What happened
During the landing rollout phase of flight, the left main landing gear collapsed. Following the collapse, the aircraft skidded to a stop.
The investigation
An examination of the landing gear identified that the barrel lugs, which are used to attach the swinging lever to the main landing gear barrel, had failed. Specifically, the fracture on the outboard lower lug showed clam shell marks, which are characteristic of a fatigue crack. This fatigue crack originated from a corrosion pit located in the bore of the lug.
Further inspection of the four bushings for the lower lugs of the barrel—which had been replaced during a previous overhaul—revealed that they did not have the proper interference fit. Additionally, the bushings lacked the correct application of corrosion preventative on their surfaces. The investigation also found that primer paint was not applied during the overhaul process; instead, Mastinox was used rather than the wet primer required by the manufacturer's procedures.
As part of the investigation, nine different landing gears with varying numbers of total cycles since manufacture or overhaul were inspected. These inspections uncovered several issues, including corrosion on the lug faces and in the lug bores, as well as torn or missing rubber sealant on the bushing flanges.