United Airlines Flight 232 Mid Air Engine Catastrophe

Did the DC10 have too many safety problems?

United Airlines Flight 232 was a scheduled flight from Stapleton International Airport in Denver, Colorado, to O'Hare International Airport in Chicago. On July 19, 1989, the DC-10 (registered N1819U) operating the route crash-landed in Sioux City, Iowa, after suffering catastrophic failure of its tail-mounted engine, which led to the loss of all flight controls. Of the 296 people on board, 111 died in the accident while 185 survived. Despite the deaths, the accident is considered a prime example of successful crew resource management due to the manner in which the flight crew handled the emergency, and the high number of survivors considering that the airplane was landed without conventional control. The flight crew became well known as a result of their actions, in particular the captain, Alfred C. Haynes, and a DC-10 instructor on board who offered his assistance, Dennis E. Fitch.

The uncontained manner in which the engine failed resulted in high-speed shrapnel being hurled from the engine; this shrapnel penetrated the hydraulic lines of all three independent hydraulic systems on board the aircraft, which rapidly lost their hydraulic fluid. As the flight controls on the DC-10 are hydraulically powered, the flight crew lost their ability to operate nearly all of them. Despite these losses, the crew were able to attain and then maintain limited control by using the only systems still workable: the two remaining engines. By utilizing each engine independently, the crew made rough steering adjustments, and by using the engines together they were able to roughly adjust altitude. The crew guided the crippled jet to Sioux Gateway Airport and lined it up for landing on one of the runways. Without the use of flaps and slats, they were unable to slow down for landing, and were forced to attempt landing at a very high airspeed. The aircraft also landed at an extremely high rate of descent due to the inability to flare (reduce the rate of descent prior to touch down by increasing pitch). As a result, upon touchdown the aircraft broke apart, rolled over and caught fire. The largest section came to rest in a cornfield next to the runway. Despite the ferocity of the accident, 185 (62.5%) passengers and crew survived owing to a variety of factors including the relatively controlled manner of the crash and the early notification of emergency services.

The cause of the engine failure was traced back to a manufacturing defect in the fan disk, which had microscopic cracks due to impurities. The cracking was present during maintenance inspections and should have been detected by maintenance personnel, revealing shortcomings in the maintenance processes.

The accident had a strong impact on the industry. DC-10s were modified with hydraulic fuses to prevent catastrophic loss of hydraulic fluid should a similar failure occur again. These modifications were also included in the DC-10's direct successor, the MD-11. Research has been conducted to see whether computers might be able to control aircraft using the engines alone, improving on what humans can do unaided.
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