NTSB Identification: LAX95IA246.
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Scheduled 14 CFR operation of NORTHWEST AIRLINES, INC. (D.B.A. operation of NORTHWEST AIRLINES, INC. )
Incident occurred Tuesday, July 04, 1995 in LAS VEGAS, NV
Probable Cause Approval Date: 02/14/1996
Aircraft: BOEING 727-257, registration: N712RC
Injuries: 53 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.
AFTER TOUCHDOWN THE CREW FELT THE AIRCRAFT LURCH TO THE RIGHT. AN INSPECTION REVEALED THAT THE RIGHT MAIN LANDING GEAR OUTER CYLINDER TRUNNION HAD SHEARED AT THE MAIN LANDING GEAR BEAM TRUNNION SUPPORT. THE OPERATOR REPORTED TWO SIMILAR PRIOR INCIDENTS. THE FAILED TRUNNION AND THE TWO FROM THE PRIOR OCCURRENCES WERE SENT TO BOEING FOR DETAILED METALLURGICAL ANALYSIS. ACCORDING TO THE LAB REPORT, ALL THREE TRUNNIONS FAILED AS A RESULT OF A FATIGUE FRACTURE AND STRESS CORROSION WHICH INITIATED IN THE BLENDOUT TRANSITION RADIUS BETWEEN THE MACHINED DOWN TRUNNION JOURNAL AND THE CYLINDER. THE RADIUS WAS FOUND TO BE BELOW THE SPECIFIED MINIMUM AND NICKEL PLATING EXTENDED INTO THE AREA IN EXCESS OF THE LENGTH PERMITTED BY THE OVERHAUL MANUAL. SEVERE THROUGH-THICKNESS CRACKING IN THE CHROME PLATING WAS ALSO FOUND IN ALL THREE TRUNNIONS. ACCORDING TO THE OPERATOR, BOEING 727 LANDING GEAR OVERHAUL REWORK IS PERFORMED IN-HOUSE.
The National Transportation Safety Board determines the probable cause(s) of this incident to be: A shear failure of the right main landing gear outer cylinder trunnion due to fatigue and stress corrosion, and the operator's inadequate and improper overhaul procedures. Full narrative available
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