19 July 1989: Sioux City

On 19 July 1989, United Airlines Flight 232, McDonnell Douglas DC-10 N1819U, en-route from Denver to Philadelphia, suffered an uncontained failure of the number 2 General Electric CF6 engine’s fan disc.  This resulted in crippling damage to the aircraft’s hydraulics and flight controls. The crew under Captain Al Haynes managed to control the aircraft by throttle movements and made a crash landing at Sioux City airport in Iowa, which fortuitously was in the middle of an emergency response exercise at the time.  Of the 296 people on board, 111 died in the accident but mraculously 185 survived.

Impact (Credit: Dave Boxum, KTIV Channel 4)

The National Transportation Safety Board (NTSB) determined that the probable cause was:

… 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 undetected 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 operate the DC-10′s flight controls.

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