Abstract:

ESDU 77015 gives simple formulae, derived from an analysis of a wide range of aircraft operating data, that enable still-air estimates of range, fuel used, and time based on cruise performance to be adjusted for the net loss of energy during climb (including acceleration) and during descent (including deceleration). The method, suitable for project estimates of block distance, fuel and time, applies to stages in which climb and descent are not substantial portions of flight. The formulae given for lost range and fuel apply to turbo-prop engined aircraft and to piston engined aircraft for which different formulae are given depending on whether the cruise was calculated using a lean mixture (best economy) or rich mixture (best power). The formulae for lost time depend on the ratio of climb or descent speed to cruise speed.