united airlines flight 232
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United Airlines Flight 232 was a regularly scheduled
United Airlines United Airlines, Inc. is a Major airlines of the United States, major airline in the United States headquartered in Chicago, Chicago, Illinois that operates an extensive domestic and international route network across the United States and six ...
flight from
Stapleton International Airport Stapleton International Airport was a major airport in the western United States, and the primary airport of Denver, Colorado. It opened on October 17, 1929, and was replaced by the current Denver International Airport in 1995. It was a hub f ...
in
Denver Denver ( ) is a List of municipalities in Colorado#Consolidated city and county, consolidated city and county, the List of capitals in the United States, capital and List of municipalities in Colorado, most populous city of the U.S. state of ...
to
O'Hare International Airport Chicago O'Hare International Airport is the primary international airport serving Chicago, Illinois, United States, located on the city's Northwest Side, approximately northwest of the Chicago Loop, Loop business district. The airport is ope ...
in
Chicago Chicago is the List of municipalities in Illinois, most populous city in the U.S. state of Illinois and in the Midwestern United States. With a population of 2,746,388, as of the 2020 United States census, 2020 census, it is the List of Unite ...
, continuing to
Philadelphia International Airport Philadelphia International Airport is the primary international airport serving Philadelphia, Pennsylvania, United States. It served 30.8 million passengers annually in 2024, making it the busiest airport in Pennsylvania and the 21st-busies ...
. On July 19, 1989, the
DC-10 The McDonnell Douglas DC-10 is an American trijet wide-body aircraft manufactured by McDonnell Douglas. The DC-10 was intended to succeed the DC-8 for long-range flights. It first flew on August 29, 1970; it was introduced on August 5, 1971 ...
(registered as N1819U) serving the flight crash-landed at Sioux Gateway Airport in
Sioux City, Iowa Sioux City () is a city in Woodbury County, Iowa, Woodbury and Plymouth County, Iowa, Plymouth counties in the U.S. state of Iowa. The population was 85,797 in the 2020 United States Census, 2020 census, making it the List of cities in Iowa, fo ...
, after suffering a catastrophic failure of its tail-mounted
engine An engine or motor is a machine designed to convert one or more forms of energy into mechanical energy. Available energy sources include potential energy (e.g. energy of the Earth's gravitational field as exploited in hydroelectric power ge ...
due to an unnoticed manufacturing defect in the engine's
fan disk A fan disk is the central hub of a fan in a turbofan engine. Fan blades are attached to the fan disk, which is rotated by a shaft driven by a gas turbine. In modern passenger aircraft, most of the propulsive thrust comes from fans, which ...
, which resulted in the loss of all flight controls. Of the 296 passengers and crew on board, 112 died during the accident, while 184 people survived. Thirteen of the passengers were uninjured. It was the deadliest single-aircraft accident in the history of United Airlines. Despite the fatalities, the accident is considered a good example of successful crew resource management, a new concept at the time. Contributing to the outcome was the crew's decision to recruit the assistance of a company check pilot, onboard as a passenger, to assist controlling the aircraft and troubleshooting of the problem the crew was facing. A majority of those aboard survived; experienced test pilots in simulators were unable to reproduce a survivable landing. It has been termed "The Impossible Landing" as it is considered one of the most impressive landings ever performed in the history of aviation.


Aircraft

The airplane, a
McDonnell Douglas McDonnell Douglas Corporation was a major American Aerospace manufacturer, aerospace manufacturing corporation and defense contractor, formed by the merger of McDonnell Aircraft and the Douglas Aircraft Company in 1967. Between then and its own ...
DC-10-10 (registration ), was delivered in 1971 and owned by United Airlines since then. Before departure on the flight from Denver on July 19, 1989, the airplane had been operated for a total of 43,401 hours and 16,997 cycles (takeoff-landing pairs). The aircraft was equipped with three General Electric CF6-6D high bypass
turbofan A turbofan or fanjet is a type of airbreathing jet engine that is widely used in aircraft engine, aircraft propulsion. The word "turbofan" is a combination of references to the preceding generation engine technology of the turbojet and the add ...
engines produced by
General Electric Aircraft Engines General Electric Company, doing business as GE Aerospace, is an American aircraft engine supplier that is headquartered in Evendale, Ohio, outside Cincinnati. It is the legal successor to the original General Electric Company founded in 1892, w ...
(GEAE). The aircraft's No. 2 (tail-mounted) engine had accumulated 42,436 hours and 16,899 cycles of operating time immediately prior to the accident flight. The DC-10 used three independent hydraulic systems, each powered by one of the aircraft's three engines, to power movement of the aircraft's flight controls. In the event of loss of engine power or primary pump failure, a ram air turbine could provide emergency electrical power for electrically powered auxiliary pumps. These systems were designed to be redundant, such that if two hydraulic systems were inoperable, the one remaining hydraulic system would still permit the full operation and control of the airplane. However, at least one hydraulic system must have fluid present and the ability to hold fluid pressure to control the aircraft. Like other widebody transport aircraft of the time, the DC-10 was not designed to revert to unassisted manual control in the event of total hydraulic failure. The DC-10's hydraulic system was designed and demonstrated to the
Federal Aviation Administration The Federal Aviation Administration (FAA) is a Federal government of the United States, U.S. federal government agency within the United States Department of Transportation, U.S. Department of Transportation that regulates civil aviation in t ...
(FAA) as compliant with regulations that "no single nginefailure or malfunction or probable combination of failures will jeopardize the safe operation of the airplane..."


Crew

Flight 232's captain, Alfred C. "Al" Haynes, 57, was hired by United Airlines in 1956. He was highly experienced and had 29,967 hours of total flight time with United, of which 7,190 were in the DC-10. Haynes' co-pilot was First Officer William R. "Bill" Records, 48. He estimated that he had approximately 20,000 hours of total flight time. He was hired first by National Airlines in 1969. He worked subsequently for
Pan American World Airways Pan American World Airways, originally founded as Pan American Airways and more commonly known as Pan Am, was an airline that was the principal and largest international air carrier and unofficial overseas flag carrier of the United States for ...
. He was hired by United in 1985, and had accrued 665 hours as a DC-10 first officer while at United.
Flight engineer A flight engineer (FE), also sometimes called an air engineer, is a member of an aircraft's flight crew who is responsible for monitoring and operating its complex aircraft systems. In the early era of aviation, the position was sometimes referr ...
Dudley J. Dvorak, 51, was hired by United Airlines in 1986. He estimated that he had about 15,000 hours of total flying time. While working for United, he had accumulated 1,903 hours as a flight engineer in the
Boeing 727 The Boeing 727 is an American Narrow-body aircraft, narrow-body airliner that was developed and produced by Boeing Commercial Airplanes. After the heavier Boeing 707, 707 quad-jet was introduced in 1958, Boeing addressed the demand for shorter ...
and 33 hours as a flight engineer in the DC-10. Dennis E. Fitch, nicknamed "Denny", 46, was a training check pilot aboard Flight 232 as a passenger. He had studied the crash of
Japan Air Lines Flight 123 Japan Air Lines Flight 123 was a scheduled domestic passenger flight from Tokyo to Osaka, Japan. On August12, 1985, the Boeing 747 flying the route suffered a severe structural failure and explosive decompression 12 minutes after takeoff. After f ...
which suffered a total hydraulic system failure and loss of flight controls and had practiced similar situations in a flight simulator. He was hired by United in 1968 and he estimated that, prior to working for United, he had accrued at least 1,400 hours of flight time with the
Air National Guard The Air National Guard (ANG), also known as the Air Guard, is a Reserve components of the United States Armed Forces, federal military reserve force of the United States Air Force, as well as the air militia (United States), militia of each U.S. ...
, with a total flight time around 23,000 hours. His total DC-10 time with United was 2,987 hours, including 1,943 hours accrued as a flight engineer, 965 hours as a first officer, and 79 hours as a captain. Eight flight attendants were also aboard the flight.


Accident


Takeoff and engine failure

Flight 232 departed from
Stapleton International Airport Stapleton International Airport was a major airport in the western United States, and the primary airport of Denver, Colorado. It opened on October 17, 1929, and was replaced by the current Denver International Airport in 1995. It was a hub f ...
in
Denver Denver ( ) is a List of municipalities in Colorado#Consolidated city and county, consolidated city and county, the List of capitals in the United States, capital and List of municipalities in Colorado, most populous city of the U.S. state of ...
at 14:09
Central Daylight Time The North American Central Time Zone (CT) is a time zone in parts of Canada, the United States, Mexico, Central America, and a few Caribbean islands. In parts of that zone (20 states in the US, three provinces or territories in Canada, and ...
, en route to
O'Hare International Airport Chicago O'Hare International Airport is the primary international airport serving Chicago, Illinois, United States, located on the city's Northwest Side, approximately northwest of the Chicago Loop, Loop business district. The airport is ope ...
in
Chicago Chicago is the List of municipalities in Illinois, most populous city in the U.S. state of Illinois and in the Midwestern United States. With a population of 2,746,388, as of the 2020 United States census, 2020 census, it is the List of Unite ...
with continuing service to
Philadelphia Philadelphia ( ), colloquially referred to as Philly, is the List of municipalities in Pennsylvania, most populous city in the U.S. state of Pennsylvania and the List of United States cities by population, sixth-most populous city in the Unit ...
. At 15:16, while the airplane was making a slight right turn at its cruising altitude of , the
fan disk A fan disk is the central hub of a fan in a turbofan engine. Fan blades are attached to the fan disk, which is rotated by a shaft driven by a gas turbine. In modern passenger aircraft, most of the propulsive thrust comes from fans, which ...
of its tail-mounted
General Electric General Electric Company (GE) was an American Multinational corporation, multinational Conglomerate (company), conglomerate founded in 1892, incorporated in the New York (state), state of New York and headquartered in Boston. Over the year ...
CF6 engine disintegrated explosively. The uncontained failure resulted in the engine's fan disk departing the aircraft, tearing out components including parts of the No. 2 hydraulic system and supply hoses in the process; these were later found near
Alta, Iowa Alta is a city in Buena Vista County, Iowa, United States. The population was 2,087 at the 2020 census. History Alta was platted in 1872, and it was incorporated in 1878. By 1882, Alta contained three general stores, two drug stores, two groc ...
. Engine debris penetrated the aircraft's tail section in numerous places, including the
horizontal stabilizer A tailplane, also known as a horizontal stabilizer, is a small lifting surface located on the tail ( empennage) behind the main lifting surfaces of a fixed-wing aircraft as well as other non-fixed-wing aircraft such as helicopters and gyroplan ...
, severing the No. 1 and No. 3 hydraulic system lines where they passed through the horizontal stabilizer. The pilots felt a jolt, and the
autopilot An autopilot is a system used to control the path of a vehicle without requiring constant manual control by a human operator. Autopilots do not replace human operators. Instead, the autopilot assists the operator's control of the vehicle, allow ...
disengaged. As First Officer Records took hold of his control column, Captain Haynes concentrated on the tail engine, the instruments for which indicated it was malfunctioning; he found its throttle and fuel supply controls jammed. At Dvorak's suggestion, a valve for fuel to the tail engine was shut off. This part of the emergency took 14 seconds.


Attempts to control the plane

Meanwhile, Records found that the airplane did not respond to his
control column A yoke, alternatively known as a control wheel or a control column, is a device used for Pilot (aeronautics), piloting some fixed-wing aircraft.Crane, Dale: ''Dictionary of Aeronautical Terms, third edition'', page 563. Aviation Supplies ...
. Even with the control column turned all the way to the left, commanding maximum left
aileron An aileron (French for "little wing" or "fin") is a hinged flight control surface usually forming part of the trailing edge of each wing of a fixed-wing aircraft. Ailerons are used in pairs to control the aircraft in roll (or movement aroun ...
, and pulled all the way back, commanding maximum up
elevator An elevator (American English) or lift (Commonwealth English) is a machine that vertically transports people or freight between levels. They are typically powered by electric motors that drive traction cables and counterweight systems suc ...
inputs that would never be used together in normal flightthe aircraft was banking to the right with the nose dropping. Haynes attempted to level the aircraft with his own control column, then both Haynes and Records tried using their control columns together, but the aircraft still did not respond. Afraid the aircraft would roll into a completely inverted position (an unrecoverable situation), the crew reduced the left wing-mounted engine to idle and applied maximum power to the right engine. This caused the airplane to level slowly. While Haynes and Records performed the engine shutdown checklist for the failed engine, Dvorak observed that the gauges for fluid pressure and quantity in all three hydraulic systems were indicating zero. The loss of all hydraulic fluid meant that control surfaces were inoperative. The flight crew deployed the DC-10's air-driven generator in an attempt to restore hydraulic power by powering the auxiliary hydraulic pumps, but this was unsuccessful. The crew contacted United Airlines maintenance personnel via radio, but were told that the possibility of a total loss of hydraulics in a DC-10 was considered so remote that no procedure had been established for such an event. The airplane was tending to pull right and oscillated slowly vertically in a
phugoid In aviation, a phugoid or fugoid () is an aircraft motion in which the vehicle Aircraft principal axes, pitches up and climbs, and then pitches down and descends, accompanied by speeding up and slowing down as it goes "downhill" and "uphill". Th ...
cyclecharacteristic of planes in which control surface command is lost. With each iteration of the cycle, the aircraft lost about of altitude. Dennis Fitch, an experienced United Airlines
captain Captain is a title, an appellative for the commanding officer of a military unit; the supreme leader or highest rank officer of a navy ship, merchant ship, aeroplane, spacecraft, or other vessel; or the commander of a port, fire or police depa ...
and DC-10
flight instructor A flight instructor is a person who teaches others to operate aircraft. Specific privileges granted to holders of a flight instructor qualification vary from country to country, but very generally, a flight instructor serves to enhance or evaluate ...
, was among the passengers and volunteered to assist. The message was relayed by senior flight attendant Jan Brown Lohr to the flight crew, who invited Fitch into the cockpit; he began assisting at about 15:29. Haynes asked Fitch to observe the ailerons through the passenger cabin windows to see if control inputs were having any effect. Fitch reported that the ailerons were not moving at all. Nonetheless, the crew continued to manipulate their control columns for the remainder of the flight, hoping for at least some effect. Haynes then asked Fitch to take control of the throttles so that Haynes could concentrate on his control column. With one throttle in each hand, Fitch was able to mitigate the phugoid cycle and make rough steering adjustments.
Air traffic control Air traffic control (ATC) is a service provided by ground-based air traffic controllers who direct aircraft on the ground and through a given section of controlled airspace, and can provide advisory services to aircraft in non-controlled air ...
(ATC) was contacted and an emergency landing at nearby Sioux Gateway Airport was organized. The conversation was recorded by the airplane's
cockpit voice recorder A flight recorder is an electronic recording device placed in an aircraft for the purpose of facilitating the investigation of aviation accidents and incidents. The device may often be referred to colloquially as a "black box", an outdated nam ...
(CVR), including: : Sioux City Approach: "United Two Thirty-Two Heavy, the wind's currently three six zero at one one; three sixty at eleven. You're cleared to land on any runway." : Haynes: " aughter
Roger Roger is a masculine given name, and a surname. The given name is derived from the Old French personal names ' and '. These names are of Germanic languages">Germanic origin, derived from the elements ', ''χrōþi'' ("fame", "renown", "honour") ...
. aughterYou want to be particular and make it a runway, huh?" ATC asked the crew to make a left turn to keep them clear of the city: : Haynes: "Whatever you do, keep us away from the city." Haynes later noted, "We were too busy o be scared You must maintain your composure in the airplane, or you will die. You learn that from your first day flying."


Crash landing

As the crew began to prepare for arrival at Sioux Gateway Airport, they questioned whether they should deploy the landing gear or belly-land the aircraft with the gear retracted. They decided that having the landing gear down would provide some shock absorption on impact. The complete hydraulic failure left the landing gear lowering mechanism inoperative. Two options were available to the flight crew. The DC-10 is designed so that if hydraulic pressure to the landing gear is lost, the gear will fall down slightly and rest on the landing gear doors. Placing the regular landing gear handle in the down position will unlock the doors mechanically, and the doors and landing gear will then fall down into place and lock due to gravity. An alternative system is also available using a lever in the cockpit floor to cause the landing gear to fall into position. This lever has the added benefit of unlocking the outboard ailerons, which are not used in high-speed flight and are locked in a neutral position. The crew hoped that there might be some trapped hydraulic fluid in the outboard ailerons and that they might regain some use of flight controls by unlocking them. They elected to extend the gear with the alternative system. Although the gear deployed successfully, no change of the controllability of the aircraft resulted. Landing was originally planned for Runway 31. Difficulties in controlling the aircraft made alignment with the runway almost impossible. While dumping some of the excess fuel, the airplane executed a series of mostly right-hand turns (turning the airplane in this direction was easier) with the intention of aligning with Runway 31. When they finished they were instead aligned with the closed Runway 22, and had little ability to maneuver. Runway 22 had been closed permanently a year earlier. Fire trucks had been placed on Runway 22, anticipating a landing on nearby Runway 31, so all the vehicles were quickly moved out of the way before the airplane touched down. ATC also advised that a four-lane Interstate highway ran north and south just east of the airport, which they could land on if they did not think they could make the runway. Captain Haynes replied that they were passing over the interstate at that time and they would try for the runway instead. Fitch continued to control the aircraft's descent by adjusting engine thrust. With the loss of all hydraulics, the flaps could not be extended, and since flaps control both the minimum required forward speed and sink rate, the crew was unable to control either the airspeed or the sink rate. On final approach, the aircraft's forward speed was and it had a sink rate of , while a safe landing would require forward speed and sink rate. Moments before landing, the roll to the right suddenly worsened significantly and the aircraft began to pitch forward into a dive; Fitch realized this and pushed both throttles to full power in a desperate, last-ditch attempt to level the plane. It was now 16:00. The CVR recorded these final moments: : First Officer Records: "Close 'em off." : Captain Haynes: "Left turn, close 'em off." : First Officer Records: "Pull 'em all off." : Captain Fitch: "Nah, I can't pull 'em off or we'll lose it, that's what's turning ya." : First Officer Records: "Okay." : Captain Fitch: "Back, Al!" : Captain Haynes: "Left, left throttle, left, left, left, left, left, left, left, left, left, left, left!" :
Ground Proximity Warning System A Ground Proximity Warning System (GPWS) is a system designed to alert pilots if their aircraft is in immediate danger of flying into the ground or an obstacle. The United States Federal Aviation Administration (FAA) defines GPWS as a type of ...
: "Whoop whoop pull up. Whoop whoop pull up. Whoop whoop pull up." : Captain Haynes: "Everybody stay in brace!" : GPWS: "Whoop whoop pull up." : Captain Haynes: "God!" : ound of impact: End of recording. The engines were not able to respond to Fitch's controls in time to stop the roll, and the airplane struck the ground with its right wing, spilling fuel which ignited immediately. The tail section broke off from the force of the impact, and the rest of the aircraft bounced several times, shedding the landing gear and engine nacelles and breaking the fuselage into several main pieces. At final impact, the right wing was torn off and the main part of the aircraft skidded sideways, rolled over onto its back, and slid to a stop upside-down in a corn field to the right of Runway 22. Witnesses reported that the aircraft " cartwheeled" end-over-end, but the investigation did not confirm this. The reports were due to misinterpretation of the video of the crash that showed the flaming right wing tumbling end-over-end and the intact left wing, still attached to the fuselage, rolling up and over as the fuselage flipped over.


Injuries and deaths

Of the 296 people aboard, 112 died in the accident. Most were killed by injuries sustained during the multiple impacts, but 35 people in the middle fuselage section directly above the fuel tanks died from smoke inhalation in the post-crash fire. Of those, 24 had no traumatic blunt-force injuries. The majority of the 184 survivors were seated behind first class and ahead of the wings. Many passengers were able to walk out through the ruptures to the structure. Of all of the passengers: * 35 died because of smoke inhalation (none were in first class). * 76 died for reasons other than smoke inhalation (17 in first class). * One died a month after the crash. * 47 were injured seriously (eight in first class). * 125 had minor injuries (one in first class). * 13 had no injuries (none in first class). The passengers who died for reasons other than smoke inhalation were seated in rows 1–4, 24–25, and 28–38. Passengers who died because of smoke inhalation were seated in rows 14, 16, and 22–30. The person assigned to seat 20H moved to an unknown seat and died of smoke inhalation. One crash survivor died one month after the accident; he was classified according to NTSB regulations as a survivor with serious injuries. Fifty-two children, including four "lap children" without their own seats, were aboard the flight because of a United Airlines promotion for "Children's Day". Eleven children, including one lap child, died. Many of the children were traveling alone. Rescuers did not identify the debris that was the remains of the cockpit, with the four crew members alive inside, until 35 minutes after the crash. All four recovered from their injuries and eventually returned to flight duty.


Investigation

The rear engine's fan disk and blade assemblyabout acrosscould not be located at the accident scene despite an extensive search. The engine's manufacturer, General Electric, offered rewards of $50,000 for the disk and $1,000 for each fan blade. Three months after the crash, a farmer discovered most of the fan disk, with several blades still attached, in her cornfield, thereby qualifying her for a reward, as a General Electric lawyer confirmed. The rest of the fan disk and most of the additional blades were later found nearby. The NTSB determined that the probable cause of this accident was the inadequate consideration given to human factors, and limitations of the inspection and quality control procedures used by United Airlines' engine overhaul facility. These resulted in the failure to detect a fatigue crack originating from a previously undetected metallurgical defect located in a critical area of the
titanium Titanium is a chemical element; it has symbol Ti and atomic number 22. Found in nature only as an oxide, it can be reduced to produce a lustrous transition metal with a silver color, low density, and high strength, resistant to corrosion in ...
-alloy stage-1 fan disk that was manufactured by General Electric Aircraft Engines. The uncontained manner in which the engine failed resulted in high-speed metal fragments being hurled from the engine; these fragments penetrated the hydraulic lines of all three
independent Independent or Independents may refer to: Arts, entertainment, and media Artist groups * Independents (artist group), a group of modernist painters based in Pennsylvania, United States * Independentes (English: Independents), a Portuguese artist ...
hydraulic systems aboard the aircraft, which rapidly lost their hydraulic fluid. 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; the flight crew lost its ability to operate nearly all of them. Despite these losses, the crew was able to attain and then maintain limited control by using the throttles to adjust thrust from the remaining wing-mounted engines. By using 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 aligned it for landing on one of the runways. Without the use of flaps and slats, they were unable to slow for landing, and were forced to attempt landing at a very high ground speed. The aircraft also landed at an extremely high rate of descent because of the inability to flare (reduce the rate of descent before touchdown 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, 184 (62.2%) 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.


Failed component

The investigation, while praising the actions of the flight crew for saving lives, later identified the cause of the accident as a failure by United Airlines maintenance processes and personnel to detect an existing fatigue crack. The Probable Cause in the report by the NTSB read as follows: Post-crash analysis of the crack surfaces showed the presence of a penetrating fluorescent dye used to detect cracks during maintenance. The presence of the dye indicated that the crack was present and should have been detected at a prior inspection. The detection failure arose from poor attention to human factors in United Airlines' specification of maintenance processes. Investigators discovered an impurity and
fatigue Fatigue is a state of tiredness (which is not sleepiness), exhaustion or loss of energy. It is a signs and symptoms, symptom of any of various diseases; it is not a disease in itself. Fatigue (in the medical sense) is sometimes associated wit ...
crack in the disk. Titanium reacts with air when melted, which creates impurities that can initiate fatigue cracks like that found in the crash disk. To prevent this, the ingot that would become the fan disk was formed using a "double vacuum" process: the raw materials were melted together in a
vacuum A vacuum (: vacuums or vacua) is space devoid of matter. The word is derived from the Latin adjective (neuter ) meaning "vacant" or "void". An approximation to such vacuum is a region with a gaseous pressure much less than atmospheric pressur ...
, allowed to cool and solidify, then melted in a vacuum once more. After the double vacuum process, the ingot was shaped into a
billet In European militaries, a billet is a living-quarters to which a soldier is assigned to sleep. In American usage, it refers to a specific personnel position, assignment, or duty station to which a soldier can be assigned. Historically, a billet w ...
, a sausage-like form about 16 inches in diameter, and tested using ultrasound to look for defects. Defects were located and the ingot was processed further to remove them, but some nitrogen contamination remained. GE later added a third vacuum-forming stage because of their investigation into failing rotating titanium engine parts. The contamination caused what is known as a hard alpha inclusion, where a contaminant particle in a metal alloy causes the metal around it to become brittle. The brittle titanium around the impurity then cracked during forging and fell out during final machining, leaving a cavity with microscopic cracks at the edges. For the next 18 years, the crack grew slightly each time the engine was powered up and brought to
operating temperature An operating temperature is the allowable temperature range of the local ambient environment at which an electrical or mechanical device operates. The device will operate effectively within a specified temperature range which varies based on the de ...
. Eventually, the crack broke open, causing the disk to fail. The origins of the crash disk are uncertain because of significant irregularities and gaps, noted in the NTSB report, in the manufacturing records of GE Aircraft Engines (GEAE) and its suppliers. Records found after the accident indicated that two rough-machined forgings having the serial number of the crash disk had been routed through GEAE manufacturing. Records indicated that
Alcoa Alcoa Corporation (an acronym for "Aluminum Company of America") is an American industrial corporation. It is the world's eighth-largest producer of aluminum. Alcoa conducts operations in 10 countries. Alcoa is a major producer of primary alu ...
supplied GE with
TIMET Titanium Metals Corporation, or most commonly referred to as TIMET, a shortened version of "TItanium METals" that is a registered company trademark. TIMET, founded in 1950, is an American manufacturer of titanium-based metals products, focusing ...
titanium forgings for one disk with the serial number of the crash disk. Some records show that this disk "was rejected for an unsatisfactory ultrasonic indication", that an outside laboratory performed an ultrasound inspection of this disk, that this disk was subsequently returned to GE, and that this disk should have been scrapped. The FAA report stated, "There is no record of warranty claim by GEAE for defective material and no record of any credit for GEAE processed by Alcoa or TIMET". GE records of the second disk having the serial number of the crash disk indicate that it was made with an RMI Titanium Company titanium billet supplied by Alcoa. Research of GE's records showed no other titanium parts were manufactured at GE from this RMI titanium billet during the period of 1969 to 1990. GE records indicate that final finishing and inspection of the crash disk were completed on December 11, 1971. Alcoa records indicate that this RMI titanium billet was first cut in 1972 and that all forgings made from this material were for airframe parts. If the Alcoa records were accurate, the RMI titanium could not have been used to manufacture the crash disk, indicating that the initially rejected TIMET disk with "an unsatisfactory ultrasonic indication" was the crash disk. CF6 engines like the one containing the crash disk were used to power many civilian and military aircraft at the time of the crash. Due to concerns that the accident could reoccur, a large number of in-service disks were examined by ultrasound for indications of defects. The fan disks on at least two other engines were found to have defects like that of the crash disk. Prioritization and efficiency of inspections of the many engines suspected would have been aided by determination of the titanium source of the crash disk. Chemical analyses of the crash disk intended to determine its source were inconclusive. The NTSB report stated that if examined disks were not from the same source, "the records on a large number of GEAE disks are suspect. It also means that any AD ( Airworthiness Directive) action that is based on the serial number of a disk could fail to have its intended effect because suspect disks could remain in service."


Influence on the industry

The NTSB investigation, after reconstructions of the accident in
flight simulator A flight simulator is a device that artificially re-creates aircraft flight and the environment in which it flies, for pilot training, design, or other purposes. It includes replicating the equations that govern how aircraft fly, how they rea ...
s, deemed that training for such an event involved too many factors to be practical. While some degree of control was possible, no precision could be achieved, and a landing with these conditions was stated to be "a highly random event". Expert United and McDonnell Douglas pilots were unable to reproduce a survivable landing; according to a United pilot who flew with Fitch, "Most of the simulations never even made it close to the ground". The NTSB stated that "under the circumstances the UAL (United Airlines) flight crew performance was highly commendable and greatly exceeded reasonable expectations." At the time of the crash, McDonnell Douglas had ended production of DC-10's, with the last of these being delivered to Nigeria Airways during the summer of 1989. The last passenger version of the DC-10 flew in 2014, although freighter versions continued to operate until late 2022. Because this type of aircraft control (with loss of control surfaces) is difficult for humans to achieve, some researchers have attempted to integrate this control ability into the computers of
fly-by-wire Fly-by-wire (FBW) is a system that replaces the conventional aircraft flight control system#Hydro-mechanical, manual flight controls of an aircraft with an electronic interface. The movements of flight controls are converted to electronic sig ...
aircraft. Early attempts to add the ability to real airplanes were not very successful; the software was based on experiments performed in flight simulators where jet engines are usually modeled as "perfect" devices with exactly the same thrust on each engine, a
linear relationship In statistics, correlation or dependence is any statistical relationship, whether causal or not, between two random variables or bivariate data. Although in the broadest sense, "correlation" may indicate any type of association, in statistics ...
between throttle setting and thrust, and instantaneous response to input. Later, computer models were updated to account for these
nonlinear In mathematics and science, a nonlinear system (or a non-linear system) is a system in which the change of the output is not proportional to the change of the input. Nonlinear problems are of interest to engineers, biologists, physicists, mathe ...
factors, and aircraft such as the F-15 STOL/MTD have been flown successfully with this software installed.


Titanium processing

The manufacturing process for titanium was changed to eliminate the type of gaseous anomaly that served as the starting point for the crack. Newer batches of titanium use much higher melting temperatures and a "triple vacuum" process in an attempt to eliminate such impurities (triple melt VAR).


Aircraft designs

Newer designs such as the
McDonnell Douglas MD-11 The McDonnell Douglas MD-11 is an American trijet wide-body aircraft, wide-body airliner manufactured by American manufacturer McDonnell Douglas (MDC) and later by Boeing. Following McDonnell Douglas DC-10, DC-10 development studies, the MD-11 ...
have incorporated hydraulic fuses to isolate a punctured section and prevent a total loss of hydraulic fluid. After the United 232 accident, such fuses were installed in the number three hydraulic system in the area below the number two engine on all DC-10 aircraft to ensure sufficient control capability remained if all three hydraulic system lines should be damaged in the tail area. Although elevator and rudder control would be lost, the aircrew would still be able to control the aircraft's pitch (up and down) with stabilizer trim, and would be able to control roll (left and right) with some of the aircraft's
aileron An aileron (French for "little wing" or "fin") is a hinged flight control surface usually forming part of the trailing edge of each wing of a fixed-wing aircraft. Ailerons are used in pairs to control the aircraft in roll (or movement aroun ...
s and spoilers. Although not ideal, the system provides a greater control than that available to the United 232. Losing all three hydraulic systems remained possible if serious damage occurs elsewhere, as nearly happened to a cargo DC-10-40F in April 2002 during takeoff in San Salvador when a main-gear tire exploded after running over a lost thrust reverser cascade. The extensive damage in the left wing caused total loss of pressure from the number-one and the number-two hydraulic systems. The number-three system was dented but not penetrated. NTSB then recommended that FAA "Require adequate protection of DC-10 hydraulic system components in the wing area from tire fragments" by better shielding or adding fuses in this area.


Restraints for children

Of the four children deemed too young to require seats of their own ("lap children"), one died from smoke inhalation. The NTSB added a safety recommendation to the FAA on its "List of Most Wanted Safety Improvements" in May 1999 suggesting a requirement for children younger than two years old to be restrained safely, which was removed in November 2006. The accident began a campaign directed by United Flight 232's senior flight attendant, Jan Brown Lohr, for all children to have seats on aircraft. The argument against requiring seats on aircraft for children younger than age two is the higher cost to a family of having to buy a seat for the child, and this higher cost will motivate more families to drive instead of fly, and incur the much greater risk of driving (see Epidemiology of motor vehicle collisions). The FAA estimates that a regulation that all children must have a seat would equate, for every one child's life saved on an aircraft, to 60 people dying in highway accidents. Though it is no longer on the "most wanted" list, providing aircraft restraints for children younger than age two is still recommended practice by the NTSB and FAA, though it is not required by the FAA as of May 2016. The NTSB asked the
International Civil Aviation Organization The International Civil Aviation Organization (ICAO ) is a specialized agency of the United Nations that coordinates the principles and techniques of international air navigation, and fosters the planning and development of international sch ...
to make this a requirement in September 2013.


Crew resource management

The accident has since become an example of successful crew resource management (CRM). For much of aviation's history, the captain was considered the final authority, and crews were expected to respect the captain's expertise without question. This began to change during the 1970s, especially after the
Tenerife airport disaster The Tenerife airport disaster occurred on 27 March 1977, when two Boeing 747 passenger jets collided on the runway at Tenerife North–Ciudad de La Laguna Airport, Los Rodeos Airport (now Tenerife North–Ciudad de La Laguna Airport) on the Spa ...
in 1977 and the crash of United Airlines Flight 173 outside
Portland, Oregon Portland ( ) is the List of cities in Oregon, most populous city in the U.S. state of Oregon, located in the Pacific Northwest region. Situated close to northwest Oregon at the confluence of the Willamette River, Willamette and Columbia River, ...
in 1978. CRM, while still considering the captain as final authority, instructs crew members to speak up when they detect a problem, and instructs captains to listen to crew concerns. United Airlines instituted a CRM class during the early 1980s. The NTSB later credited this training as valuable for the success of United 232's crew in handling their emergency. The FAA made CRM mandatory after the accident.


Factors contributing to survival rate

Of the 296 people aboard, 112 were killed and 184 survived. Haynes later identified three factors relating to the time of day that increased the survival rate: # The accident occurred during daylight hours in good weather; # The accident 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; # The accident occurred when the Iowa Air National Guard was on duty at Sioux Gateway Airport, allowing for 285 trained personnel to assist with
triage In medicine, triage (, ; ) is a process by which care providers such as Health professional, medical professionals and those with first aid knowledge determine the order of priority for providing treatment to injured individuals and/or inform th ...
and evacuation of the injured. "Had any of those things not been there," Haynes said, "I'm sure the fatality rate would have been a lot higher." Haynes also credited CRM as being one of the factors that saved his own life, and many others. When Haynes died in August 2019, United Airlines issued a statement thanking him for "his exceptional efforts aboard Flight UA232". As with the
Eastern Air Lines Flight 401 Eastern Air Lines Flight 401 was a scheduled flight from John F. Kennedy International Airport in Queens, New York, United States, to Miami International Airport in Miami, Florida, United States. Shortly before midnight on December 29, 1972, the ...
crash of a similarly sized
Lockheed L-1011 The Lockheed L-1011 TriStar (pronounced "El-ten-eleven") is an American medium-to-long-range, wide-body trijet airliner built by the Lockheed Corporation. It was the third wide-body airliner to enter commercial operations, after the Boeing 74 ...
in 1972, the relatively shallow angle of descent likely played a large part in the relatively high survival rate.
Copy at
Embry–Riddle Aeronautical University Embry-Riddle Aeronautical University (ERAU) is a private university focused on aviation and aerospace programs based in Daytona Beach, Florida, and Prescott, Arizona, United States. It is the largest accredited university system specializing in ...
.
The National Transportation Safety Board concluded that under the circumstances, "a safe landing was virtually impossible".


Notable people onboard


Victims

* John Kenneth Stille – chemist * Jay Ramsdell – commissioner of the
Continental Basketball Association The Continental Basketball Association (CBA), originally known as the Eastern Pennsylvania Basketball League, and later as the Eastern Professional Basketball League and the Eastern Basketball Association, was a men's professional basketball m ...


Survivors

* Spencer Bailey – writer, editor, and journalist * Al Haynes – captain of UA232 * Helen Young Hayes – investment fund manager * Michael R. Matz – Olympian and racehorse trainer * Jerry Schemmel – Radio broadcaster for the Colorado Rockies (Formerly for the Denver Nuggets) * Pete Wernick – banjo player and member of American bluegrass ensemble Hot Rize, who managed to resume performing two days after the crash


Depictions

* The accident was the subject of an 11th-season episode of the documentary series ''
Mayday Mayday is an emergency procedure word used internationally as a distress signal in voice-procedure radio communications. It is used to signal a life-threatening emergency primarily by aviators and mariners, but in some countries local organiz ...
'' (also known as ''Air Crash Investigation''), titled "Impossible Landing". The episode featured interviews with survivors and showed actual footage of the crash. * The accident was the subject of the 1992
television movie A television film, alternatively known as a television movie, made-for-TV film/movie, telefilm, telemovie or TV film/movie, is a film with a running time similar to a feature film that is produced and originally distributed by or to a Terrestr ...
'' A Thousand Heroes'', also known as ''Crash Landing: The Rescue of Flight 232''. *The episode "Engineering Disasters" (season 6, episode 18) of ''
Modern Marvels ''Modern Marvels'', formally known under A&E as ''Time Machine'', is a television series first aired by the History Channel in 1995, but previously under A&E starting December 10, 1993. It is the History Channel's first and longest-running prog ...
'' featured the crash. * The accident was featured in an episode of ''
Seconds from Disaster ''Seconds from Disaster'' is a US/UK-produced documentary television programme that investigates historically relevant man-made and natural disasters from the 20th and early 21st centuries. Each episode aims to explain a single incident by anal ...
'' (S2E7 9/13/05 "Crash Landing in/at Sioux City") on the
National Geographic Channel National Geographic (formerly National Geographic Channel; abbreviated and trademarked as Nat Geo or Nat Geo TV) is an American pay television network and flagship channel owned by the National Geographic Global Networks unit of Disney Enter ...
and '' MSNBC Investigates'' on the
MSNBC MSNBC is an American cable news channel owned by the NBCUniversal News Group division of NBCUniversal, a subsidiary of Comcast. Launched on July 15, 1996, and headquartered at 30 Rockefeller Plaza in Manhattan, the channel primarily broadcasts r ...
news channel. *
The History Channel History (formerly and commonly known as the History Channel) is an American pay television network and the flagship channel of A&E Networks, a joint venture between Hearst Communications and the General Entertainment Content division of The Wa ...
distributed a documentary named ''
Shockwave In physics, a shock wave (also spelled shockwave), or shock, is a type of propagating disturbance that moves faster than the local speed of sound in the medium. Like an ordinary wave, a shock wave carries energy and can propagate through a me ...
''; a portion of Episode 7 (originally aired January 25, 2008) detailed the events of the crash. * The episode " A Wing and a Prayer" of '' Survival in the Sky'' (UK title: ''Black Box'') featured the accident. * The
Biography Channel FYI (stylized as fyi,) is an American basic cable channel owned by A&E Networks, a joint venture between the Disney Entertainment subsidiary of The Walt Disney Company and Hearst Communications (each owns 50%). The network features lifestyle pro ...
series '' I Survived...'' explained in detail the events of the crash through passenger Jerry Schemmel, flight attendant Jan Brown Lohr, and pilot Alfred Haynes. * The episode "Crisis in the Cockpit" (Season 2, Episode 1) of '' Why Planes Crash'' on
The Weather Channel The Weather Channel (TWC) is an American pay television television channel, channel owned by Weather Group, LLC, a subsidiary of Allen Media Group. The channel's headquarters are located in Atlanta, Georgia. Launched on May 2, 1982, the channel ...
featured the accident. * The 1999 play '' Charlie Victor Romeo'' (made into a film in 2013) dramatically reenacted the incident using transcripts from the cockpit voice recorder (CVR). * The 1991 novel '' Cold Fire'', by
Dean Koontz Dean Ray Koontz (born July 9, 1945) is an American author. His novels are billed as thriller (genre), suspense thrillers, but frequently incorporate elements of horror fiction, horror, fantasy, science fiction, Mystery fiction, mystery, and sati ...
, includes a fictional crash based on Flight 232. * The 1993 film '' Fearless'' portrayed a fictional plane crash based in part on the crash of Flight 232. * In 2016, The House Theatre of Chicago produced ''United Flight 232''. The play was a new work directed and adapted by Vanessa Stalling and based on the book ''Flight 232'' by Laurence Gonzales. Surviving crew members attended the play in April 2016, and the production was subsequently nominated for six Equity Jeff Awards, winning two. * In 2021, the accident was covered in episode 5 of the UK TV series ''Plane Crash Recreated''.


Survivor accounts

* Dennis Fitch described his experiences in
Errol Morris Errol Mark Morris (born February 5, 1948) is an American film director known for documentaries that interrogate the epistemology of their subjects, and the invention of the Interrotron. In 2003, his '' The Fog of War: Eleven Lessons from the Li ...
's television show '' First Person'', episode "Leaving the Earth". * Martha Conant told her story of survival to her daughter-in-law, Brittany Conant, on "
Storycorps StoryCorps is an American non-profit organization which aims to record, preserve, and share the stories of Americans from all backgrounds and beliefs. Its mission statement is "to help us believe in each other by illuminating the humanity and po ...
" during
NPR National Public Radio (NPR) is an American public broadcasting organization headquartered in Washington, D.C., with its NPR West headquarters in Culver City, California. It serves as a national Radio syndication, syndicator to a network of more ...
's ''
Morning Edition ''Morning Edition'' is an American radio news program produced and distributed by NPR. It airs weekday mornings (Monday through Friday) and runs for two hours, and many stations repeat one or both hours. The show feeds live from 5:00 to 9:00 a ...
'' of January 11, 2008. * ''Flight 232: A Story of Disaster and Survival'' by Laurence Gonzales (2014, W. W. Norton & Company; ). * ''Miracle in the Cornfield'' – an inside survivor narrative by Joseph Trombello (1999, PrintSource Plus, Appleton, WI; ). * ''When the World Breaks Your Heart: Spiritual Ways of Living With Tragedy'' by Gregory S. Clapper, a chaplain in the National Guard who relates the stories of some of the survivors he aided in the aftermath of the crash (1999; 2016, Wipf and Stock; ). * ''Chosen to Live: The Inspiring Story of Flight 232 Survivor Jerry Schemmel'' by Jerry Schemmel with Kevin Simpson (Victory Pub. Co.,1996; ). * Spencer Bailey discussed his experiences on the Time Sensitive podcast, in a 2019 interview with
Andrew Zuckerman Andrew Zuckerman (born 1977) is an American filmmaker and photographer. He is best known for creating hyper-real images set against stark white backgrounds. His subjects have included birds, endangered species of animals, politicians, humanitaria ...
.


Flight 232 Memorial

The Flight 232 Memorial was built along the Missouri River in Sioux City, Iowa, to commemorate the heroism of the flight crew and the rescue efforts the Sioux City community undertook after the crash. It features a statue of Iowa National Guard Lt. Col. Dennis Nielsen from a news photo that was taken that day while he was carrying a three-year-old to safety.


Similar accidents

The odds against all three hydraulic systems failing simultaneously had previously been calculated as low as a billion to one. Yet such calculations assume that multiple failures must have independent causes, an unrealistic assumption, and similar flight control failures have indeed occurred: * In 1971, a Boeing 747, operating as Pan Am 845, struck approach light structures for the reciprocal runway as it lifted off the runway at San Francisco Airport. Major damage to the belly and landing gear resulted, which caused the loss of hydraulic fluid from three of its four flight control systems. The fluid which remained in the fourth system gave the captain very limited control of some of the spoilers, ailerons, and one inboard elevator. That was sufficient to circle the plane while fuel was dumped and then to make a hard landing. There were no fatalities, but there were some injuries.
Copy at
Embry–Riddle Aeronautical University Embry-Riddle Aeronautical University (ERAU) is a private university focused on aviation and aerospace programs based in Daytona Beach, Florida, and Prescott, Arizona, United States. It is the largest accredited university system specializing in ...
.
* In 1981, a
Lockheed L-1011 The Lockheed L-1011 TriStar (pronounced "El-ten-eleven") is an American medium-to-long-range, wide-body trijet airliner built by the Lockheed Corporation. It was the third wide-body airliner to enter commercial operations, after the Boeing 74 ...
, operating as Eastern Air Lines Flight 935, suffered a similar failure of its tail-mounted number two engine. The shrapnel from that engine inflicted damage on all four of its hydraulic systems, which were also close together in the tail structure. Fluid was lost in three of the four systems. The fourth hydraulic system was struck by shrapnel, but not punctured. The hydraulic pressure remaining in that fourth system enabled the captain to land the plane safely with some limited use of the outboard spoilers, the inboard ailerons, and the horizontal stabilizer, plus differential engine power of the remaining two engines. There were no injuries. * In 1985,
Japan Air Lines Flight 123 Japan Air Lines Flight 123 was a scheduled domestic passenger flight from Tokyo to Osaka, Japan. On August12, 1985, the Boeing 747 flying the route suffered a severe structural failure and explosive decompression 12 minutes after takeoff. After f ...
, a Boeing 747-146SR, suffered a rupture of the pressure bulkhead in its tail section, caused by undetected damage during a faulty repair to the rear bulkhead after a tailstrike seven years earlier. Pressurized air subsequently rushed out of the bulkhead and blew off the plane's vertical stabilizer, also severing all four of its hydraulic control systems. The pilots were able to keep the plane airborne for 32 minutes using differential engine power, but without any hydraulics or the stabilizing force of the vertical stabilizer, the plane eventually crashed in mountainous terrain. There were only 4 survivors among the 524 on board. This accident is the deadliest single-aircraft accident in history. * In 1994, RA85656, a
Tupolev Tu-154 The Tupolev Tu-154 (; NATO reporting name: "Careless") is a three-engined, medium-range, narrow-body airliner designed in the mid-1960s and manufactured by Tupolev. A workhorse of Soviet and (subsequently) Russian airlines for several decades, ...
operating as Baikal Airlines Flight 130, crashed near
Irkutsk Irkutsk ( ; rus, Иркутск, p=ɪrˈkutsk; Buryat language, Buryat and , ''Erhüü'', ) is the largest city and administrative center of Irkutsk Oblast, Russia. With a population of 587,891 Irkutsk is the List of cities and towns in Russ ...
shortly after departing from Irkutsk Airport, Russia. Damage to the starter caused a fire in engine number two (located in the rear fuselage). High temperatures during the fire destroyed the tanks and pipes of all three hydraulic systems. The crew lost control of the aircraft. The out-of-control plane, at a speed of 275 knots, hit the ground at a dairy farm and burned. All 124 passengers and crew, as well as a dairyman on the ground, died. * In 2003, OO-DLL, a DHL Airbus A300, was struck by a surface-to-air missile shortly after departing from
Baghdad International Airport Baghdad International Airport , previously Saddam International Airport from 1982 to 2003, () is Iraq's largest international airport, located in a suburb about west of downtown Baghdad in the Baghdad Governorate. It is the home base for Ira ...
, Iraq. The missile struck the port-side wing, rupturing a fuel tank and causing the loss of all three hydraulic systems. With the flight controls disabled, the crew used differential thrust to execute a safe landing at Baghdad. * In 2024, an Embraer 190, operating as Azerbaijan Airlines Flight 8243, was hit by a Russian anti-air system, rupturing all three hydraulic lines, rendering the plane inoperable. After diverting from the original destination of Grozny, Russia, the pilots decided to cross the Caspian Sea to attempt a landing in
Kazakhstan Kazakhstan, officially the Republic of Kazakhstan, is a landlocked country primarily in Central Asia, with a European Kazakhstan, small portion in Eastern Europe. It borders Russia to the Kazakhstan–Russia border, north and west, China to th ...
. The pilots flew for more than 70 minutes with no control surfaces before crashing on a third attempt to land at Aktau International Airport. Of the 67 people onboard, 38 died, including three out of five crewmembers. The disintegration of a turbine disc, leading to loss of control, was a direct cause of two major aircraft disasters in Poland: * On March 14, 1980, LOT Polish Airlines Flight 007, an
Ilyushin Il-62 The Ilyushin Il-62 (; NATO reporting name: Classic) is a Soviet Union, Soviet long-range Narrow-body aircraft, narrow-body jetliner conceived in 1960 by Ilyushin. As a successor to the popular turboprop Ilyushin Il-18, Il-18 and with capacit ...
, attempted a
go-around In aviation, a go-around is an aborted landing of an aircraft that is on Final_approach_(aeronautics), final approach or has already touched down. A go-around can either be initiated by the pilot flying or requested by air traffic control for var ...
when the crew experienced troubles with a gear indicator. When thrust was applied, the low-pressure turbine disc in engine number 2 disintegrated because of material fatigue; parts of the disc damaged engines number 1 and 3 and severed control pushers for both horizontal and vertical stabilizers. After 26 seconds of uncontrolled descent, the aircraft crashed, killing all 87 people on board. * On May 9, 1987, improperly assembled bearings in Il-62M engine number 2 on LOT Polish Airlines Flight 5055 overheated and exploded during cruise over the village of Lipinki, causing the shaft to break in two; this caused the low-pressure turbine disc to spin to enormous speeds and disintegrate, damaging engine number 1 and cutting the control pushers. The crew managed to return to Warsaw, using nothing but
trim tabs Trim tabs are small surfaces connected to the trailing edge of a larger control surface on a boat or aircraft, used to control the trim of the controls, i.e. to counteract hydro- or aerodynamic forces and stabilise the boat or aircraft in a pa ...
to control the crippled aircraft, but on the final approach, the trim controlling links burned and the crew completely lost control over the aircraft. Soon after, it crashed on the outskirts of Warsaw; all 183 on board died. Had the plane stayed airborne for 40 seconds more, it would have been able to reach the runway. In contrast to deploying landing gear: * On August 15, 2019, Ural Airlines Flight 178, an
Airbus A321 The Airbus A321 is a member of the Airbus A320 family of short to medium range, Narrow-body aircraft, narrow-body, commercial passenger Twinjet, twin engine jet airliners; it carries 185 to 236 passengers. It has a stretched fuselage which was ...
, encountered a flock of seagulls resulting in a
bird strike A bird strike (sometimes called birdstrike, bird ingestion (for an engine), bird hit, or bird aircraft strike hazard (BASH)) is a collision between an airborne animal (usually a bird or bat) and a moving vehicle (usually an aircraft). The term ...
that caused fires in both
CFM56-5 The CFM International CFM56 (U.S. military designation F108) series is a Franco-American family of high-bypass turbofan aircraft engines made by CFM International (CFMI), with a thrust range of . CFMI is a 50–50 joint-owned company of Safra ...
engines just after takeoff from
Zhukovsky International Airport Zhukovsky (), formerly (and still occasionally) known as Ramenskoye () is an international airport, located in Moscow Oblast, Russia, southeast of central Moscow, in the city of Zhukovsky, a few kilometers south-east of the closed Bykovo Airp ...
,
Moscow Moscow is the Capital city, capital and List of cities and towns in Russia by population, largest city of Russia, standing on the Moskva (river), Moskva River in Central Russia. It has a population estimated at over 13 million residents with ...
, Russia. Due to a failure to follow standard operating procedures, the plane was forced to land in a corn field with the
landing gear Landing gear is the undercarriage of an aircraft or spacecraft that is used for taxiing, takeoff or landing. For aircraft, it is generally needed for all three of these. It was also formerly called ''alighting gear'' by some manufacturers, s ...
raised. The pilots claimed they intentionally landed with the landing gear up, though the CVR recording revealed no discussion about this. Everyone on board the flight survived. 74 people were injured, none severely.


See also

* List of aircraft accidents and incidents resulting in at least 50 fatalities * Miracle on the Hudson


Notes


References


External links

*
NTSB Accident report of United Airlines Flight 232

Alternate link
at Embry-Riddle Aeronautical University
Cockpit voice-recorder transcript (pdf) (NB contains error)


* * ttp://www.siouxlandchamber.com/blog/remembering-flight-232/ Siouxland Chamber Of Commerce: Remembering Flight 232 (Picture of memorial depicting Lt. Colonel Dennis Nielsen carrying Spencer Bailey)
"17th Anniversary Tribute of Flight 232"

News report with video of crash landing of Flight 232
ABC News ABC News most commonly refers to: * ABC News (Australia), a national news service of the Australian Broadcasting Corporation * ABC News (United States), a news-gathering and broadcasting division of the American Broadcasting Company ABC News may a ...
, July 19, 1989
Pre-crash photos
from Airliners.net
Martha Conant tells her story of surviving the crash
* – 1992 TV movie
Errol Morris' First Person (one hour documentary video, accident recounting by Denny Fitch)
* * * {{DEFAULTSORT:United Airlines Flight 0232 Aviation accidents and incidents in the United States in 1989 1989 in Iowa Airliner accidents and incidents in Iowa Airliner accidents and incidents caused by mechanical failure Airliner accidents and incidents caused by engine failure Sioux City, Iowa
232 Year 232 ( CCXXXII) was a leap year starting on Sunday of the Julian calendar. At the time, it was known as the Year of the Consulship of Lupus and Maximus (or, less frequently, year 985 ''Ab urbe condita''). The denomination 232 for this year ...
Accidents and incidents involving the McDonnell Douglas DC-10 July 1989 in the United States Airliner accidents and incidents involving uncontained engine failure Aviation accidents and incidents caused by loss of control Aviation accidents and incidents in 1989 Filmed deaths during aviation accidents and incidents