Evening star. [volume] (Washington, D.C.) 1854-1972, 1911-01-08

TT is not till one begins to take an interest
in flying machines that he realizes what
wonderful thing the air is, and what strength
it has. Of course once in awhile one sees
chimneypots blown off, and states scattering
from the roofs of houses; but that is only in
great gales, which occur perhaps once or
twice year. But if one is going to take any
interest in flying, even if only as spectator
at an aviation meeting, it is most important
to have knowledge of the subject. And,
what is even more important, one must real
ize that wind is hardly ever steady. even
current of air; but is generally made up of a
series of gusts which, to the man who is fly
ing, act much the same as do the waves at
sea to small boat.
The flying man IS far worse off than the
sailor; for one can always see wave of
water coming, and handle the boat accord
ingly, whereas with an air wave one cannot
tell, till it has struck the machine, just when
it is coming, or how big and strong it is going
to be. 1t is one of the troubles of flying
men that the people who come to see them
fly do not know about these wind waves, and
SO expect them to fly in weather that is
really dangerous, although it may appear fine.
On a great open plain, miles and miles
wide, such as that over which the aviation
meetings at Rheims are held, there is nothing
to interfere with the wind, and consequently
it blows steadily, with hardly any gusts
or waves. 1t is then possible to fly in quite
strong winds. On the other hand. on a
small ground, or where there are hills and
banks and trees all round, the wind, even
when blowing comparatively gently, comes
in dangerous waves, swirls, and eddies, just
like the eddies and whirlpools in a stream
that has rocks or other distractions to inn
pede the flow of water.
How to Ride Air Waves
Nov, to understand properly the effects
of these waves on an aeroplane it is
necessary first to understand that the ma
chine is held in the air because the pace at
which it is driven by its propeller produces
pressure under its wings, or planes, and this
pressure lifts it up. If it is driven faster,
it makes greater pressure, and naturally it
lifts higher. If it is driven slower, it makes
less pressure. and then it falls.
1t is easy to understand that such heavy
thing as an aeroplane will not change its
speed very quickly. Even a light mono
plane will weigh four hundred to five hun
dred pounds, and one of the big biplanes
may weigh anything between eight hundred
pounds and a ton, and of course when they
are flying they have great momentum.
Therefore, suppose a machine to be flying
at speed of thirty-ive miles an hour over
the ground in a gentle wind, and suppose a
gust to meet it that is travelling ten miles
an hour faster than the wind in which it was
originally flying. What is the effect? The
machine cannot at once slow down; but
simply charges into that gust at thirty-ive
miles an hour. Consequently, the pressure
on the wings is increased and the machine
promptly rises.
But consider the effect of opposite con-
ditions. Suppose the machine had slowed
down in relation to the earth, so as to get
to its proper flying speed in relation to that
gust of wind. Presently it gets right
through the gust and into the lull the other
side, just as boat will ride over a wave
and fall into the trough between the waves.
This time the effect is that it is flying too
slowly for the patch of slow wind that fol-
lows the gust, and consequently the pressure
under the planes is decreased, and the ma
chine drops till it either hits the ground
(when it may or may not be broken, accord
ing to the pilots skill in landing), or else
picks up its speed again, and produces the
necessary pressure.
The sudden drop is most disconcerting,
and is the cause of many accidents, espe-
cially to those who are comparative novices
as aviators, and SO do not fly high enough to
leave room for sudden drop of this sort.
This is what is known to aviators as falling
into a D0cket - Or into "a hole in the wind y