Dynamic Analysis And Nonlinear Characteristic Research On Landing Gear Shimmy

Aircraft shimmy is a common problem of the landing gear in the aircraft landing and taking-off process which leads to detrimental effects on the safety, maneuverability and economical efficiency of the aircraft. In the work of the paper, theoretical analysis, bifurcation method and dynamic simulation are applied to research on shimmy.Linear analysis model is established upon multiple DOFs considering tire deformation and flexibility of strut and shimmy damper. Parameters of landing gear structure and tire are studied to determine the effect on shimmy. Nonlinear dynamic model considering torsion and lateral bending of strut is constructed based on applied bifurcation theory. The process to obtain the region of torsional shimmy and lateral shimmy is shown in detail. The wheel separation distance and wheel moment of inertia are selected as important parameters to study the effect of co-rotation configuration on aircraft shimmy in comparison to the non-co-rotation configuration.With the 3D dynamic platform LMS Virtual.Lab Motion, flexible model of nose landing gear is built based on the actual data of a type of aircraft. Accuracy of the nose landing gear model is verified by experimental data. Models consisting of flexible nose landing gear and airframe both meet the shimmy criterion.The method dealing with aircraft shimmy due to the landing gear structural clearance is developed. Different conditions of structural clearance are simulated. It is concluded that structural clearance deteriorate the shimmy condition and serious oscillation of nose landing gear swivel angle occurs. Measures are taken aiming at the shimmy phenomenon caused by structural clearance in the terms of design and maintenance.