Cessna 172F N211FC accident near Newark, Illinois

Probable cause

The failure of the No. 4 cylinder exhaust valve, which resulted in a partial loss of engine power and a forced landing. Contributing to the valve failure and loss of engine power was the extended time since the last overhaul.

NTSB analysis

The private pilot was conducting a cross-country flight when the airplane had a partial loss of engine power during cruise flight. The pilot stated that the engine continued to run but that there was an excessive vibration and significant loss of power. The pilot's corrective actions did not restore normal engine operation, and he made a forced landing in a nearby field. The airplane's nose landing gear collapsed when it impacted a berm during the landing roll, and the airplane came to rest in a nose-down attitude with structural damage to the lower fuselage.

A postaccident engine examination revealed a failure of the No. 4 cylinder exhaust valve. About 1/2 of the No. 4 exhaust valve was located during the examination, and the recovered portions exhibited significant impact damage. The failure of the No. 4 cylinder exhaust valve would have resulted in a significant loss of engine power during the flight. The engine had accumulated 2,146.9 hours since its last major overhaul, which was completed more than 27 years before the accident. According to available maintenance documentation, the No. 4 cylinder exhaust valve had not been repaired or replaced since the last major overhaul. According to the engine manufacturer, the recommended time between overhaul (TBO) is every 1,800 hours or 12 years, whichever occurs first; however, the operator was not required to comply with the recommended TBO interval under current regulations due to the type of operation.

Text from the NTSB. Open the NTSB docket for CEN16LA297 for the full record.