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Fri Jul 19, 2019, 10:20 AM

30 Years Ago Today; United Flight 232 loses its center engine, hydraulics, and almost all control

https://en.wikipedia.org/wiki/United_Airlines_Flight_232


N1819U, the aircraft involved in the accident, landing at San Diego International Airport, California in 1977

United Airlines Flight 232 was a regularly scheduled United Airlines flight from Denver to Chicago, continuing to Philadelphia. On July 19, 1989, the DC-10 (registered as N1819U) serving the flight crash-landed at Sioux City, Iowa, after suffering a catastrophic failure of its tail-mounted engine, which led to the loss of many flight controls. At the time, the aircraft was en route from Stapleton International Airport to O'Hare International Airport. Of the 296 passengers and crew on board, 112 died in the accident and 184 survived, making the crash the fifth-deadliest involving the DC-10, behind Turkish Airlines Flight 981, American Airlines Flight 191, Air New Zealand Flight 901, and UTA Flight 772.[note 1] Despite the deaths, the accident is considered a prime example of successful crew resource management because of the large number of survivors and the manner in which the flight crew handled the emergency and landed the airplane without conventional control.

Events


Radar plot of the plane's flight path, from the NTSB report

Takeoff and failure
Flight 232 took off at 14:09 CDT from Stapleton International Airport, Denver, Colorado, bound for O'Hare International Airport in Chicago with continuing service to Philadelphia International Airport.

At 15:16, while the plane was in a shallow right turn at 37,000 feet, the fan disk of its tail-mounted General Electric CF6-6 engine explosively disintegrated. Debris penetrated the tail in numerous places, including the horizontal stabilizer, puncturing the lines of all three hydraulic systems.

The pilots felt a jolt, and the autopilot disengaged. As Records took hold of his control column, Haynes focused on the tail engine, whose instruments indicated it was malfunctioning; he found its throttle and fuel supply controls jammed. At Dvorak's suggestion, a valve cutting fuel to the tail engine was shut off. This part of the emergency took 14 seconds.

Attempts to control plane
Meanwhile, Records found that the plane did not respond to his control column. Even with the control column turned all the way to the left, commanding maximum left aileron, and pulled all the way back, commanding maximum up elevator – inputs that would never be used together in normal flight – the 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 slowly level out.

The various gauges for all three hydraulic systems were registering zero. The three hydraulic systems were separate, so that failure of any one of them would leave the crew with full control, but lines for all three systems shared the same narrow passage through the tail where the engine debris had penetrated, and thus control surfaces were inoperative. The crew contacted United maintenance personnel via radio, but were told that, as a total loss of hydraulics on the DC-10 was considered "virtually impossible", there were no established procedures for such an event.

The plane was tending to pull right, and slowly oscillated vertically in a phugoid cycle – characteristic of planes in which control surface command is lost. With each iteration of the cycle, the aircraft lost approximately 1,500 feet (460 m) of altitude. On learning that Fitch, an experienced United Airlines captain and DC-10 flight instructor, was among the passengers, the crew called him into the cockpit for assistance.

Haynes asked Fitch to observe the ailerons through the passenger cabin windows to see if control inputs were having any effect. Fitch reported back 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 over 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 (ATC) was contacted and an emergency landing at nearby Sioux Gateway Airport was organized. Haynes kept his sense of humor during the emergency, as recorded on the plane's cockpit voice recorder (CVR):

Fitch: "I'll tell you what, we'll have a beer when this is all done."

Haynes: "Well I don't drink, but I'll sure as hell have one."


and later:

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: "[laughter] Roger. [laughter] You want to be particular and make it a runway, huh?"


A more serious remark often quoted from Haynes was made when 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 that "We were too busy [to 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 City, 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, there was no change in the controllability of the aircraft.

Landing was originally planned on the 9,000-foot (2,700 m) Runway 31. Difficulties in controlling the aircraft made lining up almost impossible. While dumping some of the excess fuel, the plane executed a series of mostly right-hand turns (it was easier to turn the plane in this direction) with the intention of lining up with Runway 31. When they came out they were instead lined up with the shorter (6,888 ft) and closed Runway 22, and had little capacity to maneuver. 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 plane touched down. Runway 22 had been permanently closed a year earlier.

ATC also advised that I-29 ran North and South just East of the airport which they could land on if they did not think they could make the runway. The pilot opted to try for the runway instead.


The plane landed askew, causing the explosion and fire seen in this still from local news station video.

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 were unable to control both airspeed and sink rate. On final descent, the aircraft was going 220 knots and sinking at 1,850 feet per minute (approximately 407 km/h forward and 34 km/h downward speed), while a safe landing would require 140 knots and 300 feet per minute (approximately 260 km/h and 5 km/h respectively). Fitch needed a seat for landing; Dvorak offered up his own, as it could be moved to a position behind the throttles. Dvorak sat in the cockpit's jump seat for landing. Fitch noticed the high sink rate and that the plane started to yaw right again, and pushed the throttles to full power in an attempt to mitigate the high sink rate and level the plane. It was now 16:00. The CVR recorded the following final moments:

Records: "Close 'em off."
Haynes: "Left turn. Close 'em off."
Records: "Pull 'em off"
Haynes: "Left turn, left turn, close the throttles."
Fitch: "Nah, I can't pull 'em off or we'll lose it, that's what's turning ya."
Haynes: "Okay."
Fitch: "Left Al!"
Haynes: "Left turn! Left, left, left, left, left, left, left, left, left, left!"
Ground Proximity Warning System (GPWS): "Whoop whoop pull up. Whoop whoop pull up. Whoop whoop pull up."
Haynes: "Everybody stay in brace!"
GPWS: "Whoop whoop pull up."
Haynes: "God!"
[Sound of impact, end of recording]


There was not enough time for the flight crew to react. The tip of the right wing hit the runway first, 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. On the final impact, the right wing was shorn 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


Locations of passengers indicated by lack of injury, severity of injury, and reason of death from the NTSB report

Of the 296 people on board, 111 died. Most were killed by injuries sustained in 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 185 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).

1 died 31 days after the crash.

47 were seriously injured (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 20H moved to an unknown seat and died of smoke inhalation.

One crash survivor died 31 days 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 on board the flight because of the United Airlines "Children's Day" promotion. Eleven children, including one lap child, died. Many of the children were traveling alone.

It was not until 35 minutes after the crash that rescuers identified the debris that was the remains of the cockpit, with the four pilots alive inside. All four recovered from their injuries and eventually returned to flight duty.

</snip>






To the flight crew, Al Haynes, Bill Records, Dudley Dvorak and Denny Fitch;

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Replies to this discussion thread
Arrow 20 replies Author Time Post
Reply 30 Years Ago Today; United Flight 232 loses its center engine, hydraulics, and almost all control (Original post)
Dennis Donovan Jul 19 OP
wryter2000 Jul 19 #1
Clash City Rocker Jul 19 #2
wryter2000 Jul 19 #4
Clash City Rocker Jul 19 #11
wryter2000 Jul 19 #17
Clash City Rocker Jul 19 #18
lostnfound Jul 19 #3
wryter2000 Jul 19 #5
oswaldactedalone Jul 19 #6
renate Jul 19 #7
lostnfound Jul 19 #19
bluecollar2 Jul 19 #8
Scurrilous Jul 19 #9
Blue_Tires Jul 19 #10
Johnny2X2X Jul 19 #12
renate Jul 19 #14
geralmar Jul 19 #13
Dennis Donovan Jul 19 #15
misanthrope Jul 19 #16
Reader Rabbit Jul 20 #20

Response to Dennis Donovan (Original post)

Fri Jul 19, 2019, 10:36 AM

1. Oh, lordy

I'm flying tomorrow. I so didn't need to read this.

Cheers for the crew. I hope I get Sully Sullenberger.

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Response to wryter2000 (Reply #1)

Fri Jul 19, 2019, 10:58 AM

2. Don't worry. The fact that this is still newsworthy 30 years later tells you how rare it is

The most dangerous parts of flying are the drive/cab ride to and from the airport. The only safer way to get from one place to another is in an elevator, I have been told.

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Response to Clash City Rocker (Reply #2)

Fri Jul 19, 2019, 12:24 PM

4. There you go

Being logical.

I have a little pill to take if the anxiety gets bad. Actually, dealing with the airport is more stressful than the flight.

Tanks for the reassurance.

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Response to wryter2000 (Reply #4)

Fri Jul 19, 2019, 03:30 PM

11. Agreed, airports suck

They seem to go out of their way to make flying as unpleasant as possible. At least in the US.

For the record, I have all this down because I have to say it to my wife every time we fly. And God help if there’s turbulence. But I really hope it helps in some way.

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Response to Clash City Rocker (Reply #11)

Fri Jul 19, 2019, 04:41 PM

17. Frankfurt is the worst I've ever been in

It's huge. There are many places where you have to climb stairs. And the people are rude. I'll be happy if I never see that place again.

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Response to wryter2000 (Reply #17)

Fri Jul 19, 2019, 05:36 PM

18. Speaking of foreign airports, Moscow is ridiculously paranoid

It’s the only airport I’ve been to where your luggage gets x-rayed twice before it gets on the plane. The line to get through customs is very quiet; people are apparently afraid to talk there.

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Response to wryter2000 (Reply #1)

Fri Jul 19, 2019, 11:52 AM

3. Aviation community general learns its lessons

Every crash studied to determine how to change things and make it safer. Not only mechanically, but human interaction, safety oversight, maintenance habits and programs, pilot training, etc.

You want decent weather and midsize to large aircraft because the pilots are more experienced than the regionals.

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Response to lostnfound (Reply #3)

Fri Jul 19, 2019, 12:26 PM

5. Southwest

It's going to be gawd awful hot on the East coast, but I don't suppose that will affect flying.

Thanks for the reassurance

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Response to Dennis Donovan (Original post)

Fri Jul 19, 2019, 12:28 PM

6. Met a survivor of that flight

in 1990 who was a patient in our Physical Therapy clinic. He suffered severe back, right hip and right shoulder injuries that prevented a return to work. He was also traumatized by the event as he was thrown from the plane and knocked unconscious. He told us that as he was coming to he heard faint voices saying “this one’s gone, no hope for this one” and he figured he must be dead.

As the rescuers finished placing markers next to the bodies of the deceased and moved on to another area, he began to moan and one of the rescuers heard him. It turned out that he was lying among a group of about twenty bodies and he was the only survivor. He had to lay there for a while as rescuers brought out the rescue board, splinted his leg and arm, and stabilized his head and neck.

When he realized that he was the only one around him who survived, he began to feel guilty about it and couldn’t seem to shake it. He eventually received his disability and based on our assessment, it was the right call.

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Response to Dennis Donovan (Original post)

Fri Jul 19, 2019, 12:36 PM

7. I sat next to a guy who'd been on this flight on his first trip since it happened

It was pre-9/11, so they let him stay in the pre-boarding area and then get on the plane even though he was super drunk. The staff knew why he was that way.

We had talked while we waited and I seemed to have a calming influence on him, so the staff asked whether I would sit next to him on the flight. I was in my 20s and totally untrained in trauma support, but I was also too polite to say that it was not my frickin’ job to babysit a drunk guy with PTSD. So that’s what happened. I was exhausted by the end of the flight and nobody said thank you.

He was a very nice guy though and overall I was happy to do it. We’re all here to take care of each other. I just wish I’d been given either a choice or some support and appreciation from the airline. But I liked him and felt awful for him and I still think of him fondly and often.

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Response to renate (Reply #7)

Fri Jul 19, 2019, 07:47 PM

19. I cannot imagine getting on any other flight after surviving that one

He was a brave dude for going back.

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Response to Dennis Donovan (Original post)

Fri Jul 19, 2019, 01:15 PM

8. Before I retired as an inspector

I spent several years performing dye penetrant inspections on Rolls Royce RB211 and Trent urbine engine discs and other engine components.

A fan disc inspection could easily take 6-8 hours to complete. I never found a disc or other "Group A" component that was cracked or flawed in my entire time as an inspector, a testimony to the quality of the Rolls Royce manufacturing process.

I also remember my supervisor constantly complaining that our inspections "took to long" since "you never find anything wrong anyway."

What this United crew was able to do is a testament to aviation professionals and their training.

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Response to Dennis Donovan (Original post)

Fri Jul 19, 2019, 02:04 PM

9. ...

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Response to Dennis Donovan (Original post)

Fri Jul 19, 2019, 02:15 PM

10. That was a pure masterclass of airmanship on display

Without some carefully coordinated CRM they very easily could have all perished...

EDIT: And even then, sometimes world-class stick-and-rudder skills and flawless improvisation in a dire situation still isn't enough (See Southern Airways 242 and Japanese Air Lines 123)

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Response to Dennis Donovan (Original post)

Fri Jul 19, 2019, 03:37 PM

12. The crew was amazing

In simulations after, no crew was able to reproduce that landing. It was a 1 in a million shot.

I work in the industry and we had a presentation this week where the lead investigator came to our site and spoke and answered questions. They also interviewed the head flight attendant. Really powerful stuff.

The airlines still do not have a good procedure in place for what to do with lap children in the event of a plane crash. But this crash definitely made the airline industry safer.

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Response to Johnny2X2X (Reply #12)

Fri Jul 19, 2019, 04:11 PM

14. I sort of remember watching it live on TV... am I remembering correctly?

They knew well ahead of time that the landing would be... well, the way it was. “Rough” isn’t the right word. The news media knew it was going to be a crash landing, right?

Or is that a false memory? I definitely remember watching CNN and seeing the plane doing cartwheels, but maybe that was a replay.

Amazing that anybody lived.

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Response to Dennis Donovan (Original post)


Response to geralmar (Reply #13)

Fri Jul 19, 2019, 04:17 PM

15. What are the odds that, possibly the only pilot to test under the conditions of 232...

...would be faced with the same situation on a real flight? Denny's presence on 232 was a stroke of unimaginable luck.

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Response to Dennis Donovan (Original post)

Fri Jul 19, 2019, 04:17 PM

16. I remember seeing that footage

and being surprised anyone at all survived.

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Response to Dennis Donovan (Original post)

Sat Jul 20, 2019, 12:01 AM

20. If I remember correctly, computers couldn't replicate the positive result.

After the flight, they ran the situation through simulator after simulator, and not one computer could solve the scenario with less loss of life than the actual human pilots of the real flight. Didn't most of the post-flight computer simulations end with the deaths of all on board? (Maybe I'm romanticizing the human factor.)

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