Cessna 172N N738LF accident near Desert Center, California

Probable cause

A partial loss of engine power due to low compression from an obstructed intake valve. Contributing to the accident was the pilot’s decision to shut down the engine while in flight.

NTSB analysis

In cruise flight, the airplane experienced a loss of power to the avionics. While focusing on that situation, the pilot reported a partial loss of engine power and the inability of the airplane to maintain altitude. The pilot elected to make a precautionary landing at a nearby airport. Believing he was in gliding distance of the airport, he shut down the engine. The approach was too high and the airplane overshot the runway. The pilot attempted a turn back to the runway; however, he had to make a sharper-than-normal turn due to wires in his immediate flight path. While performing the tighter turn, the airplane lost further altitude and the pilot had to make a forced landing adjacent to the runway on uneven terrain, coming to rest inverted. During a postaccident examination of the engine it was discovered that the number one cylinder's intake valve had deposits on the valve seat, preventing it from making a tight seal and resulting in the partial loss of engine power. No electrical problems could be identified during the examination.

Text from the NTSB. Open the NTSB docket for WPR09LA245 for the full record.