THE MARGIN OF POWER is the power available above
that necessary to maintain horizontal flight.
THE MARGIN OF LIFT is the height an aeroplane can gain
in a given time and starting from a given altitude.
As an example, thus: 1,000 feet the first minute,
and starting from an altitude of 500 feet above
sea-level.
The margin of lift decreases with altitude, owing
to the decrease in the density of the air, which
adversely affects the engine. Provided the engine
maintained its impulse with altitude, then, if we
ignore the problem of the propeller, which I will
go into later on, the margin of lift would not
disappear. Moreover, greater velocity for a given
power would be secured at a greater altitude, owing
to the decreased density of air to be overcome.
After reading that, you may like to light your pipe
and indulge in dreams of the wonderful possibilities
which may become realities if some brilliant genius
shows us some day how to secure a constant power
with increasing altitude. I am afraid, however,
that will always remain impossible; but it is probable
that some very interesting steps may be taken in
that direction.
THE MINIMUM ANGLE OF INCIDENCE is the smallest
angle at which, for a given power, surface (including
detrimental surface), and weight, horizontal flight
can be maintained.
THE MAXIMUM ANGLE OF INCIDENCE is the greatest
angle at which, for a given power, surface (including
detrimental surface), and weight, horizontal flight
can be maintained.
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