Accident Sequence
Approximately 49 minutes after takeoff, while in cruise flight, the pilot declared a mayday and reported that the engine had quit. Unable to land at the closest airport, he maneuvered the airplane for a forced landing to a field. During the descent, the airplane collided with trees.
Engine Examination
Post-accident examination of the engine revealed that connecting rods Nos. 1, 2, and 4 were broken. Heat distress was noted at the connecting rod journals for cylinders Nos. 1, 2, and 4. Fretting was observed at the upper support boss for the No. 2 main bearing. Both crankcase halves in the area of the No. 2 main bearing saddle showed damage. Brown discoloration was present on the No. 2 main bearing journal.
Maintenance History
The engine had been overhauled in December 1985 and installed in April 1986. In January 1994, cylinders Nos. 3 and 6 were replaced, and the top of the crankcase was sealed. At the time of the accident, the engine had accumulated approximately 995 hours since overhaul and 328 hours since the replacement cylinders were installed. The thru bolt adjacent to the fretted support boss of the No. 2 main bearing is used to secure cylinders Nos. 2 and 3. The oil had last been changed approximately 65 hours before the accident, while the engine manufacturer recommends an oil change every 25 hours.