PERILS OF THE AIR
How pilots fought the wind--Military demands
for an “airworthy” machine--Value of the
air-scout--Dangers in wind-flying--The
“side-slip”--Aeroplanes that are automatically
stable.
It has been shown how aeroplanes were built and made to fly, and not
machines of one particular make, but biplanes and monoplanes of various
types of construction; also how, granted he had a reliable motor, a man
might fly for hours without alighting. These were the lessons of 1909;
these, and the fact that flying was proved an art that could be learned
by any man who was active and had sound nerves. After Wilbur Wright had
taught his first pupils, and Bleriot and Farman had established training
schools, men in rapidly increasing numbers came to learn to fly; so
that, quite early in 1910, it was possible to list the names of more
than 200 pilots.
Progress was now revealed in two directions: firstly, encouraged by
engine reliability, airmen made cross-country flights; and secondly,
becoming more used to being in the air, and gaining confidence in the
handling of their machines, they began to fly in gusty winds. This was
shown by the fact that, fearing any breeze at first that was higher than
10 or 15 miles an hour, pilots soon combated winds of 20 and 25 miles an
hour.
Flights of 100 miles were made across country; one historic example, of
course, was M. Paulhan’s 183-mile journey from London to Manchester,
made in 242 minutes and with but one halt, by which he won _The Daily
Mail_ £10,000 prize, and in which--meeting him in keen but friendly
rivalry as the representative of England--he had the joint author of
this book, Mr. Claude Grahame-White.
The confidence of pilots in the reliability of their machines was
demonstrated conclusively by the Comte de Lambert. Rising from the
aerodrome at Juvisy, near Paris, he flew over the city and circled the
Eiffel Tower, returning afterwards without accident to his
starting-point.
Several more airmen had, by this time, succeeded in crossing the
Channel, and a notable feat was that of the Hon. C. S. Rolls, who flew
from Dover till he reached the French coast near Calais; then, circling
without a descent, he returned to his starting-point--a flight over-sea
that lasted an hour and a half. In high flying, too, the confidence of
airmen was displayed. At Rheims in 1909, it may be remembered, Latham
rose 500 feet, and this was considered remarkable. But the record,
during 1910, was beaten and beaten again, until it stood at nearly
10,000 feet. In speed also, using monoplanes with 50-h.p. motors, pilots
made records day by day; and an English airman, Mr. Radley, flying over
a measured course in August 1910, in a Bleriot monoplane, attained a
speed of more than 70 miles an hour.
In the duration of flight, which proved the reliability of engines,
great strides also were made. From Farman’s 4-hour record at the end of
1909, the figure was carried till it stood at 6 hours 1 minute 35
seconds. This flight was made by Tabuteau, an airman flying a Maurice
Farman biplane. Maurice was a brother of the famous Henri, and he built
a biplane which, while resembling the Henri Farman in general aspect,
was different in detail. In the first machines he built,--and it is one
of these the sketch (Fig. 52) shows,--Maurice Farman used, in addition
to ailerons, two side curtains or panels, as the Voisins had done; but
these he afterwards abandoned, retaining ailerons alone. A feature of
this machine was the way in which the landing skids were continued
upward, so as to form the supports for the elevating-plane. The Maurice
Farman developed into a stable and remarkably successful craft, greatly
used for cross-country flying and by military pilots.
[Illustration: FIG. 52.--Maurice Farman Biplane (early type).
A. Elevating-plane; B. Seats for pilot and passenger; C.C. Main-planes;
D. Motor with two-bladed propeller; E. Vertical panel; F. Aileron; G.
Tail-planes; H.H. Rudders; I. Landing chassis.]
The chief triumph of 1910 was the fight airmen waged against the wind.
This was their enemy--an enemy which sought to chain them to the
ground, and prevent their craft from becoming of practical use. One
point, indeed, became clear: it was of little value to fly high or for
long distances, if one could only do so in favourable weather. The
aeroplane, if it was to play a practical part in the affairs of the
world, must ascend in high winds as well as in calms. This being
recognised, there was strenuous effort to produce an “all-weather”
machine. Particularly was wind-flying of value in the military use of
aeroplanes; and it is here that we reach a vital aspect of aviation.
Immediately craft could fly across country, and ascend high enough for a
view of the land to be obtained from them, it was seen they would have a
great value as scouts in time of war.
There has, from the earliest days of battle, been a need for scouting--a
need for news as to what the enemy is doing. Picture two armies about to
engage. They approach each other cautiously, troops spread out and
dotted here and there; while in front of each force is thrown a screen
of outposts. These form a protective fence, through which the scouts of
the enemy find it difficult to penetrate. What the scouts seek to
discover is how many men there are in the army moving forward, how many
guns, and how these men and guns are being massed and drawn up for the
battle that impends. But the outposts head them off and shoot them down;
and as both armies have outposts, and as both sets of scouts find the
same difficulty in obtaining news, the two forces may grope and blunder
into battle without knowing such facts as to numbers and positions as
might spell the difference between victory and defeat. Of course, the
scouts do their best, some on foot, some horsed; but it was Napoleon who
wrote:
“Nothing is more contradictory, nothing more bewildering, than
the multitude reports of spies or of officers sent out to
reconnoitre. Some locate army corps where they have seen only
detachments; others see only detachments where they ought to have
seen army corps.”
But now came the aeroplane, and strategists seized the opportunities it
offered. Outposts could do nothing against such a scout as this; instead
of seeking to dodge them through a wood, or round a hill, it could pass
thousands of feet above their heads; and the earth below, as viewed by
the spy sitting in his machine, would be spread out like a panorama; he
would see the troops of the enemy in motion, and note their strength and
the positions to which they moved. No wonder the War Departments of
Europe were ready to buy aeroplanes. Buy them they did, indeed, in
growing numbers; but the drawback of the early machines was that they
were fair-weather craft; they would not fly in winds. Imagine that a
battle impends, and that the Commander-in-Chief of one army seeks news
as to the movements of some division of his enemy; so he orders the
air-scouts to ascend. But the wind may be blowing hard; and if it is,
and the aeroplanes are only fair-weather machines, they will have to
remain on the ground till the wind drops, and perhaps miss their
greatest chance during a whole campaign.
But it was astonishing how, feeling greater confidence in the handling
of their machines, airmen began to join issue with this enemy the wind.
They were helped, too, by a growing efficiency in the construction of
their craft. Machines were built more strongly, engines were more
staunchly made; in all details that spelt reliability, were aircraft
improved. But the wind, none the less, took its toll. It was not
combated without loss of life; and we find that, before the end of 1910,
nearly thirty men had been killed while flying. In many cases, struck by
a heavy gust, a machine collapsed in flight; in others, beaten over by
the force of the wind, but with his craft intact, the pilot had fallen
to earth, powerless to regain the control of his machine.
[Illustration: PLATE IX.--THE FIRST HIGH-POWERED BLERIOT.
This type of monoplane, in which Mr. Grahame-White learned to fly--being
seen with a passenger above--was built by Bleriot for the speed contests
at Rheims in 1909. It had an 80-h.p. motor, as compared with the
25-h.p. engine which was then fitted to ordinary Bleriots, and attained
a speed of 60 miles an hour.]
In wind-flying there were these two distinct dangers: a man might be
dashed to earth by a gust when rising or descending; or he might be
struck by a rush of wind when at a considerable height, and find his
craft driven over until it began to slip sideways instead of flying
forward. In “side-slips,” as they are called, there lies a grave risk.
What happens is this. A man flying in a wind may, by vigorous use of his
ailerons, recover the balance of his machine time after time; but as the
wind rises, he may be struck ultimately by a gust that tilts his planes
to an abnormal angle, despite his efforts to check them. The machine
will then heel till it stands almost vertical--till it reaches such an
angle, in fact, that it ceases to move forward and begins to slip
sideways--skidding away, beyond the pilot’s control, like a motor on a
greasy road. How an abnormal gust may cause a side-slip is illustrated
by Fig. 53.
[Illustration: IN NORMAL FLIGHT.
FIG. 53.--Machine “side-slipping” in a gust.
STRUCK BY AN ABNORMAL GUST.
MACHINE SLIPPING SIDEWAYS.]
In such a predicament, two things only can save the airman; one his
height above the ground, the other his nerve and presence of mind. If he
is flying low when his machine side-slips, nothing can avert disaster.
Falling at first sideways in a helpless lurch, then diving violently,
the craft will strike ground with shattering force--completely beyond
its pilot’s control. But if the airman is flying high, and granted he
is a man of experience, he may escape even the worst of side-slips, and
how he does so is as follows: as his machine slips he puts forward his
elevating-lever as far as it will go, throws over his rudder to help the
action of the elevator, and sets his motor at its fullest power--these
actions seeming, in themselves, merely to aggravate the peril by causing
the craft to fall more quickly. But the pilot knows what he is doing; he
knows that, so long as his craft slips sideways, it is impossible for
his controlling planes to act, seeing that they are effective only when
the machine moves forward through the air. What he seeks to do,
therefore, is to convert the side-slip into a forward dive. If he can do
this--if he has space for the manœuvre before the machine strikes
ground--he knows he can avert disaster.
In throwing over his elevating-lever, and accelerating his motor, his
aim would be to make his machine fall forward more rapidly than it is
slipping sideways; and, as a rule, under the combined thrust of the
motor, and the extreme angles of elevating-plane and rudder, the craft
will--after a sickening slip, perhaps of several hundred feet--begin to
lose its sideway motion and plunge straight downward. His elevating
plane will then become operative, tending to check this dive and bring
up the bow of the machine; and at the same time, feeling he has regained
control, the pilot will throttle down his motor so as to reduce the
speed of his machine. In this way, responding to the action of its
elevator, the craft will pause in its downward rush, and sweep forward
again upon an even keel. But the actions of the pilot, in such a
quandary, need to be accurately and boldly made; and unless his craft
flies high, no skill can save it. If he has not a thousand feet or more
below him, he will be dashed to death before his manœuvre has time to
take effect.
The moral, therefore, lay in flying high, and it was one that pilots
respected. Instead of passing across country at a few hundred feet, they
began soon to ascend 3000 feet and more; and at such altitudes, apart
from the greater safety in case of side-slip, an airman found usually a
steadier and less gusty wind, and was in a better position to choose
some landing-point should his motor fail suddenly.
When starting across country, particularly in the early days, a pilot
had to consider very seriously the question of the failing of his motor.
So long as he had an aerodrome below him, its smooth surface providing
an alighting spot, he felt no great concern. But in flying across
country, should his motor stop, he might find himself above a forest, or
a sheet of water, or such rough and broken land that his machine would
be damaged were he to alight upon it. But here again, as in the case of
side-slip, altitude would tend to safety.
In the stoppage of its motor, when a craft is in flight, several factors
need consideration; but one should clearly be understood: even if his
engine does fail while he is passing through the air, a pilot is not
helpless, nor does his machine fall to the ground. As he flies, of
course, it is the thrust of his motor, acting through the medium of the
propeller, that keeps his craft moving forward; and so long as this
thrust is there, forcing his planes against the air and causing them to
lift their load, the machine will fly ahead. But what happens should the
engine fail, and the machine cease to be propelled? The first effect is
that the craft begins to lose its speed, and as it does this its planes
are less operative. Unless he can restore his forward speed, therefore,
and so maintain the lift of his planes, the pilot is in peril. Were he
merely to sit still after his engine failed, and do nothing to save
himself, he would be in a position of the greatest risk. What would
happen would be that his craft, having no power thrusting it against
the air, would come gradually to a standstill; then, its planes
exercising no further lift, it would lose equilibrium and fall.
But there is another force the airman can use, even when his motor fails
entirely; and this is the downward pull of gravity, which acts
unceasingly upon his machine. He must, at all costs, restore the speed
of his craft; not only that its main-wings may bear their weight, but
that its controlling-planes may continue operative, and enable him to
steer towards a landing-point. What he does, therefore, when he hears
his motor stop, is to tilt his elevating lever and send his machine upon
a dive. Thus, even with no motor to propel him, he can still fly. It is
gravity now that moves his machine, and so long as he keeps his lever
forward, and sends his craft downward upon a gradually sloping path, he
has perfect control and need not fear a fall. Air is still being forced
under his planes; therefore, they bear their load; and, seeing that the
machine is moving forward, its rudder and other controlling planes are
able to do their work. The airman is, in fact, as much in command of his
machine as he was before its motor stopped--save for one vital
difference. While his motor ran he could fly where he pleased; but now
he is obliged to glide downward. He is, indeed, in the same position as
was Lilienthal, or any of the men who soared from hilltops. But, being
say 1000 feet or more high when his engine stops, he has the advantage
of a long glide before he reaches ground; and this gives him a chance,
surveying the land below him, to pick a smooth landing-point that may
lie in his path. If well-designed, an aeroplane will glide a long way
after its motor has failed, as is indicated by Fig. 54. In this case,
representing an actual test with a military machine, the motor has
stopped at an altitude of between 1200 and 1400 feet, and the craft
glides, before touching ground, a distance of nearly 9000 feet.
[Illustration: FIG. 54.--The gliding angle of a plane.
The motor is switched off at a height of between 1200 and 1400 feet, and
the craft glides nearly 9000 feet before landing.]
This gliding without motive power is a safeguard to the airman when he
flies across country. Should he attain a sufficient altitude, he has
little to fear, even if his engine does fail. As he glides down, he can
steer from side to side, or make a half circle and land upon a spot that
lies behind him. An aeroplane with a gliding path of 1 foot in 10, and
at a height of a mile when its engine stopped, would glide ten miles
before alighting. Taking an extreme case, one might imagine an airman
flying over a city. Suddenly, while above a network of streets and
houses, his engine stops. But even in such a quandary as this, granted
he has the wisdom to be several thousand feet high, he need not fear
disaster. Glancing keenly below him, he sights some park or open space
like an oasis among the close-packed buildings, and glides swiftly and
accurately towards it, landing without difficulty or injury to his
machine.
The making of a gliding descent, or _vol-plané_, is an art all airmen
learn; and the vital thing to remember in connection with it is, that
the machine must always move swiftly forward. Sometimes, checking his
glide too soon, a pupil at the schools will make what is called a
“pancake” landing: that is to say, misjudging his height above the
ground, he stops the glide of his craft, by a movement of the elevating
plane, when he is still 15 or 20 feet in the air. The result is that
the machine comes to a standstill, then drops flat upon its wheels; and
in doing so it may break its chassis supports, and give the pupil a
shaking. The art, in a gliding descent, is to lessen the steepness of
the dive, by throwing up the elevating plane only a second or so before
the landing-wheels make their contact with the ground. Then, its
downward speed checked--in the same way that a bird checks itself, just
before its feet touch earth--the wheels of the craft will meet the
surface smoothly, and there will be no shock or rebound.
[Illustration: A. Upper main plane; B.B. Lower main plane; C.C. Hinged
flaps which act as air brakes.
SEEN FROM ABOVE.
AS VIEWED FROM ONE SIDE.
FIG. 55.--An air brake.]
In most cases, a machine with a good gliding angle is regarded with
favour; but there are circumstances--such, for instance, as when a pilot
seeks to alight in a small field--when a gradual descending angle is a
disadvantage. The field may be bounded by trees; hence, if the machine
prolongs its glide, and he cannot make a quick landing, the pilot may
find himself threatened by a collision. To check the forward glide of a
craft, when necessary, and bring it to earth at a steep angle, air
brakes are now being tested, as illustrated in Fig. 55. When not in use,
they form sections of the lower main-plane, and are operated by the
pilot with a lever. Their action is simple: pivoted in the centre, they
swing until they expose themselves at right angles; and their surface,
when thus exposed, tends very materially to check the glide. The descent
of a machine into a small field, with and without brakes, is shown in
Fig. 56; and from this the value of the brake may be seen.
[Illustration: FIG. 56.--Action of an air brake.
A.A. Trees enclosing a small field; B. Gliding angle of a machine with
an air brake; C. Angle of a machine without a brake.]
The chief peril of the air, when pilots came to understand their risks,
was seen to be this: that a machine might be caught by a wind-gust when
flying near the ground, and dashed to earth before its pilot could check
the helpless dive; and this peril still presents itself. Combating a
breeze at first, then gusty winds, the airman has so progressed to-day
that he will face a 60-mile-an-hour gale. When well aloft, indeed, he
hardly cares how the wind may blow. It may turn him completely over, but
he is not lost; as shown by “looping the loop,” in fact, a pilot can
perform a somersault in the air and not lose control of his machine.
“Looping the loop,” which has made so great a sensation, has taught
airmen one definite lesson; and it is this: no matter how their machines
may be beaten and tossed by the wind, they need not fear a
fall--provided they are high enough above ground. The movements of a
machine, as it makes a series of “loops,” are shown in Fig. 57. The
pilot reaches a high speed before he rears up his machine to begin the
“loop,” and this downward velocity is attained by diving; then, when he
estimates his pace sufficient, he pulls his elevating-lever back and the
machine leaps upward, rearing itself vertically towards the sky, turning
over on its back, then diving again and coming right-side-up--thus
achieving a complete somersault. A skilled trick-flyer, also, will allow
his machine to drop sideways or tail first, deliberately working the
controls so that it shall do so. Then, just as it seems to spectators
that he is falling to destruction, he will dive or twist, regain the
mastery of his machine, and descend in a normal glide.
An airman, flying in a wind, is rather in the position of a man who puts
to sea in a small boat when waves are high. Once he can clear the shore,
the boatman feels at ease; but should a breaker catch him before he
reaches the smooth, rolling billows a little distance from the beach,
his craft may be overturned and dashed to pieces. So with the airman;
his moments of peril, when flying in a gusty wind, come just as he is
soaring from the ground, and when descending from a flight. Then an
air-wave, like a sea-wave, may lift his craft and drive it with a crash
to earth.
[Illustration: FIG. 57.--Looping the loop.]
And there is the peril, when near the ground, of a down-rush of wind
caused by hills or woods. More than once, when making a landing near
trees, a pilot has found his machine swept in a descending current. What
happens, in such a case, is that the wind curls over the wood or hill
that may form the obstruction, and sends a strong eddy downward; should
a machine be caught in such a trend, it may be carried to earth,
pell-mell, before the pilot can check its dive. Again--as another unseen
danger--there are “holes in the air.” The atmosphere is in constant
movement, it must be remembered; currents of warm air ascending and
currents of cold air descending; and sometimes, between a layer of warm
air and a layer of cold, there may be violent swirls and eddies. An
aeroplane may fly into such a disturbed area and fall suddenly a
distance of many feet, through being caught and swept earthward in a
rapidly descending current.
But such dangers, like others which threaten, are being surely but
steadily lessened. Machines are now built and flown which, owing to the
shape and angle of their planes, have a stability which is almost
automatic. This means that, when flying in a wind, the pilot need not be
working incessantly at his levers. His machine, once a suitable height
has been reached, will fly with no more control than a touch upon the
rudder-bar. Apart from questions of safety, such stability enables long
flights to be made without fatigue. Should he be flying a machine which
needs constant work at the controls, and should the wind be high, a
pilot becomes often so exhausted that he is compelled to descend. An
automatic stable biplane, called the D.F.W., is illustrated in Fig. 58.
Its main-planes are swept back in the shape of an arrow-head; the rear
extremities of the top-plane, forming large ailerons that are locked in
position or movable at the pilot’s will, are uptilted at their ends;
while the lower main-plane is given a dihedral or sloped-up stabilising
angle. The uptilted ailerons, which bring a negative or top pressure to
bear upon each wing-tip, and the dihedral angle of the lower plane,
which acts in conjunction with them, produce an effect which checks
automatically any tendency to a sideway roll.
[Illustration: FIG. 58.--D.F.W. (German-designed) Biplane.
A. Hull, which is steel-built, containing pilot and passenger; B.B.
Main-planes--the lower at a dihedral angle; C.C. Uptilted stabilising
ailerons, which may be locked in position; D. Stabilising fin; E.
Rudder; F. Elevating-plane; G. 100-h.p. motor (which is enclosed) and
propeller.]
The arrow formation of the planes preserves the stability of the machine
in a fore-and-aft direction. Should its pilot force it up at too steep
an angle, it will merely come to a halt in the air and then dive forward
and resume its normal flight; while, if it is made to plunge too steeply
downward, its bow will rise automatically and the machine resume an even
keel.
Another machine which is stable in flight, owing to the peculiar
formation of its wings, which resist a diving or plunging movement, or a
lateral swing, is the Dunne biplane--as designed by Lieutenant J. W.
Dunne. This craft is seen in Fig. 59. Using such a machine, pilots have
flown for long distances with the control levers locked, the biplane
adapting itself automatically to the wind-gusts and preserving its
equilibrium without aid of any kind. It has neither fore-plane nor tail;
it is made to ascend by elevators which are in the form of hinged flaps,
or ailerons, and is steered by two rudders at the extremities of the
main-planes.
[Illustration: FIG. 59.--Dunne inherently stable Biplane.
A. Hull containing pilot and passenger; B.B. Main-planes; C.C.C.C. Flaps
used as elevators; D.D. Side-planes which act as rudders; E. Engine and
propeller; F. Alighting gear.]
In the future, it is now clear, the automatically stable aeroplane will
play a highly important part. Large machines, with duplicate engines,
will be so constructed that, beyond causing them to rise and descend,
and move to right or left, the steersman will have nothing to do; to all
wind-gusts and inequalities in the air the machine will adapt itself
automatically. In this way it will be possible to build very large
craft, carrying a number of passengers or a consignment of goods, and
to fly in any winds save such raging gales as drive ships for shelter
into port.