Criterion and parameter analysis in aircraft shimmy study

Aircraft shimmy, a dynamic instability phenomenon of the landing gear has been a problem for over half a century. It is important to predict and control nose landing gear shimmy effectively in aircraft design phase. Simulation with typical cases is a better way compared to the tests on real aircraft to investigate early stage design and give modification suggestions at a reasonable cost .In this paper, the simulation for a certain type of aircraft is presented based on actual data. In the rigid-flexible coupling model of aircraft, non-linear factors are considered, such as airframe flexibility, steering clearance and tire parameters. The model is checked with test results of static and modal experiments and proved with sufficient accuracy. Figures of stable region are presented, formed by taxing speed and critical anti-shimmy damping coefficient. Accordingly, details of shimmy criterion are discussed and effects of factors mentioned above are studied. The result shows that self-alignment torque coefficient, relaxation length of tire, and steering clearance of nose landing gear affect critical damping coefficient significantly.