Incident Details
The pilot reported that the engine began running roughly and vibrating during flight. In response, he turned the ignition key to "OFF" and performed a forced landing to a field. The landing occurred on a rough surface, resulting in substantial damage to the fuselage.
Engine Inspection
Post-incident inspection of the engine found that the number one cylinder connecting rod had failed. The rod exhibited signatures consistent with overheating. Additionally, the number one cylinder connecting rod bearing was extruded, with pieces discovered in the oil screen. The bearing also showed overheating signatures.
Approximately 2 quarts of oil were present in the engine sump, with no evidence of external oil leakage. The pilot reported that the oil level during the preflight inspection was over 4 quarts.