Studies of a Large-Scale Jet-Flap Rotor in the 40- By 80-Foot Wind Tunnel

The application of the jet flap to helicopter rotor blades has long been suggested as a possible means of improving high-speed performance of helicopters. The U.S. Army and NASA Ames began studies of one such application in the 1960's, culminating in wind-tunnel tests of a full-scale, jet-flap rotor in 1965. The rotor and test apparatus utilized for that investigation were designed and constructed under a U.S. Army contract by the French firm, Giravions Dprand. The results of those tests (ref. 1) showed the very high lift and high forward speed potential for this type of rotor. Specifically, lift coefficients twice those achievable with conventional rotors at advance ratios up to 0.50 were measured; for lift coefficients representative of today's rotors, operation was indicated to be feasible at conditions equivalent to 300 knots as a lifting and propelling rotor.