HE NEW ART DF FLYING

UNIVERSITY OF CALIFORNIA LIBRARY

WALDEMAR KAEMPFFERT

LIBRARY

OF THE

UNIVERSITY OF CALIFORNIA.

Class

THE NEW ART OF FLYING

Photograph by Edwin Levick

Fig. 36. — The Hanriot monoplane in flight. The

entire framework is covered with canvas

to reduce resistance

	The New Art of Flying
	BY WALDEMAR KAEMPFFERT With Numerous Illustrations
	vi ,
	>-, >' T* ;\ } , -, } i sTV%? HI £*;i
	NEW YORK DODD, MEAD AND COMPANY 1911

Copyright iplO, BY WALDEMAR KAEMPFFERT

Copyright 1911 BY HARPER & BROS.

Published, April, 1911

LIBRARIAN'S FIK3

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PREFACE

WHEN the time comes for some historian of the far-distant future to survey critically the technical achievements of the nineteenth and twentieth centuries and to weigh the compara- tive economic importance of those achievements, it may be that the invention of the aeroplane flying-machine will be deemed to have been of less material value to the world than the dis- covery of Bessemer and open-hearth steel, or the perfection of the telegraph, or the intro- duction of new and more scientific methods in the management of our great industrial works. To us, however, the conquest of the air, to use a hackneyed phrase, is a technical triumph so dramatic and so amazing that it overshadows in importance every feat that the inventor has accomplished. If we are apt to lose our sense of proportion, it is not only because it was but yesterday that we learned the secret of the bird, but also because we have dreamed of flying long before we succeeded in ploughing the water in a dug-out canoe.

From Icarus to the Wright Brothers is a far cry. In the centuries that have elapsed more

218707

vi PREFACE

lives have been lost in aeronautic experimenta- tion than in devising telephones and telegraphs. These tragedies of science have lent a glamour to the flying-machine; so much so, indeed, that the romance rather than the technique of flying interests the reading public. Yet this attitude of wonder is pardonable. Only a few years ago the inventor of a flying-machine was classed, even by scientists, with the misguided enthusi- ast who spends his life in devising perpetual motion machines or in fruitless attempts at squaring the circle. It is hard to realise that the building of aeroplanes is now elevated to the dignity of a legitimate engineering pursuit.

Although the romantic aspects of aviation have not been ignored in the following pages, it is the chief purpose of this book to explain as simply and accurately as possible the principles of dynamic flight and aeroplane construction, so that an intelligent reader will learn why a machine many times heavier than the air stays aloft for hours at a time and why it is con- structed as it is. The limitations imposed by a popular book are such that it is impossible to discuss with anything like thoroughness such difficult matters as equilibrium and stability, the correct proportioning of supporting surfaces to weight and speed, and the resistance encoun-

PREFACE vii

tered in the air by planes in motion. Indeed, these questions are not definitely settled in the minds of technical men. Besides presenting an elementary account of a flying-machine's way in the air, it has been deemed advisable to dis- cuss the screw and the internal-combustion motor as applied to the flying-machine. There can be little doubt that the propeller and the engine offer many a problem for solution be- fore the aeroplane can compete successfully with other forms of locomotion, and a discussion of the driving mechanism of an aeroplane should, therefore, constitute an essential part of even a popular book on flying.

So marked have been the changes that have been made in the construction of well-known biplanes and monoplanes and so many are the new machines that appear almost from week to week that it is almost a hopeless task to present anything like a complete account of existing aeroplanes. Hence it has been deemed advisable to limit the descriptions of types to those machines which have been in a measure standardized.

In the preparation of this volume the author has been ably assisted by several friends to whom he wishes to make due acknowledgment. He is indebted to Mr. Carl Dienstbach for a

viii PREFACE

critical reading of the entire manuscript before it passed to the press, and for many valuable suggestions; to Mr. C. Fitzhugh Talman, li- brarian of the United States Weather Bureau, for a painstaking revision of the chapter en- titled " The New Science of the Air "; to Mr. H. A. Toulmin for information on the points at issue in the various suits brought by the Wright Brothers for the alleged infringement of their patents; to Francis W. Aymar, Pro- fessor of Law in the New York University Law School, for valuable aid in the prepara- tion of the chapter on " The Law of the Air " ; and to the Smithsonian Institution and the Wright Brothers for various photographs.

Acknowledgment is also made to Messrs. Harper & Brothers for permission to use ma- terial which appeared in an article written by the author and published in " Harper's Monthly Magazine."

NEW YORK, N. Y., January, 1911.

CONTENTS

CHAPTER PAGI

I WHY FLYING-MACHINES FLY .... i

II FLYING-MACHINE TYPES 15

III THE PLANE IN THE AIR 26

IV STARTING AND ALIGHTING 42

V How AN AEROPLANE is BALANCED . 58

VI MAKING A TURN 85

VII THE PROPELLER 94

VIII AEROPLANE MOTORS in

IX THE NEW SCIENCE OF THE AIR . . 133

X THE PERILS OF FLYING 163

XI THE FLYING-MACHINE IN WAR . . . 185

XII SOME TYPICAL BIPLANES 208

XIII SOME TYPICAL MONOPLANES .... 222

XIV THE FLYING-MACHINE OF THE FUTURE 23 1 XV THE LAW OF THE AIR 246

GLOSSARY 269

INDEX fc . . 281

ILLUSTRATIONS

Fig. 36. — The Hanriot monoplane in flight. The entire frame- work is covered with canvas to reduce resistance frontispiece

FACING PAGE

Fig. i . — Lilienthal gliding in the machine in which he was killed 4 Fig. a. — Chanute trussed biplane glider in flight 8

fig. 3. — Langley's steam-driven model, the first motor flying- machine that ever flew ia

Fig. 4. — Langley's aerodrome in flight on May 6, 1X96, on the Potomac River at Quantico. This is the first photo- graph ever made of an aeroplane in flight .... 1 6

Fig. 5. — Roe's triplane in flight. The best engineering opinion is against the triplane because of its large head resist- ance and consequent low speed 20

Fig. 6. — Cornu's helicopter or screw-flyer. In this machine the lifting and propulsive force is obtained entirely by screws »4

Fig. IO. — Langley's device for launching his aerodromes. The machine was mounted on a houseboat, which could be turned in any direction so as to face the wind ... 30

Fig. 1 1 . — Langley's model aerodrome photographed immediately

after a launch . . % 34

Fig. 13. — Starting derrick and rail of the Wright Brothers. The

machine is about to be hauled up on the rails ... 38

Fig. 14. — Combined wheels and skids employed on the later Wright

machines 44

Fig. 15. — Bleriot starting from the French coast on his historic

flight across the English Channel 48

Fig. ao. — Mr. Wilbur Wright in the old type Wright biplane . 54

Fig. ai. — The first type of Wright biplane, showing the general dis- position of the main planes, forward horizontal rudders and rear vertical rudders 60

Fig. aa. — A machine devised by the Wrights for the instruction of

pupils 7*

Fig. 24. — Glenn H. Curtiss winning the Scientific American Trophy

on July 4, 1908 76

Fig. 25. — Glenn H. Curtiss in one of his flying-machines, equipped

with balancing-planes between the main planes . . 80

Fig. 27. — The Farman biplane. The ailerons are the flaps on the planes, which, as shown in this picture, hang down almost vertically when the machine is at rest ... 8z

xi

ILLUSTRATIONS

FACING PAGE

Fig. 28. — Henry Farman seated in his biplane. His hand grasps

the lever by which the ailerons are operated ... 88

Fig. 29. — One of the new Curtiss biplanes in flight. The ma- chine is fitted with ailerons similar to those of the Farman machine pictured in Fig. 27 92

Fig. 32. — In the Antoinette monoplane the horizontal or elevating rudder is operated by means of a vertical hand-wheel by the pilot's right hand. The aviator here pictured is Hubert Latham . o,g

Fig- 33- — The Antoinette monoplane of 1909 in which ailerons

were employed to control the machine laterally . . 102

Fig. 34. — Voisin machine of 1909. Machines such as this are

no longer made 106

Fig- 35- — The Voisin biplane of 1910. The old cellular con- struction is abandoned. Instead of vertical curtains between the main planes Farman ailerons are adopted 112

Fig. 37. — Gyrostat mounted in an aeroplane according to the system of A. J. Roberts. The gyrostat is controlled by a pendulum which swings to the right or to the left, according to the tilt of the aeroplane . . . . 1 1 6

Fig. 38. — The new Wright biplane in which horizontal or elevat- ing rudder is mounted in the rear 128

Fig. 40. — A Farman biplane making a turn. The entire machine is canted so that its weight is opposed to the centrif- ugal force generated by rounding an arc at high speed 130

Fig. 43. — A Wright propeller. Wright propellers turn at com- paratively low speeds (400 revolutions a minute). They have an estimated efficiency of 76 per cent . 136

Fig. 44. — The Wright machine is driven by two propellers driven in opposite directions by chains connecting the pro- peller shafts with the motor shaft 140

Fig. 45. — The Santos-Dumont "Demoiselle" monoplane is the smallest flying-machine that has ever flown success- fully with a man. In the later "Demoiselles" fabric propellers are supplanted by wooden screws of the usual type 144

Fig. 46. — A Bleriot monoplane showing a seven-cylinder, fifty- horse power rotary Gnome motor. The motor spins around with the propeller at the rate of about 1400 revolutions a minute 148

Fig. 47. — The motor and the propeller of a R. E. P. (Robert Esnault-Pelterie) monoplane. Robert Esnault-Pel- terie has abandoned this four-bladed metal propeller for the more efficient two-bladed wooden propeller . 152

Fig. 48. — Henry Farman seated in his biplane with three passengers 156

xii

ILLUSTRATIONS

FACING PAGE

Fig. 63. — Motor of the Wright biplane 1 60

Fig. 64. — Two-cylinder Anzani motor on a Letourd-Niepce mono- plane 1 66

Fig. 65. — The kite and the balloon-house of the Mt. Weather

Observatory 17°

Fig. 66. — Sending up the first of a pair of tandem kites at the Blue

Hill Observatory 174

Fig. 67. — Mechanism of a meteorograph which records the velocity of the wind, the temperature, the humidity, and the barometric pressure 178

Fig. 69. — A glimpse through a Wright biplane. The two planes are trussed together like the corresponding members of a bridge, so as to obtain great strength . . . . 182

Fig. 70. — One of the numerous accidents that happened to Louis

, Bleriot before he devised his present monoplane . . 1 88

Fig. 71. — A biplane that came to grief because of defective lateral

control IQ2

Fig. 72. — An old style Voisin biplane of cellular construction wrecked because the pilot tried to make too short a turn near the ground 196

Fig. 73- — A Krupp 6.5 cm. gun for airship and aeroplane attack. The gun fires a projectile weighing about 8 Ibs. 1 3 oz. to a height of about 18,700 feet 200

Fig. 74. — A Krupp 7. 5 cm. gun mounted on an automobile truck. The gun fires a 12 Ib. 2 oz. projectile to a height of about 4 miles. The automobile has a speed of 28^ miles an hour. Under its seats 62 projectiles can be stored 104

Fig. 75. — A Krupp 10.5 cm. naval gun for repelling aircraft . . 210

Fig. 76. — The projectiles employed for the repulsion of airships and aeroplanes leave a trail of smoke behind them so that the gun crew can determine the amount of error in sighting 214

Fig. 77. — A projectile that hit its mark 216

Fig. 78. ' — A Voisin biplane equipped with a Hotchkiss machine gun, exhibited at the 1910 Salon de 1'Aeronautique, Paris. This is probably the first attempt to mount a machine gun on an aeroplane, and was a rather poor attempt 2*O

Fig. 79. — The Wright biplane that Wilbur Wright flew in France

in 1908 224

Fig. 80. — The Wright biplane of 1910. The elevating rudder has been placed in the rear of the machine, where it also serves as a tail 228

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ILLUSTRATIONS

_. FACING PAGE

rig. si. — The machine in the air is a Farman biplane of the latest type. The machine on the ground is a Bleriot monoplane 232

Fig. 82. — Sommer biplane 236

Fig. 83. — The 100 horsepower Antoinette monoplane that Hubert Latham flew at Belmont Park during the Interna- tional Aviation Tournament of 1910 240

Fig. 84. — The Santos-Dumont " Demoiselle " in flight . . . 150

Fig. 85. — A Bleriot racing monoplane. Six men are exerting

every muscle to hold back the machine . . . . 256

Fig. 86. — The Bleriot monoplane XII. This is a passenger- carrying type. The pilot and his companion sit side by side below the wings „ 262

XIV

DIAGRAMS

PAGE

Fig. 7. — CD is the " entering edge." The lifting power of the forward half A of the curved plane is greater than the lifting power of the rear half 2?, although both are of equal area 28

Fig. 8. — A is a simple inclined plane j S, a curved plane at the same angle of incidence or inclination ; C, the type of curved plane which has thus far given the best results in the air 29

Fig- 9 . — The plane B S is at a greater angle of incidence than the plane A A. If its speed be 10 miles an hour, it will, while travelling horizontally 25 feet, overcome its tendency to fall to D. If its speed be 20 miles an hour, it will have 50 feet to travel while over- coming its tendency to fall to E. Unless the angle of B S, therefore, were decreased to that of A A for the greater speed, the plane would not move hori- zontally but would ascend 32

Fig. 12. — The special launching device invented by the Wright Brothers. The device consists of an inclined rail, about seventy feet long ; a pyramidal derrick j a heavy weight arranged to drop within the derrick ; and a rope, which is fastened to the weight, passed around a pulley at the top of the derrick, then around a second pulley at the bottom of the derrick over a third pulley at the end of the rail, and finally fastened to a car running on the rail. The car is placed on the rail, and the aeroplane on the car. When a trigger is pulled, the weight falls, and the car is jerked forward. So great is the preliminary velocity thus imparted that the machine is able to rise in a few seconds from the car, which is left behind 52

Fig. 1 6. — Path of an aeroplane driven forward but with a speed too

low for horizontal flight, and with too flat an angle . 58

Fig. 17 — Path of a plane inclined at the angle C to the horizontal. The arrow A indicates the direction of travel. If the speed is sufficient the plane will rise because of the upward inclination of the plane 59

Fig. 18. — How a plane is laterally balanced by means of ailerons and a vertical rudder. — The plane A is provided with hinged tips C and D and with a vertical rudder E. The tips are swung in opposite directions to correct any tipping of the plane, and the vertical rudder E is

XV

DIAGRAMS

PACK

swung over to the side of least resistance (the side of the tip D in the example here given) in order to prevent the entire machine from rotating on a vertical axis . 62 Fig. 19. — The system of control on an old Wright model ... 64

Fig. 13. — The Curtiss system of control 66

Fig. 26. — The system of ailerons and rudders devised by Henry Farman for maintaining fore-and-aft and side-to-side balance 68

Fig. 30. — The Bleriot system of control 70

Fig. 31. — The steering and control column of the Bleriot mono- plane. The wheel Z,, the post AT, and the bell-shaped member M form one piece and move together. Wires 0 connect the bell with the yoke G, carrying the pulley F, around which the wires H running to the flexible portions of the supporting planes are wrapped. By rocking the post and bell from side to side in a vertical plane the wires H are respectively pulled and relaxed to warp the planes. By moving the post K back and forth the horizontal rudder is operated through the wires P. These various movements of the post can be effected by means of the wheel L, which is clutched by the aviator's hands, or by means of the bell My which can be clutched by the aviator's feet if necessary 71

Fig. 39. — An aeroplane of 40 feet spread of wing rounding an arc of 60 feet radius. Since the outer side of the aeroplane must travel over a given distance in the same time that the inner side must travel a considerably shorter distance, gravitation must be opposed to centrifugal force in order that the turn may be effected with safety . . 86

Fig. 41. — A single-threaded and a double- threaded screw. A two- bladed aeroplane propeller may be conceived to have been cut from a double-threaded screw, /. «., the sec- tions AznA A' and the sections B and B' ... 97

Fig. 42. — How the Wright propeller is cut from three planks laid

upon one another fan-wise 109

Figs. 49, 50, 51, and 52. — The four periods of a four-cycle engine. During the first period (Fig. 49) the explosive mix- ture is drawn in ; during the second period (Fig. 50) the explosive mixture is compressed j during the third period (Fig. 51) the mixture is exploded ; and during the fourth period the products of combustion are discharged 114

FiS* 53 • — The U8ual arrangement of the four cylinders of a four- cylinder engine .......... .118

xvi

DIAGRAMS

PAGE

Figs, 54 and 55. — Side and plan views of a four-cylinder engine

with diagonally-placed cylinders 120

Figs. 56 and 57. — Engine with horizontally opposed cylinders . . 1 21

Figs. 58 and 59. — Engine with four cylinders radially arranged . 123

Fig. 60. — Arrangement of connecting-rods of an engine with four

radial cylinders ..124

Fig. 6 1 — Arrangement of cylinders and crank case of one type of

three-cylinder engine ....125

Fig. 62. — Disposition of cylinders, crank case and connecting-rods

in one type of engine 126

Fig. 68. — The extent of the atmosphere in a vertical direction.

Heights in kilometres ..••••••.147

XV11

THE

NEW ART OF FLYING CHAPTER I

WHY FLYING-MACHINES FLY

AN aeroplane is any flat or slightly curved sur- face propelled through the air. Since it is con- siderably heavier than air, an inquiring mind may well ask: Why does it stay aloft? Why does it not fall?

It is the air pressure beneath the plane and the motion of the plane that keep it up. A balloon can remain stationary over a given spot in a calm, but an aeroplane must constantly move if it is to remain in the air. The mono- planes and biplanes of Bleriot, Curtiss, and the Wrights are somewhat in the position of a skater on thin ice. The skater must move fast enough to reach a new section of ice before he falls; the aeroplane must move fast enough to reach a new section of air before it falls. Hence, the aeroplane is constantly struggling with gravitation.

2 THE NEW ART OF FLYING

The simplest and most familiar example of an aeroplane is the kite of our boyhood days. We all remember how we kept it aloft by hold- ing it against the wind or by running with it if there happened to be only a gentle breeze. When the wind stopped altogether or the string broke, the kite fell. Above all things it was necessary to hold the kite's surface toward the wind, — an end which we accomplished with a string.

The eagle is an animated kite without a string ; it keeps its outspread wings to the wind by muscular power. If we can find a substitute for the string, some device in other words which will enable us to hold the kite in the proper direction, we have invented a flying-machine. The pull or the thrust of an engine-driven pro- peller is the accepted substitute for the string of a kite and the muscles of an eagle.

If only these simple principles were involved in a solution of the age-old problem of artificial flight, aeroplanes would have skimmed the air decades ago. Many other things must be considered besides mere propelling machinery. Chief among these is the very difficult art of

WHY FLYING-MACHINES FLY 3

balancing the plane so that it will glide on an even keel. Even birds find it hard to maintain their balance. In the constant effort to steady himself a hawk sways from side to side as he soars, like an acrobat on a tight rope. Occa- sionally a bird will catch the wind on the top of his wing, with the result that he will capsize and fall some distance before he can recover himself. If the living aeroplanes of nature find the feat of balancing so difficult, is it any wonder that men have been killed in endeavouring to dis- cover their secret?

If you have ever watched a sailing yacht in a stiff breeze you will readily understand what this task of balancing an aeroplane really means, although the two cases are mechani- cally not quite parallel. As the pressure of the wind on the sail heels the boat over, the ballast and the crew must be shifted so that their weight will counterbalance the wind pressure. Otherwise the yacht will capsize. In a yacht maintenance of equilibrium is comparatively easy; in an aeroplane it demands incessant vigilance, because the sudden slight variations of the wind must be immediately met. The

4 THE NEW ART OF FLYING

aeroplane has weight; that is, it is always fall- ing. It is kept aloft because the upward air pressure is greater than the falling force. The weight or falling tendency is theoretically con- centrated in a point known as the centre of gravity. Opposed to this gravitative tendency is the upward pressure of the air against the under surface of the plane, which effect is theoretically concentrated in a point known as the centre of air pressure. Gravitation (weight) is constant; the air pressure, because of the many puffs and gusts of which even a zephyr is composed, is decidedly inconstant. Hence, while the centre of gravity remains in approximately the same place, the centre of air pressure is as restless as a drop of quick- silver on an unsteady glass plate.

The whole art of maintaining the side-to- side balance of an aeroplane consists in keeping the centre of gravity and the centre of air pressure on the same vertical line. If the centre of air pressure should wander too far away from that line of coincidence, the aero- plane is capsized. The upward air pressure being greater than the falling tendency and

WHY FLYING-MACHINES FLY 5

having been all thrown to one side, the aero- plane is naturally upset.

Obviously there are two ways of maintain- ing side-to-side balance, — the one by con- stantly shifting the centre of gravity into coin- cidence with the errant centre of air pressure; the other by constantly shifting the centre of air pressure into coincidence with the centre of gravity.

The first method (that of bringing the centre of gravity into alignment with the centre of air pressure) involves ceaseless, flash-like move- ments on the part of the aviator; for by shift- ing his body he shifts the centre of gravity. It happened that one of the first modern experi- menters with the aeroplane met a tragic death after he had succeeded in making over two thousand short flights in a gliding-machine of his own invention, simply because he was not quick enough in so throwing his weight that the centres of air pressure and gravity coin- cided. He was an engineer named Otto Lilien- thal, and he was killed in 1896. Birds were to him the possessors of a secret which he felt that scientific study could reveal. Accordingly,

6 THE NEW ART OF FLYING

he spent many of his days in the obscure little hamlet of Rhinow, Prussia. The cottage roofs of that hamlet were the nesting places of a colony of storks. He studied the birds as if they were living machines. After some practical tests, he invented a bat-like appa- ratus composed of a pair of fixed, arched wings and a tail-like rudder. Clutching the horizontal bar to which the wings were fast- ened, he would run down a hill against the wind and launch himself by leaping a few feet into the air. In this manner he could finally soar for about six hundred feet, upheld merely by the pressure of the air beneath the outstretched wings. In order to balance himself he was com- pelled to shift his weight incessantly so that the centre of gravity coincided with the centre of air pressure. Since they rarely remain coin- cident for more than a second, Lilienthal had to exercise considerable agility to keep his centre of gravity pursuing the centre of air pressure, which accounts for the apparently crazy antics he used to perform in flights. One day he was not quick enough. His machine was capsized, and his neck was broken. Pil-

WHY FLYING-MACHINES FLY 7

cher, an Englishman, slightly improved on Lili- enthal's apparatus, and after several hundred flights came to a similar violent end. Crude as Lilienthal's machine undoubtedly was, it startled the world when its first flights were made. It taught the scientific investigator of the problem much that he had never even suspected, and laid the foundation for later researches.

Octave Chanute, a French engineer resident in the United States, continued the work of the ill-fated Lilienthal. Realising the inherent danger of a glider in which the operator must adapt himself to the changing centre of air pressure with lightning-like rapidity, he devised an apparatus in which the centre of air pressure was made to return into coincidence with the centre of gravity, — the second of the two ways of maintaining side-to-side balance. Thus Chanute partly removed the perilous necessity of indulging in aerial gymnastics. In his glid- ing-machines the tips of the planes, when struck by a gust of wind, would fold slightly backward, thereby curtailing the tendency of the centre of air pressure to shift.

8 THE NEW ART OF FLYING

Chanute built six motorless, man-carrying gliders, with three of which several thousand short flights were successfully undertaken. The best results were obtained with an apparatus consisting of two superposed planes, a construc- tion which had been previously adopted by Lilienthal. It remained for the Wright Brothers to provide a more perfect mechanism for controlling the movement of the centre of air pressure.

The principle of sitting or lying still in the aeroplane and, by means of mechanical devices, bringing the centre of air pressure back into alignment with the centre of gravity is now fol- lowed by every designer of aeroplanes. The old, dangerous method of shifting weights is quite abandoned. The greatest contribution made by the Wright Brothers to the art of fly- ing was that of providing a trustworthy mech- anism for causing the centre of air pressure to return into coincidence with the centre of gravity.

The aeroplane must be balanced not only from side-to-side but fore-and-aft as well. The same necessity exists in the eld-fashioned,

WHY FLYING-MACHINES FLY 9

single-surface kite. To give it the necessary fore-and-aft stability, we used to adorn it with a long tail of knotted strips of rags. If the tail was not heavy/ or long enough, the kite dived erratically and sometimes met its destruction by colliding with a tree. To insure longitud- inal stability, many aeroplane flying-machines are similarly provided with a tail, which con- sists generally of one or more horizontal plane surfaces. Some aeroplanes, however, are tail- less, among them the earlier Wright machines. Usually, they are less stable than the tailed variety.

In order to relieve the .aviator of the neces- sity of more or less incessantly manipulating levers, which control centres of air pressure, many inventors have tried to provide aero- planes with devices which will perform that task automatically. Some of them are ingen- ious; but most of them are impracticable be- cause they are too heavy, too complicated, or not responsive enough.

In order to fly, an aeroplane, like a kite or a soaring bird, is made to rise preferably in the very teeth of the wind. What is more, it

io THE NEW ART OF FLYING

must be in motion before it can fly. How this preliminary motion was to be obtained long baffled the flying-machine inventor. Eagles, vultures, and other soaring birds launch them- selves either by leaping from the limb of a tree or the edge of a cliff, or by running along the ground with wings outspread, until they have acquired sufficient speed. To illustrate the difficulty that even practised soaring birds find in rising from the ground, the late Prof. Samuel P. Langley used to quote the following graphic description of the commencement of an eagle's flight (the writer, one of the founder members of the old aeronautical society of Great Britain, was in Egypt, and the " sandy soil " was that of the banks of the Nile) :

" An approach to within 80 yards arouses the king of birds from his apathy. He partly opens his enormous wings, but stirs not yet from his station. On gaining a few feet more he begins to walk away with half- expanded, but motionless, wings. Now for the chance. Fire ! A charge of No. 3 from eleven bore rattles audibly but ineffectively upon his

WHY FLYING-MACHINES FLY n

densely feathered body; his walk increases to a run, he gathers speed with his slowly wav- ing wings, and eventually leaves the ground. Rising at a gradual inclination, he mounts aloft and sails majestically away to his place of refuge in the Libyan range, distant at least five miles from where he rose. Some frag- ments of feathers denote the spot where the shot has struck him. The marks of his claws were traceable in the sandy soil, as, at first with firm and decided digs, he forced his way; but as he lightened his body and increased his speed with the aid of his wings, the imprints of his talons gradually merged into long scratches. The measured distance from the point where these vanished to the place where he had stood proved that with all the stimulus that the shot must have given to his exertions he had been compelled to run full 20 yards before he could raise himself from the earth."

We have not all had a chance of seeing this striking illustration of the necessity of get- ting up speed before soaring, but many of us have disturbed wild ducks on the water

12 THE NEW ART OF FLYING

and noticed them run along it, flapping their wings for some distance to get velocity before they could fly, and the necessity of initial velocity is at least as great with an artificial flying-machine as it is with a bird. From this, we can readily understand why a vulture can be confined in a small cage, which is entirely open at the top.

To get up preliminary speed many methods have been adopted. Langley tried every con- ceivable way of starting his small model, and at last hit on the idea of launching it from ways, somewhat as a ship is launched into the water. The model rested on a car which fell down at the extremity of its motion and thus released the model for its free flight. On May 6, 1896, he saw his creation really fly like a living thing, the first time in history that a motor-driven aeroplane ever flew.

The Wright Brothers used to obtain their preliminary speed by having their machine carried down the side of a sandhill, partly sup- ported by a head-wind. Their first perfected motor-driven, man-carrying biplane was started on an inclined track. Most aviators of the

O (D

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1 S 1

bfl

j

WHY FLYING-MACHINES FLY 13

present time, however, mount their aeroplanes on pneumatic-tired wheels, and like the eagle, in the foregoing quotation, run along the ground for a short distance. Aeroplanes have also been dropped into the air from balloons.

Just as a soaring bird uses his legs in leap- ing into the air or running on the ground to start his flight and also in alighting, so many aeroplanes alight with the wheels that serve them during the brief moments of launching. Sometimes, however, special alighting devices are provided, a conspicuous example of which is to be found in the skids or runners of the Wright machine.

The problem of steering an aeroplane, when it is launched, is solved, as it must be, by two sets of rudders. A steamboat is a vehicle that travels in two dimensions only; hence, it re- quires only a single, vertical rudder, which serves to guide it from side to side. An aero- plane moves not only from side to side, but up and down as well. Hence, it is equipped with a vertical rudder similar to that of a steamboat's, and also with a horizontal rudder, which serves to alter its course up or down,

14 THE NEW ART OF FLYING

and which is becoming more widely known as an elevator. Fore-and-aft stability is attained in tailless machines entirely by manipulation of this elevator. Even in tailed machines its use for that purpose is quite imperative.

CHAPTER II

FLYING-MACHINE TYPES

THE flying creatures of nature — insects, birds, fishes, and bats — spread wings that lie in a single plane. Because their wings are thus disposed birds may be properly regarded as single-decked flying-machines or " monoplanes," in aviation parlance, and because the earliest attempts at flying were more or less slavish imi- tations of bird-flight, it was but natural that the monoplane was man's first conception of a flying-machine. Since birds are the most effi- cient flying-machines known, so far as power consumption for distance travelled and surface supported are concerned, the monoplane will probably always be regarded as the ideal type of aeroplane flying-machine.

It is a circumstance of considerable scientific moment that the wings of a gliding bird, such as an eagle, a buzzard, or a vulture, are wide in spread and narrow in width. Much pains- taking experimentation by Langley and others

1 6 THE NEW ART OF FLYING

has shown that the best shape of plane is that which is oblong; the span must be considerably greater than the width. In other words, science has experimentally approved the design of a bird's wings. In nature the proportion of span to width varies in different birds. The spread of an albatross' wings is fourteen times the width; the spread of a lark's wings is four times the width, which is the smallest ratio to be found among birds. The albatross is a more efficient flying-machine than the lark. Hence the albatross is a better model to follow and four- teen to one a better ratio than four to one.

Long spans are unwieldy, often too unwieldy for practical, artificial flight. Suppose we cut a long plane in half and mount one half over the other. The result is a two-decked machine, a " biplane." Such a biplane has somewhat less lifting power than the original monoplane, and yet it has the same amount of entering edge. Moreover, the biplane is a little steadier in the air than the monoplane and therefore a little safer, just as a box-kite is steadier than the old-fashioned single-surface kite. Still, the difference in stability between biplane and

From an instantaneous photograph by Dr. Alexander Graham Bell

Fig. 4. — Langley's aerodrome in flight on May 6,

1896, on the Potomac River at Quantico.

This is the first photograph ever made

of an aeroplane in flight

FLYING-MACHINE TYPES 17

monoplane is so slight that designers base their preferences for one type or the other on other considerations. Both types are inher- ently so unstable that it requires a skilled hand to correct their capsizing tendencies.

By placing one plane over another certain structural advantages are obtained. It is com- paratively easy to tie two superposed planes together and to form a strong, bridge-like truss, which was first done by Chanute. The proper support of the outstretched surfaces of a mono- plane, on the other hand, is a matter of some difficulty.

To correct the inherent instability of both monoplanes and biplanes and to make them safer machines, tails are frequently added. Stability and safety are thus gained at the expense of driving power; for the increased surface of the tail means more resisting sur- face and therefore less speed. An engine of twenty horse-power will drive a tailless Wright machine; tailed Voisin machines with large, heavy cellular tails have refused to rise at times even when equipped with fifty horse- power motors.

1 8 THE NEW ART OF FLYING

If a monoplane were to fall vertically like a parachute, it would offer the resistance of its entire surface to the fall; if a biplane were to fall, it would offer the resistance of only one of its planes to the fall. Hence the monoplane is a better parachute than the biplane. The point is perhaps of slight value, because if a skilful aviator is high enough when his motor fails him, he can always glide to the ground on a slant which may be miles in length. Para- doxical as it may seem, the greater the distance through which he may fall, the better are an aviator's chances of reaching the ground with an unbroken neck. At a slight elevation from the ground, both monoplanes and biplanes are in a precarious position in case of motor stop- pages. There is no distance to glide. Hence they must fall.

Whether the biplane is a better type of ma- chine than the monoplane, it would be difficult, if not impossible, to maintain. It is certain, however, that the biplane has been brought to a higher state of perfection than the mono- plane, probably because it was the first success- ful type of a man-carrying, motor-driven flying-

FLYING-MACHINE TYPES 19

machine. The older the type, the more marked will be the improvements to which it will be subjected. It is curious, too, that most of the pioneer aviators have been advocates of the biplane type. Lilienthal met his death in a biplane. Chanute, who brilliantly continued Lilienthal's work, and the Wright Brothers brought the motorless biplane glider to its highest pitch of perfection. The first flight ever made by a man-carrying, motor-driven machine was that of a Wright biplane. Voisin, Curtiss, and Farman, all of them experienced designers, have performed their most brilliant feats in designing or flying biplanes.

Chanute made many experiments with glid- ing-machines having more than two superposed surfaces; but he found in the end that the bi- plane type was most satisfactory. Despite the lessons to be learned from his painstaking ex- periments, inventors have not been wanting who have worked on the three-deck or triplane principle. One of these is Farman, who de- signed the Farman-Voisin three-decked ma- chine. Others are A. V. Roe in England and Vanniman in France. Vanniman and Farman

20 THE NEW ART OF FLYING

have since abandoned their triplane structures, and thus rather confirmed Chanute's conclu- sions. It is interesting to know that the tri- plane goes back as far as 1868, in which year an inventor named Stringfellow built a three- decked model.

The many-planed flying-machine was prob- ably carried to its extreme by an Englishman, Mr. Horatio Phillips. Between 1881 and 1894 he made a series of experiments which resulted in his building a multiplane, not un- like a Venetian blind in appearance. It con- sisted primarily of a series of numerous super- posed slats, which had extraordinary lifting power. Perhaps the chief objections to such a multiplane are its weight and its height. Con- sequently it is less stable in the air than biplanes.

Since an aeroplane, whether it be of single- deck or double-deck construction, must be driven at considerable speed to keep it in the air, and must, furthermore, get up a certain preliminary speed before it can fly at all, some inventors have thought of rotating the planes, as if they were huge propellers, instead of driv- ing them along in a straight line. Such screw-

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propellers, to push a machine from the ground, are mounted on a vertical shaft, the whole con- stituting a machine which goes by the name " helicopter." A helicopter should theoretically screw its way up into the air. Because no screw- propeller can possibly support a weight in air with anything like the aeroplane's economy of power, the helicopter has never been a practical success. In a helicopter, the screw-propeller must be designed not only for propulsion but for support as well. As far back as 1812 Pon- ton d'Amecourt and de la Landelle maintained that the heavier-than-air machine would be sup- ported by a screw, — the " sacred screw," to use d'Amecourt's ecstatic Gallic phrase. They found in the Academician Babinet a stout sup- porter of their view, and he it was who invented the term " helicoptere." The familiar little screw-fliers which are whirled into the air by hand or by twisted rubber bands seemed to offer experimental evidence enough in support of any helicopter theories. It was recognised, how- ever, that one screw would cause the entire apparatus to rotate. Hence two screws turning in opposite directions were early recommended.

22 THE NEW ART OF FLYING

Thus the rotating effect of one screw was coun- teracted by the other, and the lifting effects of the two were combined.

The most earnest student of the problem of the lifting screw-flier or helicopter has been Colonel Renard, of the French Army. It was he who first pointed out in 1903 that the ordi- nary screw would not answer. A helicopter's screw must not only propel, but must also sup- port, for which reason it must be differently constructed from a screw designed for propul- sion only. Renard even went so far as to plan a composite machine, an apparatus which was a helicopter for lifting itself from the ground and an aeroplane in the air. Thus he hoped to overcome the necessity of that preliminary run which aeroplanes must make in order that they may be launched in the air. His ma- chine would theoretically leap straight up from the ground.

The pathway of aeronautic invention is strewn with wrecked helicopters. Men just as distinguished as Renard have pinned their faith to the blades of its revolving screws. Among them have been Thomas A. Edison

FLYING-MACHINE TYPES 23

and Emil Berliner. Yet the only perfectly operative screw-flier constructed on the lifting- screw principle is the little toy to which ref- erence has been made. In France, where fashions in aeroplanes are created with the same facility as fashions in clothes, the heli- copter still engages the attention of a few en- thusiasts, despite the brilliant success of the aeroplane. Cornu is one of these. His ma- chine undoubtedly lifts; but thus far it has not been allowed to display its capabilities in that direction more than two feet from the ground. Breguet, the inventor of a helicopter aeroplane, is said to have flown in 1908 a dis- tance of sixty-four feet at a height of fifteen feet. He is now building aeroplanes.

Even less encouraging than these experi- ments with helicopters, have been the efforts of a few misguided aviators who have sought to build what are known as ornithopters — machines that flap wings like a sparrow. It seems very natural to adopt the flapping-wing principle, because all birds depend upon it to a certain extent. Apart from the myth of Daedalus the earliest recorded proposal of

24 THE NEW ART OF FLYING

this kind was made in 1500, by Leonardo da Vinci, but he does not seem to have made a practical test. The first actual experiment with flapping wings, according to tradition, seems to have been made by a French tight- rope dancer named A'llard, in the reign of Louis XIV. Allard attempted a demonstra- tion before the court but failed in his strength, fell, and was seriously hurt. Since that time many aviators in ornithopters have broken their wings and sometimes their bones. The most earnest experimenter was Hargrave, who ultimately gave the world the box-kite, the pro- totype of the biplane. He built eighteen flap- ping-wing models between 1883 and 1893. With one of these at least, a flight of three hundred and forty-three feet was made in 1891. It must be said that Hargrave relied on flapping wings solely for propulsion and not for support. His efforts to devise an efficient sustaining surface gave us his box- kite. Only a few French inventors still per- sist in working on the ornithopter principle. The most persistent of these is Adh. de la Hault. His machine, exhibited at Brussels in

FLYING-MACHINE TYPES 25

1908, has wings that describe, when in motion, a figure-of-eight curve. His results have been meagre.

In order to build a flying-machine with flap- ping wings, so as to imitate birds exactly, a very complicated system of levers, cams, cranks, and links must be employed, all of which usually weigh more than the wings can lift.

CHAPTER III

THE PLANE IN THE AIR

A ROWBOAT, a mud-scow, a battleship, and a racing yacht, whatever aesthetic differences they may present, are roughly similar in form. The swifter the vessel the finer will be the lines of its hull. Naval architects after some centuries of experimenting have laid down certain rules of construction to be followed in building ves- sels of a certain class.

The plane surface is to the aeroplane what a hull is to a ship. Like a ship's hull it must be fashioned to cleave the medium through which it must travel with the least possible resistance. Aeronautical engineers have not solved that problem entirely as yet, for the simple reason that flying has only recently be- come an assured fact. But their experiments have given them certain standards which they invariably follow when they design an aero- plane. Young as the art of flying is, it may well be questioned whether the aeronautical en-

THE PLANE IN THE AIR 27

gineer is not in possession of a set of empirical formulae almost as good as those of the naval architect.

.So far as the manner of cleaving their re- spective media is concerned, there is this im- portant difference between ships and planes : — A vessel is propelled through the water along the line of least resistance, the line of its length; an aeroplane, whether it be a bird or a Wright biplane, is driven through the air at right angles to the line of greatest length or resistance.

What is known as the " entering edge " of an aeroplane, in other words the character of the cutting part of a plane, gives the aero- nautical engineer much concern. It is the enter- ing edge that strikes the air first. The lifting- power of a plane gradually dwindles from the entering edge backward. A plane one hundred feet long and one foot wide has greater lifting power than a plane ten feet square, although both planes have exactly the same amount of surface. That explains why the wings of a bird are longer in span than in width, and why the aeroplanes of man are as long and as nar-

28 THE NEW ART OF FLYING

row as possible. If the entire surface of a plane were struck by the air, it would be just as ad- vantageous to employ square planes. But since the air bears directly only on the front or enter- ing edge, we must adopt planes that give us

FIG. 7. — CD is the " entering edge." The lifting power of the forward half A of the curved plane is greater than the lifting power of the rear half B, although both are of equal area.

as great an entering edge as possible without making the plane too unwieldy.

Otto Lilienthal demonstrated, after much experiment, that if an oblong surface were curved, the loss in power in the rear half of a plane might be overcome. The investigations of others, notably Horatio Phillips, Prof. S. P. Langley, Sir Hiram Maxim, and the Wright Brothers, have confirmed his opinion. Hence, despite their name, the best aeroplanes of to-

THE PLANE IN THE AIR 29

day are made not with flat, but with surfaces slightly curved from front to rear (Fig. 7), so that the rear part of a plane can " grip " the air almost as well as the entering edge. De-

B

FIG. 8 — A is a simple inclined plane; B, a curved plane at the same angle of incidence or inclination; C, the type of curved plane which has thus far given the best results in the air.

spite the curvature, however, there is an ap- preciable loss in lifting power, back of the entering edge.

The general shape which a plane should have must be considered as well as the entering edge. Much experimental research has shown that the best plane is not only curved back and

30 THE NEW ART OF FLYING

down, but is also convex on top. What is more, it has been found that it should be somewhat thicker nearer the front. Just where the thick- est part should lie is still a matter of doubt; but most designers place the thickest part at a distance from the front edge not more than a third of the total width of the plane (Fig. 8) . A kite must be held at an angle to the wind if it is to fly. So must an aeroplane. Just what that angle should be varies with the circum- stances of flight. The flatter the angle (in other words, the more horizontal the position of the aeroplane) the speedier will be the fly- ing-machine. The greater the angle of the plane, the greater will be the resistance offered and the greater will be the power required to drive the plane. Still, this greater angle will enable the flying-machine to rise more quickly in the air, because the lifting power is greater. It is easy to see that the aviator must select such an angle for his planes that his machine will be as speedy as possible, as economical of power as possible, and that it will have as much lifting power as possible. The angle in practical flying- machines varies usually from one in seven to

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one in twenty. What does that mean? It means that a plane having an angle of one in ten will push the air down at one tenth of the forward velocity and that the plane will rise one foot in ten relatively to the forward movement.

An aeroplane driven through the air is acted upon by two forces, — its weight and its hori- zontal momentum. Because it has weight it is always falling. If its horizontal momentum (its speed) is greater than the rate of its fall, it will stay in the air, which means not only that it has not time enough to fall visibly but that it may even ascend. Suppose that a plane trav- elling at the rate of ten miles an hour has just sufficient horizontal momentum to prevent its falling. If the speed be increased to twenty miles an hour, the plane will not only be pre- vented from falling, but will actually rise in the air, because of the plane's angle of inclination. Hence to prevent the plane from rising at a speed of twenty miles an hour, the angle must be flattened. Therefore substantially horizon- tal flight may be maintained by proper adjust- ment of speed and angle (Fig. 9).

32 THE NEW ART OF FLYING

The angle of incidence varies with the wind, with the power of the motor, with every devia- tion of the plane from a uniform line, and with every variation of the load. If a machine car- ries two men, the angle will be greater than if

E D

FIG. 9. — The plane B B is at a greater angle of incidence than the plane A A. If its speed be 10 miles an hour, it will, while travelling horizontally 25 feet, overcome its tendency to fall to D. If its speed be 20 miles an hour, it will have 50 feet to travel while overcoming its ten- dency to fall to E. Unless the angle of B B, therefore, were decreased to that of A A for the greater speed, the plane would not move horizontally but would ascend.

one is carried; when the fuel tank is full the angle will be greater than when the tank is empty, and will vary as the fuel is used. More- over, when the power of the motor increases or decreases, the speed correspondingly increases or decreases and causes the angle of incidence to increase or decrease. Even with constant- power, the speed is different in ascending and

THE PLANE IN THE AIR 33

descending, and the angle of incidence varies accordingly. The Wright Brothers state that during a flight of one hour the angle of inci- dence will be either greater or less than any angle which may be termed normal, for more than fifty-nine minutes, and that it will be ex- actly at the normal angle less than one minute. In their experience the angle of incidence varies in flight throughout a range of ten degrees or more and is particularly great when the wind is turbulent. For that reason, among others, the control of an aeroplane in flight requires incessant vigilance on the part of the pilot.

In most forms of locomotion, increased speed is obtained at the expense of power. When you run, you expend more energy than when you walk. A locomotive driven at high speed uti- lises more power than at low speed. Paradoxi- cally enough, the aeroplane follows no such rule. The late Professor Langley discovered that the higher the speed of an aeroplane, the less power is required to drive it. Langley was considering surfaces only. Wires and struts must also be considered, and their re-

34 THE NEW ART OF FLYING

sistance (increasing with the square of the velocity) is such that, as Herring has pointed out, flight without motor is impossible on ac- count of the resistance offered by wires alone. Theoretically at least, it seemed to Langley that a speed could be reached where the power received would be nil. The Wrights and other aviators maintain, however, that there is a close limit to this economy of power with ac- celerated speed. The early experiments of Langley, Maxim and Chanute seemed to show that at high speed increased lifting power is obtained, but how much the increase may be not all the experimenters agree. Con- trary, to the early experimenters, the Wright Brothers maintain that there is no practical advantage in increasing speed to obtain in- creased lifting power. High speed renders it possible to reduce the size and weight of the machine, which in turn means a reduction in atmospheric resistance.

The first glimpse of a flying-machine in the air is a disappointment, not because the flying- machine really flies, but because it apparently flies so slowly. The speed appears less than

THE PLANE IN THE AIR 35

it really is, and it is only when it is accurately measured that it reaches the hoped-for figure. The speed of many of the early biplanes was not much above thirty miles an hour, and most of the modern biplanes probably do not exceed forty miles. Monoplanes now travel often at a speed of not less than sixty miles. Many of the Bleriot monoplanes make considerably over seventy miles an hour on a straight line. At Reims, in 1910, over seventy miles an hour was attained. It is evident that in the near future eighty miles an hour on a straight course is well within the bounds of probability.

In an aeroplane speed is of more importance than any other vehicle, because the aeroplane is far more affected by the wind. A boat, to be sure, is affected by both tide and wind, but not to such an extent as the aeroplane. A strong tide runs only about two knots, while the speed of a fast boat is some ten times this, so that her speed is reduced only ten per cent when running against the tide. An aeroplane, however, is very much more influenced, simply because an ordinary breeze has a velocity of fifteen miles an hour, a strong wind thirty to

36 THE NEW ART OF FLYING

forty miles an hour, and a gale, sixty miles an hour. The aeroplane, in order to be a service- able vehicle of sport, must be able to make good speed against a thirty-mile wind. In other words, it should be able to obtain a ve- locity of sixty or seventy miles an hour, under favourable conditions. Such fast flying, how- ever, complicates the problem of starting and alighting. Landing at high speed is especially dangerous. As long as the method of alight- ing is what it is now, that is, as long as the machine runs along the ground for some dis- tance, it can hardly be safe to land at speeds in excess of those used at present. It is evi- dent, therefore, that it may be necessary to devise a machine which will fly over a consider- able range of speed, so that it can be slowed down before landing. The minimum speed at which an aeroplane will fly is dependent chiefly on the ratio of wing surface to weight. There- fore, to fly slowly we must have large wings in proportion to the weight. Small wings, on the other hand, give high speed, and the small wings on Bleriot and Wright racers seem to be very small indeed.

THE PLANE IN THE AIR 37

In order that the aeroplane may have a vari- able speed, it must either have large wings, so designed that they can be driven fast without, resistance, or else we must have some me^ns of reducing the surface of the wings in the air. In the former case, the angle of incidence of the wings is reduced, which would seem to be at least theoretically obtainable, whatever may be the difficulties in making the curves of the wings suitable for various speeds.

Reefing the wing surfaces is a still better method of obtaining variable speeds, but the practical difficulties are formidable. Furling a wing when travelling at forty miles an hour in the air can hardly be easy. Taking in sail in a gale of wind on a boat has its difficulties, and an aeroplane travels at the speed of a gale. For all that, we find that attempts are made, even now, to build machines on this principle.

Before we can advance much farther in aero- plane construction we must conduct more sys- tematic investigations of various kinds of sup- porting surfaces. Several laboratories are now engaged in such researches, but the results of

38 THE NEW ART OF FLYING

their labours will hardly be available for some years to come.

It is the general practice of ship-builders to test new forms of hulls by towing models of a few yards in length through the water and by measuring the resistance opposed to their mo- tion. No large ocean steamer is now con- structed without such preliminary experiments. Tests with aeroplane models are still more necessary, because in the air we are, as yet, more or less inexperienced. In both cases one of the chief objects of study is the total resist- ance to motion, and the discovery of the form which will reduce this resistance to the lowest possible point. Other important questions con- cern the distribution of pressure and skin fric- tion in their dependence upon the form and character of surface. The investigation of sta- bility and steering qualities also requires ex- periments with models, which may likewise give interesting information on the lifting power or kite action of an aeroplane when inclined to the horizontal. It is necessary to study thoroughly the magnitude and direction of the resultant force on single surfaces of

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various forms, on combinations of surfaces, and finally on complete aeroplanes, as well as the stability and steering qualities of these com- binations. It is easier and cheaper to learn from models all that they can teach us than to make the experiments with large and expensive craft, which has been the practice in the past. It is a question, however, how far the results ob- tained from models can be applied to the large vessels. Even small models of ships' hulls, which are tested in towing tanks, do not give absolute results. In aeroplanes, the method may be still more untrustworthy because the aerial craft is completely surrounded by the medium through which it travels and because the carriage generally creates more disturbance in the air than the model, a disturbance suffi- ciently great to make exact measurements im- possible. By substituting for the towing car- riage a cord wound on a windlass, this objec- tion is removed, but it remains very difficult to distinguish sharply between the comparatively small air resistances and the great force of inertia of the heavy model. M. Eiffel has made some excellent experiments with bodies freely

40 THE NEW ART OF FLYING

falling through the air. The method fre- quently employed of carrying the model around in a circle by means of a long rotating arm, or on a whirling table, is open to the objec- tion that the model is always moving in air which has been disturbed by its last passage. There is still a third method, which consists in maintaining the model at rest in a current of air produced, for example, by a blower. The mutual action between the model and the air is exactly as in the former system, if the condition of the moving air before it strikes the model is as uniform as that of still air. The trustworthiness of results obtained by this method depends, therefore, upon obtaining a uniform current free from eddies, which end can be attained by the employment of various appliances. When a uniform current has been secured, the advantages of this method are great and obvious. The duration of the ex- periment is unlimited, and the model can be attached to its support much more easily and securely than if it were in motion. Further- more, the difficulties produced by the accelera- tion and inertia of the model on a measuring

THE PLANE IN THE AIR 41

apparatus are here avoided. The model is continuously in sight, so that any irregularities can be at once detected. This system has been adopted in the Goettingen Experimental Insti- tute, planned and directed by Professor Prandtl.

CHAPTER IV

STARTING AND ALIGHTING

IN a previous chapter it has been pointed out that like every soaring bird an aeroplane must be in motion before it can fly. Even the early dreamers appreciated the fact. How that pre- liminary leap into the air is to be effected gave Langley no little concern. With the motorless gliders of Lilienthal, Pilcher, and Chanute, it was no difficult matter for the aeronaut to launch himself into the air. He simply carried his apparatus to the top of a hill, grasped the handle-bar, ran down the hill at top speed for a short distance, and then drew up his legs, like any bird. Thus he would slide down the air for several hundred feet as if upon an invisible track.

When Langley succeeded in building a small, motor-driven model of a flying-machine, the problem of launching his contrivance long baffled him. Eventually he invented a launch- ing device, which has served as a pattern for

STARTING AND ALIGHTING 43

later inventors. The difficulties which beset him were eloquently and lucidly described in an article from his pen, published in McClure's Magazine for June, 1897. The whole prob- lem is there so well and so simply presented that we cannot do better than to let Mr. Lang- ley set it forth himself, even though launching a flying-machine is now regarded as a simple matter:

" In the course of my experiments I had found out . . . that the machine must begin to fly in the face of the wind and just in the opposite way to a ship, which begins its voyage with the wind behind it.

" If the reader has ever noticed a soaring bird get upon the wing he will see that it does so with the breeze against it, and thus when- ever the aerodrome * is cast into the air it must face a wind which may happen to blow from the north, south, east or west, and we had better not make the launching station a place like the bank of a river, where it can go only one way. It was necessary, then, to send it from something which could be turned in any direc- tion, and taking this need in connection with

* * Langley's term for an aeroplane flying-machine, signifying " air-runner."

44 THE NEW ART OF FLYING

the desirability that at first the airship should light in the water, there came at last the idea (which seems obvious enough when it is stated) of getting some kind of a barge or boat and building a small structure upon it which could house the aerodrome when not in use, and from whose flat roof it could be launched in any direction. Means for this were limited, but a little " scow " was procured, and on it was built a primitive sort of house, one story high, and on the house a platform about ten feet higher, so that the top of the platform was about twenty feet from the water, and this was to be the place of the launch. This boat it was found necessary to take down the river as much as thirty miles from Washington, where I then was — since no suitable place could be found nearer — to an island having a stretch of quiet water between it and the main shore; and here the first experiments in at- tempted flight developed difficulties of a new kind — difficulties which were partly antici- pated, but which nobody would probably have conjectured would be of their actually formi- dable character, which was such as for a long time to prevent any trial being made at all. They arose partly out of the fact that even such a flying-machine as a soaring bird has to get up an artificial speed before it is on the

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wing. Some soaring birds do this by an initial run upon the ground, and even under the most urgent pressure cannot fly without it.

uTo get up this preliminary speed many plans were proposed, one of which was to put the aerodrome on the deck of a steamboat, and go faster and faster until the head-wind lifted it off the deck. This sounds reasonable, but it is absolutely impracticable, for when the aero- drome is set up anywhere in the open air, we find that the very slightest wind will turn it over, unless it is firmly held. The whole must be in motion, but in motion from something to which it is held until that critical instant when it is set free as it springs into the air.

" The house boat was fitted with an appara- tus for launching the aerodrome with a certain initial velocity, and was (in 1893) taken down the river and moored in the stretch of quiet water I have mentioned; and it was here that the first trials at launching were made, under the difficulties to which I have alluded.

" It is a difficult thing to launch a ship, al- though gravity keeps it down upon the ways, but the problem here is that of launching a kind of ship which is as ready to go up into the air like a balloon as to go off sideways, and readier to do either than to go straight forward, as it is wanted to do, for though there is no gas in

46 THE NEW ART OF FLYING

the flying-machine, its great extent of wing surface renders it something like an albatross on a ship's deck — the most unmanageable and helpless of creatures until it is in its proper element.

" If there were an absolute calm, which never really happens, it would still be impracticable to launch it as a ship is launched, because the wind made by running it along would get under the wings and turn it over. But there is always more or less wind, and even the gentlest breeze was afterward found to make the airship un- manageable unless it was absolutely clamped down to whatever served to launch it, and when it was thus firmly clamped, as it must be at several distinct points, it was necessary that it should be released simultaneously at all these at the one critical instant that it was leaping into the air. This is another difficult condi- tion, but that it is an indispensable one may be inferred from what has been said. In the first form of launching piece this initial velocity was sought to be attained by a spring, which threw forward the supporting frame on which the aerodrome rested; but at this time the extreme susceptibility of the whole construction to in- jury from the wind and the need of protecting it from even the gentlest breeze had not been appreciated by experience. On November 18,

STARTING AND ALIGHTING 47

1893, the aerodrome had been taken down the river, and the whole day was spent in waiting for a calm, as the machine could not be held in position for launching for two seconds in the lightest breeze. The party returned to Wash- ington and came down again on the 2Oth, and although it seemed that there was scarcely any movement in the air, what little remained was enough to make it impossible to maintain the aerodrome in position. It was let go, notwith- standing, and a portion struck against the edge of the launching piece, and all fell into the water before it had an opportunity to fly.

" On the 24th another trip was made and another day spent ineffectively on account of the wind. On the zyth there was a similar experience, and here four days and four (round-trip) journeys of sixty miles each had been spent without a single result. This may seem to be a trial of patience, but it was re- peated in December, when five fruitless trips were made, and thus nine such trips were made in these two months and but once was the aerodrome even attempted to be launched, and this attempt was attended with disaster. The principal cause lay, as I have said, in the un- recognised amount of difficulty introduced even by the very smallest wind, as a breeze of three or four miles an hour, hardly perceptible to the

48 THE NEW ART OF FLYING

face, was enough to keep the airship from rest- ing in place for the critical seconds preceding the launching.

" If we remember that this is all irrespective of the fitness of the launching piece itself, which at first did not get even a chance for trial, some of the difficulties may be better understood; and there were many others.

" During most of the year of 1894 there was the same record of defeat. Five more trial trips were made in the spring and summer, dur- ing which various forms of launching apparatus were tried with varied forms of disaster. Then it was sought to hold the aerodrome out over the water and let it drop from the greatest at- tainable height, with the hope that it might ac- quire the requisite speed of advance before the water was reached. It will hardly be anticipated that it was found impracticable at first to simply let it drop without something going wrong, but so it was, and it soon became evident that even were this not the case, a far greater time of fall was requisite for this method than that at com- mand. The result was that in all these eleven months the aerodrome had not been launched, owing to difficulties which seem so slight that one who has not experienced them may wonder at the trouble they caused.

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STARTING AND ALIGHTING 49

" Finally, in October, 1894, an entirely new launching apparatus was completed, which em- bodied the dozen or more requisites, the need for which had been independently proved in this long process of trial and error. Among these was the primary one that it was capable of sending the aerodrome off at the requisite initial speed, in the face of a wind from whichever quarter it blew, and it had many more facilities which practice had proved indispensable."

Langley's account has a certain historical interest, because never before had a motor- driven machine been brought to such a pitch of perfection that it could fly, if once launched. After his repeated failures, Langley finally succeeded in launching his craft from " ways," as shown in Fig. n, somewhat as a ship is launched into the water, the machine resting on a car, which fell down at the end of the car's motion.

A launching device identical in principle was afterwards employed to start the man-carrying machine built by Langley for the United States Government. Once, according to Major Ma- comb, of the Board of Ordnance, u the trial was

50 THE NEW ART OF FLYING

unsuccessful because the front guy post caught in its support on the launching car and was not released in time to give free flight, as was in- tended, but, on the contrary, caused the front of the machine to be dragged downward, bend- ing the guy post and making the machine plunge into the water about fifty yards in front of the house boat." Of another trial Major Macomb states . . . " the car was set in motion and the propellers revolved rapidly, the engine working perfectly, but there was something wrong with the launching. The rear guy post seemed to drag, bringing the rudder down on the launch- ing ways, and a crashing, rending sound, fol- lowed by the collapse of the rear wings, showed that the machine had been wrecked • in the launching; just how it was impossible to see.'* Because it was never launched, the machine never flew. The appropriation having been exhausted, Langley was compelled to abandon his tests. The newspaper derision which greeted him undoubtedly embittered him, short- ened his life, and probably set back the date of the man-carrying flying-machine's advent several years. Langley's trials have been here

STARTING AND ALIGHTING 51

set down at some length to show the practica- bility and impracticability of various launching methods and to demonstrate that his machine was far from being the failure popularly sup- posed. No man has contributed so much to the science of aviation as the late Samuel Pier- pont Langley.

That his work was not lost on the Wright Brothers at least, is evidenced by the manner in which they attacked the difficulty of getting up starting speed. The Wright Brothers in- vented an arrangement, which was simpler than Langley's, more efficient, and not so likely to imperil the aeroplane. As illustrated in Fig- ures 12 and 13, it consisted in its early stage of an inclined rail, about seventy feet long; a pyramidal " derrick " ; a heavy weight ar- ranged to drop within the derrick; and a rope which was fastened to the weight, led around a pulley at the top of the derrick, passed around a second pulley at the bottom of the derrick and over a third pulley at the end of the rail, and then secured to a car. The car was placed on the rail, and the aeroplane itself on the car. When a trigger was pulled, the weight

52 THE NEW ART OF FLYING

fell, and the car was jerked forward. So great was the preliminary velocity thus imparted that the machine was able to rise from the car in a few seconds.

FIG. 12. — The special launching device invented by the Wright Brothers. The device consists of an inclined rail, about seventy feet long; a pyramidal derrick; a heavy weight arranged to drop within the derrick; and

[ a rope, which is fastened to the weight, passed around a pulley at the top of the derrick, then around a second pulley at the bottom of the derrick over a third pulley at the end of the rail, and finally fastened to a car running on the rail. The car is placed on the rail, and the aeroplane on the car. When a trigger is pulled, the weight falls, and the car is jerked forward. So great is the preliminary velocity thus imparted that the machine is able to rise in a few seconds from the car, which is left behind.

Neither a falling weight nor a starting car- riage on rails can be carried with an aero- plane. Hence, a machine thus launched must always return to its derrick. Clearly, an aero- plane which can start up under its own power is preferable to one which is wedded to a start- ing derrick or any other extraneous launching

STARTING AND ALIGHTING 53

apparatus. Inasmuch as more power is re- quired for starting by running on the ground (i. e., for accelerating the machine) than for actual flight, the Wright Brothers continued to employ their starting rail long after other avi- ators had adopted wheels. The result was that they could equip their machine with motors of far less power than their rivals.

Even before the Wright Brothers threw aside all secrecy and flew publicly in France and the United States during the summer of 1908, Curtiss and Farman had made short flights on machines which were mounted on pneumatic-tired wheels. Their machines would run on the wheels for several hundred feet. When sufficient velocity had been attained the pilot would give a slight upward tilt to the ele- vating rudder, and the machine would leave the ground. The only essential was a fairly smooth, fairly hard piece of ground for the preliminary run. So successful has this system been that in somewhat improved form it is embodied in every modern aeroplane. Even the Wright Brothers, who long persisted in using the starting derrick in the face of the

54 THE NEW ART OF FLYING

obvious advantages of wheels, abandoned the starting derrick as soon as they had increased the power of their motors. In Fig. 14 one of their later machines is pictured, mounted on wheels.

Although starting wheels enable the aviator to rise from any suitable piece of ground, he pays for that advantage in engine power. A well-made machine, having ample power to fly, but dependent only on its engine and rubber-tired wheels for its initial run, may be unable to rise if the ground is too rough. The engine cannot overcome the loss due to fric- tion. On hard asphalt the cyclist can readily attain a speed of twenty-five miles an hour in a few seconds; on a ploughed field, he may labour hard and yet not make more than ten miles an hour. The aeroplane is in the same position as the bicycle. To start a flying- machine on rough ground requires more power than is afterwards needed for propulsion. Hence we find that the earlier Wright ma- chines, although they could rise only from the perfect surface of a starting rail, were fitted with engines of remarkably low power.

Photograph by Edwin Levick

Fig. 20. — Mr. Wilbur Wright in the old type Wright biplane

STARTING AND ALIGHTING 55

The wheels on which the preliminary run is made may also serve the aviator in alighting. After he shuts off his engine he glides down and runs on the wheels until his momentum is expended. The shock may be sufficient to wreck a machine piloted by an unskilled hand, and the run may be long, unless some form of brake is provided. Recognising these disad- vantages early in the course of their experi- ments, the Wright Brothers fitted their aero- planes with skids or runners on which the machine alighted. The shock is almost im- perceptible, and the machine stops in the course of a few yards without the assistance of a brake. Many machines are now equipped with skids similar to those embodied long ago by Herring and by the Wright Brothers in their early models.

Starting wheels and alighting skids are not easily combined in the same machine. The skids must be elevated sufficiently to clear the ground in making the preliminary run, and yet they must become effective as soon as the ma- chine touches the ground. For that reason the wheels are usually connected with springs,

56 THE NEW ART OF FLYING

which are compressed as the aeroplane strikes the ground so as to allow the skids to perform the function for which they are designed.

In the Farman biplane, for example, the wheels are mounted on the skids and are at- tached to rubber springs. When the machine alights the wheels yield, and the skids come into play.

In the Sommer biplane, the framework is carried on two large wheels at the front and two smaller wheels at the rear. The front wheels are attached by rubber springs to two skids, built under the frame. As in the Farman machine, the wheels yield by virtue of this spring mounting.

In Santos-Dumont's monoplane " Demoi- selle," springs are dispensed with. The ma- chine starts on two wheels in front and the shock of alighting is broken by a skid at the rear.

An arrangement similar to that of Santos- Dumont is to be found in the Antoinette ma- chines. The mounting consists of two wheels at the front and a skid at the rear. No springs are provided for the wheels.

STARTING AND ALIGHTING 57

In the Curtiss and Voisin biplane machines, as well as in some others of minor importance, no skids at all are employed. The machine starts and alights on the same set of wheels, and is usually stopped by brakes. On the whole the combination of wheels and skids seems to be more desirable, particularly for a heavy machine.

CHAPTER V

HOW AN AEROPLANE IS BALANCED

DROP a flat piece of cardboard from your hand. It will fall. But as it falls its surface will offer a certain resistance, so that it becomes in effect a parachute. The amount of its resistance will

FIG. 16. — Path of an aeroplane driven forward but with a speed too low for horizontal flight, and with too flat an angle.

depend on the amount of its surface. If the cardboard be driven to the left, as shown in Fig. 1 6, it will still fall, but along an inclined path. In other words it will fall while advanc- ing and advance while falling.

Suppose that this same piece of cardboard, this aeroplane, as we may call it, is inclined to

BALANCING AEROPLANES 59

the wind and that it is driven along a horizontal path B in the direction of the arrow A as shown in Fig. 17. If it were not driven forward the cardboard plane would fall by reason of its weight. But since it is driven forward and since it is inclined to the air, it offers resistance, which means that pressure is exerted upward against

Rear Edge

FIG. 17. — Path of a plane inclined at the angle C to the horizontal. The arrow A indicates the direction of travel. If the speed is sufficient the plane will rise be- cause of the upward inclination of the plane.

its lower surface. The driving power, what- ever it may be, overcomes the resistance or pressure; yet the effect of the resistance or pressure is to keep the plane up in the air. So, the plane tends to slide up diagonally on the resisting air; gravity (weight) tends to draw the plane down toward the earth; and the diag- onal sliding action tends to move the plane farther from the earth. This climbing effect is obviously dependent on the angle of the plane.

60 THE NEW ART OF FLYING

If the angle is large, it is great; if the angle is small, it is slight. Given a very high speed of propulsion, a speed greater than the falling tendency, and the plane is bound to rise. Given a speed of propulsion less than the falling ten- dency and the plane will sooner or later settle to the ground. Horizontal flight can therefore be maintained by proper adjustment of speed and angle.

This angle at which the plane moves against the air is known as the " angle of incidence." It is positive, because it has a tendency to lift. If the plane were tilted forward or dipped, the sliding effect would be earthward. Indeed, so marked would be this effect that the plane would reach the ground much more quickly than if it fell simply by its own weight. In that case the angle of incidence is negative, because it depresses.

It is therefore evident that an advancing aeroplane may be caused to travel up or down simply by making the angle of incidence posi- tive or negative.

During flight, a Wright or Curtiss or Bleriot machine is subjected to every whim of the air.

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These incessant variations of the air must all be counteracted; otherwise the machine will capsize.

It happens during flight that the aeroplane, because of the wind's caprice, will drop more on one side than on the other. To maintain his balance, the aviator must in some way lift the falling side or lower the rising side, or do both. It was this problem that long baffled the in- ventor of aeroplane flying-machines. The whole art of machine-flying is summed up in its successful solution. To the Wright Brothers of Dayton, Ohio, belongs the full credit of having devised the first and thus far the most efficient means of solving that problem, a means now em- bodied in almost every successful flying-machine.

Suppose that the plane A in Fig. 1 8 is pro- vided at each side with tips C and D, hinged so that they can be swung up or down. If these two tips (ailerons the French call them) are swung so that they lie flush with the main plane A, they have no effect whatever beyond adding to the amount of aeroplane surface. Suppose that the near side of the plane drops. In that case, the tip C is thrown down as shown

62 THE NEW ART OF FLYING

in Fig. 1 8. What happens? More resistance is offered to the air at that side and greater upward pressure is consequently exerted, so that the plane is restored to its former position

Direction of Plane's Motion

Direction of Air Pressure

FIG. 18. — How a plane is laterally balanced by means of ailerons and a vertical rudder.

The plane A is provided with hinged tips C and D and with a vertical rudder E. The tips are swung in opposite directions to correct any tipping of the plane, and the vertical rudder E is swung over to the side of least re- sistance (the side of the tip D in the example here given) in order to prevent the entire machine from rotating on a vertical axis.

of equilibrium. To assist in this restoration, the tip D at the farther side of the plane can be tilted down, so that the angle of incidence is negative or depressive. Hence the far end of the plane is lowered while the near end is raised. In all flying-machines this dropping of one tip and raising of the other is effected simultane- ously by a system of cables and levers. When

BALANCING AEROPLANES 63

the plane's balance has been regained, the tips are swung so that they lie flush with the plane A, and become virtually part of the plane.

As a result of inclining the tips at opposite angles, the near side of the plane offers more resistance to the air than the far side. Hence the near side will be retarded and the far side accelerated. This will cause the entire plane to swerve from its course. It was a brilliant discovery of the Wright Brothers to correct this swerving by means of a vertical rudder E, which is thrown over to the side of least resist- ance — the far side in the particular instance pictured in Fig. 18. The wind pressure on the rudder exerts a counteracting force at the rear of the machine and opposes the tendency of the machine to turn. Hence the vertical rudder in flying-machines serves not nearly so much for steering as for preventing the spinning of the machine.

The actual controlling method devised by the Wrights is shown in Fig. 19. Instead of one plane, the Wrights employ two superposed planes A and A' trussed together. In front or rear is a horizontal rudder or elevator to steer

64 THE NEW ART OF FLYING the machine up or down, which rudder in the example before us (an old Wright type al- though the principle is the same in the new) consists of two superposed planes, 5 and 6, and which is operated by the lever F' through the medium of connecting rods. In the

FIG. 19. — The system of control on an old Wright model.

rear is the vertical rudder C, which serves to steer the machine from side to side and to coact with the planes A and A' in keeping the ma- chine on its course. Instead of employing pivoted tips like those shown in Fig. 18, the Wrights warp the corners of the planes A and A'. Thus, when the corners i and 2 are ele- vated, the corners 3 and 4 are depressed. This simultaneous elevation and depression of cor- ners is produced by a cable E, attached to a lever F'. By throwing the lever from side to

BALANCING AEROPLANES 65

side the planes are warped. The vertical rud- der C is connected by tiller ropes with the same lever F', and is swung by moving the lever P back and forth. Hence the planes are warped and the vertical rudder properly turned by the one lever F'. The photograph reproduced in Fig. 20 shows Mr. Wilbur Wright seated in his machine /with his hands on the controlling levers. Fig. 2 1 pictures the Wright machine on the ground and shows the disposition of the main planes, horizontal or elevation rudders, and ver- tical rudder. Fig. 22 depicts an instruction machine with an extra lever for the pupil.

Some of the machines which Mr. Glenn H. Curtiss has flown are similarly provided with two superposed main planes A and J9, as shown in Fig. 23, with a box-like rudder in front and with a rear vertical rudder D. The front horizontal rudder is swung up or down by means of the rod R connected with the wheel TV, the wheel being pushed or pulled by the pilot for that purpose. The same wheel JV, when rocked like the pilot wheel of a steam- boat serves to swing the vertical rudder D by drawing on one or the other of two tiller ropes,

66 THE NEW ART OF FLYING

S. In his earlier machines, as, for example, the one illustrated in Fig. 24, Curtiss employed supplementary plane tips, very much like those represented in Fig. 18. In his later machines, however, one of which is shown in Fig. 25, he

FIG. 23. — The Curtiss system of control.

has transferred the tips from the sides of the main planes to positions between the main planes, beyond which they project, as indicated by the letters C C in Fig. 23. Despite the trans- fer their purpose still remains the same. To swing the supplementary planes C C in opposite directions, cables T T are connected with the seat-back G, which is movable from side to side

BALANCING AEROPLANES 67

and which partly encircles the pilot's body. By throwing his body from side to side the pilot swings the planes C C in opposite directions. The effect is the same as if the main planes A B were warped, as in the Wright machine. Whether or not it is necessary to throw over the vertical rudder when the balancing planes C C are- swung is the question at issue in the patent infringement suit instituted by the Wright Brothers against Curtiss. The Wrights claim that Curtiss cannot fly unless the vertical rudder is operated simultaneously with the balancing planes. Curtiss claims that he can. Much testimony has been taken on both sides. A United States Circuit Judge thought that the preponderance of expert evidence was on the side of the Wrights, particularly since Curtiss himself admitted that he did sometimes use the vertical rudder to offset the swerving of the machine caused by changing the incli- nation of the balancing planes. A preliminary injunction was therefore issued, which, on ap- peal, however, was dissolved. Whether or not Curtiss can fly without simultaneously operat- ing his vertical rudder and his balancing planes

68 THE NEW ART OF FLYING

FIG. 26. — The system of ailerons and rudders devised by Henry Farman for maintaining fore-and-aft and side-to-side balance.

BALANCING AEROPLANES 69

will be decided when the question of infringe- ment is settled at the final hearing.

In the Farman biplane, which the Wright Brothers allege likewise infringes their patent, the ailerons, as illustrated in Fig. 26, form part of the main planes A B. They are the hinged flaps D D at the rear corners of the main planes. The inclination of the ailerons D D is varied by means of cables leading to the lever C. By moving the lever C from side to side, the aile- rons are moved up and down in opposite direc- tions. To the rear of the main planes two ad- justable rudders E E are placed, from which two wires lead to a tiller F operated by the pilot's feet. When the aeroplane tips to the left, for example, the pilot swings his control-lever C to the right, thus pulling down on the flaps on the left-hand side of the planes and creating more lift on that side. The right-hand flaps remain horizontal, held out by the air pressure. When the machine is at rest on the ground, the flaps hang down vertically, as shown in Fig. 27. In Fig. 28 Mr. Farman is shown seated in his biplane. His hand grasps the lever by means of which both the ailerons or flaps and the

70 THE NEW ART OF FLYING

forward horizontal or elevation rudder are operated.

In his later machines Mr. Curtiss has pro- vided ailerons similar to those of Farman, as shown in Fig. 29.

The Bleriot monoplane, which is also in- volved in this Wright litigation, is outwardly at

FIG. 30. — The Bleriot system of control.

least more like the Wright machine in the mech- anism for maintaining side-to-side balance. Its single supporting plane is warped at the sides by a lever and a system of cables, as shown in Fig. 30. The single supporting plane is rigidly trussed along its front edge, but a cable is at- tached to one rear corner at / and passes down- ward, and toward the centre to a pulley F (Fig. 31) actuated by a lever K, and upward

BALANCING AEROPLANES 71

to the opposite rear corner of the plane /' (Fig. 30). By moving the lever K to one side, the cable pulls down the side rear portion of the

FIG. 31. — The steering and control column of the Bleriot monoplane. The wheel L, the post K, and the bell-shaped member M form one piece and move together. Wires O connect the bell with the yoke G, carrying the pulley F, around which the wires H running to the flexible por- tions of the supporting planes are wrapped. By rocking the post and bell from side to side in a vertical plane the wires H are respectively pulled and relaxed to warp the planes. By moving the post K back and forth the horizontal rudder is operated through the wires P. These various movements of the post can be effected by means of the wheel L, which is clutched by the aviator's hands, or by means of the bell M, which can be clutched by the aviator's feet if necessary.

72 THE NEW ART OF FLYING

plane at one tip to a greater angle of incidence than the normal plane of the body of the aero- plane, and permits the opposite side rear por- tion to rise to an angle of less incidence. Thus the whole plane is warped, and the portions lying at the opposite tips are presented to the air at different angles of incidence. The ver- tical adjustable rudder R (Fig. 30) is located at some distance to the rear of the main plane, and wires lead from it to a tiller operated by the feet. When the pilot warps the plane he swings the rudder to prevent the machine from spinning. By moving the lever K back and forth the horizontal rudder is rocked up and down.

In the Antoinette monoplane the horizontal or elevation rudder and the stabilising mech- anism are quite independent. The vertical rudder consists of two vertical triangular sur- faces at the rear. They are moved jointly by means of wire cables running from a tiller worked by the aviator's feet. When this tiller, which moves in a horizontal plane, is turned to the left, the aeroplane will turn to the left. The elevation rudder in the Antoinette mon-

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BALANCING AEROPLANES 73

oplane consists of a single triangular horizon- tal surface placed at the extreme rear. It is governed by cables leading from a wheel placed at the aviator's right hand (Fig. 32). To ascend, the wheel is turned up. This causes a decrease in the inclination of the ele- vation rudder relatively to the line of flight, and the machine, therefore, rises. Side-to-side bal- ance was at one time maintained by ailerons, as shown in Fig. 33. Latterly it is maintained by warping the outer ends of the main plane very much as in the Wright machine. But the front ends are movable and the rear ends rigid throughout in the new Antoinette, while the opposite is the case in the Wright biplane. The wheel at the aviator's left hand, through cables and a sprocket gear, placed at the lower end of the central mast, controls the warping. For cor- recting a dip downward on the right the right end of the wing is turned up, and at the same time the left end is turned down, thus restoring balance.

Warping a plane and rocking an aileron are not the only ways of maintaining side-to-side balance. The late Professor S. P. Langley dis-

74 THE NEW ART OF FLYING

covered that by cutting a plane in two and ar- ranging the two parts so that they would form a rather wide V when viewed from the front or rear (" dihedral angle " is the proper tech- nical term), a certain amount of automatic sta- bility would be obtained. He constructed his own successful small models on that principle. Bleriot, too, adopted it in at least one of his earlier machines. Although wasteful of power it is still a conspicuous feature of many French machines of the present day. Even in some recent biplanes, notably the racing Farman, it is to be found.

Still another way of obtaining a certain amount of automatic stability is to employ ver- tical surfaces to prevent tilting and to distribute the pressure more evenly over the main sur- faces. An example is to be found in the earlier Voisin machine, which is a biplane divided into cells by vertical curtains or partitions (Fig. 34). In practice, these partitions are found in- adequate, for which reason the pilot of this Voisin type must right his machine by steering with the rudder. Thus, if the machine cants up on the left and down on the right, he steers to

BALANCING AEROPLANES 75

the left. This brings the right side up again because it is suddenly called upon to travel more quickly through the air than the left side, in- creased speed resulting in increased elevation. This Voisin type is one of the few construc- tions that does not fall within the scope of the Wright patent. Farman, who was one of the first pilots that ever tried a Voisin, abandoned it for the aileron machine, which bears his name. In the new Voisin machines (Fig. 35) no cells at all are to be found, but instead ailerons sim- ilar to those adopted by Farman. On the whole it must be confessed that the most successful machines at the present time are those in which the side-to-side balance is maintained either by warping the wings or by means of ailerons.

Sometimes the vertical surfaces are distrib- uted along the frame of the machine in the form of keels. Although they contribute a cer- tain stability, it cannot be denied that they also increase the resistance and lower the speed. To prevent this so far as possible, and yet to retain whatever advantages they may have, it is customary to taper them. Examples of such tapering keels will be found on the Antoinette

76 THE NEW ART OF FLYING

and Hanriot monoplanes (Fig. 36, Frontis- piece). In a few years keels will probably dis- appear altogether. The advantages hardly offset the disadvantages. No special arrange- ment or design of keels has really ever suc- ceeded in insuring automatic stability. Even now the best designers confine them to the extreme rear of the machine, where they act somewhat like a bird's tail.

Mr. F. W. Lanchester, the distinguished English authority, has suggested that auto- matic stability can be insured by driving the aeroplane at speeds higher than those of the gusts, that are so liable to upset it. Just as the " Lusitania " at twenty-five knots dashes through waves and winds that would drive a fishing-smack to cover, so the high-speed aero- plane, in his opinion, would sail on, undeterred by the fiercest blast. Sixty miles an hour is the minimum speed that a machine should have, if his idea is correct. Moreover, he believes that, if the aeroplane is to have any extended use, it must travel very much faster than the motor-car.

Another means of attaining automatic sta-

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bility consists in varying the angle of incidence by rocking the whole plane on a horizontal axis, which is done by Esnault-Pelterie.

The foregoing explanation of stability and stabilizing devices applies only to side-to-side balance. Fore-and-aft balance can be obtained, as in birds, by tails, such as are found in the Curtiss, Bleriot, Antoinette, Santos-Dumont, Esnault-Pelterie, and indeed most machines.

The tail may be either a single horizontal surface or a cell, like a box kite. 'Almost every machine that now flies is provided with a tail to secure steadiness in flight. In the new Wright biplanes (Fig. 38) a single horizontal surface is used at the rear of the machine, a surface which also serves as an elevation rudder; for the Wrights have removed from the front of the machine those two parallel horizontal surfaces, which, in the early days of their work, were to them like the antennae of an insect, a means of feeling their way. The Wrights were the first who ever placed the rudder in front, and their example was quickly followed by Curtiss, Farman, Sommer, Voisin and other biplane makers. Whatever advan-

78 THE NEW ART OF FLYING

tages this forward position of the horizontal rudder may have, it is certain that it increases the tendency of the machine to pitch in flight, because of the long lever-arm provided by the rods connecting the forward rudders with the main framework. When the Wrights reversed themselves and removed the horizontal rudder from the front and placed it at the rear, where it performed not only its old function, but also served as a tail (an instrument with which the earlier Wright machines were not provided), their example was promptly followed by Voisin (Fig. 35), Breguet, Goupy, Caudron Freres and other constructors. It is safe to predict that in the future most biplanes will be provided with rear horizontal stabilising and elevating surfaces.

From the very first, monoplanes have been provided with rear horizontal or elevation rudders, probably because such is the example offered by every bird and because the late Pro- fessor Langley adopted them after much ex- perimenting. The Bleriot, Antoinette and other monoplanes have rear horizontal rudders and also tails.

BALANCING AEROPLANES 79

The tail corrects the see-saw motion or pitch- ing of a flying-machine in flight. The further back that it is placed the greater will be the steadying effect. If placed too far back, how- ever, a " dead centre " will be reached. If there is no tail the pilot must manipulate the horizontal rudder to check the see-saw motion. The Wrights have taken out a patent for a mechanical device, which maintains fore-and- aft stability automatically. In this device the human brain is supplanted by the pressure of the air on a plane. Compressed air is substi- tuted for muscular action. Lateral stability is

automatically maintained by means of a pendu-

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lum. The plane and pendulum open valves which admit compressed air to an engine oper- ating the horizontal or elevation rudder and warping mechanism.

To relieve the pilot of the physical strain of more or less constantly warping planes or ma- nipulating ailerons, it was suggested long be- fore the day of the Wrights that the flying- machine be provided with some automatic device which would prevent any capsizing tendency. The more important of such ap-

8o THE NEW ART OF FLYING

pliances are moving weights, pendulums, and gyrostats. A gyrostat is any rapidly rotating body, which, by virtue of its rotation, resists any force tending to move it from its plane of rotation. The greater the weight and the higher the speed of the gyrostat the greater must be the force expended to shift it from its plane of rotation. Hence if a gyrostat could be mounted on an aeroplane it certainly would tend to resist any unbalancing force, such as a gust of wind. Paul Regnard in France is said to have conducted very successful experiments with gyrostatically controlled aeroplanes. Rob- erts in England has also made more or less en- couraging tests. In his machine the gyrostat is applied as shown in Fig. 37.

The pilots of present machines object to any device that will relieve them entirely of all hand control. They would much prefer an auto- matic device which is immediately thrown out of operation when the hand-devices are manipu- lated. It is argued that a machine must be humoured, that with an automatic device such as the gyrostat, it is impossible to accommo- date the machine to variations in the wind.

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Moreover, there is the objection that the ma- chine must be elevated rapidly in starting, with a fairly large angle of incidence, but must after- wards assume a fairly flat angle for horizontal flight, with all of which a steadily running gyro- stat would seriously interfere. Soaring down a steep angle with motors at full speed could hardly be accomplished with a gyrostat run- ning at a fixed rate, for it is the gyrostat's tendency to resist movement. Besides, there is always the possibility that the motor which drives the gyrostat may stop, so that the avi- ator is helpless if no hand-controlled devices enable him to prevent rocking from side to side and pitching fore and aft.

The pendulum, as we have seen, has been suggested by the Wrights as well as by other inventors to relieve the aviator of his present duties. The underlying idea is that a freely suspended weight will always tend to hang down, and that it would be an easy mat- ter to connect with it elevation rudders and ailerons, in such a manner that pitching fore and aft, or rocking from side to side could be controlled by the effort of the pendulum to

82 THE NEW ART OF FLYING assume a perfectly normal position relatively to the earth. The pendulum, however, will hardly be likely to attain the desired end. It cannot control a flying-machine automatically, as Professor Prandtl has pointed out. The very force which causes an aeroplane to change its horizontal position in flight also retards it, accelerates it, or inclines it from side to side. Consequently a pendulum, which has the mo- mentum of the entire machine, will follow the direction of the aeroplane's inclination and, so far from hanging down, will deviate from the vertical. The result will be, curiously enough, that it will always maintain its posi- tion relatively to the planes, whatever their inclination fore-and-aft and side-to-side may be. Hence the pendulum is inoperative. Further- more, when an aeroplane is rounding a curve at the rate of from forty to sixty miles an hour, centrifugal force would completely nullify the action of the pendulum.

If a gyrostat is to be used, it is likely that it will be combined with some system of hand control, so that the aviator can depend upon the one or the other, as circumstances may dictate.

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But how this combination would really im- prove the situation it is difficult to see. .Auto- matic control is necessarily complicated. Hand control is admittedly dependent upon a cool head and an expert hand. Moreover, an auto- matic device must be made as small and as light as possible, for the aeroplane as it now stands is a machine in which the weight of every part has been reduced to a minimum. Can control mechanism, dependent upon a gyrostat, be made sufficiently light to meet the requirements of present construction? The more one con- siders the question, the more likely are we to believe that the best automatic machine is a well-trained hand.

Any one who has seen a skilled man steering a small boat in a heavy sea must realise that there is no possibility of making any automatic device which would take his place, and that any attempt to make the steering automatic by such means as a gyrostat would mean the certain swamping of the boat in a sea through which it could be steered quite simply by hand. The aeroplane is very much in the position of this small boat.

84 THE NEW ART OF FLYING

The danger of hand control is to be found in the possibility of making a false move. Locomotive engineers, signal men, automobile chauffeurs, are all of them in a position where a false move means a bad accident. Yet for all that, the number of errors which are made is comparatively small. A ship is dependent upon the engines and skill of the men in the pilot house ; yet it is but rarely that we hear of shipwrecks due to bad judgment in the wheel house. All things considered, it is very likely that aeroplanes will be hand controlled for years to come.

CHAPTER VI

MAKING A TURN

IN straightaway flight an aeroplane is balanced to a certain extent by the main supporting sur- faces (the large spread of which counteracts sudden inclination) and also by the position of the centre of gravity, which lies below the sup- porting surfaces in many machines. But when the vertical rudder is thrown over to swing the machine around, new forces come into play.

When a line of soldiers wheels around a street corner the man at the inner end of the line does little more than mark time; the man in the centre of the line marches along at a steady pace; while the man on the outside all but runs. In order that the line may be straight the movement must be progressively faster from the inner to the outer end. An aeroplane as it turns horizontally is in exactly the same predicament as a line of soldiers. The outer end of the machine must move faster than the inner end.

86 THE NEW ART OF FLYING

The accompanying illustration, Fig. 39, will make this clearer. Let us assume that the arc to be described is sixty feet in diameter, and

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FIG. 39. — An aeroplane of 40 feet spread of wing round- ing an arc of 60 feet radius. Since the outer side of the aeroplane must travel over a given distance in the same time that the inner side must travel a considerably shorter distance, gravitation must be opposed to centrif- ugal force in order that the turn may be effected with safety.

that the aeroplane has a spread of forty feet. The outer end of the machine must describe its large arc of sixty feet radius while the inner end is describing its small arc of twenty feet

MAKING A TURN 87

radius. Evidently the outer end must travel considerably faster than the inner.

As the speed of an aeroplane increases, its lifting power also increases. Hence the more rapidly moving outer end of an aeroplane will be subjected to a greater lifting effort than the slowly moving inner end, and hence the entire machine is canted at a more or less sharp angle on a turn. This natural canting or banking has its advantages. It counteracts the effects of centrifugal force, which are unavoidable in any rotary movement.

What centrifugal force means we see when a weight at the end of a cord is whirled around. If whirled fast enough, the weight will describe a circle, because the centrifugal force is very much greater than the force of gravitation. If the whirling be slackened below a certain criti- cal point, the weight will drop back to the hand. A flying-machine is like the whirling stone. It has a very large centrifugal force as it turns. So great is that force that it must be checked by the force of gravitation, in other words, the weight of the machine. The more the machine is heeled over, the more marked

88 THE NEW ART OF FLYING

will be the action of gravitation. Hence the natural canting of the machine on a curve is of advantage in counteracting the effect of centrif- ugal force.

If the canting be very pronounced, it is pos- sible that gravitation may overcome the centrif- ugal force, so that the machine will slide down to the ground. To forestall that possibility the aviator may either sweep his circle on so long a radius that there will be but little canting, or he may employ wing-warping devices or aile- rons to counterbalance the canting action. Since most aeroplanes are provided with either warp- ing devices or ailerons, it is the usual practice to depend upon them in turning. The result is that we see skilful pilots swinging in an arc at a speed that cants their machines at an angle which may be more than seventy degrees to the horizontal and which almost causes the specta- tor's heart to stop beating, so perilous does the exploit seem to the eye.

The inquiring reader may ask: How does wing-warping or the manipulation of ailerons prevent the machine from slipping down ? The principle involved is exactly the same as that

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MAKING A TURN 89

which underlies the balancing of the machine in straightaway flight when it is subjected to cap- sizing gusts. As soon as the pilot wheels, he in- creases the angle of incidence on the inner end and hence the upward pressure, with the result that the tendency of the inner end of the ma- chine to fall is checked. Simultaneously the angle of incidence of the outer side is decreased and the downward pressure increased, with the result that the .tendency of the outer side to rise is checked.

All this sounds very easy; yet, even after a successful aeroplane had been invented, many machines were wrecked before the trick of making a turn was learned. It took the French two years to learn the art of turning. Indeed, a wealthy Parisian, named Armengaud, offered a prize to the first Frenchman who performed the feat. Henry Farman won that prize so recently as July 6, 1908. The Wright Brothers spent the whole flying season of 1904 in learning how to sweep a circle when the wind was blowing. Octave Chanute, the only en- gineer who was allowed to see them at work during that period of apprenticeship, gives

9o THE NEW ART OF FLYING this interesting account of their trials and tribulations :

" I witnessed a flight at Dayton on October 15, 1904, of 1,377 feet> performed in twenty- four seconds. The start was made from level ground, and the machine swept over about one- quarter of a circle at a speed of thirty-nine miles an hour. The wind was blowing diag- onally to the starting rail at about sixteen miles an hour.

" After the machine had progressed some five hundred feet and then risen about fifteen feet it began to cant over to the left and as- sumed an oblique transverse inclination of fif- teen to twenty degrees. Had this occurred at an elevation of, say, one hundred feet above the ground, Orville Wright, who was in the machine on this occasion, could have recovered an even balance even with the rather imperfect arrangement for control at that time employed. But he felt himself unable to do so at the height then occupied and concluded to come down.

* This was done while still turning to the left, so that the machine was going with the wind instead of against it, as practiced where possible.

" The landing was made at a speed of forty- five to fifty miles an hour, one wing striking the

MAKING A TURN 91

ground in advance of the other, and a breakage occurred, which required one week for repairs. The operator was in no wise hurt.

" This was flight No. 71 of the 1904 series. On the preceding day the brothers had made alternately three circular flights, one of 4,001 feet, one of 4,902 feet, and one of 4,936 feet, the last covering rather more than a full circle.11

A steady wind is imperceptible to the man in a flying-machine, and turning is effected as easily with as against the wind. When the wind is unsteady not only is balancing difficult but turning also, since the machine must be simultaneously balanced and turned. The two operations are more or less confused. When the wind is very gusty the pilot may find it harder to turn and travel with the wind instead of against it.

A sharp turn on an aeroplane is like one of those moments on a yacht when you slack away quickly on the main sheet and prepare for the boom to jibe. There is none of the yacht's hesitancy, however; for the machine slides away on the new slant without a quiver. An inexperienced passenger on an aeroplane is

92 THE NEW ART OF FLYING

tempted to right the machine, as it swings around and tilts its wings, by throwing over his body toward the descending side. In a canoe or on a bicycle it would be natural to use the body. In an aeroplane the movement is un- necessary because the machine does its own banking.

In the Curtiss and Santos-Dumont machines any such instinctive movement on the part of the aviator to right the careening machine actu- ates the ailerons or wing-warping devices in the proper way. In the Curtiss biplane, as we have seen, the seat-back is pivoted and is con- nected by cables with the ailerons. Hence, should the pilot involuntarily throw his weight over to right the machine, the ailerons are tilted to regulate the pressure on the planes in the proper manner.

The effect of the vertical rudder in turning varies with the speed of the aeroplane relatively to the speed of the wind. The higher the speed of the aeroplane the more marked is the influence of the vertical rudder on its course.

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single vertical surface, mounted at the rear of, the machine: in biplanes it usually consists of a pair of parallel vertical surfaces, as in the Wright machine. Occasionally these parallel vertical surfaces form the sides of a box, as in the Voisin and Farman machines, the top and bottom of the box serving as horizontal stabilising surfaces, as in the old cellular Voisin biplane.

CHAPTER VII

THE PROPELLER

FEATHERING paddles, somewhat like those to be found on steamboats, beating wings, like those of a bird, sweeps or oars have all been suggested as means for propelling the flying- machine; but the screw propeller is the only device that has met with any success. The screw propeller is the most important adjunct of the aeroplane, and also the most deficient. The circumstance is remarkable because the screw or helical rotating propeller was associated with schemes of aerial navigation no less than four centuries ago, and by no less a personage than the great artist-mechanician, Leonardo da Vinci, at the end of the fifteenth century.

Leonardo da Vinci's propeller was a screw or helix of a single " worm " or thread — prac- tically all " worm " — comprising an entire convolution, of which the modern equivalent would be a single-bladed screw, blades being a much later development. It is not difficult

THE PROPELLER 95

to imagine how the original screw propeller came to be of the single " worm " type, and why one complete turn of the " worm " should be deemed essential. These were matters of subsequent development, the departures being suggested by experiment and trial.

It was first discovered by actual comparative trials that half a convolution of the " worm " was fully as efficient as a whole turn, and then that a quarter turn was more efficient than half. But with this curtailment of the helix a for- midable difficulty arose. It had now developed Into a one-bladed screw; it was unsymmetrical and, consequently, unbalanced. Centrifugal force and one-sided thrust jointly interposed, with poor results.

Eventually it dawned on the minds of the pioneer experimenters that to produce a more efficient, symmetrical, and compact screw pro- peller— while employing only a fraction of a convolution — two or more " worms," now reduced to blades, were necessary.

No perfect definition of a screw propeller has ever been given. It is usually defined as an organ which, by pressing upon a fluid, pro-

96 THE NEW ART OF FLYING

pels the vehicle to which it is attached. In a sense, the screw propeller may be regarded as a rotating aeroplane, with an angle of inci- dence, known as its " pitch," and a " camber," which is its curve. But the propeller differs from the aeroplane in that the blades are con- tinually passing over the same spot many times in a second in air already disturbed. This is one reason why the propeller offers a far more difficult problem than the plane.

By the " pitch " of a propeller is meant the theoretical distance that the propeller would move forward in one revolution in a solid. Because a propeller revolves in air, a very thin and yielding medium, it loses a certain amount of power, which loss is known as its " slip." If the propeller in one revolution moves forward theoretically six inches, but actu- ally only three inches, the loss of power or " slip " is fifty per cent. The slip varies with different speeds. To find the best pitch, the best curvature, the best diameter, the best speed, is the problem that confronts the propeller designer.

The ideal aerial propeller is one that can move through the air without friction. If the

THE PROPELLER 97

ideal could be attained, the entire power of the motor would be transformed into useful work, and a maximum thrust would be transmitted to the propeller shaft. The actual aerial propeller

FIG. 41. — A single-threaded and a double- threaded screw. A two-bladed aeroplane propeller may be conceived to have been cut from a double-threaded screw, i. e., the sections A and A' and the sections B and Br.

falls far short of that ideal. Its blades are not plane, but are curved in a manner skilfully de- signed to obtain a maximum efficiency. In order to give an idea of this curvature and its pos- sible variations, consider a vertical section of an Archimedes screw (Fig. 41), Let us study

98 THE NEW ART OF FLYING

the small slice, M. This small element is not a plane surface, but has a curvature which de- pends upon the pitch of the screw and its radius. Two such elements attached, opposite each other, to the same shaft represent a two-bladed propeller of definite curvature.

It is evident that this curvature cannot be a matter of indifference, for it is intimately con- nected with the distance A 5, between two points on the same generatrix of the screw; that is to say, upon the pitch of the screw. The form of a propeller blade can be imitated by holding one end of a rectangular strip of paper and twisting the other end about an axis parallel with the length of the strip. The Wrights form such a surface in deforming aeroplanes in steer- ing. If the aeroplane were attached to a fixed vertical axis, it would revolve about this axis like an ordinary propeller during a turn. The true screw-propeller in its simplest and most efficient type is but a very short length cut from a two-thread screw, in which the thread is rela- tively very deep, with a pitch equal to about two thirds of its diameter. A twist or curve in a propeller blade is necessary because the hub

THE PROPELLER 99

and the outer edge of the blade revolve at different speeds. The outer edge of the blade clearly must sweep through a greater distance in a given time than the hub. In order that all parts may theoretically grip the air equally, the angle is steeper at the centre than at the outer edge. In practice the hub portion has a much lower efficiency than the outer edge of the blade.

Just how many blades the propeller should have once gave us much concern. Some air- propellers have two blades, some three, some four. It is now generally conceded that nothing is to be gained by three and four blades, and that the two-bladed propeller is indeed the most efficient.

The Ericsson propeller (marine) was formed of a short section of a 12-thread screw of very coarse pitch and proved very ineffi- cient. The aerial fan propeller of Moy (not a screw) had six broad vanes enclosed in a hoop and was but little better. The same re- mark applies to the propellers of Henson, Stringfellow, Linfield, Du Temple, and many others. Even the first propeller fans used by

ioo THE NEW ART OF FLYING

Langley on his earliest aerial model were six- bladed. In his subsequent and highly success- ful model aerodrome the twin propellers were two-bladed true screws, as also were those of the Maxim machine.

It is a significant fact that the conspicuous successes have all been achieved with two- bladed propellers. All recent systematic and comparative experiment points to the fact that a two-bladed propeller is the most efficient, and, at the same time, fortunately, the simplest and lightest.

Authorities are not in accord on the proper position of the propeller. Most of them, how- ever, hold, with Sir Hiram Maxim, that the proper position is in the rear. Bleriot (Fig. 46), Levavasseur (who builds the Antoinette machine), and many monoplane designers mount the propeller in front. In its usual posi- tion just in advance of the centre, the front pro- peller interrupts the entering edge. To obviate this, some monoplane builders, among them Santos-Dumont and Bleriot (in his passenger- carrying monoplane XII), place the engine and pilot below the plane.

THE PROPELLER 101

On the position of the propeller Maxim says:

" Many experimenters have imagined that a screw is just as efficient placed in front of a machine as at the rear, and it is quite probable that in the early days of the steamship a similar state of things existed. For several years there were steamboats running on the Hudson River, New York, with screws at their bows instead of at their stern. Inventors of, and experi- menters with, flying-machines are not at all agreed by any means as to the best position for the screw. It would appear that many, having noticed that a horse-propelled carriage always has the horse attached to the front, and that their carriage is drawn instead of pushed, have come to the conclusion that in a flying-machine the screw ought, in the very nature of things, to be attached to the front of the machine, so as to draw it through the air. Railway trains have their propelling power in front, and why should it not be the same with flying-machines? But this is very bad reasoning. There is but one place for the screw, and that is in the imme- diate wake, and in the centre of the greatest atmospheric disturbance. ... If the screw is in front, the backwash strikes the machine and certainly has a decidedly retarding action. The

102 THE NEW ART OF FLYING

framework, motor, etc., offer a good deal of resistance to the passage of the air, and if the air has already had imparted to it a backward motion, the resistance is greatly increased."

When mounted in front, the screw draws the machine along. Hence the front propeller is sometimes called a " tractor screw." When the screw is mounted in the stern, as in a ship, it pushes the machine along (Fig. 48) and is then truly a propeller.

The question of position is not yet settled by any means. The propeller at the rear has a free discharge, but, on the other hand, its feed is disturbed. In front it has a clear feed, but is hampered in discharging, and also modifies the streams impinging on the supporting planes, as Maxim points out.

The number of the propellers is also a moot point. Kress, a well-known experimenter, be- lieved that there should be at least four pro- pellers, so attached that their shafts could be directed to different angles. Thus, he imag- ined, they could be employed to sustain the machine in the air without driving it forward. This is the helicopter or screw-flier principle,

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briefly considered in the chapter on flying- machine types.

The Wrights have always advocated the use of two propellers rotating in opposite direc- tions (Fig. 44). There is always the danger, however, that one propeller may break down and that the machine may be imperilled. In- deed, an accident of that kind occurred during the official tests of the Wright machine at Fort Myer, Virginia, in 1908. A propeller struck a loose guy-wire and broke. The biplane crashed to the ground. Orville Wright, the pilot, was painfully injured, and Lieutenant Selfridge, a passenger, was killed. It must be stated, however, that had the machine been higher, Mr. Wright would probably have glided down in safety.

Should propellers be of very small diameter and high speed, or of large diameter and low speed? Both systems have their advocates. We know something about the power of heavy gales; and when we consider that an aero- plane propeller is capable of producing a little cyclone, it is easy to conceive of its exerting sufficient force to drive a i,ooo-pound

io4 THE NEW ART OF FLYING

aeroplane at high velocity. Flying-machines have attained a speed of seventy miles an hour. In order to do this, the propellers must have turned fast enough to have produced a current of air considerably more than this veloc- ity, because the fluidity and elasticity of the air are sufficient to cause a considerable " slip " of the propellers, which reduces their efficiency to a large extent. Hence even the slowest of pro- pellers (the Wright) turns at the fairly high speed of four hundred revolutions a minute, while the swiftest turns at the rate of about fifteen hundred revolutions a minute, which is about the speed of an electric fan. A high- speed Chauviere propeller is a mere glittering disk of light about eight feet in diameter. The blades move so fast that it is possible to cast a shadow upon them; for the eye cannot per- ceive the interval which elapses before another blade has taken the place of that which has left a given spot. The phenomenon. is simply one of the persistence of retinal images ; but it serves to drive home the enormous speed of some aeroplane propellers.

It is generally believed that much better re-

THE PROPELLER 105

suits could be obtained by the use of propellers of fifteen or twenty feet diameter rotating slowly. But there are two disadvantages in- volved in this feature of construction, which make its adoption in the machines of the future rather doubtful. The first is the greatly added weight of so big a propeller; and the second, the difficulty of building a good chassis high enough to enable the propeller to clear the ground.

Like the marine turbine, the aerial engine runs too fast for the best propeller speeds. The Wright brothers overcame this difficulty by the somewhat unmechanical expedient of chain gearing, one chain being crossed. A French firm has utilised the half-time cam-shaft of the engine, suitably enlarged, to drive the propeller, thus getting a speed reduction of two to one, but the Bleriot, Antoinette, Farman, Voisin, and indeed most types continue to drive the propeller directly without reduction. It is probable that the direct drive will prevail, for any form of gearing, however simple, intro- duces an element of risk with doubtful benefits. At present there is scarcely any machine which

*io6 THE NEW ART OF FLYING

has the propeller well under control, so that it can be stopped and started and altered in speed, without stopping the motor. This is due, of course, to the weight of clutches, change-speed gears, etc. Probably some enterprising engi- neer may produce a suitable gear for this pur- pose before long.

In this outline we have used the word " effi- ciency." How is efficiency determined, may well be asked. The true efficiency of a pro- peller driving an aeroplane is the ratio between the work of propulsion and the energy con- sumed, the work of propulsion being the prod- uct of the travel of the aeroplane multiplied by the resistance opposed to its forward move- ment. The efficiency is measured at a fixed point by causing the propeller to revolve, with- out advancing or receding, and measuring the thrust produced, in the direction of the axis, by a given horse-power.

The conditions of the experiment are very different from those of rapid flight through the air, in which the friction between the air and the propeller is enormously increased; no ac- count is taken of the resistance opposed by the

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air to the forward movement of the aeroplane. In fact, no work of propulsion is performed or even imitated, the sole result being a thrust which may be employed for propulsion. Under these conditions the propeller is comparable with a lever which supports a motionless weight and thus exerts a stress, but performs no work. For this reason absolute reliance cannot be placed on the results of many propeller tests.

A fair imitation of the conditions of flight as they directly affect the propeller itself can be obtained by placing the propeller in a tube in which an air current of any desired velocity is produced by blowers. Some experimenters mount the propeller so that it revolves freely in air and yet drives a boat or a road vehicle.

Some of the best results obtained, in recent times, of thrust for horse-power applied are: Maxim, nine pounds; Langley, about seven pounds; Spencer (with a Maxim type pro- peller), six pounds; Farman, and other experi- menters in France, six pounds (about).

It is now a widely recognised fact that the aerial propellers at present in use are lament- ably inefficient. Most aeroplane successes, ex-

io8 THE NEW ART OF FLYING

cept those of the Wrights, are achieved at an enormous cost; for the propellers waste prob- ably more than half the power applied.

A propeller of large diameter and slow revo- lution is more efficient than one of small diam- eter and high speed, a circumstance borne out especially in the case of the Wright machine, in which more thrust is obtained per unit of power than in any other type (Fig. 43).

We are beginning to realise that the abuse lavished on the motor should be bestowed in very large measure on the propeller. The in- ternal-combustion engine fitted to the aero- plane must have all the vital parts cut to the narrowest margin, and must be worked at very nearly break-down rate in order to produce an enormous amount of surplus power wasted by the screw. For this reason all our more serious investigators are carrying out scientific experi- ments to determine propeller efficiency. Per- haps when they have completed their work we may be able to build a propeller which will drive a flying-machine with something like econ- omy of power.

The construction of the aerial propeller is

THE PROPELLER 109

the more delicate, because it depends to a large extent upon the peculiarities of the vessel to which it is to be attached. The methods em- ployed in all establishments are the same; yet a Chauviere propeller is very different from a Wright propeller.

FIG. 42. — How the Wright propeller is cut from three planks laid upon one another fan-wise.

A Wright propeller is made of American spruce and is of very light construction. The extremities of the blades are covered with canvas, which is varnished with the rest, for the purpose of increasing the rigidity of the thin outer ends. The whole propeller is built up of three planks arranged as shown in Fig. 42, so that they overlap like the sticks of a fan, to an extent which diminishes as the dis-

no THE NEW ART OF FLYING

tance from the hub increases. The superfluous parts of the wood, represented by the darker and triangular areas of the upper diagram in Fig. 42, are then cut away, and the curvature is tested at every point by patterns.

Chauviere propellers are made of ash, fumed oak, and walnut, and include six or seven over- lapping planks. The finished propeller contains only about eight and one half per cent of the wood of the original planks.

It should be added that constructors show little disposition to furnish exact details of their methods. Their industry is so new that they jealously guard their secrets, for which reti- cence they cannot be blamed.

Propellers are also made of metal. In these the blades are soldered or riveted to the arms, which are steel tubes riveted to the hub. The blades are shaped by hammering them upon a form. In some cases they are cast, or twisted into shape, but this construction is not so good.

CHAPTER VIII

AEROPLANE MOTORS

MARVEL as we may at the wonderful ingenuity displayed in the modern flying-machine, we have still much to learn from soaring birds. Little as we know of the efficiency of curved surfaces in the air, we know still less how to drive those surfaces without an inordinate expenditure of power, fuel, and lubricant. We have only to compare the amount of energy expended by the great flying creatures of the earth with that expended by our machines to realise how much we have to learn.

The late Professor Langley long ago pointed out that the greatest flying creature which the earth has ever known was probably the extinct pterodactyl. Its spread of wing was perhaps as much as twenty feet ; its wing surface was in the neighbourhood of twenty-five square feet; its weight was about thirty pounds. Yet this huge creature was driven at an expenditure of energy of probably less than 0.05 horse-power.

ii2 THE NEW ART OF FLYING

The condor, which is preeminently a soaring bird, has a stretch of wing that varies from nine to ten feet, a supporting area of nearly ten square feet, and a weight of seventeen pounds. Its approximate horse-power has been placed by Professor Langley at scarcely 0.05. The turkey-buzzard, with a stretch of wing of six feet, a supporting area of a little over five square feet, and a weight of five pounds, uses, according to Langley, about 0.015 horse-power. Langley's own successful, small, steam-driven model had a supporting area of fifty-four feet, and a weight of thirty pounds. Yet it required one and a half horse-power to drive it. How much power is required to fly at high speeds in machines may be gathered from the fact that although Bleriot crossed the Channel with a 25 horse-power Anzani motor, and the Wright machine uses a 25-30 horse-power motor, aero- planes usually have engines of 50 horse-power and upwards. When we consider that one horse-power is equal to the power of at least ten men, we see that even the smallest power successfully used in an aeroplane represents the combined continuous effort of more than two

AEROPLANE MOTORS 113

hundred men. To be sure, our flying-machines are very much larger than any flying creature that ever existed; but comparing their weights and supporting surfaces with the corresponding elements of a bird, their relative inefficiency be- comes immediately apparent. Mr. F. W. Lan- chester has expressed the hope that some day we may learn the bird's art of utilising the cur- rents and counter-currents of the air for propul- sion, so that we may ultimately fly without wasting power.

Aeroplanes are driven by what are known as " explosion engines " or " internal combustion engines." The fuel is not used externally, as in the steam-engine, but is fed to the engine in the form of an explosive gas. The gas is det- onated within the engine to drive a piston. Most of these internal combustion engines oper- ate on what is known as the Otto four cycle. A complete cycle comprises four distinct pe- riods, which are diagrammatically reproduced in the accompanying drawings (Figs. 49, 50, 51, and 52).

During the first period (illustrated in Fig. 49) the piston is driven forward, creating a

ii4 THE NEW ART OF FLYING vacuum in the cylinder and simultaneously draw- ing in a certain quantity of air and gas. During

FIG. 49-

FIG. 50.

FIG. 52.

FIGS. 49, 50, 51, -and 52. — The four periods of a four-cycle engine. During the first period (Fig. 49) the explosive mixture is drawn in; during the second period (Fig. 50) the explosive mixture is compressed; during the third period (Fig. 51) the mixture is exploded; and during the fourth period the products of combustion are dis- charged.

AEROPLANE MOTORS 115

the second period the piston returns to its initial position; all the admission and exhaust valves are closed; and the mixture of air and gas drawn in during the first period is compressed. The third period is the period of explosion. The piston having reached the end of its return stroke, the compressed mixture is ignited by an electric spark, and the resulting explosion drives the piston forward. During the fourth period the exploded gases are discharged; the piston returns a second time ; the exhaust valve opens ; and the products of combustion are discharged through the opened valve. These various cycles succeed one another, passing through the same phases in the same order.

The fuel employed in the internal combustion engines of aeroplanes is gasoline, called petrol in England, which is volatilised, so that it is sup- plied to the engine in the form of vapour. In order that it may explode, this vapour is mechan- ically mixed with a certain amount of air. To obtain what is called cyclic regularity and to carry the piston past dead centres, a heavy fly-wheel is employed, the momentum of which is sufficient to keep the piston in motion on the return stroke.

n6 THE NEW ART OF FLYING

Since considerable heat is developed by the incessant explosions, the cylinders naturally be- come hot. To cool them, water is circulated around them in a " water-jacket," or else a fan is used to blow air against them.

The memorable experiments of Professor Langley on the Potomac River gave rise to the idea that only an engine of extreme lightness could be employed if the flying-machine was ever to become a reality. Since his time bi- planes have lifted three and four passengers besides the pilot over short distances. While the ultimate achievement of dynamic flight was due to the lightness of the internal combustion motor in relation to the power developed, subse- quent experiment has demonstrated how the efficiency of the sustaining surfaces can be in- creased so as to diminish head resistance and to make extreme lightness in the motor desirable only on the score of freight-carrying capacity. The original motor used by the Wrights was comparatively heavy for the power developed.

Saving of weight in the motor permits the construction of a more compact and controllable machine than would be possible if the sustain-

Photograph by Edwin Levick

^y. — Gyrostat mounted in an aeroplane accord- ing to the system of A. J. Roberts. The gyrostat is controlled by a pendulum which swings to the right or to the left, according to the tilt of the aeroplane

AEROPLANE MOTORS 117

ing surfaces were designed to carry consider- able dead weight. To gain freight-carrying capacity the weight of the motor must be kept low. The fuel needed for a six-hour flight, for example, is equal in load to an engine weighing three pounds per brake horse-power, assuming that the hourly fuel consumption is one half a pound per horse-power. Clearly the motor must be light if the flight is to be long.

There are various ways of securing lightness in a motor. One way is to increase the power developed by cylinders of a certain size. An- other is to reduce the weight for a given cylin- der capacity by the use of thin steel cylinders and by constructing the parts as lightly as pos- sible. A third way is to arrange the cylinders in such a manner that more than one connect- ing-rod is assigned to each crank with a conse- quent reduction in the weight of the crank- case. A fourth way is to cool the cylinders with air instead of water.

Many motor builders have abandoned the fly-wheel because it is the heaviest part of the engine. In order that the motor may run steadily without a fly-wheel and may be prop-

n8 THE NEW ART OF FLYING

erly balanced, it has been necessary to rearrange the cylinders and to increase their number. The whole subject was recently considered by an anonymous writer in Engineering (London) . The following lucid paragraphs on the arrange-

FIG. 53. — The usual arrangement of the four cylinders of a four-cylinder engine.

ment of cylinders in present aeroplane motors present his views:

* The weight of an engine consists princi- pally of the cylinders and pistons on the one hand, and the crank, crank shaft, etc., on the other. Roughly speaking, the weight of the cylinders will be proportionate to the cube of the dimensions. That is to say, if the cylinders are arranged vertically in a row, for instance, the weight of the crank case, shaft, etc., will be practically proportionate to the cylinder ca-

AEROPLANE MOTORS 119

pacity. If we can mount the cylinders in such a manner that we can get a great cylinder ca- pacity with a very short crank case, we shall, however, save weight. If, for instance, we start with the vertical four-cylinder engine of the or- dinary type, as shown in Fig. 53, the crank case has necessarily to be as long as the length over the cylinders. In this and the following figures the valves are omitted for the sake of clearness, and in all the figures the cylinders are the same size, so that the size of crank case necessary for a given cylinder capacity can easily be seen.

'* Two common plans for reducing the length and weight of the crank case are to place the cylinders either diagonally, as in Figs. 54 and 55, or horizontally opposed, as in Fig. 56. In either of these arrangements the length of the crank case, etc., is almost halved, and a consid- erable saving of weight is effected. Any of these arrangements can be made with two, four, six, eight, or more cylinders. In the case of the diagonal engine the impulses are not evenly divided with two or four cylinders, though they can be so with six, if the angle between the cyl- inders be made one hundred and twenty degrees. With eight cylinders at ninety degrees the im- pulses are evenly divided, and this is the most usual number. In this type each diagonal pair of cylinders is connected with one crank. The

120 THE NEW ART OF FLYING

diagonal engine, with the cranks at ninety de- grees, can be balanced for all practical purposes, even where there are only two cylinders, by placing a balance weight opposite the crank

FIGS. 54 and 55. — Side and plan views of a four-cylinder engine with diagonally-placed cylinders.

equal to the weight of the whole rotating parts and the reciprocating parts of one cylinder. With four cylinders the cranks are usually placed opposite, but balance weights are still necessary to avoid a rocking moment. With eight cylinders the cranks are set so that the two

AEROPLANE MOTORS

end ones are opposite the two middle ones, and no balance weights are required.

" In the case of the opposed horizontal en- gine the two connecting rods work on opposed

FIG. 56

FIG. 57.

FIGS. 56 and 57. — Engine with horizontally opposed cylinders.

cranks, as in Fig. 57. In this case the engine, even the two-cylinder, is in many ways better balanced than the vertical or diagonal types, as the error in balancing, due to the angle of the connecting rods, is allowed for. If only two cylinders are used, there is, however, a very

122 THE NEW ART OF FLYING

small rocking moment, due to the fact that the cylinders are not actually opposite each other; but this is usually a negligible quantity. . . . With four cylinders the rocking moment is bal- anced. The impulses in the horizontal opposed engine are always evenly divided, whether two, four, or eight cylinders are used.

" Comparing the horizontal opposed with the diagonal engine, the former appears to have all the advantages, as the impulses are more even with a small number of cylinders, and the bal- ance better. The latter point will enable some- what shorter connecting rods to be used with- out excessive vibration, thus lightening the engine. . . .

'* While the crank case, etc., is distinctly lightened by these arrangements, it can be still more reduced if the cylinders are all arranged radially on to one crank. This has been done in. a great many different ways by different makers. For comparison, with the previously- mentioned four-cylinder engines, a four-cylinder radial engine is shown in Figs. 58 and 59, the cylinders being the same size as before. It will be seen that in this case the crank case and shaft are very much shorter and lighter than in any of the previous arrangements. In practice four is not a good number of cylinders, as the impulses cannot be evenly divided, and an odd number

AEROPLANE MOTORS 123

of cylinders must be used to effect this. This type of engine can be satisfactorily balanced as long as the cylinders are evenly spaced round the crank case, for all the pistons are attached

FIG. 58

FIGS. 58 and 59. — Engine with four cylinders radially arranged.

to one crank pin, and therefore form one revolv- ing weight, which can be balanced by a suitable balance weight.

' When many cylinders are used it is imprac- ticable actually to put all the connecting rods to work onto one crank pin, as either the big

124 THE NEW ART OF FLYING

ends would have to be very narrow, or the crank pin impracticably long. This can, however, be got over by the arrangement shown in Fig. 60.

" Probably the greatest difficulty in making the radial engine satisfactory is that of lubrica-

FIG. 60. — Arrangement of connecting-rods of an engine with four radial cylinders.

tion. This is a matter which does not seem to have had nearly as much attention paid to it as it needs. . . . The even distribution of the oil to the various cylinders of a radial engine is very difficult, and further, however well it might be managed when the engine is running, as soon as it stops the oil runs into the lower cylinders, and probably fouls the plugs, so that it is diffi-

AEROPLANE MOTORS 125

cult to start it again. In order to get over this, the engine has occasionally been mounted on its side, with the crank shaft vertical, the propeller being driven through bevel gear. If it is desired to run the propeller slower than the engine, there is no great objection to this, and there is little doubt that the slow-running propeller is much the more efficient. Another plan is to mod- ify the arrangement of the cylinders. Thus in

FIG. 61. — Arrangement of cylinders and crank case of one type of three-cylinder engine.

one make of three-cylinder engine the cylinders are all at the top of the crank case (Fig. 61), all the connecting rods leading to one crank pin. In this case it is impossible to divide the im- pulses evenly, and the balancing is not so good. In practice this type of engine is made with in- side fly-wheels of considerable weight, and runs well, but the fly-wheels necessarily add to the

126 THE NEW ART OF FLYING

weight. Another plan is to put all the cylinders at the top of the crank case, and to place those which should have been at the bottom in a com- plete radial engine on a crank opposite to the others, as shown in Fig. 62.

" In some cases the radial engine is made with the crank shaft fixed and the cylinders re- volving. As constructed by the Societe des Moteurs Gnome, this type (Fig. 46) has given very good results, but it may be doubted

FIG. 62. — Disposition of cylinders crank case and connect- ing-rods in one type of engine.

whether they are due simply to making the cyl- inders revolve. A very small amount of con- sideration will show that the radial engine will be of the same weight whether the cylinders re- volve or the crank shaft, all other details of construction being, of course, assumed to be the same. This being so, the only way in which

AEROPLANE MOTORS 127

the revolving cylinders can be an advantage is either by obtaining a lighter construction of cylinder or crank case, or else by increasing the power obtained from a given sized cylinder. There does not seem any reason for supposing that revolving the cylinders secures either of these results.

'* The advantages of the revolving cylinders are : ( i ) That they act as a fly-wheel, and ( 2 ) that they render air-cooling more efficient. Where the propeller is directly coupled, how- ever, no fly-wheel is required in any case. No doubt there is a distinct advantage in the air- cooling from the fact that the cylinders revolve, but it is not likely to be very great.

" Assuming that the ends of the cylinders are fifteen inches from the crank shaft, and the engine runs at twelve hundred revolutions per minute, the ends of the cylinders move through the air at about ninety-five miles an hour. When the engine with fixed cylinders is placed just behind the propeller, it probably always works in a current of air moving sixty miles an hour or more, so it will be seen that the differ- ence is not so great as might be expected. In practice the power given per cubic inch of cylin- der capacity by the Gnome engine is very small, and there seems no reason to doubt that the same power could be obtained from fixed cylin-

128 THE NEW ART OF FLYING

ders of smaller size. The good results appear to be due to the fact that the weight of the parts is reduced by machining practically all parts, in- cluding the cylinders and crank case, from steel forgings to such an extent that the engine weighs only 0.35 pounds per cubic inch of cyl- inder capacity. It seems probably that with fixed cylinders at least equally good results could be obtained if the same amount of trouble and money were spent."

The prime difficulty with the radial rotating engine shown in Fig. 46 is the lubrication, and until some means of reducing the consumption of lubricating oil is devised, the rotating cylin- der motor must have at least that compensat- ing defect. On occasions such as a flight from Chicago to New York for a prize the use of large quantities of lubricating oil may not mat- ter, but in an everyday motor for the aeroplane in the hands of the " chauffeur," or whatever his aerial equivalent may be called, the lubri- cation must be relied upon more than in the motor car; for while failure in the one case means only inconvenience, in the other it may entail disaster.

AEROPLANE MOTORS 129

The horse-power required for flight varies to a certain extent as the speed. Hence the factor that governs the maximum velocity of flight is the horse-power that can be developed on a given weight. At present the weight per horse- power of featherweight motors appears to range from two and one quarter up to seven pounds per brake horse-power. A few actual figures are given in the following list :

Antoinette 5 Ibs. per brake horse-power.

Fiat 3 " "

Gnome under 3 Ibs.

Metallurgic 8 Ibs.

Renault 7 "

Wright 6 "

Automobile engines, on the other hand, com- monly weigh 12 pounds to 13 pounds to the brake horse-power.

Because lightness and durability are oppo- site qualities, and because the more trustworthy a machine must be, the heavier must be its con- struction, it may well be inferred that the aero- plane motor is not a model either of durability or trustworthiness. The aeroplane builder ap-

130 THE NEW ART OF FLYING

pears, at present, willing to tolerate very little reliability, largely because the aeroplane is still in the hands of record-breakers and prize- winners, rather than of ordinary tourists. In making records the start takes place when the motor is ready. In a race it takes place at some determinate time, and if the motor be not ready, then the chance is lost. The record is also the result of frequent trials; a race is gained or lost in one. Thus, if one motor will make an aeroplane fly fifty miles whenever required and without unreasonable tuning up, but another makes it fly one hundred miles once out of ten attempts, the latter takes the record, though on its nine failures it may have broken down in a few miles, and may have required hours tuning up for each trial. If, however, the aeroplane is ever to be of the slightest practical use, the reliability of the engine must not only be brought up to that of the racing machine, but very much beyond it. This lack of reliability was strikingly evinced in the famous Circuit de I'Est of 1910, a circular cross-country race which started from Paris and finished there, and which included the towns of Troyes, Mezieres,

AEROPLANE MOTORS 131

Douai, and Amiens. The contest was remark- able because the airmen were expected to per- form what they had never attempted before. They had to fly over a given course on specified days without being able to choose weather con- ditions most favourable to them. Eight ma- chines started from Paris, but after the second day the only competitors left were Leblanc and Aubrun on their Bleriot monoplanes. The fail- ures of the others were due solely to engine troubles.

A resume of aeroplane motors compiled by Warren H. Miller is appended below in the concise form of a table of comparative costs and weights per horse-power based on the fifty horse-power size. It will be noticed that the Clement-Bayard is by far the heaviest, in spite of using aluminium for the case, thus adding to the already large amount of proof that for equal strength steel is always lighter than aluminium. The table also brings out the increased cost ne- cessitated by multiplication of cylinders, to ob- tain increased horse-powers at light weights. The Anzani, with only three cylinders, is by far the cheapest, but its weight is about midway be-

i32 THE NEW ART OF FLYING

tween the Clement and the Gnome, the lightest of them all.

TABLE OF FRENCH AVIATION MOTORS

Make H. P. Weight per h. p. Cost per h. p. Speed.

Antoinette ... 50 3 -84 Ibs. $48.00 ,200

Anzani 50 4.6 Ibs. 20.00 ,400

Gnome 50 3-3<5 Ibs. 52.00 ,200

E. N. V 40 3-85 Ibs. 37.50 ,500

Clement-Bayard 40 6.05 Ibs. 47.50 ,500

R. E. P 40 3.96 Ibs. 70.00 ,500

Wright 25 7-2 Ibs.

CHAPTER IX

THE NEW SCIENCE OF THE AIR

So far as the earth is concerned, the sun is very much in the position of a man who practically utilises only a single cent out of a fortune of $22,000,000 and throws the rest away; for only 1/2,200,000,000 of the sun's heat ever reaches us. That pittance must be conserved, for which reason the earth is wrapped in a wonderful, transparent, and invisible garment which we call the air and which serves the very utilitarian pur- pose of keeping the world warm. Of the thick- ness of that wrapping we know but little. Per- haps it may extend outward from the earth for a distance of two or three hundred miles if we may judge from observations of meteor trains and auroras. Some idea of its depth may be gained by stating that if this planet were a globe only six feet in diameter, the air would be not much more than two inches thick. The tex- ture of this gaseous garment and its peculiar relation to the sun have but recently been made

134 THE NEW ART OF FLYING the subject of rigorous investigation; for only in our own day has it been perceived that the vagaries of the weather may thus be satisfac- torily explained and a system of weather fore- casting devised more far-reaching and accurate than that which at present serves us.

One step in this investigation is the study of the physical attributes with which the air is en- dowed. The air has a weight which fluctuates from day to day and from hour to hour. It is sometimes warm and sometimes cold, sometimes moist and sometimes dry, sometimes calm and sometimes turbulent. All this our senses taught us long ago. But so crude are our senses that they can never tell us exactly how much it weighs at a given moment, how wet it is, how fast it moves, and how warm or cold it is. The physi- cist has, therefore, been constrained to devise subtler senses. He has given us a remarkable balance which is known to every one as a barom- eter and which weighs the air to a nicety; a del- icate measurer of moisture, which he calls a hygrometer ; a motion or wind recorder, known as an anemometer; and a heat-measurer in the form of the familiar thermometer. These re-

THE NEW SCIENCE OF THE AIR 135

sponsive artificial senses have been used on the surface of the earth for many years, and by their means are gathered the main facts upon the basis of which the weather bureaus at home and abroad venture to predict the mor- row's weather.

Because we have learned practically all there is to learn of the lower air and because weather forecasters have in the past ignored the upper levels of the air, levels which unquestionably have their influence on the weather, it was felt that some effort must be made to measure the thickness of the earth's invisible wrapping and to determine the weight, temperature, velocity, and moisture of the air miles above us.

In order to accomplish this task it was essen- tial to invent an artificial arm which would grasp the sensitive barometer, thermometer, hygrometer, and anemometer devised by the physicist and hold them for us in the upper reaches of the air. The problem of providing such an arm was not easily solved. In fact, it is not completely solved even now, for which reason the hand of science has not yet suc- ceeded in touching the uppermost layer of air

136 THE NEW ART OF FLYING

— the hem of the earth's mysterious robe. Meteorological observations with manned bal- loons have been made sporadically for much more than a century. An ascent was made by Jeffries, at London, in 1784, with a remarkably complete equipment of meteorological appara- tus. Hardly a year passes but that experiment is repeated. Because a human being cannot breathe the tenuous air of great altitudes and live, the experiment has sometimes proved fatal. To overcome the difficulty, the meteor- ologist has torn a leaf from the book of the marine biologist, who plumbs the deep sea with scientific instruments and brings to the surface living facts for subsequent study. The meteor- ologist, accordingly, now sounds the air, as if it were a great invisible ocean at the bottom of which we live.

The artificial arm that reaches upward has assumed the form either of a kite or of a small unmanned balloon, and thus it has become pos- sible to elevate to great heights the mechanical senses that weigh the air, feel its moisture and its heat, and note its motion. The men to whom most of the credit is due for all that has

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THE NEW SCIENCE OF THE AIR 137

been gleaned in the last few years are Teis- serenc de Bort, of France, Prof. A. Lawrence Rotch, of the United States, and Dr. Richard Assmann, of Germany.

During the past decade the work has been taken up by the official meteorological services of the world, and is now carried on systemati- cally under the direction of an international commission, appointed by the International Meteorological Committee. This commission has a permanent office at Strassburg, and holds triennial meetings in different cities, in which meteorologists from all civilised countries par- ticipate. The next meeting will take place at Vienna, in 1912.

In the United States, in addition to the ad- mirable work done at Blue Hill, by Professor Rotch and his staff, regular observations of the upper air are carried on by the Weather Bureau at the Mt. Weather Observatory, near Blue- mont, Va., and the data obtained are tele- graphed daily to Washington, for the informa- tion of the official weather-forecasters.

In Europe there are now several institutions devoted entirely to this branch of investiga-

138 THE NEW ART OF FLYING

tions. The most elaborate of these is the Royal Prussian Aeronautical Observatory at Linden- berg, not far from Berlin, and Germany has ob- servatories of similar character, on a somewhat smaller scale, at Hamburg, Aachen, Friedrichs- hafen, and elsewhere. The observatory at Friedrichshafen is unique in possessing a small steamboat which plies the waters of Lake Con- stance and is especially equipped for sending up kites and balloons. Other " aerological obser- vatories, " as the institutions of this character are now called, are situated at Trappes, near Paris ; Pavia, Italy; and Pavlovsk, Russia; while in the British Isles the chief centre for aerological observations is the Glossop Moor Observatory, near Manchester. Similar observatories exist in subtropical regions, in Egypt and India. A very important station is located on the peak of Teneriffe, in the Canary Islands. In the southern hemisphere upper-air researches are now regularly carried on at two places, viz., in Samoa; and at Cordoba, in the Argentine Republic. In addition to these fixed observa- tories, mention should be made of the aero- logical work now frequently carried out by ex-

THE NEW SCIENCE OF THE AIR 139

ploring expeditions, especially in the polar regions.

The scientific projection of the human mind to the upper atmosphere was not achieved merely by the invention of instruments and means for elevating them. Our eyes could not read the instruments when they were suspended in the air, and so it became necessary to make the artificial senses self-recording. Ingenious scientific artisans have provided the barometer, thermometer, hygrometer, and wing-gauge with clock-driven fingers that write a continuous, colourlessly impersonal, and therefore unbiassed story of atmospheric happenings at great heights, — a story which, to those who are versed in the hieroglyphic script in which it is written, gives a coherent account of the condi- tions that prevail at various elevations. The unselfish inventive genius which has been dis- played in devising these self-recording instru- ments would have been richly rewarded had it been applied to the needs of every-day life.

The lifting power of kites and balloons is limited, for which reason the instruments are made of feathery lightness and are ingeniously

i4o THE NEW ART OF FLYING

combined. The combination is generically known as a " meteorograph." Thus the ther- mometer and barometer are merged into a meteorograph specifically known as a " baro- thermograph," a contrivance which is provided with two automatic hands, one of which writes down the weight (pressure) of the air and the other its temperature. Sometimes the barom- eter, thermometer, and hygrometer are joined in a single instrument, which notes the humidity as well as the pressure and temperature. When the instruments return to the ground, their records inform the meteorologist of the height of the kite or balloon at any given minute during its ascent and of the temperature and barometric pressure at that particular minute. Because no ink has been found which will not freeze in the bitter cold of the upper air, the writing fingers of these instruments trace their story on smoked cylinders. At lower levels special inks and paper can be employed. Sam- ples of air have been collected by Teisserenc de Bort at heights which no human being can ever hope to reach, by devices that operate as if they were endowed with brains. To explain this

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remarkable feat, it may be stated that at a pre- determined altitude the barometer was made to complete an electric circuit (just as we push a bell-button), whereupon a little hammer fell and broke a closed, exhausted glass tube. Air rushed into the tube, and the glass was there- upon automatically sealed by a current which heated a platinum wire coiled around the broken end of the tube, thereby fusing the glass.

These are but a few of a long list of scien- tific inventions which might be cited and of which the world hears nothing. Meteorology has more than one unheralded Edison and Tesla, men who labour year after year in scien- tific obscurity, and who deem themselves richly rewarded if their instruments aid in the dis- covery of some new atmospheric phenomenon which may illumine the very dark subject of meteorology.

The elevation of these instruments by kites has probably been carried to the greatest per- fection by Prof. A. Lawrence Rotch, of the Blue Hill Meteorological Observatory at Hyde Park, Massachusetts. His exploration of the lower four miles of air is the most complete that has

I42 THE NEW ART OF FLYING

yet been made. The kites employed by him, and, for that matter, by most air explorers, are of the open box type, which every boy now flies in preference to the old-fashioned single- surface contrivance distinguished by its long tail of rags knotted together. For meteorological purposes, however, the box kite assumes dimen- sions that utterly dwarf its toy prototype. Some of the Blue Hill kites measure nine feet in length. Despite the great lifting capacity im- parted by its expansive surface, an air-exploring kite could not attain a considerable height if it were held only by hemp. A cord or rope would necessarily be so heavy and thick that a kite would be severely taxed in pulling it up. Hence it is the practice to employ fine piano-wire, which is both strong and light.

So powerful is the pull of a large kite that human muscles are hardly able to cope with it. An engine-driven winch is therefore utilised to haul in the long line. Devices are employed to register the pull of the kite and the length of the wire in use. Often it happens that as much as ten miles of line may be paid out. The elevation of the kite is determined in clear

THE NEW SCIENCE OF THE AIR 143

weather from data obtained by means of special optical instruments (theodolites) placed on the ground. At night and in hazy weather the meteorograph readings themselves must be depended upon.

Four miles may be considered the maximum height that a kite is capable of attaining. To explore the air above that limit and above the six miles that mark the end of human endurance in manned balloons, the " sounding-balloon " is employed, of which the most skilful use has been made by Teisserenc de Bort and by Dr. Richard Assmann.

The balloons are filled with hydrogen gas, which expands with increasing elevation. The degree of inflation therefore depends upon the height to be attained. Thus, if the balloon is to reach a point where the air is one half as dense as it is at the level of the sea, the gas- bag is half filled. If at the objective point the density of the air is one fourth the density at the level of the sea, the bag is filled only one fourth. Obviously, if very great heights are to be attained, heights where the air is exceed- ingly rare and thin, the balloon's capacity must

i44 THE NEW ART OF FLYING

be great and the construction wonderfully light. Paper balloons were, therefore, adopted by Teisserenc de Bort. Latterly, however, Ass- mann's India-rubber balloons, varying in diam- eter from three to five feet, have come into use, because they reach greater heights. At the maximum elevation of the balloon the expansion of the hydrogen gas is so powerful that the balloon bursts. Retarded in their fall by a para- chute, the instruments glide gently down to the ground. Instead of a parachute a slightly inflated auxiliary balloon may be employed which does not explode, and which has sufficient buoyancy to prevent a too rapid descent of the instruments and to indicate the position of the basket in a thicket or at sea. To the basket in which the instruments are contained a printed notice is attached which offers a reward for their return. More than ninety-five per cent of the sounding-balloons liberated find their way back to the observatories. Indeed, the zeal of the finder is sometimes such that he even takes the trouble to polish the smoked cylinder on which the records are traced.

Sounding-balloons reach astonishing eleva-

THE NEW SCIENCE OF THE AIR 145

tions and generally travel at railroad speed. Often they rise to heights of over fifteen miles

PROVISIONAL SELECTION OF DATES FOR INTERNATIONAL AEROLOGICAL OBSERVATIONS

(From "Wiener Luftschiffer Zeitung" Dec. I, 1909, with correc- tions subsequently announced by the International Commission for Scientific Aeronautics)

1910

1911

1912

1913

January

February

March

April

May

June

July

August

September

October

November

December

6

2-4 3

H 11-13

2

7 8-13

i

6 2-4

i

May 3i-June 2

6

3 4-9

5

9 6-8

3-S i

7 11-13

2

6

1-6 i

5 2-4

7 5

6

4 5-io

5

Is

4

2

5-7 4

In general, observations are made on the first Thursday of each month. Once a year observations on an especially extensive scale are made during six successive days; this is the so-called "International Week" and is the occasion of special aerological expeditions, in which the naval ves- sels of many countries participate. The month in which the International Week occurs varies from year to year. Shorter series of observations, covering three days, are made during other months — as shown in this table.

The results of the international observations are col- lected and published by the International Commission for Scientific Aeronautics, which has its headquarters at Strass- burg.

and cover distances of seven and eight hundred miles at the rate of forty to eighty miles an

i46 THE NEW ART OF FLYING

hour. A paper balloon will reach its greatest height in about six hours; a rubber balloon, in three hours.

Ascents with kites and sounding-balloons are regularly made on agreed dates by the air- exploring stations of the entire world. The dates noted in the table on page 145 were chosen for kite and balloon ascents for the years 1910 to 1913, inclusive.

As a result of many hundred flights made by kites and sounding-balloons by day and by night, in fair weather and foul, in spring and summer, in autumn and winter, over land and sea, in the tropics and within the arctic circle, we know that even in midsummer we live in a comparatively thin stratum of warm air. We know, too, that if we could transport ourselves to a height of ten miles and live in the bitter cold, thin air which would there surround us, we should find the aspect of the heavens won- derfully changed. The sky would no longer appear azure and suffused with light. By day as well as by night it would appear strangely black. Like brilliant points pricked in a sable canopy, the stars would shine both at noon and at mid-

THE NEW SCIENCE OF THE AIR 147

night. They would shine, moreover, not with the scintillation to which we are accustomed but with relentless steadiness. The sun would blaze

KV.

FIG. 68. — The extent of the atmosphere in a vertical direction. Heights in kilometres.

so fiercely in that cloudless sky of jet that the human skin would blister under its rays. So tenuous would be the air that it could not propa-

1 48 THE NEW ART OF FLYING

gate sound. I could not call to my friend and be heard, even though my hand touched his.

Much of this might have been guessed with- out the aid of the elaborate machinery that has been invented to explore the air. Much, how- ever, has been discovered that was undreamed of in our meteorology, — among other things, that the air is stratified above us in three more or less distinct layers.

The lowermost of these layers, the layer in which we live and which extends upward for about two miles from the surface of the earth, is a region of turmoil, warm to-day and cold to-morrow. This is the region of whimsical winds, of cyclones and anti-cyclones, of cool descending currents and warm ascending cur- rents. All our weather forecasting is at present based upon what can be learned from the gen- eral circulation of the air in this lowermost layer, the layer in which men navigate the air.

Beginning at the two-mile level that marks the end of the lowermost layer and extending upward for a distance of some five miles, we find a second stratum of air, — a stratum less capricious, and one in which the air grows

a a ,_

*fe ^ <U

'— ' O *"5

- 1 s •a* s.

V S c

c p o

1> O '^J

I « -I

rtls

M &

c ^ o

II: jj

f

o . "o

ifl

M <

'bio

THE NEW SCIENCE OF THE AIR 149

steadily colder and drier with increasing height. The lowest temperature thus far recorded is 152° below the Fahrenheit freezing point. Whatever thermal irregularities there may be are caused by wide temperature changes on the surface of the earth and by the reflection of solar heat by the clouds. Here the air moves in great planetary swirls, produced by the spin- ning of the earth on its axis, so that the wind always blows in the same eastward direction. The greater the height the more furious is the blast of this relentless gale.

Last of all comes a layer which was dis- covered by Teisserenc de Bort and Dr. Richard Assmann almost simultaneously, and which is generally called the " isothermal stratum " be- cause the temperature varies but little with alti- tude. The lower part of the isothermal layer shows a slight increase in temperature with increasing height. Hence this part of the iso- thermal layer is sometimes referred to as the " inversion layer," or region of the upper inversion.

Above the inversion layer the vertical tem- perature gradient is practically zero ; i. e., there

150 THE NEW ART OF FLYING

is little or no change of temperature with alti- tude. Teisserenc de Bort now calls the isother- mal layer " stratosphere," and the use of this latter name is increasing.

Although the air is warmer than in the layer immediately below, the temperature lies far below the Fahrenheit zero and may be placed somewhere near 100° below the Fahrenheit freezing point in middle latitudes. Here we have a region of meteorological anomalies which have not yet been satisfactorily explained. In passing from the second to the isothermal layer, the wild blasts of wind are stilled to a breeze, the velocity decreasing from twenty- five to eighty per cent. The air no longer whirls in a planetary circle. Indeed, the wind may blow in a direction quite different from that in the second layer. Whatever may be the moisture of the air below, it is always exces- sively dry in the permanent inversion layer. Just where this isothermal layer begins depends on the season, the latitude, the barometric pres- sure, and perhaps on other factors still unknown. Just where it ends no one knows; for although sounding balloons have risen to heights of over

THE NEW SCIENCE OF THE AIR 151

eighteen miles, its upper limit has not yet been discovered. In summer time the isothermal layer over middle latitudes begins at a height of about seven miles above the earth. We know that the higher it lies the colder it is, that the lower it lies the warmer it is. We know, too, that there is no bodily shifting up and down of warm and cold masses of air in that mysterious region. The result is that a current ascending from the lower level spreads out when it en- counters the " permanent-inversion " layer as if a solid barrier had been interposed.

Up to the height of the " permanent-inver- sion " layer the temperature falls at a rate which increases somewhat with altitude, but which may be placed roughly at rather over y2° C. per hundred metres (say i° F. per three hundred to four hundred feet), so that on a hot summer's day with a temperature of 90° Fahrenheit at the earth's surface, a man could place himself in fairly cool surroundings if he could rise only fifteen hundred feet. Because of the constant upheavals to which the air is subject in its lower levels, this average rate of temperature reduction, as we ascend, is not

iS2 THE NEW ART OF FLYING

often observed. It may even happen that for a short distance the thermometer may rise and not fall at all. Ultimately, the tempera- ture drops at a uniform rate until it reaches a point lower than that reported by any North- pole explorer.

To these fluctuating temperatures in the lowermost layer clouds and rain are due. Warm air tends to rise and to cool as it rises. The cooling air in turn condenses its water vapor into clouds. This process, as well as others that need not be considered here, leads ultimately to the precipitation of the condensed water of atmosphere, as rain, snow, or hail.

The three layers of air which have been dis- closed to us by the sensitive instruments of modern meteorology intermingle but slightly. The one floats upon the other as oil floats upon water. Of the great ocean of air at the bottom of which we move and live, three fourths by mass lie below the isothermal layer. All our storms, our clouds, and all dust, except such as may be of volcanic or cosmical origin, are phe- nomena of the lower two layers.

When the meteorologist has fully discovered

Photograph by Edwin Levick

Fig. 47. — The motor and the propeller of a R. E. P.

(Robert Esnault-Pelterie) monoplane. Robert

Esnalt-Pelterie has abandoned this four-

bladed metal propeller for the more

efficient two-bladed wooden propeller

THE NEW SCIENCE OF THE AIR 153

the influence which the upper region exerts upon the lower, there is reason to hope that he will be able to foretell the weather not merely a day but perhaps a week or more in advance, and to prepare charts which will be as useful to the aviator as the charts which warn the mariner of shoals and reefs.

The currents in the various levels of the atmosphere are of as much importance to the aviator as are the ocean currents to the mariner. Hence the necessity of charting the sea of air with scientific care, and hence the value of the work here outlined. The International Commis- sion for Scientific Aeronautics has already accu- mulated sufficient data to chart aerial routes, comparable with the ocean routes laid down by the various hydrographic officers of the world. Every government will have a special branch of research and will distribute infor- mation for aeronauts. The daily weather reports will be amplified to suit the flying man.

Thus far more interest has been shown in Europe than in this country in this matter of vital importance to the aeronaut. A detailed analysis of the wind data available for the

154 THE NEW ART OF FLYING

German Empire was undertaken by Dr. Richard Assmann at the instance of the " Motorluftschiff- Studiengesellschaft," founded by the Kaiser. That society, whose name translated into Eng- lish reads u Society for the Study of Motor Airships," recently published the results of Ass- mann. The Italian Aeronautical Society has performed a similar service for Italy. Such data will be useful to the aeronaut in selecting sites for practising grounds or for aerial har- bours, or in choosing the seasons most appro- priate for experiment.

Dr. Richard Assmann, director of the Royal Prussian Aeronautical Observatory of Linden- berg, in an article entitled " The Dangers of Aerial Navigation and the Means of Diminish- ing Them," contributed to the Deutsche Zeit- schrift fur Luftschifahrt, describes the aeronau- tical weather service that he is organising, and of which Lindenberg Observatory is to be the centre. According to Dr. Assmann at least three similar tentative schemes have already been put into execution in the German Empire. The first was undertaken by the Lindenberg Observatory in 1907, during trial trips made

THE NEW SCIENCE OF THE AIR 155

by the " Parseval " airship. Observations of the upper air currents were made simultaneously at five stations by means of pilot balloons and communicated to the crew of the airship, who were thus materially aided in guiding their craft. The second similar undertaking was Dr. Linke's special weather service for aero- nauts, conducted at the Frankfort Aeronautical Exposition of 1910. The third aeronautical service was organised by Dr. Polis, at Aachen. It is still in existence, and is intended especially for the benefit of the aero clubs of the Rhein- land. Its usefulness was demonstrated during the army manoeuvres in West Prussia in 1910.

Next to the United States, Germany has probably the best organised weather service in the world. It is therefore not astonishing that Germany should be better prepared than any other European state for the adaptation of modern meteorological science to the needs of the airman. Lindenberg Observatory is now equipping the Public Weather Service stations with the apparatus needed for daily observa- tions of the upper air, not primarily for the purpose of improving the weather forecasts,

1 56 THE NEW ART OF FLYING

but in order to lessen the dangers of aerial navigation, — dangers, in Assmann's opinion, largely avoidable and to which the loss of twenty valuable lives in Germany during 1910 may be attributed. At the present time the navigator of the air launches his craft with no more knowledge of the meteorological con- ditions in the upper air than can be surmised from those depicted in the ground-service weather map. The day is not far distant when he will have a weather map all his own.

In Dr. Assmann's plan, a number of the Public Weather Service stations are to be fur- nished by the Lindenberg Observatory with a theodolite, an inflating-balance for determining the ascensional force of the balloons, a sufficient number of balloons, and the necessary graphic tables for rapidly working up the observations.

At 8 A. M. every day, assuming the weather is favourable, the stations will be expected to send up a pilot balloon and to trace its course with the theodolite as long as possible. The observation will then be worked up — a matter of barely a quarter of an hour for a practised observer — and telegraphed to Lindenberg.

Photograph by Edwin Levick

Fig. 48. — Henry Farman seated in his biplane with three passengers

THE NEW SCIENCE OF THE AIR 157

Here the observations received from all other stations will be assembled and re-distributed in a single telegram sent to each of the cooperat- ing stations. If they arrive in time, the tele- grams can be utilised in connection with the ordinary daily weather forecast, as well as for the preparation of special forecasts and warn- ings for airmen. At Lindenberg the regular observation with a kite or capture balloon is made daily at 8 A. M., and in summer an ob- servation is also made about 5 or 6 A. M. Assmann also proposes to conduct daily ob- servations at Lindenberg with a pilot balloon at ii A. M., and, whenever necessary, another about 2 p. M., so that soundings of the air to an altitude of several miles will be made three or four times a day within a period of six to nine hours. Thus valuable information will be gathered which ought to enable the weather forecaster to warn airmen of impending changes in the lower atmosphere, on the basis of act- ually occurring rapid changes in the upper atmosphere.

That the German Public Weather Service stations will ultimately be supplemented with

158 THE NEW ART OF FLYING

stations especially erected for the purpose at the larger aviation fields and the like, would seem to follow from the work now done at the experimental observatory at Bitterfeld, from the erection of the aeronautical observa- tory on the Inselberg, near Gotha, from the probability of the erection of the long-promised aerological station at Taunus, and lastly, from the contemplated installation of aerological stations at nautical schools on the coast.

The difficulty of following pilot ballqons in hazy weather and at dusk leads Assmann to propose the utilisation of balloons of two sizes, the smaller and cheaper to be used when it is evident that the state of the sky will not per- mit the balloon to be followed with the the- odolite to a great distance. Observations at night could be made by illuminated balloons, but at considerable expense.

Undoubtedly there will be many days on which few, if any, observations can be secured with pilot balloons, so that only the observa- tions made at stations equipped with captive balloons and kites will be available. In order to meet this serious difficulty, Assmann is con-

THE NEW SCIENCE OF THE AIR 159

sidering the plan of supplying a few selected stations with a central and easily manageable kite outfit.

Thus far the plan outlined by Dr. Assmann has been approved only for a limited part of the Empire. Political heterogeneity still ham- pers imperial undertakings in Germany. Ulti- mately, however, the field of observations will be extended to include the south German states, where some very important stations are located, chief among which is the admirably equipped station at Friedrichshafen on Lake Constance.

Assmann himself realises that his plan can- not hope to provide detailed information and forecasts of local conditions except in so far as may be inferred from the general outlook. Some experiments which were recently made in Germany, after the appearance of Dr. Ass- mann's article, show that it is feasible to secure a corps of special thunderstorm observers who can report by telegraph and telephone, and who are numerous enough to enable the weather forecaster to follow the progress of sudden atmospheric disturbances across the country,

i6o THE NEW ART OF FLYING

and to give timely warning to the aeronaut to avoid them.

Apart from enlightening the aeronaut on the condition of the atmosphere, it will be obviously necessary to provide the equivalent of automo- bile road maps, — something that will tell the man of the air where he is. It is very difficult to recognise even familiar country from above. During his flight down the Hudson River, Cur- tiss decided to alight on what looked to him like a fine green field. Swooping down, he found that his green field was a terrace, an un- avoidable error in judgment which might have cut short his triumphal flight. With a map on a scale of half an inch to the mile, showing the lines of the roads and the shapes of the villages, it would seem easy enough to ascertain one's whereabouts; but the aviator travels quickly and a full equipment of half-inch maps would be a serious item in the weight of his load. The man in a balloon is often above clouds, and when he views the earth again it is very difficult and frequently impossible to pick up the route again. The aviator in a flying-ma- chine is more favourably placed. He knows his

Fig. 63. — Motor of the Wright biplane

THE NEW SCIENCE OF THE AIR 161

direction approximately, although he is often unable to make proper allowance for the drift- ing effect of the wind. If caught by varying currents or by storms above the clouds, he easily loses track of the course. There will be need of large distinctive ground marks for day and lights for night at distances of ten miles apart, marks which will correspond with those on an air-chart. Zeppelin proposes maps showing heights by colours, and marks indicating the influence of streams, marshes, and woods on the static equilibrium of the airship. The scale he suggests is three miles to the inch. Colour is the main consideration. In the opinion of Mr. Charles Cyril Turner, an English aero- naut, the colours should approximate to the colours of the landscape as seen from above. The roads should be white, the water blue, the fields light green, woods a darker green, habi- tations grey, and railways black.

Besides guiding the aerial traveller on his way some means must be devised of conveying useful information to him. It will often be of great importance to know the strength and exact direction of the wind. Skimming the air at the

1 62 THE NEW ART OF FLYING

rate of fifty miles an hour, the aviator will find it difficult if not impossible to make these obser- vations. The German Aerial Navy League has suggested that special light-houses be con- structed for that purpose. These are to send a long beam of light in the direction in which the wind is blowing. For day flights it will probably be necessary to have a long arrow painted white and swinging on a pivot so that it can be turned in the proper direction.

CHAPTER X

THE PERILS OF FLYING

FROM what has been said in the foregoing chapter it may well be inferred that a man who attempts to fly in the unsteady lower stratum of the atmosphere in which we live is almost in the same position as a drop of quicksilver on an exceedingly unsteady glass plate. Unlike the drop of quicksilver, however, he is provided with a more or less imperfect apparatus for maintaining a given course on the unsteady medium to which he trusts himself.

Were it not that the whirling maelstroms, the quiet pools, the billows and breakers of the great sea of air are invisible, the risks of flying would perhaps not be so great. Only the man in the air knows how turbulent is the atmosphere even at its calmest. " The wind as a whole," wrote Langley a decade ago, " is not a thing moving along all of a piece, like the water in the Gulf Stream. Far from it. The wind, when we come to study it, as we have to do

1 64 THE NEW ART OF FLYING

here, is found to be made of innumerable cur- rents and counter-currents which exist altogether and simultaneously in the gentlest breeze, which is in reality going fifty ways at once, although, as a whole, it may come from the east or the west; and if we could see it, it would be some- thing like seeing the rapids below Niagara, where there is an infinite variety of motion in the parts, although there is a common move- ment of the stream as a whole."

Through these invisible perils the airman must feel his way in the brightest sunshine, like a blind man groping his way in a strange room. He can tell you that against every cliff, every mountain side, every hedge, every stone wall, the air is dashed up in more or less tumultuous waves. The men who crossed the English Channel found that against the chalk cliffs of Dover a vast, invisible surf of air beats as furi- ously as the roaring, visible surf in the Channel below, — a surf of air that drove nearly all of them out of their course and imperilled their lives. There are whirlpools, too, near those cliffs of Dover, as Moisant used to tell. He was sucked down into one of them within two

THE PERILS OF FLYING 165

hundred feet of the sea. His machine lurched heavily, and it was with some difficulty that he managed to reascend to a height at which he could finish the crossing of the Channel.

Sometimes there are descending currents of air with very little horizontal motion, just as dangerous as the breakers. Into such mael- stroms the pilot may drop as into unseen quick- sands. On his historic flight down the Hudson River, Curtiss ran into such a pitfall, fell with vertiginous rapidity, and saved himself only by skilful handling of his biplane. A less experi- enced pilot would have dropped into the river. A sudden strong gust blowing with the machine would have a similar effect.

Such are the concentration of mind and the dexterity required by very long cross-country flights that a man's strength is often sapped. During the Circuit de I'Est of 1910, in which the contestants were compelled to fly regardless of the weather, the German, Lindpaintner, had to give up because of physical and nervous ex- haustion. Another competitor crawled under his machine, as soon as he alighted, and went

1 66 THE NEW ART OF FLYING

asleep. Wilbur Wright has been credited with the remark: " The more you know about the air, the fewer are the chances you are willing to take. It 's your ignorant man who is most reckless."

Because of the air's trickiness, starting and alighting are particularly difficult and dangerous. More aeroplanes are wrecked by novices in the effort to rise than from any other cause. As a general rule a new man tilts his elevating rudder too high, and because he has not power enough to ascend at a very steep angle, he slides back with a crash. In high winds even practised airmen find it hard to start. During the meeting at Havre in August, 1910, Leblanc and Morane were invited to luncheon at Trouville. Like true pilots of the air they decided to keep their engagements by travelling in their machines. At half past eleven they ordered their Bleriots trundled from their sheds. Twice they were dashed back by the wind before they succeeded in taking the air. An untried man would have wrecked his machine in that wind.

The pneumatic tired wheels on which a ma- chine runs in getting up preliminary speed serve

Photograph by Edwin Levick

Fig. 64. — Two-cylinder Anzani motor on a Letourd- Niepce monoplane

THE PERILS OF FLYING 167

also for alighting, as we have seen. When a monoplane glides down at the rate of forty- five miles an hour and strikes the ground, some disposition must be made of its energy. Usu- ally skids or runners, like those of a sled, are employed for that purpose, the bicycle wheels giving way under the action of springs, so as to permit the skids to arrest the machine. Men like the Wrights can bring an aeroplane to a stop without spilling a glass of water; but your unpractised hand often comes down with a shock that makes splinters of a high-priced biplane.

Inexperience in the correct manipulation of stabilising devices is a fruitful cause of acci- dents, — perhaps the most fruitful. The ma- nipulation of these corrective devices is no easy art. Machines and necks have been broken in the effort to acquire it. Man and aeroplane must become one. The horizontal rudder, which projects forward from many biplanes, is like the cane of a blind man. With it the pilot feels his way up or down, yet without touching anything. -Balancing from side to side is even more difficult. Curiously enough, it is when the

1 68 THE NEW ART OF FLYING

machine is near the ground that it is hardest of all to bring the aeroplane back to an even keel. Imagine yourself for the first time in your life seated in a biplane with a forty-foot span of wing, sailing along at the rate of thirty-five miles an hour, about ten feet from the ground. If your machine suddenly drops on one side, it will scrape on the ground before you can twist your planes and lift the falling side by increasing the air pressure beneath it. You will come down with a crash. If, on the other hand, you are an old air-dog, you will tilt up your hori- zontal or elevation rudder and glide up before you attempt to right yourself. So, too, if you see a stone wall or a hedge in your course, you will lift yourself high above it. Why? To avoid the waves of air dashed up against the wall or hedge. For if you did not rise, the waves would catch you and toss you about, and you might lose your aerial balance.

In this connection Prof. G. H. Bryan has pointed out that the distinction between equi- librium and stability should be kept in mind. An aeroplane is in equilibrium when travel- ling at a uniform rate in a straight line, or,

THE PERILS OF FLYING 169

again, when being steered round a horizontal arc of a circle. A badly balanced aeroplane would not be able to travel in a straight line. The mathematics of aeroplane equilibrium are probably very imperfectly understood by many interested in aviation, but they are compara- tively simple, while the theory of stability is of necessity much more difficult.

It is necessary for stability that if the aero- plane is not in equilibrium and moving uniformly it shall tend toward a condition of equilibrium. At the same time it may commence to oscillate, describing an undulating path, and if the oscil- lations increase in amplitude the motion will be unstable. It is necessary for stability that an oscillatory motion shall have a positive modulus of decay or coefficient of subsidence, and the calculation of this is an important feature of the investigation.

At the present time it is certain that aviators rely entirely on their own exertions for control- ling machines that 'are unstable, or at least deficient in stability, and they go so far as to declare that, owing to the danger of sudden gusts of wind, automatic stability is of little

1 70 THE NEW ART OF FLYING

importance. Moreover, even in the early exper- iments of Pilcher, it was found that a glider with too V-shaped wings, or with the centre of gravity too low down, is apt to pitch danger- ously in the same way that increasing the meta- centric height of a ship while increasing its " statical " stability causes it to pitch danger- ously. It thus becomes important to consider what is the effect of a sudden change of wind velocity on an aeroplane. If the aeroplane was previously in equilibrium, it will cease to be so, but will tend to assume a motion which will bring it into the new state of equilibrium con- sistently with the altered circumstances, provided that this new motion is stable. Thus an aero- plane of which every steady motion is stable within given limits will constantly tend to right itself if those limits are not exceeded. Exces- sive pitching or rolling results from • a short period of oscillation combined with a modulus of decay which is either negative (giving insta- bility) or of insufficient magnitude to produce the necessary damping.

More difficult than the maintenance of sta- bility is the making of a turn. The dangers that

THE PERILS OF FLYING 171

await the unskilled aviator who first tries to sweep a circle have been sufficiently dwelt upon in Chapter VI. The canting of a machine at a considerable angle, which is necessary in order that the weight of the machine may be op- posed to the centrifugal force generated in turning, necessarily implies that the aeroplane shall be at a height great enough to clear the ground. Yet many of the early experimenters wrecked their apparatus because they tried to make turns when too near the ground, with , the result that one wing would strike the turf and crumple up like paper.

Even at great heights the making of a turn is not unattended with danger, particularly when the machine is brought around suddenly. If a turn is made too abruptly, parts of the structure are sometimes strained to the breaking-point. There is good reason to believe that the Hon. C. S. Rolls was killed because he made too quick a turn.

Flying exhibitions, which tempt the prize- winning airmen to be overbold, are responsible for many of the tragedies that have occurred within the last few years. At the Reims meeting

172 THE NEW ART OF FLYING

of 1910, as many as eighteen machines were circling around one another, swooping down, hawklike, from great heights, or cutting figure- of-eight curves to the plaudits of an enthusi- astic multitude. It was not the possibility of collision that was so perilous, but the disturb- ance created in the air. The wake that every steamer leaves behind it has its counterpart in the wake that trails behind an aeroplane in the air. A rowboat may ride safely through the steamer's wake with much bobbing; an aero- plane caught in the wake of another pitches alarmingly. That was how the Baroness de la Roche met with such a terrible accident at the Reims meeting in question.

The various accidents which have occurred recently to aeroplanes raise the whole question of whether the construction of the wings is such as to give the requisite margin of safety to insure their not breaking under the loads which are likely to be thrown upon them in use. In all ordinary construction, as in building a steam- boat or a house, engineers have what they call a factor of safety. An iron column, for instance, will be made strong enough to hold five or ten

THE PERILS OF FLYING 173

times the weight that is ever going to be put upon it, but if we try anything of the kind in flying-machines the resultant structure will be too heavy to fly. Everything in the work must be so light as to be on the edge of disaster. Some of the worst accidents on record are to be attributed to this necessarily flimsy construc- tion. It is, of course, very difficult in the case of aeroplane accidents to ascertain which part broke first, for the fabric is generally so utterly destroyed that no details of the first breakage can be seen. Further, the aviator, who is the only man who can tell accurately what happened, is frequently killed, so that the only information available is what can be seen of the fall while the machine is in the air, and accidents occur so suddenly that different people do not always get the same impression of the sequence of events. There seems, however, little doubt that in several cases the wings collapsed in some way while the machine was flying, and that it fell in consequence.

In the case of a biplane (Fig. 69) the framing of the main wings usually consists of four longi- tudinals running the whole span of the wings,

i74 THE NEW ART OF FLYING

and these are braced together, both vertically and horizontally, with numerous cross-struts and wire diagonals, so as to give them very great strength, both vertically and horizontally. In fact, if the stresses of the diagonal wires be worked out, they are found to be very much below those usual in ordinary engineering work. Still, the wires are so numerous that, even if one of them breaks from vibration, the extra stress thrown on the adjacent ones will not bring the load up to the ordinary stresses allowed in girder work. The horizontal strength is also practically equal to the vertical, as the trussing is generally of the same character.

In the monoplane the trussing is much simpler. Often there is no horizontal trussing at all. The vertical strength of the main plane is entirely dependent on stays, generally four to each side, which go to the bottom of a strut under the backbone. Should one of these break, the probability is that the wing will collapse with disastrous results. These stays are often single parts of steel wire or ribbon, a material which has not been found sufficiently reliable for use as supports to the masts of small sailing

Photograph by George Brayton

Fig. 66. — Sending up the first of a pair of tandem kites at the Blue Hill Observatory

THE PERILS OF FLYING 175

boats, where wire rope is always preferred, on account of the warning it gives before breakage.

The structure of each wing in a monoplane is, in fact, very much like that of the mast and rigging of a sailing boat, the main spars taking the place of the mast, while the wire stays take that of the shrouds. A very important differ- ence, however, is that the mast of a sailing boat is almost invariably provided with a fore- stay to take the longitudinal pressure when going head to wind, while the wing of an ae'ro- r : me, as we have already noted, often has no such provision, the longitudinal pressure due to the air resistance being taken entirely by the spar.

When a monoplane is flitting through the air at the rate of sixty miles an hour, the wire stays often vibrate so fast that they emit a distinct musical note. The small boy who wants to break a piece of wire simply bends it back and forth many times at a given point. Rapid vibration of wires and ribbons on monoplanes will ultimately produce the same result. For safety's sake either wire rope should be used (heavier and therefore undesirable from the

176 THE NEW ART OF FLYING

record-breaker's standpoint), or the number of stays must be increased so that the parting of one will not necessarily spell a wreck and pos- sibly death.

The horizontal stresses thrown on the single supporting surface of an aeroplane are greater than most pilots realise. In one of those breath- less downward swoops which almost bring your heart to your throat, or in one of those quick turns in which the machine seems to stand on end, the stresses are enormously increased. It was the breaking of a wing by overstrain that killed Delagrange at Pau on January 4, 1910; it was overstrain that killed Wachter at Reims on July i, 1910; it was overstrain, due to sharp turning, that killed Rolls on July 12, 1910, at Bournemouth, England; and it was probably overstrain that weakened the wings of Chavez's monoplane in its battle with the Alpine winds and resulted in the fatal accident that occasioned the intrepid Peruvian's death on September 27, 1910.

In commenting upon the lack of horizontal strength in monoplanes, a writer in Engineering observe? ;

THE PERILS OF FLYING 177

" It is, no doubt, assumed that the weight of the machine rests on the wings, and that this is the main stress to be provided for. This is no doubt true, but a careful consideration of the horizontal stresses will show that these are much greater than might at first sight appear. When flying horizontally the horizontal stress cannot, of course, exceed the thrust of the pro- peller, and must in practice be considerably less than this, as part of that thrust is spent in over- coming the resistance of the body of the ma- chine, the tail, etc. The ratio of lifting power to horizontal stress will vary considerably in different machines with the efficiency of the planes, but even with the machine flying hori- zontally the horizontal stress will probably be in the neighbourhood of ten per cent of the vertical.

" It appears, however, that there are circum- stances in which the horizontal stress may be very much greater than this, for it increases with the speed of the aeroplane through the air, and this may be very much greater when descending than when flying level. The wings contribute the greater part of the air resistance, and there- fore, if the aeroplane is descending, it will accel- erate till the horizontal stress on the wings balances the acceleration due to gravity. Thus, if the aeroplane descends at a slope of one in

178 THE NEW ART OF FLYING

five, the horizontal pressure on the planes may be approximately twenty per cent of the weight of the machine. If the engine is kept running, it will be more than this by the amount of the propeller thrust. It is quite clear, therefore, that circumstances might arise in which the hori- zontal stress would be some twenty-five per cent of the vertical.

" Now, if we examine the framework of many of the monoplanes, we find that the horizontal strength of the wings is nothing like twenty-five per cent of the vertical; in fact, it is often prob- ably under five per cent. The framework of the wing consists of two longitudinals, and nu- merous cross-battens carrying the fabric. The longitudinals are the only part fixed to the back- bone, and therefore take practically the whole stress. These longitudinals are generally made very deep in proportion to their height, and are often channelled on the sides to make them into I-section girders. It is obvious, therefore, that their horizontal strength is very small indeed compared with the vertical. True, the numer- ous cross-battens stiffen the wing perceptibly, but the extent to which this is the case can hardly be calculated; and as they are often only about 24 inch by % incn» and fastened with very small nails, they cannot be relied on to any great extent. It seems, therefore, that either the

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wings should have diagonal bracing or should have stays in front corresponding to those down below."

That the question of speed in descent is a matter for which provision should be made is shown by the fatal death of Wachter at Reims in 1910. The speed in descending is higher than when flying level. In some cases the hori- zontal strength of the wings appears to pro- vide a very small margin for this increased stress, and the accidents seem to have happened exactly as suggested, for in each case, when rapidly descending from a height, the wing collapsed.

It may be said that when descending the en- gine ought to be stopped and the descent made at a speed not exceeding that which can be maintained on the level. Still, it is hardly prac- ticable to adhere to any such principle; for in alighting it is necessary to travel at top speed to clear the ground eddies. Moreover, if the aeroplane is to be of any practical use, it must be made to stand any reasonable usage to which it is likely to be subjected. Bicycles and motor- cars are often run down hill, or before a wind,

i8o THE NEW ART OF FLYING

at speeds far higher than can be maintained on the flat, and it is quite certain that a machine which is unsafe under these circumstances is not fit for ordinary work. Most men run down a hill as fast as they can without losing control of their cars, and aviators will doubtless do the same. The machine must, therefore, be made to stand the stresses set up under these conditions.

Very little is known of the air's power of breaking aeroplanes travelling at high speeds. Designers work from tables that indicate the breaking strength of wire and wood and the percussive force of the wind at different veloci- ties. But the actual buffeting to which a ma- chine is subjected in the air is still an engineer- ing uncertainty. A storm will tear the roof from a house and toss it a hundred yards ; yet aeroplane designers require a machine to travel through the air at hurricane speed and bear up under the sledge-hammer blows of the air, — a machine that is the flimsiest vehicle in which man has risked his life, composed, as it is, of fragile wires, the lightest wood cut as finely as possible, and fabric that is affected by varia- tions in the weather.

THE PERILS OF FLYING 181

In some of the tragedies of the flying-machine the propeller and the motor have each played their part. Lieutenant Selfridge's death at Fort Myer on August 17, 1908, was due to the snap- ping of a propeller blade, which struck a loose wire, an accident that for months crippled Orville Wright, who was piloting the machine. This, of course, was not due to any inherent defect in the propeller. Indeed, the Wright propellers, because of their low speed (four hundred to five hundred revolutions a minute), are probably the safest in use. The propellers of most monoplanes and biplanes travel at speeds as high as fifteen hundred revolutions a minute, or about as fast as an electric fan. Propellers mean more to an aeroplane than stout axles on an automobile; for if a flying- machine stops it must glide down. Nearly every contestant at a flying-machine meeting is equipped with spare propellers, which are as near alike as brains and hands can make them. Yet the same engine will not be able to turn two propellers seemingly alike at the same speed. Why? Because man can make steel, but he cannot make wood. That is grown

1 82 THE NEW ART OF FLYING

by nature. And because woods from different trees are not alike the propellers formed from them are not alike. Untraceable and insur- mountable variations create the differences. In aeroplaning science success or failure de- pends on just such slight differences.

The propeller's mechanical cousin, the motor, is also not what it ought to be. At very great heights it is impossible to obtain adequately high compressions in the motor cylinders. Hence the motor stops, and the aviator must glide down, — vol plane, as the French call it. Such glides can be made with comparative safety if the pilot is skilful. Occasionally it happens that motor stoppages have been the cause of death. It was the stopping of his motor that killed Leblon at San Sebastian on April 2, 1910, and Van Maasdysk at Amster- dam on August 22, 1910.

To prevent such accidents, Mr. Edwin Gould in 1910 offered through the Scientific American a prize of $15,000 to the designer and demon- strator of a successful machine equipped with more than one motor, the arrangement being either such that should one motor be disabled

Fig. 69.— A glimpse through a Wright biplane. The two planes are trussed together like the corre- sponding members of a bridge, so as to obtain great strength

THE PERILS OF FLYING 183

another can be immediately thrown into gear, or that if all the motors should be running si- multaneously the stoppage of one will not nec- essarily leave the apparatus without power. The progress which has been made since the Wright Brothers gave us the first success- ful man-carrying motor-driven aeroplane can hardly be called scientific progress. Much of it has been progress of the trial and error vari- ety, very costly and not always productive of valuable results. It may be retorted that, de- spite the highly scientific experiments of Langley and Maxim, we really owe the successful ma- chine to such men as the Wright Brothers, who are not profound mathematicians but skilful, practical mechanics. If the whole truth were known about the years of patient experiment- ing which finally led the Wright Brothers to the invention of a successful flying-machine, it would probably be discovered that they were no less scientific in their methods than was Langley himself.

The problem of building a flying-machine is in quite a different position from what it was. If flying-machines are not to be subjected to

1 84 THE NEW ART OF FLYING

frequent accidents and are to be made acces- sible to the million, the sooner aeronauts learn engineering the better. Not until engineers are employed to design and build flying-machines shall we be able to skim the air as safely as we now roll along the ground in motor-cars.

CHAPTER XI

THE FLYING-MACHINE IN WAR

UNLIKE any battle that has ever been fought in the world's history, the battle of the future will be a conflict waged in three dimensions. Long before its artillery will have volleyed and thundered, each great military power will have endeavoured to secure the command of the air by building more dirigible airships and aeroplanes than its rivals. The fighting arm of a nation will henceforth be extended not merely over land and sea, but upward into the hitherto unconquerable air itself. Of all this we had some indication during the remarkable French military manoeuvres of 1910. Then for the first time aeroplanes were tested under condi- tions that approximated those of actual warfare. To the laymen the aeroplane's chief function in this battle of the future would seem to be the dropping of explosives on a hapless and helpless army below. The military strategist knows better. In the first place he knows that

1 86 THE NEW ART OF FLYING

the actual amount of damage which could thus be inflicted would be disappointingly small. A hole may be torn in the ground; the windows of a few buildings may be broken; a battle- ship's superstructure may be blown away; but that wholesale destruction of life and property which would seem obviously to follow from the mere existence of military flying-machines, freighted with bombs and grenades, is not to be looked for. Even were it possible thus to destroy part of a stronghold, the difficulty of hitting the object aimed at is nearly insur- mountable. Every small boy has attempted to hit some passer-by in the street with a missile hurled from a third-story window. Usually he failed, because the target was moving and because the wind deflected the projectile. The air-marksman is much worse off. Seated in a craft which is not only skimming at a speed hardly less than thirty-five miles an hour and possibly as great as eighty miles an hour, but skimming at a height of perhaps half a mile, the chance that he will ever be able to hit his target by making the proper allowance for the horizontal momentum which his bomb would

THE FLYING-MACHINE IN WAR 187

receive, as well as for the prevailing wind, seems wofully remote. If bombs are to be dropped on forces below, it must be by means of tubes which will both project and direct the missile and which will be provided with wind gauges and height indicators for the proper guidance of the marksman. We must not allow ourselves to be misled by the skill displayed at flying exhibitions in dropping oranges on mini- ature battleships. Oranges are not bombs, nor are the heights at which they are dropped the half mile at which a military aeroplane must soar if it is to elude gun-fire.

Nevertheless some such possibility may have been at the bottom of the declaration signed by the delegates of the United States to the Second International Peace Conference held at The Hague in 1907, — a declaration which prohibited the discharge of projectiles and ex- plosives from the air. The declaration reads:

" The contracting powers agree to prohibit, for a period extending to the close of the Third Peace Conference, the discharge of projectiles and explosives from balloons or by other new methods of a similar nature."

1 88 THE NEW ART OF FLYING

The countries which did not sign the decla- ration forbidding the launching of projectiles and explosives from air-craft were: Germany, Austria-Hungary, China, Denmark, Ecuador, Spain, France, Great Britain, Guatemala, Italy, Japan, Mexico, Montenegro, Nicaragua, Para- guay, Roumania, Russia, Servia, Sweden, Switzerland, Turkey, Venezuela.

To be effective, a bomb must be fairly large. Moreover, a considerable supply of bombs must be available. The aeroplane is a thing of com- parative lightness. It cannot carry much am- munition of that sort. Hence, even admitting the possibility of dropping explosives upon any desired spot, the destruction wrought must nec- essarily be limited in extent. Lastly, there is also considerable danger in unbalancing the machine, by the sudden removal of the load from one side.

During the French manoeuvres of 1910 no attempt seems to have been made to drop explosives from either airships or aeroplanes, an omission which implies the ineffective- ness of that mode of attack. In the war of the future the aeroplane will be employed

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primarily for the transmission of orders and despatches; for discovering an enemy in a region in which his presence is suspected, his strength and the disposition of his forces being unknown; for ascertaining the strength of an enemy at points where he is known to be lo- cated; and for collecting sufficient information to permit siege guns to plant their shells where they will be most effective. In other words, the future military aeroplane will do the work of a scouting force; for its chief function will be that of reconnaissance. Two men will be seated in its frame, one to pilot the machine, and one to sketch and photograph the terrane below. From the trained eye of the spy in the air nothing will be concealed. He will be like a vulture wheeling in the blue, watching for carrion below. The click of his camera-shutter may be a death-knell, for it will record instan- taneously the position of some battery cun- ningly hidden behind a ridge, an earthwork thrown up across a pass, a stream spanned by military pontoon bridges. His pencil, when it touches the page of a notebook, may spell the death sentence of a regiment; for it will un-

1 9o THE NEW ART OF FLYING

erringly note those details of position and num- bers which the photographic plate may not be able to register. When he has learned all that he can learn, he signals his companion to re- turn. Hardly two hours may have elapsed since he was despatched on his quest. Yet within that time he may be able to give his command- ing officer information that a regiment of cav- alry could not have gathered with almost unlim- ited time.

Both Generals Picquart and Meunier, the opposing commanders during the French ma- noeuvres of 1910, expressed their satisfaction with the performance of aerial scouts. The machines were sent up practically whenever they were ordered to do so. What is more, the aviators carried out orders to the letter, and often under very unfavourable weather condi- tions. It was doubted at first whether they would be able to report with any degree of definiteness upon the position and number of the enemy. At a height of fifteen hundred feet, it seems quite possible, however, for a prac- tised man to discover the character of the troops below him and to ascertain whether they

THE FLYING-MACHINE IN WAR 191

are infantry, cavalry, or artillery. Artillery is easily enough distinguished by the intervals be- tween the horses. By counting the number of gun caissons the strength of the battery can be ascertained. The strength of cavalry and in- fantry is arrived at by counting the companies or other group formations.

During the manoeuvres in question it was sometimes difficult at the first glance to gain definite information of troops in battle forma- tion, and at times it was possible to distinguish friend from foe only by the direction of fire. Lieutenant Sido, a French army officer and aerial scout, in commenting upon the possibility of discovering at a very great height the posi- tion of an enemy's forces, stated that a man who goes up in an aeroplane for the first time cannot distinguish anything below him; that many flights are necessary before he can form a judgment of the terrane below; that good eyesight, coupled with experience, are neces- sary; that field glasses are needed only rarely; and that at a very great height cavalry is some- what harder to make out than artillery.

Although aeroplanes carrying but a single

i92 THE NEW ART OF FLYING

man did much valuable work during the ma- noeuvres, it is generally agreed that the military aeroplane must carry at least two men, one of whom shall act as a pilot, and the other as an observer. As the field of the military aero- plane is extended, it is very likely that non- commissioned officers, and even ordinary sol- diers, will be entrusted with the piloting of the machine. The observer must always be an in- telligence officer of experience. Lieutenant (now Captain) Bellenger, who distinguished himself by his effective reconnaissances in a Bleriot, maintains that one man will answer for ordinary scouting. When it is considered, however, that the machine is to be controlled, that maps are to be read, that the enemy's strength and disposition are to be discovered, that notes and sketches are to be made, it seems obvious that more than one man will be required.

It may be doubted whether the aeroplane will entirely supplant the usual forces employed for reconnaissance. The mist which usually conceals the ground early in the morning will probably interfere seriously with the activities

Photograph by Edwin Levick

Fig. 71. — A biplane that came to grief because of defective lateral control

THE FLYING-MACHINE IN WAR 193

of the aerial scout, not to mention ordinary fogs. Night marches and cavalry raids will probably be necessary as they have been in the past, and troops will mask themselves as they always have by natural and artificial concealments.

No doubt new stratagems will be devised to deceive the aerial eye. It is conceivable that a regiment may group itself in battalion or even brigade form, so that its strength may be over- estimated. Other stratagems suggest them- selves, such as the feigned movements which completely misled the observers in dirigible airships during the German army-manoeuvres of 1910.

It is highly advisable that the aeroplane be fitted, if possible, with some form of wireless telegraph apparatus, so that the commanding officer may be kept fully informed of each new discovery. The necessity of reporting in per- son means the return of the aeroplane to head- quarters. Up to the present time, no very successful attempt has been made in this direc- tion, although the success of the wireless instal- lation on the dirigible " Clement-Bayard II "

i94 THE NEW ART OF FLYING

would seem to indicate that the problem is not beyond solution.

For ordinary reconnaissance on the battle- field elaborate notes are not essential. The notes that Captain Bellenger took were of the most meagre character, — simply sufficient to refresh his memory. They were mere mem- oranda which read, for example, " 7 h. 47 m. Mortvillers, 3 batteries." Such a note was all that he required when making his oral report to refresh his memory. For siege work, on the other hand, Bellenger insists on much more detailed information. In reconnoitring of that character the chief work to be performed by the man in the air will be the precise indica- tion of the point to be shelled. An error of only one hundred and fifty feet in giving that position may nullify the besieging commander's best efforts. Reconnaissances in force to as- certain the enemy's disposition, a tactical neces- sity which may require a detachment of sev- eral thousand men from the main army for a considerable period of time will probably be of infrequent occurrence in the future war- fare. An aeroplane will accomplish the same

THE FLYING-MACHINE IN WAR 195

result in a fraction of the time. One of the bloodiest encounters the world has ever seen was the Japanese attack on " 203 Meter Hill." Yet the sole purpose of that great slaughter was the placing of two or three men at the summit of the hill to direct the fire of the Japanese siege guns upon the Russian fleet in the harbour of Port Arthur.

Major G. O. Squier of the United States Signal Corps has pointed out that the realisa- tion of aerial navigation for military purposes brings forward new questions as regards the limitation of frontiers. As long as military operations are confined to the surface of the earth, it has been the custom to protect the geographical limits of a country by ample preparations in time of peace, such as a line of fortresses properly garrisoned. At the out- break of war these boundaries represent real and definite limits to military operations. Ex- cursions into the enemy's territory usually re- quire the backing of a strong military force. Under the new conditions, however, these geo- graphic boundaries no longer offer the same definite limits to military movements. With a

196 THE NEW ART OF FLYING

third dimension added to the theatre of opera- tions, it will be possible to pass over this boun- dary on rapid raids for obtaining information, accomplishing demolitions, etc., returning to safety in a minimum time. Major Squier, therefore, regards the advent of military scouts of the air as, in a measure, obliterating pres- ent national frontiers in conducting military operations.

Is the enemy altogether defenceless? Can he offer no resistance? It is inconceivable that he shall lie at the mercy of a great artificial vulture, as helpless as a carcass. Undoubtedly he will have his special artillery, — field pieces so constructed that they can be elevated for high angle fire. Against that military bird of prey which he sees hovering far above him and whose errand he divines only too well, he will train this weapon. If his whistling shrapnel should strike a motor, a propeller blade, or an ignition device, if it should cut a tiller rope or splinter a steering rod, that great bird above him must glide down, wounded at least. It is not necessary to kill the pilot, but merely to strike a vital part of the driving mechanism.

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The spy in the air may glide down in safety; but his information is lost to his commanding officer. The question arises, can the aeroplane be struck so easily? Probably not. A moving object is always difficult to hit, but trebly so when it soars half a mile up in the sky.

Such guns are made in Germany by Krupp and by the Rheinische Metallwaaren und Ma- schinenfabrik, of Diisseldorf. The guns have small bores and use light projectiles, so that they can be fired quickly. The barrels are com- paratively long, so that a high initial velocity and a low trajectory are obtained. Telescope sights and a range finder are provided, the latter fitted with an arrangement which gives the necessary elevation as the distance is read off.

The ordinary Krupp field gun has a 6.5 cm. bore (Fig. 73), and is fitted with an hydraulic brake and a spring recoil. A coiled spring is provided to balance the gun as it is pointed above the horizontal. The upper part of the gun-carriage is movable, and the wheels can also be given a half-turn away from the body, which assists in quick aiming. This equipment weighs

198 THE NEW ART OF FLYING

875 kilos, 352 kilos of this being in the gun, 523 kilos in the carriage. The projectile weighs 4 kilos — about 81 Ibs. 13 oz. The ini- tial velocity is given as 620 m. — roughly 2,034 ft. a second; the extreme range, 8,650 m. — 9,450 yards; and the height of fire obtain- able, 5,700 m. — roughly 18,700 ft. The gun can be elevated through an angle of 70 degrees above the horizontal, and depressed 5 degrees below it, and it can be revolved right round through an angle of 360 degrees.

A heavier type of Krupp field gun (Fig. 74) has a bore of 7.5 cm., and weighs when ready for firing 1,065 kilos. The weight of the pro- jectile is 5.5 kilos — about 12 Ibs. 2 oz. The initial velocity is stated to be 625 m. per sec- ond, and 9,100 m. and 6,300 m. are given as the extreme range and height attained at trials. The motor-car on which the weapon is carried is designed for an average speed of 45 kilome- tres— 2%y2 miles an hour, and weighs 3,250 kilos — 7,163 Ibs. — without the gun. It car- ries 62 projectiles under the seats, and is propelled by a 50 horse-power motor. It is steadied during firing by a special arrangement

THE FLYING-MACHINE IN WAR 199

which presses the platform against the axles. The gun can be elevated to an angle of 75 degrees from the horizontal, and can be re- volved through a complete circle.

A 10.5 cm. naval gun (Fig. 75) is also made by Krupps. It weighs 3,000 kilos when ready for firing, the projectile 18 kilos, the gun 1,400, the carriage 1,600. Its initial velocity is 700 m. per second, and 13,500 m. and 11,400 m. are given as the extreme range and height attain- able. As in the case of the 7.5 cm. gun, it can be elevated through an angle of 75 degrees from the horizontal, and revolved through a complete circle. All these three guns are 35 calibres long.

The guns made by the Diisseldorf firm are of a somewhat different construction. The bore is 5 cm., and the barrel is 30 calibres long. The gun is worked from a centre pivot by a hand- wheel and weighs 140 kilos — 400 kilos with shield. It can be elevated to an angle of 70 degrees above the horizontal, and depressed 5 degrees below it, and can be revolved through a complete circle. The total weight of the gun, ammunition, five men and car comes to 3,200

200 THE NEW ART OF FLYING

kilos. The car is built at the factory of Ehr- hardt, at Zella, and is driven by a motor of 50 to 60 horse-power, which propels it at a normal speed of 45 kilometres per hour. It is said to be capable of negotiating gradients of 22 per cent even on bad roads. The whole, including the wheels, can be protected by nickel-steel plate shields.

During the French manoeuvres of 1910 a special gun was used for the repulsion of air- ships and aeroplanes, the invention of Captain Houbernat. It was a weapon of 75 millimetres (3 inches) diameter carried on an. automobile. The maximum elevation of fire was 66 degrees. The piece was so mounted that it could be swung down for its whole length with the muzzle beside the driver of the car. When ele- vated, the entire weight of the piece was thrown on the rear of the motor-car. Hence it was necessary to stake down the front wheels. The weapon had a range of 5,000 metres (3 miles). The projectiles fired were Robin shells which ex- plode at a maximum elevation of 2,500 metres (7,200 feet). Besides this piece, a mitrailleuse was used of the usual type employed by French

THE FLYING-MACHINE IN WAR 201

infantry and cavalry, but modified so that it could be elevated at a high angle and fired from an automobile if necessary.

The question of ammunition most suitable for guns is also receiving attention in Germany. The Diisseldorf firm mentioned has introduced a combined shrapnel and ordinary shell for use against both dirigibles and aeroplanes. This new form of shrapnel differs from that which is ordinarily fired in so far as, after the explosion of the shrapnel part, the shell part is carried on to the target, or to the ground, where it det- onates, giving off in its flight an observable cloud of smoke. A somewhat similar projectile is also made by the Krupps. The trail of smoke serves the purpose of indicating how close the projectile came to its mark (Figs. 76 and

77)-

Not upon such artillery and shells and shrap- nel will the enemy rely, but on aeroplanes and airships of his own. He must fight steel with steel. When he sees a black speck in the sky, moving toward him, he gives a quick command. A monoplane or a biplane, perhaps two, start with a whirr from his camp and soar to meet

202 THE NEW ART OF FLYING

that speck. When machine encounters machine in the sky, what will happen? They dare not ram each other. That would mean the inevit- able destruction of both; for the two would surely fall, a mass of twisted and splintered metal and wood. They must fire at each other. But with what? Not with revolvers or rifles, for their range is too small for effective shoot- ing at an aeroplane wheeling around some thousands of yards away; not with a field-piece, for it could not be carried on so light a contriv- ance; but with a machine-gun of especially light construction, a mitrailleuse which will pour forth so many hundred shots a minute in a steady stream, like a jet of water spouting from a hose. That battle in the sky will be won by the swiftest and most readily controlled flying- machine, — by the aeroplane, in a word, which can run and choose its own position and range.

The question may well be asked: What will be the relation of dirigible to aeroplane? Will the one type displace the other? Both types will probably be necessary. The dirigible and the aeroplane will bear to each other the rela-

THE FLYING-MACHINE IN WAR 203

tion of battleship to torpedo boat. In actual war each combatant will have a fleet of both airships and aeroplanes. When an enemy ap- pears it will be the first duty of the opposing fleet to attack him. The home fleet will have a certain advantage because it will be nearer its base. It is not likely that an attacking fleet will sail over an enemy's country unless it is able to destroy the home fleet.

What chance has the dirigible against the aeroplane in an aerial battle? Because of its greater speed the aeroplane has the advantage of fighting or running. Moreover, the dirigible being a most expensive machine, there are al- ways likely to be more aeroplanes than air- ships, so that many aeroplanes can be opposed to a single dirigible, just as many torpedo boats are sent against a single battleship on the theory that one at least will deal a fatal blow.

Its great speed gives the aeroplane an im- measurable advantage over the dirigible even in scouting. Suppose that a frontier several miles long is patrolled by a fleet of dirigibles, and suppose that a considerable number of hos-

204 THE NEW ART OF FLYING

tile aeroplanes is available to ascertain the position and strength of the enemy beyond that frontier. No reasonable number of dirigibles could alone protect that frontier from invasion. The blockade can always be run. However well the line may be protected, there will be spaces where the aeroplane can cross and recross after having taken all the observations required.

For actual fighting purposes the aeroplane cannot as yet be reckoned with. It can be armed only with the lightest gun and can carry only a very limited amount of ammunition and men. The dirigible, on the other hand, can carry a crew of twenty-six and can be fitted with guns much above rifle-calibre. It can remain in the air thirty or forty hours, and in that time travel several hundred miles. When the aeroplane can carry a couple of fighting men in addition to the pilot, and these can be armed with some- thing in the nature of a machine-gun, the effi- ciency of aeroplanes will be far increased if they can cruise in fleets against isolated dirigi- bles. The small target and high speed of the aeroplane will be in its favour, even though its

THE FLYING-MACHINE IN WAR 205

opponent will be more heavily armed. More- over the inevitable confusion attending a com- bat waged upwards and downwards and on all sides should offer many a chance to a daring fighter of delivering a telling blow.

It has been urged that if the aeroplane once gets above the dirigible the fate of the latter is sealed; for the gas bag prevents the dirigible from firing at the aeroplane. It may well be that gun-platforms will be arranged on top with a conning-tower projecting from the car below, through the gas bag. Such a construc- tion has been proposed in Germany. At pres- ent the dirigible can ascend to heights which the aeroplane has not yet reached. The rarity of air at altitudes of over a mile has an im- portant effect on the operation of the aeroplane engine. Most of the men who have soared to great heights in aeroplanes have found that their motors stopped at a certain elevation, and a motor that stops places the pilot in the posi- tion of a balloonist whose gas has leaked away. If the aeroplane can choose its own range be- cause of superior speed, the dirigible can at least choose its own elevation. Yet even here

206 THE NEW ART OF FLYING

there are limitations to be observed. As a dirigible rises its gas expands. To prevent the bursting of the envelope, gas must be allowed to escape. Hence when the dirigible drops again to a lower level, its ascensional power has been considerably curtailed.

Command of the air, like command of the sea, will depend on men and material. With- out men of courage and skill, flying-machines are useless. Without efficient flying-machines, on the other hand, it is obvious that men cannot fly. The situation is much the same in that re- spect as in naval affairs. England has domi- nated the sea because she has had the ships and a well-trained industrious body of civilians to fight them. Acquisition of material is merely a matter of spending money. The nation that spends the most money will have the most numerous and best equipped air navy. In the case of war in the air, as at sea, success will depend not only on abundant material, but on the ability to supply wastage of war, which is enormous and increases in enormity as the ma- terial becomes more complicated and costly. In matters of armament, however, cost is not

THE FLYING-MACHINE IN WAR 207

the guiding principle. Nothing is so expensive as defeat, and to avoid defeat the most efficient aircraft must be provided in sufficient numbers. Battles, aerial or terrestrial, are won as much by money as by hard fighting.

CHAPTER XII

SOME TYPICAL BIPLANES

ALL biplanes, no matter by whom designed, have certain features in common. Besides the two superposed supporting surfaces from which they take their name, they all have a horizontal rudder or elevator, by means of which the ma- chine is guided up or down and is prevented from pitching; a vertical rudder, by means of which the machine is kept on an even course and turned to the right or to the left; and some means by which the amount of main sur- face exposed to the pressure of the air can be varied, so as to keep the machine in balance from side to side. To these essential elements a tail, consisting of a small horizontal surface, is usually added, because it serves to steady the machine in flight.

Just how these elements shall be disposed is a matter of more or less difference of opinion among biplane designers, and this difference of opinion has given us the various biplanes of the

SOME TYPICAL BIPLANES 209

Wrights, Curtiss, Farman, Goupy, Sommer, Breguet, and others. Biplanes as a class fol- low the lines of the Wright machine. It is here impossible and unnecessary to describe in de- tail all the biplanes in use at the present day. For our purpose it will be quite sufficient to con- fine ourselves to the Wright, Curtiss, Farman, and Sommer machines, inasmuch as they rep- resent the chief systems of control to be found in the two-surface machine.

THE WRIGHT BIPLANE

The two supporting surfaces of the Wright machine consist of canvas stretched over and under ribs of spruce. At a point near the centre these surfaces are three inches thick. The dimensions of the planes vary. In the earlier machines they measured 41 feet in spread, 6.56 feet in depth, and 538 square feet in area. In the later machines the spread has been re- duced to 39 feet, the depth to 5.5 feet, and the area to 410 square feet. A smaller model has also been designed in which the spread has been reduced to 26 feet.

In the first Wright machines (Fig. 79) the

210 THE NEW ART OF FLYING

horizontal or elevation rudder was mounted in front, and was so constructed that it was auto- matically curved concavely on the under side when elevated, and in the opposite way when depressed. A long wooden rod connected the horizontal rudder with a lever, which was ma- nipulated by the operator's left hand (Fig. 20). By pulling the lever toward him the operator inclined the rudder upward; by pushing the lever away from him the operator depressed the rudder.

The vertical rudder, which not only served to steer the machine in a horizontal plane but also to prevent it from spinning on a vertical axis, was mounted in the rear of the machine as at present. It consisted and still consists of two parallel vertical surfaces, swung by a lever in the operator's right hand. By pushing the lever away from him the operator turns the machine to the left; by pulling it toward him he turns the machine to the right.

Side-to-side balance has always been main- tained in the Wright biplane by warping the main planes in the manner explained in Chap- ter V. The entire front of the two supporting

Fig. 75- — A Krupp 10.5 cm. naval gun for repelling aircraft

SOME TYPICAL BIPLANES 211

surfaces is rigid; but the rear corners are mov- able. The central sections of the two planes are rigid and are never moved in balancing the machine. Only the rear corners of both planes play any part in controlling the apparatus. These flexible rear corners of both planes are connected by means of cables with the lever in the operator's right hand (Fig. 20), in other words, the lever which controls the vertical rud- der. By throwing the lever from side to side the rear corners are flexed in opposite direc- tions; in other words, as one corner of one plane is bent down, the other corner of the same plane is bent up, with the result that the entire plane is given what the Wrights call a " helicoidal warp." The same lever controls both the vertical rudder and the warping of the planes, because the Wrights found that as the planes were bent the machine would spin on a vertical axis, as explained in Chapter V. This lever is therefore swung in a circular or ellip- tical path so that the planes are warped and the vertical rudder swung in the proper direc- tion at the same time.

In the newer Wright biplanes a modified form

212 THE NEW ART OF FLYING

of lever has been adopted to warp the wings and turn the vertical rudder, the principle, how- ever, remaining substantially the same. The new lever is provided with an auxiliary grip, which can be worked by the fingers to operate the vertical rudder, while the main portion of the lever is pushed forward or backward to warp the wings.

In the European Wright machine a tail was soon added, because it was found that the ma- chine pitched markedly in flight. This pitching was corrected, to be sure, by manipulation of the horizontal rudder, but this required con- siderable skill on the pilot's part. Hence a horizontal surface was placed in the rear to act as a steadying tail, which surface could be turned up and down to aid the elevation rudder in its action. In the American machines, made by the Wrights themselves, this horizontal tail has also been incorporated (Fig. 80). What is more, the front horizontal rudders have been abandoned altogether and the rear horizontal surface or tail employed both as an elevator and a steadying surface. The result has been that the machine flies far more steadily than formerly.

SOME TYPICAL BIPLANES 213

The earlier Wright machines were mounted on skids. The machines were launched on a starting rail (Fig. 12) in the manner described in Chapter IV. The European manufacturers of Wright machines soon introduced wheels on which the machine ran in the usual manner, the skids serving for alighting as before. This im- provement has been adopted by the Wrights (Fig. 14).

The motors which drive the American Wright machines are made by the Wrights themselves. The horse-power, except in small racers, varies from 25 to 30, which is consider- ably below that of most European biplanes. The motor drives two propellers revolving in opposite directions at the rate of 400 revolu- tions a minute, which is remarkably slow as propeller speeds go.

The Wright racing aeroplane, which made its first appearance at the Belmont Par!: Inter- national Aviation Meet of 1910, is not essen- tially different from the regular Wright biplane. In order to attain high speed, the planes have been reduced in spread, and consequently in area, and a V-motor of high power has been in-

2i4 THE NEW ART OF FLYING

stalled. The planes are 21 feet in length and 3l/2 feet wide. The combined area of both planes is 180 square feet. It is stated that the motor develops about 60 horse-power. The machine was used by Johnstone when he made an altitude flight of 9,714 feet. The machine is credited with a speed of 685^ miles an hour.

THE CURTISS BIPLANE

Like the Wrights, Mr. Glenn H. Curtiss has departed somewhat from the type that he originally evolved. In his earlier machines (Fig. 25) the supporting planes consisted of " rubberized " silk stretched over the top of a light spruce frame. The spread of the planes was 26.42 feet, the depth 4.5 feet, the dis- tance between the planes 5 feet, and the area 220 square feet. In the more recent machines the spread is 32 feet, the depth 5 feet, and the area 316 square feet.

The horizontal or elevation rudder of the Curtiss biplane consists of two parallel hori- zontal surfaces mounted in front of the ma- chine and moved in unison by means of a steer-

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ing-wheel. A long bamboo rod connects the horizontal rudder with the steering-wheel, the arrangement being such that by pushing or pull- ing the steering-wheel backward or forward, the rudder is respectively turned down or up.

The vertical rudder of the Curtiss machine is a single surface placed in the rear and also operated by the steering-wheel through the medium of cables. To work the vertical rud- der the steering-wheel is rocked like the pilot- wheel of a steamboat. To secure steadiness in flight and to reduce the pitching effect a hori- zontal surface or tail is mounted in the rear.

Side to side balance was maintained in the Curtiss machine up to 1910 by means of two balancing planes of about 12 square feet in area, mounted between the two main planes. These balancing planes were swung in opposite directions by cables connected with a yoke partially surrounding the aviator's body and mounted to rock. By leaning from side to side the aviator moved the yoke and consequently the balancing-planes. The arrangement was such that the instinctive motion of the body swung the balancing-planes.

216 THE NEW ART OF FLYING

In the late Curtiss machines ailerons (Fig. 29) similar to those of the Farman biplane (q. v.) are employed. They are operated in the same manner as the old balancing-planes.

The motors which drive the machine are made by Mr. Curtiss himself. On the larger machines the motors are of the well-known V-type and develop 50 horse-power. On the smaller machines 25 horse-power vertical cylin- der motors are used. The engine is controlled by an accelerator pedal on the left of the steer- ing column. There is also a throttle lever close to the pilot's seat. Another pedal under the action of the pilot's right foot is employed to cut off the ignition and to apply a brake to the front wheel of the chassis by which the machine is carried on the ground. Mr. Curtiss himself has driven machines with 100 horse-power motors.

The propellers are made of wood and are two-bladed. Their diameter is 6 feet, the pitch 5 feet, and the speed 1,200 revolutions a minute.

The machine starts and alights on three rubber-tired wheels.

SOME TYPICAL BIPLANES 217

For the Belmont Park aviation meeting of 1910 Mr. Curtiss made a machine which was practically a monoplane. The upper plane was reduced to a surface of almost negligible area. At the meeting in question the machine was not given a very extensive trial, so that it could not be compared with the Bleriot and other machines that were entered.

THE FARMAN BIPLANE

The Farman biplane is the outcome of Henry Farman's experience • with the old, cellular Voisin biplanes (Fig. 34). Like Curtiss, he was manifestly influenced by the Wrights, as, indeed, was every French maker of flying- machines after the memorable flights of Wilbur Wright in France in 1908. As it now stands, the Farman is probably the most widely used biplane in Europe and deservedly so by reason of its ingenious and extraordinarily staunch construction.

The main supporting surfaces of the Farman biplane are made of what is known as " Conti- nental " cloth, a special fabric manufactured for aeronautic purposes. The cloth is stretched

218 THE NEW ART OF FLYING

over ribs of ash. Although the dimensions vary somewhat, the average Farman biplane has a spread of 33 feet, a depth of 6.6 feet, and a total area of 430 square feet. In the later machine the upper plane has a greater spread than the lower. The planes are sepa- rated by a distance of 7 feet.

The elevation or horizontal rudder is car- ried out in front of the machine, after the early Wright fashion. Wires run from the rudder to a lever held by the pilot's right hand (Fig. 28). By pushing the lever away from him, the pilot depresses the rudder; by pulling the lever toward him, he tilts the rudder up.

The same lever controls the lateral balance of the machine. Four hinged flaps, constitut- ing the rear corners of the main planes, are connected by cables with the lever. By throw- ing the lever from side to side the flaps (aile- rons) on one side are pulled down, and the flaps on the other side are relaxed so that they lie practically flush with the main planes. When the machine is standing still on the ground, the flaps hang down. As soon as the

SOME TYPICAL BIPLANES 219

machine is in flight, they stream out behind the main planes.

The vertical rudder consists of two parallel vertical surfaces in the rear of the machine, which surfaces are connected by means of tiller cables with a lever worked by the pilot's feet.

Somewhat in advance of the vertical rudder are two horizontal surfaces which constitute a steadying tail. The top surface of this tail can be swung up and down in conjunction with the front horizontal rudder.

The motors used on the Farman machine are usually Gnome rotary motors of 50 horse- power, although 100 horse-power motors have been used on occasion. The propeller is a Chauviere wooden propeller of two blades, with a speed of 1,200 revolutions a minute. The pitch of the propeller is 4.62 feet, the diameter 8.5 feet.

The machine is mounted on two skids, each of which is fitted with a pair of wheels. Heavy elastic bands connect the skids with the axles of the two wheels. In alighting the bands yield and allow the skids to take the main shock.

220 THE NEW ART OF FLYING

This is a most ingenious, efficient, and simple invention, which has been widely copied.

THE SOMMER BIPLANE

The biplane built by Farman's former pupil Roger Sommer (Fig. 83) follows the Farman type rather closely. The supporting surfaces consist of rubber cloth stretched over wooden ribs. The spread is 33 feet, the depth, 5.2 feet, and the total area 326 feet.

The horizontal rudder is carried well out in front of the machine. It consists of a single horizontal surface. As in the Farman machine, it is controlled by a single lever, which, instead of being placed at the right, is mounted at the left. The operation of this lever and the con- sequent elevation and depression of the rudder are exactly the same as in the Farman machine.

As in the Farman machine, ailerons are em- ployed to maintain side-to-side balance. These ailerons are to be found either on both planes or only on the upper plane. They are not oper- ated, as in the Farman machine, by the lever which controls the horizontal rudder. Instead, the Curtiss principle of using the instinctive

SOME TYPICAL BIPLANES 221

movements of the pilot's body is adopted. Wires leading from the ailerons are attached to a yoke partially surrounding the aviator's body. In obedience to the movements of the body the ailerons are pulled down and up respectively.

The vertical rudder is a single surface at the rear of the machine operated, as in the Farman machine, by a foot lever.

To steady the machine a single horizontal surface is mounted in the rear. This surface is movable, not for the purpose of acting as an elevation rudder, but to increase or decrease the stabilising effect. A lever at the aviator's right controls this tail.

The machine is mounted on skids and wheels, the skids serving for alighting. Rubber springs are employed in connection with the wheels, as in the Farman machine.

As a general rule Sommer machines are driven by 50 horse-power Gnome motors, which turn a two-bladed Chauviere propeller at the rate of 1,200 revolutions a minute. Some ma- chines have been fitted with 100 horse-power motors.

CHAPTER XIII

SOME TYPICAL MONOPLANES

MONOPLANES differ less from one another than biplanes. Nearly all of them have the same system of lateral control, and the same method of mounting the motor. As a general rule this system of lateral control is the Wright wing-warping method. The motors are usu- ally Gnome motors mounted in front of the machines.

THE ANTOINETTE MONOPLANE

Antoinette monoplanes (Fig. 84) are de- signed and built by Levavasseur, a well-known manufacturer of motors.

The single silk surface of an Antoinette mon- oplane is constructed in two halves which are so mounted that they form a slight dihedral angle. This plane is braced to a central mast or spar, and is carried on a girder-like frame of aluminium, cedar, and ash. The spread of the plane is 49 feet ; the area 405 square feet.

SOME TYPICAL MONOPLANES 223

The horizontal rudder is a single surface at the extreme rear of the machine and is con- trolled by a hand-wheel at the aviator's right

(Fig. 32).

The vertical rudder comprises two surfaces at the rear of the machine. Tiller cables lead from the surfaces to a lever operated by the aviator's feet.

To balance the machine from side to side the plane is warped after the Wright principle. In contradistinction to the Wright machine, how- ever, the front edges are flexible and the rear edges fixed. To warp the plane a hand-wheel is provided at the aviator's left.

The mast, to which the plane-halves are braced, contains a pneumatic shock-absorber in its lower end, besides which there are two wheels with heavy pneumatic tires and a for- ward plough-like skid. A skid in the rear is used to support the tail.

On each side of the body is a horizontal, fan- shaped keel at the rear to steady the machine longitudinally. A vertical fin above this hori- zontal fin gives a certain amount of lateral stability.

224 THE NEW ART OF FLYING

An 8-cylinder V-type water-cooled Antoinette motor of 50 horse-power is placed in front of the machine and drives a y-foot propeller. At the International Aviation Meeting held in 1910 at Belmont Park, Latham flew a 100 horse-power Antoinette.

The Antoinette monoplanes which are built in Germany are equipped with 100 horse-power Gnome motors of fourteen cylinders. The area of the wings can be reduced by about one square metre, the smaller area being employed when the aviator is flying alone. When three pas- sengers are carried besides the aviator, the span can be increased to fifteen metres, so that the area amounts to four square metres. The passengers are placed symmetrically, so that the centre of gravity of the machine is not dis- turbed. This large Antoinette machine is some- what longer than the normal Antoinette, built in France. Since the utilisation of the Gnome motor means the abandonment of the usual Antoinette water-cooling plant, and such auxil- iary apparatus as radiators, pumps, etc., it was necessary to redistribute the weight. Accord- ingly the German machine is longer than the

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THE BLERIOT MONOPLANES

Louis Bleriot is a well-to-do manufacturer of automobile lamps whose attention was di- rected to flying-machines in 1906. He has the distinction of having broken more machines and more frequently risked his life than any other man interested in the new sport. What is more, he was the first man who ever flew a monoplane.

Bleriot's remarkable experience has resulted in the development of two types of machines known respectively as the Bleriot XI (Fig. 81) and the Bleriot XII (Fig. 88). The Bleriot XI is a fast model patterned after that with which Bleriot flew across the English Channel; the Bleriot XII is a passenger-carrying machine, which differs somewhat from the XI.

The main plane of the No. XI is built in halves and consists of " Continental rubber " stretched over a wooden frame. In order that the machine may be readily transported the halves of the plane can be detached from a

226 THE NEW ART OF FLYING

central joint. This detachability, moreover, renders it possible to interchange wings of large and small area. The spread is normally 28.2 feet, the depth 6.5 feet, and the total area 151 square feet.

To steady the machine longitudinally in flight a horizontal surface or tail is employed. The horizontal or elevation rudder consists of two movable surfaces, one at each side of this tail. The horizontal rudder is operated by a central lever in the manner described in Chapter V.

The vertical rudder of the Bleriot XI con- sists of a vertical surface in the rear of the machine. It is operated by tiller wires con- nected with a foot lever.

Lateral control of the machine is obtained by wing-warping, as in the Wright biplane, For this purpose the central lever or bell- column, described in Chapter V, is employed, the column being thrown from side to side to pull on one wing-warping wire and to slacken the other.

In the machine with which he flew across the English Channel, Bleriot used a 25 horse- power Anzani motor. Since then 50 horse-

SOME TYPICAL MONOPLANES 227

power Gnome motors have usually been em- ployed, the motor being mounted in front of the machine and driving a two-bladed Chau- viere propeller 6.87 feet in diameter at the rate of 1,200 to 1,400 revolutions a minute.

The starting and alighting gear of the Ble- riot XI consists of rubber-tired wheels and rubber shock-absorbers. For the rear wheel, as shown in Fig. 86, a skid has been substituted.

In the smaller type of Bleriot a fuel tank is placed very far below the frame in order to lower the centre of gravity. In the larger type two fuel tanks are placed between the wings in the body of the machine right in front of the pilot's seat. In order that the lowered fuel tank of the small Bleriot XI may offer as little resistance to the air as possible, it is given a fish form (Fig. 86) for the reason that Prandtl has proven that such shapes offer the least resistance.

Racing machines are also made on the lines of the Bleriot XI, but with a smaller wing- spread and 100 horse-power, fourteen-cylinder Gnome motors.

The passenger-carrying Bleriot XII is so con-

228 THE NEW ART OF FLYING

structed that the aviator sits with his passen- gers under the main plane, back of the motor. This type is now practically abandoned. In the Bleriot XI he sits with his body above the main plane. A later passenger-carrying model has been evolved in which the two occupants of the machine sit side by side above the plane, as in the regular Bleriot XL

Early in 1911 Bleriot brought out a remark- able 10 passenger monoplane, the lateral sta- bility of which was controlled by ailerons and the 100 horse-power motor of which was placed with the propeller directly behind the plane, following Maxim's suggestion. A front hori- zontal rudder was also provided, similar to that of the Farman biplane.

THE SANTOS-DUMONT MONOPLANE

By far the smallest flying-machine of the day is the monoplane designed by Santos-Dumont. Because of its littleness it is extremely fast.

The supporting surface consists of silk stretched over bamboo ribs. This silken sur- face is braced by wires to a central frame of bamboo and metal tubing. The spread is 18

SOME TYPICAL MONOPLANES 229

feet, the depth 6.56 feet, and the area 113 square feet.

The vertical rudder and the horizontal rud- der, usually entirely distinct, in most biplanes and monoplanes, are here combined after the Langley principle. This combined rudder is carried on a universal joint so that it can be turned in any direction. Although they are mounted together, the horizontal and vertical members of the rudder are operated indepen- dently. The vertical surface is controlled by a hand-wheel or lever at the pilot's left hand. The horizontal rudder is operated by a lever held in the aviator's right hand.

Following the principle of Curtiss, lateral control is effected by the instinctive movements of the aviator's body; but instead of employ- ing balancing planes or ailerons Santos-Dumont warps the plane. The wires leading from the plane are connected with a steel member sewed on the pilot's coat. Hence the pilot has only to sway his body in order to warp the wings.

The starting and alighting gear consists of two wheels at the front and a skid at the rear.

230 THE NEW ART OF FLYING

No tails or other stabilising surfaces are used, although the horizontal member of the rudder undoubtedly acts as a tail, as in the newer Wright biplane.

The motor may be of any type. Darracq, Clement-Bayard, and Panhard motors of 30 horse-power have been used. The propeller is a two-bladed Chauviere.

CHAPTER XIV

THE FLYING-MACHINE OF THE FUTURE

WHAT will the flying-machine of the future be like? He would be a wise man indeed who could predict with any degree of accuracy the exact form and dimensions of the coming aero- plane. The dreams of the old-time imaginative novelist seem almost to be realised now. Our more modern Kipling, looking back in his mind's eye at our feeble efforts, talks with scorn in the " Night Mail " of " the days when men flew wooden kites over oil-engines." Yet it is not likely that we shall graduate from that crude type for many years to come. A scien- tific forecast of the flying-machine's possibili- ties and its effect on human affairs must therefore be deduced from present aeroplane facts.

The aeroplane of our time is a thing of almost feathery lightness. In its construction the lightest and toughest woods and the small- est possible amount of metal must be used. As

23 2 THE NEW ART OF FLYING

a result, it is wellnigh as delicate as a watch, and like a watch it must be handled with some care. Since the motor is the heaviest part of a flying-machine, it offers the most serious ob- stacle to the attainment of lightness. Because of the motor's necessarily small size its power is none too generous, and because of its delicate construction it breaks down with awkward ease. Hence it is safe to prophesy that the flying-machine of the future will be equipped with motors far higher in power than those at present in use.

It is probable that the future aeroplane will carry two motors, instead of one, each motor independently operative, so that if one fails, the other will still be able to drive the machine safely through the air. For military purposes at least, such a double-motor aeroplane is abso- lutely necessary. Imagine a spy in the air compelled to glide ignominiously down in an enemy's camp, because his engine failed him! Mere considerations of safety demand the in- stallation of two motors on a flying-machine. In March, 1910, the French aviator Crochon fell to the ground in a cross-country flight from

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Mourmelon to Chalons, because his motor broke down. Le Blon was killed at San Sebas- tian on April 2, 1910, as a result of a similar motor trouble. During the Nice meeting in April, 1910, Chavez and Latham mercifully dropped into the Mediterranean, also because of motor trouble. All of these accidents might have been avoided if the aviators could have relied upon a second motor.

The aviator of the present day is somewhat in the position of a bicycle rider on a slack wire, armed with a parasol. He must exercise inces- sant vigilance, lest he lose his balance. The strain upon nerves and muscles, for the begin- ner at least, is tremendous. Hence, even now, we hear of automatic devices which will prevent the loss of a flying-machine's equilibrium and which will enable the aviator to soar in the sky more blithely than he can at present.

Balloonists find difficulty in ascertaining their location, particularly after descending from a cloud bank. It is true that the aviator can swoop down to the earth and find out where he is. Nevertheless, it is very likely that in the future he will be provided with charts and in-

234 THE NEW ART OF FLYING

struments which will obviate that necessity, — charts which will indicate landmarks and instru- ments which will indicate the angle of the flight path and which will include convenient field glasses and day and night signalling devices. Needless to say the aviator will carry a com- pass, probably a prismatic compass from which directions can be taken with great accuracy so long as fixed objects on the earth are visible. No doubt the compass will have a dial covered with luminous material, visible in the dark. At night a trailing-line will be cast overboard, fitted with some electrical indicator, which will ring a bell if some object should be struck, to warn the pilot that he is flying too low. The German Aerial Navy League has proposed that special beacon lights be erected at certain points. The aviator of the future will certainly need some such guidance if he flies by night, — some light which will send a long beam in the direction in which the wind is blowing.

Two men at least will be carried by the aero- plane of the future, — one to look after the controlling mechanism and the other to navi- gate. The military aeroplane will surely be so

THE FUTURE FLYING-MACHINE 235

manned; for one man alone cannot perform the duties of mechanician and observer.

Explorations into unknown lands will be robbed of their perils by the flying-machine. The hummocks of the Arctics, the jungles of Africa, the morasses of a country untrodden by the foot of man can hide nothing from the ex- ploring aviator. Tasks which formerly occu- pied years for -their achievement will hence- forth be accomplished in as many months, weeks, or even days. If Lieutenant Shackleton found the motor-car of service in Antarctic ex- ploration, what shall be said of the flying-ma- chine which speeds on its journey unimpeded by mountains of snow or grinding pack-ice? The character of the information gathered by the future explorer-aviator will be of greater scien- tific value than that which is at present so pain- fully collected. A Livingstone or a Stanley chop- ping his way through dense tropical vegetation brings back no complete map of the region trav- ersed. All that he can show is his itinerary, — a mere fringe of the new country. Mountains and rivers he indicates rather than charts. In- stead of crawling over the face of our planet,

236 THE NEW ART OF FLYING

the sky-explorer will some day survey it from a height. He will see his Africa or Asia or India spread before him like a map. His eye will sweep an area measuring hundreds of square miles in extent. The camera will record those topographical peculiarities which he came to note, and he will be spared the necessity of imperilling his life to discover the source of a river or the secret of some Tibetan Forbidden Kingdom.

So far as actual appearance goes, the opin- ions of present-day flying experts differ as to the flying-machine of the future. Mr. R. W. A. Brewer, an English authority, sees a larger and a heavier machine than we have at present, a kind of air yacht, weighing at least three tons, and built with a boat-body. The craft of his fancy will be decked in. It will carry several persons conveniently and will be provided with living and sleeping accommodations. He proph- esies that it will fly at speeds of one hundred and fifty to two hundred miles an hour, for the rea- son that high speeds in flying, according to some authorities, mean less expenditure of power than lower speeds. Mr. F. W. Lanchester, as we

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THE FUTURE FLYING-MACHINE 237

have pointed out in a previous chapter, enter- tains similar views on the necessity of high speed. If it is ever possible for an aeroplane to travel at such terrific velocities, whole conti- nents will become the playgrounds of aviators. Daily trips of one thousand miles would not be extraordinary. It is even conceivable that there will be aeroplane liners which will travel from Europe to America in twenty-four hours.

It seems certain that special starting and alighting grounds will be ultimately provided throughout the world. If tramcars must have their stables and their yards, it is not unreason- able to demand the provision of suitable aero- plane stations. Depots or towers will be erected for the storage of fuel and oil, — garages on stilts, in a word. The aviator in need of sup- plies will signal his wants, lower a trailing line and pick up gasoline by some such device as we now employ to catch mail sacks on express trains.

It may well be that the advent of the flying- machine will have a marked effect on our archi- tecture. Some day houses will be provided with landing stages, assuming that the aeroplane

238 THE NEW ART OF FLYING

will be able to alight more easily than at pres- ent and without the necessity of running along the ground for some distance before it expends its momentum. Ely's remarkable feat in land- ing on the deck of a warship in the harbour of San Francisco shows that the thing is not re- motely possible. When that day dawns, roofs will disappear in favour of flat terraces suited for launching and landing. A business man in- stead of travelling in a lift from the ground floor of a building to his office on the twenty- first floor, will start from the roof of the build- ing and proceed downward.

Above all things, flyirg must be safer than it is now. Although the dangers of a sport will inevitably attract to it adventurous spirits, a really commercial machine must satisfy the requirements of the highly nervous man or woman to whom sailing a yacht seems a suicidal pastime.

The early days dl the bicycle and the auto- mobile industries offer a close parallel to the present position of the aeroplane industry. The pioneers having shown the way, the ma- chine immediately became an instrument of

THE FUTURE FLYING-MACHINE 239

sport. Speed was the thing first desired, and the speed of anything that moves can best be demonstrated in a competition. Bicycle and automobile races became and still are, to some extent, the manufacturer's opportunity of test- ing and demonstrating the quality of his ma- chines. Long before the manufacture of either touring bicycles or touring automobiles as- sumed their present proportions, the production of the racing machine was all important. The flying-machine is now in this stage. Races and endurance tests will be the battles from which will emerge the flying-machine of the future, — the machine capable of sustained flights, many hours in duration, at speeds of eighty and one hundred miles an hour. The racer will give birth to the touring flyer, just as the touring car of to-day was evolved from the racing car of five years ago.

Incredible as it may seem, in less than a year from the date when Blerioc flew over the Eng- lish Channel, a feat which set France aeroplane- mad, the actual sales of flying-machines out- numbered the actual sales of automobiles in the first year of their commercial development.

240 THE NEW ART OF FLYING

A flying Frenchman clamours for his Bleriot or Farman as impatiently as an automobiling American millionaire for his high-powered car, ordered months in advance. The one is no more inclined to bide his time than the other. Hence agents have sprung up in Paris, who order machines from the manufacturer on spec- ulation, and receive as much as $500 to $1,000 above the factory price for immediate delivery. In Paris at least such signs as " Bouvard et Pecuchet, Agents pour Monoplanes Antoi- nette " can be seen even now, — the harbinger of a great industry of the future and of flying- machine quarters in our large cities.

Compared with the flying-machine of the future, the motor-car will seem as tame and dull as a cart, drawn by a weary nag on a dusty country road. Confined to no route in particu- lar, unhampered by speed restrictions, the speed maniac can drink his fill in the high-powered monoplane. Even the most leisurely of air- touring machines will travel at speeds that only a racing automobile now attains, while the air racer will flit over us, a mere blur to the eye a buzz to the ear. In an hour or two a

Photograph by Edwin Levick

Fig. 83. — The 100 horsepower Antoinette monoplane

that Hubert Latham flew at Belmont Park

during the International Aviation

Tournament of 1910

THE FUTURE FLYING-MACHINE 241

whole province will be traversed; in a day a whole continent. An air tourist, a few years hence, will breakfast in Paris and sup the same evening in Moscow. His air-charts, the equiva- lent of our present road automobile maps will be an atlas, a book in which the air-routes of all Europe are laid down. Swifter than any storm will be his flight. If the black, whirling mael- strom of a cyclone looms up before him, he can make a detour or even outspeed it; for the velocity of his machine will be greater than that of the fiercest of howling, wintry blasts. At a gale which now drives every aviator timorously to cover, he snaps a contemptuous finger, plunges through it in a breathless dash and emerges again in the sunshine, as indifferent to his experience as a locomotive engineer after running through a shower.

The aspect of the heavens will be wonder- fully changed when the pleasure plane of the air has arrived. Black specks will dot the blue sky, more like birds than machines, specks that the practised will recognise as impetuous and daring high flyers. Lower down the less reck- less will perform their evolutions, and the whirr

242 THE NEW ART OF FLYING

of their motors will be as the droning of bees, so numerous will they be.

All this deals with the sport. Has the aero- plane no mercantile future? Shall we see flocks of gigantic artificial birds, freighted with heavy cargoes, darkening the sky as they wing their way across the Atlantic or the continent? Will travelling by steamship and railway give way to the aeroplane?

The most sanguine aeronautic engineer would not venture to predict the supplanting of the freight train or the steamer by the aeroplane. For many, many years to come the flying- machine will remain what it is now, a vehicle of sport and war only. Perhaps it may never be anything more. Why? Because it cannot be made big enough. The carrying capacity of an aeroplane depends on its spread of plane. To increase the load means so important an in- crease in spread that an unmanageable area of supporting surface would be necessary. In order to secure the necessary strength to uphold this increased area an increased weight per square yard is entailed. Hence it is unlikely that aeroplanes carrying many passengers will

THE FUTURE FLYING-MACHINE 243

be built in our time. Not so very long ago Mr. Orville Wright expressed the opinion that aero- planes " will never take the place of trains or steamships for the carrying of passengers. My brother and I have never figured on building large passenger-carrying machines. Our idea has been to get one that would carry two, three, or five passengers, but this will be the limit of our endeavours."

The late Prof. Samuel P. Langley discovered in the course of his classic experiments that the higher the speed at which a plane travels through the air the less is the supporting sur- face required. Hence there is a chance that a machine may be constructed in the future which, taking advantage of this law, will be provided with a supporting surface adjustable in area, so that it can start with a large surface, and fold up its planes at full speed. In such a machine the supporting surface would be ulti- mately reduced until it is a thin edge. We would have an aeroplane propelled by great power, supported largely by the pressure against its body, its wings reduced to mere fins, serving to guide its motion.

244 THE NEW ART OF FLYING

As a future commercial possibility, the air- ship is far more promising than the aeroplane. To the size of the airship there is no limit. Indeed, the larger it can be built the more eco- nomically can it be driven, when we measure economy by ratio of carrying power to cost of operation. Just how large an airship can be constructed is a question of constructive en- gineering. In considering that question the late Prof. Simon Newcomb pointed out that econ- omy is gained only when the dimensions of an airship are so increased that it will carry more than an ocean steamer or a railroad train. To attain that end he estimated that it would be necessary to build an airship at least half a mile in length and six hundred feet in diameter. Such an airship might carry a cargo of ten thou- sand tons or fifteen thousand passengers. The construction of so huge a craft is not an utter engineering absurdity, remote as it may seem to us now. We recently witnessed something like this when Count von Zeppelin's passenger- carrying airship made a voyage that excited the admiration of the world, even though the vessel was wrecked in a storm. Some fourteen

THE FUTURE FLYING-MACHINE 245

passengers were transported on that remark- able trip, for whom adequate seating and dining accommodations were provided. But the cost of operating such a giant of the air is enormous. After all is said, money will decide the ques- tion of the commercial possibilities of flying- machines and airships. How much does it cost to build? How much does it cost to maintain? How much does it cost to operate? Not until these questions are answered satisfactorily can we tell whether or not the aeroplane will ever be anything more than a racing machine for gilded youth and the dirigible an air-yacht for bankers too old for the more perilous aeroplane.

CHAPTER XV

THE LAW OF THE AIR

IT is one of the most difficult tasks of govern- ment to adapt existing laws to those incessant changes in the relationships of nations and in- dividuals which are brought about by the in- vention of new arts and industries. The rail- road, the telegraph, the telephone, and wire- less signalling have each given the legislatures of the world no little concern in developing codes which would enable the new inventions to take their place in our daily lives without too greatly disturbing vested rights.

Englishmen and Americans are fortunate in having a common law, which, although based upon custom and precedent, is nevertheless so flexible that it is able to adapt itself to the new conditions which the flying-machine will create. To supplement whatever shortcomings the com- mon law may have, there can be no doubt that special statutes will be passed in this country and England to define the relations of the air-

THE LAW OF THE AIR 247

men to people on the earth below. European nations develop their laws more consciously. They even anticipate conditions that may arise by the introduction of a new invention. Thus we find that continental jurists have given con- sideration to questions of such detail as the nationality to be ascribed to persons born on board voyaging air-craft, rights in respect of salvage, and other doctrines drawn from mari- time law. Twenty years hence it will be inter- esting to compare Anglo-Saxon air-laws evolved from custom and actual experience, with the air- laws of the continent, many of them enacted before aerial navigation was really established. The mere fact that aeroplanes and airships plough the air above us is in itself a circum- stance that gives rise to a new legal situation. As Professor Meli of Zurich has put it, a careful man must now look not simply in front of him and on either side, but above him as well.

Has the airman any inherent right to navi- gate the air at all? That is the first question that must be decided by civilised countries, whether they be Anglo-Saxon, European, or Asiatic. The question of an inherent right must

248 THE NEW ART OF FLYING

be considered both from the standpoint of the private property owner and from the standpoint of international law.

Even among lawyers the old saying that to the owner of a piece of land belongs not only the earth beneath his feet to the very centre of the globe, but the air above his property to an infinite height, is regarded as a basic principle of the English common law. Yet, to use the words of Brett, Master of the Rolls, in the case of Wandsworth Board of Works v. United Telephone Company, (1884) 13 Q. B. D. 904, this old maxim is at best a u fanciful phrase. " The maxim can be traced to Coke upon Littleton and to Blackstone. In all the vast body of deci- sions on which the English common law is based, there can be found none in which the ownership of the air to a height above that at which a prop- erty owner could make reasonable use of it, is the point at issue. It is true that Coke's old saw and its reiteration by Blackstone have been approved in many a dictum; but dicta are not decisions. If the doctrine were really good common law, every man who sailed over the land of another would be a trespasser. Sup-

THE LAW OF THE AIR 249

pose that an action were brought to collect dam- ages for trespass. It is hardly likely that even nominal damages could be recovered, for the simple reason that no injury has been worked to the landowner's estate and no nuisance has been created. Decisions enough can be found to justify the action of trespass in all cases of encroaching signs, buildings, trees, overhang- ing telegraph and telephone wires; but in all these cases the defendant's possession and the use of the land have been interfered with. It may well be concluded that rights in the air must be strictly appurtenant to the soil beneath, and that unless a reasonable use of the land is interfered with, no action for trespass will lie. The actual interference with the enjoyment of the land as the sole justification for legal action is fully recognised in Europe. Even be- fore the advent of the flying-machine and the airship the code of the Canton of Grisons pro- vided that " property in land extends to the air space (above) and the earth beneath, so far as these may be of productive value to the owner." In the German Civil Code the rights of the air- man are recognised in a clause in which the

25o THE NEW ART OF FLYING

property holder " cannot prohibit such interfer- ences undertaken at such a height or depth that he has no interest in the prevention."

It is probable that one of the first of the fu- ture laws of the air will fix the height at which air-craft must travel. In all likelihood the aero- naut will be compelled to sail at a height not less than fifteen hundred feet over inhabited districts and navigable inland waters, leaving him free to fly at any height he pleases over wildernesses and the high seas. A man who sails over a city not only takes his own life into his hands, but also endangers the lives of others, because he cannot readily alight should his motor fail him. The French advocate, Fau- chille, has therefore proposed a law which will forbid flying over communities without the per- mission of the authorities.

That an action can be brought against an aviator who alights upon a piece of land with- out the owner's permission, even though he be compelled to do so against his will, is even now well established. In a New York case (Guille v. Swann, 19 Johns. 381 ; 10 Amer. Dec. 234) decided in 1822, an aeronaut was held respon-

THE LAW OF THE AIR 251

sible not only for the direct damage caused by the descent of his balloon into a garden, but even for the remote damage caused by the crowding of strangers upon the property to sat- isfy their curiosity. Such unpremeditated de- scents will be frequent in coming years. The obvious necessity of sometimes alighting against one's will demands some law which will enable the airman to land without necessarily incurring a suit for damages or imprisonment. Judge Simeon Baldwin questions whether it will not be advisable to prescribe a mode of indicating where a landing is prohibited and where it is permitted. If, for instance, a red flag were made the sign of prohibition, it may fairly be provided, in his opinion, that to land in the face of such a warning the aviator subjects himself to an action for double damages, enforcible by his arrest. The Berlin Conference relating to wireless telegraphy imposed on all coast and shipping stations the duty of exchanging wire- less messages, regardless of the system em- ployed. A similar arrangement would probably apply to the right of air-craft to use local areas set apart for alighting, mooring, and embarka-

252 THE NEW ART OF FLYING

tion. It would seem that a distinction should be made between an accidental landing, which is due to negligence and which causes damage, and a landing which is made with all due care in order to save the airman from death. In the one case a penalty of some kind should be imposed, but in the other the airman should be allowed to escape by simply paying the amount of the actual damage which he has inflicted. Judge Baldwin has even raised the question whether the law of self-preservation cannot be invoked by an airman who is compelled to make an immediate landing to save his own life and by so doing accidentally causes the death of another.

It is certain that in order to reduce the possi- bility of accidents to a minimum only a licensed pilot will be permitted to navigate the air in the future. Judge Baldwin advises that the government issue such licenses only on the filing of a proper indemnity bond for the bene- fit of those who may suffer such accidents. He has pointed out that the same result could be obtained by compelling the owners of air- craft to take out blanket policies of accident

THE LAW OF THE AIR 253

insurance, covering all injuries occasioned by the use of the ship and authorising the injured to bring suit upon it in the name of the insured, but for their own benefit.

In European countries a tendency is shown to subject air navigation to the monopolistic control of the state. In the United States and in England private enterprises will have a freer hand, subject, of course, to strict governmental supervision by registration, license, and inspec- tion. But shall such a government license issued in one state or country be respected in another? There seems to be no good reason why it should not. Automobile licenses are so respected for a limited number of hours. Treaties and agreements will undoubtedly be drawn which will secure the recognition of air licenses by foreign governments. But to har- monise the aeronaut's rights with those of other men and those of foreign lands over which he may take his course, demands not only ade- quate local legislation but adequate interna- tional agreements. Professor Meli of Zurich, in a recent address before the International Vereinigung fur vergleichende Rechtswissen-

254 THE NEW ART OF FLYING

schaft of Berlin, strongly advocated the convening of an international conference for this purpose. Such a conference was held at Paris in 1910, but accomplished very little in the way of practical results. The British Government demanded more time for con- sideration before approving the measures of the Conference.

Although every reasonable concession will be made to the man who builds and flies air- craft, it must not be supposed that those below are altogether at the mercy of the man in the air. Every moment of an atmospheric voyage is fraught to some extent with danger to those below. If actual physical injury is sustained by a man on the ground, the civil or criminal courts may be appealed to for justice. The man who is wounded by an object dropped from an air-craft certainly has a right of action for damages, whether or not he be the owner of the land upon which he happens to be stand- ing at the time. The master and servant rule would apply here as well as in other cases. An action for damages would lie against the pilot of the flying-machine, whether he be the

THE LAW OF THE AIR 255

owner of the craft or not, or the master by whom he is employed. It is even conceivable that an injunction could be obtained to abate a nuisance caused by a fleet of air-craft travel- ling in a defined roadway day after day and week after week, so as to annoy a tenant or a property holder by their noise, odours, exhaust, and the like.

Besides these rights of the man below, whether he be a landowner or not, there are broader national questions to be considered. In a sense the state is the ultimate owner of the soil, and as such it has the right to regulate the air above its territory, and to state the con- ditions under which it will permit the naviga- tion of the air. That air-craft will sooner or later become the subject of governmental reg- ulation and authorisation seems almost self- evident when we consider the history of the railroad, the telegraph, the telephone and wire- less telegraphy. In the United States the indi- vidual states will regulate the air-craft that ply the air wholly within the state; the federal government those vessels that travel from state to state.

256 THE NEW ART OF FLYING

The international aspects of the question are somewhat more difficult to dispose of. Before the American Political Science Association, Mr. Arthur K. Kuhn suggested that the right of the craft of one nation freely to traverse the air-space of another might be compared with that of the vessel of one state freely to navi- gate the river of a coriparian state, especially when the river becomes navigable within its own territory. Dr. Hazeltine, reader in Eng- lish law at Cambridge, believes, however, that the analogies of the high seas and the maritime belt of coastal waters as applied by advocates of limited sovereignty are far from being sound and applicable. Still it is not unlikely that, in settling the international problems that must in- evitably arise in the future, some of the prin- ciples of maritime law will be applied to the navigation of the air. Because the airship, and to a lesser degree the aeroplane, may be an instrument of commerce as well as a ship sail- ing the high seas, Judge Baldwin has suggested that provision must be made for ship's papers; that the number of passengers to be carried on an air vessel must be fixed; that the qualifica-

THE LAW OF THE AIR 257

tions of those in charge must be determined; that machinery must be inspected; and that pilotage must be provided for.

Freedom of the seas is based on the impos- sibility of an effective control by any one state. It has been urged by one school of German advocates, among them Meurer, Holtzendorff, and Griinwald, that the air-space over a state is an appurtenance of it, and as such the right to navigate it is not as free as the right to navi- gate the high seas. By another school the rela- tion of the state to its overlying air-space is compared with that of its coastal waters. The abortive Convention drafted by the International Conference on Aerial Navigation of 1910 was based entirely upon the provisions of inter- national maritime law. There are the same re- quirements as to registration and nationality of air-vessels, certificates of fitness of the craft and the competence of its navigators and navi- gation in territorial waters — using the mari- time phrase for the sake of convenience — and the same regulations applying to the sojourn of alien craft in distress. It is laid down that aerial navigators must keep a very detailed

258 THE NEW ART OF FLYING

log, giving the names, nationality and domicile of all persons on board, and embodying a record of the course, altitude and all the events of the voyage. This log must be preserved for at least two years from the date of the last entry, and must be produced on the demand of the authorities. Each state would have to exercise the right of police and customs supervision in the atmosphere over its territory. It would have power to regulate passenger and goods traffic between points in its own territories, and it could prohibit navigation in certain zones of reasonable extent, indicated with sufficient pre- cision to permit of their being shown on aero- nautical charts. There is such a thing as a three- mile limit in maritime law, a limit originally set by the range of a cannon. Why then, we are asked, should there not be sovereignty within a certain zone, the height of which is determined by gun fire? The analogy and the rule re- sulting from it were strongly supported by Westlake before the Institute of International Law; but they were rejected in favour of a negative sovereignty, saving the right of self- protection. The range of Krupp ordnance,

THE LAW OF THE AIR 259

which has been especially designed for airship repulsion, would no doubt aid in determining the height of such a zone. Holtzendorff, Fau- chille, and Holland would restrict absolute sov- ereignty within a zone of isolation varying from three hundred and thirty metres (the altitude of the Eiffel Tower as the highest artificial object) to fifteen hundred metres. The topog- raphy of the earth is in itself a sufficient objec- tion to that proposal. Dr. Hazeltine has expressed the view that any theory of sover- eignty limited in height is open to the same objection as the theory of a zone of protection in which free passage is allowed to non-military craft. In his opinion the state should have full, sovereign dominion in the entire air space above its territory. Furthermore, he main- tains that the recognition of each territorial state's full right of sovereignty in the air space above it would constitute a basis for the fu- ture development of national and international aerial law, leaving, as it would, to aerial navi- gators as well as states and their inhabitants the full legal enjoyment of their proper interests. A nation's sovereignty can hardly extend

260 THE NEW ART OF FLYING

to a domain that it cannot defend from invasion. When Balboa stood upon a peak in the Andes and, surveying the Pacific, claimed in the name of Spain all the land that its waters might wash, he was as ridiculous as he was grandiloquent. Even in that age of limited geographical knowl- edge he must have felt that his country could never uphold the claim by force of arms. To be sure, it would be easier for a nation to defend all the air-space above its territory than to restrain encroachments upon land washed by the waters of a vast ocean. The maximum height at which air-craft can sail may be placed at about five miles, with the probability that the average height will be about one mile. It would not be a task of extraordinary difficulty for any nation equipped with a formidable aerial navy to police its air-space more or less effectively. Whatever zone is adopted, self-interest alone will impel each state to grant access to and passage through its air-space in time of peace, subject only to such rules as its reasonable interests may require. As to the liberty to navigate the air, the following rule was accepted at the Inter- national Conference of 1910:

THE LAW OF THE AIR 261

" Each of the contracting States shall permit the navigation of the airships of the other con- tracting States within and above its territory, reserving the restrictions necessary to guaran- tee its own safety and that of the persons and property of its inhabitants."

The restrictions referred to relate chiefly to the question of certain zones, over which, if they are properly indicated in advance, no airship may fly unless compelled to by necessity. If an aeroplane is carried by accident or by adverse air conditions over an interdicted zone, it must descend at once and indicate its disability. It must also descend if signalled to from the earth.

The matter of jurisdiction over crimes com- mitted by airmen or their passengers is likewise a matter of international concern. Fauchille has proposed that crimes committed on air-craft " fall under the competence of the tribunals of the nation to which the air-craft belongs." Ameri- can and English lawyers will object to any such principle because Anglo-Saxon law has always been territorially administered. Probably con- current jurisdiction will be agreed upon, as in

262 THE NEW ART OF FLYING

the case of crimes committed on foreign vessels in territorial waters.

Besides crimes committed on air-craft, there are also crimes committed on the ground which involve the rights of airmen. Balloons have been shot at in pure wantonness. Jurisdiction in such cases obviously belongs to the country in which the firearms were discharged. If a man is killed in a flying-machine in the United States by a bullet discharged over the border- line in Canada, there is no reason why murder has not been done in the United States and why the murderer should not be extradited and tried in a United States court.

Lastly, there remains to be considered the legal status of the airship and the aeroplane in time of war. Balloons were used in war long before the dirigible airship or the aeroplane were brought to a state of practical perfection, but they never played so conspicuous a part in military operations that it was necessary to de- fine their status according to the principles of international law. It is true that Bismarck said that an Englishman who manned a French balloon would be subject to arrest and trial

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THE LAW OF THE AIR 263

" because he had spied out and crossed our out- posts in a manner which was beyond the* con- trol of the outposts, possibly with a view to making use of the information thus gained to our prejudice." That dictum of blood and iron seems much too drastic even to German com- mentators. A spy is supposed to act clandes- tinely. An air-craft is so conspicuous an object that even though bent on ascertaining the enemy's strength and the disposition of its forces, its errand can hardly be secret. On the other hand, Mr. Kuhn has pointed out that the impossibility of flying secretly by day, at least, is in itself no reason why the use of the air- craft may not be clandestine. The Hague Peace Conference in 1907 left the matter in a very unsatisfactory condition. It provided that aeronauts were not to be regarded as spies if they carried despatches or maintained commu- nication between different parts of an army or territory, but it failed to fix the status of the reconnoitring airman. In the war of the future the aeroplane and the airship will perform much the same function as a cavalry reconnais- sance in force; yet even Bismarck would not

264 THE NEW ART OF FLYING

have shot as a spy a trooper captured on a scouting raid. The international complica- tions which may arise even at the present time will undoubtedly be considered when the next Hague International Conference takes place. The possibility that an alert military spy, float- ing serenely over a fortress which has cost a nation millions, may photograph or sketch every battery, manifestly necessitates the adop- tion of some restrictive measures. So jealously are many of the fortifications of Europe guarded from the watchful eyes of spies, that entry within their portals is granted only on certain conditions. No cameras may be taken within the lines; nor is admission granted with- out credentials. What a spy on land might be unable to discover in months by cunning, cajol- ery, and bribery, will be exposed to an aeronaut in half an hour. Some check must therefore be placed upon the scout in the air. At the Inter- national Conference on Aerial Navigation of 1910 it was proposed that a state should have the privilege of developing photographic nega- tives found on board an airship coming to earth in its territory, and if necessary to seize them

THE LAW OF THE AIR 265

and the photographic apparatus. Wireless tele- graphic instruments, too, could not be used, according to another provision, without special permission, for any other purpose than to secure the vessel's safety. Perhaps, although no Inter- national Conference has thus far suggested it, the pilots of the future will be constrained to avoid fortifications entirely, or run the risk of arrest by air sentry, — military lookouts gliding along in aeroplanes ready to act if a too closely approaching atmospheric tourist ap- pears. Arrests will undoubtedly be made by these sentinels in the air; the captured aeronaut will be asked for his credentials and will be searched for sketches that may implicate him. If he is caught red-handed, he will be punished

— how, must be determined by international agreement.

The war of the future will be a conflict of air- craft as well as of infantry and artillery. How shall the aeroplane of any warring country be distinguished from those of any other? Every ship on the high seas, whether it be merchant- man or battleship, flies the flag of its country,

— a challenge to its foes in time of war, a

266 THE NEW ART OF FLYING

badge of peace to its friends. The question of nationality brought up some interesting points during the International Conference of 1910. It was decided that it should be determined by the nationality of the owner or by his domicile. It was also voted that:

" A State may require its subject to be at the same time domiciled on its territory, or it may admit domiciled foreigners as well as its sub- jects. Airships belonging to companies must take the nationality of the State in which their head office is situated. In the case of an airship belonging to several owners, at least two-thirds must be owned by subjects of, or foreigners domiciled in, the State conferring nationality."

The Swiss delegates protested that this article would permit the establishment of many foreign airships in one nation without the supervision of their own, and then drew attention to a sugges- tion already made by them that no nationality be attributed to airships, but that each airship be compelled to acknowledge a " certain port of register or domicile." This system, the Swiss believe, " offers, from the point of view of the safety of States, guarantees very superior to

THE LAW OF THE AIR 267

those secured by the system of owner's na- tionality." But the Swiss proposal was rejected.

Fully as important as these considerations are the rights of neutral air-craft in time of war. If France and Russia are at war, has Germany the right to prevent the v vessels of either nation from crossing her boundaries be- cause her neutrality is violated? The right of exclusion is absolute, if no neutral zone be agreed upon internationally. But if a free zone be agreed upon, the aerial equivalent of the maritime three-mile limit, have belligerents the right to engage in battle over neutral ter- ritory with a possibility of injuring those below? There is such a force as gravitation and with that force airships and aeroplanes must constantly reckon.

Will the air-craft that seeks refuge on neutral ground or in neutral air be compelled to leave within a stipulated time, as in the case of a warship that seeks refuge in a neutral harbor? Will an air-craft so badly injured that it cannot leave, even when ordered to do so, be disarmed?

The military reports of the question were discussed at the International Conference of

268 THE NEW ART OF FLYING

1910, but more with regard to the status of air-craft in time of peace than in time of war. The departing or landing of military airships of one state in the territory of another was prohibited, unless with the authorization of the state whose territory is involved; -while each contracting state was at liberty to pro- hibit or regulate in accordance with its interests the passage over its territories of military air- ships belonging to other contracting states. A clause in the Convention relating to the extra- territoriality of military airships and their crews while within the limits of jurisdiction of a for- eign state, appears not to have met with the full approval of the delegates of several Powers, Great Britain and Austria being among those who reserved their adhesion. The Convention stipulated that nothing it contained should in- terfere with the liberty of action of belligerents or with the rights and duties of neutrals. As bearing on this point, it is of interest that all the participating nations agreed that the aerial transport of explosives, firearms, ammunitiqn, and carrier-birds must be forbidden.

GLOSSARY

Adjusting Plane or Adjusting Surface: A surface of small area for regulating lateral stability; usually located at the side edge or rear edge of a supporting plane. It is to be distinguished from an aileron (q. v.) in that it is capable of adjustment but not of inde- pendent movement by special operating devices.

Advancing Edge: See Entering Edge.

Advancing Surface: The forward supporting sur- face of a machine provided with supporting planes in tandem, as in the Langley aerodrome, or with super- posed surfaces arranged in step formation.

Aerocurve: Any arched supporting surface. The term has been proposed because few supporting sur- faces are true aeroplanes. See also Aerofoil.

Aerodrome: A term invented by the late Prof. Samuel P. Langley and used by him to designate an aeroplane flying-machine. Etymologically the term signifies " air-runner." It is more commonly used to designate a flying-course by analogy with " hippo- drome." Mr. F. W. Lanchester and Dr. Alexander Graham Bell have sought to restrict the term to th& use which Langley intended.

Aerodromics: Langley 's term for the science and art of flying with an aeroplane flying-machine.

Aerofoil: The supporting surface of a flying- machine, coined, like Aerocurve, because the sup- porting surfaces of a flying-machine are not, strictly speaking, flat planes.

270 GLOSSARY

Aeronaut: One who navigates the air.

Aeronautics: The science of aerial navigation.

Aeronef: A term invented in France and intro- duced into English-speaking countries to designate any heavier-than-air flying-machine. The term is not much employed either in French or in English.

Aeroplane: Any plane surface propelled through the air. The term was invented before it was discovered that curved surfaces are better than flat surfaces. Hence it is not strictly applicable to modern support- ing surfaces.

Aileron: A French word meaning " winglet," in- troduced into English to designate any freely swinging surface controlled by the aviator and designed to main- tain lateral stability. Ailerons may be either tips hinged to the side edges or rear edges of the main supporting surface, or they may be small independent planes. See also Adjusting Surface, Balancing Plane or Surface, Stabiliser, and Wing-Tip.

Airship: A term originally employed to designate any aerial craft, whether heavier or lighter than air, but now restricted by the best writers to dirigible balloons.

Air Speed: The velocity of a machine in the air as distinguished from its velocity on the ground.

Airman: An aeronaut; one who navigates the air.

Alighting Gear: The wheels or skids or combina- tions of both on which a machine alights. See Skids.

Angle of Attitude: See Angle of Incidence.

Angle of Entry: The angle formed by a tangent to the entering edge with the line x>f motion.

Angle of Incidence: The angle made by the main

GLOSSARY 271

planes with the line of travel. Sometimes called " angle of attitude " and " angle of attack." The angle may be positive or negative, depending on the direction in which the plane is turned to the line of flight.

Angle of Trail: The angle formed by a tangent to the rear edge with the line of travel in curved sup- porting surfaces.

Apteroid: Lanchester's term for a short, broad form of wing.

Arch: The downward curve or droop to the ends of supporting surfaces.

Aspect: The top plan view of an aeroplane flying- machine.

Aspect Ratio: The ratio of the length to the width of a plane or curved supporting surface.

Aspiration: The suction produced by a current of air which strikes a curved supporting surface.

Attitude: See Angle of Incidence.

Automatic Stability: See Stability.

Auxiliary Surface: See Supplementary Surface.

Aviation: Flight with heavier-than-air machines as distinguished from ballooning.

Aviator: The pilot of a heavier-than-air machine.

Balance: The maintenance of equilibrium by means of balancing surfaces. A distinction is sometimes made between Balancing and Stabilising (q. v.).

Balancing Plane or Balancing Surface: A surface for establishing and maintaining equilibrium as well as to assist in turning. Such surfaces may be operated either automatically or by hand; they maintain both longi- tudinal and lateral balance.

Beat: A periodically recurring movement in a pro- peller blade or in a wing of a flapping-wing machine.

272 GLOSSARY

Biplane: A flying-machine with two superposed sup- porting surfaces.

Body: See Fuselage.

Box-Kite: A kite invented by Hargrave and pro- vided with two parallel vertical and two parallel hori- zontal surfaces in the form of an open box.

Brace: A compression member.

Camber: The curve of a supporting surface meas- ured from port to starboard.

Caster-Wheel: A small wheel of the alighting gear, so pivoted that, like the caster of a chair, it automati- cally suits itself to the direction of the flying-machine's motion on the ground.

Carburetter: An apparatus by which air is charged with a hydrocarbon so that it will either burn or ex- plode. In the gasoline flying-machine motor it serves the purpose of mixing the gasoline vapor with air in the right proportion to form an explosive when ignited.

Chassis: The under framework of a flying-machine.

Cell: An open box-like unit. Its parallel vertical and parallel horizontal surfaces serve to maintain stability.

Centre of Effort: The point in which the effect of an axially exerted force is theoretically concentrated, as, for example, the thrust of a propeller.

Centre of Gravity: A point in which the weight of a flying-machine is theoretically concentrated.

Centre of Lift: See Centre of Pressure.

Centre of Pressure: An imaginary centre in which the air pressure on a supporting surface is theoretically concentrated.

Centre of Thrust: See Centre of Effort.

GLOSSARY 273

Chord: The line connecting the ends of the segment of a circle.

Compound Control: A system of hand-levers and ropes or hand-wheels and ropes by which two con- trolling operations are simultaneously carried out with but a single operating device, as, for example, the single lever in a Wright machine, which serves not only to warp the main planes, but also to swing the vertical rudder at the same time.

Compression Side: The side of a surface, such as an aeroplane or air-propeller, which faces the flow of air current.

Curtain: A vertical plane, as in the Voisin cellular biplane, between the main planes, serving to insure a certain amount of lateral stability.

Diagonal: A diagonal brace in a framework.

Derrick: A pyramidal structure from the top of which a weight can be mechanically dropped in order to start a flying-machine in motion on a rail. Some- times called a " pylon."

Dihedral Angle: The angle formed by two planes placed at opposite sides of a median line, so as to form a very wide " V."

Double-Decker: A synonym of biplane (q. v.).

Double Monoplane: A machine having two sets of supporting surfaces arranged in a single tier. Such a machine is also called a " following-surface " machine.

Double Rudder: A rudder having two surfaces of more or less similar surface and outline, which sur- faces may or may not act simultaneously.

Doubled-Surfaced: Covering both sides of the framework of a supporting surface.

274 GLOSSARY

Drift: The resistance offered to forward motion of a plane or curved surface in the air by the horizontal component of the air pressure against the plane. It is to be carefully distinguished from mere head resist- ance (q. v.).

Elevator: The horizontal rudder of a flying-machine, used for steering in a vertical plane.

Entering Edge: The front or leading edge of an aeroplane.

Equilibrator: The tail of a flying-machine.

Equilibrium: In flying-machine parlance the term is used in the same sense as " stability." Properly speaking, an aeroplane is in equilibrium when travelling at a uniform rate in a straight line, or, again, when it is steered around a horizontal arc or circle. It is necessary for stability that if the aeroplane be not in equilibrium and moving uniformly it shall tend toward a condition of equilibrium.

Equivalent Head Area: The area which would offer head resistance equal to that of the supporting sur- faces of a flying-machine plus the struts, stays, wires, chassis, etc.

Feathering: Said of surfaces which are manoeuvred in a manner to pass edgewise and flatwise in alternate directions while in motion.

Fin: A rigid vertical surface which acts somewhat like the keel of a sailing yacht.

Fish Section: A section resembling in shape the body of a fish. Such sections are commonly found in flying- machine struts.

Fixed Wheel: In contradistinction to a caster-wheel (q. v.), a wheel that always preserves its relative posi- tion in the alighting-gear.

GLOSSARY 275

Flapping-Wing Flight: Flight by means of beating wings as distinguished from flight obtained by means of rigid aeroplanes. See Ornithopter.

Flexible Propeller: A fabric propeller, capable of adjusting itself in flight.

Flying Angle: Flying attitude. See Angle of Incidence.

Following Edge: The rear edge of an aeroplane surface.

Following Surface: The rear surfaces of two similar surfaces arranged in tandem.

Fore-and-Aft: Longitudinally.

Front Control: Front Rudder: The framework and planes situated at the extreme front of the aeroplane, in advance of the operator.

Fusiform : Spindle-shaped.

Fuselage: The framework or body of an aeroplane.

Gap: The distance between two planes in a multi- plane machine.

Glide: To travel without power.

Glider: An aeroplane without a motor.

Gliding Angle: The angle at which a machine glides down without power.

Ground Attitude or Incidence: The difference in the angle formed by the aeroplane surface when on the ground and when in flight.

Guy-Wire: A wire connecting two members of an aeroplane, usually parts of the controlling system.

Gyroplane: A flying-machine with rotating planes. See Heliocopter.

Gyroscope: A freely-hung, rapidly-rotating fly-wheel, which resists forces that tend to throw it from its plane of rotation.

276 GLOSSARY

Hangar: A term said to be of Hungarian origin, now also used in English, to designate a shed for hous- ing aeroplanes or airships.

Head Area: The total head resistance offered by the entire framework of an aeroplane.

Head Resistance: The resistance a surface offers to movement through the air.

Heavier-than-Air: A term applied to all air-craft not sustained by a buoyant gas.

Helicopter or Helicopter e: A heavier-than-air ma- chine in which flight is secured by lifting screw pro- pellers revolving in more or less horizontal planes.

Helix: The path of a point moving uniformly around a cylinder and uniformly along the cylinder.

Horizontal Rudder: See Elevator.

Keel: The under framing of an aeroplane to stiffen it both laterally and vertically. Sometimes used as a synonym of fin ( q. v. ) .

Land Speed: The rate of travel of an aeroplane on the ground before ascension.

Landing Area: A special allotment of ground on which a machine can land safely.

Landing Skid: See Skid.

Lateral: A strut for side wise bracing in the frame- work of an aeroplane.

Lateral Stability: Lateral equilibrium in the side-to- side direction.

Lattice Girder: A girder with many crossed mem- bers, resembling in appearance a lattice window.

Leeway: Lateral drift in the direction in which the air current is flowing due to the air current.

Lift: The ascensional force of an aeroplane surface.

Longitudinal Stability: Lengthwise stability.

GLOSSARY 277

'Magneto: An apparatus for generating electric cur- rent to produce a spark wherewith to ignite the explo- sive mixture in the cylinder of an internal-combustion motor.

Main Plane: The largest supporting wing in a multiplane.

Mast: A spar or strut for fastening trussing wires or stays to stiffen the planes.

Monoplane: An aeroplane with one or more sup- porting surfaces, all in the same plane.

Monorail: A rail used as a track in starting some machines.

Multiplane: An aeroplane with more than one main supporting surface.

Nacelle: See Fuselage. In some monoplanes the en- closed, boat-like part of the body, containing the seat for the pilot and his passenger.

Negative Angle of Incidence: The angle formed by a plane inclined downwardly to the direction of travel.

Ornithopter, Ornithoptere, Orthopter, or Orthop- tere: A machine which attains flight by bird-like flap- ping of wings.

Orthogonal Action: The vertical reaction of the air in affording equilibrium by means of wing motion.

Panel: The vertical planes in a box-like or cellular structure.

Pendular Movement: To-and-fro movement like that of a pendulum.

P hug old: Lanchester's designation for the undulat- ing course naturally adopted by plane surfaces when moving in the air.

Pitch: The forward movement that would be pro- duced by one turn of a propeller in a solid.

278 GLOSSARY

Plane: Literally a flat surface; in aeroplanes a flat or curved surface.

Poly plane: See Multiplane.

Pylon: The tower required by some types of aero- planes to start. Also, the pillars that mark a definite course to be taken by a flying-machine at a flying- machine meeting.

Radiator: A coil of piping or any circuitous conduit in which water is cooled by radiation after having cir- culated around the hot cylinder of an internal com- bustion engine.

Rarefaction Side: The side opposite the compression side, as, for example, the top of an aeroplane in motion.

Reactive Stratum: The compressed or rarefied layer of free air flowing along an aeroplane surface.

Rear Control: A stabilising tail surface which may also be a rear horizontal rudder.

Rising Angle: The maximum angle of ascension.-

Rudder: A horizontal or vertical plane used for steering.

Runner: See Skids.

Screw: A propeller.

Single-Decker: A monoplane.

Single-Surfaced: Aeroplane surfaces covered only on one side. Compare with Double-Surfaced.

Skids: Runners underneath some types of machines, used for landing.

Skin Friction: The friction of the air against sur- faces.

Slip : The difference between the pitch of a propeller and its actual forward travel.

Soaring Flight: Flight with rigid wings.

Spar: A strut, a brace, etc.

GLOSSARY 279

Stability: Maintenance of balance in flight by auto- matic devices such as a shifting weight or a gyroscope (q. v.) ; or hand-operated devices such as ailerons, wing- tips, and plane-warping devices.

Stabilise: To maintain equilibrium by means of surfaces and not by mechanism.

Stabiliser: The tail of a flying-machine.

Stabilising Plane: A surface for the maintenance of equilibrium ; small horizontal planes hinged to the main planes, and suiting the angle of the wind.

Starting Frame: See Chassis.

Starting Rail: See Monorail.

Stay: A brace or wire in an aeroplane framework.

Steadying Vane: Small vertical planes, usually placed in the front control of the old Wright machine.

Straight Pitch: In propellers, a flat instead of a helical blade surface.

Strainer: A turnbuckle.

Strut: A compression member in a structure. In biplanes the posts separating the main planes.

Supplementary Surface or Auxiliary Surface: A small surface such as an aileron or wing-tip, which acts in unison with a larger one for a specific purpose.

Supporting Surfaces: The main planes.

Tail: A collective term for the framework and planes in the rear of the main plane.

Tail Planes: The rear planes supported by the tail framework.

Tail Wheel: A small wheel under the tail of some machines to support the tail on the ground.

Tie: A tension member in a framework; used also for wire stays.

Tractor Screw: A propeller set in front of the sup-

280 GLOSSARY

porting surface instead of in the rear, so that the ma- chine is drawn through the air and not pushed.

Triplane: An aeroplane with three superposed sup- porting surfaces.

Turnbuckle: A combined right and left-hand screw for taking up the slack in a loose wire stay.

Up-Wind: Moving against the wind.

Variable Pitch: In propellers, a varying angle of blade width in contradistinction to uniform pitch.

Vol-Plane: See Glide.

Wake: The wash of an aeroplane in flight.

Warping: The act of twisting a plane for the main- tenance of equilibrium.

Wash: See Wake.

Wing Arc: The arc described by a moving wing.

Wing-Bar: A longitudinal strip so placed as to strengthen an aeroplane surface.

Wing Section: The longitudinal curvature with re- lation to the arc of travel.

Wing-Skid: A runner under a wing-tip.

Wing-Tip: The hinged outer side of a plane.

Wing-Wheel: A wheel under a wing-tip to support the wing when the machine strikes on the ground.

INDEX

ACCIDENTS

perils of flight, 161

AEROCURVES (See Aeroplanes, Entering Edge, Lift, and Planes)

AERODYNAMICS

empirical formulae, 27; laboratories and their work, 38; towing carriage, 39; Eiffel's experiments, 39; whirl- ing tables, 40; relative ad- vantages of fixed and moving models, 40; Gottingen studies, 41; propeller-thrust tests, 106

AEROLOGY (See Meteorology)

AEROPLANE (See also Entering Edge, Planes, Lift, Drift)

definition, i; compared with kite, 2; with screw- propeller, 96; military uses, 185; dirigible airships vs. aeroplanes in war, 202; aero- plane of the future, 236, 240

AILERONS (See also Stability)

use in maintaining stabil- ity, 61, 75; Farman system, 69; early Antoinette system, 73; use in turning, 88

AIR

relation of scientific study of air to flight, 133 et seq.; study by de Bort at great heights, 140; charting ocean of air, 153 et seq., 241; dangers of unsteady air, 163 et seq.; air resistance and effect on structure of machines, 177, 1 80; military command of the air, 186, 206; effect of rarefied air on engines, 205

AIRSHIPS IN WAR (See Explo-

sives, Hague Peace Conference, and War)

ALBATROSS

aspect ratio, 16

ALIGHTING

birds and machines com- pared, 13; alighting at high speed, 36; use of wheels and shock absorbers, 55, 167; skids, 55; brakes, 57; dangers, 167, 179; alighting gear of Farman, 56, 219; of Sommer, 56; of Santos-Dumont, 56, 229; of Antoinette mono- plane, 56, 223; Wright alighting gear, 213; Curtiss' alighting gear, 216; Bleriot XI alighting gear, 227; alight- ing grounds of the future, 237; landing on warships, 238; legal aspects of com- pulsory landing, 251

ALLARD

ornithopter experiments, 24

ANEMOMETER

use in meteorology, 134,

139

ANTOINETTE (See Monoplanes,

Motors, Stability) ANZANI MOTOR (See Motors) ARCHITECTURE

effect of flying on building design, 237 ARMENGAUD PRIZE

won by Farman, 89 ARTILLERY, AERIAL (See Ord- nance) ASSMANN, RICHARD

meteorological studies, 137, 143, 144, 149, 154, 156, 158, 159

282

INDEX

ASPECT RATIO

in birds, 16; in biplanes and monoplanes, 16; relation to entering edge and lift, 27 ATMOSPHERE

its purpose, 133; results of study, 146; isothermal stratum, 151; permanent- inversion layer, 151 AUBRUN

in Circuit de I'Est, 131 AUTOMOBILE MOTORS (See

Motors) AUTOMOBILES

motor-car guns, 198; Ehr- hardt car, 200

BALANCING (See Stability)

BALANCING-PLANES (See Sta- bility)

BALDWIN, SIMEON

on law of the air, 251, 252, 256

BALLOONS IN WAR (See Explo- sives, Hague Peace Conference, and War)

BALLOONS, SOUNDING

use in meteorology, 136, 139, 143 et seq.

BANKING (See Steering and Gravitation)

BAROMETER

its use in flying, 134

BAROTHERMOGRAPH

meteorological use, 140

BELLENGER, CAPTAIN

performances as an air- scout, 192, 194

BIPLANE

distinguished from mono- plane, 15, 16, 208; structural advantages, 17; defects of its double surface, 18; relative perfection of monoplane and biplane, 18; compared with skate, I; control of center of air-pressure on Wright machine, 8, 210; tailed and tailless Wright biplanes, 9, 17,

95, 98, 103, 105, 209; small wings of Wright racers, 36, 209, 213; alighting gear of Wright machine, 55, 213; of Farman, 56, 219; of Sommer, 56; _of Curtiss, 57; of old Voisin, 57; structure of Wright machine, 63, 77, 209; structure of Curtiss biplane, 65> 77, 92> 2I4J structure of Farman machine, 69, 74, 77, 105, 217 et seq.; Voisin (old tyPe)> 74; Voisin (new type), 75> 77) 78> I05; structure of Sommer machine, 77, 220 et seq.; structure of Breguet machine, 78; structure of Voisin (new type), 78, 105; structure of Goupy, 78; struc- ture of Caudron Freres, 78; margin of safety, 172 et seq.

BIRDS

relation to aeroplanes, 2, 5, 9; launching devices of birds, 10, 45; vultures in open cages and reason therefor, 12; birds and machines in alight- ing, 13; efficiency, 15, in, 113; proportions and shapes of wings, 16, 27; Lanchester on bird flight, 113

BISMARCK

on air-spies, 262

BlTTERFELD

aerological observatory, 158 BLACKSTONE

on ownership of the air, 248 BLADES, PROPELLER (See Screw) BLERIOT, Louis (See also Mono- planes)

his use of the dihedral angle,

74; his cross-Channel flight,

112, 239; his experiences, 225

BLUE HILL OBSERVATORY (See

Rotch, A. Lawrence) BOATS

comparison of wind effects on boats and planes, 35 BOMBS (See also War)

as an offensive weapon, 186

INDEX

283

BRAKES

use in alighting, 57 BRETT, MASTER OF THE ROLLS,

on law of the air, 248 BREWER, R. W. A.

his aeroplane of the future, 236 BRYAN, G. H.

on equilibrium and stabil- ity, 1 68

CAMBER

of propellers, 96 CAUDRON FRERES (See Bi- planes}

CANNON, AERIAL (See Ordnance} CANTING (See Gravitation, Steer- ing) CENTRIFUGAL FORCE

its effect in steering, 87; in screw propellers, 95 CHANUTE, OCTAVE

his gliders, 7, 19, 42; his use of the truss, 17; his de- scription of Wright Brothers' learning to turn, 89 CHAUVIERE PROPELLERS (See - Screw} CHAVEZ

cause of death, 176; acci- dent at Nice, 233 CIRCUIT DE L'EST

motor trouble, 130; physi- cal endurance test, 165 CLEMENT-BAYARD MOTORS (See

Motors) COKE UPON LITTLETON

ownership of the air, 248 COMPASS

for aerial use, 234 CONDOR (See also Birds)

efficiency as a flying ma- chine, 112 CORNU

his helicopter, 23 CRIME IN THE AIR (See Law,

Aerial CROCHON

cause of his death, 232

CURTISS, GLENN H. (See also Biplane, Monoplane, and Motors Hudson River flight, 160, 165

DAEDALUS

his ornithopter, 23 D'AMECOURT, PONTON

relation to helicopter, 21 ^ DANGERS OF AIRMEN (See Acci- dents) DA VINCI, LEONARDO

his ornithopter, 24; his screw propeller, 94 DE BORT, TEISSERENC

meteorological studies, 137, 140, 143, 144, 149 DELAGRANGE

cause of death, 176 DE LA HAULT, ADH.

ornithopter experiments, 24 DE LA LANDELLE

his relation to helicopter, 21 DE LA ROCHE, BARONESS

accident at Reims (1910), 172

DIHEDRAL ANGLE (See Sta- bility) DIRIGIBLE AIRSHIP IN WAR (See

War} DOVER

wind surf, 164 DUCKS

their difficulty in starting, ii Du TEMPLE

his propeller, 99

EAGLE

compared with kite, 2; how launched in flight, 10 EHRHARDT AUTOMOBILES (See

Automobiles) EIFFEL

aerodynamic experiments,

ELY

his landing on deck of war- ship, 238 ENGINES (See Motors)

284

INDEX

ENTERING EDGE

relation to lifting power, 27; Lilienthal's investigation, 28; Phillip's study, 28; Langley's results, 28; Wright Brothers' studies, 28

E. N. V. MOTORS (See Motors) EQUILIBRIUM (See also Stability) of yachts and aeroplanes, 3; distinguished from stabil- ity, 1 68 ERICSSON

his marine propeller, 99 ESNAULT-PELTERIE, ROBERT his stability control system,

EXPLORATION

geographical and topo- graphical value of the flying- machine, 235 EXPLOSIVES

use on aeroplanes, 186; shrapnel for repelling attack, 20 1

FARMAN, HENRY

his launching device, 53;

use and abandonment of

early Voisin biplane, 75;

winning of Armengaud prize,

89; influence of Wright

Brothers, 217 FAUCHILLE

on permissible altitude,

2S°> 2S9> criminal aerial

jurisdiction, 261 FIAT MOTORS (See Motors) FLAPPING-WING MACHINES (See

Ornithopters) FLY-WHEEL

its function, 115,' 117;

rotary engines as fly-wheels,

127

FRICTION (See Skin Friction) FRIEDRICHSHAFEN

observatory, 138, 159 FUEL (See Petrol and Gasoline) FUTURE, FLYING-MACHINE OF

THE, 231 et seq., 240, 242

GASOLINE

its use as a fuel, 115, 117 GLIDING

its relation to safe flight, 18, 189 GLOSSOP MOOR

aerological observatory, 138 GNOME MOTORS (See Motors) GOULD, EDWIN

prize for multimotor ma- chine, 182

GOUPY (See Biplanes) GRAVITATION

its part in aeroplane flight, J» 4» 3i» 59; in steering, 87 GRAVITY, CENTER OF

relation to center of air pressure, 4; shifting center of gravity to maintain bal- ance, 5, 8; in Lillienthal's machine, 6; in Pilcher's machine, 7; in Chanute's gliders, 7; relation to stabil- ity, 85 GRUNWALD

on international law of the air, 257

GUNS, AERIAL (See Ordnance) GYROSTAT

its use in automatically maintaining balance, 80, 82

HAGUE PEACE CONFERENCE

on use of bombs, 187; on spies in the air, 263 HARGRAVE, LAWRENCE

ornithopter experiments, 24 HAZELTINE

on international law of air, 256, 259 HELICOPTERS

principle of screw-fliers, 20; d'Amecourt and de la Lan- delle, 21 ; Renard's screw- flier, 22; Edison's helicopter, 22; Berliner's helicopter, 23; Cornu's helicopter, 23; Bre- guet, 23; Kress, 102 HELIX (See Screw)

INDEX

285

HENSON

his propeller designs, 99 HERRING

determination of effect of wires and struts on speed, 34; invention of skids, 55

HOLTZENDORFF

on international law of the air, 257, 259

HOUBERNAT GUN (See Ordnance} HYGROMETER

use in meteorology, 134, 139

INCIDENCE, ANGLE OF

maintenance of horizontal flight by adjustment of angle of incidence, 31, 59, 60; cause of variations in the angle, 32; gyrostat and angle of incidence, 80 INSELBERG

Aerological Observatory,

T IS8

INSURANCE

Baldwin on accident in- demnities, 252

INTERNATIONAL CONFERENCE ON AERIAL NAVIGATION (See Paris Conference)

ISOTHERMAL STRATUM (See At- mosphere)

JEFFRIES

meteorological studies, 136

KEELS (See also Stability)

their stabilizing effect, 75

KITES

kites and aeroplanes com- pared, 2; stability of kites and manner of maintaining it, 9; launching, 9; stability of box and single-surface kites compared, 16; use in meteorology, 136, 139, 142, 143

KRESS

his propeller system, 102 KRUPP AERIAL ARTILLERY (See

Ordnance) KUHN, ARTHUR K.

on international law of the air, 236 et seq.', spies in the air, 263

LANCHESTER, F. W.

on automatic stability, 76; on speed, 236 LANDING (See Alighting) LANGLEY, SAMUEL PIERPONT

comparison of eagle and aeroplane, 10; his launching experiments, 12, 42; ex- periments with planes, 16; determination of lift of aero- curves, 28; determination of power ratio for given speed, 33, 243; his trials with large aerodrome, 49; newspaper derision, 50; use of the dihe- dral angle, 74; adoption of rear horizontal rudder, 78; his propellers, 100, 107; study of bird efficiency, in; motor designs, n6j wind studies,

T l63

LARK

aspect ratio, 16

LATHAM, HUBERT (See also Monoplanes)

at Belmont Park (1910), 224; accident at Nice, 233

LAUNCHING

necessity of preliminary run, 9, 10, 42; methods of getting up preliminary speed, 12, 44; Langley's experi- ments, 12; Wright Brothers' methods, 12; wheels for launching, 12, 13; Langley's difficulties, 42; Wright start- ing derrick and rail, 52; power consumed in launching,

e; adoption of wheels by irtiss and Farman; Wright

286

INDEX

adoption of wheels, 54; gyro- stats and their effect, 80; launching grounds of the future, 237

LAW, AERIAL

adaptability of common law, 246; salvage, 247; own- ership of air, 248; code of Canton of Grisons, 249; German Civil Code, 249; permissible altitude, 250, 258; trespass, 250; com- pulsory alighting, 251; li- censes, 253; international aspects, 253, 256 et seq.; aerial equivalent of maritime three-mile limit, 258; crimi- nal jurisdiction, 261; spies in the air, 263; rights of neutrals, 267

LEBLANC

in Circuit de I'Est, 131; at Havre (1910), 166

LEBLON, HUBERT

cause of death, 182, 233

LEVAVASSEUR (See also Mono- planes [Antoinette]) propeller mounting, 100

LICENSES

Baldwin on licenses, 252

LIFT

relation to entering edge, 27; to angle of incidence, 31; Maxim's experiments, 28; Phillip's work, 28; Langley's studies, 28, 34; Wright Broth- ers' studies, 28, 34; effect of turning on lift, 87

LIGHTHOUSES

beacons for aviators, 234

LlLIENTHAL, OTTO

cause of his death, 5; his gliders, 6, 8, 19, 42; experi- ments in determining lifting effect, 28

LlNDENBERG

Aeronautical Observatory, 138, 154, ISS, 156

LlNDPAINTNER

In Circuit de FEst, 131

LlNFIELD

his propeller design, 99 LINKE

his aeronautic weather ser- vice, 155 LUBRICATION

of motors, 124, 128

MACOMB, MAJOR

on Langley's aerodrome, 49 MAPS

use by aviators, 160 MAXIM, SIR HIRAM

experiments on lift of curved surfaces, 28; pro- peller designs, 100, 101, 107 MEURER

on international law of

on law of the air, 247, 253 METALLURGIC (See Motors) METEOROGRAPHS (See Mete-

orology) METEOROLOGY

relation to flying, 133 et seq.\ dates for international aerological investigations, 145 MEUNIER, GENERAL

on aerial scouting, 190 MILITARY USES OF FLYING MACHINES

aeroplane in war, 186 et seq. MILLER, WARREN H.

his table of motor efficien- cies, 131 MODELS

relative advantages of fixed and moving models in re- search work, 40 MOISANT

cross-Channel flight, 164 MONOPLANE

compared' with skate, i; distinguished from biplanes, 15; structural defects, 17; advantage of its single sur- face, 18; relative perfection of monoplane and biplane,

INDEX

287

1 8; speed of Bleriot, 35; alighting gear of Antoinette, 56, 223; of Pelterie, 57; Bleriot construction, 70, 78, 100, 105, 225; Antoinette construction, 72, 75, 78, 100, 105, 222; use of dihedral angle by Langley and Bleriot, 74; Hanriot monoplane, 76; Santos-Dumont monoplane, 92, 100, 228; Curtiss mono- plane, 217; margin of safety, 172

MORANE

at Havre meeting (1910), 166

MOTOR-CAR GUNS (See Auto- mobiles)

MOTORS

relation to speed, 17; to angle of incidence, 32; di- minishing power required with increasing speed (Langley's law) 33; power consumed in starting machine, 53, 54; low power of early Wright motors, 54; relation to pro- pellers, 108; efficiency, in, 116, 129, 205; Anzani, 112, 132, 226; Wright, 112, 116, 129, 132, 213; 4-cycle princi- ple, 113; lightness, 117, 232; cylinder arrangements, 117; lubrication, 124; radial en- gines, 124; Gnome motors, 126, 127, 129, 132, 219, 220, 224, 227; Antoinette motors, 129, 132, 224; Fiat motors, 129; Metallurgic, 129; Re- nault, 129; automobile mo- tors, 129, 224; E. N. V. motors, 13 2; Clement-Bayard, 132, 230; Curtiss, 216; R. E. P. motors, 132; motor-break- downs, 182, 205; effect of rarefied air on compression,2O5

MOY

his fan-propeller, 99

MT. WEATHER OBSERVATORY its functions, 137

MULTIPLANE

triplanes, 19, 20; Phillips, 20

NEUTRALITY IN AIR WARFARE (See Law, Aerial)

ORDNANCE, AERIAL

for repulsion of aerial at- tacks, 196; Krupp guns, 197 et seq., 258; Rheinische Metallwaaren und Maschi- nenfabrik (Dlisseldorf) aerial guns, 199, 201; Houbernat gun, 200; machine-guns on aeroplanes, 202, 204; range of Krupp guns to determine neutral zone, 258

ORNITHOPTERS

underlying principle, 23 ; Leonardo da Vinci's, 24; Allard's experiments, 24; Har- grave's models, 24; de la Hault's experiments, 24; dis- advantages of the type, 25

OTTO ENGINE (See Motors)

PARIS CONFERENCE

international law of the air, 253, 260, 266, 267 PATENTS

Wright patents and their scope, 67, 68, 69, 70, 75; Wright pendulum patents, 79 PAVIA

Aerological Observatory,

T,'38

PAVLOVSK

Aerological Observatory,

T,'38

PENDULUM

Wright automatic pendu- lum for stabilizing, 79; faults of the pendulum as an auto- matic control device, 81

PERMANENT INVERSION LAYER (See Atmosphere)

288

INDEX

PETROL

as a motor fuel, 115, 117 PHILLIPS, HORATIO

his multiplane, 20; study of lifting effect of curved planes, 28 PHOTOGRAPHY

the camera in war, 189, 264; in exploration, 236 PICQUART, GENERAL

on aerial scouting, 190

PlLCHER

his death, 7; gliders, 42, 170 PITCH

definition, 96

PLANES (See also Lift, Entering Edge)

Proper shape and size, 16; relation to hull of a ship, 26, 27; entering edge and lift, 27; Lilienthal's results, 28; Wright Brothers' studies of aerocurve lifts, 28; Phillips study of lifts, 28; force act- ing on plane in motion, 31; angle of incidence and speed, 31; relation of power to speed, 33, 243 (Langley's law); speed and size of planes, 36; reefing wings, 37; aerodynamic studies, 38; margin of safety, 172

POLIS

his aeronautic weather ser- vice, 155

POWER (See Motors)

PRANDTL

aerodynamic work at Goet- tingen, 41; exposure of pen- dulum defects for automatic control, 82; study of form for airship gas bags, 227

PRESSURE

relation of pressure to entering edge, 28; aero- dynamic study of pressure, 38; pressure and support of machine in flight, 59; effect on construction, 177

PRESSURE, CENTER OF

relation of center of gravity to, 4; shifting center of pres- sure to maintain balance, 5; in Lilienthal's glider, 6; in Pilcher's machine, 7; in Chanute's glides, 7; in Wright machines, 8; automatic con- trol, 9

PROJECTILES (See Explosives')

PROPELLERS (See Screw)

PTERODACTYL

efficiency compared with flying machine, in

RACING

its effect on commercial development of aeroplane, 240 RADIATORS

in motors, 116 RAILS IN LAUNCHING (Set

Launching) RECONNAISSANCE

scouting aeroplanes, 189, 190 REGNARD, PAUL

his gyrostatic system of control, 80 REIMS

meeting of 1910 and speeds attained, 35; accidents, 172, ^176, 179 RENARD, COLONEL

his combined aeroplane and helicopter, 22

RENAULT MOTORS (See Motors) R. E. P. (See Esnault-Pelterie

and Motors')

RESISTANCE (See Pressure) RHEINISCHE METALLWAAREN UNO MASCHINENFABRIK AE- RIAL ARTILLERY (See Ord- nance) RHINOW

Lilienthal's experiments at, 6

ROLLAND

on international law of the air, 259

INDEX

289

ROLLS, C. S.

cause of death, 171, 176

ROTCH, A. LAWRENCE

meteorological studies, 137, 141

RUDDERS, HORIZONTAL (See also Steering)

their purpose, 13, 167; Wright system, 64, 77, 210; Curtiss system, 65, 77, 214; Farman system, 69, 77, 218; Bleriot system, 72, 226; An- toinette system, 72, 223; stabilizing effect when used as tails, 77; Langley system, 78, 129; Sommer system, 220; Santos-Dumont (De- moiselle) system, 229

RUDDERS, VERTICAL (See also Steering)

their necessity, 13; use in maintaining stability as taught by the Wrights, 63; Curtiss system, 65, 215; Farman system, 69, 219; Bleriot system, 72, 226; An- toinette system, 72, 223; Wright system, 210; Santos- Dumont system, 229; effect of vertical rudder in steering, 92; types of vertical rudders, 92

SAFETY (See Occidents)

SALVAGE (See Law, Aerial)

SCOUTING

aeroplane reconnaissances, 189, 190

SCREW

lifting propellers in heli- copters, 21 ; inefficiency of screw, 94, 106, 108; da Vin- ci's screw, 94; principle of screw, 95 et seq.; Ericsson's marine propeller, 99; Moy's fan propeller, 99; Henson's propeller, 99; Stringfellow's propeller, 99; Linfield's pro- peller, 99; du Temple's pro- peller, 99; Langley's pro-

pellers, 100; Maxim's pro- pellers, ico; Kress system, 102; Wright system, 103, 109; Chauviere, 104, 109, no, 219, 227, 230; danger of breakage, 181; Curtiss pro- pellers, 216

SCREW-FLIERS (See Helicopters)

SELFRIDGE

his death, 103, 181

SHELLS (See Explosives)

SHIPS (See also Yachts, Boats)

difference between aero- planes and ships in axis of propulsion, 27; comparison of towing-tank experiments and aerodynamic researches, 38

SHOCK-ABSORBERS (See also Alighting)

necessity of, 55

SHRAPNEL (See Explosives)

SIDO, LIEUTENANT

performances as an aerial scout, 191

SKIDS (See also Alighting)

use in alighting, 55; intro- duction by Herring and Wrights, 55; use by Farman, 56, 219; Sommer, 56; Santos- Dumont and Antoinette, 56

SKIN-FRICTION

its laboratory study, 38; in screw propellers, 96

SLIP

definition, 96; speed and slip, 104

SOMMER, ROGER his biplane, 220

SOUNDING-BALLOONS (Set Bal- loons)

SPAN (See Aspect Ratio)

SPEED (See also Motors)

tails and their effect, 17; relation of speed to form, 26; relation to gravitation, 31; effect on angle of incidence, 32; power and speed in aero- planes, 33, 34; monoplane speeds, 35; relation of speed to wind, 35; landing at high

290

INDEX

speed, 36; necessity of vari- able speed, 36, 243; speec and stability, 75; speed and steering, 87; speed and mo- tors, 130; speed and struc- tural design, 177, 179; speec of future aeroplane, 236 SPY, AERIAL

repulsion of, 196 SQUIER, MAJOR G. O.

on military possibilities oJ aerial navigation, 195 STABILITY

in birds, 3; in machines, 4; methods of maintaining stability, 5; fore-and-aft sta- bility, 8, 14, 167; automatic control, 9, 75, 79, 83, 169, 223; monoplane and biplane stability compared, 16; sta- bility explained, 58; aile- rons and their use, 61; Wright warping system, 63, 210; Curtiss system, 65, 92, 215; Wright-Curtiss infringement suit, 67; Farman control, 69, 218, 220; Bleriot control, 70, 226; Antoinette control, 72, 223; the efficiency of the dihedral angle, 74, 170; use of vertical curtains (Voisin), 74; effect of keels, 75; Lanchester on speed and stability, 75; Esnault-Pelterie control, 77; use of tails to maintain fore-and-aft stability, 77, 210; gyrostatic control, 80; au- tomatic vs. hand control, 80; stability and steering, 88; effect of wind, 91; Santos- Dumont control system, 92; dangers of bad manipulation of stabilizers, 167; equilib- rium and stability distin- guished, 168; Sommer system of control, 220 STARTING (See Launching) STAYS (See also Wires)

in monoplanes and bi- planes, 173 et seq.

STEERING (See also Rudders)

necessity for two sets of rudders, 13; Wright system, 64; Curtiss system, 65; Far- man system, 69; Antoinette system, 72; principles in- volved in steering, 85 et seq.'t perils of steering, 170

STRINGFELLOW

his triplane, 20; his pro- peller designs} 99

TAILS

their part in maintaining stability, 9, 14, 17, 77, 79, 212, 219, 221, 226 TAUNUS

Aerological Observatory, 158 TELEGRAPHY, WIRELESS

on aeroplanes in war, 193; Berlin Conference, 251 THEODOLITES

use in meteorology, 143 THERMOMETER

use in meteorology, 134, 139

THRUST (See Screw) TOWING-CARRIAGES

defects of, 39 TRACTOR SCREWS (See Screws) TRAPPES

aerological work, 138 TRESPASS (See Law of the Air) TRIPLANE (See Multiplane) TURKEY-BUZZARD (See also Birds)

efficiency as a flying-ma- chine, 112 TURNING (See Steering)

VAN MAASDYSK

cause of death, 182 VOL-PLANE (See Gliding) VOISIN FRERES (See Biplanes) VULTURES

how launched for flight, 10; how caged and reason there- for, 12

INDEX

291

WACHTER

cause of death, 176, 179

WAR,

flying-machines in, 185 et seq.\ dirigibles vs. aeroplanes in war, 202; double-motor military machine, 232; inter- national law and aerial war- fare, 262

WARPING (See Stability)

WATER-JACKET use in motors, n 6

WEATHER

weather and flight, 133 et seq.

WESTLAKE

on international law of the air, 258

WHEELS FOR ALIGHTING AND LAUNCHING (See Launching and Alighting)

WHIRLING-TABLES their defects, 40

WIND

relation of speed to wind, 35; effect on launching, 46; effect on steering, 91; use of anemometer, 134; wind- data of German Empire, 154; wind perils, 163, 170; wind- gauges for dropping explo- sives, 187

WINGS (See Planes)

WIRES

effect on speed, 33; use in

stiffening monoplanes and biplanes, 173 et seq.

WIRELESS TELEGRAPHY (See Telegraphy)

WRIGHT BROTHERS

their contribution to flight problem, 8; launching de- vices, 12, 51; study of lift of curved surfaces, 28; on variability of angle of inci- dence, 33; study of relation of power to speed (Langley's law), 34; influence of Langley on Wrights, 51; introduc- tion of skids, 55; their solu- tion of stability problem, 61, 63; rudder studies, 77; automatic stability patents, 79; Chanute on their early turning experiments, 89; ac- cident to Orville Wright at Ft. Myer, 103, 181; skill in aviation, 166, 167; scientific character of their work, 183; influence on Farman, 217; Orville Wright on future of aeroplane, 243

YACHTS (See also Boats, Ships) compared with aeroplanes in stability, 3; compared with aeroplane in making a turn, 91

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WILL BE ASSESSED FOR FAILURE TO RETURN THIS BOOK ON THE DATE DUE. THE PENALTY WILL INCREASE TO SO CENTS ON THE FOURTH DAY AND TO $1.OO ON THE SEVENTH DAY OVERDUE.

MAR 5 1934
DEC 26 *Q'ir
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