Incident Description
After touchdown, the flight crew felt the aircraft lurch to the right. An inspection found that the right main landing gear outer cylinder trunnion had sheared at the main landing gear beam trunnion support.
Prior Incidents
The operator reported two similar prior incidents involving trunnion failures.
Metallurgical Analysis
The failed trunnion and the two from the prior occurrences were sent to Boeing for detailed metallurgical analysis. According to the lab report, all three trunnions failed as a result of a fatigue fracture and stress corrosion. The fracture initiated in the blendout transition radius between the machined-down trunnion journal and the cylinder.
Findings
The radius was found to be below the specified minimum, and nickel plating extended into the area in excess of the length permitted by the overhaul manual. Additionally, severe through-thickness cracking in the chrome plating was found in all three trunnions.
Operator Information
According to the operator, Boeing 727 landing gear overhaul rework is performed in-house.