Experimental Investigation Of Gust Response Of Hingeless Helicopter Rotors PDF Download

The vertical gust response and its alleviation for hingeless helicopter rotor blades in cruising flight is studied theoretically and experimentally. An evaluation is performed of the effectiveness of torsional stiffness variation in conjunction with chordwise center-of-gravity shift in alleviating the blade flapping response to decrease the root bending moment. The theoretical analysis utilizes the equations of motion of hingeless rotor blades exposed to vertical gusts in forward flight for the flapping, lagging, and elastic and rigid pitch degrees of freedom. The equations include the effect of steady-state deflections in the trim conditions and various hingeless rotor configurations such as precone, droop and torque offset as well as chordwise center-of-gravity shift and aerodynamic center offset. The experimental program involves the wind tunnel tests of a five-foot diameter rotor subject to a sinusoidal waveform gust. Testing involves variation of the blade chordwise center-of-gravity location, the blade torsional stiffness, rotor advance ratio, and vertical gust frequency. (Author).