The private pilot was conducting a personal, cross-country flight. He reported that, when the Cessna 152 was about 12 miles from the departure airport, the engine started running roughly, and the airplane was “violently shaking.”
He decided to conduct a forced landing in a field near St. Augustine, Florida. During the landing, the nose landing gear dug into the soft ground and the airplane flipped over.
Post-accident examination of the engine revealed that the No. 4 cylinder exhaust valve was fractured, and although the head of the exhaust valve was not recovered, the fracture features on the exhaust valve stem were consistent with fatigue.
A review of maintenance records revealed that the exhaust valves were installed during an overhaul of the engine about 28 years before the accident. The engine manufacturer recommended that the engine be overhauled every 12 years or 2,400 hours, whichever comes first.
Probable cause: The partial loss of engine power due to a fractured exhaust valve, which resulted in a forced landing on unsuitable terrain and a subsequent rollover.
This September 2018 accident report is provided by the National Transportation Safety Board. Published as an educational tool, it is intended to help pilots learn from the misfortunes of others.