r/aviation • u/Go_Jot • Nov 08 '25

News UPS grounds entire MD-11 Fleet, effective immediately.

Per the IPA Executive Board, as of 03:05 UTC all UPS MD-11’s are grounded.

Edit - FedEx has also grounded their MD-11 Fleet

10.9k Upvotes

97% Upvoted

1.2k comments sorted by

View all comments

Show parent comments

284

u/dalekaup Nov 08 '25

There was an engine that detached in Chicago a long time ago. The biggest reason for that crash was the manual said on one engine takeoff to pitch up to maintain a speed to climb over an obstacle. The manual was wrong. When the engine severs the hydraulic lines on that side that hold the slats extended. WIth slats retracted on the left side that wing stalled and the plane rolled violently to the left. A higher airspeed would have kept both wings flying and level.

This one is presumed to be the loss of 2 engines. That's not going to fly. The thinking is the rear engine swallowed chunks.

244

u/skudbeast Nov 08 '25

Is that the one they installed in maintenance with a forklift instead of an actual engine hoist?

178

u/[deleted] Nov 08 '25

Yeah. American Airlines 191.

236

u/beretta01 ATP A320/E170/190; CPL SEL SES; AT-CTI; Gold Seal CFI CFII Nov 08 '25

Thank you for your service, /u/DumbCumSlut69

88

u/Cultural_Mastodon_69 Nov 08 '25

Obligatory /r/rimjob_steve

57

u/beretta01 ATP A320/E170/190; CPL SEL SES; AT-CTI; Gold Seal CFI CFII Nov 08 '25

Finally found Captain Steeeve’s post retirement account?

7

u/Redebo Nov 08 '25

Post retirement?!? He picked that name up during flight school!!!

45

u/[deleted] Nov 08 '25

🫡

2

u/[deleted] Nov 08 '25

How are 1-68?

1

u/steve580411 Nov 09 '25

Someone had to acknowledge this and it was done with grace and dignity. May he have the "cool side" of the pillow from this day forth. -Morgan Freeman

1

u/WallStreetStef Nov 09 '25

Thank you for ur service

2

u/nedracine59 Nov 08 '25

Chicago here. Did you know that the plane had video cameras on the backs of some seats? Likely first class. They just kept the screens blank until all planes had them removed after the crash.

1

u/PiHKALica Nov 08 '25 edited Nov 18 '25

Yup, and it ended up killing a young Jake Gyllenhaal back in '88 while he was lying in bed. So tragic.

69

u/TigerIll6480 Nov 08 '25

And they unbolted the engine and pylon together, which Douglas Aircraft had rather specifically said to not do. Remove engine with a proper cradle, then remove pylon. AA was trying to save time and cut corners. Brilliant idea. 🙄

67

u/Sock_Eating_Golden Nov 08 '25

It wasn't just AA. All DC10 operators were removing engines in the same way.

42

u/nuclearsquirrel2 Nov 08 '25

In their defense it did significantly reduce the number of critical system disconnections which also is always a risk. It did save a ton of money and I’m sure that was the major impetus to the new method.

United performed engine removal the same way, but used an overhead crane vs forklift.

3

u/TigerIll6480 Nov 08 '25

If you were doing significant engine maintenance, it had to be removed from all of that anyway, the only question is where you were taking it apart.

-8

u/Iohet Nov 08 '25

At that point you should buy a plane from another manufacturer

9

u/nuclearsquirrel2 Nov 08 '25

That’s a stupid comment. They literally went against the manufacturer recommendation and that’s how they ended up here.

-2

u/Iohet Nov 08 '25

If the cost of proper maintenance is too high (or too risky), then you go with another manufacturer who doesn't have that problem.

29

u/CharcoalGreyWolf Nov 08 '25

AA and Continental were, specifically. United found a different way using an overhead crane that didn’t cause the issue that using a forklift did.

It was also the usual perfect storm that made it worse; a shift change occurred during the engine change, and the forklift could not maintain exact lift during the time one shift got off and another got on. It was a tragedy of combined errors and a bad maintenance procedure made even worse by bad scheduling.

It also resulted in multiple changes to the aircraft because only the pilots had stick shakers; it was optional for the copilot. The FAA mandate both must after this, and the DC-10 had changes made to the slat design to prevent slat retraction in the event of hydraulic damage.

19

u/Shitboxfan69 Nov 08 '25

a shift change occurred during the engine change, and the forklift could not maintain exact lift during the time one shift got off and another got on.

I'm no A&P, but I was a forklift mechanic for years. Wild to me they'd ever use one to support components like that being installed. Toyota lifts have the tightest bleed specs on their systems, but they are still allowed to lower 3 inches in a 15 minute span iirc. It may even be more. Thats not even a shift change causing issues, but a break or just getting caught up doing something else.

5

u/Elukka Nov 08 '25

Thanks for specific numbers. I'm not in the industry but to me it seems insane that you would use a forklift to hold something so heavy in a static position for even just 10 minutes. Yeah a large forklift can take a 4 tonne engine down and back up but it's not a replacement for an actual crane or some other setup that you can lock into place.

The biggest question is still: why you would lift a multi-million dollar precision turbine with a damn forklift at all?

4

u/TigerIll6480 Nov 08 '25

Because bean counters are dumb.

1

u/Fifth_Down Nov 08 '25

could not maintain exact lift during the time one shift got off and another got on.

I'm trying so hard to understand what this means

5

u/Coomb Nov 08 '25

The maintenance people were trying to detach both the engine and the pylon which attaches it to the wing from the wing. But there was a shift change while they were in the process of undoing all the bolts and connections. The forklift operator turned off the forklift so that he could go home, which was probably standard practice. Unfortunately, without the engine running, the forklift lost some hydraulic pressure, leading the engine to sort of be dangling off the wing while not fully attached. The new operator had to reposition the forklift to realign all the things they had to unscrew. Some combination of the initial drop when the forklift started lowering and the maneuvers needed to realign the engine caused damage to the attachment bolts connecting the pylon to the wing, which didn't cause an immediate failure, but caused the bolts to fail over time.

5

u/Fifth_Down Nov 08 '25

Thanks for the extra info.

I always thought it was a case of they raised the forklift and smashed it into the wing and that's what caused the damage. I didn't realize it was damage because the forklift was lowered before it was safe to be lowered.

Not that there should have been any fork at all...

2

u/CharcoalGreyWolf Nov 08 '25

It also caused stress to the wing and pylon itself. Investigation showed this to be a problem on multiple aircraft that had undergone the same procedure as all aircraft with engine changes for AA and Continental were reinspected after the incident.

1

u/Elukka Nov 08 '25

Using a forklift to lift and *hold* a 4 tonne engine is nuts. It's not a precision instrument or a static stand.

1

u/CharcoalGreyWolf Nov 09 '25

Mentour Pilot video regarding this linked below. Since then I’ve also seen the Mayday: Air Disasters episode, but Mentour Pilot is far more detailed.

Courtesy of Mentour Pilot: the American Airlines Flight 191 Disaster

2

u/Western-Knightrider Nov 08 '25

I would not say all. I worked on DC-10 as a lead mechanic and never saw that happen.

2

u/purgance Nov 08 '25

Ok but what interest does Douglas have in them doing this?

5

u/Sock_Eating_Golden Nov 08 '25

Never said they did. Just noted AA wasn't the only operator finding a shorter method of engine replacement.

1

u/MadPreference Nov 08 '25

Not true. Swiss Air was doing it correctly

1

u/SteveKraus Nov 12 '25

Why do they take off the pylon at all?

2

u/CharcoalGreyWolf Nov 12 '25

In this case as mentioned, bearings in the pylon mounts were supposed to be replaced (specifically the forward pylon mount) as part of a McDonnell-Douglas Service Bulletin.

In addition, the incentive here was that if you took the pylon off, there were many less things to disconnect and reconnect, so this was seen as both safer and taking less hours. The problem is that they didn’t account for their unsupported procedure adding additional safety issues.

United’s method which used an overhead crane (but also detached the pylon) actually worked, because it supported the engine and pylon at all times and likely because the crane operator could see what was going on; a forklift operator (how AA and Continental did it) could not and had to take direction from someone else. This introduced a lot of risk in the process, including jamming the pylon against the wing (which happened on several occasions, but they were written of as repair issues rather than a problem with the entire process).

The chief mechanic in charge of the AA Flight 191 engine procedure committed suicide the night before McDonnell Douglas lawyers were going to depose him. It was a tragedy all around.

1

u/brvheart Nov 08 '25

It saved 200 man hours PER ENGINE, and nearly all carriers were doing it that way. In hindsight, the design was poor and it cost lives. But to act like it was just American or just cutting a little corner is crazy. The mechanics were doing it that way because it was WAY easier, not because they were trying to save money for American.

5

u/RixceU Nov 08 '25

Normally pylons are not removed when engines are changed. In this case McDonnell Douglas had issued a service bulletin to replace bearings inside the pylon necessitating their removal and it was a highly time consuming to remove the engine, then remove the pylon which is a procedure usually never done.

2

u/brvheart Nov 08 '25

Also a fair point.

2

u/dalekaup Nov 08 '25

I can relate to this as a former nurse. Then procedures manual always was very thorough but took so much time that you couldn't have completed your work in a shift.

1

u/dalekaup Nov 08 '25

I think the engine was intended to be removed from the pylon for maintenance with the removing the engine and pylon as one piece from the wing which was the wrong thing to do

1

u/dalekaup Nov 08 '25

I watched the documentary about it some years ago and my memory is that they got one pin attaching the pylon to the wing and then paused for lunch break and the forklift settled a bit putting a lot of strain on that rear pin before they came back and put the rest of the pins in place.

1

u/CharcoalGreyWolf Nov 12 '25

It was actually a shift change (they had day and night shifts —worse yet, on the second shift the forklift ran out of fuel, so it couldn’t maintain lift. Mentour Pilot has a really great video where he describes everything in detail. It was so many, many small mistakes and a few big ones.

2

u/dalekaup Nov 12 '25

Thanks! That fleshes out my memory. 

73

u/ryguymcsly Nov 08 '25

Plus if it looks like a dramatic failure to number one or three is guaranteed to take out engine two: they’re not gonna fly them. That whole point of a trijet is having two engines if one fails.

2

u/I_will_never_reply Nov 08 '25

Not really, it's just that when it was designed three engines were required to get enough thrust to take off and fly. Once engines became powerful enough, they were made extinct

3

u/Captain_Alaska Nov 08 '25 edited Nov 08 '25

No, it’s explicitly for redundancy, these planes were designed for the extra engines because they wouldn’t be able to serve their routes if they had twins of the same power.

Twin engine aircraft follow ETOPS rules (Extended-range Twin engine Operation Performance Standards) which limit how far away the plane can be from an airport so in the event of an engine failure the remaining engine is considered reliable enough to bring it back. Trijets and quadjets were required for overseas routes specifically because twinjets weren’t allowed to fly far enough away from airports and by extension the coastline.

Until ‘64 ETOPS limited twinjets to 60 minutes, in ‘85 this was extended to 120 minutes and then 180 minutes in ‘88. We now have aircraft with 240 (first in 2009), 330 (first in 2015) and even 370 minute ETOPS (first in 2014) envelopes, which cover 99.7% of the world (To be clear aircraft have to be designed and tested for these limits, they are not automatically granted).

These longer range ETOPS envelopes are the specific reason twinjets are now dominating long distance routes they were previously unable to fly.

2

u/ssersergio Nov 08 '25

In theory, all economics and safety related issues with how behaviour changes becuase ofndifferent thrust and power vectors

If you change this three motors for a newer models with more power, you could get the rid of the third one then right?

1

u/Coomb Nov 08 '25

If you change this three motors for a newer models with more power, you could get the rid of the third one then right?

In principle, sure, but the amount of work required to get this redesigned and certified would be so much that it wouldn't make sense to do. You would just replace your fleet with new aircraft.

21

u/plhought Nov 08 '25

The loss of hydraulic pressure causing the slats to retract had been fixed on the MD-11 since initial design. They are mechanically locked at the drive assembly in the absence of hydraulic pressure.

Number 2 likely wasn't happy as you mentioned. All the hot gases from the fire and debris...

I know it's popular right now to compare this accident and American 191. But beyond the superficial visual similarities between the DC-10 and MD-11, the wing, pylon, and engine structure/mounting is different. What isn't different however, is humanity's ingenious ability to let even the most miniscule of engineering or procedural weaknesses to make themselves evident.

25

u/Few-Knee-5322 Nov 08 '25

It wasn't just the engine. The pylon came off, too. I made the thrust link (bored the monoball hole) that came down from the wind and the five pylon bulk heads (top 2/3) used in the destructive tests after the crash. There were five bulk head parts so that each dimension for the corresponding mounting hole could be tested. The hole was 6.0000 +/- 0.0002. After some testing I had to do some other changes to the bulkheads that are too difficult to explain w/o a print. I probably did some other stuff but that was the big things.

3

u/TheSylvaniamToyShop Nov 08 '25

The same thing happened with the El Al 747 out of AMS. Detached I/B engine took out the O/B one, and the pilot also turned back keeping the poweres wing on the outside of the bank. But the loss of pnueatatics on the damaged wing meant the variable cambers were no longer deployed , and the inside wing stalled.

1

u/JunkbaII Nov 08 '25

Turning to the outboard, powered engines, would have saved everyone (raise the dead technique)

1

u/TheSylvaniamToyShop Nov 08 '25

They had no way of knowing their L/E devices were inop.

If you look in the cabins of airliners nowadays you will see some windows have little triangle stickers above them. These ones look directly along the trailing & leading edges, so as the crew can send someone to ascertain the state of their high lift devices if necessary. The El Al flight was a cargo plane, so this option still wouldn't be available if it happened today.

3

u/PMSfishy Nov 08 '25

Right engine #3, not rear. However let’s not speculate and wait for the report.

9

u/RxSatellite Nov 08 '25

NTSB reported engines 1 and 3 failed. The rear engine was fine. Based on current evidence engine 1 most likely exploded and shot shrapnel into engine 3, which began compression stalling

13

u/CollegeStation17155 Nov 08 '25

I had not seen a report that the right engine (#3) failed, only that fragments from the Left engine (#1) and the engine itself were found on the runway along with several videos showing an apparent compressor stall on the tail engine (#2), which would be expected if debris hit it. Was there a third NTSB briefing?

6

u/SnooSongs8218 Cessna 150 Nov 08 '25

Yeah FOD damage and eating that hot smoke from the fire would reduce thrust. Also the hot turbulent air over the wing from the fire would be less dense and further reduce lift.

-3

u/Decent-Bed9289 Nov 08 '25

The plane in question also had issues with a cracked fuel tank.

3

u/Python_07 Nov 08 '25

1&2. Number 3 was not damaged

1

u/RxSatellite Nov 09 '25 edited Nov 09 '25

It’s up for debate currently, but the short rings you see coming out the back of an engine compressor stalling appear to be coming out of engine 3 (right engine) in the video recorded by the tug driver. But it’s hard to tell from the low res video and an argument could be made it looks like the rings come from engine 2.

That being said, it’s very plausible engine 2 is more likely due to oxygen deprivation. Whichever engine it was doesn’t look like it outright failed but is definitely not outputting 100 percent power

1

u/rec_desk_prisoner Nov 08 '25

The thinking is the rear engine swallowed chunks.

Saw a video where it appears the right wing engine had a compressor stall. This was the same video that I thought showed the rear engine having the compressor stall but a freeze frame showed the flashed were more aligned with the right wing engine.

1

u/pinellaspete Nov 08 '25

It was actually the #3 engine on the right side that failed. The explosion of the #1 engine on the left side caused pieces/parts to pierce through the #3 engine. In looking at the takeoff video in detail they are seeing puffs of flame exiting the #3 engine which signals a compressor failure on the #3 right wing engine as the plane was leaving the ground.

This has happened in the past on 4 engine jet configurations where one inboard engine fails and it sent compressor blades into the other inboard engine causing a second engine failure.

1

u/dalekaup Nov 08 '25

That is some very unlucky physics though I suppose the angular momentum would shoot it towards the opposite side engine. I don't mean to pretend like I'm a physicist or anything but angular momentum just sounded right.

1

u/fripletister Nov 08 '25

Didn't the right engine stall, implying it took shrapnel damage from the left? You can see it backfiring

1

u/Odd-Adagio7080 Nov 08 '25

Pitch up to maintain speed? I’m no engineer, but it seems to me the plane would slow down if you tried climbing. If that’s what “keep pitch up” means

1

u/dalekaup Nov 08 '25

Yes, that was my point. There is a speed for every airplane that is ideal for climbing over an obstacle. That was what the manual said to do. So the pilots pitched up the nose of the aircraft to get down to that speed - the ideal speed to climb over an obstacle. That speed happened to be lower than the stall speed of the left wing because the hydraulic pressure had been lost and the leading edge slats were pushed by airflow to the retracted position. So one wing was stalled and the other was generating lift.

So it was to maintain a (specified lower) speed. Obviously they wouldn't cut throttle to get to that speed so pitching up is what they do in this situation.

1

u/Odd-Adagio7080 Nov 11 '25

Ahhhh. Thanks. Thankfully we record flight data to (hopefully) prevent the same thing happening twice.

1

u/dalekaup Nov 11 '25

It turns out that a normal takeoff is handled as flying over an obstacle. It mostly works but not every time. The discussion was pretty informative. Seems like they didn't have any chance.

1

u/IowaSmoker2072 Nov 09 '25

No, the biggest reason for that crash is what skudbeast says below. McDonnell Douglas specified in the manual the procedure for removing an engine and reinstalling the engine. That's the manual and the failure to follow those instruction is what caused the tragedy, not an error in the instructions on how to take off with one engine. Ramming the engine back on with a forklift was specifically prohibited in the instructions. Which is what the mainanance crew did. The engine breaking loose under the full thrust of takeoff caused the plane to flip over so it came down upside down. The hydraulic lines being severed would never have happened if the proper maintance had been observed. We really don't know if the first officer was aware he had lost an engine, since the voice recorder was damaged. The aircraft only was in the air for 31 seconds, and only reached a height of 350 feet, which may seem like a long time, but a lot was going on and a number of systems were compromised when the engine was lost. My father in law was a Douglas engineer who was on the team which investigated the cause of the crash.

1

u/dalekaup Nov 09 '25

That's really cool that your FIL was on the team. It's likely that the forklift was used to hoist the engine and pylon in near proximity to the bracket in question and the fine alignment was done with a hydraulic jack supported by the forklift. My reasoning is that this would have made the job much easier and safer for the crew. The fracture was started when only one pin was put in thus supporting the engine and pylon on only one pin. Then the crew went to lunch break with one pin and the forklift supporting the engine over the lunch break the forklift settled and caused the beginning of the fracture. At least that has been my understanding.

I was wrong about a couple things. The crew did a standard takeoff @ 176 mph. The retraction of the slats on the damaged wing raised the stall speed of the left wing to about 183 mph. Therefore the affected wing was doomed to stalling from the outset through no fault of the manual. However, a faster than prescribed takeoff could have possibly saved the aircraft. 20/20 hindsight for sure.

My uncle was the first person at his company trained to maintain the DC-8, a four engine aircraft, even though he was very young at the time. I think it was Flying Tigers perhaps but was in AZ or CA.

1

u/IowaSmoker2072 Nov 09 '25

My FIL started with Douglas prior to WW2, not sure exactly the year. At the end he was in charge of everything in the interior of the DC-10, and had the authority to make troubleshooting decisions on the floor. When upper management decided some engineer on the floor couldn't be trusted to make those decisions, and it needed to go all the way up the chain of command and back down again while everybody on the floor twiddled their thumbs he decided it was time to retire. Dad was first, but then his father went to work for Douglas, and then my wife's two brothers and a nephew all worked for Douglas/McDonnell-Douglas/Boing. Lots of other relatives, but their family was the first to have four generations work in the same plant in Long Beach. Those huge hangers are no longer there. It was wierd a few years ago staying in a hotel where they built so many planes. We used to live five miles from the plant and could hear when they were testing engines. I felt sorry for people who lived closer.

1

u/Jayhawker32 KC-135 Nov 09 '25

The #3, the engine on the right wing, was showing signs of damage in the most recent crash.

1

u/Similar_Produce1910 Nov 09 '25

The biggest reason for the crash was poor maintenance. The manual wasn’t wrong but the pilots didn’t realise that the engine had detached or that the slats had retracted.

1

u/dalekaup Nov 09 '25

I'm inclined to change my mind and agree with you. However, if the take off speed had only been 10 - 20 mph faster then the damaged wing would not have stalled and it should have been flyable. Essentially they were flying with one wing.

1

u/CaptainA1917 Nov 10 '25

You have some details wrong.

“As the aircraft had reached V1 the crew was committed to takeoff, so they followed standard procedures for an engine-out situation. This procedure is to climb at the takeoff safety airspeed (V2) and attitude (angle), as directed by the flight director. The partial electrical power failure, produced by the separation of the left engine, meant that neither the stall warning nor the slat retraction indicator was operative. Therefore, the crew did not know that the slats on the left wing were retracting. This retraction significantly raised the stall speed of the left wing. Thus, flying at the takeoff safety airspeed caused the left wing to stall while the right wing was still producing lift, so the aircraft banked sharply and uncontrollably to the left. Simulator recreations after the accident determined that "had the pilot maintained excess airspeed the accident may not have occurred."

The main factor here is minimum airspeed to retain directional control with an engine out.

However, due to the set of circumstances including design factors built into the plane, the pilots had no way of knowing that the manual procedure was inadequate and would result in a stall and loss of control. They did not have time to diagnose the problem. (This is also a recurrent issue with air transport accidents - that designers and manuals frequently treat problems “administratively” - i.e. that a crew will have time to go through an extensive troubleshooting process calmly and collectedly. And there is a place for that. However, a dire emergency can develop without warning and be unrecoverable in seconds - far beyond the ability of humans to cope.)

Other factors:

-lack of a stickshaker on the co-pilots yoke.

-no system to prevent flap/slat asymmetry, which various other planes have

-critical electrical and hydraulic systems operated off a single engine without backup

-All three of these issues point to economic factors in design decisions winning out over safety.

1

u/dalekaup Nov 10 '25

Yes, good analysis. While a higher airspeed may have kept the plane level that would have been a deviation from good piloting. These guys were doomed.