on the outside of
the turn, travelling with greater velocity, and therefore securing a
greater reaction than the lower wing, thus tending to tilt the aeroplane
over still more. The aeroplane is now almost upside-down, _but_ its
attitude relative to the direction of motion is correct and the
controlling surfaces are all of them working efficiently. The recovery
of a normal attitude relative to the Earth is then made as illustrated
in sketch C.

The pilot must then learn to know just the angle of bank at which the
margin of lift is lost, and, if a sharp turn necessitates banking beyond
that angle, he must "nose-down."

In this matter of banking and nosing-down, and, indeed, regarding
stability and control generally, the golden rule for all but very
experienced pilots should be: _Keep the aeroplane in such an attitude
that the air pressure is always directly in the pilot's face._ The
aeroplane is then always engaging the air as designed to do so, and both
lifting and controlling surfaces are acting efficiently. The only
exception to this rule is a vertical dive, and I think that is obviously
not an attitude for any but very experienced pilots to hanker after.

SPINNING.--This is the worst of all predicaments the pilot can find
himself in. Fortunately it rarely happens.

It is due to the combination of (1) a very steep spiral descent of small
radius, and (2) insufficiency of keel-surface behind the vertical axis,
or the jamming of the rudder and/or elevator into a position by which
the aeroplane is forced into an increasingly steep and small spiral.

Owing to the small radius of such a spiral, the mass of the aeroplane
may gain a rotary momentum greater, in effect, than the air pressure of
the keel-surface or controlling surfaces opposed to it; and, when once
such a condition occurs, it is difficult to see what can be done by the
pilot to remedy it. The sensible pilot will not go beyond reasonable
limits of steepness and radius when executing spiral descents.

[Illustration: Nose Dive Spin.]

In this connection every pilot of an aeroplane fitted with a rotary
engine should bear in mind the gyroscopic effect of such engine. In the
case of such an engine fitted to a "pusher" aeroplane, its effect when a
left-hand turn is made is to depress the nose of the machine. If fitted
to a "tractor" it is reversed, so the effect is to depress the nose
if a right-hand turn is made. The sharper the turn, the greater such
effect--