Wind-tunnel tests on a 12-ft diameter helicopter rotor

Abstract

Measurements of the thrust, torque and flapping angle for a 12-ft diameter rotor over a range of blade angle, shaft inclination and tip-speed ratio have been made to give information on the validity of the standard rotor theory and of the effect of stalling on the retreating blade. Good agreement with the theory was obtained over the normal operating range, using aerofoil characteristics determined from the measurements in the static thrust condition. Stalling was found to be progressive in character showing first by an increase in torque and flapping angle and later by a fall in thrust, as compared with the calculated values.