19981203045859A

Approximately one hour into the flight, the flight instructor reported that the engine developed a rough condition and a reduction in power. Since normal flight could not be maintained, the flight instructor selected a field that he believed would be suitable for a forced landing. During the landing roll, the flight instructor attempted to avoid a collision with a drainage ditch and trees. After the airplane went through several gyrations it rested 180 degrees from the initial landing direction. Examination of the engine desclosed that the #2 exhaust valve had failed, and pieces of the valve head were lodged in the cylinder and the exhaust system. The examination of the valve revealed that the valve head separated at the valve stem attach point. The valve stem remained in a normally installed positon, and functioned normally when the engine drive train was rotated. A review of the engine maintenance logs disclosed that this engine had a previous exhaust valve failure 931 hours ago. The exhaust valve part number was SA-64612. (-23) pilot's statement: on December 3, 1998, my student and I took off from dare county regional airport (mqi) at approximately 1830Z. The preflight inspection and pre takeoff run up were normal and we were full of fuel. We made a touch and go at elizabeth city (ecg) and edenton (ede) approximately one (1) hour into the flight, the plane experienced an engine roughness and a partial loss of power. I selected a field that appeared most suitable for the forced off field landing. During the landing, while trying to avoid trees, drainage ditches, and a dike for a hog lagoon, the aircraft rotated 180 degrees after touchdown and suffered substantial damage. Neither my student nor I were injured during or after the landing. The preliminary post accident inspection indicates a possible exhaust valve failure.