large.

5. Camber.--Since such an aeroplane would be of low velocity, and
therefore possess a large angle of incidence, a large camber would be
necessary.

Let us now consider the essentials for an aeroplane of maximum velocity
for its power, and possessing merely enough lift to get off the ground,
but no margin of lift.

1. Comparatively HIGH VELOCITY.

2. A comparatively SMALL SURFACE, because, being of greater velocity
than the maximum climber, a greater mass of air will be engaged for
a given surface and time, and therefore a smaller surface will be
sufficient to secure the requisit lift.

3. A small angle relative to the propeller thrust, since the latter
coincides with the direction of motion.

4. A comparatively small angle of incidence by reason of the high
velocity.

5. A comparatively small camber follows as a result of the small angle
of incidence.

SUMMARY.

Essentials for Maximum Essentials for Maximum
Climb. Velocity

1. Low velocity. High velocity.
2. Large surface. Small surface.
3. Large angle relative to Small angle relative to
propeller thrust. propeller thrust.
4. Large angle relative to Small angle relative to direction
direction of motion. of motion.
5. Large camber. Small camber.

It is mechanically impossible to construct an aeroplane of reasonable
weight of which it would be possible to very the above opposing
essentials. Therefore, all aeroplanes are designed as a compromise
between Climb and Velocity.

As a rule aeroplanes are designed to have at low altitude a slight
margin of lift when the propeller thrust is horizontal.

ANGLES OF INCIDENCE (INDICATED APPROXIMATELY) OF AN AEROPLANE DESIGNED
AS A COMPROMISE BETWEEN VELOCITY AND CLIMB, AND POSSESSING A SLIGHT
MARGIN OF LIFT AT A LOW ALTITUDE AND WHEN THE THRUST IS HORIZONTAL

MINIMUM ANGLE.

This gives the greatest velocity during horizontal flight at a low
altitude. Greater velocity would be secured if the surface, angle, and
camber were smaller and designed to just maintain horizontal flight
with a horizontal thrust. Also, in such case, the propeller would not
be thrusting downwards, but along a horizontal line which is obviously
a more efficient arrangement if we regard the aeroplane merely from one
point of view, i.e., either with reference