CEN22LA309

The pilot stated that he noticed a slight hesitation in the engine, followed by backfiring and a large drop in engine speed while in cruise flight at 2,000 ft above ground level. He was able to regain partial power for a few minutes before the engine lost additional power. The pilot performed a forced landing between two corn fields, where the airplane sustained substantial damage to the fuselage due to impact with terrain. Postaccident testing of the engine revealed a stuck exhaust valve on the No. 2 cylinder that resulted in the loss of engine power during cruise flight. No other anomalies were noted with the engine or related systems that would have precluded normal operations of the engine. Thus, the stuck exhaust valve likely resulted in the partial loss of engine power.

On July 7, 2022, at 1915 central daylight time, a Cessna 172M, N5177H, sustained substantial damage when it was involved in an accident near Friend, Nebraska. The pilot and a passenger were uninjured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. The pilot stated that the engine sustained a slight hesitation followed by backfiring and a large drop in engine speed during cruise flight at 2,000 ft above ground level. The pilot reported he switched fuel tanks, checked carburetor heat, switched magnetos, and was able to restore partial power for a few minutes by adjusting the throttle. The engine then "lost all power again." Attempts to restore power with throttle control movement were unsuccessful. The engine then lost additional power and the pilot performed a forced landing between two corn fields. The airplane’s right wing impacted corn stalks and spun the airplane around during the landing. The airplane sustained substantial damage to the fuselage. During a postaccident engine run, the engine missed and an external temperature measurement of the No. 2 cylinder assembly revealed a relatively colder temperature than that of the other cylinder assemblies. The pilot attributed the engine missing and low cylinder assembly temperature to a sticking exhaust valve. No other anomalies were noted with the engine that would have precluded normal operations.