Cessna 182P N8443M accident near Prospect, Tennessee

Probable cause

A loss of engine power due to the fatigue failure of the No. 6 cylinder exhaust valve rocker boss.

NTSB analysis

The pilot was performing a cross-country flight whenthere was a “sudden severe engine vibration and loss of power.” He reduced the throttle in an attempt to lessen the engine vibration and elected to land the airplane in a soybean field since he was unsure if he could clear a large, forested area between him and the next closest airport. After touchdown, the nose landing gear struck a ditch, separated, and the airplane nosed over, coming to rest inverted.

An examination of the engine after the accident revealed the No. 6 cylinder exhaust valve rocker boss was fractured and loose inside the rocker cover. The boss was fractured in two places. Metallurgical examination revealed one of the fractured bosses failed from fatigue that initiated at multiple sites along the bore surface that had been in contact with the rocker arm.

A review of the maintenance logbooks revealed that the engine cylinders were removed, overhauled, and reinstalled about 3 years and 4 months before the accident, and the airplane had accrued about 154 hours total time since the cylinders were overhauled.

Text from the NTSB. Open the NTSB docket for ERA23LA372 for the full record.