NTSB Identification: ANC98LA078.
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Nonscheduled 14 CFR
Accident occurred Friday, June 19, 1998 in HOLY CROSS, AK
Probable Cause Approval Date: 07/02/1999
Aircraft: Cessna 207, registration: N1673U
Injuries: 4 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 and three passengers, departed on an air taxi flight over remote terrain. While in cruise flight about 2,200 feet, the engine oil pressure began to drop, and the engine oil temperature began to rise. The pilot decided to divert to the nearest airport. The engine quit running, and the pilot selected an emergency landing area on a sand bar along a river that contained several willow trees. During the landing, the airplane received damage to the wings and fuselage. The engine had accrued 1,491 hours since an overhaul. During that time, seven engine cylinder changes were performed by company maintenance personnel. An examination of the engine revealed the crankshaft was broken along the aft, lower edge of the number two cheek journal, at the forward radius of the number two main bearing journal. The fracture line was straight and flat, through the full dimension of the number two cheek journal, and was oriented perpendicular to the longitudinal axis of the crankshaft. The number two main bearing was broken and flattened. The number two main bearing saddle was flattened and distorted. The left and right engine case halves mating surface exhibited galling/fretting at the number two main journal bolt holes.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: The improper installation/undertorquing of the engine crankcase bolts by company maintenance personnel, and a subsequent fracture of the engine crankshaft. A factor in the accident was unsuitable terrain for a forced landing. Full narrative available
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