Definitions for the Beginner

An aerobatic model has a wide performance range. The optimal propeller for slowspeed
3-D isn’t necessarily the right propeller for precision flight.
Definitions for the Beginner
Gas-powered engines are simple to run.
This 2.4 cu. in. Fox typically turns a 20 x
10 propeller.
Maximum rpm from an engine isn’t
always practical; that demand could cause
serious damage over a long period.
Altitude: Air density reduces with altitude. This is reflected in the
constant number in the thrust formula.
Altitude (Feet) Constant
Sea Level 0.000011127
1,000 0.000010806
2,000 0.000010490
3,000 0.000010182
4,000 0.000009881
5,000 0.000009581
6,000 0.000009301
ARF: Almost ready to fly.
BHP: Brake horsepower.
CID: Cubic inch displacement.
mph: Miles per hour.
PLF: Propeller Load Factor (diameter2 x pitch).
PL: Power loading (ounces of model weight per cubic inch of
displacement).
rpm: Revolutions per minute.
Stability: A model’s ability to return to level flight after a gust or when
controls are centered.
Torque: Turning force in inch-ounce.
Trim: Adjust controls for level flight.
TWR: Thrust-to-weight ratio (measured in percentage).
Wing area: Constant chord-chord x span (in inches)
Tapered-(Root Chord + Tip Chord) x Span ÷ 2
Divide square inches by 144 to get square feet.
Wing loading: Ounces of model weight divided by the wing area in
square feet. The result is ounces per square foot of area. MA
—A.G. Lennon
56 MODEL AVIATION
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