Incident Overview
The airplane conducted a forced landing in an open field following a complete loss of engine power during climb out from a touch-and-go landing. The pilot had been practicing touch-and-go landings for over an hour with no prior difficulties. After a brief break, he performed another preflight inspection and resumed landing practice.
Sequence of Events
On the fourth takeoff, as the aircraft climbed through approximately 200 feet, the engine emitted a clunking noise and ceased producing power. The pilot steered the airplane toward an open field and touched down on soft dirt. However, the terrain caused the aircraft to dig in, resulting in damage to the wings, stabilizer, landing gear, and propeller.
Engine History
The engine had accumulated an estimated 1,860 hours since its manufacture in 1953. According to the manufacturer, there was no record of the engine having been returned to the factory after its original production. The engine underwent a field overhaul in 1960, accumulating approximately 910 hours since that time. A subsequent "top overhaul" in 1970, during which the exhaust valves were replaced, left the engine with about 255 hours of operation.
Post-Accident Inspection
Examination of the engine revealed that all cylinders were undamaged except for cylinder No. 3, which exhibited extensive mechanical damage. The exhaust valve for cylinder No. 3 had fractured and separated at the transition where the valve stem meets the valve head. The fracture surfaces on the separated valve pieces were completely obliterated by the mechanical damage sustained during the failure. The piston face showed mechanical damage across most of its surface, including two holes. The push rod corresponding to cylinder No. 3 was slightly bent. However, no evidence was found indicating that the valve had been sticking prior to failure.