NTSB Identification: FTW97IA045.
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Scheduled 14 CFR operation of AMERICAN AIRLINES
Incident occurred Saturday, November 23, 1996 in DFW AIRPORT, TX
Probable Cause Approval Date: 11/06/1998
Aircraft: McDonnell Douglas MD-82, registration: N3507A
Injuries: 3 Minor,116 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 airplane was departing when a thump was felt with a slight left nose pull, and the pilots aborted the takeoff. The pilots taxied clear of the runway and came to a stop. Several flight crews on the ground reported on the tower frequency that the incident airplane's left engine was on fire. The captain initiated evacuation of the airplane. The Airport Rescue and Fire Fighting (ARFF) personnel reported that the engine fire was confined to the tailpipe area. Turbine blades had separated from the number 4 turbine disk, penetrated the engine case, and subsequently damaged the engine pylon and empennage area. The teardown examination of the engine revealed that the Low Pressure Turbine (LPT) shaft was deformed and fractured into two pieces. Heavy coke deposits were identified on both the outer diameter of the LPT shaft and the inner diameter of the center tube. The two pieces of the LPT shaft were twisted and subjected to 'considerable' permanent deformation. The amount of plastic deformation was indicative of exposure to high temperatures. Additionally, the High Pressure Turbine shaft was found with a (one of three) 4 1/2 bearing stack retention pin missing.
The National Transportation Safety Board determines the probable cause(s) of this incident to be: The failure of the low pressure turbine shaft. A factor was the coke build up on the low pressure turbine shaft. Full narrative available
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