Event Description
While in cruise flight, the engine RPM decreased unexpectedly. The pilot's attempts to recover the RPM were unsuccessful, and the engine eventually quit. A forced landing was made to an empty field. During the roll-out, the aircraft struck a concealed ditch, which resulted in substantial damage.
Engine Examination
Later examination of the engine revealed that the #3 exhaust valve had seized in a partially open position, and the corresponding pushrod was broken. There was evidence that the valve had not been seated for some time, with carbon buildup found on both the valve and valve seat.