NTSB Identification: ANC97LA112.
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Accident occurred Friday, July 25, 1997 in PALMER, AK
Probable Cause Approval Date: 05/04/1998
Aircraft: Cessna 206, registration: N9412Z
Injuries: 1 Serious,2 Minor.

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

While in cruise flight at 3,000 feet MSL over remote terrain, the engine suddenly quit. The pilot selected a flat area for an emergency landing. After touchdown, the float assemblies were torn off the fuselage, and the airplane nosed over. During the postaccident examination of the engine, one cylinder bolt was found loose, and the engine case displayed evidence of fretting. The crankshaft was broken. A metallurgical examination of the crankshaft revealed a fracture pattern typical of fatigue cracking. The number one engine cylinder had been replaced about 585 service 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, and an inadequate engine cylinder replacement by maintenance personnel. A factor in the accident was unsuitable terrain for a forced landing.

Full narrative available

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