Calculation method of blade element aerodynamic loads based on small perturbation theory

A calculation method of blade element aerodynamic loads based on small perturbation theory is established for helicopter flight simulation application. The method synthesizes flap-lag-torsion elastic rotor blade mode,couples rotor dynamic inflow,unsteady aerodynamics model with dynamic stall and rotor trimming model. The entire model is developed in a standard state-space form. To verify this model,the UH-60 A helicopter is taken as an example,and the effects of yaw flow on rotor aerodynamic performance are studied at low speed flight and high speed flight. It is shown that yaw flow has a greater effect on rotor aerodynamic performance at high speed flight. Blade induced velocity fields and aerodynamic loads are simulated,and the results are compared with flight test data. It is shown by the results that the method can accurately predict the unsteady aerodynamic rotor loads in steady flight by capturing its variational characteristics along blade azimuthal locations,and it is still applicable for high speed flight.