What happened
While performing a normal cruise flight, the pilot reported that the engine RPM was decreasing while the oil temperature was increasing. Following these indications, the engine seized. The pilot's forward visibility became severely restricted because oil covered the windscreen.
During the attempt to land, the pilot overshot the intended field. The aircraft subsequently collided with a fence and then experienced a nose-over.
The investigation
An examination of the engine revealed that the end cap of the number 3 cylinder connecting rod had separated, exited the engine case, and come to rest in the oil sump.
Personnel from Lycoming Engine stated that the separation of the rod cap resulted from a lack of lubrication. This lack of lubrication caused the rod bolts to stretch and lose their torque, which allowed one of the two nuts to vibrate off. The remaining rod bolt failed due to overload. Records indicated the engine had received a top overhaul 136 hours prior to the accident, and a major overhaul had been performed 2,122 hours earlier.