Incident
Shortly after taking off, while the aircraft was climbing to cruise altitude, the engine ceased operating. The pilot executed a forced landing in a field, and the aircraft landed hard.
Examination
An examination of the engine disclosed that the crankshaft had fractured at the connecting rod thrust face, just above the rear fillet radius of the No.5 crankpin journal. Metallurgical examination of the crankshaft determined that the failure occurred due to fatigue.
History
A review of the engine logbooks revealed that the engine had been overhauled. During the run-in after that overhaul, a cam follower failed. The engine was subsequently disassembled, and the crankshaft was inspected using the magnaflux method; no defects were noted. The engine was then overhauled a second time and had accumulated approximately 372 hours of operation since that second overhaul.