DEN06LA112

While in cruise flight at an altitude of approximately 8,500 feet, the pilot heard a "loud bang," and the engine oil pressure decreased. Shortly thereafter, engine oil was noted on the windscreen, and the engine lost power. Subsequently, the pilot initiated a forced landing to a field. During the forced landing, the airplane impacted terrain and the nose and right main landing gears collapsed. Examination of the airplane revealed the right wing was buckled. A review of the maintenance records revealed that 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 major overhaul and 49 hours since the annual inspection. No additional maintenance besides an oil change was performed on the engine since the November 11th inspection. Examination and disassembly of the engine revealed that connecting rods had been fractured and separated. The pistons were found separated from the connecting rods. The six pistons displayed cracks and fractures along the piston pin bosses, and mechanical damage was noted on the bottom side of the piston. The pistons were retained for further examination by the NTSB materials laboratory. The connecting rod and main bearings displayed evidence of discoloration and heat signatures. The crankshaft counterweights were separated from the crankshaft. Metallurgical examination of two pistons revealed that fractures along the boss for the piston pin were consistent with overstress separation in a casting.

On August 10, 2006, approximately 0830 mountain daylight time, a Piper PA-24-260, single-engine airplane, N8741P, sustained substantial damage during a forced landing following a loss of engine power during cruise flight near Harrisburg, Nebraska. The private pilot, who was the registered owner and operator of the airplane, and passenger were not injured. Visual meteorological conditions prevailed, and a flight plan was not filed for the Title 14 Code of Federal Regulations Part 91 personal flight. The flight departed Garden City, Kansas, at 0700 central daylight time, and was destined for Billings, Montana.

According to the pilot, while in cruise flight at an altitude of approximately 8,500 feet, he heard a "loud bang," and the engine oil pressure decreased. Shortly thereafter, engine oil was noted on the windscreen, and the engine lost power. Subsequently, the pilot initiated a forced landing to a field. During the forced landing, the airplane impacted terrain and the nose and right main landing gears collapsed. Examination of the airplane by the pilot revealed the nose and right main landing gears were separated, and the right wing was buckled.

A review of the maintenance records revealed that 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 major overhaul and 49 hours since the annual inspection. No additional maintenance besides an oil change was performed on the engine since the November 11th inspection.

The Lycoming IO-540-D4A5 engine was examined and disassembled at the facilities of Crotts Aircraft Service, Dodge City, Kansas, under the supervision of a Federal Aviation Administration inspector. Examination and disassembly of the engine revealed that connecting rods had been fractured and separated. The pistons were found separated from the connecting rods. The six pistons displayed cracks and fractures along the piston pin bosses, and mechanical damage was noted on the bottom side of the piston. The pistons were retained for further examination by the NTSB materials laboratory. The connecting rod and main bearings displayed evidence of discoloration and heat signatures. The crankshaft counterweights were separated from the crankshaft.

According to the NTSB materials laboratory factual report, dated March 27, 2007, two AirTech pistons contained a crack in the boss for the piston pin. Saw cuts were performed in order to expose the fracture surfaces. The exposed fracture face from each piston contained a river pattern, indicative of a fracture origin, that emanated at the machined chamfer on the end of the piston pin bore. Scanning electron microscope examination of the fracture faces revealed faceted features consistent with overstress separation in a casting. No evidence of fatigue cracking was noted. X-ray energy dispersive spectroscopy analysis of the fracture faces produced a spectrum consistent with an aluminum alloy.

The reason for the engine failure could not be determined.