NTSB Identification: FTW94IA070.
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Scheduled 14 CFR SOUTHWEST AIRLINES
Incident occurred Wednesday, January 19, 1994 in LITTLE ROCK, AR
Probable Cause Approval Date: 02/14/1995
Aircraft: BOEING 737-2H4, registration: N53SW
Injuries: 67 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.
ONE OF TWO LEFT MAIN WHEELS SEPARATED. THE SUBSEQUENT LANDING WAS UNEVENTFUL. THE TIRE AND WHEEL REMAINED INTACT. THE AXLE NUT WAS FOUND WITH THE LOCKING RETAINER RING INSTALLED IN THE GROOVE ON THE NUT. EVIDENCE COLLECTED BY THE MANUFACTURER INDICATED THE RETAINER NUT SPUN OFF OF THE AXLE WITH THE ROTATION OF THE WHEEL. ACCORDING TO THE MANUFACTURER, 'THIS CONDITION COULD ONLY OCCUR IF THE LOCKING CAPABILITY OF THE RETAINING RING WAS LOST DUE TO THE RETAINING RING NOT FULLY SEATED.' THE MANUFACTURER MEASURED THE THREAD DIMENSIONS OF THE INNER CYLINDER AXLES AND RETAINER NUTS. THREADS ON BOTH AXLES AND RETAINER NUTS WERE BEYOND THE MANUFACTURER'S WEAR LIMITS. ON THE INCIDENT AXLE, THREAD ENGAGEMENT MEASUREMENT (EXCLUDING THE DAMAGED AREA) FOR THE AXLE WAS AT THE MANUFACTURER'S WEAR LIMIT. ACCORDING TO THE MANUFACTURER, WEAR DID NOT COMPROMISE THE CAPABILITY OF THE NUT AND AXLE. THEIR CROSS SECTION OF THE NUT 'DID NOT EXHIBIT ENOUGH DEFORMATION TO SUPPORT MIGRATION OF THE NUT OFF THE AXLE.'
The National Transportation Safety Board determines the probable cause(s) of this incident to be: WAS THE LANDING GEAR SEPARATION DUE TO AN UNDETERMINED CAUSE. Full narrative available
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