Incident Overview
A pilot reported that the airplane experienced a severe vibration while at 2,000 feet MSL. The airplane was descending at 200 feet per minute with the throttle fully forward, and the tachometer indicated 1,700 RPM. The nearest airport was approximately 6 miles away. The pilot radioed the airport to advise of the situation and entered the traffic pattern on the base leg.
Pilot Actions
During the approach, the pilot noted that the airplane was high on the approach. He recalled from his training that it was better to be high and fast than low and slow. The airplane touched down about halfway down the 3,100-foot-long runway. After touchdown, the airplane exited the runway into a 6-foot-wide culvert, causing the aircraft to nose over.
Examination Findings
Following the incident, the Federal Aviation Administration (FAA) conducted an examination of the engine. A compression test revealed a leak. The leaking cylinder was removed and sent to the National Transportation Safety Board (NTSB) laboratory in Washington, DC, for further analysis. A metallurgical examination determined that the exhaust valve had separated due to fatigue cracking. The cracking initiated in the radius between the stem and the head of the valve.