Incident Overview
During cruise at 5500 feet, the pilot detected the odor of burning oil. Shortly thereafter, oil pressure was lost, the propeller entered high RPM, and the tachometer indicated overspeed beyond the redline. A loud report was heard, and all engine power ceased. The pilot attempted a forced landing in rolling countryside, but the aircraft struck a tree and a fence during the landing.
Engine Examination
Post-accident examination of the engine found that the No. 6 connecting rod cap had failed. This failure was followed by a progressive and massive internal destruction of the engine. The root cause of the engine failure was determined to be oil starvation.
Oil Supply Hose
Further investigation revealed that the oil starvation resulted from a broken oil supply hose that runs from the oil cooler to the accessory drive section of the engine. The hose was 12 years old and had accumulated 802 hours of service since its installation in 1978. The manufacturer's recommended replacement interval for the hose is 1000 hours. The hose is covered by a fire insulation sleeve, which prevents easy visual inspection without disconnecting the hose, removing it from the aircraft, and withdrawing it from the sleeve.