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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
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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
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THE MASTERY OF THE AIR
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。
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CHAPTER XLVIII Some Technical Terms used by
Aviators
Though this book cannot pretend to go deeply into the technical side
of aviation； there are certain terms and expressions in everyday use by
aviators that it is well to know and understand。
First； as to the machines themselves。 You are now able to distinguish a
monoplane from a biplane； and you have been told the difference between
a TRACTOR biplane and a PROPELLER biplane。 In the former type the
screw is in front of the pilot； in the latter it is to the rear of the pilot's seat。
Reference has been previously made to the FUSELAGE； SKIDS；
AILERONS； WARPING CONTROLS； ELEVATING PLANES； and
RUDDER of the various forms of air…craft。 We have also spoken of the
GLIDING ANGLE of a machine。 Frequently a pilot makes his machine
dive at a much steeper gradient than is given by its natural gliding angle。
When the fall is about one in six the glide is known as a VOL PLANE； if
the descent is made almost vertically it is called a VOL PIQUE。
In some cases a PANCAKE descent is made。 This is caused by such a
decrease of speed that the aeroplane； though still moving forward； begins
to drop downwards。 When the pilot finds that this is taking place； he
points the nose of his machine at a much steeper angle； and so reaches his
normal flying speed； and is able to effect a safe landing。 If he were too
near the earth he would not be able to make this sharp dive； and the
probability is that the aeroplane would come down flat； with the
possibility of a damaged chassis。 It is considered faulty piloting to make a
pancake descent where there is ample landing space； in certain restricted
areas； however； it is quite necessary to land in this way。
A far more dangerous occurrence is the SIDE…SLIP。 Watch a pilot vol…
planing to earth from a great height with his engine shut off。 The propeller
rotates in an irregular manner； sometimes stopping al