Cessna 150M N171RD accident near Key Biscayne, Florida

Probable cause

The fatigue failure of the No. 1 cylinder intake valve, which resulted in the partial loss of engine power.

NTSB analysis

The commercial pilot was conducting a personal flight. The pilot reported that, several minutes after takeoff and while en route to his destination airport, the engine began to run roughly and lose power. He subsequently attempted to restore power without success. He then maneuvered the airplane for a forced landing on the fairway of a golf course. The airplane touched down on wet grass, and the pilot was unable to stop the airplane before it collided with two palm trees, which separated the outboard sections of both wings.

Postaccident examination of the engine revealed that the intake valve of the No. 1 cylinder had failed due to fatigue, which would have resulted in the partial loss of engine power and engine roughness reported by the pilot. The origin and the extent of the fatigue region could not be determined due to postfracture damage. Further examination of the tip of the valve revealed an abnormal contact wear pattern likely caused by either misalignment relative to the valve seat, valve guide wear, or sticking between the valve stem and the valve guide. A review of maintenance records revealed that new cylinders had been installed when the engine was overhauled about 904 total flight hours before the accident.

Text from the NTSB. Open the NTSB docket for ERA16LA027 for the full record.