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UAL 232: The Sioux City Crash

© Patrick Worden

It was a strange convergence of events that brought about this disaster. It was an equally unlikely amount of good fortune that allowed the DC-10 to make it to the runway at Sioux City Gateway Airport, and for nearly 200 lives to be saved. Jung might have called it synchronicity, others might simply say it was an extreme example of Murphy's Law. What it amounted to was one of the most startling and fascinating accidents in commercial air history.

On 19 July, 1989 United Airlines Flight 232 was enroute from Denver to Chicago. At about 4:00 p.m., with First Officer William Records at the controls, the aircraft experienced a catastrophic failure of the number two (center) engine. The DC-10 is a favored aircraft among pilots mainly because of its ability to experience such failures and return to earth safely. As Captain Al Haynes, the hero of UAL 232 said later, "The DC-10 has three engines; you only need one to fly." This, coupled with its triply-redundant hydraulic systems, meant that an accident of the type that UAL 232 experienced had odds against of something like a billion to one. And the odds of a flight crew coping with such an emergency as competently as did the crew of UAL 232 are practically non-existent.

What happened was, a manufacturing defect in the fan blade of the number two engine resulted in increasingly worse metal fatigue every time the engine was operated. Seventeen years worth of routine maintenance and six fluoroscopic examinations had failed to reveal the defect. On the afternoon of 19 July, 1989 the stress on the defect reached the breaking point. In the course of one revolution, the stricken fan broke into hundreds of shards, which sprayed explosively from the engine housing and peppered the horizontal stabilizer and the cone section of the tail. All three hydraulic lines were severed, instantaneously making moot the designers' contingency of redundant hydraulic systems. With all hydraulics gone, the aircraft lost all ability to control the ailerons, rudders, flaps, spoilers, landing gear brakes and nosewheel steering. It was a systems loss so catastrophic, and presumably so remote, that no one had ever planned for its eventuality. If anyone had ever thought about it, they would have written it off as a non-survivable accident.

But luck was not completely against the 285 passengers and 11 crew. Good fortune was immediately discovered when Dennis Fitch, a deadheading United pilot and DC-10 instructor, came foreward to offer his assistance. Fitch, Haynes and Records began controlling the aircraft the only way they could: with the engine throttles. They found that by carefully feathering the one and three engines, they could effect right or left turns. They still had no control over pitch or airspeed, but since the craft was already in a slightly nose-down attitude, they found they could slowly lose altitude simply by circling. They had been flying at 37,000 feet when the accident occurred; they managed to descend to 9,000 feet by the time they began lining up for their approach to Sioux City Gateway.

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