lying as a sport.

CHAPTER VIII

FACTORS THAT MAKE FOR SAFETY

It has been calculated that nearly half the aeroplane disasters of the
early days were due to a structural weakness in machines, or to
mistakes either in their design, or in such details as the position,
shape, and size of their surfaces. To-day, thanks to science, and to
the growing skill and experience of aeroplane designers and
constructors, this risk of the collapse of a machine in the air, or of
its failure to respond to its controls at some critical moment through
an error in design, has been to a large extent eliminated. That such
risks should be eliminated wholly is, as yet, too much to expect.

One of the factors making for safety has been the steady growth in the
general efficiency of aircraft: in the curve of their wings which, as
a result largely of scientific research, has been made to yield a
greater lift for a given surface and to offer a minimum of resistance
to their passage through the air; in the power and reliability of
their engines; in the efficiency of their propellers; and in the
shaping of the fusilage of a machine, and in the placing and
"stream-lining" of such parts as meet the air, so as to reduce the
head resistance which is encountered at high speeds. Such gains in
efficiency, which give constructors more latitude in the placing of
weight and strength where experience show they are needed, have gone
far to produce an airworthy machine. In the old days, when machines
were inefficient, a few revolutions more or less per minute in the
running of an engine meant all the difference between an ascent and
merely passing along the ground. But nowadays, through the all-round
increase in efficiency that has been obtained, a machine will still
fly upon its course without losing altitude, and respond to its
controls, even should the number of revolutions per minute of its
engine be reduced considerably.

When given a greater efficiency in lifting surfaces and
power-plants--and profiting also from the lessons that had been learnt
in the piloting of machines--constructors were able to devote their
attention, and to do so with certainty instead of in a haphazard way,
to the provision of factors of safety when a craft was in flight. With
a machine of any given type, if driven through the air at a certain
speed, it is possible to estimate with accuracy what the normal
strains will be to which it is subjected. But even if such data