Dynamics of the Aircraft Nose Landing Gear with Two Time Delays

A four--degree--of--freedom nose landing gear (NLG) system is investigated, which has two time delays in the torsional and lateral bending damping of the strut. By applying a combination of numerical computations and qualitative theory of delay differential equations, the local stability of the trivial equilibrium is analyzed with three different time delay cases. It is further shown that the NLG system undergoes stability switches as the time delays vary, and these stability switches correspond to Hopf bifurcation points at critical time delays. Additionally, numerical results indicate that the NLG system exhibits various irregular motion transitions as the time delays increase, including periodic, multiperiodic, and even chaotic motions. These results highlight the profound impact of time delays on the shimmy amplitude, which leads to a detrimental effect on the stability of the NLG system. The analytical findings provide a theoretical insight into the stability design of NLG systems in the field of engineering applications.