Incident Overview
During a night flight at approximately 10,000 feet mean sea level (msl), the flight reported an engine problem, declared an emergency, and requested vectors to the nearest airport. The pilot stated, '...we got a fire in the right engine.' While diverting, the pilot was unable to maintain altitude, and the airplane descended to about 1,700 feet. Ridges in the area had tops between 2,500 and 2,800 feet. About 15 miles from the alternate airport, the airplane struck trees at an elevation of approximately 1,720 feet and crashed.
Examination of the Right Engine
Examination of the right engine revealed that the last 8 to 12 inches of the right overboard tube had separated circumferentially from the exhaust system. A metallurgical examination of the exhaust stack showed evidence of fatigue; there were numerous hot gas corrosion cracks that originated at the interior surface and propagated through the wall thickness of the stack. The evidence indicated that a breach of the right exhaust stack allowed hot, high-velocity gases to escape and initiate a fire.
Weather Conditions
The weather at Altoon was reported as: 8,000 feet scattered, visibility 3 miles with fog and haze.