NTSB Identification: ATL92IA169.
The docket is stored on NTSB microfiche number 50001.
Scheduled 14 CFR operation of FLAGSHIP AIRLINES, INC. (D.B.A. AMERICAN EAGLE )
Incident occurred Monday, August 31, 1992 in CHATTANOOGA, TN
Probable Cause Approval Date: 09/14/1993
Aircraft: Saab-Scania AB (Saab) 340B, registration: N245AE
Injuries: 25 Uninjured.

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

THE FLIGHT WAS CRUISING AT AN ALTITUDE OF 15,000 FEET. THE FLIGHT CREW OBSERVED THE PROPELLER OIL PRESSURE FOR THE LEFT ENGINE RISE ABOVE THE RED LINE, AND SHUT THE ENGINE DOWN. THE FLIGHT WAS OVER CHATTANOOGA, TENNESSEE, AND THE PILOT ELECTED TO LAND AT CHATTANOOGA. THE FLIGHT CREW UNSUCCESSFULLY ATTEMPTED SEVERAL TIMES TO FEATHER THE PROPELLER. THE FLIGHT CREW REPORTED THAT AT SOME POINT, PRIOR TO EXITING THE RUNWAY AFTER LANDING, THE AIRCRAFT PROPELLER HAD STOPPED ROTATING. EXAMINATION OF THE PROPELLER GEAR BOX REVEALED THAT THE GEAR BOX WAS SEIZED AS A RESULT OF A FAILURE WITHIN THE GEAR BOX. EXAMINATION OF THE PROPELLER CONTROL UNIT REVEALED THAT THE UNIT WAS FAILED TO PITCHLOCK AS A RESULT OF CONTAMINATED OIL SUPPLY FROM THE GEAR BOX. VELOCITY MINIMUM CONTROL WITH A NON ROTATING PROPELLER HAS NOT BEEN DETERMINED FOR THIS AIRCRAFT.

The National Transportation Safety Board determines the probable cause(s) of this incident to be:

THE FAILURE AND SUBSEQUENT SEIZURE OF THE REDUCTION GEAR BOX, AND THE FAILURE OF THE PROPELLER CONTROL UNIT AS A RESULT OF CONTAMINATED OIL SUPPLY WHICH IS SHARED WITH THE GEAR BOX.

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