NTSB Identification: ERA11IA521
14 CFR Part 91: General Aviation
Incident occurred Sunday, September 18, 2011 in New Haven, CT
Probable Cause Approval Date: 02/14/2013
Aircraft: BEECH V35, registration: N275BM
Injuries: 2 Uninjured.
NTSB investigators used data provided by various sources and may not have traveled in support of this investigation to prepare this aircraft incident report.
During the climb after takeoff, as the airplane approached 6,000 feet mean sea level, the crankshaft fractured, and the airplane experienced a total loss of engine power. The forward portion of the crankshaft, with the propeller attached, departed the engine. The pilot declared an emergency and returned to the departure airport where he performed a forced landing on a runway. The airplane sustained minor nose gear damage when it overran the runway. Examination of the crankshaft revealed that it was fractured across the No. 4 main journal. Metallurgical examination revealed cracks that initiated on the bearing surface near an oil transfer tube and propagated in fatigue.
At the time of the incident, the engine had been operated for about 910 total hours, about 500 hours of which had occurred since maintenance, which was performed about 2 1/2 years before the incident and included the reinstallation of the Nos. 2 and 4 cylinders. The crankcase adjacent to the fractured portion of the crankshaft showed significant fretting on the mating surfaces, possibly due to incorrect torque applied during the previous cylinder repair; however, the investigation could not determine the relevance of that repair, if any, due to the time that had elapsed since the repair was completed.
The National Transportation Safety Board determines the probable cause(s) of this incident to be: The in-flight fatigue failure of the engine’s crankshaft, which resulted in the separation of the forward portion of the crankshaft and the propeller. Full narrative available
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