Event Description
While cruising, the aircraft's engine developed a vibration and began running roughly. The pilot reduced power and established a track for an emergency landing at a nearby county airport. However, the airplane crashed approximately one mile short of the airport.
Examination Findings
Examination of the engine assembly disclosed that a piece of the crankcase was broken above the number 2 cylinder. The cylinder was partially secured by only one hold down nut on the bottom left side. Further examination revealed fretting between the cylinder flange and the engine case. All crankcase fractures showed signs of overload failure.
Maintenance History
The engine maintenance logs disclosed that the engine's crankcase had been replaced on October 24, 1990. This engine malfunction occurred 258 hours after that replacement.
Subsequent Service Bulletin
Following this accident, Continental Motors issued a service bulletin which increased the torque value for the cylinder hold down nuts. The bulletin also instructed that the standard six point hold down nuts be replaced with twelve point nuts during overhaul.