FLIGHT PERFORMANCE AND TRAJECTORY PREDICTION OF THE COAXIAL HELICOPTER IN AUTOROTATION

In this paper, the flight dynamics and kinematics models were established for the coaxial rigid helicopter in autorotation process, based on the principle of point-mass model. The XH-59A helicopter was chosen to be an example. The aerodynamic forces of rotor and fuselage were superimposed. The rotor performance prediction was based on engineering empirical formula. The dangerous region of the helicopter is determined, and the parameters varying with descent angle in stable autorotation state were calculated for flight speed 10m/s and 30m/s respectively. Result shows that with the increase of descent angle, the rotor thrust, the collective pitch and the helicopter horizontal velocity are decreased, while the rotating speed of the rotor and descent rate are increased. The higher the flight speed is, the higher the thrust and descent rate are, and the smaller the pitch angle is.