Failure analysis on abnormal cracking of the main landing gear door of a civil aircraft

Among the myriad structural and moving components integral to civil aircraft, only a select few confront the dual challenges of meeting aerodynamic and mechanical performance criteria, a circumstance exemplified by landing gear doors. The failure of landing gear poses a substantial threat to both the structural integrity and the safety of an aircraft during flight. Surprisingly, the existing literature lacks an in-depth investigation into the failure of landing gear doors. This paper addresses this gap by examining the abnormal cracking failure observed in the main landing gear door of a civil aircraft. The purpose of this paper is to find out the root cause of the failure, so a comprehensive investigation of the landing gear outer door is carried out. This investigation employed various techniques, including computed tomography, three-dimensional scanning analysis, macroscopic and microscopic morphology analysis using optical microscopy, threedimensional stereomicroscopy, scanning electron microscopy, and micro-area composition analysis using energy dispersive spectrometry. Through repeated sorting and comprehensive analysis of various failure forms and defects, the root causes of the main landing gear door failure were conclusively identified. Evidence revealed that the crack originated at the upper edge corner of the main landing gear door, precisely where abnormal contact and wear with the hinge joint occurred. Targeted countermeasures were proposed from aspects such as design, manufacturing, and installation, and the suggested improvements were adopted.