The mathematical models of high-altitude long-endurance unmanned aerial vehicles (HALE UAV) engines with the corrected method of Reynolds number for engine components characteristics were built

and the corresponding programs were developed. The effects of extracting power from low-pressure spool on different small and medium thrust turbofans engine and the core engine

as well as the effects of extracting power from two spools on the engine were calculated and analyzed under high-altitude flight condition; the proper proportion of power extraction between different spools was analyzed. It is shown from the computation results that compared with extracting power from high-pressure spool under high-altitude flight condition

extracting power from low-pressure spool can observably improve the fan/compressor surge margins for turbofan without booster and the booster surge margins for turbofan engine with booster

remarkably increase the power extraction of turbofan without/with booster on the premise of maintaining engine operation stability; also this can realize a 9% to 14.8% improvement in spool speed

correlated mass flow and pressure ratio of the core engine for developing potential of the core engine.