What happened
On October 18, 2022, a Piper PA-3/2-300, registration N600JG, was involved in a fatal accident near Brentwood, Tennessee. The flight was being operated under Part 91 for the purpose of delivering the aircraft to Fayetteville Municipal Airport (YFM) for avionics repairs.
While cruising at approximately 5,400 feet, the pilot declared an emergency due to a partial loss of engine power. After communicating with air traffic control, the pilot attempted to divert to Nashville International Airport (BNA). During the descent, the pilot reported that the engine had "stopped" and the aircraft was "heading down."
An eyewitness observed the aircraft maneuvering approximately 75 feet above the ground before striking power lines and crossing a road. The aircraft came to rest in trees, where it caught fire and eventually exploded. The pilot sustained 1 fatal injury.
The investigation
Investigators examined the engine and wreckage to determine the cause of the power loss. The engine, a Lycoming IO-540-K1A5, could not be rotated by hand, and the oil suction screen was found to be completely blocked with metallic particles and rubber material consistent with a magneto drive cushion.
Technical analysis of the crankshaft revealed a fatigue crack that began in the fillet radius between the No. 6 connecting rod journal and the forward cheek. The No. 6 rod bearing had been extruded, and the No. 6 connecting rod was fractured. Evidence of sliding contact damage was found on several connecting rod journals and caps.
Maintenance records showed the engine had undergone a field overhaul in 2012, during which the crankshaft was replaced. Investigators found that the installed crankshaft had been made obsolete in 1979 and was not certified for use in this specific engine model. Furthermore, the crankshaft had been renitrided during the 2012 overhaul, but the resulting nitride layer was thicker than specification and the core hardness was lower than required. Additionally, the connecting rod bearings used in the engine were not authorized for this specific engine model.