Incident Overview
During cruise flight at an altitude of 6,500 feet, a commercial pilot with 1,150 flight hours observed a rise in engine oil temperature. The pilot responded by opening the cowl flaps and increasing the mixture control, which resulted in a reduction of exhaust gas temperature (EGT) and cylinder head temperature (CHT).
Engine Failure
Approximately five minutes after these adjustments, the engine began "running rough and sparks appeared from the cowling with loud bangs." The pilot subsequently shut down the engine and extended the landing gear in preparation for a forced landing on a road. However, the airplane was unable to reach the road and executed a forced landing at night in a field covered with mesquite. The landing resulted in structural damage to the aircraft.
Post-Incident Examination
An examination of the engine revealed that several connecting rods had failed, and the number one piston was found to be eroded.
Conclusion
The investigation did not assign a probable cause to this event.