NTSB Identification: SEA97LA193.
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Accident occurred Monday, August 18, 1997 in EDWALL, WA
Probable Cause Approval Date: 02/15/2000
Aircraft: Cessna TU206G, registration: N6620Z
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 private pilot stated that during climb, about 10 minutes after takeoff, he felt a strong vibration in the engine, followed by an abrupt engine stoppage a few seconds later. During the subsequent forced landing onto rolling terrain that was surrounded by obstructions, the airplane struck a fence post, hit a ditch, and flipped over. An examination of the engine revealed that the crankshaft had fractured. The fracture was the result of fatigue cracking that initiated at the surface of the aft radius of the no. 2 main bearing journal. Heavy rubbing damage in the aft radius indicated that the bearing shifted aft and scored the radius resulting in fatigue initiation at the surface. A visual inspection of the crankcase mating surfaces revealed fretting, indicating that there was relative motion between the two crankcase halves. No evidence of heat distress or lack of lubrication was found. The engine, a Continental TSIO-520, had received a 'top' overhaul about 45 operating hours before the accident.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: A fatigue failure of the engine crankshaft. Factors contributing to the accident were the rolling terrain, and the fence. Full narrative available
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