SIOUX CITY, IA, USA
N1819U
MCDONNELL DOUGLAS DC-10-10
The Safety Board's full report on this investigation is provided as Aviation Accident Report number AAR-90/06. To obtain a copy of this report, or to view the executive summary online, please see the Web site at http://www.ntsb.gov/publictn/publictn.htm UNITED AIRLINE FLT 232 WAS CRUISING AT FL 370, WHEN THERE WAS A CATASTROPHIC FAILURE OF THE # 2 (TAIL MOUNTED) ENG. THIS WAS DUE TO SEPN, FRAGMENTATION & FORCEFUL DISCHARGE OF THE STAGE 1 FAN ROTOR ASSEMBLY PARTS FM THE #2 ENG (UNCONTAINED FAILURE), WHICH LED TO LOSS OF THE 3 HYD SYSTEMS THAT POWERED THE FLT CTLS. THE FLIGHTCREW EXPERIENCED SEVERE DIFFICULTIES CTLG THE ACFT, WHICH SUBSEQUENTLY CRASHED DRG AN EMERG LNDG AT SIOUX CITY. AN INV REVEALED EVIDENCE CONCERNING LIMITATIONS IN INSPN & QUALITY CTL PROC USED DRG ENG OVERHAUL, WHICH RESULTED IN A FAILURE TO DETECT A FATIGUE CRACK, ORIGINATING FM A PREVIOUSLY UNDETECTED METALLURGICAL DEFECT IN A CRITICAL AREA OF THE STATE 1 FAN DISK. (SEE: NTSB/AAR-90/06)
THE INADEQUATE CONSIDERATION GIVEN TO HUMAN FACTORS LIMITATIONS IN THE INSPECTION AND QUALITY CONTROL PROCEDURES USED BY UNITED AIRLINES' ENGINE OVERHAUL FACILITY WHICH RESULTED IN THE FAILURE TO DETECT A FATIGUE CRACK ORIGINATING FROM A PREVIOUSLY UNDECTECTED METALLURGICAL DEFECT LOCATED IN A CRITICAL AREA OF THE STAGE 1 FAN DISK THAT WAS MANUFACTURED BY GENERAL ELECTRIC AIRCRAFT ENGINES. THE SUBSEQUENT CATASTROPHIC DISINTEGRATION OF THE DISK RESULTED IN THE LIBERATION OF DEBRIS IN A PATTERN OF DISTRIBUTION AND WITH ENERGY LEVELS THAT EXCEEDED THE LEVEL OF PROTECTION PROVIDED BY DESIGN FEATURES OF THE HYDRAULIC SYSTEMS THAT OPERATED THE DC-10'S FLIGHT CONTROLS.
Source: NTSB Aviation Accident Database
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