What happened
During the landing roll of an aircraft, the left main gear outer cylinder separated from the assembly.
The investigation
A metallurgical examination was conducted on the failed component. Investigators discovered a pre-existing fatigue crack located in the Schrader valve hole. This area, including the region where the fatigue occurred, had been coated with a layer of nickel during a previous overhaul to restore the part's original tolerances.
The investigation determined that the cracking originated from a 0.009-inch-deep gouge or filing mark within this nickel layer. Due to the presence of this mark and other similar nearby marks, the corner of the component failed to meet the required overhaul specifications, which mandate a radius of 0.6 to 0.9 inches at the fatigue initiation site. Additionally, a bevel found in the nickel layer at this corner did not comply with established corner requirements.
The cylinder involved had accumulated 82,131 total hours and 14,951 cycles. It had last been overhauled and returned to service on September 30, 1988.