United Airlines Flight 232
On 19 July 1989 United Airlines Flight 232, a DC-10 flying from Denver to Chicago and Philadelphia, lost all three hydraulic systems when its tail engine's fan disk shattered at 37,000 feet. The crew steered it to Sioux City, Iowa, using only the two remaining engines, and 184 of the 296 people on board survived the crash landing.
The sequence of events
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Watch this moment · 2:28
Departure from Denver
Flight 232 left Denver's Stapleton airport for Chicago and Philadelphia. The climb to 37,000 feet was normal, with the first officer flying on autopilot.
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15:16:10 CDT
The tail engine fails
The crew heard a loud bang, followed by vibration. The No. 2 engine, in the tail, had failed, and the second officer saw that hydraulic pressure and quantity in all three systems had fallen to zero.
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15:20 CDT
Emergency declared
With the aircraft turning to the right and not responding to the controls, the crew radioed Minneapolis Center for emergency help and vectors to the nearest airport.
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15:22 CDT
Heading for Sioux City
The controller said the aircraft was heading towards Sioux City and asked if the crew would prefer to go there. They said yes.
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15:29 CDTapproximately
An extra pilot in the cockpit
An off-duty United DC-10 training check airman travelling as a passenger came to the cockpit, looked at the wings from the cabin, and then took over the throttles so the pilots could work the control columns.
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Watch this moment · 19:56
15:49 CDTapproximately
The landing gear goes down
About 11 minutes before landing, the crew lowered the gear using the alternate extension procedure. They saw the airport from about 9 miles out, lined up with runway 22, which was closed.
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Watch this moment · 5:55
The crash landing
Descending fast at about 215 knots, the aircraft's right wing dropped just before touchdown. The right wingtip hit first and the DC-10 broke up and burned, with the centre section coming to rest in a cornfield.
Key facts
| Aircraft | McDonnell Douglas DC-10 |
|---|---|
| Aircraft variant | McDonnell Douglas DC-10-10, N1819U |
| Flight number | 232 |
| People who died | 112 |
| People on board | 296 |
| Were there survivors? | Yes |
| Phase of flight | Cruise |
Official finding · National Transportation Safety Board (NTSB)
inadequate consideration of human factors limitations in the inspection and quality control procedures at United Airlines' engine overhaul facility, so a fatigue crack from an undetected metallurgical defect in the stage 1 fan disk was not found; the disintegrating disk's debris exceeded the protection designed into the DC-10's hydraulic systems.
More coverage
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Fascinating Horror
United Airlines Flight 232: The Crash Landing at Sioux City, 1989
Questions and answers
What caused United Airlines Flight 232 to crash?
A fatigue crack in the stage 1 fan disk of the tail engine grew from a defect in the titanium that dated from the disk's manufacture. The disk broke apart in flight, and the debris cut the lines of all three hydraulic systems. The NTSB found that United's engine overhaul inspections had not detected the crack because human factors limits in the inspection process were not properly considered.
How did the crew steer the DC-10 without hydraulics?
With no working flight controls, the crew used the throttles of the two wing engines. More power on one side turned the aircraft, and changing power on both moved the nose up or down. An off-duty training captain, Dennis Fitch, handled the throttles while Captain Al Haynes and First Officer William Records worked the control columns.
How many people survived United 232?
184 of the 296 people on board survived. 111 were killed in the crash and one more passenger died of his injuries 31 days later, so 112 people died in all.
Why did so many people survive?
The NTSB found that the crew's performance was highly commendable and greatly exceeded reasonable expectations, because a DC-10 with no hydraulic flight controls could not be expected to land successfully on a runway. On the ground, the airport and county emergency plan, a full-scale disaster drill held in 1987 and nearly half an hour of warning meant rescuers were waiting when the aircraft arrived.
What changed after United Airlines Flight 232?
The NTSB's safety issues included the design of the CF6-6 fan rotor, the manufacture and inspection of titanium engine parts, and how hydraulic systems are protected from engine debris. Other fan disks made from the same batch of titanium were recalled for ultrasonic testing, and two were found with defects. Read more in our guide to DC-10 crashes.
Sources: The facts and written text on this page come from the 3 videos on this page, by Mentour Pilot, Fascinating Horror, KCCI.
