Abstract: A method to predict the aerodynamic characteristics of a rotor at high advanced ratio is proposed which takes into consideration the particularity of the compound high speed helicopter rotor with a severe reverse flow region. The method is then used to calculate the aerodynamic performance of an H-34 rotor with various combinations of advanced ratios and rotor angles of attack and the results are compared with wind tunnel test data. The article further analyzes the effect of reverse flow region on the performance of the H-34 rotor at various high advanced rotor ratios as well as on the angle of attack, the lift and drag coefficients of the blade sections. The results show that the larger the area of the reverse flow region, the greater is its influence on the rotor performance and angle of attack, lift and drag coefficients of the blade sections. Furthermore, the angle of attack of a blade section exhibits rapid change on the boundary of the reverse flow region. There are obvious differences between the angle of attack, the lift and drag coefficients of the blade sections inside and outside the reverse flow region.

Key words: helicopter, high advanced ratio rotor, reverse flow region, aerodynamic characteristic, flapping motion, induced velocity