Parametric shimmy analysis

A more reliable parametric shimmy analysis model taking the elasticity of strut, the elasticity of damper linkage system and the influence of shimmy damping into consideration is set up in this paper. The Multiple-Scales-Method is utilized to obtain the expressions of stability condition and transition curve under the conditions of non resonant case, principal parametric resonance and combination resonance respectively. The parametric shimmy analysis for a real type of aircraft is carried out based on the perturbation analysis results, and the stability chart and critical taxiing velocities of two types of aircraft in the case of principal parametric resonance are given. It is indicated that there exist two critical taxiing velocities near which parametric shimmy is susceptible to occur, while the landing-gear system is stable when taxiing velocity is far from them. This characteristic makes the parametric shimmy distinct from the shimmy in general case. Because few previous studies of nose gear shimmy have dealt with parametric shimmy problem, the results given in this paper provide useful reference for aircraft design and maintenance.