Incident
Approximately 25 minutes after departure, while in cruise flight at 1,500 feet mean sea level, a sudden vibration shook the airplane. The pilot scanned the engine instruments and noted that everything "appeared to be normal." Subsequently, oil covered the windscreen, severely limiting forward visibility. The pilot initiated a forced landing to a grass field with the landing gear in the retracted position. During the landing, the airplane bounced, and the left wing "skimmed" across the top of a metal cattle feeder before impacting the ground. The airplane then spun around approximately 450 degrees and came to rest upright.
Examination
Examination of the engine revealed two holes on the top and bottom of the engine case between the #1 and #2 cylinders. The #2 connecting rod was found sticking out of the top hole and was not attached to the crankshaft. The #2 connecting rod cap was found separated from the connecting rod. The #2 connecting rod cap attachment bolts, nut, and both bearings were missing and not located. The other attachment bolt was found lodged inside the crankcase next to the #3 cylinder opening. The camshaft exhibited impact damage and was fractured in half at the point where the #2 connecting rod was found positioned.
Maintenance History
Review of the maintenance records revealed the engine had accumulated 997.75 hours since major overhaul at the time of the last annual inspection. Further review indicated that the last entry in the engine logbook was an oil change, with 1097.4 hours since major overhaul.