Analysis of ground resonance for helicopters with different elastomeric lag damper connections

An analytical model is developed for the dynamic stability analysis of helicopter rotor/fuselage coupled systems with general connections or inter-blade connections for the nonlinear elastomeric lag dampers. Within this analytical model, the factors as unsteady aerodynamic and blade flap/lead-lag coupled motion are both considered. Via a convert from the fuselage equivalent model into the fuselage instantaneous wheel axis, the fuselage roll and the pitch motion are both involved. Through an application of the improved nonlinear VKS model based on complex modulus, for the cases of general connections and inter-blade connections for the nonlinear elastomeric lag dampers, the small disturbance momental equation is given. The method of eigenvalue analysis is used to investigate the ground resonance stability of the helicopter rotor/body coupled system with two connections of dampers. The results of engineering examples show that the method possesses a clear physical conception and is convenient for use.