Incident Details
The aircraft was kept in an unheated hangar and fitted with an oil heater. Outside temperature at takeoff was approximately 0°F. During departure, oil pressure registered in the yellow arc and remained there for the duration of the flight. Despite available airports suitable for precautionary landings, the pilot continued the flight.
After about 30 to 45 minutes of flight, the propeller began surging and oil pressure decreased markedly. Approximately one minute later, the engine started knocking and subsequently stopped. The pilot executed a forced landing.
Post-Accident Inspection
Following the accident, oil was observed covering the top of the engine. The oil cap was found securely tightened. Approximately 4 quarts of oil remained in the engine as indicated by the dipstick. Engine inspection revealed a hole in the crankcase above the number 2 and 4 cylinders. The connecting rod bearings for cylinders 2, 3, and 5 were burned and showed signs of meltdown. The number 4 connecting rod and bearing had separated from the crankshaft and exhibited heat damage and failure. Examination of the oil passages found no obstructions, and fluid flowed freely through the oil cooler.