CEN18LA329

The student pilot reported that he was flying north of the departure airport when the airplane's engine began running roughly. He attempted to return to the airport but was unable to reach the airport and landed in a cornfield. The airplane nosed over in the 7-ft-tall corn and sustained substantial damage to both wings. Examination of the airplane revealed that the engine's No. 3 cylinder exhaust valve was stuck in its valve guide, and the No. 3 exhaust valve rocker arm was fractured. A maintenance record entry indicated that the Nos. 1, 3, and 4 cylinders had experienced valves sticking and had been sent back to the overhaul vendor for service. The cylinders were reinstalled 3 days before the accident. Based on the available evidence, the partial loss of engine power was likely due to the No. 3 cylinder exhaust valve becoming stuck, which resulted in a secondary overload failure of the associated rocker arm and a substantial reduction in engine power output.

On August 14, 2018, about 0800 central daylight time, a Cessna 150M, N6341K, sustained substantial damage during a landing to a corn field near Madison, South Dakota, following a loss of engine power during cruise flight. The student pilot was not injured. The aircraft was registered to an individual and operated by the pilot under the provisions of 14 Code of Federal Regulations Part 91 as a solo instructional flight. Visual meteorological conditions prevailed for the flight, which was not operated on a flight plan. The local flight originated from the Madison Municipal Airport (MDS), Madison, South Dakota, about 0710. The student pilot reported he was flying north of MDS when the airplane's engine began running rough. He attempted to return to MDS but was unable to reach the airport and landed in a corn field. The airplane nosed over during the forced landing and sustained substantial damage to both wings. The airplane came to rest inverted in corn standing about 7 ft tall. Due to the location of the airplane in the middle of the corn field, the airplane was not recovered until 6 weeks after the accident after the crop had been harvested. Examination revealed that the engine's No. 3 cylinder exhaust valve was stuck in its valve guide and the No. 3 exhaust valve rocker arm was fractured. Maintenance records showed that the airplane engine's most recent overhaul was completed on March 12, 2018. The most recent engine maintenance record entry dated August 11, 2018, indicated that the Nos. 1, 3, and 4 cylinders had been removed and sent back to the vendor that had completed the engine overhaul due to sticking valves. The cylinders were then reinstalled on the engine. According to the tachometer times noted in the maintenance entries, the engine had accumulated 207 hours since the overhaul as of the maintenance entry.