Rotor unsteady aerodynamics research of a small-scale coaxial helicopter in hovering state

Based on the engineering reality, a calculation model of the rotor unsteady aerodynamics of a small coaxial helicopter in hovering state had been set up. An airfoil unsteady aerodynamic model was established by introducing a set of Leishman-Beddoes semi-empirical indicial response formulas; the aerodynamic interaction between upper and lower rotors of the coaxial helicopter was set up by bringing an interferential factor in the dynamic inflow model, and the Runge-Kutta method was used to obtain the numerical solution of the rigid flapping angle. According to the calculation and analysis, the thrust and torque responses to a rapid collective pitch increase in hovering state were obtained, and the direction response´s differences between the semi-differential and full-differential direction control modes were compared.