WPR19LA226

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 go around 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.

On July 26, 2019, about 1920 Pacific daylight time, a Cessna 177RG airplane, N1828Q, was substantially damaged when it was involved in an accident near Fall City, Washington. The pilot and passenger sustained minor injuries. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. According to the pilot, as he neared his level off altitude, the airplane’s engine began to run rough after, and he 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, Fall City Airport (1WA6), Fall City, Washington. The pilot stated that he had difficulty locating the airport while on a straight-in approach. Subsequently, he misjudged the airplane’s altitude and speed for the landing and initiated a go-around. During the go-around, the engine lost additional power, which resulted in the pilot initiating a forced landing in an open field. Due to the field’s uneven terrain, the airplane nosed over during the landing roll and came to rest inverted. A postaccident examination of the engine revealed that the engine could be safety run. An engine test run was accomplished, and the engine ran rough at various power settings. After the engine run, it was noted that the No. 3 cylinder was cold to the touch, which was consistent with it being non-operational. The No. 3 cylinder was then removed from the engine for examination. Examination of the cylinder combustion area revealed that the No. 3 intake valve head had a cup shape conforming to a “tuliped” valve, consistent with exposure to excessive temperatures. The softening of the valve head material caused by excessive temperatures would deform the valve head into a “tulip” shape. The “tulip” shape of the valve head did not allow the intake valve to seat properly and left a noticeable gap through which gases and air could escape.