What happened
Approximately 30 minutes into the flight, the pilot observed smoke entering the cockpit through the right-side defrost duct. In response to the smoke, the pilot elected to divert to the nearest airport, located 14 nautical miles north of the aircraft's position.
As the aircraft reached a point approximately 3 miles from the destination airport, a fire developed inside the cockpit in the area near the right-side rudder pedals. The pilot decreased engine power and began a descent toward a field. The final memory recorded by the pilot was the aircraft crossing power lines.
The investigation
A detailed inspection of the muffler identified two distinct areas of burn-through damage. Additionally, the aircraft firewall exhibited a 14-inch diameter area showing evidence of severe overheating. Examination of maintenance records revealed that there was no indication the exhaust muffler had ever been replaced.