The effect of variation of gear ratio on the performance of a variable-pitch airscrew for a high-speed aeroplane

Abstract

The effect of change of gear ratio has been examined in the case of a four-bladed airscrew of 14 ft. diameter absorbing 2,000 b.h.p. at 37,000 ft. at a forward speed of 450 m.p.h. with a given engine speed (3,700 r.p.m.). Using the limited data at present available for the lift and drag of an airscrew blade section at high Mach number, it appears that for a sufficiently low gear ration the higher working lift coefficient of each blade element may increase the induced power loss such much that it is not off-set by the reduction in compressibility loss brought about by the decreased Mach numbers of the blade sections.