Primary finding
Probable cause
A partial power loss when the rocker box for one cylinder disengaged. A factor was: unsuitable terrain for a forced landing.
Investigator assessment
Analysis narrative
While on a local area personal flight, the engine rpm dropped from 2,300 to 1,400 rpm followed by engine vibration. The pilot elected to land on the only road in the area which contained a 40 degree right turn along the landing roll path. As the aircraft negotiated the turn, the right wing struck a fence post and the aircraft spun into a ditch. Examination revealed a failure of the right forward cylinder valve rocker box exhaust stud which backed out and prevented the intake valve from working properly.
Source record
Factual narrative
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