What happened
The pilot was engaged in practicing touch-and-go landings for over an hour and had encountered no issues with the aircraft during that period. Following a break, the pilot performed another preflight inspection and continued with further landing practice.
During the fourth takeoff of the session, as the airplane climbed through 200 feet, the engine produced a clunking noise and ceased producing power. The pilot steered the aircraft toward an open field and performed a forced landing on soft dirt. Upon impact, the airplane dug into the ground, causing damage to the wings, stabilizer, landing gear, and propeller.
The investigation
Investigators examined the engine, which had been in service for approximately 1,860 hours since its manufacture in 1953. There was no factory record of the engine returning for service since that time. The engine had logged about 910 hours since a field overhaul in 1960 and roughly 255 hours since a top overhaul performed in 1970, which included the replacement of the exhaust valves.
Upon inspection, all cylinders were found to be undamaged except for cylinder No. 3, which showed extensive mechanical damage. The exhaust valve for cylinder No. 3 had fractured and separated at the transition point between the valve stem and the valve head; the fracture surfaces were obliterated by subsequent mechanical damage. Additionally, the piston face exhibited widespread mechanical damage and contained two holes. While the corresponding push rod was slightly bent, investigators found no evidence of a sticking valve.