The effects of runway unevenness on the design and operation of an aircraft have been subjected to investigations for a number of years. Runway roughness will, in general, produce both longitudinal and lateral excitations. This article examines the lateral stability of linear and non-linear models of an aircraft nose landing gear (NLG) subjected to ground-induced lateral excitation. Simulations of ground profile and ground excitation modelling have been performed and numerical studies were carried out to bring out the effect of runway roughness and its interaction with torsional free play. The results show that a small amount of runway excitation causes a significant reduction in the critical shimmy velocity and, in combination with free play, it has an adverse impact on lateral stability of the NLG of an aircraft. Finally, a study has been performed to postpone the dynamic instability by introducing a magnetorheological (MR) fluid-based damper and enhanced torque arm stiffness.
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