EXPERIMENTAL WORK IN FLYING
THE novice about to take his first trial trip in
an automobile will soon learn that the great task
in his mind is to properly start the machine. He
is conscious of one thing, that it will be an easy
matter to stop it by cutting off the fuel supply
and applying the brakes.
CERTAIN CONDITIONS IN FLYING.--In an aeroplane
conditions are reversed. Shutting off the
fuel supply and applying the brakes only bring
on the main difficulty. He must learn to stop the
machine after all this is done, and this is the
great test of flying. It is not the launching,--
the ability to get into the air, but the landing, that
gives the pupil his first shock.
Man is so accustomed to the little swirls of air
all about him, that he does not appreciate what
they mean to a machine which is once free to
glide along in the little currents which are so unnoticeable
to him as a pedestrian.
The contour of the earth, the fences, trees, little
elevations and other natural surroundings, all
have their effect on a slight moving air current,
and these inequalities affect the air and disturb
it to a still greater extent as the wind increases.
Even in a still air, with the sun shining, there are
air eddies, caused by the uneven heating of the
air in space.
HEAT IN AIR.--Heat is transmitted through the
air by what is called convection, that is, the particles
of the air transmit it from one point to the
next. If a room is closed up tight, and a little
aperture provided so as to let in a streak of sunlight,
it will give some idea of the unrest of the
atmosphere. This may be exhibited by smoke
along the line of the sun's rays, which indicates
that the particles of air are constantly in motion,
although there may be absolutely nothing in the
room to disturb it.
MOTION WHEN IN FLIGHT.--If you can imagine
a small airship floating in that space, you can
readily conceive that it will be hurled hither and
thither by the motion which is thus apparent to
the eye.
This motion is greatly accentuated by the surface
of the earth, independently of its uneven contour.
If a ball is thrown through the air, its
dynamic force is measured by its impact. So
with light, and heat. In the space between the
planets it is very cold. The sunlight, or the rays
from the sun are there, just the same as on the
earth.
Unless the rays come into contact with something,
they produce no effect. When the beams
from the sun come into contact with the atmosphere
a dynamic force is exerted, just the same
as when the ball struck an object. When the rays
reach the earth, reflection takes place, and these
reflected beams act on the air under different conditions.
CHANGING ATMOSPHERE.--If the air is full of
moisture, as it may be at some places, while
comparatively dry at other points, the reflection
throughout the moist area is much greater than in
the dry places, hence evaporation will take place
and whenever a liquid vaporizes it means heat.
On the other hand, when the vapor is turning
to a liquid, condensation takes place, and that
means cooling. If the air should be of the same
degree of saturation throughout,--that is, have
the same amount of moisture everywhere, there
would be few winds. These remarks apply to
conditions which exist over low altitudes all over
the earth.
But at high altitudes the conditions are entirely
different. As we ascend the air becomes rarer.
It has less moisture, because a wet atmosphere,
being heavier, lies nearer the surface of the earth.
Being rarer the action of sunlight on the particles
is less intense. Reflection and refraction of the
rays acting on the light atmosphere do not produce
such a powerful effect as on the air near the
ground.
All these conditions--the contour of the earth;
the uneven character of the moisture in the air;
the inequalities of the convection currents; and
the unstable, tenuous, elastic nature of the atmosphere,
make the trials of the aviator a hazardous
one, and it has brought out numerous theories
connected with bird flight. One of these assumes
that the bird, by means of its finely organized
sense, is able to detect rising air currents, and it
selects them in its flight, and by that means is enabled
to continue in flight indefinitely, by soaring,
or by flapping its wings.
ASCENDING CURRENTS.--It has not been explained
how it happens that these particular "ascending
currents" always appear directly in the line of
the bird flight; or why it is that when, for instance,
a flock of wild geese which always fly through
space in an A-shaped formation, are able to get
ascending air currents over the wide scope of space
they cover.
ASPIRATE CURRENTS.--Some years ago, in making
experiments with the outstretched wings of
one of the large soaring birds, a French sailor
was surprised to experience a peculiar pulling motion,
when the bird's wings were held at a certain
angle, so that the air actually seemed to draw it
into the teeth of the current.
It is known that if a ball is suspended by a
string, and a jet of air is directed against it, in
a particular way, the ball will move toward the
jet, instead of being driven away from it. A well
known spraying device, called the "ball nozzle,"
is simply a ball on the end of a nozzle, and the
stream of water issuing is not effectual to drive
the ball away.
From the bird incident alluded to, a new theory
was propounded, namely, that birds flew because
of the aspirated action of the air, and the wings
and body were so made as to cause the moving air
current to act on it, and draw it forwardly.
OUTSTRETCHED WINGS.--This only added to the
"bird wing" theory a new argument that all flying
things must have outstretched wings, in order
to fly, forgetting that the ball, which has no
outstretched wings, has also the same "aspirate"
movement attributed to the wings of the bird.
The foregoing remarks are made in order to impress
on the novice that theories do not make
flying machines, and that speculations, or analogies
of what we see all about us, will not make an
aviator. A flying machine is a question of
dynamics, just as surely as the action of the sun on
the air, and the movements of the currents, and
the knowledge of applying those forces in the flying
machine makes the aviator.
THE STARTING POINT.--Before the uninitiated
should attempt to even mount a machine he should
know what it is composed of, and how it is made.
His investigation should take in every part of the
mechanism; he should understand about the plane
surface, what the stresses are upon its surface,
what is the duty of each strut, or brace or wire
and be able to make the proper repairs.
THE VITAL PART OF THE MACHINE.--The motor,
the life of the machine itself, should be like a
book to him. It is not required that he should
know all the theories which is necessary in the
building, as to the many features which go to
make up a scientifically-designed motor; but he
must know how and why it works. He should understand
the cam action, whereby the valves are
lifted at the proper time; what the effect of the
spark advance means; the throttling of the engine;
air admission and supply; the regulation
of the carbureter; its mechanism and construction;
the propeller should be studied, and its action
at various speeds.
STUDYING THE ACTION OF THE MACHINE.--Then
comes the study on the seat of the machine itself.
It will be a novel sensation. Before him is the
steering wheel, if it should be so equipped. Turning
it to the right, swings the vertical tail plane
so the machine will turn to the right. Certainly,
he knows that; but how far must he turn the
wheel to give it a certain angle.
It is not enough to know that a lever or a wheel
when moved a certain way will move a plane a
definite direction. He should learn to know
instinctively, how FAR a movement to make to get
a certain result in the plane itself, and under running
conditions, as well.
Suppose we have an automobile, running at the
rate of ten miles an hour, and the chauffeur turns
the steering wheel ten degrees. He can do so with
perfect safety; but let the machine be going forty
miles an hour, and turn the wheel ten degrees,
and it may mean an accident. In one case the
machine is moving 14 1/2 feet a second, and in the
other instance 58 feet.
If the airship has a lever for controlling the
angle of flight, he must study its arrangement,
and note how far it must be moved to assume
the proper elevating angle. Then come the means
for controlling the lateral stability of the machine.
All these features should be considered and studied
over and over, until you have made them your
friends.
While thus engaged, you are perfectly sure that
you can remember and act on a set of complicated
movements. You imagine that you are skimming
over the ground, and your sense tells you that you
have sufficient speed to effect a launching. In
your mind the critical time has come.
ELEVATING THE MACHINE.--Simply give the elevator
lever the proper angle, sharp and quick and
up you go. As the machine responds, and you can
feel the cushioning motion, which follows, as it begins
to ride the air, you are aware of a sensation
as though the machine were about to turn over
to one side; you think of the lateral control at
once, but in doing so forget that the elevator must
be changed, or you will go too high.
You forget about the earth; you are too busy
thinking about several things which seem to need
your attention. Yes, there are a variety of matters
which will crowd upon you, each of which require
two things; the first being to get the proper
lever, and the second, to move it just so far.
In the early days of aeroplaning, when accidents
came thick and fast, the most usual explanation
which came from the pilot, when he recovered,
was: "I pushed the lever too far."
Hundreds of trial machines were built, when
man learned that he could fly, and in every instance,
it is safe to say, the experimenter made the
most strenuous exertion to get up in the air the
first time the machine was put on the trial ground.
It is a wonder that accidents were not recorded
by the hundreds, instead of by the comparatively
few that were heard from. It was very discouraging,
no doubt, that the machines would not fly,
but that all of them, if they had sufficient power,
would fly, there can be no doubt.
HOW TO PRACTICE.--Absolute familiarity with
every part of the machine and conditions is the
first thing. The machine is brought out, and the
engine tested, the machine being held in leash
while this is done. It is then throttled down so
that the power of the engine will be less than is
necessary to raise the machine from the ground.
THE FIRST STAGE.--Usually it will require over
25 miles an hour to raise the machine. The engine
is set in motion, and now, for the first time a new
sensation takes possession of you, for the reason
that you are cut off from communication with
those around you as absolutely as though they
were a hundred miles away.
This new dependence on yourself is, in itself,
one of the best teachers you could have, because
it begins to instill confidence and control. As the
machine darts forward, going ten or fifteen miles
an hour, with the din of the engine behind you,
and feeling the rumbling motion of the wheels
over the uneven surface of the earth, you have the
sensation of going forty miles an hour.
The newness of the first sensation, which is
always under those conditions very much augmented
in the mind, wears away as the machine
goes back and forth. There is only one control
that requires your care, namely, to keep it on a
straight course. This is easy work, but you are
learning to make your control a reflex action,--to
do it without exercising a distinct will power.
PATIENCE THE MOST DIFFICULT THING.--If you
have the patience, as you should, to continue this
running practice, until you absolutely eliminate
the right and left control, as a matter of thought,
occasionally, if the air is still turning the machine,
and eventually, bringing it back, by turning
it completely around, while skimming the ground,
you will be ready for the second stage in the
trials.
THE SECOND STAGE.--The engine is now arranged
so that it will barely lift, when running
at its best. After the engine is at full speed, and
you are sure the machine is going fast enough,
the elevator control is turned to point the machine
in the air. It is a tense moment. You are on the
alert.
The elevator is turned, and the forward end
changes its relation with the ground before you.
There was a slight lift, but your caution induces
you to return the planes to their normal running
angle. You try it again. You are now certain
that the machine made a leap and left the ground.
This is the exhilarating moment.
With a calm air the machine is turned while
running, by means of the vertical rudders. This
is an easy matter, because while going at twenty
miles an hour, the weight of the machine on the
surface of the ground is less than one-tenth of its
weight when at rest.
Thus the trial spins, half the time in the air,
in little glides of fifty to a hundred feet, increasing
in length, give practice, practice, PRACTICE,
each turn of the field making the sport less exciting
and fixing the controls more perfectly in the
mind.
THE THIRD STAGE.--Thus far you have been
turning on the ground. You want to turn in the
air. Only the tail control was required while on
the ground. Now two things are required after
you leave the ground in trying to make a turn:
namely, putting the tail at the proper angle, and
taking charge of the stabilizers, because in making
the turn in the air, the first thing which will
arrest the attention will be the tendency of the
machine to turn over in the direction that you are
turning.
After going back and forth in straight-away
glides, until you have perfect confidence and full
control, comes the period when the turns should
be practiced on. These should be long, and tried
only on that portion of the field where you have
plenty of room.
OBSERVATIONS WHILE IN FLIGHT.--If there are
any bad spots, or trees, or dangerous places, they
should be spotted out, and mentally noted before
attempting to make any flight. When in the air
during these trials you will have enough to occupy
your mind without looking out for the hazardous
regions at the same time.
Make the first turns in a still air. If you should
attempt to make the first attempts with a wind
blowing you will find a compound motion that will
very likely give you a surprise. In making the
first turn you will get the sensation of trying to
fly against a wind. Assuming that you are turning
to the left, it will have the sensation of a wind
coming to you from the right.
FLYING IN A WIND.--Suppose you are flying directly
in the face of a wind, the moment you begin
to turn the action, or bite of the wind, will cause
the ends of the planes to the right to be unduly
elevated, much more so than if the air should be
calm. This raising action will be liable to startle
you, because up to this time you have been accustomed
to flying along in a straight line.
While flying around at the part of the circle
where the wind strikes you directly on the right
side the machine has a tendency to climb, and you
try to depress the forward end, but as soon as you
reach that part of the circle where the winds begin
to strike on your back, an entirely new thing
occurs.
As the machine is now traveling with the wind,
its grip on the air is less, and since the planes were
set to lower the machine, at the first part of the
turn, the descent will be pretty rapid unless the
angle is corrected.
FIRST TRIALS IN QUIET ATMOSPHERE.--All this
would be avoided if the first trials were made in
a quiet atmosphere. Furthermore, you will be
told that in making a turn the machine should be
pointed downwardly, as though about to make a
glide. This can be done with safety, in a still
air, although you may be flying low, but it would
be exceedingly dangerous with a wind blowing.
MAKING TURNS.--When making a turn, under no
circumstances try to make a landing. This
should never be done except when flying straight,
and then safety demands that the landing should
be made against the wind and not with it. There
are two reasons for this: First, when flying with
the wind the speed must be greater than when flying
against it.
By greater speed is meant relative to the earth.
If the machine has a speed of thirty miles an hour,
in still air, the speed would be forty miles an hour
going with the wind, but only twenty miles against
the wind. Second, the banking of the planes
against the air is more effective when going into
the wind than when traveling with it, and, therefore,
the speed at which you contact with the earth
is lessened to such an extent that a comparatively
easy landing is effected.
THE FOURTH STAGE.--After sufficient time has
been devoted to the long turns shorter turns may
be made, and these also require the same care,
and will give an opportunity to use the lateral
controls to a greater extent. Begin the turns, not
by an abrupt throw of the turning rudder, but
bring it around gently, correcting the turning
movement to a straight course, if you find the
machine inclined to tilt too much, until you get used
to the sensation of keeling over. Constant practice
at this will soon give confidence, and assure
you that you have full control of the machine.
THE FIGURE 8.--You are now to increase the
height of flying, and this involves also the ability
to turn in the opposite direction, so that you may
be able to experience the sensation of using the
stabilizers in the opposite direction. You will
find in this practice that the senses must take in
the course of the wind from two quarters now, as
you attempt to describe the figure 8.
This is a test which is required in order to obtain
a pilot's license. It means that you shall
be able to show the ability to turn in either direction
with equal facility. To keep an even flying
altitude while describing this figure in a wind, is
the severest test that can be exacted.
THE VOLPLANE.--This is the technical term for
a glide. Many accidents have been recorded owing
to the stopping of the motor, which in the
past might have been avoided if the character of
the glide had been understood. The only thing
that now troubles the pilot when the engine "goes
dead," is to select a landing place.
The proper course in such a case is to urge
the machine to descend as rapidly as possible, in
order to get a headway, for the time being. As
there is now no propelling force the glide is depended
upon to act as a substitute. The experienced
pilot will not make a straight-away glide,
but like the vulture, or the condor, and birds of
that class, soar in a circle, and thus, by passing
over and over the same surfaces of the earth, enable
him to select a proper landing place.
THE LANDING.--The pilot who can make a good
landing is generally a good flyer. It requires
nicety of judgment to come down properly. One
thing which will appear novel after the first altitude
flights are attempted is the peculiar sensation
of the apparently increased speed as the earth
comes close up to the machine.
At a height of one hundred feet, flying thirty
miles an hour, does not seem fast, because the surface
of the earth is such a distance away that particular
objects remain in view for some moments;
but when within ten feet of the surface the same
object is in the eye for an instant only.
This lends a sort of terror to the novice. He
imagines a great many things, but forgets some
things which are very important to do at this
time. One is, that the front of the machine must
be thrown up so as to bank the planes against the
wind. The next is to shut off the power, which
is to be done the moment the wheels strike the
ground, or a little before.
Upon his judgment of the time of first touching
the earth depends the success of safely alighting.
He may bank too high, and come down on the tail
with disastrous results. If there is plenty of field
room it is better to come down at a less angle, or
even keep the machine at an even keel, and the
elevator can then depress the tail while running
over the ground, and thus bring the machine to
rest.
Frequently, when about to land the machine
will rock from side to side. In such a case it is
far safer to go up into the air than to make the
land, because, unless the utmost care is exercised,
one of the wing tips will strike the earth and
wreck the machine.
Another danger point is losing headway, as the
earth is neared, due to flying at too flat an angle,
or against a wind that happens to be blowing particularly
hard at the landing place. If the motor
is still going this does not make so much difference,
but in a volplane it means that the descent
must be so steep, at the last moment of flight, that
the chassis is liable to be crushed by the impact.
FLYING ALTITUDE.--It is doubtful whether the
disturbed condition of the atmosphere, due to
the contour of the earth's surface, reaches higher
than 500 feet. Over a level area it is certain that
it is much less, but in some sections of the country,
where the hill ranges extend for many miles,
at altitudes of three and four hundred feet, the
upper atmosphere may be affected for a thousand
feet above.
Prof. Lowe, in making a flight with a balloon,
from Cincinnati to North Carolina, which lasted
a day and all of one night, found that during the
early morning the balloon, for some reason, began
to ascend, and climbed nearly five thousand
feet in a few hours, and as unaccountably
began to descend several hours before he landed.
Before it began to ascend, he was on the western
side of the great mountain range which extends
south from Pennsylvania and terminates in
Georgia. He was actually climbing the mountain
in a drift of air which was moving eastwardly,
and at no time was he within four thousand feet
of the earth during that period, which shows that
air movements are of such a character as to exert
their influence vertically to great heights.
For cross country flying the safest altitude is
1000 feet, a distance which gives ample opportunity
to volplane, if necessary, and it is a height
which enables the pilot to make observations of the
surface so as to be able to judge of its character.
But explanations and statements, and the experiences
of pilots might be detailed in pages, and
still it would be ineffectual to teach the art of flying.
The only sure course is to do the work on
an actual machine.
Many of the experiences are valuable to the
learner, some are merely in the nature of cautions,
and it is advisable for the beginner to learn what
the experiences of others have been, although they
may never be called upon to duplicate them.
All agree that at great elevations the flying
conditions are entirely different from those met
with near the surface of the ground, and the history
of accidents show that in every case where
a mishap was had at high altitude it came about
through defect in the machine, and not from gusts
or bad air condition.
On the other hand, the uptilting of machines,
the accidents due to the so-called "Holes in the
air," which have dotted the historic pages with
accidents, were brought about at low altitudes.
At from two to five thousand feet the air may be
moving at speeds of from twenty to forty miles
an hour,--great masses of winds, like the trade
stream, which are uniform over vast areas. To
the aviator flying in such a field, with the earth
hidden from him, there would be no wind to indicate
that he was moving in any particular direction.
He would fly in that medium, in any direction,
without the slightest sense that he was in a gale.
It would not affect the control of the machine,
because the air, though moving as a mass, would
be the same as flying in still air. It is only when
he sees fixed objects that he is conscious of the
movement of the wind.