NTSB Identification: FTW96FA282.
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Scheduled 14 CFR operation of WINGS WEST AIRLINES, INC. (D.B.A. AMERICAN EAGLE )
Accident occurred Monday, July 01, 1996 in DFW AIRPORT, TX
Probable Cause Approval Date: 03/31/1998
Aircraft: Saab-Scania AB (Saab) SF340B, registration: N335AE
Injuries: 15 Uninjured.
NTSB investigators either traveled in support of this investigation or conducted a significant amount of investigative work without any travel, and used data obtained from various sources to prepare this aircraft accident report.
The airplane departed runway 13L and climbed to an altitude of approximately 400 feet AGL when the flight crew 'heard a loud bang.' The right engine upper cowling departed the airplane, the right engine shut itself down, and the right propeller automatically feathered. The flight crew declared an emergency and executed a single engine landing without further incident. Examination of the airplane's right CT7-9B turboprop engine revealed that the Stage 2 turbine disk was missing and that approximately one third of the disk was found in the right landing light compartment. One end of the disk fragment progressed through a cooling air hole and there was evidence of a fatigue fracture that had initiated from multiple origins on the inboard side of the cooling air hole. Research revealed a layer of deformed microstructure and an associated zone of increased disk hardness near the origin area of the fatigue crack. Test disks were drilled using dull and worn drill bits which resulted in plastic deformation and increased hardness of the inner diameter hole surfaces. The manufacturer reported that the deformed microstructure correlates to a zone of reduced fatigue properties.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: The manufacturer's inadequate procedure for manufacturing the number two turbine disk. Full narrative available
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