Narrative
After dispensing a chemical load, the pilot was returning to reload when the engine began running roughly. The pilot noted that fuel flow was erratic, so he turned on the boost pump. The engine stabilized momentarily, but then smoke entered the cockpit and the engine began surging. The pilot subsequently conducted an emergency landing on rough, uneven terrain. During the landing, the aircraft went over on its nose, causing the shoulder harness to fail; however, the lap belt held. After the aircraft came to rest, the pilot evacuated. Subsequently, the aircraft was destroyed by fire.
Examination Findings
An examination of the aircraft revealed a hole in the exhaust pipe on the right side of the engine. The hole was located near the exhaust gas temperature (EGT) probe. This hole allowed exhaust gases to be directed toward fuel lines and electrical wires. The mode of shoulder harness failure could not be determined because the harness was destroyed in the fire.