Cessna 177RG N1828Q accident near Fall City, Washington

Probable cause

The failure of the No. 3 cylinder intake valve that resulted in a partial loss of engine power and a forced landing on uneven terrain.

NTSB analysis

During a cross-country flight, as the pilot neared his level-off altitude, the airplane’s engine began to run rough. The pilot elected to return to the departure airport. However, during the return, the engine continued to run rough and lose power, which prompted him to land at the nearest airport. He had difficulty locating the airport during the approach, which resulted in the airplane being high in altitude and airspeed. The pilot initiated a go-around, but, during the goaround the engine lost additional power. The pilot initiated a forced landing to an open field. The airplane nosed over during the landing roll due to uneven terrain and came to rest inverted.

A postaccident examination of the engine and an engine run revealed that the No. 3 cylinder was non-operational. Examination revealed that the No. 3 intake valve head was deformed, likely from exposure to excessive temperatures, which resulted in the softening of the valve material. The deformity of the valve did not allow the intake valve to seat properly and left a noticeable gap through which gases and air could escape. This gap would result in the loss of power from the No. 3 cylinder. The reason for the overheat condition could not be determined based on available evidence.

Text from the NTSB. Open the NTSB docket for WPR19LA226 for the full record.