Flight Measurements of Helicopter Blade Motion with a Comparison between Theoretical and Experimental Results

Measurements of flapping motion, in-plane motion and blade distortion of helicopter rotors are presented for selected conditions of flight at tip-speed ratios ranging from 0.12 to 0.25. Flapping and in-plane measurements are reduced to Fourier series coefficients and are tabulated. Values of measured flapping motion are compared with theoretical calculated values and agreement is found to be good enough to render theory useful within range of conditions tested, in such problems as estimation of control displacement for trim and static-stability determination and in design of rotor hub.