Analysis of Influence of Aircraft Flexibility on Nose Landing Gear Shimmy

The dynamics of nose landing gear shimmy is studied in this paper with a certain type of aircraft.Based on the multi-body dynamics theory,a dynamics model of shimmy is developed which takes into consideration the flexibility of nose landing gear and airframe by means of the component mode synthesis method,to investigate the stability of shimmy.The model is verified with the data of static tests and mode tests.Diagrams of the stable region are presented accordingly,formed by the taxiing speed and critical anti-shimmy damping coefficients,to explore the influence of the movement and flexibility of the airframe.The result shows that,the initial angle of nose wheel contributes little to shimmy analysis.A simplified method,which replaces the flexibility of the nose landing gear by the connection stiffness between the nose landing gear and airframe,is not accurate enough and can only be applied to qualitative analysis.The movement of the rigid airframe exerts little influences on the critical damping coefficient.However,the flexibility of the airframe has considerable influence and it may increase the critical damping coefficient by 12.1% on the average at mid and high speeds.