The effects of compressibility arising from high-tip-speed oper-ation on the flapping, thrust, and power of a helicopter rotor over a wide range of forward flight conditions are investigated by the use of numerical methods.nFor the particular set of airfoil characteristics used, the results indicated minor increases in rotor flapping and thrust arising from increasing rotor tip speed from 350 to 750 fps. The largest effect noted was an increase in profile-drag power on the advancing side of the disk that was proportional to the amount by which the blade-tip Mach number exceeded the drag-divergence Mach number. These effects of compressibility appeared to be independent of blade twist but are, of course, a function of the airfoil characteristics employed in the analysis.
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