Aeromechanical Stability of Rotor/Fuselage Coupling System in Helicopter Ground Taxiing

When a helicopter is ground taxiing, the dynamic characteristics of the landing gear wheels change with the taxiing speed, and the rotor generates significant aerodynamic forces. Therefore, the dynamic stability of the rotor/fuselage coupling system when a helicopter is ground taxiing is an aeromechanical stability issue that requires consideration of rotor aerodynamics. In this paper, the aeromechanical dynamic model and analytical method of the rotor/fuselage coupling system in helicopter ground taxiing are presented, including the aerodynamic forces of the rotor blades, the flapping and lagging motions of the blades, as well as the pitching, rolling, and lateral motions of the fuselage. The aeromechanical stabilities of the rotor/fuselage coupling system under different taxiing speeds are calculated. The calculation results show that with the increase in taxiing speed, the frequencies of the lateral and rolling motions of the fuselage decrease and coincide with the frequency of the regressing lag motion of the rotor, causing a decrease in the damping of the rolling motion of the fuselage and a reduction in the aeromechanical stability. When considering the aerodynamic forces, the critical instability taxiing speed increases and the range of instability taxiing speeds decreases compared to when not considering the aerodynamic forces.