NTSB Identification: LAX07LA236.
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Accident occurred Wednesday, August 01, 2007 in Goleta, CA
Probable Cause Approval Date: 03/31/2008
Aircraft: Cessna R172K, registration: N458BJ
Injuries: 1 Minor,1 Uninjured.
NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.
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 8 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 airplane was at 1,200 feet, and 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 2 main bearing in the oil sump, and one bearing fragment in the oil pickup screen. Additionally, the bearing material of the number 2 main bearing had partially displaced itself and extruded between the crankshaft journal and the crankcase. The bearing fragments were somewhat shiny or polished, indicating they received lubrication and were not exposed to extreme temperature. Numerous fragments from the number 2 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 from 5.3 parts per million (ppm) to 61.2 ppm 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 1 connecting rod had failed under overload that resulted from extreme temperatures at the connecting rod bearing that were consistent with oil starvation. The number 1 connecting rod bearing receives oil pressure from the oil pump through the number 1 main bearing, and would be one of the first bearings to be effected by reduced oil flow.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: The oil starvation and failure of the number one piston connecting rod and bearing that was due to the fragmentation of the number 2 main bearing, which then obstructed the engine oil pickup tube and restricted the flow of oil through the engine. Full narrative available
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