the mastery of the air(操纵空气)-第29章
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between pilots in this respect is interesting to observe。 On the great day at
Hendon； in 1913the Aerial Derby daythere were over a dozen pilots out
with their craft。
From the enclosure one could watch the airmen and their mechanics as
the machines were run out from the hangars on to the flying ground。 One
pilot walked beside his mechanics while they were running the machine to
the starting place； and watched his craft with almost fatherly interest。
Before climbing into his seat he would carefully inspect the spars； bolts；
wires； controls； and so on； then he would adjust his helmet and fasten
himself into his seat with a safety belt。
〃Surely with all that preliminary work he is ready to start；〃 remarked
one of the spectators standing by。 But no！ the engine must be run at
varying speeds； while the mechanics hold back the machine。 This
operation alone took three or four minutes； and all that the pilot proposed
to do was to circle the aerodrome two or three times。 An onlooker asked a
mechanic if there were anything wrong with that particular machine。
〃No！〃 was the reply； 〃but our governor's very faddy； you know！〃
And now for the other extreme！ Three mechanics emerged from a
hangar pushing a rather ungainly…looking biplane； which bumped over the
uneven ground。 The pilot was some distance behind； with cigarette in
mouth； joking with two or three friends。 When the machine was run out
into the open ground he skipped quickly up to it； climbed into the seat；
started the engine； waved a smiling 〃good…bye〃； and was off。 For all he
knew； that rather rough jolting of the craft while it was being removed
from the hangar might have broken some wire on which the safety of his
machine； and his life； depended。 The excuse cannot be made that his
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mechanics had performed this all…important work of inspection； for their
attention was centred on the daring 〃banking 〃 evolutions of some
audacious pilot in the aerodrome。
Mr。 C。 G。 Grey； the well…known writer on aviation matters； and the
editor of The Aeroplane； says； with regard to the need of inspection of air…
craft：
〃A pilot is simply asking for trouble if he does not go all over his
machine himself at least once a day； and； if possible； every time he is
starting for a flight。
〃One seldom hears； in these days； of a broken wheel or axle on a
railway coach； yet at the chief stopping places on our railways a man goes
round each train as it comes in； tapping the tires with a hammer to detect
cracks； feeling the hubs to see if there is any sign of a hot box； and looking
into the grease containers to see if there is a proper supply of lubricant。
There ought to be a similar inspection of every aeroplane every time it
touches the ground。 The jar of even the best of landings may fracture a
bolt holding a wire； so that when the machine goes up again the wire may
fly back and break the propeller； or get tangled in the control wires； or a
strut or socket may crack in landing； and many other things may happen
which careful inspection would disclose before any harm could occur。
Mechanics who inspected machines regularly would be able to go all over
them in a few minutes； and no time would be wasted。 As it is； at any
aerodrome one sees a machine come down； the pilot and passenger （a fare
or a pupil） climb out； the mechanics hang round and smoke cigarettes；
unless they have to perform the arduous duties of filling up with petrol。 In
due course another passenger and a pilot climb in； a mechanic swings the
propeller； and away they go quite happily。 If anything casts loose they
come downand it is truly wonderful how many things can come loose or
break in the air without anyone being killed。 If some thing breaks in
landing； and does not actually fall out of place； it is simply a matter of
luck whether anyone happens to see it or not。〃
This advice； coming from a man with such wide experience of the
theory and practice of flying； should surely be heeded by all those who
engage in deadly combat with the demons of the air。 In the early days of
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aviation； pilots were unacquainted with the nature and method of approach
of treacherous wind gusts； often when they were flying along in a steady；
regular wind； one of these gusts would strike their craft on one side； and
either overturn it or cause it to over…bank； so that it crashed to earth with a
swift side…slip through the air。
Happily the experience of those days； though purchased at the cost of
many lives； has taught makers of air…craft to design their machines on
more trustworthy lines。 Pilots； too； have made a scientific study of air
eddies； gusts； and so on； and the danger of flying in a strong or gusty wind
is comparatively small。
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CHAPTER XLVII Accidents and their Cause
（Cont。）
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
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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 p
