Failure Analysis And Improved Scheme Of A Type Of Nose Landing Gear Emergency Lowering

The landing gear retraction-extend mechanism is the key components of aircraft, whose workingperformance directly affects the security of takeoff-landing and ground motion. Among all the aircraftaccidents, the aircraft accident caused by the landing gear mechanism malfunction is highest. Therefore,the search of landing gear mechanism is of great significance. This paper is based on the nose landinggear of an aircraft. The failure cause of the emergency lowering was obtained. The improved schemewas then put forward. The scheme solved the problems of the test element’s deformation and themechanism’s clamping stagnation, which provided a meaningful reference for the fault analysis oflanding gear emergency lowering.For the problem that a nose landing gear failed to extend in the emergency way, the kinematicalanalysis and dynamic analysis of the model were carried out. According to the reasons why the failureoccurred, the improving scheme of the landing gear was given. The three-dimensional improved modelwas built in CATIA, and the kinematical performance of the mechanism was simulated in the DMUmodule. The dynamic performance was also obtained by analyzing the model in LMS Virtual.Lab.These analyses verified the feasibility of the improved scheme, and provided a basis for the landinggear’s further structural design and strength optimization.During the tests of a landing gear, the retraction mechanism got stuck due to the seriousmechanism deformation. Aiming at this problem, the mechanism’s load condition was analyzed and thefailure causes were obtained. The rigid-flexible coupling models were established using ADAMS aswell as LMS Virtual.Lab. By the rigid-flexible coupling dynamics simulation method, it wasconcluded that how the assembling gap affects the mechanism deformation. The study shows that themain reason why the mechanism got stuck is the additional moment caused by the origin design and theassembling gap. The improved design scheme was proposed and analyzed by the rigid-flexiblecoupling method. The following results were concluded. The new scheme can solve the unreasonablestress problem on the transmission parts. The key components’ deformation has also been reduced,which solves the clamping stagnation problem,ensure the flight test of this landing gear.