This August 2007 accident report is provided by the National Transportation Safety Board. Published as an educational tool, it is intended to help pilots learn from the misfortunes of others.
Aircraft: Cessna 172.
Location: Goleta, Calif.
Injuries: 1 Minor, 1 Uninjured.
Aircraft damage: Substantial.
What reportedly happened: The airplane was 15 miles east of the destination airport, at 1,500 feet msl, when the engine gauges started to indicate low oil pressure and high oil temperatures. About eight miles east of the airport, the engine experienced a loss of power, and produced a puff of white-gray smoke combined with loud clanking sounds. The pilot directed the airplane towards an open field above a stretch of beach.
During the landing roll, the airplane came to the end of the field, nosed over the edge of a 50-foot cliff, and came to rest on the beach below.
The engine had been factory rebuilt in 2002, and had accumulated 1441.5 hours since the last major overhaul. An examination of the engine revealed a 2.7-inch hole in the top of the engine case, shiny copper fragments from the number two main bearing in the oil sump, and one bearing fragment in the oil pickup screen. Additionally, the bearing material of the number two main bearing had partially displaced itself and extruded between the crankshaft journal and the crankcase. Numerous fragments from the main bearing were located in the oil sump. The sizes of the fragments were generally too large to enter the oil sump pickup tube but could obstruct the pickup tube orifice, restricting the oil flow. Engine oil analysis records indicate a sudden increased level of copper occurred sometime within the previous 63.1 hours of operation. Engine journal bearing material is the only material within the engine that has a significant copper component. This increase in copper levels is directly related to the gradual deformation and fragmentation of the number 2 main bearing. The number one connecting rod had failed under overload that resulted from extreme temperatures at the connecting rod bearing that were consistent with oil starvation.
Probable cause: The oil starvation and failure of the number one piston connecting rod and bearing that was due to the fragmentation of the number two main bearing, which then obstructed the engine oil pickup tube and restricted the flow of oil through the engine.
For more information: NTSB.gov