On May 24, 1989, a Boeing 727-247 (registration N296WA) operated by Delta Air Lines was involved in an aviation accident near Denver, CO. Investigators recorded the probable cause as: FAILURE OF THE LEFT MAIN LANDING GEAR FORWARD TRUNNION BEARING SUPPORT FITTING DUE TO A CRACK INITIATING AT THE FORWARD EDGE OF THE BORE AND PROPAGATING BY INTERGRANULAR STRESS CORROSION INTO THE BORE SURFACE THAT RESULTED IN AN EVENTUAL DUCTILE FRACTURE. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive; 13 related events involving the same aircraft type or operator are linked below.
During pushback, the left main landing gear collapsed. Inspection revealed a fractured forward trunnion bearing support fitting with heavy surface corrosion and intergranular stress corrosion cracking.
Event Description
During the pushback procedure, the aircraft was pulled forward slightly to remove the nosewheel from the chocks. At that moment, the left main landing gear collapsed.
Inspection Findings
Subsequent inspection of the landing gear assembly revealed a fracture of the forward trunnion bearing support fitting (part number 65-16206-11). Heavy surface corrosion was observed on the fitting. Microscopic examination disclosed extensive intergranular stress corrosion. A crack had developed approximately 0.1 inches inboard from the forward edge of the bore and had propagated approximately 2.1 inches aft into the bore surface. The final fracture resulted from ductile separation.
