Incident Summary
While cruising at an altitude of 2,500 feet, the pilot reported that the engine began to run rough and lose revolutions per minute (RPM). The pilot attempted emergency procedures, but the loss of RPM continued. Consequently, the pilot decided to perform an off-airport landing. During the approach to the selected landing area, the engine RPM dropped to 1,200, and the pilot secured the engine.
Forced Landing
During the forced landing, the aircraft impacted a small tree and a fence post. The aircraft came to rest after striking these obstacles.
Examination Findings
A post-incident examination of the engine was conducted. The examination revealed a broken exhaust valve in the number one cylinder. Further metallurgical examination of the broken valve indicated evidence of a progressive failure.