It is a mistaken idea that flying machines must be operated at extreme
altitudes. True, under the impetus of handsome prizes, and the incentive
to advance scientific knowledge, professional aviators have ascended to
considerable heights, flights at from 500 to 1,500 feet being now
common with such experts as Farman, Bleriot, Latham, Paulhan, Wright and
Curtiss. The altitude record at this time is about 4,165 feet, held by
Paulhan.
One of the instructions given by experienced aviators to pupils, and for
which they insist upon implicit obeyance, is: "If your machine gets more
than 30 feet high, or comes closer to the ground than 6 feet, descend at
once." Such men as Wright and Curtiss will not tolerate a violation of
this rule. If their instructions are not strictly complied with they
decline to give the offender further lessons.
Why This Rule Prevails.
There is good reason for this precaution. The higher the altitude the
more rarefied (thinner) becomes the air, and the less sustaining power
it has. Consequently the more difficult it becomes to keep in suspension
a given weight. When sailing within 30 feet of the ground sustentation
is comparatively easy and, should a fall occur, the results are not
likely to be serious. On the other hand, sailing too near the ground
is almost as objectionable in many ways as getting up too high. If the
craft is navigated too close to the ground trees, shrubs, fences and
other obstructions are liable to be encountered. There is also the
handicap of contrary air currents diverted by the obstructions referred
to, and which will be explained more fully further on.
How to Make a Start.
Taking it for granted that the beginner has familiarized himself with
the manipulation of the machine, and especially the control mechanism,
the next thing in order is an actual flight. It is probable that his
machine will be equipped with a wheeled alighting gear, as the skids
used by the Wrights necessitate the use of a special starting track.
In this respect the wheeled machine is much easier to handle so far as
novices are concerned as it may be easily rolled to the trial grounds.
This, as in the case of the initial experiments, should be a clear,
reasonably level place, free from trees, fences, rocks and similar
obstructions with which there may be danger of colliding.
The beginner will need the assistance of three men. One of these should
take his position in the rear of the machine, and one at each end. On
reaching the trial ground the aviator takes his seat in the machine and,
while the men at the ends hold it steady the one in the rear assists in
retaining it until the operator is ready. In the meantime the aviator
has started his motor. Like the glider the flying machine, in order to
accomplish the desired results, should be headed into the wind.
When the Machine Rises.
Under the impulse of the pushing movement, and assisted by the motor
action, the machine will gradually rise from the ground--provided it
has been properly proportioned and put together, and everything is in
working order. This is the time when the aviator requires a cool head,
At a modest distance from the ground use the control lever to bring the
machine on a horizontal level and overcome the tendency to rise. The
exact manipulation of this lever depends upon the method of control
adopted, and with this the aviator is supposed to have thoroughly
familiarized himself as previously advised in Chapter XI.
It is at this juncture that the operator must act promptly, but with the
perfect composure begotten of confidence. One of the great drawbacks in
aviation by novices is the tendency to become rattled, and this is much
more prevalent than one might suppose, even among men who, under other
conditions, are cool and confident in their actions.
There is something in the sensation of being suddenly lifted from the
ground, and suspended in the air that is disconcerting at the start,
but this will soon wear off if the experimenter will keep cool. A few
successful flights no matter how short they may be, will put a lot of
confidence into him.
Make Your Flights Short.
Be modest in your initial flights. Don't attempt to match the records
of experienced men who have devoted years to mastering the details of
aviation. Paulhan, Farman, Bleriot, Wright, Curtiss, and all the rest of
them began, and practiced for years, in the manner here described, being
content to make just a little advancement at each attempt. A flight of
150 feet, cleanly and safely made, is better as a beginning than one of
400 yards full of bungling mishaps.
And yet these latter have their uses, provided the operator is of a
discerning mind and can take advantage of them as object lessons. But,
it is not well to invite them. They will occur frequently enough under
the most favorable conditions, and it is best to have them come later
when the feeling of trepidation and uncertainty as to what to do has
worn off.
Above all, don't attempt to fly too high. Keep within a reasonable
distance from the ground--about 25 or 30 feet. This advice is not given
solely to lessen the risk of serious accident in case of collapse, but
mainly because it will assist to instill confidence in the operator.
It is comparatively easy to learn to swim in shallow water, but the
knowledge that one is tempting death in deep water begets timidity.
Preserving the Equilibrium.
After learning how to start and stop, to ascend and descend, the next
thing to master is the art of preserving equilibrium, the knack of
keeping the machine perfectly level in the air--on an "even keel," as
a sailor would say. This simile is particularly appropriate as all
aviators are in reality sailors, and much more daring ones than those
who course the seas. The latter are in craft which are kept afloat by
the buoyancy of the water, whether in motion or otherwise and, so long
as normal conditions prevail, will not sink. Aviators sail the air in
craft in which constant motion must be maintained in order to ensure
flotation.
The man who has ridden a bicycle or motorcycle around curves at anything
like high speed, will have a very good idea as to the principle of
maintaining equilibrium in an airship. He knows that in rounding curves
rapidly there is a marked tendency to change the direction of the motion
which will result in an upset unless he overcomes it by an inclination
of his body in an opposite direction. This is why we see racers lean
well over when taking the curves. It simply must be done to preserve the
equilibrium and avoid a spill.
How It Works In the Air.
If the equilibrium of an airship is disturbed to an extent which
completely overcomes the center of gravity it falls according to the
location of the displacement. If this displacement, for instance, is at
either end the apparatus falls endways; if it is to the front or rear,
the fall is in the corresponding direction.
Owing to uncertain air currents--the air is continually shifting and
eddying, especially within a hundred feet or so of the earth--the
equilibrium of an airship is almost constantly being disturbed to some
extent. Even if this disturbance is not serious enough to bring on
a fall it interferes with the progress of the machine, and should
be overcome at once. This is one of the things connected with aerial
navigation which calls for prompt, intelligent action.
Frequently, when the displacement is very slight, it may be overcome,
and the craft immediately righted by a mere shifting of the operator's
body. Take, for illustration, a case in which the extreme right end
of the machine becomes lowered a trifle from the normal level. It is
possible to bring it back into proper position by leaning over to the
left far enough to shift the weight to the counter-balancing point. The
same holds good as to minor front or rear displacements.
When Planes Must Be Used.
There are other displacements, however, and these are the most frequent,
which can be only overcome by manipulation of the stabilizing planes.
The method of procedure depends upon the form of machine in use. The
Wright machine, as previously explained, is equipped with plane ends
which are so contrived as to admit of their being warped (position
changed) by means of the lever control. These flexible tip planes move
simultaneously, but in opposite directions. As those on one end rise,
those on the other end fall below the level of the main plane. By this
means air is displaced at one point, and an increased amount secured in
another.
This may seem like a complicated system, but its workings are simple
when once understood. It is by the manipulation or warping of these
flexible tips that transverse stability is maintained, and any tendency
to displacement endways is overcome. Longitudinal stability is governed
by means of the front rudder.
Stabilizing planes of some form are a feature, and a necessary feature,
on all flying machines, but the methods of application and manipulation
vary according to the individual ideas of the inventors. They all tend,
however, toward the same end--the keeping of the machine perfectly level
when being navigated in the air.
When to Make a Flight.
A beginner should never attempt to make a flight when a strong wind is
blowing. The fiercer the wind, the more likely it is to be gusty and
uncertain, and the more difficult it will be to control the machine.
Even the most experienced and daring of aviators find there is a limit
to wind speed against which they dare not compete. This is not because
they lack courage, but have the sense to realize that it would be silly
and useless.
The novice will find a comparatively still day, or one when the wind is
blowing at not to exceed 15 miles an hour, the best for his experiments.
The machine will be more easily controlled, the trip will be safer, and
also cheaper as the consumption of fuel increases with the speed of the
wind against which the aeroplane is forced.