HELICOPTER ROTOR LIFT DISTRIBUTIONS FOR MINIMUM-INDUCED POWER LOSS

A method is described for solving the minimum-induced loss (MIL) rotor design problem. First, the generalized Betz condition for MIL rotors is developed. Because the resulting lift distributions would generally exceed the maximum blade lift coefficient on the retreating side of t he rotor, the necessary conditions are extended to include constraints on the lift. A method for solving for the optimum lift distribution u sing finite elements is described. Numerical results are presented for a typical rotor in forward flight. The MIL rotor may have on the orde r of 10% less induced power loss than a typical unoptimized rotor.