Incident Summary
While cruising at 8,500 feet, a passenger in the right seat observed that the oil filler access door on the top of the right engine was open and that oil was leaking from it. The pilot then checked the engine instruments and noted that the only abnormal reading was a low manifold pressure on the left engine. In response, the pilot decided to perform a precautionary landing at Clinton.
Approach and Landing
During the traffic pattern, the pilot heard the left engine cutting out. Recalling the earlier low manifold pressure reading, he believed the left engine was failing and feathered the left propeller. He also retracted the landing gear and flaps. However, the right engine did not produce sufficient power, and the aircraft crash landed in a wheat field.
Post-Accident Examination
Examination of the right engine revealed a fatigue failure of the No. 4 cylinder. The fatigue crack had initiated at pre-existing sharp-bottomed dents present in two cracked fins, with the crack propagating from the fins into the cylinder. The left engine was subsequently run and tested; the only deficiency noted was that the engine ran richer than normal at low power settings.