Failure Investigation: in Flight Loss of a Main Landing Gear Door of a Transport Aircraft

Abstract: An executive transport military aircraft experienced the loss of the left main landing gear door during a standard flight. In the aftermath of this serious occurrence, at the Chemistry Department of the Flight Test Center of the Italian Air Force (IAF), a technical investigation started to identify the root causes of the failure and to prevent other similar incidents. The investigation was carried out jointly with the representative of the manufacturing company and was focused on the fracture surfaces of the hinges connecting the door to the fuselage. This paper shows the results obtained by fractographic (optical and electronic microscopy), metallographic, chemical analysis and numerical simulation: the root cause of the cracks was a phenomenon of pitting corrosion mainly located on the door back hinge and due to a local loss of coating. This made possible a fatigue fracture mechanism under normal operative cyclic loads.