Cessna 172M N61736 accident near Oakland, California

Probable cause

A loss of engine power due to oil starvation. The oil starvation event was due to the failure of maintenance personnel to tighten the mounting bolts for the newly installed vacuum pump.

NTSB analysis

During cruise flight, the pilot noticed the engine was running rough along with a surge in power. He adjusted the mixture to the full rich position, which seemed to smooth the roughness. A few seconds later, he noticed that the engine oil temperature gauge was rising and he diverted towards a nearby airport. The pilot stated that while en route to the airport, the engine lost power and he initiated a forced landing to an open lot near his position. During the landing roll, the airplane struck a large mound of dirt. Examination of the airplane revealed structural damage to the fuselage. Only residual oil was found in the engine. Examination of the engine revealed evidence of an internal oil starvation induced catastrophic failure. The nuts securing the vacuum pump to the mounting pad were loose. About 10 psi of compressed air was applied to the oil cooler inlet port on the engine. Bubbling oil was observed originating from the vacuum pump mounting pad. No further anomalies were noted. Review of maintenance records revealed that the vacuum pump was replaced prior to the accident flight.

Text from the NTSB. Open the NTSB docket for SEA08LA155 for the full record.