What happened
Upon touchdown, the crew of a Boeing 727 felt the aircraft lurch to the right. A subsequent inspection determined that the outer cylinder trunnion of the right main landing gear had sheared at the main landing gear beam trunnion support.
The investigation
The operator reported that two similar incidents had occurred previously. The failed trunnion from this event, along with the components from the two prior occurrences, were sent to Boeing for a detailed metallurgical analysis.
The laboratory report indicated that all three trunnions failed due to fatigue fracture and stress corrosion. This failure initiated in the blendout transition radius located between the cylinder and the machined down trunnion journal. Investigators found that the radius was below the specified minimum requirement. Additionally, the nickel plating extended into this area beyond the length permitted by the overhaul manual. Severe through-thickness cracking in the chrome plating was also identified in all three examined trunnions. The operator noted that all landing gear overhaul rework for the Boeing 727 is performed in-house.