United Airlines Flight 232

Encyclopedia : U : UN : UNI : United Airlines Flight 232

|) | }} }} | Passengers=296| Crew=11 | Survivors=184 | }}

United Airlines flight 232 "UA232", "UAL232" (United 232 Heavy) was a scheduled flight operated by United Airlines. On July 19, 1989, its Douglas DC-10-10 (Registration |) | }} }}) suffered an uncontained failure of its number 2 engine (mounted in the tail), which destroyed all three of the aircraft's hydraulic systems. With no controls working except the throttles for the two remaining engines, it broke up during an emergency landing on the runway at Sioux City, Iowa killing 112 of its 296 passengers and one of the 11 crew members. It is one of the best-recognized air disasters in American aviation history, largely due to the presence of television crews near the airfield as the plane landed end-over-end in a spectacular fireball.

Owing to the extraordinary skill of the crew and a DC-10 instructor pilot, 184 passengers and 10 crew members survived. The crash is considered one of the textbook examples of successful crew resource management, due to the excellent use of all the resources available aboard the plane for help during the emergency.

The incident was made the subject of the 1992 television movie, , and was also featured in an episode of Seconds From Disaster on the National Geographic Channel. It was also one of the inspirations for Peter Weir's 1993 film version of Fearless, adapted from a novel by Rafael Yglesias.

Contents

1 History of the flight
2 Flight crew performance
3 Causes
4 Increased chances for survival
5 1994 memorial
6 See also
7 Notable after the crash
8 References
9 External links

History of the flight

The flight took off at 14:09 (CDT) from Stapleton International Airport, Denver, Colorado and was due to fly to Philadelphia International Airport in Philadelphia, Pennsylvania via O'Hare International Airport in Chicago, Illinois. At 15:16 the fan disk of its tail-mounted GE CF6-6 engine fragmented catastrophically and the engine assembly failed to contain the debris which severed all three of the airplane's triply redundant hydraulic systems, allowing the hydraulic fluid to drain away. The odds of all three hydraulic systems failing simultaneously had previously been calculated as high as a billion to one, but a similar failure had occurred in incidents such as Japan Airlines flight 123. Most of the fan disc split into two and burst out the side of the engine cowling. This destroyed hydraulic lines toward the rear of the aircraft that controlled the rudder and the horizontal stabilizer (used to control the airliner's pitch). Pieces from the fan disc also punctured the other two hydraulic systems.

Captain Alfred C. Haynes and his flight crew soon felt a jolt going through the aircraft, and warning lights showed that the autopilot had disengaged (due to the large jolt and engine problems being considered as problems best left to the pilot) and the number two engine (the one on the tailfin) was malfunctioning. The engine was immediately shut down, and vibrations from the damaged engine ceased. The pilot noticed that the airplane was fractionally off-course, and moved his control column slightly in order to correct this. However, the plane would not respond. When the flight crew looked over their instruments they were horrified to discover that the pressure gauges for each of the hydraulic systems was registering zero. The crew realized that the initial failure had left all control surfaces on the airplane immovable. As the triple failure of the hydraulic systems had been considered impossible by the aircraft engineers, there was no other means of safely controlling the aircraft. It had a continual tendency to turn to the right and was difficult to maintain on a stable course, due to damage caused to the tailfin being heavier on the right than on the left, as the largest piece of the fan blade exited on the right. The plane quickly began to soar up and then plunge back down uncontrollably, which is characteristic of accidents where hydraulic power was lost. The flight crew discovered that the only way to control the plane was by adjusting the thrust on the two remaining wing-mounted engines. Dennis E. Fitch, a DC-10 flight instructor was deadheading as a passenger on the plane, and offered his assistance. As a flight instructor, he knew that the DC-10 was one of the few airplanes designed to be controllable by throttles alone. This method of control is similar to skid steering, but with nothing to skid on, and is accomplished by running one engine faster than the other to turn the plane, and accelerating/decelerating in order to gain or lose altitude. This interested him and so in his spare time he had practiced flying DC-10s on throttles in a flight simulator. The task of flying the plane (using the throttles) was naturally assigned to him. Basic control was now possible. However, the damage to the tailfin was so severe that the plane was only be able to make right hand turns. Air-traffic control (ATC) was contacted and an emergency landing at nearby Sioux Gateway Airport was organized. Landing had originally been planned at the 9,000 foot (2743 m) Runway 31. The difficulties in controlling the aircraft made lining up almost impossible. The plane executed a series of left-hand spirals, with the intention of coming out at the end lined up with runway 31. When they came out they were instead left with an approach on the shorter Runway 22 of 6,600 feet (2012 m) and with little capacity to maneuver. One of the flight crew later remarked that normally a go-around technique (where an aircraft abandons landing and comes round for another attempt) would be implemented, but they would not have been able to keep the plane in the air for that long.

Runway 22 was full of fire trucks, who had been anticipating a landing on runway 31. There was a large scramble as the trucks rushed out of the way. Fortunately, all the vehicles parked there got out of the way before the plane touched down.

Fitch continued to control the aircraft's descent by adjusting engine thrust. On final descent, the right wing dropped and the nose pitched forward. Fitch increased the throttles to counter-act the problem, but the engines did not respond quickly enough. The tip of the right wing contacted the runway first and the aircraft skidded to the right, ignited, and somersaulted several times. 111 people died as a result of the inferno, including several children who were too young have seats of their own (so called 'lap children'). As a result the NTSB added a safety recommendation to the FAA on its "List of Most Wanted Safety Improvements", the response to which was flagged on NTSB's website as an "acceptable response, progressing slowly". It also sparked an ongoing campaign led by a flight attendant on the plane for all children to have seats on aircraft. 184 people survived the accident.

Flight crew performance

In subsequent reconstructions of the circumstances of the accident in flight simulators, no pilot, regardless of seniority, has succeeded in reproducing Fitch's achievement of maneuvering the aircraft as far as the runway. Generally, others lose control while the aircraft is still in mid air.^{[[Citing sources citation needed]]}

Because this type of aircraft control is difficult for humans to achieve, some researchers have attempted to integrate this control ability into computers, especially those in fly-by-wire aircraft. Early attempts to add the ability to real planes were not very successful, the software having been based on experiments conducted in flight simulators where jet engines are usually modeled as "perfect" devices with exactly the same thrust on each engine. Later, programming was updated to compensate for the problem, and planes have been successfully flown with this software installed. However, it remains a rarity on commercial aircraft.

Causes

Investigation assigned the origin of the fracture of the fan disk to a failure of United Airlines maintenance processes to detect an existing fatigue crack. The detection failure arose from poor attention to human factors in United Airlines' specification of maintenance processes.

The true cause of the crash, however, lay in a metal 'inclusion' in the disk and was traced back to the metal processing plant from which the engine part was sourced. It turned out that there was a defect in elimination of gaseous anomalies during the purifying of the (molten) titanium disk ingot. These anomalies, if left unchecked, would contribute to a systematic decrease of the metal's strength over time and, ultimately, its failure. Newer batches used a 'triple vacuum' process to eliminate these impurities.

The subsequent investigation and airworthiness directive also revealed a handful of the titanium fan disks already in service from the same batch of ingots which had started to exhibit the initial cracking symptoms of part failure.

Some portions of the plane that broke away when the fan disk failed were later found in farm fields along the flight path.

Other planes were modified following the accident to incorporate additional backup means of manipulating some of the flight controls even if the three hydraulic systems fail.

Increased chances for survival

Of the 296 people aboard, 111 were killed as a result of the crash. 185 survived the incident. Captain Haynes later told of three contributing factors regarding the actual time of day that allowed for a better chance of survival:

The incident occurred during daylight hours;
The incident occurred as a shift change was occurring at both a regional trauma center and a regional burn center in Sioux City, allowing for more medical personnel to treat the injured; and
The incident occurred when the Iowa Air National Guard was on duty at Sioux Gateway Airport, allowing for 285 trained personnel to assist with triage and evacuation of the wounded.

1994 memorial

There is a statue that depicts Colonel Dennis Nielsen carrying three-year-old survivor Spencer Bailey to safety, which commemorates the heroic rescue efforts shown by the Sioux City community after the crash. The memorial is part of Sioux City's riverfront development located near the Anderson Dance Pavilion.

The memorial features contemplative areas and a tree-lined approach with plaques narrating the terrible crash.

Notable after the crash

Passenger Michael Matz, who is credited with saving the lives of four children in the crash, would go on to train the 2006 Kentucky Derby favorite and winner Barbaro. Three of the children he saved, members of the Roth family (two brothers and a sister), travelled to Louisville for the race. It was the first time they had seen Matz in person for a decade although they had kept in touch over the years.

References

External links

Warning: The following links contain strobing pop-up ads:

From Wikipedia, the Free Encyclopedia. Original article here. Support Wikipedia by contributing or donating.
All text is available under the terms of the GNU Free Documentation License See Wikipedia Copyrights for details.