Abstract:
The report describes a simplified 8-point strip theory method of calculating the free-air performance of a propeller up to tip Mach numbers near the velocity of sound. It is based on the assumptions of R. & M. 1674 and 1849 together with the further simplifying assumption that the curve is straight (valid below the stall) and that the curve also is straight (valid for J > 1.0). The report includes tables of parameters which are required in the calculations as functions of J, r, and N for eight standard radii (r, = 0.3, 0.45, 0.6, 0.7, 0.8, 0.9, 0.95, 0.975) for the range of values of J from 1.0 t o 7.0; these are of universal application. In addition, tables of section data for various section shapes are required; these are given for Clark Y sections over a range of thickness in R. & M. 2036; they were derived, by methods described in R. & M. 2020, from overall measurements of thrust and torque on full scale propellers at low values of J in the Royal Aircraft Establishment 24-ft. tunnel and are subject to revision in the light of subsequent experimental research.
