Stability Investigation of SHIMMY Phenomenon of Aircraft Landing Gear

Document Type : Original Article

Authors

• Anooshirvan Farshidianfar
• Mostafa Toofani

10.22067/fum-mech.v22i2.10617

Abstract

Shimmy is a self-excited oscillatory, combined lateral-yaw motion of the landing gear caused by the interaction between dynamic tyre behavior and landing gear structural dynamics. Initially, the models for evaluating shimmy stability remaineds linear. Although linear model will usually reveal basic characteristics, it will generally fail to accurately predict the behavior of a landing gear system. This study treats the torsional dynamics of the lower parts of the landing gear as a multi-degree of freedom mechanical system and tire elasticity according to the elastic string theory. First they are linearized. Then eigenvalues are computed, solving analytically the stability boundaries with a parameter space method and numerical solution by simulation of the nonlinear system for time histories. It can play the role of linear analysis verification. It seems that linearized methods are well suited to obtain extensive insight, respecting limitations of these methods. Numerical simulation, on the other hand, is a valuable tool for pointing out specific effects of a nonlinear system in large amplitude regions.

---