Incident Overview
A pilot reported hearing a knocking sound while climbing through 5,000 feet after takeoff. The knocking was followed by a loud noise and engine vibration. The pilot stated that he apparently had lost a cylinder and that oil pressure was dropping. He declared an emergency and received radar vectors. After descending through clouds, the pilot reported that smoke and flames were coming from the cowling. The pilot elected to make a forced landing in a small field. On touchdown, the nose gear collapsed and the aircraft nosed over.
Engine Examination
Examination of the engine revealed two broken connecting rods and two crankcase throughbolts that were undertorqued. The crankshaft main bearing had rotated, blocking the oil passage to the other crankshaft bearings. Overheating of the connecting rod journals and bearings was evident. The number 2 cylinder had been replaced on January 2, 1989, 28 hours before the accident.
Sequence of Events
The pilot initiated the takeoff and climbed normally until reaching 5,000 feet, when the knocking sound began. The engine vibrations and oil pressure drop occurred shortly thereafter. After the emergency declaration and vectoring, the pilot descended through cloud cover, at which point smoke and flames became visible from the engine cowling. The forced landing was executed in a small field, but the nose gear failed upon touchdown, causing the aircraft to flip over.