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# Power Required

Ver - 2014.07.12

In turbine powered aircraft thrust is the most useful way to calculate aircraft performance because turbine engine thrust is very predictable.

However, piston engine aircraft do not lend themselves to predictable thrust measurement because of changing prop pitch, RPM, and carburetor manifold pressure. Power is a better way to calculate piston engine performance.

 Weight: 1600 mph: 50 (73 ft/sec) L/D: 7 Prop(eff): .80 HP(theory): 30 HP(actual): 36

 Weight(lb): Speed(mph): L/D(ratio): Prop(eff): (typ .75-.90)

Here are some important concepts

f = force, s = speed, d = distance

Force(f) times a distance(d) equals energy (e).
f(lb) * d(ft) = e
Force times a speed is power.
f(lb) * s(ft/sec) = p
So...
550ft / lbs / sec = 1hp
metric would be...
75m / kg / sec = 1hp

To convert HP to thrust
HP * 75 / s(m/s) = thrust in kg
HP * 550 / s(ft/sec) = thrust in lbs

Also...
745.7 watts = 1HP