Effect of active blade pitch control on helicopter rotor performance

In order to find out the influence rule and the essence of the effect of active blade pitch control on helicopter rotor performance, a rotor aerodynamic model was built firstly in consideration of the impact of second order harmonic blade pitch control, and then corresponding helicopter flight dynamic model was established. Rotor power was taken as the evaluation basis to investigate the effect of second order harmonic blade pitch control on rotor performance in trimming conditions. For the sample helicopter, the rotor power obtained with any second order harmonic blade pitch control increases when advance ratio is 0.2; 5% rotor power reduction can be achieved by second order harmonic blade pitch control with amplitude of 1.5° and initial phase of 90°when advance ratio is 0.35. By analyzing the distribution of angle of attack and drag coefficient on rotor disc of sample helicopter, the essence of using second order harmonic blade pitch control to improve rotor performance was summarized: in the high speed and high load status, an appropriate second order harmonic blade pitch control can improve the distribution of angle of attack on rotor disc, and delay the occurrence of retreating blade stall, thus decreasing the rotor power eventually and improving the rotor performance effectively.