COMPARISON OF THEORETICAL AND EXPERIMENTAL MODEL ROTOR BLADE VIBRATORY SHEAR FORCES
UNITED TECHNOLOGIES CORP STRATFORD CT SIKORSKY AIRCRAFT DIV
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An investigation was undertaken to obtain quantitative measurements of the vibratory forcing functions from the blades of rotary wing aircraft in the flight speed range encompassing both pure and compound helicopter operation. These measurements were made using dynamically scaled model rotor blades mounted on a specially instrumented rotor head. Testing was accomplished over a range of equivalent forward speeds from 75 to 300 knots and over a range of full-scale rotor lifts from zero to 40,000 lb. In addition to rotor performance, the final data include ten harmonics of the orthogonal blade root shear forces, rotor blade bending moments, and rotor control loads. A portion of the experimental results was correlated with a fully coupled aeroelastic analysis which included the effects of wake induced velocities. It was found that the inclusion of these effects improved the correlation of the flatwise shear forces over that obtained assuming uniform inflow.