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United flight 232 was enroute from Denver to Chicago on the afternoon of July 19, 1989. On the flight deck at FL370 that day was Captain Al Haynes, a 30,000 hour pilot, First Officer William Records, and Flight Engineer Dudley Dvorak. Along with eight flight attendants, there were 285 passengers on board the DC-10. Shortly after crossing into Iowa, the aircraft began a gentle right turn to take it direct to Chicago.

With Records flying, there was a loud bang from the rear of the aircraft, causing the entire aircraft to shudder. Haynes saw that the number two (centre) engine had failed and asked for the engine shutdown checklist to be started. As Dvorak began the checklist, he noticed that all three hydraulic systems were loosing pressure and quantity. Instead of straitening out, the aircraft continued it's right turn. Records disconnected the autopilot and attempted to level the aircraft out, but he found that he could no longer control the aircraft.

Meanwhile, the aircraft had now began a descent. Haynes attempted to fly the aircraft via his controls but found the same result. He then eased the power back on the port engine and the excess thrust on the starboard side began to roll the aircraft back to wings-level. The crew then gave a call to Minneapolis Centre relaying their problem. The controller initially gave 232 a vector towards Des Moines International, but seeing that the aircraft had continued it's turn back towards the west before straightening out, he then gave 232 a vector towards Sioux City Gateway Airport. Located on the east bank of the Missouri river, Gateway had a runway of 9,000ft and another of 6,600ft.

It had a third runway of nearly 7,000ft which had been closed for some time. Haynes alerted the passengers that they had lost the number two engine and then instructed the flight attendants to prepare the passengers for an emergency landing. The crew had come to the realization that they were now unable to move any of the control surfaces and had only the engine power of the left and right engines to control the aircraft. It turned out that one of the passengers on board flight 232 was Dennis Fitch, a United training and check pilot with over 3,000 hours on the DC-10. Haynes asked Fitch to go back and look out the windows to check for any structural damage. When Fitch returned to the flight deck, he informed Haynes that the both of the inboard ailerons were sticking up, but none of the controls appeared to be damaged or moving.

232 Explodes on Impact

Haynes asked Fitch to take control of the throttle levers to allow the crew time to sort out the other decisions they were facing. Fitch knelt down in front of the floor and began to work with the throttles to maintain control of the aircraft. During this time, the aircraft had completed two slow right turns while descending. Calling Sioux City Approach, Haynes requested the ILS frequency for 9,000ft runway 31. The crew continued to prepare for emergency landing, dumping fuel and extending the landing gear. A flight attendant reported that she saw damage to the aircraft's horizontal stabilizer which Dvorak went back and confirmed.

The aircraft was now descending through 9,000ft some 21 miles northeast of the airport. Approach asked 232 to fly southbound to keep it east of the city and set it up for an approach to runway 31. Fitch was unable to fight the aircraft's continuing efforts to turn right and, instead of turning southbound, the aircraft again flew a 360 which Fitch was able to stop just as the airport lay ahead of them. They were now 12 miles from the airport and lined up with the closed runway, the 6888ft runway 22. Fortunately, there was an open field at the far end of the runway. The controller cleared them to use the closed runway and the crew managed to get the aircraft flying straight. Unfortunately, they couldn't accurately control the airspeed and sink rate. They were descending at over 1,600feet/minute at around 215kts. In an incredible feat of airmanship, they managed to touch down near the beginning of the runway just off the centreline.

Unfortunately, the starboard wingtip touched down just prior to the landing gear, pulling the aircraft sideways. The excess airspeed and high sink rate caused the aircraft to break up on impact, igniting into a huge fireball. Amazingly, despite the explosion and high speed break-up, 185 people survived the accident, including all four crew members.
......Examination of the wreckage showed that portions of the number 2 engine fan blades were embedded in the empennage. Missing from the wreckage was number 2 engine fan module, which had separated in flight. The failure of the number 2 engine sent fragments through the empennage, rendering all three hydraulic systems inoperable, all of which had critical components that ran together near the engine casing. Several farmers living northeast of the city reported finding various parts of the aircraft on their properties.

Investigators were able to recover the aircraft's tailcone as well as half of the fan containment ring. Also found were fan blade fragments and parts of the hydraulic lines. Three months after the accident, two pieces of the engine fan disk were found in the fields near where the first pieces were located. Together the pieces made up nearly the entire fan disk assembly. Two large fractures were found in the disk, indicating overstress failure.

Metallurgical examination showed that the primary fracture had resulted from a fatigued section on the inside diameter of the disk. Further examination showed that the fatiguing had resulted in a small cavity on the surface of the disk, apparently a defect in manufacturing. The 17 year old disk had undergone routine maintenance and six times had been subjected to fluorescent penetration inspections. Investigators concluded that human error was responsible in improperly identifying the fatigued area before the accident.

Subsequent simulator tests showed that other DC-10 crews were unable to repeat the effort of the crew of 232. Investigators concluded that, in it's damaged condition, it was not possible to land the aircraft on a runway. As a result, the crew was giving much praise for managing to put the aircraft down just off the runway centreline and saving as many lives as they did.