Study on the lift and propulsive force shares to improve the flight performance of a compound helicopter

To investigate the effects of lift and propulsive force shares on flight performance,a compound helicopter model is derived.The model consists of a helicopter model,a wing model and a propeller model.At a low speed of 100 km/h,the Lift-to-Drag ratio(L/D)of the compound helicopter is improved when the wing provides 20.2%of the take-off weight.At high speeds,the L/D can be improved when the propeller provides the total propulsive force.Lowering the main rotor speed increases the wing lift share,however,the maximum L/D increases first and then decreases.The maximum L/D increases with decreasing the blade twist of the main rotor.Decreasing the blade twist from-16°to-8°increases the maximum L/D by 2.3%,and the wing lift share is increased from 65.0%to 74.7%.When the main rotor torque is balanced by the rudder,the maximum L/D is increased by 2.2%without changing the wing lift share.The wing should provide more lift as increasing the take-off weight,which reduces the induced power of the main rotor and increases the L/D.When increasing the take-off weight from 9500 kg to 11000 kg,the maximum L/D is increased by 6.5%,and the wing lift share is increased from 74.7%to 80.2%.