Narrative:During a cruise climb, the aircrew noted an unusual vibration; however, attempts to isolate the vibration were unsuccessful. While climbing from FL190 to FL250, the flight engineer went aft to observe the engines & props, but noted nothing unusual. A flight attendant went forward to advise the captain that nothing was observed, when the vibration increased in intensity. As she left the cockpit, she peered out the right window and saw the no. 4 prop separate and strike the aircraft. This caused major damage to the lower fuselage and resulted in decompression of the cabin. The flight controls became jammed and the engines would not respond to throttle movement. The autopilot was used for minimal control and the flight crew were able to divert to Anchorage, AK. They were able to climb and descend by retracting and extending the landing gear with the no. 2 eng shut down. The aircraft was landed safety and the engines were shut down to decelerate. The exact cause of the prop separation was not determined since it fell in the ocean during the occurrence.
Probable Cause:
PROBABLE CAUSE: "Propeller system/accessories..undetermined."
Classification:
Prop/turbine blade separation
Forced landing on runway
Sources:
» NTSB
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This map shows the airport of departure and the intended destination of the flight. The line between the airports does
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Distance from Cold Bay Airport, AK to Seattle/Tacoma International Airport, WA as the crow flies is 2870 km (1794 miles).
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