Abstract:

ESDU 75018 gives formulae for specific air range that can then be integrated to give range under the assumptions that fuel consumption per unit engine output-shaft power (or equivalent power) is constant and that cruise is at constant lift/drag ratio or a parabolic law connects the lift and drag coefficients (in which case cruise at constant pressure height and either constant airspeed or power is considered). The fuel consumption assumption is discussed under practical conditions for both piston and turbo-prop engines and factors affecting consumption are considered. The selection of the speed for best range and the factors affecting its choice are discussed, and the range behaviour with speed illustrated graphically for aircraft powered by either piston (with or without supercharging) or turbo-prop engines.