated with
Margrave's name came to be invented, and it is interesting
and instructive to note that in making these kites Hargrave
was merely putting into practice the principle of using
superposed planes advocated so strongly by Wenham, with
whose work he was acquainted.
As a result of his experiments with kites, Hargrave
was led to the conclusion that in the construction of a
flying machine the cellular or box-kite formation would
afford the stability and support of a dihedral monoplane
of twice the span in which the dihedral (rise of the wing
tip above the centre) is equal to the gap. This principle
Hargrave communicated to the Royal Society of New
South Wales in a paper read on 5 August, 1896. The idea
found practical expression in the first commercial Voisin
biplane used by Farman and Delagrange eleven years
later in 1907. The Voisin biplane at that date was charac-
terized by its cellular formation, the main planes being
joined by vertical planes in the gap.
From Australia, it will be convenient to transfer our
attention to America, where one of the most interesting
figures in the whole history of the science was working
slowly and laboriously, but with infinite pains and skill,
to accomplish a definite and very useful task, f Samuel
Pierpont Langley was the founder of the science of flight
in America,/ and the early publication of the results of his
experiments, by the Smithsonian Institute in 1891,!
SOME PIONEERS ABROAD 209
the world at large its first real treatise on aerodynamics,
and Langley in particular an undisputed claim to universal
prestige. Others had experimented before on the lift and
resistance of inclined plates, but no one had ever approached
the subject with the same regard to the scientific accuracy
of working that characterized Langley's research. When
he had found out all he could by means of his whirling
table, he set himself to finish his self-imposed task, which
was to demonstrate on a small scale that a power-propelled
model could be built that would fly. This had already,
to a rather limited extent, been achieved by Stringfellow
in England, but there is reason to suppose from Langley's
writings that he was unaware of the fact, for he was scrupu-
lously honourable in referring to the work of others when-
ever he had any knowledge of their accomplishments.
Langley, however, was essentially a type that would work
on in uninterrupted seclusion, and although he mentions
several names' of other pioneers, yet their work does not
appear to have greatly influenced him, and it is even ques-
tionable if it was ever known to him in detail.
The record of Langley's endeavours to build a practical
self-propelled model forms one of the most fascinating
pages in the history of the art, and when at last, on 6 May,
1896, he achieved success, he had indeed accomplished a
great deal for one man. The story of his many intermediate
failures is in itself quite a remarkable example of undaunted
endeavour. Langley's model was a tandem monoplane,
and although this type has not since been popular, the
fact that it was successfully flown must be borne in mind
against the possibility of future development along
these lines. At this point Langley considered that he
had finished his task, but later on he was induced to build
a full-sized machine under the auspices of the American
Government;, and had not the two attempts to launch this
apparatus been attended by mishaps to the launching gear,
it is quite possible that the Langley aeroplane would have
been the first to make a really successful flight.
Both efforts to launch the machine, the first on 7 October,
1903, and the second on 8 December, resulted in failure.
14
210 AVIATION
On both occasions the launching apparatus tripped up the
aeroplane as it left the rail on the top of a large house-
boat, and precipitated it into the water. Although evidently
no fault in the machine, the American Government with-
drew their support, and the aeroplane was never repaired.
On 17 December of that year the Wrights made their
historic flights with their first motor-driven biplane.
There was another pioneer in America, Professor J. J.
Montgomery, whose work is apt to be forgotten, and which
even at the time was very little known or appreciated.
Having commenced experiments in California in 1883 with
a flapping- wing machine, which was unsuccessful, he built
in 1884 three gliders, with one of which he accomplished a
glide of 600 feet. Desiring more particularly to investigate
the principles of equilibrium and control, he constructed a
series of large models, which were tested by dropping
them from a cable stretched between two mountain-tops.
It was the success of these models, which invariably
glided safely to earth, that led him to construct a large
machine, which he took down to the mountains near San
Juan for trial. These experiments were made somewhat
on the same lines as those of Lilienthal, and came to a
conclusion when Montgomery injured his leg by tripping
up in a squirrel hole. As a result of this accident three
pilots, J. M. Maloney, Wilkie, and Defolto, were engaged
to ride the new machines which were put in hand, and with
which exhibition glides were given about the year 1905 in
Santa Cruz, San Jose, Santa Clara, Oakland, and Sacra-
mento. So much confidence had Montgomery in his
machines that he had consented to make the tests by launch-
ing them, with the pilot on board, from balloons.
At first the adjustments were so arranged that the pilot
had very little control, and the machines merely settled
down in the air. With increasing experience, however,
the pilot's powers to manoeuvre the glide were extended.
Unfortunately one of these trials resulted disastrously,
although through no fault of the machine or the pilot.
During the ascent in the 'balloon a guy rope caught in the
framework of the machine and broke an important member.
SOME PIONEERS ABROAD 211
The pilot, Maloney, failed to observe the accident : he
launched the machine, which turned turtle and settled
a little faster than a parachute. Maloney was picked up
unconscious, and died half an hour afterwards, although
the only mark of any kind on him was a scratch from a
wire on the side of his neck. He had descended from an
altitude of 2000 ft., and his death was, therefore, presumably
due to heart failure. It was not this mishap that interfered
with the continuation of Montgomery's experiments, but
one of far more serious importance, for the San Francisco
earthquake occurred just as he was arranging to make
some far from elaborate tests, and naturally distracted
public attention, and particularly public support, from an
undertaking that was so little allied to the immediate
needs of that plucky community.
Apart from his practical experiments, Montgomery
also devoted much thought to the science of aerodynamics,
and in particular to the mathematics of the cambered
plane. At the Aeronautical Congress of 1893 he drew
attention to the cyclic up-current in the vicinity of the
leading edge of a plane in flight by making the following
statement : "A current of air approaching an inclined
surface is deflected far in advance of the surface and ap-
proaching it in a gradually increased curve, reached it at
a very abrupt angle." \j
Gliding, as a recognized branch of flight, originated, ,\
from the point of view of its contemporary influence, in
Germany, where the art was commenced in 1891 by that
brilliant exponent, Otto Lilienthal, whose experiments
are recorded in another chapter. Where Lilienthal's
method of procedure differed so essentially from that of
other experimenters, and that wherein he performed such
a valuable service to the cause, was his early realization
of the necessity of gaining some sort of practical experience
in the air without the use of either complicated or expensive
apparatus. He was, it would seem, practically the first
pioneer to appreciate that the real problem of flight lay far
more in learning to control the machine than in the designing
apparatus that should be capable of dynamic self-support.
212 AVIATION
With his machine adjusted like a life-buoy under his
arms, Lilienthal would launch himself into the air by
running downhill against a head wind, and giving a final
leap from the ground when he felt a sufficient supporting
effect of the wind under the wings. In this way he ac-
complished from the year 1891 actual gliding flights through
the air of several hundred feet in length, and during the
course of his experiments he made thousands of successful
trials of this nature. It is important to remember, in order
to appreciate the significance of Lilienthal's experiments,
that such glides are true flights in principle, and the only
reason they take place in a downward direction instead of
along a horizontal path is because the earth's attraction
is employed, in lieu of a mechanical engine, as the prime
moving force. Lilienthal thus demonstrated a means of
experiencing and investigating the problem of flight that
was within the reach of all who had the little means but
enough leisure to devote to its pursuit. It is significant
that the solution in question might have been discovered
at a much earlier period in the history of man, yet no one
before Lilienthal had apparently realized that gliding con-
stituted the real front door to the practice of flying.
Otto Lilienthal was a scientist as well as an engineer,
and his researches on the lift: resistance ratios of cambered
planes are classic. He was an enthusiast for popularizing
flight, and always tried to inspire youthful minds to take
up the subject by describing how exhilarating the pastime
of gliding is for those who practise it. It was evidently
one of his cherished ideas that the art in question might be
generally taken up by the youth of the country, for he
recognized that nothing would be more likely to further
the progress of flying than to have the rising generation
intimately acquainted with a very pleasing phase of its
technique.
Unfortunately, Otto Lilienthal lost his life in 1896 during
one of his experiments, just at the time when his work was
about to take a turn in a still more interesting direction,
for he had already made some few experiments in power
propulsion when the end came. It has since been recog-
"Flight" Copyright Sketches
1. A tandem-type monoplane glider, designed by Prof. J. J. Montgomery, and successfully flown
by D. Maloney at California in 1905. The initial altitude for gliding was obtained by ascending in
a balloon.
2. The biplane glider designed by Octave Chanute and flown by A. M. Herring in 1896 over the
shores of Lake Michigan, U.S.A. This machine is the prototype of the modern biplane construc-
tion in respect to the bracing of the main planes.
3. The Wright biplane glider as used on the Kill Devil Sand-hills at Kitty Hawk, North
Carolina, U.S.A. Gliding experiments commenced in 1900, and continued until 1903.
Ooserve the pilots' attitudes in the above photographs
seated on the longitudinal boom.
In the upper photograph the pilot is
SOME PIONEERS ABROAD 213
nized that Lilienthal's method of using his machine is
fraught with some danger in gusty weather, and it is com-
monly admitted that previous accidents were only avoided
by his gymnastic skill in the control of his machine. The
vast number of flights that he did accomplish, however,
were of immense value as an encouragement to others,
for if his death damped the ardour of some, the sterling
quality of his work inspired others to continue his work,
among them Pilcher, Chanute, and the Wrights.
The former, a young English engineer, at that time
attached to the experimental department of Hiram S.
Maxim, took up the subject in 1895, and built a machine
of his own design, but somewhat on Lilienthal lines. On two
or three occasions he met Lilienthal in Germany, and made
glides in Lilienthal's own machine. Unfortunately, however,
he, too, met with a fatal accident at an early stage of his
career, although not before he had drawn attention to
several matters of great practical importance, among them
. the disadvantages of a big dihedral angle in side winds,
the difficulty of controlling a machine with an unduly
low centre of gravity, the possibility of towing a glider
as a kite, and the advantage of a wheeled chassis as a means
of relieving the pilot of the weight of his machine when
landing.
Octave Chanute, who, like Lilienthal, was an engineer
by profession, had already retired from the more active
path of railroad construction, in which he had risen to
become one of the leading men of his day, before he seriously
interested himself in the study of aviation. Like Lilienthal,
too, he grasped the importance of gliding flight, and, having
published an article strongly recommending others to pursue
the art, he decided to institute practical experiments, if
not exactly personally, at any rate at his own expense.
He therefore secured the services of A. M. Herring, a much
younger enthusiast than himself, who had previously made
some gliding flights of his own on a Lilienthal apparatus in
1894. This machine Herring rebuilt, and also another on
very different lines, suggested by Chanute himself.
The apparatus was completed in June, 1896, and trans-
214 AVIATION
f erred to a suitable site on the shores of Lake Michigan,
near St. Joseph, for trial.
Chanute 's experiments lasted until September of that
year (1896), when the camping party broke up for the
winter, and were not afterwards renewed, for Chanute
was even then sixty-four years of age, and although at-
tracted to flight with all the fervour of youth, he doubtless
deemed it wise to moderate his personal participation in
such experiences. Moreover, the trials had served their
purpose so far as Chanute was concerned, and their results
coming from such an authority in the engineering world
induced a widespread interest in the subject.
CHAPTER XXII
THE CONQUEST OF THE AIR
Early work of the Wrights — The first long flight — Santos Dumont's tail-
first aeroplane — Henry Farman wins the first Grand Prix — The American
Army contract.
EIENTHAL'S death, regrettable as it was in
itself, had one most significant effect that in
some measure may be said to have placed the coping
stone on his labours. Among those who read the brief
announcement of the fatal accident were Wilbur Wright
and his brother Orville, whose work is described in detail
in another chapter.
They fully recognized the enormous advantages of
gliding as a means of obtaining effective experience with
a minimum of trouble and expense, but they had an idea
that by using a larger machine than Lilienthal's, capable
of being supported at a speed of about 18 miles per hour,
and by selecting a site where winds of this order were
frequent, if not regular, they would be able to vary their
free glides by the use of the machine as a kite. Before
actually drawing out designs, they took very carefully
into consideration the features of the Lilienthal, Pilcher,
and Chanute machines, the result of which was that they
evolved a type of their own that embodied from the first
the principal characteristics of the Wright biplane with
which Wilbur Wright subsequently electrified the world
by his wonderful flights.
Like Chanute, the Wrights went into camp in order to
make their experiments, the site chosen being Kitty Hawk,
North Carolina, a little settlement located on the strip of
land that separates Albemarle Sound from the Atlantic
Ocean. Here they commenced their practical trials in
215
216 AVIATION
the summer of 1900, and Chanute himself, who was one of
their first visitors, stayed a week with them. Their ex-
periments were most successful and highly instructive,
but being carried on well away from the madding crowd,
little reliable information of the work done was brought
to light until Wilbur Wright himself read a paper before
the American Western Society of Engineers, published
in their Journal for December, 1901. In 1902 their gliding
experiments were resumed, and some modifications made
in the machine. So long as they were actually engaged
on their experiments, they very properly resented intrusion
by the general public, and consequently they took every
reasonable precaution to work in seclusion. It thus hap-
pened that their ultimate success, which was to achieve
sustained flight with a power-driven machine, took place
under conditions that gave rise to all sorts of rumours
and doubts affecting thejtruth of this momentous event
in the world's history. It was on 17 December, 1903,
a little more than three "years after the commencement
of their original gliding flights, that, having equipped a
biplane with a petrol engine of their own design and con-
struction, they succeeded in making four free flights from
level ground against the wind. The experiments were
resumed in 1904 with great success, over one hundred
flights being made. Further progress was achieved in
1905, and in that year they brought the control of their
machine to such a pitch of perfection that they could
legitimately claim to have definitely achieved the con-
quest of the air, and to have commenced upon the second
phase of aviation, which may be better described as the
development of flight. ^The following is an interesting
letter from Orville Wright to Patrick Y. Alexander, who
communicated it to the Aeronautical Society of Great
Britain on 15 December, 1905. The letter itself is dated
17 November of that year :
" We have finished our experiments for this year after a
season of gratifying success. Our field of experiment, which
is situated eight miles east of Dayton, has been very unfavour-
THE CONQUEST OF THE AIR 217
able for experiment a great part of the time, owing to the
nature of the soil and the frequent rains of the past summer.
Up to the 6th September we had the machine out on but eight
different days testing a number of changes that we had
made since 1904 ; as a result the flights on these days were
not so long as our own of last year. During the month of
September we gradually improved our practice, and on the
26th made a flight of a little over n miles. On the 3oth we
increased this to 12^ miles, on 3rd October to 15^, on 4th
October to 2o| miles, and on the 5th to 24^ miles. All of
these flights were made at about 38 miles an hour, the flight on
5th October occupying 30 minutes 3 seconds. Landings were
caused by the exhaustion of the supply of fuel in the flight
of 26th and 3oth September and 8th October, and in those of
3rd and 4th October by the heating of bearings in the trans-
mission, of which oil cups had been omitted. But before the
flight of 5th October oil cups had been fitted to bearings and
the small gasoline can had been replaced with one that
carried enough fuel for an hour's flight. Unfortunately, we
neglected to refill the reservoir, and as a result the flight was
limited to 38 minutes. We had intended to place the record
above the hour, but the attention the flights were beginning
to attract compelled us to suddenly discontinue our ex-
periments in order to prevent the construction of the
machine from becoming public.
" The machine passed through all of these flights without
the slightest damage. In each of these flights we returned
frequently to the starting-point, passing high over the heads
of the spectators. ORVILLE WRIGHT."
Thus was the air finally subjected to the motive power
of man's invention by two Americans, very nearly a century
after Cayley had logically demonstrated the plausibility
of such an achievement, and had accurately forecast
many of the features j)i the machine wherewith it was
actually accomplished^ Owing to the desire of the Wrights
to keep certain details of their machine from public know-
ledge, in order that they might negotiate for the sale of
their patents to Governments, their accomplishments
at first met with none of that general appreciation and
public enthusiasm that they deserved and subsequently
received. ; Many were altogether sceptical of engine-pro-
218 AVIATION
pelled flight having been accomplished at all, overlooking
or being ignorant of the bona fides of their integrity that
Wilbur Wright had already given by his addresses to the
American Western Society of Engineers. Again and again
did articles appear in the Press urging the Wrights to come
out of their shell, but they remained firm in their original
decision, and the mystery of silence grew more intense
during a subsequent period of two and a half years that
they were engaged in various negotiations.
In this interval, the star of aviation suddenly moved
once more to France, where Santos Dumont, a Brazilian
long resident in Paris, achieved the first officially observed
flight recorded by the Aero Club of France on 23 October,
1906. This achievement, small though it was in it sett-
lor the flight was really only a long jump of 164 ft. — never-
theless had a most important effect in firing enthusiasm
all over the country, where, as a matter of fact, active
experiment had been in progress for some time.
Captain Ferber, of the French Army, was the first to
take up the subject after the unfortunate termination
of Ader's work in 1890, and his inspiration came, as did
so much that resulted in good work, from the pioneer
Lilienthal. Ferber commenced his own gliding experiments
in 1898, but lack of suitable ground at first prevented
very successful results. Later, in 1901, Ferber obtained
new ideas from Chanute, and commenced experiments
with a biplane, which resulted more satisfactorily. Another
enthusiast in France, interested in the work of Chanute,
was Ernest Archdeacon, who did perhaps more than anyone
to encourage the early stages of flight by founding a fund
in 1903, and in offering the Archdeacon Cup as a prize for
the first officially recorded flight exceeding 25 metres. It
was this prize that Santos Dumont won, on 23 October,
1906, by successfully performing a prearranged flight
under the observation of duly appointed representatives
of the Aero Club of France.
Apart from his financial encouragement, which at all
times has been most generous, Archdeacon deserves also
to be remembered for his personal association with the
THE CONQUEST OF THE AIR 219
practical side of experimental work. He had several
gliders constructed, commencing with the first in 1904,
and in 1905 put into practice an original idea for per-
forming experiments over water by having the machine
towed as a kite by a motor-boat on the Seine. In these
experiments Gabriel Voisin performed the duties of pilot.
Contemporary with these tests, others of a similar character
were conducted by another pilot, who was ultimately
to achieve great fame — Louis Bleriot, the hero of the first
cross-Channel flight.
These experiments took place in 1905 ; in October,
1906, Santos Dumont set the ball rolling by winning the
first prize, as already mentioned ; in November the Daily
Mail offered its famous £10,000 prize for a flight from London
to Manchester ; and early in 1907 Voisin, who with his
brother decided to go in for aeroplane construction on a
commercial scale, had already built two machines of his
own design with which Leon Delagrange and Henry Farman
were diligently experimenting at Bagatelle and Issy.
Although Delagrange was the first in the field by several
months, it was Henry Farman who was the first to make
the flight for which everyone was hoping. It was fully
recognized by all who followed these early experiments
in detail, that while straight-ahead flights were likely to
become more and more general and relatively easy of
accomplishment, the real test of machine and pilot lay in
turning about and in going in all directions through
the wind ; in other words, in the performance of a flight
over a closed course. So important was this achievement
deemed to be that MM. Deutsch and Archdeacon put up
a prize of 50,000 frs. for its accomplishment over a course
of one kilometre in length. This prize Henry Farman won
with his Voisin biplane on 13 January, 1908, and the follow-
ing is a translation of the historical official notice issued
by the Aero Club of France :
' The Grand Prix d'Aviation of 50,000 francs offered by
M. Deutsch de la Meurthe and M. Ernest Archdeacon to the
Aero Club de France, to be awarded to the inventor of a
220 AVIATION
flying machine who shall first accomplish a flight of one
kilometre in a closed circuit without touching ground, has
been officially won to-day, Monday, 13 January, 1908, at
Issy-les-Moulineaux, by Mr. Henry Farman, in his first and
single flight made at 10.15 this morning.
" The trial was officially controlled by the delegates of
the Committee of Aviation of the Aero Club de France,
Comte Henry de la Vaulx, M. Henry Kapferer, and M. Louis
Bleriot. The duration of the flight, according to the time
officially taken by M. H. Kapferer, was i min. 28 sec., and the
average elevation was between four and six metres from
the ground.
" The Committee of Aviation met on the same day, at
4.30 in the afternoon, to enter an official record of the result
in the books of the Aero Club.
" The board of directors of the Aero Club, represented by
M. Deutsch de la Meurthe, Comte Henry de la Vaulx and
M. Georges Bosangon, has resolved to give a banquet in
honour of Mr. Henry Farman in the salons of the Auto-
mobile Club de France on Thursday next, 16 January. At
this banquet the grand gold medal of the Aero Club de France
will be handed to Mr. Farman, and silver-gilt medals to his
co-operators, the firms of Voisin Freres and of Antoinette.
In addition to this prize the firm of Antoinette wins the gold
medal offered by M. Albert Triaca to the builders of the
motor which won the Grand Prix d' Aviation."
It is important to bear in mind, in order properly to
appreciate the relative significance of progress in France
at this date, that the successful flights of the Wrights had
altogether faded from the public's horizon. Two years
had elapsed since the accounts of their great flights had
appeared in the Press, and it requires something more
substantial than memory to last through any such length
of time as this in modern history. The Wrights themselves
kept quiet, although every now and again the Press would
ask them point blank what they thought of the trend of
affairs in the flying world, and even when they did once
again occupy the stage, their acts still took place behind
the curtain.
On 23 December, 1907, the American Army Signal
"Flight " Copyright Sketches
T. Sketch from a photograph illustrating Pilcher's glider " The Hawk" with which he experi-
mented in England in 1896. The above illustration should be compared with that of the Lilienthal
glider.
2. Santos Dumont's tail-first type biplane with which he won the first flight prize (Archdeacon
Cup) on October 23rd, 1936. The prize was for the first officially observed flight exceeding 25 metres.
"Flight" Copyright Sketch
An early Voisin biplane of the type used by Henry Farman and Leon Delagrange in 1907. The
general design is baseu on the principle of the box-kite invented by Lawrence Hargrave in 1903,
and advocated by him, in a paper to the Royal Society of New South Wales in 1906, as a means of
conferring lateral stability on aeroplanes.
THE CONQUEST OF THE AIR 221
Corps invited tenders for army aeroplanes, the purchase
to take place conditionally upon certain tests that were then
regarded, by those whose actual knowledge of what had
been accomplished was limited to the public achievements
in France, as so severe as to be preposterous. The more
interesting and important clauses of this famous document
are as follows : 1
(3) The flying machine must be designed to carry two
persons having a combined weight of about 350 lb., also
sufficient fuel for a flight of 125 miles.
(4) The flying machine should be designed to have a
speed of at least 40 miles per hour in still air, but bidders
must submit quotations in their proposals for costs de-
pending upon the speed attained during the trial flight,
according to the following scale: 40 m.p.h., 100%; 39
m.p.h., 90%; 38 m.p.h., 80%; 37 m.p.h., 70%; 36 m.p.h.,
60%; less than 36 m.p.h. rejected ; 41 m.p.h., 110%; 42
m.p.h., 120%; 43 m.p.h., 130%; 44 m.p.h., 140%.
(6) Before acceptance a trial endurance flight will be
required of at least one hour, during which time the flying
machine must remain continuously in the air without land-
ing. It shall return to the starting-point, and land without
any damage that would prevent it immediately starting
upon another flight. During this trial flight of one hour
it must be steered in all directions without difficulty, and
at all times under perfect control and equilibrium.
(10) It should be sufficiently simple in construction
and operation to permit of an intelligent man to become
proficient in its use within a reasonable length of time.
(12) Bidders will be required to furnish with their pro-
posal a certified cheque amounting to 10% of the price
1 For full text of this historic document readers are referred to Flight,
p. 651, of 14 June, 1913, where also will be found an interesting personal
statement by Lieutenant- Colonel G. O. Squier, who was intimately
associated with its preparation.
For detail aviation history prior to January, 1909 — in which year
Flight was founded — readers should consult the Automotor Journal.
This motoring periodical contained a section devoted to aeronautics for
many years and published the first account of the Wrights' success that
appeared in any English newspaper. The Auto was the parent journal
of Flight, and both papers are still published from the same offices at
44 St. Martin's Lane, W.C.
222 AVIATION
stated for the 40 miles speed. Upon making the award
for this flying machine these certified cheques will be
returned to the bidders, and the successful bidder will
be required to furnish a bond, according to Army Regula-
tions, of the amount equal to the price stated for 40 miles
speed.
CHAPTER XXIII
THE FAMOUS YEAR
The Wrights in France — An hour in the air — Generosity and prizes —
The first pupils — The restart in England — Cody and Roe — The first certifi-
cates— The first Aero Show.
T"N the summer of 1908 Wilbur Wright came to France, his
I brother Orville remaining in America in order to attend
jLto the construction and testing of a machine for the
Army contract . Hiere began, when Wilbur Wright first
came to France, a period of almost ludicrous suspense.
Everyone was so keenly impatient to see this wonderful
man fly that the suppressed excitement often reached
fever heat, as day after day was passed in his methodically
careful preparations.
The chosen site for the experiments was the Hunaudieres
Race-course near Le Mans, and early in August everything
was apparently in readiness. The aviation world was
all expectancy, everyone was waiting to see — they knew
not quite what. It would be difficult indeed, too, to exactly
analyse the mixed feelings induced by Wilbur Wright's
first public flight, which lasted exactly i min. 47 sec., and
cpv^red a distance of a mile and a quarter !
LXhis took place on 8 August, 1908, 'which day, being
a Saturday, gave the public time to discuss the performance
at leisure over the ensuing week-end. On Tuesday, how-
ever, Wilbur Wright macle another little flight, but this
time with a difference. /He rose in the air, and repeatedly
executed figures of eight and other manoeuvres, showing
the utmost control over his machine. , The trial lasted
less than four minutes, but M. Delagrange, who witnessed
it, thus succinctly summed up the situation, " Eh bien.
Nous n'existons pas. Nous sommes battus."
223
224 AVIATION
Few people knew, nor is it even generally known to-day,
that Wilbur Wright was himself to all intents and purposes
learning on his own machine. Although surpassing all
others in his experience of riding the air, nevertheless,
it happened that he was strange to the precise system
of control embodied on his own aeroplane. When, after
their gliding experiments, the two brothers built their
motor-driven aeroplane, they arrived at a point at which
their opinions differed. Each preferred a different arrange-
ment of levers for manipulating the same system of control,
and just before ^Wilbur Wright packed up his machine,
which thereafter remained in its crate during the long
period of negotiations in foreign countries, he had intro-
duced the universally pivoted warping and rudder lever
that characterized all the early Wright biplanes./ This
control he considered to be best suited to his requirements,
but he had not had time to become expert in its use, which
very simple explanation accounts for a great deal that was
often mystifying to the good spectators of Le Mans.
Presently, the scene of operations was, for convenience,
changed to Auvours, and again the progress was slow.
Newspaper correspondents kicked their heels with im-
patience, and to pass the time would hum the following
refrain :
" C'est difficile de voir voler Orville,
C'est bien plus dur de voir voler Wilbur."
It was part of Wilbur Wright's contract with the French
syndicate, of which Lazare Weiller was the head, to make
two flights of 50 kiloms. in one week, with a second person
as passenger or a bag of sand equivalent to a man's weight,
the flights to be made in a wind of at least eleven metres
per second. In consideration of this performance, the
transference of the French patents to the syndicate, and
the building of a certain number of machines, Wilbur
Wright was to receive £20,000.
Each day saw an increase in the length of his flight by
two or three minutes, but even by 5 September his longest
flight was only 20 mins. in duration. Then, like
THE FAMOUS YEAR 225
a bolt from the blue, there suddenly came the news, on
9 September, that Orville Wright had flown for over an
hour at Fort Myer in America. The next news that Wilbur
Wright received was that his brother had met with an acci-
dent on 17 September, and, worse still, that the accident
in question had resulted in the death of Lieut. Self ridge,
who wras a passenger on the machine. This naturally
cast a gloom over matters aeronautical, for since the un-
timely disasters to Lilienthal and Pilcher, flyers of every
degree had seemed to be in charge of a special Providence.
Frequent accounts of machines toppling over during the
inexperienced efforts of embryo pilots were to be heard
on all sides, but so far no one had been killed, or even,
apparently, seriously hurt. Louis Bleriot, for example,
who was most perse veringly trying to develop a monoplane
of his own design, used frequently to break up his machine,
yet he himself always came through unscarred. Orville
Wright, although badly hurt, was reported to be not seriously
in danger of losing his life.
It was after this incident that Wilbur Wright began to
increase the rate of his progress. He had, in fact, only
been waiting for Orville to make the first flight of an hour,
in order that America might have the honour of its
performance within her shores, j On 21 September he
remained in the air for i hr. 31 mm. 254 sec., during which
time he covered a distance of nearly 61 miles. This was
followed by other flights of equal importance, and on several
ascents he [carried passengers, j On two of these latter
occasions he succeeded in completing his contract with
the Weiller Syndicate, for on 6 October he flew for i hr.
4 min. 26 sec. with Mr. Arnold Fordyce, and on n October
carried M. Painleve for i hr. 9 min. 451 sec., thus making
two flights exceeding 50 kiloms. each in the same week.
Shortly afterwards Wilbur Weight also carried as passengers
four members of the Royal Aero Club, the late Hon. C. S.
Rolls, Mr. F. Hedges Butler, Major Baden Powell, and Mr.
Griffith Brewer.
WTiilst Wilbur Wright was making these fine per-
formances at Le Mans, Henry Farman and Leon Dela*
15
3i 25f 21 Sept.
14 20 12 Sept.
10 o ii Sept.
7 24 28 Sept.
5 52 10 Sept.
2 30
226 AVIATION
grange, inspired by what they had seen, gained confidence
to surpass themselves on their own machines. Very soon
they, too, were making flights of appreciable duration,
far exceeding anything that they had accomplished prior
to Wilbur Wright's appearance in France. Progress in
the art during the first nine months of 1908 was phenomenal,
for whereas the year had opened with a circular flight of one
kilometre as a great effort, by the end of September the
following principal flights had been accomplished :
List of principal flights up to 30 September, 1908.
Time. Date.
Order. Aviator. h. m. s. 1908.
1 . Wilbur Wright
2. Orville Wright
3. Orville Wright
4. Wilbur Wright . .
5. Orville Wright
6. Orville Wright
7. Orville Wright .. .. o 57 31 9 Sept.
8. Wilbur Wright . . . . o 54 3^. 24 Sept.
9. Henry Farman . . . . o 43 o 29 Sept.
10. Wilbur Wright . . . . o 39 19 16 Sept.
11. Wilbur Wright .. .. o 36 14^ 5 Sept.
12. Henry Farman . . . . o 35 36 30 Sept.
13. Leon Delagrange . . .. o 29 53^ 5 Sept.
14. Leon Delagrange . . . . o 28 o 6 Sept.
15. Wilbur WT right . . . . 021 43! 10 Sept.
16. Henry Farman . . . . o 20 20 6 July
17. Wilbur Wright . . . . o 19 48f 5 Sept.
18. Leon Delagrange . . . . o 16 30 22 June
19. Leon Delagrange . . . . o 15 26* 30 May
Other flyers in the field at this time included Louis Bleriot,
who was, as mentioned above, diligently pioneering the
monoplane, of which type of machine there was also another
good example, that was originally known as the Gastambide-
Mengin, but subsequently became more famous as the
Antoinette. Esnault Pelterie, who had been so interested
in the Wrights' gliding experiments as to make certain
tests of his own with a view to checking their figures,
had also come to the conclusion that the monoplane was
a more desirable type of machine than the biplane, and,
like Bleriot, he was at that time endeavouring to achieve
success.
Much encouragement from all quarters was being given
THE FAMOUS YEAR 227
to aviation by the creation of valuable prizes, the most
notable of which was a very generous offer by a large
tyre firm, Messrs. Michelin, involving an aggregate sum of
£10,000. Of this £600 per annum was to be available in
the form of an annual prize, during a period of ten years,
for the flight of longest duration, provided that in each
year the flight in question should last twice as long as that
accomplished by the previous winner of the prize. A sum
of £4000 was also set aside as a special prize for a passenger
flight to the summit of the Puy-de-D6me. With prizes
like this to be won, it was little wonder that flying should
grow apace. Almost every available open space in France
was called into requisition as an aerodrome, and machines
of all kinds and descriptions were to be seen " rolling "
about the ground in the initial attempts of their pilots
to ascend. An art that was almost non-existent in January
became the topic of the hour in September, and the end of
the year saw Wilbur Wright, who was easily the winner
of the first Michelin prize, with a flight of i hr. 53 min. 59!
sec. on 18 December, carefully training three Frenchmen —
Paul Tissandier, Count de Lambert, and Lucas Gerard ville —
to fly his machine in the balmy air of Pau. Wilbur
Wright's first Italian pupil was Mario Calderara, a lieu-
tenant in the Royal Italian Navy.
Chilly days ushered in the new year 1909, and although
possibly propitious enough so far as the absence of wind was
concerned, they wrere not conducive to increased enthusiasm
at the various flight grounds, for flying is a cold pastime
at any time, therefore especially so in winter. January
passed uneventfully, but saw much perseverance on the
part of those who meant to see the thing through, and in
February one of the most determined students at that
time, J. T. C. Moore-Brabazon, made some short flights
with a Voisin biplane at Chalons in France. Putting aside
the question of Henry Farman's English descent, Moore-
Brabazon thus obtained the honour of being the first
Englishman to fly. Before the month was out, however,
signs of success began to manifest themselves within our
own shores ; S. F. Cody, flying some 400 yards at Alder-
228 AVIATION
shot on 21 February, with the British Army biplane.
Great credit is also due to the plucky perseverance of A. V.
Roe, who for a year or more past had been trying with
varying success to fly his low-powered triplane.
In preparation for the various proposed flight meetings
the C.A.M. (Commission Aerienne Mixte) published their
general competition rules about this time, and early in
March the Aero Club of France issued their first list of
pilots' certificates (dated 7 January, 1909) to the following
pioneers : L. Delagrange, Santos Dumont, R. Esnault
Pelterie, Henry Farman, Wilbur Wrigth (sic), Orville Wright
Capt. Ferber, L. Bleriot. Truly do the names of these
famous eight deserve to go down to posterity, not alone
because of the curiosity that almost always attaches to
the first in things of this sort, but because these men
thoroughly deserve the distinction of being the real pioneers
of the practical side of the movement. Capt. Ferber, who
stands out less prominently than some of the others as
a pilot, was a leading exponent of the science.
At this point in the history of the movement the Aero
Club of the United Kingdom made their first important
practical move towards the furtherance of aviation, as
distinct from ballooning, by the acquisition of an aero-
drome at Shellbeach, in the Isle of Sheppey. Here Short
Bros, immediately commenced to erect a factory for building
aeroplanes, in their capacity of official engineers of the
Club. Subsequently, this firm acquired a concession to
construct the Wright biplanes in England.
At Pau, the Wright School in France, the pupils con-
tinued to make rapid progress, and considerable en-
couragement resulted from two royal visits ; one on the
part of King Edward VII and the other from King Alfonso
of Spain. Shortly afterwards Wilbur Wright, having by this
time trained some of his pupils to fly by themselves, left
the school in charge of Count de Lambert, in order that he
might attend personally to the manufacture of his biplane.
The absence of Wilbur Wright from the arena thus served
to divide attention more evenly among the different aviation
grounds in France, where almost every day found a new-
ROE • 19O9
" Flight" Copyright Sketches
1. The British-built Roe triplane of 1909.
2. The British-built Cody biplane of 1909.
3. The French-built Antoinette monoplane of 1909.
THE FAMOUS YEAR 229
comer with a new machine. Few of these would-be pilots
had yet learned to fly, and as a matter of fact the first
to do anything sensational during this interim was Santos
Dumont, who succeeded in flying his miniature monoplane
" Demoiselle," which had a span of only 17 ft., a distance
of 2-5 kilom. across country on 8 April, 1909.
It can never be said against this generation that it failed
to encourage aviation once flying had been demonstrated
as an accomplished fact, and not the least pleasing feature
of this particular period was the manner in which the
English branch of the Michelin Tyre Company came for-
ward with the offer of an English Michelin cup valued at
£500, together with a prize of £500, to be given annually
for five years, solely for the encouragement of British
pilots and British constructors. The announcement was
made at the end of March, which month closed with the
holding of the first British Aero Show at Olympia, London.
This exhibition naturally aroused a great deal of interest
among the general public, the majority of whom had
naturally never previously seen an aeroplane, and many
of whom were not a little astonished to find what curious
great machines they were at close quarters.
Early in April, the Daily Mail again came forward
with the offer of £1000 for the first circular mile flight
to take place in Britain by a British subject flying a British
machine. This was the third prize that the Daily Mail had
offered, the first being the famous £10,000 London to
Manchester prize, which few people supposed would ever
be won, and the second was a prize of £500 for the first
cross-Channel flight, which, being initially only open for the
year 1908, had been re-established as a £1000 prize for the
year 1909.
In April, 1909, there must have been well over 100
prizes of one kind and another that had been definitely
offered for specific events. They did not all run into four
figures in English sovereigns, but very often they repre-
sented five figures in francs, and there is no doubt what-
ever that this generosity on the part of wealthy private
people, no less than the enterprise on the part of some
230 AVIATION
progressive companies who saw the prospect of a little ad-
vertisement for their outlay, was of the very greatest service
in encouraging the movement. Many of the more enthusi-
astic spirits among would-be flyers were but poorly en-
dowed with this world's goods, and in this country especially
it was almost impossible to raise funds for private experi-
ments. Fired by the chance of a substantial reward,
however, many pioneers spent their time and their money
freely in their efforts to achieve success.
CHAPTER XXIV
THE CHANNEL FLIGHT
Latham's splendid failure — Bleriot's great success — The Royal Aero
Club's first aerodrome — The first British flight meeting — The end of 1909.
JULY, 1909, was the greatest month of the history of
aviation, for it witnessed the crossing of the Channel
by Bleriot on Sunday morning, 25 July. The event
was not only one of epoch-making importance in itself,
but the incidents associated therewith are of unique in-
terest. Early in the month much excitement was aroused
by definite announcements on the part of various more
or less proficient pilots, that they would compete for the
Daily Mail prize. Principal attention, however, centred
around the preparations of Hubert Latham, who was
the first to make any actual move. Having taken his
Antoinette monoplane to Sangatte during the second
week of the month, he patiently awaited a favourable
day, which did not arrive for more than a week.
His famous first attempt took place on Monday, 19
July, the start being made at 6.20 a.m. When from 6 to 8
miles out from the French coast, however, the engine
began to miss-fire, and ultimately stopped, so that the pilot
was faced with no other alternative than that of descending
on to the water, which, fortunately, was calm. A well-
executed glide terminated in very gentle contact with the
sea and the peculiar construction of the machine, which
was built with very thick wings and a boat -like body,
enabled it to float when partly submerged. Latham
himself did not even get his feet wet, and when rescued
by a French torpedo destroyer, told off for his escort, he
was calmly smoking his inevitable cigarette.
It was a splendid failure, but before it had even ceased
231
232 AVIATION
to be the topic of public conversation, Bleriot suddenly
arrived on the scene, and without delay made his historic
flight. A few days previously he had completed a very
successful cross-country journey of 25 miles between
Etampes and Orleans, and it was probably this achieve-
ment that determined him to try for the great event while
fortune wore a smiling face — for it is not always that the
Fates are favourable to the flyer. He chose Baraques as
a starting-point, and left the French shore at half -past
four on Sunday morning, 25 July, arriving in England
at 12 min. past 5, where he landed in the North-
fall meadow behind Dover Castle. Allowing for the
difference between French and English time, the journey
occupied approximately 40 min., and as the course followed
was far from straight, it is estimated that the speed was
at least 45 miles an hour. One of the interesting minor
points about the flight was that Bleriot lost his way, and
did not land on the spot that he had previously selected
for the purpose ; in consequence, the crowd awaiting
his arrival was disappointed, and the only actual witness
of his arrival was, so far as is known, Police Constable
Stanford, who happened to be on duty in the vicinity.
Hardly had Bleriot achieved success when Latham made
another bid for fortune, and again met with failure ; once
more also was he rescued safely from the waters of the
Channel.
The foregoing events naturally placed all other achieve-
ments in the shade, but the month of July saw the advent
of many new stars in the firmament of night whose sub-
sequent brilliancy in turn attracted the eyes of the world.
It was in July, for instance, that a young French mechanic,
Louis Paulhan, first appeared at Issy with a Voisin biplane
that he had won as a prize in a competition for models. His
first attempts were very modest little jumps, but before
the end of the month he flew from Douai to Arras, a distance
of 13 miles across country, which he accomplished in 22 min.
As the result of this achievement he formally entered his
name as a competitor for the London to Manchester flight —
and this after less than four weeks' experience !
THE CHANNEL FLIGHT 233
One of the first English pupils in France, G. B. Cockburn,
also attracted attention at this time by flying his Farman
biplane at Chalons ; while M. Delagrange, who was, of
course, already famous as a pioneer, commenced at this
period to take lessons from Count de Lambert in the art
of flying a Wright biplane. In England, S. F. Cody ac-
complished a flight of about 4 miles, and there were signs
of future success in the trials made by A. V. Roe with his
triplane on Lea Marshes.
About this time news from America announced the
acceptance by the U.S.A. Government of the Wright
biplane in respect to the Army contracts. In this matter
the Wrights received the sum of $30,000, inclusive of a
bonus of $5000. The tests of the machine were carried
out at Fort Myer drill ground near Washington, D.C.
Towards the latter end of August came the much-antici-
pated Rheims Aviation Week, the Grand Semaine de
Champagne, as it was called in France, of which the most
important event was the first contest for the Gordon-
Bennett Aviation trophy. Among the competitors was
one representative of Great Britain, G. B. Cockburn,
whose longest flight up to that time had been about a
quarter of an hour in duration. Altogether 36 machines
were entered, several, of course, being of the same type,
the Wright, Farman, and Voisin biplanes with the Bleriot,
Antoinette and R.E.P. monoplanes predominating. One
machine came from America, the Curtiss biplane, and with
this Glenn Curtiss succeeded in winning the principal
event, which resulted in placing the custody of the Gordon-
Bennett trophy in the hands of America for the ensuing
year. During this meeting Paulhan came still more promi-
nently to the fore, and Hubert Latham accomplished what
was then regarded as a wonderful altitude flight of 508 ft.
During September, Alec Ogilvie and T. P. Seawright took
delivery of a Wright glider, which had been constructed for
them by T. W. K. Clarke, a pioneer in the British industry,
and with this machine they went down to some hills behind
Eastbourne in order to make preliminary experiments,
pending the arrival of their power-driven machine. The
234 AVIATION
month closed with some rather sensational flights by Santos
Dumont on his miniature monoplane " La Demoiselle,"
and, sad to relate, also with the death of Capt. Ferber,
who was perhaps the most scientific of those actively as-
sociated with the practical side of the movement.
October was an important month from the point of view
of aviation in England, for it marked the beginning of
active proceedings at the Aero Club ground at Shellbeach,
where J. T. C. Moore-Brabazon and the Hon. C. S. Rolls
both made successful flights ; the former on his all-British
Short biplane, with which he entered for and subsequently
won the Daily Mail prize of £1000 offered to the first British
aviator who should fly an all-British machine over a circular
mile. Quite the most sensational event of this period,
however, was again provided in France, where Count de
Lambert flew his Wright biplane from Juvisy round the
Eiffel Tower in Paris one fine Monday afternoon.
Notwithstanding all this extraordinary progress in
flying, few people in England at this time had actually
seen a machine fly, and the greatest possible interest thus
centred in the first aviation meetings to be held in this
country, which took place simultaneously at Blackpool
and Doncaster during October. The Blackpool meeting
was held under the auspices of the Aero Club, and among
the famous pilots who attended were Henry Farman,
Hubert Latham, and Louis Paulhan. Farman's flying
was impressive from its very monotony ; indeed, nothing
could have been better calculated at that time to inspire
public confidence in the stability of aeroplanes than Far-
man's regular circuits of the course. They were accom-
plished at quite a low altitude, the machine being often
barely 8 ft. off the ground. Paulhan exhibited far more
versatility in the handling of the same machine, which
was flown alternatively by these two pilots, but the sen-
sation of the meeting was Hubert Latham's marvellous
flight in a wind that fluctuated, according to the official
anemometer, between 15 and 30 miles an hour.
It was an enthralling performance that held every
spectator spellbound in suspense, for it seemed hardly
THE CHANNEL FLIGHT 235
possible that the pilot and his machine could continue to
fight a wind so violent. Unfortunately, the Blackpool
meeting, and also the Doncaster meeting, where Sommer,
Delagrange, and Le Blon were the principal pilots, were
largely marred by persistent bad weather, so that the less
experienced pilots were unable to come out of their sheds.
Subsequent to the Blackpool meeting, Louis Paulhan
was engaged to give a series of demonstration flights over
the Brooklands motor race-course at Weybridge, where thou-
sands of people in the London district, who had been
unable to attend at Blackpool, took the opportunity of
obtaining their first ocular demonstration of flight from
this already great master of the art. The month of October
closed with J. T. C. Moore-Brabazon winning the Daily
Mail £1000 prize for the first circular mile flight on a British
machine, with C. S. Rolls making a very successful mile and
a half flight, also at the Aero Club's ground at Shellbeach,
on a Wright biplane, and with the appearance of the first
lady flyer, Baroness La Roche, in France.
During November J. T. C. Moore-Brabazon and C. S.
Rolls continued to make progress, and Alec Ogilvie com-
menced a series of successful flights with his Wright biplane
over the Camber sands near Rye. In the middle of this
month the Commission Aerienne Mixte officially passed
the following records as having been established in accord-
ance with their regulations :
Altitude. Count de Lambert, 300 metres.
Speed. Henry Farman, 200 kiloms. in 3 hr. 42 min. 34 sec.
Distance. Henry Farman, 234-212 kilom.
Duration. Henry Farman, 4 hr. 17 min. 53 1 sec.
December saw F. K. McClean, another member of the
Aero Club, successfully flying a Short -Wright biplane at
Eastchurch in the Isle of Sheppey, which ground Mr.
McClean acquired in the vicinity of the Club ground at Shell-
beach, and which subsequently became, through his generous
action, the official Club ground when unexpected incon-
veniences rendered it necessary to quit the Shellbeach
aerodrome.
More British pupils practising in France came to the fore
236 AVIATION
in this month, among them being Mortimer Singer and
Claude Grahame-White. In England, as the result of
Paulhan's successful demonstration, the ground enclosed
by the Brooklands race-track was converted into an aero-
drome, and a few aeroplanes began to take up residence in
the sheds that were there erected.
" Flight" Copyright Photos
1. The fourteen-cylinder Gnome with its fore-and-aft supporting bracket.
2. The seven-cylinder Gnome as mounted on an aeroplane.
CHAPTER XXV
LATTER-DAY PROGRESS
The London-Manchester flight — The second Channel flight — The
Bournemouth meeting — The deaths of C. S. Rolls and Cecil Grace — The
coming of the military flyer.
AL other events in the early part of 1910 were
utterly eclipsed by the winning of the Daily Mail
£10,000 prize, for a flight from London to Man-
chester, by Louis Paulhan on Wednesday and Thursday,
27 and 28 April. The victory was sensational to a degree,
for an earlier competitor in the field was Claude Grahame-
White, who made an unsuccessful attempt on the pre-
ceding Saturday, when he flew his Henry Farman biplane
from Park Royal, on the outskirts of London, to a place
near Lichfield, where he was forced to descend, on account
of engine trouble.
During the night an increasing wind damaged his machine,
and necessitated an immediate return to London for repairs,
which were only just' completed on the same Wednesday
afternoon that saw Louis Paulhan 's biplane of the same
type, which had arrived at Hendon that morning, finally
assembled.
Somewhere about five o'clock in the afternoon, therefore,
both competitors were more or less ready to make an im-
mediate start, but the weather was so unsatisfactory as to
render it a matter of doubt if any attempt would be made
that day. So firmly, indeed, were Grahame-White's
advisers of this opinion, that they allowed him to go to bed,
in order that he might be fresh and fit in the morning.
No sooner had Paulhan put the finishing touches to his
own machine, however, than he decided to make a trial
flight, and having once ascended into the air, he came to
237
238 AVIATION
the conclusion that he would start for the journey to Man-
chester forthwith.
It was at 5.21 p.m. when he first rose from the ground,
and he flew straight over to the L. and N.W. main line,
which he followed as far as Rugby. Passing over this town
at 7.20 p.m., he flew on as far as Lichfield, where he descended
in a field by the Trent Valley station at ten minutes past
eight. He had thus accomplished 117 miles of his journey.
The landing at Lichfield was one of the finest features of
this most remarkable flight.
Flying, as he was, in windy weather, in the dark and in
a strange country, Paulhan suddenly realized that he had
come to the end of his petrol, and that the grourid beneath
him was more or less impossible for descent. He had just
passed over a small field, which seemed to the pilot to be
the only clear space in the neighbourhood, so, without
a hesitation, he turned about and glided down into this
one safe retreat. Many pilots, who might conceivably
have achieved the landing, would have been forced to
finish their journey there and then, for the problem of
reascent called for the exercise of still more skill, the field
being so small, and telegraph wires being in the line of
flight.
At four o'clock the next morning, however, Paulhan
was safely in the air, and by 4.25 a.m. he had reached
Rugeley. Less than an hour later he was passing over
Crewe, and at 5.32 a.m. he alighted at his destination, in
a field at Didsbury, two miles from Manchester, amid an
enthusiastically applauding multitude. Thus was the
Daily Mail prize won at his first attempt, by a man who
was only " rolling " his machine at Issy in the previous
July.
When Paulhan started, Grahame-White was asleep,
but as soon as his camp heard the news he was awakened,
and thereupon decided to make an immediate start. With-
out waiting to test the repairs of his machine, he set off
just before half-past six, when the evening was already
fast drawing in towards darkness. An hour later it was
already too dark to see the way clearly, and at five minutes
LATTER-DAY PROGRESS 239
to eight he had to descend at Roade, after a journey of 60
miles. Before three o'clock the next morning he was aloft
again, but his ill luck with the engine did not desert him,
and he had to come down at Polesworth when only 107
miles of the total journey had been accomplished. Before
he was able to make the necessary adjustments he heard
the news of his defeat, and nothing remained for him but
to conclude his own plucky attempt with a call for " three
cheers for Paulhan " from the surrounding crowd.
With the successful accomplishment of the London-
Manchester flight, aviation had been deprived of its most
valuable prize, and it was, therefore, an event of no little
moment when the Daily Mail announced, at the end of
June, that they would offer another £10,000 for an event
to take place in July, 1911. Full details of this event
were not published at the time, beyond stating that it
would take the form of a thousand miles circular tour ex-
tending over the greater part of England and Scotland and
would occupy a period of about a week.
Prior to the Manchester flight, the event of chief im-
portance in England was the award of the British Michelin
Cup, together with a cash prize of £500, to J. T. C. Moore-
Brabazon, for his flight of 19 miles, which he accomplished
on an all-British Short biplane on Tuesday, i March. The
Hon. C. S. Rolls, who had achieved a somewhat longer
flight within the same period, did not at this time own
a British-built machine.
When Bleriot entered for the cross-Channel prize, which
he won on 25 July, 1909, he omitted to make formal entry
for the Reuinart Prize of £500 that was also available
for the same event. This sum, therefore, coupled with
the further £100 cup offered by the Daily Mail for the
second Channel crossing, rendered it well worth while
making another attempt. To Jacques de Lesseps, the
youngest son of the famous engineer of the Suez Canal,
therefore, is the honour of having won these prizes by a
cross-Channel flight on Saturday, 21 May. He flew from
Les Barraques to a large meadow some distance inland
from the South Forelands Lighthouse. His machine
240 AVIATION
was a Bleriot fitted with a Gnome rotary engine, and his
time for the journey was 37 min. Another entrant for the
Reuinart Prize was the Hon. C. S. Rolls, who, however,
was in no way deterred by the prior success of de Lesseps
from his ambition to be the first Britisher to cross the
Channel. Bad weather prevented his attempt for several
days, and some delays were also caused through engine
trouble. A satisfactory day at last dawned on 2 June, and
at half-past six in the evening Rolls left the British coast
on his French-built Wright biplane. He crossed the French
shore about one and a half miles east of Sangatte at about
a quarter-past seven, and returned to British soil just after
eight o'clock, without alighting in France. Before starting
on his homeward journey, he successfully " posted " a
letter addressed to the Aero Club of France.
Also at the end of June there was held at Wolverhampton
the first meeting confined entirely to British flyers, but
the interest and importance of this event was overshadowed
by the Bournemouth meeting, which took place early in
July. At Bournemouth, the pick of modern pilots com-
peted for a very valuable prize fund, and their achievements
showed what extraordinary advance had been made as
compared with the accomplishments at Blackpool in the
preceding year.
The long-distance flights, as such, were, not specially
remarkable, but a sea flight, which consisted of a journey
from the aerodrome to the Needles and back, was an im-
portant feature of the meeting, and the prize offered in
connection therewith was won by Morane. J. A. Drexel
and Grahame-White also successfully accomplished this
flight, while Robert Loraine, well known as an actor, but then
flying under the name of " Jones," made a plucky if ill-judged
start in stormy weather, and was forced to descend on the
Isle of Wight. Much anxiety was naturally felt at his
absence, but news of his safety was received in due course,
and at a later date, and in more favourable weather, he flew
back again to the mainland.
Special events, such as a slow-speed test, which was
won by the Hon. C. S. Rolls at 25-3 m.p.h., a weight-carrying
LATTER-DAY PROGRESS 241
contest, a starting prize and a prize for alighting, were also
included in the programme. The latter event, which took
place on the second day of the meeting, was so ill-fated
as to result in the death of C. S. Rolls, whose absence from
the arena of flight none have since ceased to regret.
After the Bournemouth meeting a flight of considerable
interest was carried out by J. A. Drexel, who flew his
Bleriot from the aerodrome to the Drexel-McArdle aviation
school in the New Forest. He was accompanied by H.
Delacombe, who made manuscript notes of his observations
en route. Apart from its general interest, this experiment
was in the main performed in order to prove that such a
record would be legible, and that useful observations
of the surrounding country might be made from such
a position by a military officer.
In August, another international meeting took place
at Lanark, in Scotland, which many of the Bournemouth
competitors attended, but as competitions were held
simultaneously at Blackpool, the interest and importance
of these events was divided. Among the outstanding features
of the Blackpool meeting were the ascent of Chavez on
a Bleriot monoplane to an altitude of 5887 ft., and the coast
flights of Robert Loraine and Grahame-White. Some weeks
afterwards, on Sunday, n September, Loraine flew the
Irish Channel, but failed to make a landing on Irish soil
by a matter of yards : both he and his machine, however,
were safely rescued from the water.
The most important Continental event in August was
the Circuit de TEst, an aerial tour organized by Le Matin,
and comprising a series of cross-country flights forming a
circuit from Paris via Troyes, Nancy, Mezieres, Douai,
and Amiens. Eight competitors started and two finished,
Leblanc and Aubrun. Both flew Bleriot monoplanes
fitted with Gnome engines, and Leblanc, the winner,
who secured the £4000 prize, with, in addition, several
special prizes for flights made at the various stopping-
places, occupied 12 hr. i min. i sec. for the journey of 500
miles. Aubrun's time was 13 hr. 31 min. 9 sec.
The realm of flight has been remarkable for the rapicl
242 AVIATION
development of individual pilots, but even the most pro-
gressive were surpassed in boldness by J. B. Moissant,
who, after a phenomenally short apprenticeship, set out
with his mechanic to fly from Paris to London on his Bleriot
monoplane. He left the Issy aerodrome on Tuesday
afternoon, 16 August, 1910, halted at Amiens at 7.30
p.m., where he remained overnight, and flew to Calais
early the next morning. Before noon he had crossed the
Channel and made a safe descent near Tilmanstone, about
seven miles from Dover. The next day he got as far as Sitting-
bourne, where a forced descent was made, owing to a broken
valve rod, and after this was repaired a short flight as far
as Rainham was all that could be accomplished before the
engine again gave trouble. Persistent ill fortune then
dogged his attempts to finish his journey, and other descents
were made at Gillingham, Wrotham, and Kemsing, near
Sevenoaks, before he finally reached the Beckenham
Cricket Ground on Tuesday, 6 September, after an interval
of exactly three weeks !
During September, 1910, the Army manoeuvres in France
gave an opportunity for demonstrating an aspect of the
utility of flight that was always regarded as one of the
most important of its probable fields of definite develop-
ment. The aeroplane in war introduced an unknown
quantity in military operations, and great interest naturally
attached to the possibilities arid limitations of the " new
arm." In France they were not slow to take advantage
of the occasion, and very good work was done of a kind
that certainly aroused favourable comment from others
besides French military experts.
Late in the same month another milestone in the history
of the development of flight was erected, but unfortunately,
over the grave of Chavez, who lost his life while landing
after crossing the Alps. On 29 September, Chavez started
from Brigue to fly across the Alps by way of the Simplon
Pass. In fifty minutes he had flown 35 miles from the
starting-point, and was then above Domo D'Ossola, where
he decided to alight. While effecting the landing he capsized
the machine within a short distance of the ground, and
LATTER-DAY PROGRESS 243
was himself so badly hurt that he died of his injuries.
Doubt enshrouds the cause of this, as of many other acci-
dents, but it is at any rate plausible to believe that after
an effort of this magnitude the plucky pilot was so exhausted
as to have miscalculated the last act of his great achieve-
ment.
In October a new aerodrome was opened at Hendon,
on the outskirts of London, and became the head-quarters
of the Bleriot School in England, and also of the Aero-
nautical Syndicate, which thereupon commenced the com-
mercial manufacture of an original design by H. Barber of
an all-British monoplane known as the Valkyrie. During
the year, Brooklands, which was first used as an aerodrome
by Paulhan for demonstration flights subsequently to the
Blackpool meeting of last year, was also developed into
a well-equipped flight ground, and became the scene of
constant practice on the part of many new-comers. Indeed,
it was the activity at Brooklands that best showed the
true spirit of the movement at this date.
Towards the end of the month three British pilots,
Claude Grahame- White, J. Radley, and Alec Ogilvie,
left for America, in order to compete for the Gordon-
Bennett Cup, which had been won by Curtiss last year.
This event Grahame -White turned into a British victory.
Activity in England then began to centre round the
events for the British Michelin Cup and the Baron de
Forest £4000 prize for the longest flight from England to
any place on the Continent. These events brought forward
with startling suddenness a new pilot in T. O. M. Sopwith,
who after a very short pupilage obtained his certificate,
and put up a flight of over 100 miles on the Brooklands
aerodrome. Almost immediately afterwards he seized
a favourable opportunity to fly into Belgium, thereby
temporarily holding the records for both the Michelin
and de Forest prizes at one and the same time. S. F. Cody,
who had previously flown nearly 100 miles for the British
Michelin Cup, regained his position in the interim, but
four days before the end of the year Alec Ogilvie flew
142 miles over the Camber sands near Rye. This achieve-
244 AVIATION
ment, notable in itself, was the more interesting inas-
much as the engine employed on this occasion was a
new two-stroke N.E.C. motor, on the development of
which a great deal of time and money had been spent
by the manufacturers. Fate made great sport with
chance on the Michelin Cup flights of 1910, for on the
last day of the year Sopwith, who had returned to Brook-
lands, flew 150 miles, and was himself beaten at the eleventh
hour by Cody, who flew 185 miles 787 yards over Laffan's
Plain. By this victory S. F. Cody won a well-merited
success, for none had been more persevering than he in
his development of the aeroplane in England.
The French Michelin Cup, which also closed at the end
of the year, was won by Tabuteau, who flew his Farman
biplane for an approximate distance of 365 miles in 7 hr.
48 min.
Bad weather prevented competition for the de Forest
prize being as keen as it might have been, and indeed the
gales were so severe that, some machines were wrecked
in their sheds at Dover. Another was subsequently de-
stroyed by fire. Cecil Grace, however, at last managed to
make a start, but when he had crossed the Channel he was
forced to descend, owing to the increasing wind. An im-
provement during the afternoon decided him to try to
fly back to England, but during the return passage he lost
his way in the fog and was drowned. In him England lost
another of her best men, whose interest in the movement
extended well into the science as well as the art of flight.
Many others, too, lost their lives this year, often, it is
to be feared, through an over-ambitious anxiety to do great
deeds with a little experience. Few remembered the ex-
ample of the Wrights, who progressed slowly that they
might be sure.
In America especially many phenomenal performances
took place, often on Wright machines, for the Syndicate
controlling the patents at this time decided that their
immediate field of public activity should be concentrated
on demonstration flights rather than manufacture. Among
the pilots retained for this purpose two, who unfortunately
LATTER-DAY PROGRESS 245
lost their lives, were in the habit of electrifying sightseers
with sensational airmanship of an extraordinary order.
Descending, nay, almost dropping from great heights
to get sufficient velocity, these pilots would execute spiral
turns by banking their machines to an excessive angle, and
one came to grief by actually turning over sideways in mid-
air.
In 1911 the great event of the year was the Circuit of
Britain for the second £10,000 prize offered by the Daily
Mail. It was won by Lieut. Conneau, of the French Army,
flying under the name of " Beaumont," after a close and
exciting race with Vedrines, who was also from France.
Many wonderful performances had been made before,
but this was certainly the most wonderful of all, for these
competitors flew daily stages of their circuit in all sorts of
weather, that taxed not only the skill of the pilot, but the
physical and mental endurance of the man. It was, in
fact, a feat comprising so many difficulties, that all who
followed its progress and realized its import recognized
that they were witnessing an effort of altogether ex-
ceptional character. S. F. Cody and J. Valentine also
completed this difficult course within the stipulated time
limit. In so far as its general interest expelled some of
the characteristic apathy of the Englishman to new de-
velopments, it accomplished a good purpose, but so much
did it point to the extraordinary qualities of the pilots
as the main cause of their success, that there was a tendency
in some quarters to regard flying as more than ever a trick
at which the few might excel, but the majority never learn.
From this time, however, the centre of interest gradually
transferred itself from private flying to the military use of
aeroplanes, and in England the chief consideration of those
engaged in the far from prosperous industry was how soon
the Government would undertake the proper equipment
of the Army with British-built machines. The first step
to this end was the establishment of the Royal Flying
Corps in the place of the Air Battalion, and the acquisition
of a large piece of ground at Upavon, on Salisbury Plain,
where was subsequently established a Central Flying School
246 AVIATION
for the final training of naval, military, and civilian pilots
who, having already taken their certificates privately,
were desirous of joining the R.F.C.
Preparations were also started for holding a competition
for military aeroplanes, which thus became the central
feature of the subsequent year, and afforded incidentally
a considerable amount of reliable technical data that
hitherto had not been available.
The Army manoeuvres followed the trials, and afforded
an opportunity for a further important display of
military aeronautics. Unfortunately, two serious accidents
to service monoplanes marred the occasion, and gave rise
to an inquiry by a departmental committee, the report of
which suggested various minor alterations to existing
machines, but in no way condemned the type.
A most valuable technical report was also published
at the end of 1912 by the Government Advisory Committee
for Aeronautics, which was established in April, 1909,
under the Presidency of Lord Rayleigh, O.M., F.R.S., with
Dr. R. T. Glazebrook, C.B., F.R.S., as Chairman. Two
previous reports had been issued, but neither possessed
quite the same direct interest to the practical constructor
as that issued at the end of 1912. The Advisory Committee
is responsible for the initiation of the scale model research
conducted at the National Physical Laboratory, and for
the sanction of the full scale experiments carried out at the
Royal Aircraft Factory now under the superintendence of
Mr. Mervyn 0' Gorman, C.B.
During the summer of 1912 a new phase of flying suddenly
assumed importance through the successful operation of
several hydro-aeroplanes designed to arise and alight on
the water. With the introduction of flying into the Navy,
the hydro-aeroplane was naturally a sine qua non from the
first, and its importance from the manufacturer's stand-
point was soon to be demonstrated by the prevalence of
such machines at the third British Aero Show organized by
the Society of Motor Manufacturers, with the assistance of
the Royal Aero Club, which was held at Olympia during
a week in February, 1913.
-
Hydro-monoplanes getting up speed on the water preparatory to becom
upper picture shows a Deperdussin, and the middle view is of a Nieuport, th
a triple-stepped keel about twelve inches wide ; the lower photograph show
Reproduced from " Flight"
to becoming " unstuck." The
e floats of which have
shows a Borel, which, like
the " Dep.," has flat floats.
PART IV
INTRODUCTION
IN this part of the book will be found a collection of
memoranda that could not properly have been included
in the body of the text. Certain matters of technical
interest have been dealt with in greater detail than would
have been in keeping with the introductory nature of the
other parts ; also, numerical examples of an elementary
character have been added for the benefit of those who
desire to pursue the study of the subject in this direction.
Tables and formulae have been compiled to more than
cover the requirements of those making such calculations,
but they will doubtless be found of general utility to the
technical student.
Needless to say, the assistance of readers who are kind
enough to point out errors and to suggest useful additions
will be very much appreciated by the author.
247
TERMINOLOGY
EVERY specialized subject has its own terminology, and
even when the chosen words are commonplace their
usage is necessarily of a technical character. Although
I have endeavoured to make this book self-explanatory in the
text, it will perhaps be as well if those who now approach the
subject of aviation for the first time familiarize themselves in
advance with certain of the more usual words.
Many French words are at present in common use for things
that might just as well be described in English, and in the text
I have avoided foreign terms as far as possible. Some of them
are given below, however, for general convenience of reference.
As often happens in the early stages of a new science, the seeds
of future confusion are sown by pioneers who choose words
without considering all their current usages. Thus, the term
drift is a term much used in aerodynamics to express resistance.
That it harmonizes with lift (e.g. the lift and drift of a wing) is
the most that can be said for it in this connection. On other
and more serious grounds it should be abandoned in this sense,
for it already possesses a nautical significance implying drifting
with the stream. In this latter meaning also it is much needed
in aeronautical terminology.
The word plane seems beyond salvation ; its usage as a term
descriptive of the main supporting members of an aeroplane is
too deep-rooted to be changed. In the text I have used, as much
as possible, the word wing instead of plane. As the wings of
aeroplanes are not flat but cambered, it is necessary to speak
sometimes of a cambered plane.
The term aerofoil is used instead of cambered plane by some
writers, but is not generally popular. The word aeroplane
essentially belongs to the machine as a whole : it is descriptive
of a class of flying machine that supports itself by its motion in
flight.
Monoplanes and biplanes are merely types in the aeroplane
class. The monoplane has a single pair of wings, like a bird ;
the biplane has two superposed planes. The difference is merely
a question of the arrangement of the supporting surface :
when the wing area is very large it is more usual to dispose it in
two layers, and such a machine therefore becomes a biplane.
248
TERMINOLOGY 249
A glider is an aeroplane without an engine. It flies downhill,
like an aerial toboggan.
In speaking of the subject of aerial navigation at large it is
preferable to use the word aeronautics to imply the entire science.
Aviation relates to the art of flying, and aerodynamics is the
science of the forces created by relative motion in air. It is
thus the science of the aeroplane : which kind of aircraft is the
only machine that is thus far successful in flight.
It is important to distinguish between the aeroplane and the
airship ; the latter floats by the aid of its balloon. The airship
is a dirigible balloon, being able to navigate against the wind :
it is often called a dirigible for short. The present volume does
not deal with this side of aeronautics.
A ground set apart for aircraft is called an aerodrome, but
some early writers have used this term to mean an aeroplane.
Sheds for aircraft are sometimes called by the French word
hangars.
Another French word at present in common use is fuselage,
meaning the girder-like backbone employed in modern aero-
plane design. This member also forms the body of the machine.
The term chassis has such a well-known reference to the motor-
car that it may be said to be an adopted English word. Used in
connection with aeroplanes, it means the undercarriage that
supports the machine on the ground.
French terms that are used in connection with the flight of an
aeroplane include such expressions as vol plane, meaning a
gliding descent with the engine shut off, and vol pique, meaning
a dive, or descent at a very steep angle. When a machine flies
with its tail abnormally low in respect to the head of the machine
it is said to be cabrl. The tail of the machine itself is, in French,
the empennage. Monoplanes usually have a pyramid-like mast
over the pilot's cockpit ; it is called in French a cabane. Bi-
planes sometimes have flaps called ailerons attached to their
main planes for balancing purposes.
The above are the more frequently heard French words
relating to aeroplanes and flying generally, and although they
are avoided as far as possible in the text this reference to them
is made for general convenience of those who may find them
elsewhere.
There is one technical word in particular to which it seems
well to call special attention — efficiency. This term has but one
meaning to the engineer, to whom it represents the ratio of the
useful work done to the energy expended in doing it. Thus,
technically, the only justifiable use of the word is in the form of
a percentage, e.g. 80% efficiency, etc. The sole criterion as to
the technical justification of the use of the word in any particu-
lar case is, therefore, determined by whether or no it is possible
250 AVIATION
to define 100% efficiency. When there is obviously no such
theoretical limit to the relationship to which the term efficiency
has been applied, its use, technically speaking, is improper.
But the ramparts of this exclusiveness have been much bat-
tered. The lay public uses the term in an indefinite sense,
implying a vague merit. Technical writers, and I one of them,
are sometimes guilty of making a convenience of the expression
in connection with the ratios that are not efficiencies in the true
technical sense of the term ; but in this book I have endeavoured
to avoid its use wherever it is not properly justified by the above
definition.
CLUBS AND INSTITUTIONS
^ j ^HE Royal Aero Club (166 Piccadilly) is the representative
I of Great Britain on the International Aeronautic Federa-
tion, which exercises jurisdiction over all matters of sport,
records, etc. It is open to all who are interested and eligible to
join, on the same lines as any other sporting club.
Pilots' certificates are issued by the R.Ae.C., and all who
wish to fly in public must first obtain this certificate. It is
recognized by all other clubs affiliated to the F.A.I.
The R.Ae.C. is also the authority to whom to apply for official
observation of special performances for which it is desired to
obtain a certificate.
The official notices of the R.Ae.C. appear in Flight, which
is sent to members every week.
The Public Safety and Accidents Investigation Committee
was formed by the Royal Aero Club. Representatives of the
Aeronautical Society sit on this committee by invitation of the
R.Ae.C. Communications should be addressed to the Secretary,
Mr. H. E. Perrin, at 166 Piccadilly.
The Aeronautical Society (n Adam Street, Adelphi) is devoted
more particularly to the scientific side of the movement, to the
encouragement of experimental research, and to the organiza-
tion of lectures and discussions. These latter take place once a
fortnight during the session.
Membership is open to all who are interested in the subject,
and ladies are admitted to membership. For those qualified
technically, there is a Fellowship Grade within the membership
of the Society to which members can be transferred, subject to
the approval of the council and the membership generally. The
object of the Fellowship Grade is to confer a technical status on
those elected thereto, in the same way that membership of cer-
tain technical institutions is solely reserved for technically
qualified persons.
The National Aerial Defence Association (n Victoria Street)
was founded in 1913 by the Navy League as a non-party organiza-
tion for influencing public opinion in favour of adequate British
aerial defence. Its object is to support any Government in
power that has a vigorous programme laid down for that purpose,
and to work harmoniously with the R.Ae.C. and Aeronautical
251
252 AVIATION
Society in the promotion of public interest in matters relating
to aeronautics generally. Its policy excludes the purchase of
aeroplanes for the Government on the principle that the pro-
vision of armament is a parliamentary duty.
The Aerial League (104 High Holborn). General propaganda
and, in particular, the organization of popular lectures.
The British Woman's Patriotic League (65 Sinclair Road,
Kensington). General propaganda and the collection of funds
for the development of National Aeronautics.
The Woman's Patriotic Aerial League (25 Denison House,
Vauxhall Bridge Road) . General propaganda and the collection
of funds for the development of National Aeronautics.
The Imperial Air Fleet Committee (104 Shoe Lane, E.G.).
Founded mainly for the purpose of obtaining subscriptions for
the purpose of presenting aeroplanes to the Governments of our
overseas dominions. The first such aeroplane was presented to
New Zealand.
The Society of Motor Manufacturers and Traders (Maxwell
House, Arundel Street, W.C.), representing the Automobile
Industry, organizes and defrays the cost of the Annual Aero
Show, which is held in conjunction with the R.Ae.C. There is
a permanent sub-committee of the S.M.M.T. representing aero-
nautical interests.
BIBLIOGRAPHY
THE following are a few of the books that should be included
in any aeronautical library :
Technical Report of the Advisory Committee for Aeronautics.
Published yearly (commencing 1909) by H.M. Stationery Office
and sold by Wyman & Sons, Fetter Lane, E.G. Contains par-
ticulars of the experimental work conducted at the National
Physical Laboratory and at the Royal Aircraft Factory.
Eiffel's La Resistance de I' Air et V Aviation. Published with
the complement in 1911, by H. Dunod et E. Pinat, 47 Ouai des
Grands-Augustins, Paris. Contains particulars of Eiffel's
experiments at his laboratories in the Champ de Mars and at
Auteuil. English Edition, translated by J. C. Hunsaker, pub-
lished by Constable & Co., London, and Houghton MifHin Co.,
New York.
Bulletin .de Vlnstitut Aerotechnique de I'Universite de Paris.
Published by H. Dunod et Pinat, 47 Quai des Grands-Augustins,
Paris.
Rendiconti delle esperienza e degli studi eseguiti nello stabili-
mento de esperienze e construzioni aeronautiche del genio. Published
by Cav. V. Salviucci, Viale Giulio Caesare N. 2, Roma.
Bulletin de VInstitut Aerodynamique de Koutchino. Published
by the Institution in 1906, 1909, 1911, and 1912. Contains the
records of the researches conducted under the direction of D.
Riabouchinsky.
Stanton's Resistance of Plane Surfaces in a Uniform Current of
Air, and Experiments on Wind Pressure. Published in 1907 and
1908 by the National Physical Laboratory, Bushy House,
Teddington.
Langley's Experiments in Aerodynamics, and The Internal
Work of the Wind. Published in 1891 and 1893 by the Smith-
sonian Institution, Washington, U.S.A.
Alexander See's Les Lois Experimental de V Aviation. Pub-
lished in 1911 by Libraire Aeronautique, 32 Rue Madame,
Paris.
Lanchester's Aerial Flight. Published in 1907 by Constable and
Co., Orange Street, Leicester Square. In two volumes. The
first volume, entitled Aerodynamics, is a treatise on the theory
of motion in air, the lift and resistance of aerofoils, etc. The
253
254 AVIATION
second volume, entitled Aerodonetics, relates more particularly
to experiments with models.
Greenhill's Dynamics of Mechanical Flight. Published in 1912
by Constable & Co., 10 Orange Street, Leicester Square. A
mathematical treatise on the subject, originally delivered in the
form of lectures at the Imperial College of Science and Tech-
nology, in March, 1911.
Bryan's Stability in Aviation. Published in 1911 by Mac-
millan & Co., St. Martin's Street, London. A treatise giving
the form for the mathematical treatment of problems relating
to equilibrium in air.
Duchene's Mechanics of the Aeroplane. Translated by J. H.
Ledeboer and T. O'B. Hubbard. Published in 1912 by Long-
mans, Green, & Co., 39 Paternoster Row. An up-to-date, straight-
forward, and well-arranged introduction to the practical science
of aviation.
Marey's Vol des Oisseaux. Published in 1890 by G. Masson,
120 Boulevard St. Germain, Paris. An investigation of the
movements of birds in flight
Mouillard's L' Empire de I' Air. Published in 1881 by G.
Masson, 120 Boulevard St. Germain, Paris.
Lilienthal's Bird Flight as the Basis of Aviation. Published
in German in 1891. Translated by A. W. Isenthal in 1911.
Published by Longmans, Green, & Co., 39 Paternoster Row,
London.
The Aeronautical Classics. A series of six small books pub-
lished by the Aeronautical Society, n Adam Street, Adelphi.
Edited for the Council by T. O'B. Hubbard and J. H. Ledeboer.
The object of their publication was to preserve in a convenient
form the writings of Sir George Cayley, F. H. Wenham, Thomas
Walker, Francesco Lana, Percy S. Pilcher, John Stringfellow,
and Giovanni Borelli.
Means' Epitome of the Aeronautical Annual. Published in
1910 by W. B. Clarke & Co., 23 Tremont Street, Boston, Mass.,
U.S.A. This volume forms a collection of the more important
articles originally printed in the three volumes of the A eronauti-
cal Annual published in 1895, 1896, and 1897. Edited by James
Means. It contains Lilienthal's own account of his experiments,
also articles by Octave Chanute, Sir Hiram Maxim, Pilcher, and
Langley.
Henry De La Vaulx' Triomphe de la Navigation Aerienne.
Published in 1912 by Jules Tallandier, 75 Rue Dareau, Paris. A
review of all phases of aeronautics, including ballooning, by one
who played an intimate part in their development.
Hildebrandt's Airships, Past and Present. Translated by
W. H. Story. Published in 1908 by Constable & Co., 10 Orange
Street, Leicester Square. Captain Hildebrandt was instructor
BIBLIOGRAPHY 255
in the Prussian Balloon Corps, and his work affords an interest-
ing resume of the progress in military ballooning and the use of
dirigibles up to that date.
Moedebeck's Pocket-book of Aeronautics. Translated by W. M.
Varley. Published in 1907 by Whittaker & Co. A concise collec-
tion of aeronautical data, more particularly relating to ballooning.
The results of the researches at the Gottingen Model Testing
Institution, under the direction of Professor G. Prandtl, are
published in the German periodical Zeit fur Flugtechnic und
Motorluftschiffahrt. Abstracts of the more important foreign
memoranda of this kind are to be found in the Appendices to the
Technical Reports.
Index to certain special articles in Flight that may be needed
for reference in respect to subjects mentioned in this book : —
VOL. V
1913 ' Stability and Control " (A. E. Berriman), p. 34 et seq.
1 Negative Wing Tips " (J. H. Hume Rothery), p. 64
et seq.
' Hydro Aeroplanes " (V. E. Johnson), p. 72 et seq.
' Notes on Machines " (Lieut. Parke), p. 69.
' Flying Experiences " (G. M. Dyott), p. 58, p. 138.
' Stability Devices " * (Mervyn O'Gorman), p. 161 et seq.
1 Monoplane Committee's Report, p. 154.
' Military Aviation " * (Maj. F. H. Sykes), p. 277.
' Wright Patent Decision," p. 300.
' Flying Fish," p. 302.
' Teaching Flying " (L. WT. F. Turner), p. 326.
' Aerial Navigation Act," p. 284.
' Laws of Similitude " * (L. Bairstow), p. 330.
1 Bird Flight " (E. F. Andrews), p. 334.
1912 ' Germany and France, their Air Fleets," p. 1160.
' Engines " * (A. Graham Clark), p. 1178.
' Aviation in India " (C. E. Esdaile), p. 1018.
' Military Trials. Judges' Report," p. 986.
' Elevator Action of Rudder " (Maj. Brocklehurst), p. 853.
' Army Manoeuvres (Official)," p. 851.
' Parke's Dive," p. 787.
' Measurement of Gliding Angle," p. 746.
' Royal Flying Corps," p. 346, p. 371, p. 510.
' Bleriot Control " (E. L. Ovington, pilot), p. 494.
' Wilbur Wright," p. 458.
' The Magnetic Compass " (E. H. Clift), p. 163 et seq.
1 Soaring Flight,"* p. 123.
1911 ' Observations on Bird Flight " (Dr. E. H. Hankin).
* Indicates a paper contributed to the Aeronautical Society or some
other technical institution.
256 AVIATION
PRINCIPAL JOURNALS IN THE FOREIGN
AERONAUTICAL PRESS
FRANCE
L'Aerophile. Official organ of the Aero Club de France.
Fortnightly. Subscription 18 fr. per annum. 35 Rue Francois
ier, Paris (VHP).
L'Aero. Daily. 35 fr. per annum. 23 Bvd. des Italiens,
Paris.
GERMANY
Zeit. fur Flugtechnic und Motorluftschiffahrt. Official organ of
the Imperial Flying Club. Fortnightly. 15 marks per annum.
Publishers : Verlag von R. Oldenbourg, Munich. General Editor :
Ing. Ausbert Vorreiter, Berlin, W. 57, Biilowstrasse 73.
Deutsche Luftfahrer Zeitschrift. Fortnightly. 16 marks per
annum. Publishers: Verlag Klasing and Co., G.m.b.H., Berlin,
W. 9, Linkstrasse 38. General Editor : H. W. L. Moedebeck.
Berlin W. 30, Nollendorfplatz 3.
AMERICA
Aero Club of America Bulletin. Monthly. 3.50 dollars per
annum. 420 W. I3th Street, New York City.
Aeronautics. Monthly. 25 cents per copy. 250 W. 54th Street,
New York City.
Aircraft. Monthly. 2 dollars per annum. 37 E. 28th Street,
New York City.
Aero and Hydro. Weekly. 4 dollars per year. 537 S. Dear-
born Street, Chicago.
CHRONOLOGY
1452-1519 Leonardo da Vinci invented the ornithopter (flap-
ping-wing type), the helicopter (lifting-screw type),
and the parachute.
1670 Francesco Lana designed an airship supported by vacuum
globes.
1782 Montgolfier invented the hot-air balloon.
1783 Rozier made the first balloon ascent.
Robert built a hydrogen gas balloon.
1785 Blanchard crossed the Channel in a balloon with Dr.
Jeffries (7 January).
1804 Laplace recommended French Government to find
funds for balloon research, and Gay Lussac and
Biot were selected to give this recommendation
effect.
1809-10 Cayley wrote his articles on flight and aeroplane design
in Nicholson's Journal.
1821 Green used coal gas in balloons.
1842 Henson and Stringfellow began their investigations.
1848 Stringfellow succeeded in making his large model aero-
plane to fly with a small steam-engine.
1852 Giffard built a dirigible fitted with a steam-engine.
1859 Goddard in charge of French war balloons used in the
campaign against Italy.
1862 Glaisher selected by the British Association to carry out
scientific balloon experiments.
1866 Aeronautical Society founded (12 January).
1868 Aeronautical Society's First Exhibition at the Crystal
Palace.
1874 Penaud introduced the elastic-driven toy aeroplane for
experimental purposes.
British military balloon school established at Chatham.
1884 Renard built "La France/' an electrically propelled
dirigible, and the first to manceuvre in a figure of
eight.
17 257
258 AVIATION
1885 Aeronautical Society's Second Exhibition at the Alex-
andra Palace.
1890 Ader began his flying experiments.
1891 Langley's experiments in aerodynamics published by the
Smithsonian Institute, Washington.
Lilienthal commenced his gliding experiments in Germany.
1893 Hargrave invented the box-kite in Australia.
Maxim made an accidental free flight with his captive
aeroplane.
1895 Pilcher commenced his gliding experiments in England.
1896 Chanute introduced gliding in America.
1900 Wright and his brother built their first glider.
1902 Lebaudy built the first practical military dirigible for the
French Government.
1 903 The Wrights made their first free flight with a motor-driven
aeroplane (17 December).
1906 Santos Dumont won the first flight prize (23 October).
1907 The American Army Signal Corps invited tenders for
army aeroplanes (23 December).
1908 Henry Farman won the Grand Prix with his Voisin
biplane (13 January).
Wilbur Wright commenced flying in France (August).
Flight, first aero weekly in the world, founded (5 Nov.).
First Aero Salon, Paris (December).
1909 Cody began to make successful flights with the British
Army biplane.
First British Aero Show at Olympia (March).
Hubert Latham alighted in the Channel while trying to
fly from France.
Bleriot flew the Channel (Sunday, 25 July).
First Gordon-Bennett race at Rheims won by Curtiss for
America (August).
First British flight meeting at Blackpool (October).
Paulhan gave demonstration flights at Brooklands over
motor track, the ground enclosed by which was sub-
sequently prepared as an aerodrome (October).
J. T. C. Moore-Brabazon won the Daily Mail £1,000 for a
circular mile flight, with a Short biplane (October).
1910 Aero Club of the United Kingdom receives the Royal
prefix (February).
Meeting at Heliopolis, Egypt (February).
J. T. C. Moore-Brabazon won the first British Michelin
Cup, for longest distance, with a flight of nineteen miles
on a Short biplane (March).
CHRONOLOGY 259
1910 Second British Aero Show (March).
London to Manchester flight won by Paulhan (27-28
April).
Jacques de Lesseps flew the Channel (May).
C. S. Rolls flew across to France and returned without
alighting (June).
Bournemouth meeting (July).
Circuit de L'Est (August.)
Robert Lorraine flew the Irish Channel and alighted in
the sea (September).
Aeroplanes at the French Army Manoeuvres (Sep-
tember).
Chavez crossed the Alps, and was killed while alighting
(September).
Hendon aerodrome opened (October).
Second Gordon- Bennett race in America won by Claude
Grahame- White for Britain (November).
T. O. M. Sopwith flew into Belgium.
S. F. Cody won the second British Michelin Cup with a
flight of 185 miles 787 yards on a Cody biplane, with a
Green engine (December).
Cecil Grace drowned in the Channel, having flown into a
fog while returning from France (December).
1911 Capt. Bellenger flew from Paris to Bordeaux (90 kiloms.
in 5 hr. 10 min. net time) (February).
Aeroplane first used in war by Hamilton, who flew
over Ciudad Juarez, while fighting was in progress
between the Mexican rebels and the Royalist troops,
and reported the situation to the latter (February).
Prier flew from Hendon to Paris, non-stop (April).
Paris- Madrid race won by Vedrines (May).
Aerial Navigation Act (June).
European Circuit won by Lieut. Conneau (" Beaumont ")
(June).
Third Gordon-Bennett race held at Eastchurch, and won
by Weymann for America (July).
Circuit of Britain for the Daily Mail £1,000, won by
Lieut. Conneau (" Beaumont "), with Vedrines a close
second. Cody and Valentine also finished the course
within the stipulated time-limit (July).
Fourny flew 720 kiloms. in eleven consecutive hours
(September).
Garros attained 13,943 feet altitude (September).
French Military Aeroplane Trials (October).
The Wrights practise soaring flight in America (October).
260 AVIATION
1911 Cody won the third long-distance British Michelin Cup
(now known as Cup No. i, there having been intro-
duced a second cup by the Michelin firm which is known
as Cup No. 2, for the quickest time over a given course
(October). Cody won the British Michelin Cup No. 2
(October).
1912 British Army Estimates provided a vote of £308,000 for
the Aerial Services (February).
French Army Estimates provided a vote of £880,000 to
be spent on aircraft (February).
Formation of the Royal Flying Corps (March).
Tabuteau flew from Pau to Paris in a single day (March).
Vedrines conducted an electioneering campaign by
aeroplane in France (March).
French Army temporarily suspended the use of monoplanes
on a report by Bleriot respecting top bracing (March) .
Mr. Roger Wallace, K.C., retired from Chairmanship of
the Royal Aero Club and succeeded by Sir C. D. Rose,
Bart. (March).
Appointment of a Public Safety and Accident Investiga-
tion Committee by the R.Ae.C. and the Aeronautical
Society invited to nominate representatives (March).
Miss Harriet Quimby flew the Channel (April).
Corbett Wilson flew the Irish Channel and was the first to
land on the Irish soil (April).
The French Minister of War reviewed twenty-six fully
equipped aeronautical units (April).
Daily Mail inaugurated an expansive scheme of aeroplane
tours about the country in order to arouse popular
interest in flying (May).
Wilbur Wright died from typhoid fever in America (May).
Garros won the Grand Prix of the French Aero Club,
which was flown over the Anjou circuit.
T. O. M. Sopwith won the Aerial Derby, consisting of a
flight round London, organized by the Daily Mail (June) .
H.M. King George V became the patron of the Royal
Aero Club (June).
Hubert Latham killed by a buffalo while big-game shoot-
ing on the Congo (July).
Military Aeroplane Trials on Salisbury Plain (August).
G. de Havilland made a British height record of 9500 ft.
with the Royal Aircraft Factory's biplane B.E. 2.
Paris-Berlin flight by Audemars (August).
Provisional ban on Army monoplanes following fatal
accidents during the Army manoeuvres. A committee
of inquiry appointed to investigate (September).
CHRONOLOGY 261
1912 Aeroplanes and small dirigibles played an important part
in the military manoeuvres (September).
Fourth Gordon-Bennett race held in America and won by
Vedrines for France (September).
Paris Aero Salon (November).
Aeroplanes in the Balkan War (November).
1913 Bieolvucie flew across the Alps (January).
Bider flew from Pau to Madrid (January).
Report on Army monoplanes issued (February).
Fourth Aero Show at Olympia (February).
R.F.C. squadron at Montrose established (March).
Decision of foreign courts in the Wright patent litigation
(March).
Monaco Hydro-aeroplane meeting (April).
Death of Sir C. D. Rose, M.P., Chairman of the Royal
Aero Club (April).
Election of the Marquess of Tullibardine, M.V.O., D.S.O.,
M.P., to the Chairmanship of the Royal Aero Club (May).
Mansion House meeting for Aerial Defence organised by
the Navy League (May).
M. Brindejonc des Moulinais prosecuted under the Aerial
Navigation Acts for flying into England without giving
notice (May).
The British Government offers £5000 as a prize for British
engines (June).
Robert Slack flew from Paris to London (July).
Mr. Joynson-Hicks, M.P., and Mr. Sandys, M.P., disclose
to Parliament the unfavourable result of their in-
vestigations into the state and number of aeroplanes
possessed by the R.F.C. (August).
Cody killed by a fall during a flight on his new biplane
(August).
Commander Felix flies a Dunne biplane from England
to France.
First start of the Daily Mail waterplane race round
Britain (August).
On a second attempt, H. G. Hawker flew from Southamp-
tion via Yarmouth, Scarborough, Aberdeen, Cromarty,
the Caledonian Canal, Oban, and Lame to within
about 18 miles of Dublin, where he met with an accident
that disabled his Sopwith biplane. He was flying with
a six-cylinder Green engine of about 100 h.-p. Starting
at half-past five on Monday morning, he arrived at
Oban on Tuesday afternoon. He was awarded a
consolation prize of £1000.
WORLD'S RECORDS CERTIFIED
:[. Time for a given distance on a closed circuit :
PILOT ALONE.
WITH ONE PASSENGER.
WITH Two PASSENGERS.
Kiloms.
Pilot.
Time.
Pilot.
Time.
Pilot.
Time.
h. m. s.
h. m. s.
h. m. s.
5
J. Vedrines
o I 43$
H. Bier
0 2 58
Ch. Nieuport
0 2 52
O
10
20
30
40
5°
IOO
J. Vedrines
J. Vedrines
J. Vedrines
J. Vedrines
J. Vedrines
J. Vedrines
o 3 28
o 6 56
o 10 32!
o H 3f
o 17 35
o 35 l6!
Legagneux
Legagneux
Legagneux
Legagneux
Legagneux
Legagneux
o 4 24!
o 8 51
o 13 i8f
o 17 44f
o 23 13
o 44 36£
Ch. Nieuport
Ed. Nieuport
Ed. Nieuport
Ed. Nieuport
Ed. Nieuport
Ed. Nieuport
o 5 45
o n 59f
o 17 52£
o 22 44!
o 29 371
o 59 8
!5°
J. Vedrines
0 52 52r
Legagneux
1710
—
—
200
J. Vedrines
1 I0 55
H. Bier
2 3 49
—
—
250
M. Tabuteau
2 7 54
H. Bier
2 39 37
—
—
300
M. Gobioni
2 49 o
—
—
—
—
35°
Gilbert
3 26 16
— •
—
—
400
Gilbert
3 55 27ir
—
—
—
—
45°
Gilbert
4 24 44*
—
—
—
—
500
Gilbert
4 54 6i
—
—
—
—
600
Gilbert
5 52 38
—
—
—
—
700
Fourny
9 34 i
—
—
—
800
Fourny
10 44 45 f
—
—
—
—
900
Fourny
i i 59 9t
—
• —
—
—
IOOO
Fourny
13 I 12
—
—
—
II. Absolute fastest speed for a distance of 5 kiloms. during a closed circuit flight
Speed.
Speed.
Speed.
k p.h.
k.p.h.
k.p.h.
5
J. Vedrines
"•Ir* ""
174-100
G. Legagneux
i35'952
Ed. Nieuport
102-855
III. Absolute greatest distance in a closed circuit :
Distance.
Distance.
Distance.
kiloms.
kiloms.
kiloms.
Fourny
1010-900
Lt. Barrington-
401 "500
Bier
112 "OOO
Kennett
IV. Absolute longest duration in a closed circuit :
Duration.
Duration.
Duration.
h. m. s.
h. m. s.
h. m. s.
Fourny
U 17 57i
Souvelack
4 35 o
H. Oeterich
2410
V. Absolute greatest altitude :
i
Altitude.
Altitude.
Altitude.
metres.
metres.
metres.
Garros
5610
v. Blaschke
4630
v. Blaschke
3580
VI. Distance in a given time :
Distance.
Distance.
Hours.
kiloms.
kiloms.
k
J. Vedrines
45-664
Legagneux
31 "O2O
—
—
J. Vedrines
84-665
Legagneux
66-639
—
—
I
J. Vedrines
1 68 '244
Legagneux
i33'469
—
—
2
Tabuteau
234'43I
P. Mandelli
1 90 '858
—
—
3
Tabuteau
310-281
Leoel
224-850
—
—
4
Gilbert
410*900
—
—
—
—
5
Gilbert
510-000
—
—
—
—
6
P. M.Bournique
490 'ooo
—
—
—
—
7
Tabuteau
522-935
—
—
—
—
8
Fourny
585-200
—
—
—
—
9
Fourny
66 1 '200
—
—
—
—
10
Fourny
744-800
—
—
—
—
ii
Fourny
820-800
—
—
—
—
12
Fourny
904-400
—
—
—
—
13
Fourny
980*400
-r-
—
—
—
F.A.I. UP TO 31 DEC., 1912
WITH THREE PASSENGERS.
WITH FOUR PASSENGERS.
WITH FIVE PASSENGERS.
Pilot.
Time.
Pilot.
Time.
Pilot.
Time.
h. m. s.
-
h. m. s.
h. m. s.
P. Mandelli
Busson
o 3 48
o 6 i6f
Busson
Busson
0 3 34
078
—
P. Mandelli
o 12 3
Busson
o 14 o£
—
—
P. Mandelli
o 17 37
—
—
—
P. Mandelli
o 23 n
—
—
—
—
P. Mandelli
o 29 47
—
—
—
—
P. Mandelli
o 56 33
—
—
—
—
Speed,
k.p.h.
Speed,
k.p.h.
1
idelli
1 06 "029
Busson
87-251
-
Distance.
Distance.
kiloms.
kiloms.
!delli
I lO'OOO
Busson
25740
Duration.
Duration.
Duration.
h. m. s.
h. m, s.
h. m. s.
ch
i 35 o
A. Faller
I 1 8 0 Molla
i 6 48i
Altitude.
Altitude.
metres.
metres.
tnig
I 1 20
Verschaeve
596
Distance.
kiloms.
_
idelli
106*029
—
—
—
—
THE ROYAL FLYING CORPS
THE development of aeronautics for service purposes in
England commenced with experiments with captive balloons
at Aldershot in 1862. Military ballooning was formally
introduced into the Army in 1879, a balloon school being estab-
lished at Chatham. In the next year the 24th Company of
Royal Engineers was selected for special instruction in aero-
nautics.
The Royal Flying Corps was formed in 1912 and absorbed the
Air Battalion that formerly represented military aviation in
England. While the Royal Flying Corps represents what is in
some respects a distinct arm of the service, its administration
comes partly under the War Office and partly under the Ad-
miralty. Thus there are two wings, military and naval, but the
personnel of both wings is supplied from a Central Flying School,
which trains soldiers, sailors, and civilians in flying and in the
mechanics of aviation. From the Central Flying School, officers
and men are drafted into the Naval or Military Wing as the case
may be.
Experimental scientific work is conducted under the general
direction of the " Advisory Committee," which was appointed
by the Prime Minister in 1909 and sits once a month. The
research itself is partly carried out on a model scale at the
National Physical Laboratory, and in part on a full scale at the
Royal Aircraft Factory.
A standing sub-committee of the Committee of Imperial
Defence and known as the " Air Committee " has been appointed
by the Army Council to co-ordinate action in dealing with
questions that arise in connection with the Royal Flying Corps.
The present chairman of this committee is Brig.-Gen. D. Hender-
son, Director of Military Training.
The following abstracts from various official documents give
the more important items of information that may be required
for reference.
From the official memorandum on the formation of the
Corps :
" The necessity for an efficient aeronautical service in this
country not less urgent than in the case of the other Powers.
264
THE ROYAL FLYING CORPS 265
" The organization should be capable of absorbing and utiliz-
ing the whole of the aeronautical resources of the country.
" While it is admitted that the needs of the Navy and Army
differ, and that each requires technical development peculiar to
sea and land warfare respectively, the foundation of the require-
ments of each service is identical, viz. an adequate number of
efficient flying men. Hence, though each service requires an
establishment suitable to its own special needs, the aerial branch
of one service should be regarded as a reserve to the aerial branch
of the other. Thus in a purely naval war the whole of the Royal
Flying Corps should be available for the Navy, and in a purely
land war the whole corps should be available for the Army.
" At present no military requirements beyond those of the
Expeditionary Force, which are of urgent importance, are being
dealt with.
" The purposes for which aeroplanes will be required in land
warfare are as follows :
(a) Reconnaissance.
(b) Prevention of enemy's reconnaissance.
(c) Intercommunication.
(d) Observation of artillery fire.
(e) Infliction of damage on the enemy.
" Having considered the organization of the aeronautical
forces of other Powers, so far as information is available, the
establishments laid down below would appear to provide a
suitable organization for the Expeditionary Force of 6 divisions
and i cavalry division, viz. :
" Head-quarters.
" 7 Aeroplane Squadrons, each providing 12 aeroplanes.
" i Airship and Kite Squadron, providing 2 airships and 2
flights of kites.
" i line of communication flying corps workshop.
" For the future, the Military Wing of the Royal Flying Corps
comprises all branches of aeronautics, including aeroplanes,
airships, and kites. All these are required for the same purpose,
and should work in close co-operation.
" The total number of aeroplanes required for the seven
squadrons of the military division will be eighty-four.
" To provide the war establishment for the seven Aeroplane
Squadrons that are considered necessary for our Expeditionary
Force, 182 officer flyers and 182 non-commissioned officer flyers
are required.
" It is considered that the minimum number of trained flyers
should be two per aeroplane. Of these one should be an officer,
266 AVIATION
and, in the case of one-seated machines, both should be officers.
For purposes of calculation, however, one officer and one non-
commissioned officer flyer are allowed. The number of flyers
required on this basis is shown below :
" 7 Squadrons. — Officers : commanders, 7 ; 3 sections, 84 ;
total, 91. Non-commissioned officers : sergeants, 7 ; 3 sections,
84 ; total, 91.
" In addition, it is necessary to provide a Reserve to meet
casualties, and it is considered that this should be on a basis of
loo per cent for six months' wastage.
" The total number of flyers required will therefore be :
Officers N.C.O.'s
For war establishment and 7 squadrons . . 91 91
Reserve . . . . . . . . . . 91 91
Total 182 182
" Conditions of Service. — Entry to the Royal Flying Corps as
officers will ultimately be confined to those who have graduated
at the Central Flying School. These officers will be drawn from
(a) officers of all branches of the naval and military services, and
(b) civilians. The rank and file will consist of warrant officers,
petty officers, non-commissioned officers and men transferred
from the Royal Navy or the Army, and also of men enlisted
directly into the Royal Flying Corps, either on a regular or a
special reserve basis. At the conclusion of their training they
should be eligible to be appointed either (a) for continuous
service in the Naval or Military Wing of the Royal Flying Corps,
or (b) to the permanent staff of the Flying School, or (c) to the
Royal Flying Corps Reserve.
" The period of appointment in the case of officers, who elect
for continuous service with the Naval or Military Wings of the
Royal Flying Corps or at the Central Flying School, will normally
be 4 years.
" Civilian candidates for appointment to the Royal Flying
Corps as officers apply in the first instance to the Commandant
of the Central Flying School, quoting the number of their Royal
Aero Club certificate.
" Great importance is attached to the primary condition that
every member of the Royal Flying Corps shall incur a definite
obligation to serve in time of war either for naval or military
purposes in any part of the world.
"It is essential that all combatant officers in the Royal
Flying Corps should be practical flying men.
" For the present, military officers and civilians who are
candidates for commissions in the Royal Flying Corps first have
THE ROYAL FLYING CORPS 267
to obtain their Royal Aero Club certificate, and on being accepted
as members of the Royal Flying Corps receive the sum of £75.
" Naval Wing. — The Naval Flying School at Eastchurch will,
for administrative purposes only, be provisionally under the
orders of the Captain of H.M. ship Actezon, and all officers and
men will be borne on the books of the Actaon.
" Central Flying School. — The Central Flying School is estab-
lished on Salisbury Plain, on ground south-east of Upavon.
" There are three courses at the Central Flying School during
the year, each course lasts 4 months.
" The training includes :
(i) Progressive instruction in the art of flying,
(ii) Instruction in the general principles of mechanics and
the construction of engines and aeroplanes,
(iii) Instruction in meteorology,
(iv) Training in observation from the air.
(v) Instruction in navigation and flying by compass,
(vi) Training in cross-country flights,
(vii) Photography from aircraft,
(viii) Signalling by all methods,
(ix) Instruction in types of warships of all nations.
" The R.F.C. Reserve. — The officers of the Reserve of the Royal
Flying Corps are divided into two classes ; the officers of the
First Reserve are required to produce on the first day of each
quarter satisfactory evidence that they have performed during
the previous quarter flights amounting to an aggregate of nine
hours in the air, and including one cross-country flight of not less
than one hour's duration. These conditions are subject to
modification in particular cases. Flyers of the Second Reserve
need not be required to carry out any flights, but are available
for service in the Royal Flying Corps in time of war.
" Royal Aircraft Factory. — The existing Army Aircraft Factory
has been renamed the ' Royal Aircraft Factory.' It will be ad-
ministered by the War Office. It should carry out the following
functions :
(1) The higher training of mechanics for the Royal Flying
Corps.
(2) Repairs and reconstruction for the Royal Flying Corps.
(3) Tests with British and foreign engines and aeroplanes.
(4) Experimental work.
(5) The existing work in the manufacture of hydrogen, and
generally meeting the requirements of the Airship and
Kite Squadron.
(6) General maintenance of the factory at present.
268 AVIATION
" Pay. — Abstracts from Army Order :
Ordinary Pay
Squadron Commander . . . . 253.
Flight Commander . . . . 175.
Flying officer . . . . . . 12s.
" The order continues that His Majesty the King's will and
pleasure is that :
" Flying pay may be issued during leave on the same condi-
tions as staff pay. Subject to this, flying pay may be issued
continuously to officers serving in the aeroplane squadrons and
to officers who are qualified aeroplane flyers serving in the air-
ship and kite squadron. Officers serving in the airship and kite
squadron who are not qualified aeroplane flyers shall receive
flying pay at the above rate for each day on which they make an
ascent by airship or kite.
"2. The pay of other officers shall be as follows :
" Commanding Officer, Military Wing, £800 a year, with
quarters. Medical Officer, pay and allowances of his rank.
" If the medical officer is required to fly, the Army Council
shall decide what emoluments he shall receive with reference to
the special circumstances of the case.
"3. The pay of the Staff of the Central Flying School shall be
as follows :
Commandant . . £1,200 a year, with quarters.
Instructor. . . . The emoluments laid down for a Squad-
ron Commander in Article i.
Quartermaster. . As laid down in Article 138 of the Pay
Warrant.
"4. Officers shall be seconded for service in Our Royal Flying
Corps from the date they satisfactorily complete such period of
instruction at the Central Flying School as Our Army Council
may prescribe. Whilst undergoing this period of instruction they
shall receive the regimental emoluments of which they were
previously in receipt, and shall in addition receive flying pay at
the rate of 45. a day.
"5. The period of an officer's service in Our Royal Flying
Corps, shall, subject to his remaining fit for flying duties, be
4 years, but it may be prolonged at the discretion of Our Army
Council.
" 6. Officers appointed from civil life to Our Special Reserve
of Officers for service in Our Royal Flying Corps shall, whilst
under instruction at the Central Flying School, be considered as
on probation, and shall receive regimental pay at the rates
appointed for infantry officers of Our Special Reserve of Officers,
together with flying pay at the rate laid down in Article 4.
Their period of service shall be as laid down in Article 5. On the
THE ROYAL FLYING CORPS 269
satisfactory completion of the period of instruction prescribed
by Our Army Council their commissions may be confirmed and
they shall then be graded as flying officers. They shall there-
after be eligible to receive while employed on flying duties the
emoluments laid down in Article I, except when performing the
quarterly flying test referred to in Articles 7 and 8. They shall
also be eligible to receive an outfit allowance of £40 under the
conditions prescribed for other officers of Our Special Reserve of
Officers.
" 7. Officers who are not serving continuously in Our Royal
Flying Corps shall form the Reserve of Our Royal Flying Corps.
The officers of this Reserve shall consist of two classes. , Officers
of the First Reserve shall be required to perform a quarterly
flying test to be prescribed by Our Army Council. Officers who
do not perform a quarterly flying test shall form the Second
Reserve of Our Royal Flying Corps.
"8. Officers appointed to Our Special Reserve of Officers for
service in Our Royal Flying Corps who are serving in the First
Reserve shall in consideration of their holding themselves liable
for service with Our Navy or Army at home or abroad, and of
the performance of the quarterly test, receive in place of the
gratuity of £20 issued to other officers of Our Special Reserve of
Officers an annual gratuity of £50 payable under conditions to
be prescribed by Our Army Council. Officers of Our Regular
Army of the First Reserve of Our Royal Flying Corps shall
receive for such number of days as may be found necessary
(regard being had to weather conditions) for the proper per-
formance of their test, the regimental emoluments of their rank,
together with flying pay at the rate laid down in Article I.
" 9. Officers of the Second Reserve shall receive no special
emoluments as such.
" Warrant Officers, Non-commissioned Officers and Men
" 10. The daily rates of pay of men enlisted or transferred to
serve in the Military Wing of Our Royal Flying Corps shall be
as follows : Warrant officer, 95. ; sergeant, 6s. ; first-class air
mechanic, 45. ; second-class air mechanic, 2S.
" They shall in addition be eligible to receive flying pay at the
rate of 45. or 2S. a day, according to their flying proficiency under
such conditions as may be laid down by Our Army Council.
Warrant officers and others serving in the airship and kite
squadron shall, unless they are qualified aeroplane flyers, receive
flying pay at the rate of 2S. a day for each day on which they
make an ascent by airship or kite.
" ii. Warrant officers, non-commissioned officers and men of
Our Royal Flying Corps Special Reserve shall receive pay and
flying pay at the same rates and under the same conditions as
270 AVIATION
under Article 10, when employed on Army duty. Whilst under-
going an enlistment instruction in flying at the Central Flying
School, they shall draw the rates of pay laid down in Article 10,
and in addition flying pay at the rate of is. a day.
" 12. Warrant officers, non-commissioned officers and men,
other than those serving continuously in Our Royal Flying
Corps, shall, if performing the quarterly tests to be prescribed by
Our Army Council, be granted annual gratuities as follows :
" (a) Whilst serving with the colours, £10.
" (b) Whilst serving in Our Army Reserve, or in Our Special
Reserve, £20.
" Warrant officers, non-commissioned officers and men serv-
ing in Our Army Reserve or Our Special Reserve who do not
engage to perform the quarterly test to be prescribed by Our
Army Council, shall be granted a gratuity of £10. The condi-
tions and method of issue shall be determined by Our Army
Council.
"13. Army reservists shall not, in addition to the gratuities
payable under Article 12, be entitled to pay under Article 1199
of the Pay Warrant, and warrant officers, non-commissioned
officers and men of Our Royal Flying Corps Special Reserve shall
not be eligible to receive recruits' bounty, training bounty, or
non-training bounty.
" Gratuities and Special Pensions
"14. Officers who are :
(a) Members of Our Royal Flying Corps,
(b) Members of Our Special Reserve of Officers (Royal
Flying Corps),
(c) Undergoing a private course of instruction, having
previously been selected by Our Army Council for
military flying work,
(d) Undergoing a course of instruction at the Central Flying
School,
shall if injured on flying duty, be eligible for gratuities and
pensions under the conditions and at the rates laid down in the
Pay Warrant for officers who have been wounded in action.
" In the event of death within 7 years as the result of injuries
so received, pensions, etc., may be awarded to the officer's widow
and children or other relatives, under the conditions applicable
to the case of officers killed in action or dying of wounds received
in action.
"15. Warrant officers, non-commissioned officers and men of
Our Royal Flying Corps, or of Our Royal Flying Corps Special
Reserve, discharged in consequence of injuries received on flying
duty shall be eligible for pensions under the conditions and at
the rates laid down for their respective ranks in the Pay Warrant
in the case of men discharged for wounds received in action.
THE ROYAL FLYING CORPS 271
" In the event of death within 7^years as the result of injuries
so received, pensions and compassionate allowances may similarly
be awarded to the widow and children of a warrant officer, non-
commissioned officer, or man."
"Army Estimates, Aviation Vote
" The total provision for the above services made in the
1912-13 Estimates compares with that made in 1911-12, as
follows :
1912-13 1911-12
Xj A>
Establishment of Army personnel for
aeronautical work . . . . . . 25,000 20,000
Premiums to officers gaining pilots' cer-
tificates . . . . . . . . . . 3,ooo
Staff of new school . . . . . . 5,ooo
Aeroplanes, stores, and materials for
factory and school . . . . . . 161,000 85,000
Buildings, including Army share of school
buildings . . . . . . . . 38,000 26,000
Land for school . . . . . . . . 90,000
322,000 131,000
Less Admiralty contribution to general
expenses of school . . . . . . 14,000
308,000 131,000
Increased provision . . . . £177,000 "
" Excluding provision for land, the sums taken in 1913-14
compare with those taken in 1912-13 as follows :
1913-14 1912-13
K> KJ
Establishment of Army personnel, in-
cluding Special Reserve and premiums
for pilots' certificates 150,500 28,000
Staff of school 18,500 5,000
Aeroplanes, mechanical transport, stores,
and materials . . . . . . . . 285,000 161,000
Buildings, including Army share of school
buildings . . . . . . . . 72,000 38,000
526,000 232,000
Less Admiralty contribution towards
school 25,000 14,000
Net provision 501,000 218,000
Increase . . . . . . . . 283,000 '*
" Provision (not included in the above figures) has also been
made for guns for the attack of aircraft."
MILITARY TRIALS, 1912
ABSTRACTS FROM THE OFFICIAL REPORT
" s^\RDER of importance. — The Judges' Committee placed the
I ^requirements called for in the competition in the following
^•^ order of importance, and assigned value to them accordingly:
Speed, including flexibility of speed, climbing, gliding, landing,
view, starting ; communication between passenger and pilot,
and dual control ; sound construction throughout, interchange-
ability of parts, and compactness and convenience of handling.
No competing aeroplane had a silenced engine, and, therefore, the
difficulty of measuring relative efficiency in this particular did
not enter into the awards. The low position in the above list
given to sound construction is due to the fact that those aero-
planes which were considered in the awards all complied generally
with the broad requirements in this respect. The difficulty of
judging accurately the capability of an aeroplane to face rough
weather is so great that, in spite of its supreme importance, it
was considered unwise to allot a high value to it. The Judges'
Committee, however, included this kind of stability among other
impressions of general excellence which they formed during the
course of the trials, and to which due weight was given.
" Order of Merit Obtained. — Ten of the competing aeroplanes
were placed by the Judges' Committee in order of merit as
follows :
1. Cody biplane (British), No. 31.
2. Deperdussin monoplane (French), No. 26.
f Hanriot monoplane (French), No. I • • i F 1
3' I Maurice Farman biplane (French), No. 22 i ^Uc
r Bleriot tandem monoplane (French), No. 4 > E .
•*" i Hanriot monoplane (French), No. 2 . . J "
i Deperdussin monoplane (British), No. 21 . .
7. j Bristol monoplane (British), No. 14
Equal.
' Bristol monoplane (British), No. 15
10. Bleriot Sociable monoplane (French), No. 5.
" Certain of these aeroplanes did not fulfil some one of the
requirements called for, but all were considered to be efficient
machines. The standard of excellence attained by several of the
competing aeroplanes brought them very close together in the
272
MILITARY TRIALS, 1912 273
final assignment of positions in the order of merit, although their
particular merits were of a widely varying nature. The Judges'
Committee were unanimous in the selection given above.
" The Awards. — The Army Council, on the recommendation
of the Judges' Committee, have awarded the following prizes in
connection with the Military Aeroplane Competition.
Prizes open to the world :
First prize, £4000, to S. F. Cody, for Cody biplane (British).
Second prize, £2000, to A. Deperdussin, for the Deper-
dussin monoplane (French), No. 26.
Prizes open to British subjects, for aeroplanes manufactured
wholly (except the engine) in the United Kingdom :
First prize, £1000, to S. F. Cody.
"As no other British aeroplane completed all the tests, the
two second prizes will be withheld, but the three third prizes of
£500 each are awarded to :
British Deperdussin Co., for Dep., No. 21.
British and Colonial Co., for Bristol monoplane, No. 14.
British and Colonial Co., for Bristol monoplane, No. 15.
' The following entrants, whose aeroplanes were submitted to
all the tests, will receive £100 in respect of each aeroplane :
M. Ducrocq, for Hanriot monoplanes (French), Nos. I and 2.
Aircraft Co., for Maurice Farman biplane (French), No. 22.
L. Bleriot, for Bleriot monoplanes (French), Nos. 4 and 5.
A. V. Roe, for Avro biplane (British), No. 7.
ANALYSIS OF THE PERFORMANCES
The accompanying tables contain data relating to the eleven
machines that went through the Military Trials. A detailed
report of the tests was published in Flight at the time of the event.
The dimensions of the machines are approximate only, but an
attempt has been made to include the more interesting figures.
The supporting area includes the tail area where that member is
of the lifting type. In the case of the Cody, which has a large
load-carrying elevator in front and only a very small horizontal
fin on each of the rudder plates behind, the elevator has been
included. In other cases, the elevator area is not included in the
supporting surface.
The rating of the engines sometimes varies considerably from
the power they are known to develop and the calculations have
thus been based on values that are believed to be approximately
accurate. The engine powers are not, however, based on actual
tests of the engines in question.
18
274 AVIATION
The machines were weighed during the trials and the weights
stated in the tables are, therefore, accurate figures. The weight
in flight comprises the weight of the pilot and passenger, which
was in all cases made equal to a load of 350 Ib. In addition,
there is the weight of fuel and oil carried during the three hours'
flight. This amount had to be adequate for a flight of 4^ hours'
duration, in most cases it slightly exceeded that amount. The
weight in flight given in these tables includes such surplus, and,
therefore, differs by that amount from the figures given in the
official report.
It is interesting to observe how uniformly the different
machines work out to a common weight per unit of power when
empty. It might be supposed that the structure could be
regarded apart from the engine, but the figures tend to show
that the aeroplane represents a complete unit in respect to weight
for power, and that within the limits of common practice
modern aeroplanes weigh about 15 Ib. per h.p. available. Two
comparatively heavy machines are the Avro biplane and the
Maurice Farman biplane. The Cody biplane is about i Ib. per
h.p. heavier than the monoplanes. It had an engine of 120 h.p.
as compared with the 60 h.p. engines on the Bleriot monoplanes.
As the load carried in flight varied within narrow limits, the
weight per h.p. in flight is thus also fairly constant, the
Avro biplane and the Maurice Farman biplane again being the
heaviest machines per unit of power.
The wing areas varied widely and the wing loading in the
table is, of course, calculated on the total weight in flight. The
gliding angle was measured by an apparatus carried on board the
machine. This instrument simultaneously recorded the relative
air speed and the rate of vertical descent, from which could be
calculated the average slope. The gliding angle, which for the
most part is better than I in 6, represents an inclusive measure-
ment of all the resistances obtaining under the conditions of the
glide. It is necessary to be cautious, however, about deducing
too much from the figures in question as a great deal depends on
what the actual conditions were at the time the test was made.
A factor of importance, for example, is whether the propeller
was rotating during the glide, as the propeller itself would offer
considerably more resistance if stationary. The question of best
speed also affects the result, as was very evident from the
differences in the results of the first and the second attempts
that each pilot made in this test. The gliding speeds at which
the best gliding angles were measured appear in the tables.
The fastest speed was measured with and against the wind,
and the value given is the mean of the values so obtained. The
slowest speed, it should be remarked, depended much on the skill
and daring of the pilot ; in a few instances exceptionally slow
MILITARY TRIALS, 1912 275
speeds were obtained by switching on and off an engine that
would not run slow enough when throttled down. The speed
range is indicated by the percentage increase represented by the
fastest speed over the slowest speed.
The rate of climbing is given in feet per minute and the
equivalent power represented by raising the total weight at that
rate is also shown. In another column this is expressed as a
percentage of the engine power available, assuming 100 per cent
efficiency. In general, less than one-fifth of the total engine
power is demonstrated in the actual ascent, but allowing for the
probable propeller efficiency, the proportion of power available
for climbing may be regarded as nearly one-quarter.
Details of the petrol and oil consumption appear in another
table and the cost per mile on the basis of petrol at is. 6d. per gal.
and oil at 45. 6d. per gal. has also been calculated. It will be
observed that the rotary Gnome engine used in some cases one-
third as much castor oil for lubrication as it consumed petrol for
the development of power. The expense of their lubrication,
owing to the higher cost of oil per gallon, is thus very nearly
equal to that of the expense of the petrol per mile. Extravagance
in oil for lubricating purposes is essentially due to lack of proper
regulation in the oil feed and distribution. In the Gnome rotary
engine, a quantity of oil escapes through the induction valve in
the piston head and so through the exhaust valve in the cylinder
head into the atmosphere, where it emerges as very pungent
smoke.
Although aeroplanes fly against a resistance of approximately
one-sixth of their weight, whereas a motor-car is opposed by no
more than about one-fiftieth of its weight, the cost of fuel is
comparatively little more in the case of the aeroplane than it is
with the motor-car. Thus, even the Cody biplane with its
120 h.p. engine and its total weight of over a ton can be flown
for a cost of 2jd. a mile for petrol. Also, its economy of oil
consumption brings the total cost of petrol plus oil to a figure
only slightly in excess of 2jd. The Avro biplane with the
60 h.p. Green engine is another notable example of fuel and oil
economy, the cost in this case being less than if d. per mile. If
speed is taken into consideration the cost per mile-per-hour for
a journey of 100 miles on this machine may be represented by
2|d., which is cheaper than the corresponding value given by any
other machine.
The cost of fuel and oil required on an aeroplane is not only
an interesting subject to study, but it bears an important
relationship to the possible commercial future of aircraft. On
first thoughts, the excessive resistance, which causes an aeroplane
virtually to travel always uphill when compared with the
resistance of such a vehicle as a motor-car, would seem to be all
276 AVIATION
against its chances of utility from the commercial standpoint.
It is, of course, a very serious limitation, but on the score of cost
the figures in the table show that it suffers no very serious
disadvantage provided the structure of the aeroplane is reason-
ably immune from damage. The straightforward nature of
flight in the air and the high average speed thereby attained
represent a very economical condition compared with the
operation of a motor-car on the usual winding roads. Also, the
tyre bill of the motor-car is a very serious item, and although
tyres are used on aeroplanes there is no reason why they should
seriously affect the expense. The wing fabric does not wear out
by its motion through the air, and it can be made reasonably
weatherproof. Thus, in the absence of breakages, the chief items
in the upkeep of an aeroplane are fuel and oil, and although it is
necessary to have a comparatively powerful engine there seems
no reason why the expense under this head should not in future
be brought down to a very low figure indeed.
One matter of great importance that it is, however, necessary
to bear in mind in this connection, is that the motion of the
aeroplane is relative to that of the air, and only incidentally
relative to the earth. Thus, a machine may fly against the
wind and occupy a very long time in reaching its destination.
Alternatively it may fly with the wind and so traverse the
distance at an abnormally high speed.
In the same table as that containing the cost of fuel, figures are
also given showing the range of action on full tanks. The
conditions of the Trial specified that the machines were to be
capable of flying for 4^ hours without descent, and so the range
is thus limited by the speed. It will be noticed, however,
that in some cases the oil supply would run short before the fuel
tank was empty. Lubrication is just as important to an engine
as fuel, and such shortage might be very important in the case
of an engine using a special lubricant, such as castor oil, which
would not be available so readily as petrol if a forced descent were
made in some chance locality for replenishments.
MILITARY TRIALS, 1912
277
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IPM.
undg
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278
AVIATION
WEIGHTS
„-
~ <5
I
T3
M
Machine
•*£
lit
ll
.= JU
Ib.
Ib.
Ib.
Ib.
Ib.
h.p.
one in
Hanriot i . .
1166
1921
I4-7
24-0
6-4
80
6-6
Hanriot 2 . .
1160
1898
14-6
237
6-34
80
5'9
Bleriot Tan.
885
1499
14-7
25-0
577
60
5-6
Bleriot JSoc.
857
1481
I4-2
247
4-8
60
5'3
Avro
1191
1762
18-4
27-2
5-28
65
6-5
Bristol Mon. 14
1144
1839
15-3
24-5
8-75
75
6-5
Bristol Mon. 15
H59
1871
15-4
25-0
8-9
75
British Dep. 21
1226
2037
—
80
6-2
M. Farman
1318
I931
18-3
26-8
2-9
72
6-8
Fr. Dep.
1184
1868
14-7
23H
6-1
80
5'4
Cody
1948
2680
1 6-2
23-8
5-55
120
6-2
SPEEDS
II
w>
bJO
C
J-Q
'So
c
Machine
li
i
I
If
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IB
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rcr os
w S
fa
00
^ *•
o
u
^a,
m.p.h.
m.p.h.
m.p.h.
ft./min.
tup.
/o
Hanriot i . .
75-2
59'9
25-6
61
365
21-2
26-5
Hanriot 2 . .
75'4
66-6
13-2
68
333
I9-I
24-0
Bleriot Tan.
60-8
51-0
17-5
—
250
11 "3
17-7
Bleriot Soc.
58-9
40-0
47'3
52
236
10-6
16-6
Avro
61-8
49-3
105
5-6
8-6
Bristol Mon. 14
7°-5
68-3
3'2
64
200
n-i
14-9
Bristol Mon. 15
72-9
58-1
26-0
218
12-4
16-6
British Dep. 21 . .
68-2
54-6
26-0
—
267
26-5
2O-6
M. Farman
55-2
37-4
47-6
38
207
I2-I
16-8
French Dep.
69-1
17-1
62
333
18-8
23-5
Cody
72-4
48-5
49-4
59
288
23-4
19-5
MILITARY TRIALS, 1912
279
jnoq jad -S|B3
sal!IM-
jnoq «d
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6 S S 6 g 6 6 6 3 a x
000
Is* O N
• u
ffi K « pq < pq PQ w g £
280
AVIATION
COST OF FUEL AND OIL PER MILE
„
RANGE OF ACTION ON
"3
a
6
»- V g $
Fui-T, TANKS
*O *O
M
*0
C/3
a«'I'S
"o
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Machine
1-1 -•*-.
— ."•?
a
" '"S 3 O
£<§>
O®
&
o. £2
1
O
•1-
d.
d.
d.
m.p. h.
d.
Miles
Miles
6
Hanriot i
1-88
•64
3-52
75
4'7
408
400
•98
Hanriot 2
2-05
•5
3-55
75
4'7
361
406
I-I2
Bleriot Tan.
1-59
•5
3'°9
61
5'°
3°5
295
•97
Bleriot Soc.
I-93
•5
3'43
59
5'8
252
34°
1*35
Avro
1-2
•45
1-65
62
2-7
345
840
2-42
Bristol Mon. 14 ..
2-05
•32
3'37
70
4-8
343
328
•95
Bristol Mon. 15 . .
i-73
•12
2-85
73
3'9
421
420
I -00
British Dep. 21 ..
2-59
"42
4-01
68
5'9
320
590
1-84
M. Farman
2-38
0-7I
3'°9
55
5'6
276
266
•96
Fr. Dep.
2-2
I-04
3-24
69
47
379
1-2
Cody . .
2-25
0-3I
2-56
72
3'6
336
74°
2-2
WIND CHARTS
TO ignore meteorology in the study of aviation is to neglect
the very foundations of the science. The scope of this book,
however, does not pretend to do more than state the obvious
importance of the connection.
£ 23r^ August 1312
* / /
"Flight" Copyright Drawing
Wind charts showing- the state of the weather when most of the competitors took
their wind tests in the British Military Trials, 1912. On the right is the wind chart
for the flight made by Pixton on a Bristol monoplane for a quarter of an hour just
after noon on the 23rd August.
The wind charts above are given as a matter of interest and
as a record of the state of the art of flying in winds at the period.
They relate, with one exception, to the time of the Military Trials
in August, 1912. The exception is Hubert Latham's famous
flight at the first Blackpool meeting October, 1909. It was an
altogether phenomenal performance, and the chart deserves to
be recorded. His flight occurred between the hours of i and 2
p.m.
Each vertical line on the chart is a wind gust. A very remark-
281
282
AVIATION
able chart is that showing the state of the air while Pixton flew
the Bristol monoplane one noon over Salisbury Plain.
A special and sad interest attaches to the sudden rising of the
wind after a dead calm about 20 min. past six on 12
August, 1912. The gust indicated upset the experimental
Mersey monoplane, with fatal results. Just such a similar gust
' ' Flight ' ' Copyright Drawing
Wind charts illustrating- a remarkable rise in the wind over Salisbury Plain on the
i3th and 24th August, 1912. The former gust upset an experimental aeroplane and
resulted in a fatal accident. General flying was in progress on the latter date, bul
there was no accident. On the right is the chart of the wind during the famous High!
made by Latham at Blackpool on November 22nd, 1909. Latham's flight took place
between i and 2 in the afternoon.
occurred at the same time of day and place eleven days later,
whilst general flying was in progress. The state of the weather
during the wind tests in the Military Trails is indicated in one of
the charts, and shows the high general level of the security of the
pilots and their machines. Gordon Bell, who led the way on the
Martin Handasyde monoplane on that occasion, put up a particu-
larly fine flight.
ACCIDENTS
r I ^HE following opinions and recommendations have been
published by the Royal Aero Club, as the result of the
"^ investigations of the Accidents Committee into the specific
cases to which they refer. The full reports on each case will be
bund in Flight.
" The Committee is of opinion that the cause of the accident
was the pilot himself, who failed sufficiently to appreciate the
dangerous conditions under which he was making the turn,
when the aircraft was flying tail down, and in addition was not
lying in a proper manner.
" A sideslip occurred, and the pilot lost control of the aircraft.
" It seems probable that his losing control was caused by his
)eing thrown forward on to the elevating gear, thereby moving
:his forward involuntarily, which would have had the effect of still
urther turning the aircraft down. This would explain his being
thrown out whilst in the air.
" In the opinion of the Committee it is possible that if the
)ilot had. been suitably strapped into his seat he might have
retained control of the^aircraft.
" The Committee is of opinion that the cause of the accident
was primarily due to the instability of the aircraft, which made
t difficult to control in a disturbed atmosphere. That the
)oint where the accident occurred is well known to be one where
rregular disturbances of the air are prevalent under certain wind
xmditions. One of these disturbances must have struck the air-
craft, and the pilot eventually lost control.
" The Committee draws the attention of manufacturers,
designers, and pilots to the risk involved by want of provision
against the consequences of possible failure of parts of the
engine or its attachments to the aircraft, when such failure would
ead to the breakage of other and vital parts of the structure.
" The Committee is of opinion that the ground in question
was unsuitable for the sort of exhibition flights which the pilot
was attempting. It was too narrow for a pilot to attempt
sharp turns at a low altitude and between spectators on either
283
284 AVIATION
side of the ground. The inevitable danger from this condition
of affairs should be made known to promoters and aviators.
" The attention of manufacturers and pilots is specially
drawn to this particular accident, which emphasizes the risk
that is run in starting a cross-country flight with an aircraft
which, from one cause or another, is under-powered at the time.
" The Committee again draws attention to the primary
importance of a good field of view for the pilot.
" Seeing that this is not the first occasion on which wings of
the 'Antoinette' type have collapsed in the air, the Committee
recommends that the Royal Aero Club should vote a sum of
money for the investigation of this design.
" In this particular instance the aircraft was removed by the
local authorities almost immediately after the accident and any
evidence which could have been obtained from the position or
fractures of the parts was thereby lost. A good deal of the wood-
work was burnt after the removal. The Committee has already
made a recommendation that steps should be taken by the
authorities to prevent similar destruction of evidence in future.
" In view of the above recommendation, the Committee unani-
mously voted a sum of £20 to cover the cost of the investigation.
" The risk that is run by a pilot in persevering in a flight
with a faulty engine has already been drawn attention to, and
this further accident adds additional emphasis to the danger.
This flight, in that it was effected over water at a low altitude,
demanded additional precaution.
" When flights over water are habitually attempted, pre-
cautionary measures should always be taken, either the aircraft
itself should be capable of floating for a reasonable time, or,
alternatively, the men should wear, or have available, some
appliance for keeping them afloat until rescued."
MONOPLANE COMMITTEE'S REPORT
(ABSTRACTS)
" To the Secretary of State for War.
" The Committee appointed in the early part of October ' to
inquire into and report upon the causes of the recent accidents
to monoplanes of the Royal Flying Corps and upon the steps, if
any, that should be taken to minimize the risk of flying this class
of aeroplane,' submit the following report :
" Chief Conclusions and Recommendations. — The main con-
clusions arrived at by the Committee and their recommendations
in connection therewith may be briefly summarized.
ACCIDENTS 285
" (i.) The accidents to monoplanes specially investigated were
not due to causes dependent on the class of machine to which they
occurred, nor to conditions singular to the monoplane as such.
" (ii.) After consideration of general questions affecting the
relative security of monoplanes and biplanes, the Committee
have found no reason to recommend the prohibition of the use of
monoplanes, provided that certain precautions are taken, some
of which are applicable to both classes of aeroplane.
" (iii.) The wings of aeroplanes can, and should, be so designed
as to have sufficient strength to resist drift without external
bracing.
" (iv.) The main wires should not be brought to parts of the
machine always liable to be severely strained on landing.
" (v.) Main wires and warping wires should be so secured as to
minimize the risk of damage in getting off the ground, and should
be protected from accidental injury.
" (vi.) Main wires and their attachments should be duplicated.
The use of a tautness indicator, to avoid overstraining the wires
in ' tuning up/ is recommended. Quick-release devices should be
carefully considered and tested before their use is permitted.
" (vii.) In view of the grave consequences which may follow
fracture of any part of the engine, especially in the case of a
rotating engine, means should be taken to secure that a slight
damage to the engine will not wreck the machine. Structural
parts, the breakage of which may involve total collapse of the
aeroplane, should, so far as possible, be kept clear of the engine.
" (viii.) The fabric, more especially in highly loaded machines,
should be more securely fastened to the ribs. Devices which will
have the effect of preventing tears from spreading should be con-
sidered. Makers should be advised that the top surface alone
should be capable of supporting the full load.
[ " (ix.) The makers should be required to furnish satisfactory
evidence as to the strength of construction and the factor of
safety allowed. In this special attention should be paid to the
manner in which the engine is secured to the frame.
" (x.) Engine breakages should be systematically investigated
and reported on, and the reports should be submitted to the
Advisory Committee for Aeronautics.
[ " (xi.) No machine should be taken into use until after
examination and approved test, and all machines should be
regularly inspected, especially after any serious damage or repair.
'Parts of machines in course of construction should be inspected
'and passed before being assembled.
" (xii.) Two or three skilled mechanics for each squadron should
be specially engaged for a time to act as instructors and so set a
standard of technical workmanship.
" (xiii.) In case of any serious accident, care should be taken
286 AVIATION
to preserve and identify damaged portions of the machine which
may help to account for the cause. It is desirable to obtain the
assistance of the police authorities in this matter.
" 56. The Committee also desire to recommend that the follow-
ing questions be specially referred to the Advisory Committee
for Aeronautics for further investigation and report :
" (a) The general question of stability of aeroplanes.
" (b) Detailed investigation of the strains and stresses in aero-
plane wings, especially monoplane wings. Tests on the strength
of wooden struts and beams as used in aeroplane work.
" (c) Aerodynamic investigation of aeroplane wings designed
to have sufficient strength without external bracing.
" (d) Investigation into the strength of aeroplane fabrics,
wounded and unwounded ; and into the effect of the application
of dopes and of exposure.
" (e) Investigation of engine breakages.
" (/) The methods of testing a complete machine and the test
conditions to be fulfilled.
" (g) Investigation into the conditions of the vol piqtt<?in respect
to monoplanes and biplanes."
PILOT'S NOTES
I AM indebted to several pilots of great practical experience
for the following notes :
To Steer due South.
1. Get into the air against the wind.
2. Look at the compass and steer south by its direction.
3. Look up and ahead quickly, and take note of any land-
marks that happen to be in line with the compass course on the
card. The objects thus seen will lie due south from the starting-
point, for only an inappreciable amount of drift will have
occurred during this preliminary manoeuvre.
4. Without looking at the compass, proceed to steer the
machine straight for the landmarks just chosen. Steer thus for
a minute or so, until you feel you are progressing satisfactorily
towards them. Take no heed of the direction in which the
machine is pointing.
5. Without changing the attitude of the machine, glance down
quickly at the compass, and set the lubber point against the
needle. The lubber point being an adjustable part of the com-
pass case, which is attached to the machine, serves to mark a
certain attitude of the machine in respect to the needle of the
compass, which is controlled by the earth's magnetism.
6. Continue to keep the needle on the lubber point. If the
flight is of long duration, be sure to look out for changes in the
wind by keeping a careful note of the direction in which the
ground appears to move under the machine. If there is any
evidence of a change in the wind it is necessary to reset the
lubber point by repeating the original manoeuvre.
Cross-country Journeys.
1. Never fly across strange country at less than 3000 feet.
2. Do not attempt cross-country journeys before your skill
enables you to make the spiral glides and S-turns that may be
necessary if you are to alight safely in a small space in emergency.
3. Ease your engine periodically by gliding down about 1000
feet, but be sure to regain the altitude afterwards.
Landing.
i. Beware of sea breezes and other diurnal changes of the
wind that may cause the ground wind to blow in a diametrically
287
288 AVIATION
opposite direction to the upper air. Take note of flags, smoke,
and other guides that may assist you properly to alight up-wind.
2. Beware of being deceived as to the slope of the ground ;
it is very difficult to see which way a field slopes when viewing
it from above.
Rising.
i. When forcing a machine off a bad surface at a coarse angle
and low-flying speed, ease off the elevator slowly once you are
in the air. If the angle of the wings is reduced too quickly the
machine will strike the surface again, because the acceleration
will not yet have provided the necessary speed required to
maintain the lift at the finer wing angle.
i. Tie a piece of worsted or ribbon, about twelve inches long, to
some part of the machine where it is in the line of sight and can fly
freely like a flag in the wind. So long as the ribbon flies parallel
to the axis of the machine, the aeroplane is properly banked.
A sideslip is indicated immediately by the slewing of the ribbon
into an oblique position. Most pilots, by underbanking, sideslip
outward when turning. All pupils of the late Wilbur Wright
use the ribbon ; it will also work if tied to the mast of a tractor
monoplane.
Gliding.
Fit the machine with an air-speed indicator clear of the pro-
peller draught. Calibrate it by flying the machine level at its
normal speed, note the position of the pointer, then set the
index mark on the scale to correspond. Afterwards, in flight, the
pointer will always be on this mark when the air speed is normal
and the gliding slope can be adjusted accordingly. Most pilots
who do not use an air-speed indicator descend at an unnecessarily
steep angle.
THE WRIGHT PATENT LITIGATION
(From Flight, 15 March, 1913.)
" T T is interesting to observe how the three years' patent
I litigation in the United States, Germany and France, on
•*• which more than £50,000 has been spent, has now reached
its final stage simultaneously in all three countries.
" In the United States the action against Curtiss is now
disposed of, the Court at Buffalo having upheld the validity of
the Wright Brothers' patent.
" In Germany, the Supreme Court at Leipzig gave its decision
orally on 26 February, to the effect that the Wright Brothers
were the inventors of the warping per se and also of the warping
and rudder control combined, but although it did not support the
monopoly for the warping by itself, it confirmed the German
patent as valid on amendment being made to exclude warping
broadly per se. The German Court left the claim standing for the
combined rudder and warping, without making any stipulation
that these two mechanisms need be mechanically connected.
" The French case has now been heard in Paris, and judgment
will be delivered on igth inst., and seeing that there is no official
report of the oral judgment at Leipzig, those interested in France
are discussing the German judgment and reading their hopes into
the words of the judges. In view of the published opinions by those
who were not present, it may be interesting to quote Mr. Orville
Wright's observations made to a representative of the New York
Herald in Paris on the yth inst., after his return from being
present at the Trial at Leipzig :
" Mr. Wright said that it is an error to suppose that the
decision given by the Leipzig Court recently recognizes as valid
or patentable only a mechanical combination, or rather coupling,
of the warping wing movement with the aeroplane rudder. On
the contrary, this verdict, he asserted, means that all aeroplanes
with warping wings and a rudder, notwithstanding that the two
be independent one of the other, constitute an infringement of
the Wright patents.
" ' The decision of the Supreme Court of Germany at Leipzig,'
continued Mr. Wright, ' was an oral one. The written decision
will be made public later. After considering the patents of
Mouillard, Boulton, Robitsch and Ader, the Court held that we
19 289
f
290 AVIATION
were the inventors of warping, and that it was only on account
of disclosures made by our friend Chanute and ourselves, prior to
making our application for the patent, that the Court was com-
pelled to reduce the claim so as to exclude warping per se. The
Court then stated that the function of a rudder on a flying
machine is not merely that of a ship's rudder, but that it is a
necessity for maintaining balance on a flying machine having
warping wings.
" ' It held further that we were the first to discover and use
warping wings and rudder together, on the same machine. The
Court did not say that the invention was restricted to the
mechanical coupling of these two elements, as has been alleged.
" ' That our claim to the patent for the combined use of
warping wings and a rudder is a broad one is shown by the fact
that the director of a prominent German aeroplane factory called
on me in Berlin after the Leipzig decision had been handed down
to arrange for a licence to manufacture under the patent. He
said : " According to the decision of the Supreme Court every
machine built in Germany is an infringement."
" British manufacturers will no doubt be interested in these
foreign judgments, because up to the present, we believe, only
one licence has been applied for to work under the Wright
patents in England.
" In order to enable the patent situation in Germany to be
clearly understood by readers of Flight, we have interviewed Mr.
Griffith Brewer, who explained this somewhat complicated
technical question as follows :
" ' There are two general methods of resisting a patent, one by
proving the patent to be bad, and the other by proving the
alleged infringement not to come within the scope of the patent.
In cases where it is evident that escape by this second channel is
not open, actions are brought by the inf ringers against the owners
for the annulment of the patent, because if the patent can be
declared void anyone may infringe with impunity.
" ' It was an action to annul the Wright patent which was
brought in Germany, and the Supreme Court of Leipzig has now
decided to uphold the patent on its scope being reduced to
exclude the warping by itself. No other reduction is made in the
patent, and, consequently, all aeroplanes which warp and have a
vertical rudder, will still infringe the German patent in the same
manner they did before the action.
" ' The judges at Leipzig, in giving their decision, expressed
the view that the Wright Brothers were the inventors of the
warping per se, and also of the combined warping and rudder,
and they made no statement that the warping and rudder control
had to be mechanically connected in order to come within the
ambit of the claims. Statements to that limiting effect may
THE WRIGHT PATENT LITIGATION 291
therefore be disregarded, and seeing that the judges in an action
for annulment are not called upon to interpret whether certain
constructions come within the claims, it is obvious that they
would not go outside their duties and decide whether or not
aeroplanes of certain manufactures came within the claims.
" ' Warping on a machine which does not carry a rudder is thus
free to all in Germany, but that is all the decision actually
Since the above account of the actions was published, the
written decisions have been given. In Germany, the written
decision differs from the oral one in so far as the breadth of
the first claim is not declared, but in France the decision ex-
pressly says that the co-existence of rudder and warp on the
same machine comes within the scope of the patent. It is now
left to the experts to decide whether this broad claim is antici-
pated in any one of the alleged anticipations.
THE PETROL ENGINE
PETROL is a trade name given to a group of volatile fractions
in the paraffin series of hydrocarbons. In America the com-
modity is known as gasolene ; in France it is called essence.
In the scale of densities and boiling points, the petrol group stands
immediately above the lamp oils, which are misnamed in England
by the generic title paraffin, and in France by the word petrole,
but in America are called kerosene.
The chief source of petrol is natural petroleum, which is
mined in all parts of the world. Great Britain now derives
more than half her supply of petrol from Borneo, Sumatra,
and Java, via the " Shell " route through Suez ; the remainder,
" Pratts," comes from the American fields.
In most natural petroleums the principal constituent is the
paraffin series, the gaseous members of which serve to force
the crude oil from the wells. Petrol and the other petroleum
products are obtained by distillation. In natural petroleum
there is commonly only a small percentage of the more volatile
benzines that constitute commercial petrol. Owing to the
demand for motor spirit increasing out of proportion to the
demand for other petroleum products, the distillers have
gradually included a small proportion of the heavier fractions,
and petrol has steadily increased in density in consequence.
At one time it was possible to buy spirit as light as 0.68 specific
gravity ; now the lower grade petrol is 0.76 sp. gr.
Petrol will ordinarily begin to boil at about 45° C.; about
90% will have distilled below 130° C. When sprayed into
the atmosphere it evaporates and forms a combustible mixture
that is highly explosive when compressed. In this state it is
readily ignited by an electric spark.
The petrol engine works on this principle. One of its ac-
cessories is a carburettor, which consists of a simple spraying
device, the flow of petrol being regulated by a needle valve
controlled by a float. By means of a pipe the engine cylinder
communicates with the mixing chamber containing the spray
jet ; this communication is intercepted at intervals by a valve
that is usually opened and closed mechanically, but may operate
by the suction of the engine itself.
Assuming the piston to be made to descend from the top
292
THE PETROL ENGINE 293
of the cylinder, its effect will be to act like the plunger of a
suction pump ; if the above-mentioned inlet valve is open,
it will draw into the cylinder a charge of the combustible mixture
provided by the carburettor.
The inlet valve closes soon after the piston has reached the
bottom of its stroke, and thereby imprisons the charge, which
is subsequently compressed into the combustion space between
the piston and the cylinder head as the piston returns to the
top.
Just before the piston reaches the top of its stroke, an electric
spark is caused to occur at the points of an ignition plug pro-
jecting through the cylinder walls. The explosive charge
is fired, and the rapid rise in temperature within the cylinder
causes a forcible expansion of the imprisoned gases, which
press upon the piston, and cause it to perform the one working
stroke of its cycle of operations.
Having completed this stroke, another valve in the cylinder
head is mechanically opened to permit of the escape of the
burnt gases to the atmosphere. The returning piston scavenges
the cylinder of the products of combustion, the exhaust valve
closes, and the simultaneous opening of the inlet valve is a
signal for the cycle of operations to commence all over again.
On this four-stroke cycle devised by Beau de Rochas in 1862
most modern petrol engines operate. There is, however, also
a two-stroke cycle, in which a working stroke occurs once
every revolution, instead of once every two revolutions. In
this type of engine, of which the N.E.C. is an example, ports are
cut in the cylinder walls, so as to be automatically uncovered
by the piston as it approaches the bottom of its stroke. While
completing its stroke these ports remain open, and means
have to be devised for clearing away the burnt gases and
introducing a fresh charge during this brief interval of time.
It is the momentum stored in the flywheel that keeps the
engine running between the working strokes ; the " rotary "
engines serve as their own flywheels, for in such designs, of
which the Gnome is an example, the cylinders and crank chamber
revolve about the stationary crank shaft. Ordinarily, the
cylinders are stationary and the crank shaft revolves.
In order to save weight, some engines, including the rotary
engines, have their cylinders arranged radially about the crank
chambers. Others have them set in V formation in two rows,
and some follow orthodox motor-car practice in arranging the
cylinders in line. When the cylinders are radial, one of the
pistons is usually connected to a master connecting rod, the
big end of which embraces the crank pin in the usual way.
To this master big end the other connecting rods are hinged
by pins similar to those used for the attachment of the pistons.
294
AVIATION
In the Gnome engine the inlet valves are situated in the piston
heads and are opened by the suction in the cylinder. The
mixture from the carburettor enters the crank chamber through
the hollow stationary crank shaft that supports the engine,
and so gains access to the cylinders through the valves in the
piston.
Reverting to the subject of petrol, it is important to recognize
that its e vaporization, which is facilitated by spraying, is a
process demanding heat. This heat is withdrawn from the
atmosphere, and, under certain conditions, the lowering of
x-hf Copyright Drawing
Sectional drawing" of a e;o-h.p. Gnome rotary engine. Inset is a sketch of the inlet
valve in the piston head ; 'it is fitted with balance weights to compensate for the cen-
trifugal force of rotation. The operating" levers of the exhaust valve in the cylinder
head are similarly balanced.
the temperature will cause a deposit of snow and the con-
sequent interruption of further carburation. It is necessary
to avoid undue exposure of the carburettor to cold, and it is
generally considered desirable to provide it with artificial
heat by means of a hot- water jacket, or the proximity of an
exhaust pipe when the circumstances are convenient.
Other fuels that have been used with more or less success
in motor-car engines comprise lamp oil, a mixture of lamp oil
and petrol, benzol, " synthetic petrol," and alcohol. Lamp
oil, lacking the volatile fractions, is difficult to start from the
cold, but mixed with petrol it serves as a reasonable fuel.
Benzol is a by-product recovered from those coke ovens
that are fitted with appropriate apparatus. It is chemically
THE PETROL ENGINE 295
quite different from petrol, being the trade term for a group
of the benzene series. Its lowest boiling point is 80° C., so
that it, too, is sometimes difficult to start from the cold ; it
may, however, be mixed with petrol in order to remove this
difficulty. It is essentially a by-product, for the benzene
series is formed only when coal is distilled at a high tempera-
ture (1200° C.), and a high temperature is used only in the
production of an illuminating gas and metallurgical coke.
Were coal to be distilled commercially for the production of
motor spirit, a low temperature (450° C.) would afford a larger
yield, and the tar product would belong to the paraffin series,
and so yield petrol. The Del Monte process operates on this
principle.
" Synthetic petrol " is petrol manufactured out of crude
oil that has had all its natural petrol removed by distillation.
The crude oil is passed with water through a retort at about
600° C., containing a metallic catalyst in the form of iron turnings
or nickel. Having been dissociated with the water in the presence
of the catalyst, the elements reform as spirit having the qualities
of petrol. The process is also applicable to the treatment of
the tar produced by the low temperature distillation of coal.
At the moment, it is in the experimental stage.
When a paraffin is heated to a temperature above its boiling
point it becomes " cracked " into spirit, apparently of the
olefine series. To a limited extent " cracking " is adopted
in the usual process of distillation, as conducted commercially.
Alcohol, which may be produced by the fermentation of
starchy substances like potatoes and grain, has only about
one half the thermal value of petrol, and so cannot produce
the same amount of power from a given-sized engine. Unless
facilities were accorded by the Government, its industrial use as
a motor spirit in this country is virtually rendered impossible
on account of the expense involved in its methylation to conform
with the law. Moreover, methylated spirits is not very suitable
for use in a petrol engine.
The heat value of a pound of petrol is, roughly speaking,
20,000 British Thermal Units, and an engine consuming 0.7 Ib.
of petrol per h.p. hour will thus be supplied with about 14,000
B.Th.U. per hour per h.p. The relationship between heat and
work is given by Joules equivalent, which is 772 ft. Ib. per
B.Th.U. Thus, the energy supplied to the engine in the form
of latent heat is 772 X 14,000 ft. Ib. per hour, which is 5.6 h.p.
Thus the engine is being supplied with 5.6 h.p. in the form of
latent heat in the fuel, and is producing i h.p. in the form of
mechanical work ; the thermal efficiency plus the mechanical
efficiency of the engine, therefore, amounts to 18 per cent.
As the work done on internal friction in the engine is work
296
AVIATION
actually accomplished by the heat of the fuel, the pure thermal
efficiency is perhaps in the order of 23%. Thus, 77% of the
heat is wasted, being in part absorbed by the cylinder walls,
and in part discharged with the exhaust.
If the specific heat of the exhaust gas be taken as 0.2, its
temperature of ejection as 1000° Fahr. above the atmosphere,
and the original mixture to be such that 18 pounds of air is
carburetted by i Ib. of petrol, then the heat lost in the
exhaust is in the order of 19%.
SPARK GAP
INDUCTION COMPRESSION EXPLOSION EXHAUST
THE BEAU OE ROCHAS OR OTTO 4 STROKE CYCLE
"Auto" Copyright Dra-wing
Diagram illustrating the fundamental component parts of a petrol engine.
Petrol enters the carburettor through a needle-valve controlled by a float. It
is sucked from the jet by the air entering the cylinder during the induction
stroke. When compressed, this explosive mixture is ignited by the spark.
The working stroke of the cycle ensues, and is followed by the exhaust.
THE HIGH TENSION MAGNETO
SUMMARY OF A LECTURE
DELIVERED BY THE AUTHOR TO THE NATIONAL
SOCIETY OF CHAUFFEURS
ELECTRICITY exists in Nature. Several ways are known of
making its presence felt. For instance, if a piece of sealing-
wax is rubbed with flannel it becomes electrified and will
pick up little bits of paper. Again, if you attach a piece of carbon
and a piece of zinc to opposite ends of a wire and dip them
into a solution of sal-ammoniac in water, a current of electricity
will flow in the wire in consequence of the chemical reaction
in the cell. A battery of accumulators is charged by the chemical
change caused to take place in its plates when a current of
electricity passes through them. In return, it supplies its
own electricity after charging by a reversal of the chemical
action, which finally results in the plates assuming their original
condition when the battery is discharged.
When electricity flows in a wire, the wire is surrounded
by a sheath of magnetism. When the wire is in the form of
a coil wound, for preference, on a soft iron core, the iron be-
comes a magnet while the electricity flows.
Alternatively, an ordinary coil of wire with its ends joined
together will have a current of electricity induced in it if its
iron core is magnetized. But the electricity will only manifest
itself while the magnetization is taking place ; in short, it will
merely be an electric impulse.
Soft iron is readily magnetized by placing it near a permanent
steel magnet. If the permanent magnet is of horseshoe form,
and the iron is turned round between its poles or extremities
so that one end of the iron is first adjacent to the north pole
and then to the south pole, the iron will be magnetized, de-
magnetized, and remagnetized in the opposite sense. If a coil
of wire is wound on the piece of iron, an electric impulse will
be generated at each change in the magnetization.
This is the basis of the action of a magneto. When the arma-
ture revolves, its iron core alternately becomes a magnet in
one direction and then in the other.
297
298 AVIATION
Electricity so produced is of the pulsating kind ; at one
moment it is at a maximum, at another it is zero. It is when
the electricity is at a maximum that we must produce the spark.
There are two sorts of spark, the low-tension and the high-
tension.
If electricity is flowing in a closed conduit, and you switch
off the current, the momentum of the electricity will make it
jump across the gap. This is a low- tension spark.
If in an open circuit a very sudden impulse of electricity
is generated, it may be sufficient to jump a small gap of its
own accord without any preliminary closing of the switch.
This is the high-tension spark.
Whereas quite a feeble electric pressure suffices to produce
a low-tension spark, it needs about 10,000 volts to make a high-
tension spark jump even half a millimetre gap under com-
pression.
The advantage of a jump spark is that it avoids moving
switches inside the cylinders. In the old days of low-tension
magneto systems, the igniter tappet adjustments needed con-
stant attention.
High-tension electricity can be produced from low-tension
electricity in a very simple way. If two coils of wire are wound
on an iron core, and one of the coils is caused to pulsate with
electricity, then the other coil will reproduce the pulsations
in sympathy, although it is not electrically connected to the
first coil.
The voltage of the electric pressure in the second coil will
be 1000 times greater than in the first coil if it has 1000 times
as many turns in its winding.
In this way we can make the electricity of our secondary
winding jump a small fixed gap. But it is very important in
a motor-car to be able to time the occurrence of this spark so
that it synchronizes with the action of the engine.
In fine, we need to be able at will so to disturb the electrical
conditions as shall make the momentary pulsations of extreme
violence. This can be done by suddenly switching off the
primary current, if a condenser is already connected across
the switch contacts. By the switch, is in this case meant the
contact breaker of the magneto.
The condenser is a bundle of tin foil sheets in two groups
interleaved alternately and insulated with mica from each
other. It is capable of being charged with electricity like the
surface of sealing-wax. It prevents the low-tension spark that
otherwise would occur at the contact breaker, and it also acts
like a spring buffer in jerking the electricity to and fro in the
coil. Instantly, the secondary coil responds to the violent
pulsations, and causes a spark to jump the ignition plug gap.
THE HIGH TENSION MAGNETO 299
The spark itself is merely an example of high incandescence
due to the heating effect of the electricity. The light of an
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"Auto " Copyright Dra-i-ing
Diagram of connections for a typical four-cylinder magneto, based on the design
of the ZU 4 Bosch of 1912. The connections are applicable in principle to any high-
tension magneto system, but the internal connections of the Bosch armature differ
from common practice in respect to the earthing of the secondary winding through
the primary. The "earth" circuit, which is formed by the metallic parts of the
engine, etc., is indicated by a dotted line. When the magneto bracket is not part
of the engine it is necessary to complete the earth return from the engine to the
magneto frame by a wire.
electric lamp is similarly due to the filament being white hot.
It is made white hot by the electricity, but the electricity itself
is not the light.
300 AVIATION
When the armature of a magneto revolves, the magnetism
clings to its core. In consequence, the maximum impulse
occurs later as the speed increases. On the other hand, the
timing is required to take place earlier as the engine runs faster,
and so there is a tendency for the magneto either to be weak
when starting or else when running fast on full advance. In
order to overcome this difficulty specially shaped pole pieces
have been devised.
A diagram on page 299 shows the electrical connections
for a typical high-tension magneto circuit. The armature
of the magneto contains two coils of wire, one being of finer
gauge and having very many more turns than the other. In
most magnetos one end of each coil is connected to the iron
core of the armature. In the Bosch magneto illustrated the
secondary winding is attached to the primary winding, and
the other end of the primary winding is alone directly attached
to the iron core. The end so attached is said to be earthed,
in contradistinction to the other end, which is said to be live.
The live end of the primary winding is connected to the ad-
justment screw of the contact breaker. Against this screw
presses the platinum tip of the pivoted lever that is operated
by the cam. The pivoted lever is earthed. When the contact
is closed electricity flows in the primary circuit ; the flow is
interrupted by the sudden separation of the contacts, which
causes an electro-magnetic disturbance in the circuit, and so
generates a high electric tension in the secondary winding of
the armature.
The live end of the secondary winding is connected to the
distributor brush, which acts as a revolving switch, and so
places each of the ignition plugs separately in circuit with the
magneto in their proper firing sequence. The electricity from
the ignition plug returns to the magneto through the metal
parts of the engine, with which the base of the magneto must
be in electrical connection. This part of the circuit is known
as the "earth" return. When a magneto is switched off, the switch
contact must maintain a closed primary circuit, that is to sa~y,
they must form an electrical bridge across the contact breaker,
and so neutralize the effect of its mechanical operation.
THE ATLANTIC PASSAGE
THE offer of a prize of £10,000 by the Daily Mail for a flight
across the Atlantic, to be completed within 72 consecutive
hours, brings definitely to the fore a problem that has often
been informally discussed. In considering a non-stop flight of
this magnitude it is very important to recognize the possible
limitations that may be imposed by the fundamental mechanics
of aviation. A rough-and-ready estimate of the possibilities of
a non-stop flight serves indeed as an excellent object-lesson in
this phase of the subject, but this particular prize permits, of
course, of descents en route.
In order to obtain a starting-point for one's calculations,
it is necessary to review the available data in respect to modern
machines. From the evidence provided by the analysis of the
Military Trials, it seems reasonable to assume three provisional
figures for this purpose. The first is that any aeroplane is likely
to weigh 15 Ib. per h.p. in its construction alone ; secondly, it
is improbable that any machine at the present time has a re-
sistance of much less than i in 6 at 70 m.p.h. ; thirdly, the fuel
consumption of an aeroplane engine is seldom more economical
than half a pint of petrol per h.p. hour.
So long as these figures hold good, the size of the machine
is immaterial, that is to say, we can work in units of i h.p.
Looking at a map of the world, the shortest distance from
land to land in the vicinity of a steamship route is somewhat
less than 2000 miles. Let us, however, take 2000 miles to be
the distance to be flown in one stretch. At 70 m.p.h. this will
be accomplished in about 29 hours, let us say 30 hours for
convenience.
An engine working continuously for 30 hours, and consuming
half a pint of petrol per h.p. per hour will thus consume 15
pints of fuel per h.p. on the whole journey. The weight of
petrol is about 0-9 Ib. per pint, but in order to be on the safe
side we might allow for 15 Ib. of petrol per h.p. for the complete
journey.
Thus the machine itself weighs 15 Ib. per h.p., and the petrol
that it initially carries likewise weighs 15 Ib. per h.p., the total
being 30 Ib. per h.p. One-sixth of this weight represents the
resistance to flight at 70 m.p.h., according to the hypothesis.
301
302 AVIATION
That is to say, the resistance to flight is 5 Ib. at the speed in
question.
Five Ib. resistance at 70 m.p.h. represents 350 mile Ib. per
hour, or 94 per cent of I h.p., which is in excess of any propeller
efficiency thus far attained. Allowing for the reduction in
weight during the flight, owing to the consumption of the fuel,
the mean resistance of the fuel might be reckoned as that equiva-
lent to half the initial weight of the petrol. The mean resistance
of the machine and fuel on this basis would, therefore, be 375 Ib.,
which at 70 m.p.h. represents 260 mile Ib. per hour or 70% of ih.p.
It is apparent from these figures alone that the problem of
flying non-stop across the Atlantic is beyond the limit of present-
day possibility, for each of the three figures chosen to represent
the hypothetical conditions represents a comparatively low
actual value, and even with them it is difficult to show any
appreciable margin of reserve.
Moreover, it must be borne in mind that the above calculation
supposes the machine to be flying without a pilot. A journey
of this duration would require the presence of two pilots on
board such a machine. Their weight would be at least 300 Ib.,
and this would in some measure determine the actual engine
power required. If the attempt were made with a loo-h.p.
engine, the weight of the pilots would represent 3 Ib. per h.p.,
and thus add half a pound per h.p. to the resistance. If the
engine were more powerful than this, the weight of the pilot
would represent a smaller proportionate increment to the re-
sistance.
The prospect of building the machine lighter than the specified
weight is less promising than the prospect of reducing the re-
sistance by the application of the principles of stream- line design.
It is possible that a practical aeroplane might have a resistance
appreciably less than I in 6 at 70 m.p.h., and it is towards
the improvement in body design and the elimination of un-
necessary superstructure that the offer of this particular prize
may be expected to direct most attention.
The arbitrary choice of 70 m.p.h. as the flying speed is based
on the practical consideration that it is essential for any machine
attempting such a journey to be capable of meeting and forcing
its way through strong winds. Misfortune in respect to weather
would probably doom such an attempt to failure in any case,
and the best that can be done under the circumstances is to
reduce the risks as far as possible by reducing the time during
which the pilot is exposed to them. On the other hand, to
assume a speed greater than 70 m.p.h. would be to specify
something in excess of the values that can readily be attained
by existing machines, and the hypothesis itself would, therefore,
call for something in the nature of a special design.
NEWTON'S LAWS OF MOTION
I. T F a body be at rest it will remain at rest ; or if in motion,
I it will move uniformly in a straight line until acted
"*• upon by some force.
2. The rate of change of the quantity of motion (momentum)
is proportional to the force which causes it, and takes place
in the direction of the straight line in which the force acts.
If a body be acted upon by several forces, it will obey each
as though the others did not exist, and this whether the body
be at rest or in motion.
3. To every action there is opposed an equal and opposite
reaction.
Inasmuch as air has mass, weighing, as it does, nearly 0-08 Ib.
per cu. ft. (about 13 cu. ft. of air weigh i Ib.) it obeys Newton's
laws of motion, and gives rise to a reaction when a force is
applied to accelerate it from rest. Thus, the wing in flight
continually accelerates a stratum of air downwards, and must
derive a lift therefrom. Similarly, the propeller continually
accelerates a stream of air horizontally, and must derive a thrust
by so doing.
The total force in each case is proportional to the mass per
second and to the acceleration, thus :
Pressure (lift or thrust) = mass per second X acceleration
P=mf
There is some difficulty in estimating the theoretical force
that should be exerted by a wing or a propeller, because neither
the mass per second nor the acceleration can accurately be
denned.
If we take a given area of wing A, a given velocity of flight
v and a given mass-density for the air — , then the lift P at
o
some particular angle of incidence 0 is an expression in the
form:
g
where C is a constant known as the lift coefficient, which must
be determined by experiment on a model for any particular
wing shape and angle of incidence.
303
PRESSURE AND RESISTANCE
CONSTANTS
\ ERODYNAMICS is a science that is advanced mainly by
/-\ experimental data compiled in laboratories in different
parts of the world. It is, therefore, of great importance that
the results of various investigators should readily be comparable
at a glance. This is facilitated by expressing the results, when
possible, in such a form that the coefficient is an absolute con-
stant, that is to say, its numerical value is unaffected by the
system of units employed.
The pressure on a flat plate facing the wind may be expressed
in the form :
Force = Constant x density x Area x velocity2
F= C P " A v2 "
In order to express the force in pounds, when v is in feet per
second and A is in sq. ft. the expression is divided by gravity
thus:
F lb. = C
whence :
F lb.=
400
When the velocity V is expressed in miles per hour, the equation
becomes :
Thus, when C = i, the force per sq. ft. is numerically equal
to v2 4-190. This is an easy figure to remember, and can readily
be altered to correspond with other values of C.
304
PRESSURE & RESISTANCE CONSTANTS 305
THE RESISTANCE OF FLAT PLATES
If a flat plate facing the stream were to bring every filament
of the current to rest, C would have a value equal I -o.
If the resistance of the above plate were numerically equal
to the head corresponding to the velocity of the stream H = f—
then C would equal 0-5.
The above are purely theoretical values. Experiments give
the following results :
Small plates 0=0-507
Large plates C=o-62
From the latter, the approximate formula for the pressure
per sq. ft. on the face of a large surface is given by the expression
F (Ib.) = — -, where V is the air speed in miles per hour.
THE RESISTANCE OF PERFORATED PLATES
According to experiments made by Dr. Stanton at the National
Physical Laboratory, almost 10 per cent of the area may be
removed by the holes without affecting the total air pressure.
Even when as much as 40 per cent of the surface is missing,
nearly 90 per cent of the initial pressure remains. The theory
is that the dead water on the lee side virtually forms a backing
to the plate, and so receives on its behalf a limited amount of
momentum. As the holes become more numerous, the dead
water is rapidly washed away, thus when 90 per cent of the
plate is removed, the total pressure is 12 per cent of the initial
value, an amount that is only slightly greater than the extent
of the remaining surface.
THE RESISTANCE OF PLATES IN TANDEM
To the same order of things belong the phenomena related
to the shielding of one plate by another in front of it. Thus,
Dr. Stanton found that a pair of plates placed in tandem 1-5
diameters apart experienced less than 75 per cent of the pressure
that either one of them would experience when standing alone.
The distance apart had to be increased to 2-15 diameters before
the total pressure was made equal to that on one plate singly.
Even when 5 diameters apart, the total pressure was only 178
times the pressure on one plate separately.
20
306
AVIATION
THE RESISTANCE OF HONEYCOMB
RADIATORS
The resistance of a honeycomb radiator having 75% of its area
as wind passage is approximately one half that of a flat plate of
the same dimensions, i.e.
The resistance of a radiator may thus approximately be
expressed as V2-f-730 Ib. per sq. ft. super.
The speed of the air through the tubes of the honeycomb
(tubes 19/64" inside diameter, length 3f") was found to be
75% of the approaching air. Halving the length increased the
velocity through the tube to 82%.
ANGLE OF INCIDENCE
'2 t
-6 -4 -2 O 2 4 6 5 10 12 14 16 15 20
"Flight" Copy riff h Drawing
Chart comparing the lifting efforts of three flat-bottomed wing sections
and a flat plate. It will be observed that all the cambered sections con-
tinue to lift while inclined at a negative angle of incidence. The results
are from the N.P.L. experiments published in the Technical Report
for 1912.
PRESSURE & RESISTANCE CONSTANTS 307
THE LIFT AND RESISTANCE OF WINGS
In respect to the lift of aeroplane wings, the constant C
is called the lift coefficient. Although the critical angle of
maximum lift is ordinarily less than I2j°, the value of C may
be even slightly higher than 0-62 for some sections in this atti-
tude. That is to say, a cambered wing thus inclined may ex-
perience an upward lift that is greater than the pressure on the
flat face of a plate standing upright against the wind.
The numerical value of the lift coefficient C depends on
the angle of incidence and also on the shape of the section.
A chart opposite shows the nature of the variation for three
different sections tested at the N.P.L.
It will be noticed that in all cases a cambered wing has a
positive lift coefficient when the angle of incidence is zero.
For a flat plate, the lift coefficient itself is, of course, zero when
the angle of incidence is zero. Cambered wings reach their
-6-4-2 0 2 46 5 1O 12 14 16 15 2O
Flight' Copyright Drawing
Chart comparing: the lift with the resistance of the wing- sections and
flat plate referred to in the preceding diagram. The theoretical limit to
the lift resistance ratio of a flat plate is defined by the cotangent of the
angle of inclination, which is shown as a curve on the chart. It will be
observed that all the cambered sections develop a superior lift resist-
ance ratio throughout some portion of the range of useful attitudes.
308
AVIATION
attitudes of no lift when set at a negative angle of incidence.
The amount of the negative angle corresponding to no lift
depends on the shape of the section. Thicker sections, that is
to say those having a greater height of camber, have higher
lift coefficients at fine angles of incidence than thin sections.
MAXIMUM SPEED
WING LOADING
Flight " Copyright Drawing
Chart showing" the wing- loading of various machines in the British
Military Trials, 1912, and the maximum speeds attained. Graphs are
drawn on the chart showing four different lift coefficients, which serve
as datum lines for the comparison of different wing loadings at different
speeds.
In the Military Trials, when flying their fastest, very few wings
reduced their lift coefficient below 0-21, which corresponds to
The resistance coefficient of a wing also depends on the angle
of incidence and the section, but the greatest ratio of lift co-
efficient to resistance coefficient occurs for all sections at a
fine angle, generally in the neighbourhood of from 3 to 6 degrees
PRESSURE & RESISTANCE CONSTANTS 309
angle of incidence. Thin sections attain the highest ratio,
but at the angles of highest lift:resistance ratio the lift
coefficient is small. Nevertheless, for a given ratio, the thin
section appears to have a higher lift coefficient than the very thick
wing. Curves showing the lift resistance ratios of three flat-
bottomed wing sections tested at the N.P.L. are given on page 307.
There is also shown on this chart the lift resistance ratio of
a flat plate, calculated on a theoretical basis as to skin friction.
The lift resistance ratio of a flat plate cannot exceed the cotangent
of the angle of inclination. The curve of cotangents is shown
on the chart, and it will be observed that the cambered wings
demonstrate lift resistance ratios of a superior value to this
over a range of several degrees. A table of tangents appears at
end of book. The cotangent 0= — ^—
tan u
THE RESISTANCE OF WIRES
The resistance of a given wire is approximately proportional
to the square of the velocity. Actually, the rate of the increase
in the resistance of large wires is rather more rapid than is in
accordance with the V2 law ; with small wires the rate of
increase is rather less rapid.
The resistance increases in proportion to the diameter, and
also, of course, in proportion to the length. The product diameter
X length represents the projected area of the wire, which value
must be used for A in the expression F=Q>Av2.
The approximate values of C are as follows :
Smooth wires 6=0-435
Stranded cable C =0-52
It will be observed that the resistance of a smooth wire is
slightly less, and that of a stranded cable slightly greater than
the resistance of a small flat plate of corresponding area.
LTHE RESISTANCE OF STRUTS
Tests made at the N.P.L. on a circular section strut of i in.
diameter showed a value of €=0-57. That is to say, the re-
sistance of such a strut is in the same order as that of a flat
plate equivalent to its projected area.
A convenient figure to remember is that a i-in. circular section
strut has a resistance of about 40 Ib. per 100 ft. run at 40 miles
an hour. The resistance varies as the length, the diameter, and
the square of the speed.
THE RESISTANCE OF FAIR SHAPES
Tests on strut sections of fair shape, such as are often used
in aeroplane construction, showed that the value of C might
be reduced to o-i or even less. This indicates that a fair-shape
310 AVIATION
strut section may have a resistance only one-sixth that of a
circular section strut. The choice of the best strut section
for constructional purposes must, of course, necessarily take
into account the question of relative strength and weight.
But it is important to remember that on a machine having a
gliding angle of, say, one in six, every pound saved in head re-
sistance enables the machine to carry 6 Ib. extra weight in flight.
Thus a relatively heavy fair-shaped strut may be an economy
in load. Alternatively, a strut that is economical of weight
from the standpoint of strength might be encased in a low-re-
sistance form of some light material.
Fair shapes employed in strut sections do not ordinarily
exceed three diameters in length. The ratio of the fore-and-
aft length to the diameter is called the 'fineness ratio.
Other fair- shaped bodies may, of course, have a much greater fine-
ness ratio, but the computation of their resistance is only possible
when their form is analogous to that of a model already tested.
FRIGTIONAL RESISTANCE
When a flat plate is placed edgewise in the wind, there is a
resistance due to the friction of the air passing over its surfaces.
The expression of this force involves a term representing the
kinematic viscosity of the fluid.
Zahm's formula (corrected1) for friction is:
F = kA°-93 v1-86
The coefficient k having a value 0-0000082 when F is the
total resistance of both surfaces of a board that measures A
sq. ft. in single surface area.
Theoretically, a perfect stream-line body should experience only
frictional resistance ; from experiments at the N.P.L. it would
appear, nevertheless, that the coefficients for fair-shaped model
dirigible envelopes is sometimes twice as much as that for a
flat surface. Even in the best cases the flat-surface co-efficient
only represented 75% of the measured resistance.
At first sight, the inadequacy of the flat-surface coefficient to
account for the total resistance suggests that the nature of the
resistance is not wholly frictional, but that the difference might be
expressed as resistance due to the projected cross-sectional area.
Were such the case, this part of the resistance would be ex-
pressed in the form CpAv2.
Analyses of tests have been made on these lines, and opinions
seem to differ as to their values. Personally, I regard the
evidence at present available as being in favour of supposing
the resistance of fair shapes to be wholly of the order
F = kA°-93 v l-8Q
and not divisible into two parts.
In its original form Zahm's formula did not possess the dimensions of a force :
the above expression is the form in which it is used for reference by the N.P.L.
DISTRIBUTION OF PRESSURE ON
WING SECTIONS
r I ^ HE diagrams on page 102 are prepared from the researches
of Eiffel, but differ somewhat from his method of presenting
the results. They are intended to show more graphically the
nature of the distribution of pressure over various wing sections,
all of which are inclined at 6° angle of incidence to the line
of flight. The wing sections are shown in black ; above each
is a shaded region indicating suction ; below is another shaded
reg on indicating pressure. The radial distance of the outer
edge of the shaded region from the surface of the wing indicates
the relative intensity of the force at that point.
The suction and the pressure together provide the lifting
force that supports the wing in flight. It is evident at a glance
that the suction is in all cases much superior to the pressure ;
in other words, that the upper surface is by far the more im-
portant of the two.
Comparing the diagrams of the cambered sections with
that of the flat plate No. i it will be observed that the former
show a general tendency to tilt forwards in front. The portion
that seems to lean up-wind is situated over the dipping front
edge of the wing section. The fact that it exceeds in magnitude
the drag on the surface aft accounts for a Net up-wind force
parallel to the chord, which Lilienthal called the " tangential."
The diagrams thus serve as a graphic illustration of the funda-
mental advantage of the cambered wing over the flat plate.
The flat plate cannot possibly have any part of its diagram
tilted forwards, consequently it never has any up-wind com-
ponent. Its lift: resistance ratio, even neglecting skin friction,
could thus never exceed the numerical value of the cotangent
of the angle of its inclination. It is shown elsewhere that the
lift: resistance ratio of the cambered wing commonly does exceed
this value at angles greater than 4 or 5 degrees. The reason
for this superior merit is rendered evident in the forward tilt
above mentioned.
It is important to realize that the diagrams materially change
their shape with alterations in the angle of incidence. From
information of this character, properly plotted to scale, the
312
AVIATION
IM.PL SERIES
EIFFEL SERIES
11
BIRDS WING
WRIGHT
VOISIN
MFARMAN
BLERIOT XI
BLERIOTXI
BREGUET
" Flight" Copyright Drawing
At Eiffel's Laboratory in Paris and at the National Physical Laboratory at Tedding-
ton, the qualities of certain wing sections have already been very thoroughly investi-
gated. In the above diagram the sections so tested are illustrated, and in the table
opposite certain of the principal qualities relating to each are specified. The full
particulars relating to these series appear in Eiffel's Resistance de I'Air and the
Technical Report ior 1912 respectively.
PRESSURE ON WING SECTIONS 313
position of the centre of pressure can be located for any given
angle. The position of the C.P. and its travel are discussed on
page 15.
There is no known theoretical limit to the local intensity of the
suction on the upper surface, but tests show that it may be ex-
pected to reach a value (—1-5 p.v2) in the vicinity of the leading
edge.
The maximum local pressure on the bottom of the wing
cannot exceed (+Jpv2).
TABLE OF COEFFICIENTS FOR THE SECTIONS
C1 = lift coefficient at critical angle
L : R = maximum lift : resistance ratio
Cj^lift coefficient corresponding to L:R
No.
i
2
3
4
6
7
4b
N.P.L.
SERIES
EIFFEL
SERIES
Cx
L:R
C2
No.
c,
L:R
C2
0-48
13-8
0-16
i
0-50
6-4
O-2I
°*57
15-0
0-225
2
0-52
12-5
0-18
0-61
I4-3
0-275
3
0-62
II'O
0-34
0-59
12-7
0-325
4
°'75
7-1
0-56
0-56
n-7
o-35
5
0-62
XI-O
0-36
0-53
ii-i
0-38
6
0-64
10-6
0-32
0-48
IO-2
0-42
7
0-46
13-9
0-15
0-62
12-7
0-36
8
0-60
II-4
0-28
0-64
12-7
0-38
9
0-67
7-8
0-46
0-66
12-7
0-40
10
0-56
10-4
0-26
ii
0-51
14-0
0-17
12
0-48
15-4
0-13
13
0-62
9-1
0-28
130
o-54
13-2
0-26
ANALYSIS OF FORCES ON WING
SECTIONS
IN the Technical Report of the Advisory Committee, the
forces acting on various wing sections are analysed in detail
throughout a full range of angles. The accompanying charts
illustrate the composition of these forces in a way that indi-
cates some of the more important characteristics of a cambered
wing.
The first diagram shows the forces normal to the chord.
As the angle of inclination is always small, these forces may be
regarded as perpendicular. They, therefore, represent the lift.
Curves are plotted to show the contribution of the upper and
lower surfaces separately.
The lift due to the upper surface is about three times that
due to the lower surface, as may also be seen very clearly from
the diagram of distribution of pressure on page 102.
The lower surface of this wing exerts a downward pressure
below (+4°) angle of incidence, while the wing as a whole ceases
to lift at about (-2°).
If one of the diagrams showing the distribution of pressure
on a cambered wing (page 102) is integrated, the resultant
force would be tilted slightly forward of the normal to the
chord. In fine, it would have an up-wind component parallel
to the chord. The contributions of the upper and lower sur-
faces to these forces parallel to the chord are shown in the
second of the diagrams herewith.
It will be noticed that the lower surface is of small consequence.
If it were flat it would have no force parallel to the chord except
that due to frictional resistance. Similarly, if the section
under investigation were a flat plate instead of a cambered
wing, there would be no force parallel to the upper surface
except friction. The net total force parallel to the chord is
that which Lilienthal called the tangential. For all angles greater
than about (+3°), the tangential is an up-wind force tending to
reduce resistance.
It is important to differentiate between the tangential which
may be an up-wind force and the net resistance which is
invariably a down-wind force.
If the section were a flat plate there would be no " tangential "
ANALYSIS OF FORCES ON WING
ANGLE OF INCIDENCE
10 15 go 25
TOTAL
UPPER SURFACE
LOWER SURFACE
0— ZERO L\FT
OWN PRESSURE
UPPER SURFACE
TOTAL TANGENTIAL
LOWER SURFACE
RESISTANCE DUETO NORMAL
TOTAL RESISTANCE
RESISTANCES
;=_ RESISTANCE DUE
TO PARALLEL F
"Flight" Copyright Drawing
Diagram illustrating an analysis of the forces on a cambered wing as obtained by
experiment at the National Physical Laboratory. The particulars are published in
the Technical Report of the Advisory Committee for 1912. An explanation appears
the Technical Report of the
in the text of this book.
316
AVIATION
consequences, the resistance would be at least equal to the normal
force multiplied by the sine of the angle of inclination (P sin 6) .
The value of the net resistance of a cambered wing is made up,
for any angle, by the difference between P sin 6 and the tangential.
The degree to which the " tangential " assists in reducing P sin 0
is shown in the third diagram.
The low value of the net resistance over all the finer angles
in the flight region indicates in a very striking manner one of
the chief reasons for the merit of the cambered wing. The other
reason is its superior lift coefficient at any given angle. This
is illustrated by the chart on page 306.
LIFT
RESULTANT
(NORMAL
~P
A?
LINE. OF FLIGHT
HORIZONTAL
RESISTANCE
DUETO NORMAL *Fsin0
"Flight" Copyright Drawing
Vector diagram illustrating- the forces on a wing as built up from the
details of the analysis of forces illustrated in the preceding1 diagram.
The force P normal to the chord would give rise to a resistance P sin Q
but for the existence of the up-wind tangential which causes the re-
sultant to be inclined forward of the normal and so reduces the net
resistance to the value shown.
For an explanation of the coefficients the reader is referred
to page 307.
It will be noticed that the curves are dotted above the angle
of I2j°, this is the critical angle for the wing in question, and
from that point up to 20° the upper-surface pressures are un-
steady. At about 20° the suction again becomes steady ; its
distribution is, however, then uniform all over the upper sur-
face, which thus no longer contributes an up-wind force. On
the contrary, the force parallel to the chord now acts down-
wind, and tends to augment the resistance, but as the lower
surface still contributes an up-wind force, the net tangential
is practically zero.
A vector diagram is given herewith to show the forces acting
at 12 J° angle of incidence. It is of assistance in visualizing the
series of conditions that are graphically shown in the charts.
ANALYSIS OF FORCES 317
It is most important to recognise that the existence of any
force parallel to the chord, other than that due to friction,
is entirely due to the uneven distribution of pressure along the
chord at all ordinary flight angles. If the pressure distribution
on the surface were uniform, the up-wind pull on the dipping
front edge would be neutralized by the down-wind drag on the
trailing portion of the wing. Similarly if the wing has no camber
(i.e. flat plate) there is no chance of any " tug-of-war " through
a tilting of the forces, and the potential advantage of an uneven
pressure distribution is lost.
THE TRAVEL OF THE C.P. ON WING
SECTIONS
A SERIES of diagrams on page 15 show a wing section in ai
/-\ range of attitudes from 4° to — 1° angle of inclination. On
•*• ^"each diagram a vertical arrow is drawn to indicate the centre
of pressure. It can be seen at a glance how the C.P. travels to-
wards the trailing edge as the angle becomes finer. Above 5°,
only a slight forward movement of the C.P. accompanies an
increase in the angle of incidence ; above 19° the movement'
reverses its direction.
The travel of the C.P. is shown in another manner on page 319.
Different wing sections exhibit these phenomena at different
angles, but within the range of attitudes employed in flight,
wing sections commonly now used are unstable in the sense
that the C.P. retreats as the angle diminishes. A disturbance
tending to reduce the angle would thus be augmented by the
direction in which the C.P. would travel, and the initial dis-
turbance would in consequence culminate in a nose dive. It
is the tail of the modern aeroplane that neutralizes this un-
stable movement of the C.P. on its wings.
A flat plate has an inherently stable movement of the C.P.,
as may be seen from the slope of the graph in an accompanying
chart.
A stable movement of the C.P. throughout a range of about
8° in the flight region is also a characteristic of a wing section,
No. I3b, tested by E. N. Fales at the Massachusetts Institute
of Technology. Its graph is also shown in the chart opposite.
It is interesting to compare these various characteristics, and
this has been done by superimposing the graphs on a common
chart.
Reflexed wing sections (i.e. having an up-turned trailing edge)
are also being investigated for stability of C.P. travel.
If a satisfactory stable wing section could be found, an aero-
plane might be constructed without such a long tail.
THE TRAVEL OF THE C.P.
319
FALES NM5b
EIFFEL NM3te
(BLERKJT N»XI»)
E -5 -4 -5 -0 -7 -5 -0 10 O -1 -2 -3 -4 -5 -6 -7 -5
" Plight '' Copyright Drawings
Charts illustrating' the travel of the centre of pressure on two wing sections and a
iat plate. They are shown on separate diagrams and also superimposed on a common
(diagram. The Fales wing section is particularly interesting inasmuch as it demon-
strates a stable travel of the C.P. within a portion of the flight region. The chart for
ftleriot wing is b,ased on the Technical Report,
THE SYNTHESIS OF AEROPLANE
RESISTANCE
IT is obviously important to have a convenient method of
combining the data relating to the resistance of various details
in such a form as shall enable the designer to estimate the re-
sistance of the complete aeroplane.
The method employed at the Royal Aircraft Factory and
elsewhere is illustrated by the charts opposite. Actually,
the R.A.F. method is to superimpose the curves on one chart,
but it is more convenient to explain them separately.
All the graphs are drawn to a common scale of flight speed,
which forms the basis of the investigation. The vertical scale
of each diagram varies according to the nature of the graph.
The first step is to plot the curve of wing resistances by calcu-
lating the lift coefficient required to support the weight in
flight at any given velocity, and finding the corresponding
resistance coefficient from the characteristic curves of the wing
section employed. It is, of course, essential to have these
characteristic curves, which are only to be obtained by tests
on scale models. The characteristic curves for Bleriot II bis
as tested at the N.P.L., are given on the same page. Character-
istic curves for other wing sections tested at the N.P.L. appear
in the Technical Report, and those tested by Eiffel are given
in his Resistance de I' air et de V aviation. A numerical example
showing the calculation of the lift coefficient required at a
given speed is given on page 329.
Having plotted the resistance of the planes (with an allowance
for biplane interference when calculating the lift) the next
step is to calculate the resistance of the struts, wires, and body.
Notes on the resistances of various objects are given on p. 305.
These resistances are plotted on the same chart, and are
added together to give the total resistance.
It is useful to replot this total resistance, so as to express
the " gliding angle," i.e. resistance '.weight ratio, at any speed.
The gliding angle is generally expressed as i in — , but this
system does not give a uniform scale on the chart. The scale
is found by first using the uniformly divided scale of resistance,,
and then ascertaining the actual resistance corresponding to*
320
AEROPLANE RESISTANCE
321
ON£ IN in
21
322 AVIATION
any given gliding angle for the weight in question. For ex-
ample, if the weight is 1700 lb., the gliding angle required
is i in 5, then the corresponding place on the scale for the I in 5
mark is 1700/5=340 lb. Similarly for i in 6, I in 7, etc.
The next step is to convert the resistance into power required
by multiplying the resistance by the corresponding speed in
m.p.h. and dividing by 375, in order to express the result in h.p.
On the chart of power required, may be plotted a graph showing
the power available with a given propeller and given engine. The
vertical height between these two curves gives the reserve power
available for climbing, etc., at any speed, and where the curves
intersect is the limiting speed in horizontal flight.
Supposing the power available is such that the curves intersect
in the flight region at a slow speed as well as at a high speed, a
condition of especial significance is indicated by the former point.
The machine can just fly straight. It has no reserve power for
acceleration, consequently it is unable to enter the proper flight
region without the assistance of gravity, which involves a partial
descent. The attitude of the machine, however, is not appro-
priate to descent, because the tail being down, any manoeuvre
such as turning involves either descent or acceleration, conse-
quently the condition is a critical one that should be strictly
avoided. It is liable to occur to a pilot who persists in flying a
machine with an engine that is not giving its proper power
output.
NOTE ON THE CENTRIFUGAL COUPLE
IN connection with the general problem of steering an aero-
plane it has been pointed out that the centripetal force is
derived as a component of the wing pressure, when the wings
are canted.
When flying on a circular course the outer wing tip necessarily
proceeds faster than the inner wing tip. In the differential
negative warp control, positive portions of the wings are assumed
to be symmetrical. It would seem, therefore, that the centre
of pressure must be displaced to the far side of the centre of
gravity, and, therefore, tend to increase the bank.
In this connection it is, therefore, interesting to consider
the influence of the centrifugal couple as giving rise to a force
tending to prevent such increase.
If a stick has a string attached to the centre of its length,
and is whirled at the end of the string, it has two positions of
equilibrium, only one of which is stable. When the stick is
upright and at right angles to the string, the centrifugal forces
of its halves are balanced. If one end of the stick is now
displaced so that the stick lies obliquely to the string, then the
mean velocity of one half of the stick exceeds that of the other,
and the centrifugal force is greater in the faster portion. This
augments the tilt until the stick lies in line with the string,
where it assumes a position of stable equilibrium.
The wings of an aeroplane when banked would seem to be
in a position similar to the tilted stick of the above experiment.
The centrifugal couple tends always to destroy the bank, and
so tends to counteract the couple due to the superior mean
velocity of the outer wing. If they tend to a position of stable
equilibrium, then the balance of the system as a whole may
be stable during circular flight, in spite of the symmetry of the
positive angles of opposite wings.
That this balance between the surplus lift and the centri-
fugal couple is plausible may be deduced from the general
consideration that both are dependent on the superior mean
speed of the outer wing. As the bank increases, the difference
in the mean speeds diminishes, and therewith the surplus lift
decreases. For an imaginary bank of 90°, hi which the wing
spars would be vertical to the ground, the condition of balance
323
324 AVIATION
for circular flight would be identical with those of straight-line
flight, the relative speeds of the two wings having become equal
once more.
Although the surplus lift depends only on the difference
in the mean speeds of the positive parts of the wings, and is
thus a maximum when the circular course is flown with level
wings, the centrifugal couple depends also on the bank itself,
and tends to a maximum when the bank is 45°.
Assuming that the symmetrical positive parts of the wings
are automatically balanced by the centrifugal couple in the
way suggested, then the warping of one negative wing tip suffices
for the needs of steering a circular course with fixed controls.
NUMERICAL EXAMPLES
MOST of these calculations are only accurate to the
degree of approximation obtainable with a six-inch slide
rule, but the method of working by logs is freely
indicated as a guide to greater precision when necessary.
LOGARITHMS. — In the tables the mantissa only is given : it
is always a positive quantity.
The characteristic is — as the number is > < unity.
e.g. log 120=2-079 > l°g 12=1-079 ; log 1-2=0-079
log 0.12 =1-079 '> log 0-012 =2 -079.
Fractional indices by logs :
e.g. H71-86; log ii71-86 = i-86 log 117 = 1-86x2-068
=3-85 =log 7080
/. H71-86=7o8o.
e.g. iJ-72, log 1172=2 log 117=2 x 2 -068 =4 -136= log 13700.
FRICTION AL RESISTANCE. — Assuming Zahm's formula for air
friction, calculate the friction on 1170 ft.2 of exposed surface at
80 m.p.h.
Zahm's formula; F(lbs.)=o-ooooo82A°-93v1-86
v is in ft. /sec.
.'. 80 m.p.h. =1-46x80 =117 ft. /sec.
Thus, the friction F(lbs.)
=0-0000082 (ii7o)°-93(ii7)1-86.
(ii7o)°-93; 0-93 log 1170 =0-93 X 3-068 =2-85 =log 708.
/.(ii7o)°-93=7o8.
(H7)1-86 ; 1-86 log H7=i-86x2-o68=3-85=log 7080.
/.(ii7)1-8e=7o8o.
/. F(lbs.) =0-0000082x708x7080
=0-0000082 x 5,000,000
=41.
325
326 AVIATION
Imagine air friction to be cc Av2 instead of A°-g3vl-8&, an£
the coefficient remains unaltered, what would be the difference for
the case in question ?
Av2=ii70 xii72=H7o x 13,700 = 16,000,000,
and A°'93v1<86=5,ooo,ooo.
Thus, the resistance to motion would be more than trebled.
What is the pressure on a flat plate measuring 35 ft. by 33 ft. 6 in.
facing a wind of 80 m.p.h. ?
The formula for air-pressure on flat plates is P=c/aAv2.
A=35X33'5 ft.2=ii7o ft.2
v ft./sec.=8o x 1-46=117.
p for air at atmospheric temp, and pressure=o-o8 lbs./ft.3
P I
.'. -= — approx.
g 400
C for large plates =0-62 (experimental value).
=0-62 x- x 1170 xii72
_o-62 xii7o x 13,700
400
=24,800.
In the above case, compare the pressure per square foot and per
square metre.
g 400
P(kgs./m2) = C-^v2 (metric).
o
P=i-2g kg./m3 ; §=9-81 m. /sec. /sec.
g 7-65
v=ii7XO'305=35-6 m./sec.
.\V2=I280.
C being an absolute constant is still 0-62.
. „, 0-62x1280
.-. P(kgs./m2)=
Ratio : — lbs./ft.2: kgs./m2= 21. 2/104= 1/4.9.
Compare with the figure given in the Pressure Conversion
Table, page 345.
NUMERICAL EXAMPLES 327
In the preceding examples, compare the pressure on the plate
when facing the wind with the surf ace friction when it is set edgewise.
The area of the plate facing the wind is 1170 ft.2.
The surface that it exposes to friction when edgewise is, there-
fore, 2x1170 ft.2.
For convenience call the pressure P and the friction F.
Then P = 24,800 Ibs., and F =2x41 =82 Ibs.
.'. Ratio P/F= 24800/82 =300 nearly.
That is to say, at 80 m.p.h. the pressure on a flat plate of 1170 ft. *
area is about 300 times the total friction on its surface when
placed edgewise. This ratio only holds for this particular area
at this particular speed.
In the above, what would be the effect 0/25% increase in speed ?
New speed =80 + (-25x80) =80 +20 = 100 m.p.h.
For the face pressure P« v2.
/.Increase in P=^-2=i-252 = i-57 = 57%-
For the surface friction Focv1-86.
/. Increase in F=^^1-86=i-251-86.
oO
£.251.88 ; j-86 log i-25 = i-86xo-097=o-i8=log 1-51.
/. i-251-86=i-5i.
/. Increase in F=5i%.
In the above, what would be the effect of halving the area of the
plate ?
The face pressure P is proportional to the area
.'. P is reduced by 50%.
The friction F is proportional to A0-93
.'. Fcc(i)-»3 ; 0-93 (log i— log 2)
log 1=0-0 ; log 2=0-301 ; 0—0-301 = 1-699
0-93 X I -699 =0-93 X (—0-301) = — 0-28 = i -72 =log -525.
.-. (J)-»3=o-525.
That is to say, the friction F will now be 0-525 of what it was
formerly. This represents a reduction of (1 — 525) =0.475, i.e.
47i%-
What would be a plausible value for the estimated resistance of a
fair-shaped body having iijoft.2 of exposed surface ?
From the tests recorded in the Technical Report on dirigible
shapes, the resistance calculated by Zahm's formula was found
to vary indiscriminately from 50% to 75% of the total resistance.
Thus, if the fair-shaped body in question is in any way less
symmetrical in form than these examples, it seems improbable
328 AVIATION
that its resistance would be less than twice that calculated by
Zahm's formula.
Thus, the resistance calculated above is 41 Ibs.
.'. a plausible figure for the resistance of the fair-shaped body
is 2 X 41 =82 Ibs. at 80 m.p.h.
The resistance of the body will be « A-^v1-86 according to the
Technical Report.
Having regard to the fact that any fair-shaped body must have a
considerable fineness ratio, and also to the fact that the exposed
surface necessarily increases with the length, it is interesting to
discuss roughly the limiting ratio of length to diameter that would
make the resistance of a fair shape under given conditions equal to
that of its cross-sectional area as a flat plate.
In a previous example, the face-pressure on a flat plate was
shown to be 600 times greater than the friction on the same area
of exposed surface for a particular case.
Allowing the friction so calculated to be 50% of the total
resistance of the fair shape, the ratio of face-pressure to surface
resistance becomes 300 : i.
Suppose for convenience that the surface is expressed, as that
of a cylinder, by ?rDL, where D = diameter and L= length.
Then the cross-sectional area= — D2.
4
the ratio
section — 2 T)'
4
And L/D= fineness ratio.
.'. when 4 L/D=3oo the resistances will be equal.
i.e. when L= — 0=75 D.
In the above, roughly speaking, how would the resistance of the
fair shape compare with the pressure on the section as a flat plate if
the fineness ratio were 7-5 ?
Tt, j.- x surface 7-5
The ratio of areas — -. — =4^=30.
section ^ i
,™ ,. , . , unit surface
The ratio of resistances — r— — ; — =300.
unit section
/. since the actual surface is 30 times the cross-sectional area,
the resistance of the body might be expected to be about -^th
that of its cross-sectional area as a flat plate for this particular
case.
Since Foe A0-9^1-86, whereas PocAv2, it is apparent that the
above ratio will not hold for any other speed or area of exposed
surface than the particular value for which it was calculated.
NUMERICAL EXAMPLES 329
A certain aeroplane loaded weighs 2000 /6s. The wing selected
for its use has the characteristics graphically illustrated in the
chart on p. 321. Choose a suitable area.
The lift of a wing is given by the formula P(lbs.)=C-Av2, of
o
which the constant C varies with the angle as shown on the chart ;
the mass density of air - is conveniently taken as — ; A is
the area required in ft.2 and v is the flight speed in ft. /sec.
The weight in flight is constant and = 2000 Ibs.
.-. P=C^Av2=2000 Ibs.
g
It is obviously desirable to maintain a fairly high liftiresist-
ance ratio throughout the flight region. By inspection of the
graph, the lift: resistance ratio of 10 suggests itself as a plausible
lower limit for the purposes of calculation. This value occurs
when the angle of incidence is 2° and again when it is 12°. The
corresponding lift coefficients are 0-2 and 0-56 respectively.
Of these, the latter represents the limit of normal low-speed
flight. It determines the area, if ability to fly slowly is a con-
sideration of first importance. Suppose a safe speed of 40 m.p.h.
is required.
Then 40 m.p.h. = 1-46x40 =48-4 ft. /sec.
P=C-Av2=o-56x — X Ax (48-4)* =2000 Ibs.
g 400
. _ 2000x400 _ 800,000 _ 800,000
"0-56 x (48-4) z~~ 0-56 x 2350 1320
=6ioft.2.
The wing loading is thus -7- — =3*3 Ibs. nearly.
It now remains to consider the speed required to support
flight at 2° angle of incidence, when the lift coefficient is 0-2.
Thus, from the above :
800,000
0-2x610
,£
=6600
J log 6600 =4(3-8195) =
=log8o-3.
/. v=8o-3ft./sec. = 55-5 m.p.h.
The speed range of 40 to 55-5 m.p.h. represents 15-5 m.p.h.
increase on 40 m.p.h., or 39%.
330 AVIATION
In the above, suppose the inclusive resistance to horizontal flight
is graphically illustrated by the gliding angle curve on p. 321. Discuss
the possibilities of the machine if 80 h.p. is available at the pro-
peller under all conditions of flight.
At 40 m.p.h. the gliding angle by the graph is i in 6. The
resistance to flight is therefore 2000-^-6=333 Ibs.
333 Ibs. X 40 m.p.h. = 13, 320 mile Ibs./hr.
(13,320-^-375) =35-5 h.p.
There is, thus (80—35-5) =44-5 h.p. or 55% of the engine power
in reserve at the low speed.
At 55-5 m.p.h. the resistance is I in 7-7 = 260 Ibs.
260 Ibs. X 55-5 m.p.h. =38-5 h.p.
Suppose the resistance from this point upwards increases in
proportion to V2, what is the limit in speed for 80 h.p. ?
Since power is the product resistance X velocity, and resist-
ance is, by the above assumption, made proportional to V2,
then the power required becomes proportional to V2xV=V3.
Alternatively, the speed is proportional ^/ power.
Thus, ^38-5 h.p. corresponds to 55-5 m.p.h.
Then 3/80 h.p... .. 55-5
J log 2-o8=Jxo-3i8i=o-io6.
=log 1-28
/. 4/2-08=1-28
and V = 55«5X 1-28=71 m.p.h.
At 71 m.p.h. with 80 h.p., the resistance is - — ^-^=424 Ibs.
And for a weight of 2000 Ibs. this represents a " gliding angle "
of i in 4-75.
It will be observed that this figure is fairly in accord with the
value given on the graph for this speed.
In the above, it is apparent that there is a reserve of about 80 h.p.
at the lower speeds. If this is all available for ascent what is the
initial rate of climbing, neglecting all losses ?
40 h.p. = (40x33,000) ft. Ibs./min.
The weight raised is 2000 Ibs.
, ... . , . 40x33,000 rr , . .
.'. Initial rate of ascent is— - =660 ft. /mm.
2OOO '
NUMERICAL EXAMPLES 331
Suppose it to be possible to ascend until the scale of lift coefficients
is reduced by 33% owing to the change in atmospheric density, what
is the limiting altitude ?
Neglecting temperature change, the ratio of densities gives
the ratio of the barometer readings, viz. 3 : 2 = 1 -5.
An approximate formula connecting this ratio with altitude is
H(ft.) =60,720 log q,
where q = M-^ the ratio of the pressures, viz. in this case 1-5.
Thus H(ft.)=6o,72O log 1-5 =60,720 x -1761
= 10,700 ft. (approx.).
If the barometer reads 760 mm. initially it will finally read
2x760
=5Q5 mm.
A table is given on p. 352 showing the heights in metres corre-
sponding to barometer and temperature.
For 505 mm. a plausible reading is about 3250 metres or
3-28x3300 = 10,700 ft.
An aeroplane flying at 600 ft. altitude and 70 m.p.h. is observed
to descend steeply with the engine shut off. When it has travelled
600 //. measured horizontally, it is only 100 //. above the ground.
What is its probable speed at this point if its resistance is I in 6
at 70 m.p.h. and increases as Vz?
Problems of this character should always be visualized by
diagrams and may most readily be solved graphically.
Thus, from the diagram, it is apparent that if the glide had
been accomplished at 70 m.p.h. against i in 6 resistance, the
descent would have been 100 ft. in a distance of 600 ft. There is
thus 400 ft. loss of altitude unaccounted for by resistance and
this head must, therefore, be producing acceleration.
The head through which a body would have to fall in vacuo
to acquire 70 m.p.h. or (1-46x70)= say, 100 ft. sec. (approx.) is :
H=v2-f-2g=(ioo) 2-^-64 = 156 ft.
A graph of H=v2/2g is drawn over a suitable range of speeds,
and above this is plotted a curve representing the additional
head required to overcome resistance « v2. This curve starts
100 ft. above the first curve at 100 ft. /sec., and the subsequent
heights above the first curve are made proportional to the squares
of the speeds. Thus (ioo)2 corresponds to 100 ft. /. (no)2
=120 ft. ; (120)2 = 145 ft. ; (130)2 = 170 ft., etc.
The total head under consideration is 156 ft., representing
the initial velocity, -fioo ft. representing the initial resistance
+400 ft. representing the acceleration, =656 ft. A horizontal
332
AVIATION
line drawn at this altitude on the chart intersects the resistance
curve above the speed of 160 ft./sec. = no m.p.h., which is thus
an estimate of the probable speed at the moment under considera-
tion.
" Flight" Copyright Drawing
Graphic solution to the above problem.
Whereabouts, approximately, would the c.p. on the wings be
situated at no m.p.h., assuming the wing section to be that repre-
sented by the graphs on p. 321 and p. 319. The machine weighs
2000 Ibs. and has 6io//.2 wing area.
In horizontal flight the wing loading would be (2000-^-610)
=3-3 ft. Ibs.2, but owing to the sloping descent less than the
full weight of the machine is air-borne.
The tangent of the angle of descent is given by the fall of
500 ft. in 600 ft. =£=0-835 = tan 40°. That is to say, the
slope is 40° to the horizontal. The air-borne weight on the
wings is proportional to the cosine of the slope ; cos 40=076.
.'. the wing loading =076x3 -3— 2-5 lbs./ft.2
Thus P = C-v2-CX-xno2-2-
2-5x400
-=0-083.
2
(no)
NUMERICAL EXAMPLES 333
From the graph on p. 321 a coefficient 0-083 corresponds to
nearly — J° angle of incidence, and from the graph on p. 319 the
c.p. at — i° is about 0-65 of the chord from the leading edge ;
that is to say, it is appreciably aft of the middle of the wing.
In the above, suppose the wing chord measures 6 ft.: the front and
rear spars being I //. and 4 ft. 6 ins. from the leading edge respec-
tively. Compare the loads on the two spars at 9° and — J° angles of
incidence.
At 9°, the c.p. is about -27 of the chord for the front.
0-27x6 ft. = 1-62 ft.
The c.p. is thus 0-62 ft. behind the front spar and 2-88 ft. from
the rear spar.
The loads on the spars, which are 3-5 ft. apart, are inversely
as the distance of the c.p. from each.
CQ
Thus the front spar carries — • =82%
«j 0
0-62 0_,
and the rear spar carries = 10%.
At — J°, the c.p. is about 0-65 of the chord from the front :
thus, 0-65x6 ft. =3-9 ft.
The c.p. is thus 2-9 ft. behind the front spar and 0-6 ft. in front
of the rear spar.
It is obvious, without further calculation, that the distribu-
tion of the load is reversed, the rear spar now carrying over
82% of the total load.
It is apparent, therefore, that the rear spar must be at least
as strong as the front spar for the above arrangement. If the
rear spar were further forward it would be liable to carry more
load than the front spar.
If this fine angle is only acquired on steep slopes, there will be
a reduction of the total air-borne load, as explained in a former
example. On a slope of 40° the load supported by the wings is
76% of the total weight of the machine, in which case the load
on the rear spar becomes -76 X -82 =62% of the total. This
apparent advantage, however, might readily disappear under
the sudden stress of flattening out.
Discuss the question of a limiting speed for an aeroplane descending
headlong.
Suppose the normal speed of the machine is V m.p.h., and that
its resistance at this speed is J W. From the curve on p. 321 it
appears reasonable to assume that the inclusive resistance of a
machine in flight increases as the square of the speed at high
speeds
334 AVIATION
When falling headlong vertically, the propelling force of the
earth's attraction is equal to the weight of the machine.
Steady motion will thus be attained when the normal resist-
ance J W is increased to W, i.e. to 6 times its original value.
As the resistance is assumed to increase as V2, the velocity
required will be <v/6V=2-45V. That is to say, the limiting speed
for the case in question would be about 2j times the normal
flying speed.
It is required to absorb by springs giving 9 ins. compression
the shock of landing a machine which alights at 40 m.p.h. while
gliding on a slope of i in 6 without flattening out. Calculate the
force on the springs.
The rate of vertical descent is Jx (1-46x40) =9-8 ft. /sec.
The distance in which this velocity of impact is reduced to
zero is 0-75 ft.
From the fundamental formula v = v/2f H
v
the retardation f = -jr» where H is the compression range of
the spring and v is the initial velocity.
W
The force of a blow =mf, where m= mass = — (Ibs.).
W, WX64
Thus — f = — -7=2W.
g 32
That is to say, the force of the blow is equal to twice the weight
of the machine.
A flat rudder plate of 12 ft.2 area is pivoted 30 ft. from the e.g. of
the aeroplane. What is the couple produced by moving the rudder 10°
when the machine is flying at looft./sec. ?
According to the graph on p. 306 a flat plate at 10° gives a
pressure coefficient of about 0^43.
The total pressure P = C-Av2
_o-43Xi2X(ioo)2
400
= 129 Ibs.
The couple = 129x30 ft. =3770 Ib. ft.
NUMERICAL EXAMPLES
335
A propeller exerting a thrust of 360 Ibs. is situated 18 ins. above
the centre of resistance. What downward force on a tail plane
30 //. to the rear will balance the couple ?
The couple due to the propeller is (300 X 1-5) Ib. ft. That due
to the tail is (PX3O) Ib. ft.
In the above, the machine weighs 2000 Ibs. How far behind the c.p.
should the e.g. be situated to balance the propeller thrust ?
As before, couple due to thrust = (300x1 -5) Ib. ft.
and couple due to e.g. = (x X 2000) Ib. ft.
300x1-5
^ =0-225 ft. =2 7 ins.
x=
200O
An aeroplane capable of 70 m.p.h. steers due north in a wind of
30 m.p.h. blowing across its path at 60°. What is its course, and
in what direction should it steer to proceed due north?
The problem is best solved graphically as below by drawing
vectors representing the relative motion of the machine and
wind to scale. The resultant course and speed are measured off
the diagram to scale.
2O 30 4O 5O M.PH
HORIZONTAL
IN CALM
IN W//VD
WIND 5O M.PH
' ' Flight " Copyright Dra-wtHf
Diagram illustrating the graphic solutions to these problems.
A machine flying at 70 m.p.h. against a 30 m.p.h. wind descends
at that speed on a slope of I in 4 to the relative wind. What is its
apparent path to an observer on the ground?
As before, the problem is solved graphically. It is important
to recognize how a head wind increases the steepness of the
apparent descent. The attitude of the machine itself, however,
is unchanged.
336
AVIATION
By what force does an aeroplane steer a circular course?
Solely by the centripetal force obtained from a banked attitude;
the centripetal force being the horizontal component of the wing
pressure in this position.
Compare and discuss the centripetal forces under various con-
ditions.
Consider for a moment the accompanying diagrams, which are
supposed to represent the forces as seen in an end-on view of an
approaching aeroplane. Fig. i shows the lift, P, equal to the
weight, W, the wings being level. In Fig. 2 the wings are canted
to 45°. As the pressure remains at right angles to the wing spar,
its direction is tilted in sympathy with the bank. Assuming the
Flight" Copyright Dra-wint
Diagrams illustrating- the centripetal forces that steer an aeroplane
when it is banked.
relative air speed to be unchanged, the magnitude of the pressure
will be the same as before. In its new direction it is unable to
support the entire load of the weight, a fraction of which thus
initiates downward acceleration.
But there is now a horizontal component of the pressure caus-
ing acceleration to the left (supposing the machine to be advanc-
ing out of the plane of the paper towards the spectator) and this
centripetal force is opposed by the equal centrifugal force as the
machine proceeds along its appropriate circular path.
For the particular speed, there is a particular radius that will
provide the proper centrifugal force to balance the centripetal
force due to the bank, and the circular path corresponding to
this radius the machine automatically pursues without any aid
from the rudder.
While the bank, represented in Fig. 2, is being established, the
radius of the turning circle is diminishing ; when the bank is
NUMERICAL EXAMPLES 337
fixed, the centre of the turning circle is also fixed. The
conditions of Fig. 2 may thus represent the beginning of the
turn, or any instantaneous position during the turn.
It will be understood, therefore, that Fig. 2 represents a state
of turning on a circular path, accompanied by an accelerated
descent due to the weight being insufficiently supported. This
latter is, of course, a possible source of danger at low altitudes
when the ground may intervene to prevent the proper comple-
tion of the turn. If the lift should be reduced for any reason,
the unsupported fraction of the weight is increased at the
same time that the radius of turning increases, as shown in
Fig- 3-
In order to turn on the same level, it is necessary to increase
the speed or the angle of incidence, which may mean increasing
the power output. Reserve power is in any case a primary
factor of safety for turning.
In Fig. 4 is shown the case of a 15° bank, with increased pres-
sure sufficient to support the load and maintain a rather wide
turning circle. In Fig. 5 the increase in the wing pressure needed
to support a 30° bank is indicated, and in Fig. 6 the bank is
again 45°, as in Figs. 2 and 3. The pressure, it will be observed,
is nearly one-third greater than normal. If P <x V2, then
the velocity required represents an increase of about 15 per
cent.
Beyond the angle of 45° the wing pressure needed to support
the load plus the centrifugal force increases very rapidly, as is
shown in Fig. 7. For a bank of 60° the wing pressure is about
twice the normal, for 70° it is about three times the normal, and
for 80° it is about six times the normal value.
For a bank of 45° the centrifugal force is equal to the weight
supported against gravity. The radius of a given bank increases
as the square of the speed needed for the support of the load
due to the centrifugal force and the weight.
Thus, if a bank of 45° is completely supported at 80 ft. per
second, the radius of the turning circle is 200 ft. ; if a lower
loading permitted the same bank to be maintained at 60 ft. per
second the radius would be reduced to about 112 ft.
The question of a small turning circle depends on the reserve
power that can be converted into extra wing pressure. Other
things being equal, the lower speed machine will manoeuvre in
the least radius and will be able to put about in the least
time.
The calculations for radius of turning circle are as
follows :
Centripetal Force : F=P sin <f>,
where P=wing pressure ; <£= angle of bank.
22
338 AVIATION
If machine is to maintain the same level while turning, either
the speed or the angle of incidence must be increased to make :
r_ W
cos <j>
.*. turning without descent :
_ W sin <f>
F = T-*-=W tan <£.
cos 9
For the special case of 45°, tan 45° = i. /. F=W.
The centrifugal force of any object W turning at v ft. /sec. in
a circle of radius r is :
F=Wv2/gr.
Fundamentally: — Centrifugal force = Centripetal force.
/. W tan <£=Wv2/gr.
.'. r = v2/g tan <£, for any angle of bank <£
and for the special case of 45°, where tan </> — i
r = v2/g.
For example, when v=8o ft. /sec.
1=6400/32=200 ft.
and when v=6o ft. /sec.
1=3600/32 = 112 ft.
What reserve power is required to turn on a bank of 45° without
descending ?
The wing pressure required to maintain the same level is
W W ...
P = — — 5 = — — = I«42W.
cos 45 0707
The reserve power necessary to obtain this increase in wing
pressure depends entirely on the prevailing attitude of the
machine and whether it is necessary to increase the speed or
merely to increase the angle.
If the machine is already flying very fine with the wings at an
inefficient angle, increasing the angle will improve the efficiency
of the wings, which will compensate more or less for the increased
pressure.
Thus, suppose the wing shown in the graph on p. 321 is flying
at 2° incidence, where the left coefficient is about 0-2. Then
increasing the coefficient to (1-42x0-2) =0-285 will call for am
angle of about 5°. The liftresistance ratio in this latter attitude
is about 12, whereas formerly it was only 9.
The effect, so far as the wings are concerned, is thus from a*
resistance of (\ X i) =o-nW to a resistance of (T^ X 1-42) =o-u8W.
That is to say, there is an increase of only 7%.
On the other hand, had the wings been flying in their attitude off
maximum lift: resistance ratio, any alteration would involve a loss;
in lift:resistance ratio and consequently a very serious increase
in power required. If the lift;resistance ratio remained un-
NUMERICAL EXAMPLES 339
changed the increase in the wing pressure by 42% would involve
a corresponding increase in the power output at the same speed.
A consideration of this problem shows how fundamentally
important it is to provide aeroplanes with sufficiently powerful
engines, because even the initial assumption in the above
estimate presupposed the machine to be flying faster than its
speed of least resistance and, therefore, of having sufficient
reserve power for this purpose.
What is the magnitude of the gyroscopic couple produced by the
rotary engine and the propeller on an aeroplane that changes its
course by 90° in 4 seconds? The data relating to the engine and
propeller are as follows :
Engine. Weight W=28o Ibs.
Radius of gyration A =0-7 ft.
Revs, per min. = i20O.
Propeller. Weight W= 32 Ibs.
Radius of gyration X =2 -5 ft.
Revs, per min.=i2OO.
Gyroscopic couple M=mA2W12.
Where M=mass, A = radius of gyration, W= angular velocity
of rotation in radians per sec., 12=precession or angular velocity
of displaced axis.
Engine :
W 280 _
m=— = — =8-75
g 32
12=90° in 4 sees. =i rev. in 4x4 = 16 sees.
, i
.'. revs. /sec. = —
10
.% M=mA2wi2
=875x0-49x125x0-395
=212 Ib. ft.
Propeller : —
A2=2-52=6-2
W 12 as for the engine.
= i -o x 6-2 X 125 x o -395
=305 Ib. ft.
Total M = 212+305 = 517 Ib. ft.
At a radius of 20 ft. the force is — -=26 Ibs.
20
340 AVIATION
On an elevator of 13 sq. ft. area at this distance from the e.g. the
pressure required to counteract couple is 2 Ib. /ft. z nearly.
It is apparent that, for the case in question, the control
needed to counteract the gyroscopic couple is not more than
might ordinarily be required to meet disturbances due to gusts.
Further, the gyroscopic couple does not come unexpectedly.
It is interesting to note that the couple due to the propeller
alone may be more than that due to the rotary engine alone.
Assuming a flight speed of 69 m.p.h., what radius and bank
would satisfy the hypothesis of the previous problem ?
In the previous problem, the machine turns 90° in 4 sees.
.*. it completes the circle in (4X4)=i6 sees.
circumference
But —. — r— — = time = 10 sees.
velocity
2vrr
— 16.
v
_ i6v _ 16 x (69 x i -46)
~ 27r ""2x3-14 ~
=260 ft.
Turning at (69 X 1-46) =100 ft. sec. on a radius of 260 ft. creates
a centrifugal force :
Wv2 W(ioo)2
F = = — - — 7r-=i-2iW,
gr 32 X 260
which requires a corresponding centripetal force :
F=Wtan 0 = i-62W
.'. tan 0 = 1-21.
/. 0 = -5o°.
Where 0 = angle of bank. It is evident that the conditions
are exceptionally severe.
What is the direction of the gyroscopic couple ?
Draw in plan view the shaft and the rotating mass. Mark]
an arrow on the latter showing its rotation, then indicate the
angular precession of the axis by another arrow. The gyroscopic j
couple will tend to place the rotating mass so that its arrows j
correspond to those drawn to indicate the precession.
The above may perhaps be memorized by the phrase " Rotation
replaces precession."
NUMERICAL EXAMPLES 341
What is the theoretical limit to the increase in the static thrust of
a propeller when the power applied to the shaft is doubled ?
The theoretical limit to the thrust/power ratio of a
propeller is based on the assumption of a uniform slip stream
v ft. /sec. through the entire disc area A = (D2 /4) ft.2.
The thrust F=mv
m = mass /sec. =/>Av *
The minimum energy per second in the slip stream
ft. Ibs./sec.
Av3
H.P.
800 x 550
Since the power h. p. ocv3, .*. voc *J h.p.
And since the thrust <x v2, .'. Fee ( */ h.p.) *« h.p. <xh.p.°-66.
Thus if the energy is doubled the thrust is increased 2°-66 times
2o.66. 0.55 i0g 2=o-66x-3oi=o-2=log 1-59
i.e. the thrust is increased 59%.
As this calculation takes no account of blade friction, turbulence,
and other losses that are likely also to increase simultaneously, the
actual gain in thrust would be considerably less than this estimate.
A graph drawn to represent h.p. serves, however, as a
very useful datum line for the comparison of static thrust tests,
but such tests are in themselves of no particular value.
The above example is given primarily as an illustration of the
fundamental relationship between force and energy in fluids. It is
applicable only where the boundary of the stream can be denned.
In respect to propellers, it is useful as emphasizing the importance
of having a sufficiently large diameter for slow speed flight.
What is the theoretical limit to the efficiency of a propeller in flight ?
Neglecting turbulence and blade friction as in the previous
example,
The work lost in the slip stream = Jmv12
The useful work done=Fv=mv1v
V!=slip stream velocity, v= flight speed ; F= thrust.
The mass in both cases = |"-A(Vi4-v)"j
The total work done = [Jmv12+niv1v]
~ . _ useful work_ mvjV
~ total work [Jmv12-fmv1v]
v flight speed
""[Jvx+v] ~[J slip-f flight-speed]
342
AVIATION
For a given propeller it is apparent that the theoretical limit
to the efficiency increases with the flight speed.
Suppose the slip stream velocity = 20% of the flight speed:
then Vi=o-2v
Draw a plan indicating the places within reach of a one hour's
flight on an aeroplane when there is a real wind of greater velocity
than the speed of the machine.
"Flight " Copyright Dra-wing
Diagram illustrating graphic solution to above problem.
At one extremity of a line representing the wind to scale and
direction draw a circle of radius representing the real air speed
of the machine to scale. Draw tangents from the circle to the
other end of the wind line. Any point within the boundaries is
within reach of an hour's flight starting from this end of the
wind line.
A certain wing has been chosen for an aeroplane and its charac-
teristic shows that 600 ft.z of area will be required to support
the load in flight. What allowance must be made for biplane con-
struction if the gap is equal to the chord ?
The loss in lift coefficient with biplane construction, gap
= chord is about 17%.
.'. area required = (600+17x6) =702 ft.2
What is the approximate range of vision at 1000 //. altitude ?
Range (miles) =A/H-f 75H where H= altitude
= Viooo-f 75o =
=42 miles.
NUMERICAL EXAMPLES 343
Compare the maxima local forces on the top and bottom of a wing
at looft./sec.
Tests show that one may expect a local intensity of suction
= (-i-5/>v2)
The maximum pressure on the bottom surf ace =o -5/0 v2
P o-5X(ioo)a
.'. o-5-v2=^L- — 1-=i2-5lbs./ft.2
°g 400
.'. the probable suction at some point on the upper surface
=3Xi2-5=37-5lbs./ft.2
As 100 ft. /sec. =69 m.p.h. the above would be quite a usual
local stress on the wing fabric.
At no m.p.h., which, might be acquired during a dive, the
local stress might be
i-5x(iioxi-46)'_i-5X(i6o)« 2
400 400
As this local intensity at some point is liable to occur on any
wing at that speed, the necessity for a secure fabric fastening and
strong ribs is clearly indicated. The fabric itself, unless deterior-
ated, is usually amply strong for its purpose.
A machine travelling at 50 m.p.h., rolls in flight so as to depress
one of its wings 18 ins. in a second. What is the alteration in
the effective angle of wing tip incidence during this action ?
Speed of machine =73 ft. /sec.
Descent of wing tip =1-5 ft. /sec. for I ft.
/. in 73 ft. wing tip descends 1-5 ft.
.*. tangent of angle of virtual inclination =—=0-025 nearly
=tan ij° approx.
That is to say, the angle of incidence at the tip is virtually
increased ij° while descending. Similarly, the other wing tip
is virtually reduced by this amount.
344
AVIATION
SYMBOLS EMPLOYED WITH
THROUGHOUT
A = area ft.2
C = the constant for air pres-
sure in absolute units
=0-62 for a large flat
plate.
D = diameter.
F=force.
H=head.
L= length
P= pressure.
V=speed m.p.h.
W = weight.
A UNIFORM SIGNIFICANCE
THIS BOOK
f — acceleration ft. /sec. /sec.
g = gravity =32-2 ft. /sec. /sec.
k = a coefficient.
W
m=mass=—
g
v = velocity ft. /sees.
6 = angle of incidence.
v= kinematic viscosity.
circumference
TT= — -jr— — =3-14159.
diameter
p = density =0-08 Ibs. /ft.3 for
air.
com angular velocity radians/
sec.
LETTERS OF THE GREEK ALPHABET COMMONLY EMPLOYED AS
MATHEMATICAL SYMBOLS
a — alpha. #=theta. p = rho.
/3=beta. A— lambda o- = sigma
7=gamma. /z = mu. r = tau.
8 = delta. v = nu. <£ = phi.
e=epsilon £=xi. ^=psi.
£=zeta. 7r=pi. to
LIFT COEFFICIENT CONVERSION FACTORS
Wherever an absolute lift coefficient is given, either in this
book or elsewhere, it may, for approximate purposes, be con-
verted into ''pounds lift per square foot of wing area " by
multiplying by 0-0051 V2 ; where V is the flight speed in m.p.h.
The following table gives useful values of the conversion
factor for several speeds :
V m.p.h.
0-0051 V2
40
8-15
50
60
127
18-3
70
80
25-0
32-6
90
4i-5
IOO
51-0
e.g. A lift coefficient of 0-25 corresponds to (0-25x25) =6-25
Ibs. per sq. ft. at 70 m.p.h. under normal atmospheric conditions.
TABLES
345
LENGTH
i in. =25-4 cms.
i ft.= 0-305 m.
i yd. = 0-914 m.
i mile = 5280 ft.
= 1760 yds.
= 1-61 km.
sea mile =6080 ft.
Equator =60 sea mi.
i m.= 3-28 ft.
AREA
i ft.2 = 144 in.2
=0-093 m.2
i m. 2 = 1076 ft.2
i yd.2 =0-836 m.2
i acre =4840 yds.2
=4046-7 m.2
i sq. mile =640 acres.
WEIGHT
i oz.=28-35 grammes
i Ib. =16 oz.
=0-4536 kg.
=445,000 dynes
I ton =22 40 Ibs.
= 1016-05 kg.
i U.S.A. ton =2000 Ibs.
i kg. =2 -2 Ibs.
=981,000 dynes
COUPLES
i kg. m. =7-25 Ibs. ft.
i Ib. ft. =0-138 kg. m
PRESSURE
i kg. /m.2 =0-205 Ibs. /ft.2
i Ib. /ft. 2=4-9 kg. /m.2
i Ib. /in. 2=0-07 kg. /cm.2
=68,976 dynes /cm.2
= 2-04"Hg. @62°F.
=2-3ft.H20 „
i"H20@62° F.=5-i961bs./ft.2
=0-073" Hg.
=65 ft. air
i atm.@62° F. =29-95* Hg.
=760 mm. Hg.
=33-94 ft. H20
=14 -76 Ibs. /in.2
= i X io8 dynes/cm.2
= •95 ton /ft.2
I kg. /cm. 2 = 14-223 Ibs. /in. 2
= -975 atm.
i oz. /yd. 2 =33 -9 grammes /m.2
KINEMATIC VISCOSITY
Air =0-147
Water =0-105.
346
AVIATION
VELOCITY
i m.p.h. =1-46 ft. /sec.
=88ft./min.
= 1-609 k.p.h.
i knot = 1-152 m.p.h.
i k.p.h. =0-6214 m.p.h.
=0-9113 ft. /sec.
i cm. /sec. =2 ft./min. (appx.)
i ft. /sec. =0-685 m.p.h.
i m. /sec. =2-25 m.p.h.
SOUND IN AIR 1142 FT. /SEC.
WIND
Altitude,
ft.
I,OOO
2,000
3,000
4,000
6,000
8,000
12,000
Velocity,
m.p.h.
10
20
25
28
30
32
35
DENSITY (p)
If sp. gr. water=i-oo
then Ib. /in. 3= sp.gr. X -036
i gramme /cm3 =62 -43 Ibs. /ft 3
i kg. /m3 =0-0623 Ibs. /ft.3
ilb./ft.3 = i5-8kgs./m.3
Air=o-o81bs./ft.3
= 1-29 kg./m.3
Hydrogen =0-005 Ibs. /ft.3
=0-0895 lbs./m.3
Coal gas =0-0403 Ibs. /ft. 3
=0-646 lbs./m.3
Water=62-5lbs./ft.3
= 10 Ibs. /gal.
Petrol (72 sp.gr.) =45 Ibs. /it.3
= 7-2 Ibs. /gal.
Ash =49 Ibs. /ft.3
Bamboo = 25
Cork = i5
Mahogany =40
Oak = 50
^ Pine =36
Spruce =31 ,,
Walnut =42 ,,
THE ATMOSPHERE
Altitude,
ft.
o
4,000
8,000
12,000
16,000
20,000
Density
P Ibs. /ft. 3
0-78
0-68
0-51
0-47
0-41
TABLES
347
POWER
i h.p. =375 mile Ibs./hour
=33000 ft. Ibs./min.
=550 ft. Ibs./sec.
= 77 -5 kg. metres /sec.
=0746 kilowatts
=42-416 B.Th.U./min.
(lb.°F.)
= 10-711 calories /min.
(kg0. C.)
=0-175 Ibs. carbon oxi-
dized/hour
= 2-64 Ibs. water evapor-
ated@2i2° F./hour
Joules equivalent : I B.Th.U.
=772 ft. Ibs.
TEMPERATURE
°C. =0-555 (°F.- 32)
°F.=32+(i-8°C.)
Absolute zero= - 459° F.
= -273°C.
The earth, increase in temp,
with depth -}- i° C. per 100 ft.
(approx.).
The atmosphere, decrease in
temp, with altitude : —
4000 ft. . . . -2j°F.perioooft
16000 ft. ...-3° F. „ „
17000 ft -3i°F. „ „
28000 ft. ...-4° F. „ „
VOLUME
i gal. =8 pts.
=160 fl. ozs.
=227-27 in.3
=o-i6ft.3
=4-546 litres
i U.S.A. gal. =231 in.3
I litre = -I m.3
= 1-76 pts.
=61-02 in.3
=0-22 gallon
i ft.3 = 1728 in.3
= 50 pints
= •0283 m.3
ANGULAR
i circle =360°
i radian = 360 °-^27r
=57-296°
(o = angular velocity
= radians /sec.
=27r re vs. /sec.
Revs . /sec . = w /2ir
ft.3
= 1-307 yds.3
i fluid oz. =480 drops H2O
i teapsoonful=6o drops (abt.)
DIMENSIONS
Velocity LT'1
Acceleration LT~2
Kinematic viscosity LZT~1
Density ML~3
Force MLT~2
348
AVIATION
Temperattire.
°Fahr. °Cent.
Cwts.
Weight.
Kgs.
Miles
per
gal.
Litres
per zoo
kiloms.
£
Exchange,
s. d. fr. c.
0 =
-18
5
—
254
5
=
55
0
0
I
= 0 10
IO =
— 12
10
=
508
6
=
48
0
0
2
= O 20
2O ==
- 7
12
=
610
7
=
40
o
0
3
= o 30
32 =
o
14
sss
712
8
=
36
0
o
4
= o 40
40 =
4
16
=
813
9
=
31
0
o
5
= ° 5°
50 =
10
18
—
915
IO
=
28
0
o
6
= o 60
60 =
16
20
;— - J
,016
ii
=
26
o
o
7
— o 70
70 =
21
22
— J
,118
12
=
23
0
o
8
= o 80
80 =
27
24
^^ I
,220
13
=
22
0
o
9
= o 90
90 =
32
26
= I
,321
J4
=
20
o
o
10
= 10
15
=a
19
IOO =
38
28
= I
,423
16
=
18
o
0
ii
= I 10
no =
43
30
= I
,524
J7
s=
17
0
I
0
= I 20
I2O =
49
32
= I
,626
18
=
16
o
2
o
2 50
I30 =
54
34
= I
,728
19
=
15
0
3
0
= 37°
I40 =
60
36
= I
,829
o
4
0
= 50
20
=
M
150 =
65
38
= I
,93i
21
13-5
0
5
0
= 6 30
160 =
7i
40
= 2
,032
22
=
13-0
0
6
0
= 7 50
Lyo =
77
42
— "2
.134
23
=
12-0
0
7
o
= 8 80
1 80 =
82
44
• ; 2
,235
24
=
n-5
0
8
o
= IO O
190 =
88
46
= 2
,337
25
=s
1 1 -2
o
9
o
= II 30
26
=
10-8
200 =
93
48
r— 2
,438
27
=
10-4
o
10
0
= 12 50
212 =
IOO
5°
= 2
,54°
28
=
IO-O
I
o
o
= 25 o
220 =
104
52
= 2
,640
29
=
9-6
2
o
0
= 5° °
230 =
no
54
= 2
.74°
3
o
0
= 75 o
240 =
IJ5
56
Tr— r
,840
3°
=?
9-4
4
0
0
— IOO O
3i
=
9-i
5
o
o
= 126 o
250 =
121
58
= 2
,94°
32
=
8-8
10
o
o
= 252 o
260 =
126
60
= 3
,050
33
=
8-5
270 =
132
34
=
8-3
35
==
8-0
Surfaces —
Triangle
Circle
Sector
Parabola
Ellipse
Cone
Sphere
Volumes —
Cylinder
Sphere
Segment
Cone
Wedge
The Circle —
Circumference
Equal Square
Inscribed
The above tables are only approximate.
MENSURATION
= Base X | perpendicular.
=D2x-7854.
= Arcx| radius.
= Basexf height.
= Major axisx -7854 minor axis.
= Base area -j- (Base circ. x \ slant height).
-14159.
= Base area x length.
= •5236 Height (Height2 + 3 Base Radius).
= Base area x \ perpendicular.
= Base area x \ perpendicular.
=-0x3-14159.
= 0x0-886226.
= D x 0-7071.
TABLES
349
Feet.
Metres.
Miles.
Kiloms.
Gallons.
Litres.
Lbs.
Kgs.
I
=
•3
I
= 1-6
I =
4'5
I
=
•45
2
- =
•6
2
= 3'2
2 =
g-0
2
—
•9
3
B=
•9
3
= 4-8
3 =
I3-6
3
=
i-4
4
=
1-2
4
= 6-4
4 =
18-2
4
=
1-8
5
=
i-5
5
= 8-0
5 =
22-7
5
=
2-3
6
=
1-8
6
= 9-6
6 =
27-3
6
=
27
7
=
2-1
7
= 1 1 -2
7 =
31-8
7
=
3'2
8
=
2-4
8
= 12-8
8 =
36-3
8
=
3-6
9
=
27
9
= 14-5
9 =
40-9
9
=
4-i
10
=
3-o
10
= 16-1
10 =
45-4
10
=
4'5
Cu.
ins.
Cu.
cms.
fe
Sq.
metres.
Per
Ib.
s. d.
Per
kilog.
fr. c.
Per
yard,
s. d.
Per
metre,
fr. c.
I =
16-3
i
= -09
I O
= 2 80
10 =
I 40
2 =
32-7
2
= -18
2 0
= 5 60
20 =
2 80
3 =
49-1
3
= -28
3 o
8 40
30 =
4 15
4 —
65-5
4
= '37
4 o
= II 10
40 =
5 50
5 =
81-9
5
r -46
5 o
= 13 90
5 o =
6 90
6 =
98-3
6
= -56
6 o
= 16 70
60 =
8 30
7 =
1147
7
= -65
7 o
= 19 50
70 =
9 65
8 =
131-1
8
= 74
8 o
= 22 30
80 =
II 10
9 =
147-5
9
= -84
9 o
= 25 o
90 =
12 40
10 =
163-0
10
= -92
IO O
= 27 80
IO O =
13 80%
9 =
10 =
147-5
163-0
9 =
IO =
•84 9 o = 25 o
•92 10 o = 27 80
9
10
o =
o =
: 12 40
: 13 80k
Pressure.
Price of
Petrol.
Lbs.
per
sq. in.
Atmospheres
(or kilogs.
persq.
centimetre).
Metres
d'eau.
Per
gal.
s. d.
Per
litre.
C.
Per
bidon.
fr. c.
I
=
•07 =
07
O =
28
=
40
2
=
•14 =
!'4
I =
3°
=
5°
3
=
"2 ^^
2-1
2 -— ^
33
=
65
4
=
•27 =
2-8
3 -
35
=
75
5
=
•34 =
3'5
4 =
37
=
85
6
=
•41 =
4-2
5 =
39
=
i 95
7
=
•48 =
4'9
6 =
42
=
2 10
8
=
•54 =
5-6
7 =
44
=
2 20
9
=
•61 =
6-3
8 =
46
=
2 30
IO
=
•68 =
7-0
9 =
49
=
2 45
20
=
1-4 =
14-0
10 =
5i
=
2 55
3°
=
2-0 =
21-0
ii =
53
=
2 65
40
=
27 =
28-0
20 =
55
=
2 75
50
=
3'4 =
35 '°
21 =
58
as
2 90
60
=
4-1 =
42-0
22 =
60
=
3 °
70
=
47 =
49-0
23 =
63
=
3 15
80
=
5'4 =
56-0
24 =
65
=
3 25
90
=
6-1 =
63-0
25 =
67
=
3 35
100
6-8 =
70-0
26 =
69
3 45
The above tables are only approximate.
350
AVIATION
COMPASS
Miles Kiloms.
per per
MORSE CODE
P ' A 1
hour. hour.
oin s. ng e.
O 1 ' t
• ••
0
e — 8
B -• • •
i = 2 48 45
J °
10 = 16
C -•«>•
i = 5 37 30
15 = 24
D •••
| = 8 26 15
20 = 32
22 = 35
F • •-.
i = n 15 o
24 = 38
G »-•
ij = 14 3 45
26 = 41
H ••• •
28 = 45
I • •
ij = 16 52 30
30 48
J •---
if 19 41 T5
32 = 51
K -•-
34 54
L • — • •
2 — 22 30 O
36 = 57
M --
2i 25 18 45
38 = 61
N -•
O mm m m
2j 28 7 30
40 = 64
P •-.•
2| - 3° 56 15
42 67
44 = 71
Q ..«.
R« • •
3 = 33 45 °
46 = 74
9 ^B V
3i = 36 33 45
48 - 77
50 = 80
3 • • •
T -
3i = 39 22 30
52 = 83
U ••-
3f = 42 ii 15
54 = 86
56 = 90
V • • • .
W •--
4 = 45 o o
58 - 93
X -• •-
Y -.--
60 = 100
Z --• •
64 = 103
66 = 106
68 = no
NUMERALS
70 =113
72' = 116
2 «•««-.
74 = H9
3 • • • • mm
76 = 122
•J
A •••••§
78 = I25
T^
5 • • • • •
80 = 128
6 •§••••
90 = 144
ioo — 160
7 mm mm m • •
105 = 168
no = 176
0 - - - - -
120 r= IQ3
TABLES
351
FORMULA OF THE HYDROCARBONS, ETC., OF IMPORTANCE IN
CONNECTION WITH LIQUID FUEL
i. The paraffin series — CnH2n+2
Methane CH4 . bolts at ° C/
Ethane C2H6 .
. 1
Propane C3H8
t Vgas.
Butane C4H10 .
• J
Pentane C6H12 .
37
Hexane C6H14 .
69]
Spirit, the
Neptane C7H16 .
Octane C8H18 .
98 Vpetrol
. I20J
benzines or
naphthas.
Nonane C9H20 .
. 130
Decane C10H22 .
158^ Kerosene or lamp oil,
Undecane CuH24 .
180 " Solar " or Intermedi-
Duodecane Ci2H26 .
200 ate oil,
etc. etc.
Lubricating oil,
C17H36 .
Vaseline,
etc. etc.
Wax.
2. The Olefine series CnH2n
Ethylene CaH4
etc. etc.
3. The Acetylene series CnH2n_2
Acetylene C2H2
etc. etc.
4. The Benzene series CnH2n_6
Benzene C6H6 boils at 81° C.) -r> ,
Tolvene C,H8 „ in }BenzoL
Xylene C8H10
etc.
5. Naphthalene CnH2n_12
Naphthalene C10H8 boils at 218° C.
6. Alcohol C2H6OH
Methylic Alcohol CH4O boils at 63° C.
Ethylic „ C2H6O „ 78° C.
COSECANT 0 " Flight" Copyright Drawing
Diagram illustrating- the trigonometrical ratios.
352
AVIATION
ALTITUDE (METRES) Corresponding to Barometer mm.
Bar.
mm.
Mean Temperature, ° C.
20°.
10°.
0°.
-10°.
-20*.
770
-90
-87
-84
-8 1
-78
760
33
22
21
20
19
750
137
132
I27
123
118
740
252
243
235
227
219
730
369
356
344
332
320
720
488
471
455
439
423
710
608
587
567
547
527
700
730
705
680
656
632
690
854
825
796
767
738
680
980
946
913
880
847
670
,107
1,070
,032
994
956
660
.237
1,195
,152
,109
,067
650
,368
1,322
,275
,228
,181
640
,502
,450
,399
,348
,297
630
,637
,581
,525
,469
.4*3
62O
.775
,714
,654
.593
,532
610
,915
,850
,784
,718
.653
600
2,057
,987
,917
.847
.777
590
2,202
2,127
2,052
.977
,902
580
2,349
2,269
2,189
2,109
2,029
57°
2,499
2,414
2,328
2,243
2,158
560
2,651
2,56l
2,470
2,380
2,290
550
2,807
2,711
2,615
2,519
2,423
54°
2,965
2,863
2,762
2,661
2,560
530
3,126
3,019
2,912
2,805
2,698
520
3,290
3,177
3,065
2,953
2,841
510
3,457
3,339
3,221
3,103
2,985
500
3,628
3,5°4
3,380
3.256
3,132
490
—
3,672
3,542
3,4*2
3,282
480
—
3,843
3,708
3.572
3.436
47°
—
4,019
3,876
3,734
3,592
460
—
4,198
4.049
3.9oi
3,753
45°
—
4.380
4,226
4,071
3.9i6
44°
—
4.567
4,406
4.245
4.083
430
—
4.759
4,591
4.422
4.253
420
—
4.955
4,780
4,604
4,428
410
—
5,155
4.973
4.791
4,608
400
— .
5,36i
5,i7i
4.982
4.792
390
-=—
5,572
5,375
5.178
4.98i
380
—
5,788
5,583
5.379
5.174
37°
—
6,010
5,797
5,585
5,372
360
—
6,238
6,017
5,797
5,576
350
—
6,473
6,244
6,015
5,786
34°
—
6,714
6,477
6,239
6,002
33°
— •
6,963
6,716
6,470
6,224
320
— •
7,219
6,964
6,709
6,453
310
—
7.483
7,219
6,954
6,690
300
—
7,757
7,482
7,208
6,934
290
—
8,039
7.755
7.471
7,186
280
—
8,331
8,037
7.742
7.448
270
—
8,634
8,329
8,024
7,718
260
—
8,949
8,633
8,317
8,000
250
—
9,276
8,948
8,620
8,292
200
—
ii,i53
10,742
10,348
9,954
150
—
13.536
13,058
12,579
12,101
IOO
—
16,925
16,327
15,729
15,130
50
—
22,717
21,914
21,110
20,308
TABLES
SINES AND TANGENTS
353
Degs.
Sine.
Tangent
Degs.
Sine.
Tangent.
O
•ooooo
•OOOOO
90
46
•71934
1-03553
44
I
•01745
•01746
89
47
•73135
1-07237
43
2
•03490
•03492
88
48
•74314
i-iio6i
42
3
•05234
•05241
87
49
•75471
I-I5037
41
4
•06976
•06993
86
50
•76604
1-19175
40
5
•08716
•08749
85
51
•77715
1-23490
39
6
•10453
•I05IO
84
52
•78801
1-27994
38
7
•12187
•12278
83
53
•79864
1-32704
37
8
•13917
•14054
82
54
•80902
1-37638
36
9
•J5643
•15838
8l
55
•8I9I5
1-42815
35
10
^7365
•17633
80
56
•82904
1-48256
34
ii
•19081
•19438
79
57
•83867
I-53987
33
12
•20791
•21256
78
58
•84805
1-60033
32
13
•22495
•23087
77
59
•85717
1-66428
3i
14
•24192
•24933
76
60
•86603
1-73205
30
15
•25882
•26795
75
61
•87462
1-80405
29
16
•27564
-28675
74
62
•88295
1-88073
28
17
•29237
•30573
73
63
•89101
1-96261
27
18
•30902
•32492
72
64
•89879
2-05030
26
19
•32557
•34433
71
65
•90631
2-14451
25
20
•34202
•36397
70
66
•91355
2-24604
24
21
•35837
•38386
69
67
•92050
2-35585
23
22
•37461
•43403
68
68
•92718
2-47509
22
23
•36073
•42447
67
69
•93358
2-60509
21
24
•40674
•44523
66
7°
•93969
2-74748
20
25
•42262
•44631
65
7i
•94552
2-90421
19
26
•43837
•48773
64
72
•95106
3-07768
18
27
'45399
•50593
63
73
•95630
3-27085
17
28
•46947
•53I7I
62
74
•96126
3-48741
16
29
•48481
•55431
61
75
•96593
3-73205
15
3°
•50000
•57735
60
76
•97030
4-01078
J4
31
•51504
•60086
59
77
•97437
4-33I48
13
32
•52992
•62487
58
78
•97815
4-70463
12
33
•54464
•64941
57
79
•98163
5-14455
II
34
•55919
•67451
56
80
•98481
5-67128
10
35
•57358
•70021
55
81
•98769
6-3I375
9
36
•58779
•72654
54
82
•99027
7-"537
8
37
•60182
•75355
53
83
•99255
8-14435
7
38
•61566
•78129
52
84
•99452
9-5I436
6
39
•62329
•80978
5i
85
•99619
11-43005
5
40
•64279
•83910
50
86
•99756
14-30067
4
41
•65606
•86929
49
87
•99863
19-08114
3
42
•66913
•90040
48
88
•99939
28-63625
2
43
•68200
•93252
47
89
•99985
57-28996
I
44
•69466
•96569
46
90
I -OOOOO
Infinite
O
45
•70711
I -OOOOO
45
Cosine.
Con tangent.
Degs.
Cosine.
Contangent.
Degs.
COSINES AND CONTANGENTS
354
AVIATION
LOGARITHMS
No.
0
1
2
3
4
5
6
7
8
9
10
oooo
0043
0086
0128
0170
0212
0253
0294
°334
°374
11
0414
°453
0492
0531
0569
0707
0645
0682
0719
°755
12
0792
0828
0864
0899
°934
0969
1004
1038
1072
1106
13
1139
H73
1206
1239
1271
I3°3
1335
1367
1399
1430
14
1461
1492
1523
1553
1584
1614
1644
1673
1703
*732
15
1761
1790
1818
1847
1875
1903
1931
1959
1987
2014
16
2041
2068
2095
2122
2148
2175
2201
2227
2253
2279
17
2304
2330
1355
2380
2405
2430
2455
2480
2504
2529
18
2553
2577
2601
2625
2648
2672
2695
2718
2742
2765
19
2788
2810
2833
2856
2878
29OO
2923
2945
2967
2989
20
3010
3032
2054
3075
3096
3II8
3139
3160
3181
3201
21
3222
3243
3263
3284
3304
3324
3345
3365
3385
34°4
22
3424
3444
3464
3483
35°2
3522
3541
356o
3579
3598
23
3617
3636
3655
3674
3692
3711
3729
3747
3766
3784
24
3802
3820
3838
3856
3874
3892
3909
3927
3945
3962
25
3979
3997
4014
4°3!
4048
4065
4082
4°99
4116
4133
26
4150
4166
4183
4200
4216
4232
4249
4265
4281
4298
27
4314
4330
4346
4362
4378
4393
4409
4425
444°
4456
28
4472
4487
4502
45i8
4533
4548
4564
4579
4594
4609
29
4624
4639
4654
4669
4683
4698
4713
4728
4742
4757
30
4771
4786
4800
4814
4829
4843
4857
4871
4886
4900
31
4914
4928
4942
4955
4969
4983
4997
5011
5024
5038
32
5051
5065
5079
5092
5105
5H9
5132
5145
5159
5*72
33
5185
5198
5211
5224
5237
5250
5263
5276
5289
5302
34
5315
5328
534°
5353
5366
5378
5391
54°3
54J6
5428
35
5441
5453
5465
5478
5490
55°2
5514
5527
5539
5551
36
5513
5575
5557
5599
5611
5623
5635
5647
5658
5670
37
5682
5694
57°5
5717
5729
574°
5752
5763
5775
5786
38
5798
5809
5821
5832
5843
5855
5866
5877
5888
5899
39
59ii
5922
5933
5944
5955
5966
5977
5988
5999
6010
40
6021
6031
6042
6053
6064
6075
6085
6096
6107
6117
41
6128
6138
6149
6160
6170
6180
6191
6201
6212
6222
42
6232
6243
6253
6263
6274
6284
6294
6304
63M
6325
43
6335
6345
6355
6365
6375
6385
6395
6405
6415
6425
44
6435
6444
6454
6464
6474
6484
6494
6503
6513
6522
45
6532
6542
655i
6561
6571
6580
6590
6599
6609
6618
46
6628
6637
6646
6656
6665
6675
6684
6693
6702
6712
47
6721
6730
6739
6749
6758
6767
6776
6785
6794
6803
48
6812
6821
6830
6839
6846
6857
6866
6875
6884
6893
49
6902
6911
6920
6928
6937
6946
6955
6964
6972
8681
50
6990
6998
7007
7016
7024
7033
7042
7050
7°59
7067
51
7076
7084
7093
7101
7110
7118
7126
7135
7M3
7152
52
7160
7168
7177
7185
7193
7202
7210
7218
7226
7235
53
7243
7251
7259
7267
7275
7284
7292
7300
7308
73J6
54
7324
7332
734°
7348
7356
7364
7372
7380
7388
7396
TABLES
LOGARITHMS— continued
355
No.
0
1
2
3
4
5
6
7
8
9
55
7404
7412
74J9
7427
7435
7443
745i
7459
7466
7474
56
7482
7490
7497
75°5
7513
7520
7528
7536
7543
755i
57
7559
7566
7574
7582
7589
7597
7604
7612
7619
7627
58
7634
7642
7649
7657
7664
7672
7679
7686
7694
7701
59
7709
7716
7723
7731
7738
7745
7752
7760
7767
7774
60
7782
7789
7796
7803
7810
7818
7825
7832
7839
7846
61
7853
7860
7868
7875
7882
7889
7896
7903
7910
7917
62
7924
793i
7938
7945
7952
7959
7966
7973
798o
7987
63
7993
8000
8007
8014
8021
8028
8035
8041
8048
8055
64
8062
8069
8075
8082
8089
8096
8102
8109
8116
8122
65
8129
8136
8142
8i49
8156
8162
8169
8176
8182
8189
66
8i95
8202
8209
8215
8222
8228
8235
8241
8248
8254
67
8261
8267
8274
8280
8287
8293
8299
8306
8312
8319
68
8325
8331
8338
8344
8351
8357
8363
8370
8376
8382
69
8388
8395
8401
8407
8414
8420
8426
8432
8439
8445
70
8451
8457
8463
8470
8476
8482
8488
8494
8500
8506
71
8513
8519
8525
8531
8537
8543
8549
8555
8561
8567
72
8573
8579
8585
8591
8597
8603
8609
8615
8621
8627
73
8633
8639
8645
8651
8657
8663
8669
8675
8681
8686
74
8692
8698
8704
8710
8716
8722
8727
8733
8739
8745
75
8751
8756
8762
8768
8774
8779
8785
8791
8797
8802
76
8808
8814
8820
8825
8831
8837
8842
8848
8854
8859
77
8865
8871
8876
8882
8887
8893
8899
8904
8910
8915
78
8921
8927
8932
8938
8943
8949
8954
8960
8965
8971
79
8976
8982
8987
8993
8998
9004
9009
9015
9020
9025
80
9031
9036
9042
9047
9053
9058
9063
9069
9074
9079
81
9085
9090
9096
9101
9106
9112
9117
9122
9128
9133
82
9138
9143
9149
9154
9159
9165
9170
9175
9180
9186
83
9191
9196
9201
9206
9217
9212
9222
9227
9232
9238
84
9243
9248
9253
9258
9262
9263
9274
9279
9284
9289
85
9294
9299
9304
93°9
9315
9320
9325
9330
9335
934°
86
9345
9350
9355
9360
9365
9370
9375
9380
9385
9390
87
9395
9400
9405
9410
9415
9420
9425
9430
9435
944°
88
9445
9450
9455
9460
9465
9469
9474
9479
9484
9489
89
9494
9499
95°4
9509
9513
95i8
9523
9528
9533
9538
90
9542
9547
9552
9557
9562
9566
9571
9576
958i
9586
91
9590
9595
9600
9605
9609
9614
9619
9624
9628
9633
92
9638
9643
9647
9652
9657
9661
9666
9671
9175
9680
93
9685
9689
9694
9699
97°3
9708
9713
9717
9722
9727
94
9731
9736
9741
9745
9750
9754
9759
9763
9768
9773
95
9777
9782
9786
9791
9795
9800
9805
9809
9814
9818
96
9823
9827
9832
9836
9841
9845
9850
9854
9859
9863
97
9868
9872
9877
9881
9886
9890
9894
9899
9903
9908
98
9912
9917
9921
9926
9930
9934
9939
9943
9948
9952
99
9956
996i
9965
9969
9974
9978
9983
9987
9991
9996
INDEX
Accidents, 161, 225, 283
Ader, 204
Advisory Committee, 90, 94, 246
Aero Show, 246
Aeronautical Society, 93, 199
Alexander, 216
Angle of incidence, 24
Antoinette, 220
Anzani, 23
Archdeacon, 63, 133, 138, 218
Argyll, 199
Arlands, 186
Aspect, 12, 199
(T test), 12
Atlantic, 301
Aubrun, 241
Aubry, 167
Austro-Daimler, 23
Avro, 19, 23, 148, 150
B
Baden-Powell, 225
Balloons —
,, air, 182, 176
,, hydrogen, 179
first ascents, 185
Barber, 243
B.E.2, 22, 24
Beaumanoir, 184
Beaumont, 245
Besnier, 176
Bienvenu, 191
Biggin, 189
Birds, 65, 75, 89
Black, 179
Blackburn, 29
Blackpool, 241
Blanchard, 188
Bleriot, 26, 28, 33, 133, 150, 173, 219,
226, 232
Books, 253
Boomerang, 55
Borel, 159, 160
Borelli, 176
Bournemouth, 240
Brearey, 199
Breguet, 25, 35, 159
Brewer, 73, 225
Bristol, 18, 27, 147, 148, 150
Bryan, 53
Butler, 225
Cabre, 73
Calderara, 227
C.A.M., 235
Camber, 4
,, (v. flat plate), 8, 105
Garden, 144
Caudron, 32
Cavallo, 179
Cavendish, 179
Cayley, 8, 19, 85, 191
Centre of pressure, n, 13, 77, 318,
332
,, „ (retrogression), 15, 125,318
Centrifugal couple, 323
Channel, 173, 189, 244
,, first flight, 231
Chanute, 122, 123, 213
Charles, 184, 188
Chavez, 241
Chronology, 257
Circuit de 1'Est, 241
,, of Britain, 245
Clarke, 233
Climbing, 71, 330
,, and elevator, 72
Clubs, 251
Cockburn, 233
Cody, 23, 24, 28, 31, 82, 150, 227,
233, 243
Colliex, 133
Conneau, 173, 245
Control, 32, 168
,, elevator, 72
,, rudder, 168
,, warp, 33
Curtiss, 233
D
Daily Mail, 140, 219, 229, 239, 245
De Forest, 243
356
INDEX
357
Degen, 193
Delacombe, 241
Delagrange, 50, 132, 219, 223, 235
De Lambert, 227
De Lesseps, 239
Deperdussin, 31, 150, 159
Deschamps, 184
Dihedral, 20, 37, 52, 69, 105
Drexel, 240
Dumont, 133, 218
Dunne, 23, 24, 66, 108, 140
Dyott, 170
j_^
Eddies, 170
Eiffel, 77, 96, 103
Elastic, 204
Engineering, 77
Engines, 23, 86, 292
E.N.V7., 132
Ettrich, 143
Examples, 325
F
Fales, 77
Farman, 22, 23, 26, 50, 63, 108, 132,
159, 173. 2I9
Ferber, 218, 228, 234
First flights-
See Ader.
Farman.
Langley.
Maxim.
Rozier.
Santos Dumont.
Wright.
Fishes, 80, 89
Flapping wings. See Hargrave.
" Flight," 255
Flights—
,, Britain, 173
„ Channel, 173
,, Manchester, 173
Floats, 156
Flow, 91
Fordyce, 225
Friction, 95
Gap, 106
Gausman, 177
Gerardville, 227
Glaisher, 199
Glazebrook, 246
Gliding, 7, 43, 210
,, Cayley, 194
,, Chanute, 213
,, Control, 122
,, Lilienthal, no, 210
Gliding, Montgomery, 210
,, Ogilvie. 233
,, Pelterie, 226
,, Pilcher, 213
,, Wright, 120
Gnome, 23, 86, 294
Goupy, 158
Grace, 244
Grahame-White, 140, 236, 243
Green, 23, 87
Guns, 8 1
Gusts, 47, 51
H
Hamilton, 170
Hankin, 65, 76
Hanriot, 31, 148
Hargrave, 204
Harper, 53
Helicopter, 84, 191
Hendon, 243
Henson, 196
Herring, 213
History, 174
Holden, 162
Huffaker, 123, 125
Hydro-aeroplanes, 152, 171, 246
Hydrogen, 179
Hydroplanes, 154
Icarus, 174
Interference, 105
Jeffries, 189
Journals, 256
K
Kites, 205
Lagarde, 188
Lana, 176
Lanchester, 12, 76
Langley, 131, 208
La Roche, 235
Latham, 231, 234
Launoy, 191
Leblanc, 241
Le Blon, 235
Le Matin, 241
Lift, 3, 8, 26, 90
,, coefficient, 99, 307, 329
,, dihedral, 105
,, Military Trials, 151
,, rresistance ratio, 90, 97, 125,
200, 307
358
AVIATION
Lift: resistance ratio — flat plate, 97,
307
Lilienthal, 43, 96, 98, 102, 108, no,
121, 124, 172, 211
Loraine, 241
Lunardi, 189
M
Magnetos, 297
Maloney, 210
Manchester, 237
Manoeuvres, 242
Marey, 121
Martin-Handasyde, 18
Maxim, 201
McArdle, 241
McClean, 235
Meteorology, 281
Meurthe, 63, 138, 219
Michelin, 227, 239
Military—
,, Guns, 8 1
,, Manoeuvres, 242
„ R.F.C., 264
„ Trials, 147, 272
Models, 10
Monaco, 158
Montalembert, 188
Montgolfier, 181
Montgomery, 108, 143, 210
Moore-Brabazon, 136, 227, 234, 239
Morane, 240
Motion, 303
Mouillard, 204
N
Newton, 3, 57, 79, 106, 152, 303
Newton's laws, 303
Nieuport, 159
Notes, 287
N.P.L., 93, 96, 98, 99, 101, 105, 106
Numerical examples, 325
Ogilvie, 73, 93, 233, 243
O'Gorman, 246
j.
Page, 27
Parachute, 192
Parke, 167
Patents, 289
Paulhan, 140, 173, 232, 234, 243
Pelterie, 133, 226
Penaud, 204
Petrol, 292
Phillips, 200
Pilcher, 213
Pilot's Notes, 287
Power, 193
Priestley, 181
Prizes, 219, 226
Propellers, 4, 21, 24, 79, 335
,, diam. and speed, 81
,, two, 81
w (v. wing), 6
R
R.AC.C., 234, 246
R.A.F., 22
Radley, 243
Ramus, 155
Rankine, 83
Rayleigh, 5, 246
Records, 226, 235, 262
References, 255
Relative motion, 2
Renault, 23
Resistance —
,, aeroplanes, 320, 329
,, constants, 304
,, fair shapes, 305, 327
,, friction, 309, 325
plates, 305, 326
,, radiators, 306
,, struts, 309
wings, 307
,, wires, 308
Revillon, 185
Reynolds, 166
Reuinert, 239
R.F.C., 245, 264
Robert, 184, 188
Roe, 228, 233
Roebuck, 197
Rolls, 163, 225, 234, 240, 242
Rozier, 185
Ruck, 162
Rudder couple, 334
Seawright, 233
Sheldon, 189
Short, 19, 80, 156, 228
Singer, 236
Soaring, 118
Sommer, 235
Sopwith, 243
Speed, variable, 72> 9°
Spratt, 123, 125
Springs, 334
Squier, 221
Stability, 9, 10, 38
,, compass, 42
damping, 44
,, directional. See Steering.
,, Dunne, 143
INDEX
359
Stability, lateral, 46, 208
longitudinal, 67
negative tips, 55
of cambered wing, 1 1
of flat plate, 10, 51
pitching, 67
platform, 45
sideslip, 50
weathercock, 42, 70, 77
Weiss, 141
yawing, 49
Stalled, 73
Starting-, 153
Stanford, 232
St. Fond, 184
Steering-, 57
a course, 287, 335
balance of power, 59
banking, 58, 336
birds, 65
closed circuit, 62
dirigibles, 13
Dunne, 145
negative tips, 63, 145
Streamlines, 91
Stringfellow, 172, 196
Sykes, 148
Tables, 344
Tails, 16, 35
„ skids, 36
Tangential, 98
Tatin, 204
Terminology, 248
Thornycroft, 155
Tissandier, 227
Triaca, 220
Turnbull, 77
Turner, 199
Tytler, 188
U
Undercarriages, 27
U.S.A. Army, 220, 233
V
Valentine, 245
Vedrines, 173, 245
Vickers, 18
Villette, 186
Vinci, 175
Voisin, 50, 108, 132, 208, 219
,, control, 133
Vol Pique, 331
w
Walker, 192
Warp, 33, 48
,, and yawing, 49
" Waterhen," 157
Weiller, 224
Weiss, 1 08, 140
Wenham, 199
Wilkins, 176
Wind charts, 281
Wing area, 329
analysis, 314
camber, 4, 96
feathers, 75
flaps, 34
joint, 89
pressure distribution, 101, 311
v. propeller. See Propeller.
propulsion, 175, 206
reflexed, 77
structure, 25, 33
top pressure, 75
Wolseley, 87
Wolverhampton, 241
Wright (biplane), 22, 29, 32, 79, 86,
106, 164
(Orville), 5, 50, 63, 73, 108,
120, 137, 173,
213, 2i5
(Wilbur), 5, 50, 63, 108, 120,
137. 173. 213,
215, 223
Wrights-
control, 32
first machine, 130
rail track, 29
patent, 289
research, 120
stalled, 73
Yachts, 4, 44, 47, 70
Yawing, 49
Zahm, 95
Zambeccari, 187
6
360
AVIATION
INDEX TO FIRST REFERENCES
The following index is for
refer in Part I to the first
ascertaining its meaning.
Aerodynamic, 8
Angle, 24
Aspect, 12
,, ratio, 105
Balance of power, 59
Bank, 58
Cdbrd, 73
Cambered wing, 4
C.G. (centre of gravity), 14
C. P. ( ,, pressure), n
Chord, 18
Critical angle, 99
Dihedral, 20, 37
Dive, ii
Elevator, 20
Flaps, 34
Friction, 95
Gap, 106
Gliding, 7
Gust, 46, 54
Helicopter, 84
Interference, 105
Lift, 3, 26
,, coefficient, 99
,, :resistance ratio, 90
the convenience of those who may want to
use of an expression for the purpose of
Monoplane, 17
Negative tips, 55
Pitching, 39
Pressure distribution, 103
Reflexed wing, 77
Relative motion, 2
Rolling, 10
Sideslip, 50
Soaring, 5
Spin, 49
Stability, 10
,, (compass), 42
,, (platform), 45
,, (weathercock), 42
Steering, 56
Tail, 20, 35
Tangential, 98
Top pressure, 75
Undercarriage, 17
Up- wind component, 104
Warp, 33
,, (automatic), 54
Yawing, 39
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