Accident Description
According to the pilot, approximately 20 minutes after departure while in cruise flight, the airplane's engine began to 'run rough' and vibrate. The pilot reduced power in attempts to dampen the vibration and initiated a precautionary landing to a nearby airport.
As the airplane touched down, the pilot noticed a dirt embankment, approximately 2 feet high, running along the runway centerline. Subsequently, the airplane contacted the embankment, exited the runway surface, struck a fence and trees, and came to a stop upright.
Post-Accident Findings
A test run of the engine revealed that the engine would not run with the ignition switch in the LEFT position and would run rough in the BOTH position. Examination of the left magneto showed that the resistance was less than 16,000 ohms, failing to meet the manufacturer's specifications. Additionally, the number 3, 4, and 5 rear spark plugs exhibited oil and lead deposits.