By using windmill anemometers inflow fluctuation of model-helicopter rotor have been measured; results show following characteristics -- thrust reduction is closely related to increment of downwash component or inflow near rotor tip induced by strong vortex ring which appears when rate of descent is nearly equal to induced velocity generated in hovering state; torque variation is not observable for low collective pitch operation of rotor having twisted blades but is recognized for high pitch operation, particularly for rotor having untwisted blades; this is explained by blade element theory with measured inflow distribution.
Induced flow variation of helicopter rotor operating in vortex ring state
J Aircraft
Journal of Aircraft ; 5 , n 4
1968
6 pages
Aufsatz (Zeitschrift)
Englisch
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