an effect which may render the aeroplane unmanageable if the
spiral is one of very small radius and the engine is revolving with
sufficient speed to produce a material gyroscopic effect. Such
gyroscopic effect should, however, slightly _assist_ the pilot to
navigate a small spiral if he will remember to (1) make _right-hand_
spirals in the case of a "pusher," (2) make _left-hand_ spirals in the
case of a "tractor." The effect will then be to keep the nose up and
prevent a nose-dive. I say "slightly" assist because the engine is, of
course, throttled down for a spiral descent, and its lesser revolutions
will produce a lesser gyroscopic effect.

On the other hand, it might be argued that if the aeroplane gets into a
"spin," anything tending to depress the nose of the machine is of value,
since it is often claimed that the best way to get out of a spin is
to put the machine into a nose-dive--the great velocity of the dive
rendering the controls more efficient and better enabling the pilot to
regain control. It is, however, a very contentious point, and few are
able to express opinions based on practice, since pilots indulging in
nose-dive spins are either not heard of again or have usually but a hazy
recollection of exactly what happened to them.

GLIDING DESCENT WITHOUT PROPELLER THRUST.--All aeroplanes are, or should
be, designed to assume their correct gliding angle when the power and
thrust is cut off. This relieves the pilot of work, worry, and danger
should he find himself in a fog or cloud. The pilot, although he may not
realize it, maintains the correct attitude of the aeroplane by observing
its position relative to the horizon. Flying into a fog or cloud the
horizon is lost to view, and he must then rely upon his instruments--(1)
the compass for direction; (2) an inclinometer (arched spirit-level)
mounted transversely to the longitudinal axis, for lateral stability;
and (3) an inclinometer mounted parallel to the longitudinal axis, or
the airspeed indicator, which will indicate a nose-down position by
increase in air speed, and a tail-down position by decrease in air
speed.

The pilot is then under the necessity of watching three instruments
and manipulating his three controls to keep the instruments indicating
longitudinal, lateral, and directional stability. That is a feat beyond
the capacity of the ordinary man. If, however, by the simple movement
of throttling down the power and thrust, he can be relieved of