to velocity OR climb.

OPTIMUM ANGLE (Thrust horizontal)

The velocity is less than at the smaller minimum angle, and, as
aeroplanes are designed to-day, the area and angle of incidence of the
surface is such as to secure a slight ascent at a low altitude. The
camber of the surface is designed for this angle of incidence and
velocity. The lift-drift ratio is best at this angle.

BEST CLIMBING ANGLE

The velocity is now still less by reason of the increased angle
producing increase of drift. Less velocity at A GIVEN ANGLE produces
less lift, but the increased angle more or less offsets the loss of
lift due to the decreased velocity, and in addition, the thrust is now
hauling the aeroplane upwards.

MAXIMUM ANGLE

The greater angle has now produced so much drift as to lessen the
velocity to a point where the combined lifts from the surface and from
the thrust are only just able to maintain horizontal flight. Any greater
angle will result in a still lower lift-drift ratio. The lift will then
become less than the weight and the aeroplane will consequently fall.
Such a fall is known as "stalling" or "pancaking."

NOTE.--The golden rule for beginners: Never exceed the Best Climbing
Angle. Always maintain the flying speed of the aeroplane.

By this means, when the altitude is reached where the margin of
lift disappears (on account of loss of engine power), and which is,
consequently, the altitude where it is just possible to maintain
horizontal flight, the aeroplane is flying with its thrust horizontal
and with maximum efficiency (as distinct from engine and propeller
efficiency).

The margin of lift at low altitude, and when the thrust is horizontal,
should then be such that the higher altitude at which the margin of lift
is lost is that altitude at which most of the aeroplane's horizontal
flight work is done. That ensures maximum velocity when most required.

Unfortunately, where aeroplanes designed for fighting are concerned, the
altitude where most of the work is done is that at which both maximum
velocity and maximum margin of lift for power are required.

Perhaps some day a brilliant inventor will design an aeroplane of
reasonable weight and drift of which it will be possible for the pilot
to vary at will the above-mentioned opposing essentials. Then we shall
get maximum velocity, or maximum margin of lift, for power as required.
Until then the design of the aeroplane must remain a compromise between
Velo