into the distance.
"An airplane is a machine...." he would begin again with an air of
utter despondency. That was certainly no news to cadets. They had an
idea that it might be a machine, and wanted to know more about it.

"An airplane is a machine with lift-generating surfaces attached to a
frame which carries an engine, fuel, aviator, and devices by which he
steers, balances, and controls his craft," the mournful flight
sergeant was finally able to convince them.

Lift-generating surfaces--these are the bases of all flying. Every one
knows, for instance, that a paper dart, instead of falling directly to
the floor, sails in a gliding angle for some distance before crashing.
Lift is generated under those plane surfaces moving through the
air--and the lift keeps that paper dart gliding. Little eddies of air
are compressed under its tiny wings. Imagine an engine in the dart,
propelling it at some speed. Instead of having to nose down to get
enough speed to generate lift under its wings, the dart would be able
to fly on the level, or even climb a bit.

Just so with an airplane. A gliding airplane about to land with power
shut off is that paper dart on a large scale. The airplane flying is
the dart with power. To make the airplane safe to fly, to give control
to the pilot so that he may steer it where he wants to, there is a
rudder, moved by a rudder-bar under the foot of the pilot. It is
impossible to turn a swiftly moving airplane in the air by the rudder
alone. It must be banked to prevent skidding, even as a race-track is
banked high on the turns. On its side an airplane will cushion its own
bank of proper degree by the use of ailerons. These ailerons are
sections of the wing-tips which may be moved either up or down. They
are counterbalanced so that movement of the left down gives you the
right aileron up. With left aileron down, the lift of the left wing is
increased, and it tips up; at the same time the lift of the right wing
is decreased, and it sags down. In that way the airplane is tipped up
for a bank. These ailerons, wing sections, really, are controlled by
a device known as the joy-stick in the cockpit.

We have seen how an airplane is made to tip and turn. Before a machine
is under control we must be able to climb, or come down to the ground
for a landing. Vertical control of an airplane is attained by the use
of elevators, flaps on the tail plane acting as horizontal rudders. A
pull-back on the joy-stick