Event Overview
During flight, the pilot notified air traffic controllers that the aircraft engine was operating roughly and that he was shutting it down. The pilot later reported that the engine began to shake violently, raising concern that the engine might separate from its mount. A forced landing was executed in a farm field.
Aircraft and Engine Information
The aircraft had accumulated a total time of 62.5 hours. The engine, which was new, had logged 42 hours of operation.
Post-Accident Examination
An external examination of the engine revealed three broken engine mounts. No other external evidence of damage was noted. Subsequently, the engine case was disassembled. The engine crankshaft was found to be broken at the connecting rod journal for the number one cylinder.
Metallurgical Analysis
A metallurgical analysis of the fracture surface showed striations typical of fatigue cracking. The fatigue origin was located 0.033 inches below the surface. No metallurgical anomalies were observed in a section made near the fracture origin.