Classic History Books

William J. Claxton - The Mastery of the Air

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


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


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


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