NTSB Identification: ANC04LA059.
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Accident occurred Saturday, May 22, 2004 in Goodnews, AK
Probable Cause Approval Date: 10/28/2004
Aircraft: Piper PA-31-350, registration: N4105D
Injuries: 1 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 airline transport certificated pilot departed a remote airport in a twin-engine airplane. The airport is located on the coast of the Bering Sea, and has an area of low hills that are northwest of the airport. The pilot said the wind conditions were about 070 degrees magnetic at 25 knots, with gusts to 30 knots. After departure, the pilot reported that he initially climbed the airplane to about 1,200 feet, but as he approached the area of low hills, he descended to about 700 feet. At an indicated airspeed of about 185 knots, the pilot said that the airplane encountered severe turbulence for about 30 seconds, during which his radio headset was dislodged. Upon arrival at his destination, the pilot informed the director of maintenance that during the flight, the airplane encountered turbulence and appeared to have received damage to the wings. The director of maintenance reported that the airplane received structural damage that consisted of wrinkling and rippling of both of the upper wing surfaces, extending about 8 feet outboard from each engine nacelle. In addition, the elevator had wrinkling that extended about 6 inches inboard from each of the outboard hinge attach points. The closest official weather observation station is located about 32 nautical miles south of the accident site. An automated weather observation system (AWOS) was reporting in part: Wind, 110 degrees (true) at 17 knots, gusts to 27 knots; visibility, 7 statute miles; clouds and sky condition, 1,200 feet overcast.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: The pilot's inadequate weather evaluation which resulted in an in-flight encounter with severe turbulence, and his exceedence of the design stress limits resulting in overstress of the wings. A factor contributing to the accident was the presence of turbulence. Full narrative available
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