What happened
Following touchdown, the aircraft rolled approximately 400 to 600 feet along the runway when the left main landing gear collapsed. This structural failure caused the aircraft to veer off the left side of the runway.
The investigation
An investigation into the collapse revealed that the left main landing gear trunnion had failed due to fatigue. The fracture occurred through the barrel adjacent to the lower end of the fillet. A metallurgical examination determined that the fatigue originated at the base of a grinding mark. Additionally, investigators identified several secondary cracks that also originated from grinding marks located near the primary fatigue fracture.
According to the aircraft logbook, the trunnion had undergone inspection during the previous 100-hour inspection in accordance with Piper Service Bulletin (S/B) #787A. At the time of the accident, the aircraft had flown approximately 80 hours since that inspection. The requirements of the service bulletin specified cleaning the trunnion housing of dirt and paint and performing a careful inspection of the housing for cracks using 10x magnification at the lower end of the fillet.