Many people still think that if the engine of an aeroplane should stop
while the machine was in mid-air, a terrible disaster would happen. All
petrol engines may be described as fickle in their behaviour, and
so complicated is their structure that the best of them are given to
stopping without any warning. Aeroplane engines are far superior
in horse-power to those fitted to motorcars, and consequently their
structure is more intricate. But if an airman's engine suddenly stopped
there would be no reason whatever why he should tumble down head first
and break his neck. Strange to say, too, the higher he was flying the
safer he would be.
All machines have what is called a GLIDING ANGLE. When the designer
plans his machine he considers the distribution of the weight or the
engine, pilot and passengers, of the petrol, aeronautical instruments,
and planes, so that the aeroplane is built in such a manner that when
the engine stops, and the nose of the machine is turned downwards, the
aeroplane of its own accord takes up its gliding angle and glides to
earth.
Gliding angles vary in different machines. If the angle is one in
twelve, this would mean that if the glide wave commenced at a height of
1 mile, and continued in a straight line, the pilot would come to
earth 12 miles distant. We are all familiar with the gradients shown on
railways. There we see displayed on short sign-posts such notices as
"1 in 50", with the opposite arms of the post pointing upwards and
downwards. This, of course, means that the slope of the railway at that
particular place is 1 foot in a distance of 50 feet.
One in twelve may be described as the natural gradient which the machine
automatically makes when engine power is cut off. It will be evident why
it is safer for a pilot to fly, say, at four or five thousand feet high
than just over the tree-tops or the chimney-pots of towns. Suppose, for
example, the machine has a gliding angle of one in twelve, and that when
at an altitude of about a mile the engine should stop. We will assume
that at the time of the stoppage the pilot is over a forest where it is
quite impossible to land. Directly the engine stopped he would change
the angle of the elevating plane, so that the aeroplane would naturally
fall into its gliding angle. The craft would at once settle itself into
a forward and slightly downward glide; and the airman, from his point of
vantage, would be able to see the extent of the forest. We will assume
that the aeroplane is gliding in a northerly direction, and that the
country is almost as unfavourable for landing there as over the forest
itself. In fact, we will imagine an extreme case, where the airman is
over country quite unsuitable for landing except toward the south;
that is, exactly opposite to the direction in which he starts to glide.
Fortunately, there is no reason why he should not steer his machine
right round in the air, even though the only power is that derived
from the force of gravity. His descent would be in an immense slope,
extending 10 or 12 miles from the place where the engine stopped
working. He would therefore be able to choose a suitable landing-place
and reach earth quite safely.
But supposing the airman to be flying about a hundred yards above the
forest-an occurrence not likely to happen with a skilled airman, who
would probably take an altitude of nearly a mile. Almost before he could
have time to alter his elevating plane, and certainly long before he
could reach open ground, he would be on the tree-tops.
It is thought that in the near future air-craft will be fitted with two
or more motors, so that when one fails the other will keep the machine
on its course. This has been found necessary in Zeppelin air-ships. In
an early Zeppelin model, which was provided with one engine only, the
insufficient power caused the pilot to descend on unfavourable ground,
and his vessel was wrecked. More recent types of Zeppelins are fitted
with three or four engines. Experiments have already been made with the
dual-engine plant for aeroplanes, notably by Messrs. Short Brothers, of
Rochester, and the tests have given every satisfaction.
There is little doubt that if the large passenger aeroplane is made
possible, and if parliamentary powers have to be obtained for the
formation of companies for passenger traffic by aeroplane, it will be
made compulsory to fit machines with two or more engines, driving three
or four distinct propellers. One of the engines would possibly be of
inferior power, and used only in cases of emergency.
Still another cause of accident, which in some cases has proved fatal,
is the taking of unnecessary risks when in the air. This has happened
more in America and in France than in Great Britain. An airman may have
performed a very difficult and daring feat at some flying exhibition
and the papers belauded his courage. A rival airman, not wishing to
be outdone in skill or courage, immediately tries either to repeat the
performance or to perform an even more difficult evolution. The result
may very well end in disaster, and
FAMOUS AIRMAN KILLED
is seen on most of the newspaper bills.
The daring of some of our professional airmen is notorious. There is
one particular pilot, whose name is frequently before us, whom I have
in mind when writing this chapter. On several occasions I have seen him
flying over densely-packed crowds, at a height of about two hundred feet
or so. With out the slightest warning he would make a very sharp and
almost vertical dive. The spectators, thinking that something very
serious had happened, would scatter in all directions, only to see the
pilot right his machine and jokingly wave his hand to them. One trembles
to think what would have been the result if the machine had crashed to
earth, as it might very easily have done. It is interesting to relate
that the risks taken by this pilot, both with regard to the spectators
and himself, formed the subject of comment, and, for the future, flying
over the spectators' heads has been strictly forbidden.
From 1909 to 1913 about 130 airmen lost their lives in Germany, France,
America, and the British Isles, and of this number the British loss
was between thirty and forty. Strange to say, nearly all the German
fatalities have taken place in air-ships, which were for some years
considered much safer than the heavier-than-air machine.