Experimental Investigation of the Effects of Helicopter Rotor Design Parameters on Forward Flight Stall Characteristics
Final rept. Jan 1972-Dec 1973
UNITED AIRCRAFT RESEARCH LABS EAST HARTFORD CT
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An experimental investigation was conducted to determine the effects of number of blades, twist, aspect ratio, camber, taper ratio, and torsional frequency on helicopter rotor stall characteristics in forward flight. The tests were conducted in the low-speed UARL 4- x 6-ft wind tunnel with 4.7-ft- diameter model rotors having flapping articulation. Stall conditions were approached by means of increasing rotor shaft angle at fixed collective pitch. Torsional frequency was varied by using a special blade root flexure which would produce the required rigid blade torsional frequencies. Rotor performance, blade response, and boundary layer separation data were acquired to determine the occurrence and extent of blade stall.