NTSB Identification: CHI99LA253.
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Accident occurred Sunday, July 25, 1999 in BROOKFIELD, MO
Probable Cause Approval Date: 11/30/2000
Aircraft: Beech B36TC, registration: N587DL
Injuries: 2 Uninjured.

NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.

The pilot advised controllers that the aircraft engine was running rough and he was shutting it down. The pilot later stated that the engine began to shake violently and that he was concerned that the engine would become detached from the engine mount. The pilot executed a forced landing on a farm field. The aircraft had accumulated a total time of 62.5 hours and the new engine had accumulated 42 hours. External examination of the engine revealed three broken engine mounts. No other external evidence of damage was noted. The engine case was disassembled and the engine crankshaft was found to be broken at the connecting rod journal for the number one cylinder. A metallurgical analysis revealed striations typical of fatigue cracking. The fatigue origin was found to be 0.033 inches below the surface. No metallurgical anomalies were noted in a section made near the fracture origin.

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

the total mechanical failure of the engine crankshaft due to fatigue. A factor was the ditch encountered on landing.

Full narrative available

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