the long hours they
have frequently to be on duty, with no more than hasty intervals for
rest, their average of care and accuracy is very high. But there have
been cases--mostly in the past though--in which a machine has
developed a structural defect, or some defect say in its control gear,
which ought to have been observed by its mechanics, but which has not
been so detected, and has led to a catastrophe in flight. With
machines built lightly, and subjected to heavy strains when at high
speeds, it is vital that the inspection of such craft, that the
examination of every detail of them, should be carried out in a spirit
of the greatest care. The fraying through of a control wire, unnoticed
by those in charge of a machine, has been sufficient to cause a
disaster; while carelessness in overhauling a motor, a task of supreme
importance, seeing that its engine is the heart of an aeroplane, has
been another cause of accident. It is vital that, when an airman
ascends, both his machine and his motor should be in perfect working
trim. He himself, before he flies, and after his aeroplane has been
wheeled from its shed, should make it a habit to look over the machine,
so as to impose his own personal check upon the work his mechanics
have done.

Even when every care has been taken, and a machine ascends in perfect
trim, there is the human factor, represented by the pilot, which must
be considered always in a study of aeroplane accidents. There is often,
when a catastrophe seems imminent, a choice of things that may be
done. If an engine fails, for instance, under awkward circumstances,
the pilot may have, say, three courses open to him in regard to his
descent. Two may spell disaster and the third safety. It is here that
the innate judgment of a pilot, combined with his experience, will
tell its tale. But this personal element in flying, and particularly
in regard to an accident, is often a very difficult one for which to
make allowances.

The whole problem of aeroplane disasters is, to the analyst, one of
unusual complexity. Take for example the case of a pilot who is flying
alone in his machine, and at an altitude of several thousand feet.
Suddenly something happens; the machine is seen to fall and the pilot
is killed. Experts come to examine the aircraft, but it is wrecked so
completely that little which is reliable can be gathered from any
inspection; while the man who could explain what has happened--the
pilot of the mach