Abstract:The landing gear system (LGS) is an important component of aircraft which supports the aircraft and has a characteristic of control, including the aerodynamics, control, hydraulic and others. It has a very important mission, which seriously influences the safety of an aircraft, especially during the process of landing and taking off. LGS extension/retraction system of a typical civil aircraft is taken as a research object. Its dynamic behavior was analyzed by using LMS Virtual, Lab Motion and LMS Imagine. LGS extension/retraction system was dynamically simulated by Lab AMESim software. The influence of equivalent force was studied on LGS extension/retraction system, as well as for the characteristic of LGSs dynamic movement and friction. The result shows that the LGS model can complete the action of extension and retraction on time under the condition of equivalent force, which has an obvious influence on the speed of LGSs retraction and extension.