STEPS IN TECHNICAL PLANNING
several spheres of aviation, on the far-faring liners of Imperial
Airways, as well as on the fighting aircraft of die Royal Air
Force, placed the Bristol Company in die lead of the world's
design.
There were reasons, of a highly technical nature, why water-
cooled engines as a class were generally unsuitable for this
exacting task. A leading factor against them was dieir greater
weight in proportion to horse power, whilst the primary
recommendation of die Pegasus rested in the fact that each
horse power was produced with an engine weight of the low
figure of 1.6 Ib.
There were other difficulties in connection with water-
cooling of a practical order which threatened to cause trouble
in the extremes of temperature that we should meet. The
Pegasus engine excelled on account of its low weight per
horse power, a point of the greatest importance where every
ounce had to be carried for six miles up through the air and
where each ounce had a much greater detrimental effect at
diat altitude than near sea-level. It excelled also by virtue of
die merits of its supercharger. This is a speciality of die Bristol
Company, and enabled die engine to maintain much of its
power where other engines would fade away.
In the spring of 1932, then, it was reasonably certain that
only one engine in the world was capable of doing the work
we contemplated, a British engine and a Pegasus. To express
it in odier words, it was the knowledge of the development
which the Pegasus engine had reached that brought a scientific
flight over Mount Everest into die region of practical politics.
The matter therefore came to this: the Pegasus engine was
to take the expedition over the summit, and die aeroplane and
all other items of gear would be subsidiary to it.
The enterprise was fortunate in that die Bristol Company
themselves proposed at that time to make an attempt on the
height record, and to surpass that set up by the pilot of the
U.S. Army Air Corps. Naturally, the Pegasus engine was the
one which they intended to employ for this. .This fact turned to
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