Incident Overview
While cruising at approximately 8,500 feet, the pilot reported hearing a loud bang, followed by a decrease in engine oil pressure. Shortly thereafter, engine oil was observed on the windscreen, and the engine lost power. The pilot executed a forced landing to a field. During the landing, the airplane impacted terrain, causing the nose and right main landing gears to collapse. Post-accident examination revealed that the right wing was buckled.
Maintenance History
A review of maintenance records showed that the most recent annual inspection was completed on November 11, 2005, at a total airframe time of 3,358 hours. The engine had accumulated 257 hours since its last major overhaul and 49 hours since the annual inspection. No additional maintenance beyond an oil change had been performed on the engine following the November 11 inspection.
Engine Examination
Disassembly and examination of the engine revealed that the connecting rods had fractured and separated. Pistons were found separated from the connecting rods. All six pistons exhibited cracks and fractures along the piston pin bosses, with mechanical damage noted on the underside of the pistons. The pistons were retained for further examination by the NTSB materials laboratory. The connecting rod and main bearings showed evidence of discoloration and heat signatures. Additionally, the crankshaft counterweights had separated from the crankshaft. Metallurgical examination of two pistons determined that fractures along the boss for the piston pin were consistent with overstress separation in a casting.