Very fast. Quite sad to see it happen. Also quite puzzling is how the Air India disaster still does not have a root cause analysis done (though supposedly it will be released end of this year)
Looks like it's been moved to <a href="https://www.ntsb.gov/investigations/Documents/DCA26MA024%20Preliminary%20Report.pdf" rel="nofollow">https://www.ntsb.gov/investigations/Documents/DCA26MA024%20P...</a>
Originally explained on the blancolirio channel on YouTube -<p>The timing and manner of the break make a lot more intuitive sense when you consider that the engine is essentially a massive gyroscope. As the plane starts to rotate, the spinning engine resists changes to the direction of its spin axis, putting load on the cowling. When the cowling and mount fail, that angular momentum helps fling the engine toward the fuselage.
I think far simpler explanation is "the back part failed first and engine is making thrust so it just flipped over on now-hinge mounting
That's why it flipped upwards, but not why it flipped towards the body of the plane / to the right.
Yup. That's exactly what experts said of American Airlines flight 191 which was basically the same engine mount, same failure. Engine flipping over the wing.
The failure of the pylon appears to be different. On AA 191, the pylon rear bulkhead cracked and came apart. In the case of UPS flight 2976, the pylon rear bulkhead looks to be in one piece, but the mounting lugs at the top of the rear bulkhead cracked.<p>Admiral Cloudberg has a great article on AA 191 that covers exactly what happened: <a href="https://admiralcloudberg.medium.com/rain-of-fire-falling-the-crash-of-american-airlines-flight-191-e17ffc5369e5" rel="nofollow">https://admiralcloudberg.medium.com/rain-of-fire-falling-the...</a>
American 191's engine mount failed because of improper maintenance. It remains to be seen whether this failure had the same cause or if it was something else, such as metal fatigue.
A failure due to metal fatigue would still be a failure to properly maintain the aircraft, right? I know by "improper maintenance," you're referring to actual improper things being done during maintenance, and not simply a lack of maintenance. But I'm reading things like "the next check would've occurred at X miles," and, well... it seems like the schedule for that might need to be adjusted, since this happened.
Yes, when I said "improper" I meant the American 191 maintenance crew took shortcuts. The manual basically said "When removing the engine, first remove the engine from the pylon, then remove the pylon from the wing. When reattaching, do those things in reverse order." But the crew (more likely their management) wanted to save time so they just removed the pylon while the engine was still attached to it. They used a forklift to reattach the engine/pylon assembly and its lack of precision damaged the wing.[0]<p>Fatigue cracking would be a maintenance issue too but that's more like passive negligence while the 191 situation was actively disregarding the manual to cut corners. The crew chief of the 191 maintenance incident died by suicide before he could testify.<p>[0] <a href="https://en.wikipedia.org/wiki/American_Airlines_Flight_191#Engine_separation" rel="nofollow">https://en.wikipedia.org/wiki/American_Airlines_Flight_191#E...</a>
If the (FAA-approved) maintenance schedule says "the next check should occur at X miles" and X miles hasn't happened yet, then it's not going to be classified as improper maintenance -- it's going to be classified as an incomplete/faulty manual.<p>Now, of course, if that maintenance schedule was not FAA-approved or if the check was not performed at X miles, that's going to be classified as improper maintenance.
It depends. This aircraft was made near the beginning of the MD-11 production and if the original analysis for the fatigue life of this location was wrong, then you would expect to see that appear in older aircraft first. If that ends up being the case then it's not an inspection or maintenance issue, it's an engineering failure. Given aerospace accident history I would say that is less likely than some maintenance issue but we won't know for sure for a bit.
Flipping backwards is what caused the engine to fly to the right and land to the right of the takeoff runway. The stills in the NTSB preliminary report clearly show the engine flying over the aircraft, to the right, and then heading straight down.
There might be some truth in that. But the report doesn't confirm that theory.
What theory? That the mount failed? Or the rotation of the engine in the photos going up and over the fuselage?<p>It seems like both are true, but doesn't necessarily prove WHY the mount failed.
Not an aviation expert at all, so take this with a grain of salt, but I think "the spinning engine resists changes to the direction of its spin axis" offers two important insights:<p>* why it failed at rotation (the first/only sudden change of direction under full throttle) rather than as soon as it was mounted onto the plane, while taxiing, as soon as they throttled up, mid-flight, or on landing. This is important because at rotation is the worst possible time for this failure: no ability to abort take-off, no ability to land safety under no or severely limited power, little time to react at all, full fuel. Knowing these failures are likely to manifest then stresses the importance of avoiding them.<p>* why it failed in such a way that it damaged the rest of the plane.<p>Not so much what was wrong with the mounting in the first place, if that's what you're asking. Presumably it was designed to withstand the forces of this moment and clearly has done so many times before.
That the engine was flung into the fuselage due to gyroscopic forces.
Well, <i>some</i> force flung it inboard and above the fuselage (gods, that CCTV stills sequence.) Knowing that the engine rotates CCW, there are not many candidates.
This is a preliminary report. Its purpose is to present initial evidence/information.<p>The final reports are always much more comprehensive.
I'm presenting it "useful not true" - not an RCA.
I assume such forces are calculated and added in when deciding hot thick to make those mounting brackets.
Yes, obviously; MD-11s aren't flinging engines off the wing every single takeoff. A 34 year old airframe may or may not actually match design strength, though.
Yes, but the point is that this moment of the takeoff is when a failure that's been waiting to happen is most likely both because of the thrust and the gyroscopic resistance.
Yep. Now do 3 decades of metal fatigue.
Aluminum has limited loading cycles
I'd be very surprised to read that the aft lug that cracked (and the bearing it contained) were made of aluminum. They were almost certainly steel or Inconel.
Wouldn't that be true of all cast metal objects?<p>Or are some metals impervious?
No; roughly, yes. Based on the crystal structure of the metal, fatigue works differently.<p>> The fatigue limit or endurance limit is the stress level below which an infinite number of loading cycles can be applied to a material without causing fatigue failure.[1] Some metals such as ferrous alloys and titanium alloys have a distinct limit,[2] whereas others such as aluminium and copper do not and will eventually fail even from small stress amplitudes.<p><a href="https://en.wikipedia.org/wiki/Fatigue_limit" rel="nofollow">https://en.wikipedia.org/wiki/Fatigue_limit</a>
Grounding all MD-11s and DC-10s is a major move. I guess it makes sense as a big factor was the fatigue cracks on the pylon (lugs), despite the pylon not being behind on inspections. I am wondering what the inspections of pylons in other planes will yield, likely that will determine whether the grounding will continue.<p>But beyond figuring out why the engine mount failed, I am very interested in what caused the actual crash. "Just" losing thrust in a single engine is usually not enough to cause a crash, the remaining engine(s) have enough margin to get the plane airborne. Of course this was a major structural failure and might have caused additional damage.<p>EDIT: It seems there was damage to the engine in the tail, even though this was not specified in the preliminary report, likely because it has not been sufficiently confirmed yet.
And if the failure of a wing engine can cause the rear engine to fail, that would raise concerns about all "two in front one in back" trijets. Similar to how putting the Space Shuttle orbiter's heat shield directly in the line of fire for debris that comes off he rocket during launch turned out to be a bit of a problem.
At this point there aren’t any trijet designs like that being built, and it’s unlikely we’ll ever see a new trijet design. It served a role in the transition from four engines to two, but now with ETOPS-370 there’s no commercially viable route that can’t be served with an appropriate twinjet.
There are several passenger trijets still existing - they are just not commercial airliners. Dassault for one is quite fond of the design; the Falcon 900, 7X and 8X are trijets, and I'm pretty sure the latter two are still in production. I wouldn't be at all surprised to see another trijet design from them probably around 2030.
Don't forget about Tupolev Tu-154. It didn't stop flying as a commercial airplane because of safety, rather because of noise emission limits.
The Falcons have all three engines tail mounted, so not the same "type" of trijet as MD-11.
And the failure of an inboard wing mounted engine can cause the failure of an outboard wing mounted engine on the same side, as in the case of El Al 1862. <a href="https://www.faa.gov/lessons_learned/transport_airplane/accidents/4X-AXG" rel="nofollow">https://www.faa.gov/lessons_learned/transport_airplane/accid...</a><p>And the failure of an engine mounted on the left wing can cause debris to cross through the fuselage structure and cause a failure of the engine mounted on the right wing, or to fly thousands of feet in any particular direction, as happened to American Airlines in both a ground run incident, and in their Flight 883 accident.<p><a href="https://www.dauntless-soft.com/PRODUCTS/Freebies/AAEngine/" rel="nofollow">https://www.dauntless-soft.com/PRODUCTS/Freebies/AAEngine/</a><p><a href="https://aerossurance.com/safety-management/uncontained-cf6-aa-b767/" rel="nofollow">https://aerossurance.com/safety-management/uncontained-cf6-a...</a>
The industry also responded to those crashes. For example, the El Al 1862 incident prompted a redesign of the engine strut that was subsequently mandated as a retrofit for all 747s.<p>And here's a more detailed description of that ground run incident. It also found that the failure was related to a design flaw, and mandated that aircraft be grounded for inspection and rework. <a href="https://skybrary.aero/accidents-and-incidents/b762-los-angeles-usa-2006" rel="nofollow">https://skybrary.aero/accidents-and-incidents/b762-los-angel...</a><p>I'm not a regulator or aerospace engineer or anything like that so I can't really say which actions are or are not appropriate. But I do want to observe that these are all unique failures with unique risk profiles that can't all be painted with a single broad brush. All I was trying to do in the previous post was speculate on why a MD-11 failure could result in a grounding of the DC-10 and KC-10A as well. The first thing that came to mind is that I think those are the only remaining trijets of that general shape that are still around. Though I suppose another possibility is that they all share an identical pylon design or something like that.
<i>> Though I suppose another possibility is that they all share an identical pylon design or something like that.</i><p>They're very closely related planes (MD-11 is an upgraded DC-10; KC-10A is a military version of the DC-10), so that wouldn't be surprising. Likely the KC-10A has the same pylon, and the MD-11 has one that's similar enough that it's worth being cautious.
Yeah, the trijet design seems failed in general. Unless you can design it to tolerate any wing+tail dual engine failure -- in which case, why have the tail engine at all?
It wasn’t failed. It was designed for a very specific reason and served that purpose well.<p>Once the reason went away, better designs took over.<p>They were designed to allow smaller jets to fly over the ocean further than a two engine jet was allowed (at the time). Airlines didn’t want to waste all the fuel and expense of a huge 4 engine jet, but 2 wouldn’t do. Thus: the trijet.<p>The rules eventually changed and two engine jets were determined to be safe enough for the routes the trijets were flying.<p>Using two engines that were rated safe enough used less fuel, so that’s what airlines preferred.<p>It was never designed to be used anywhere else as a general design. Two engines did that better.
You've framed this as disagreeing with me, but I don't think you are. I agree the design made sense in the 1960s, when we didn't know any better and requirements were different.
In the case of the quad jets, Boeing tried the 747-SP and had minimal marketing success.<p>In the case of the trijets the MD-11 lived on as a freighter because it had a much higher capacity than anything else smaller than a 747.<p><pre><code> It was never designed to be used anywhere else as a
general design. Two engines did that better.
</code></pre>
Not quite. Dassault still makes a three engined bizjet and in theory the Chinese fly a three engined stealth jet.
> in which case, why have the tail engine at all?<p>"you know what this motorized piece of anything needs, less power"<p>-nobody, ever
At some point it comes down to probabilities. With so many flights going on, one in a million incidents become a certainty. For example UA232 [1] suffered failure in all 3 redundant hydraulic systems due to an uncontained engine failure. Any of the 3 systems would have been enough to retain control of the aircraft. Of course this lead to some investigations on why all 3 systems could be impacted at the same time and what can be done to limit failures.<p>Besides the technical aspects that flight is an impressive example of resilience and skill. Bringing that plane down to the ground in nearly one piece was essentially impossible and a one in a million chance in itself.<p>[1] <a href="https://en.wikipedia.org/wiki/United_Airlines_Flight_232" rel="nofollow">https://en.wikipedia.org/wiki/United_Airlines_Flight_232</a>
Airlines operate to a much stricter standard than one in a million. If one in a million flights ended in a fatal crash, the US alone would see about 3 airline passenger deaths <i>per day</i> on average. The actual average over the past 10 years is under 0.02 deaths per day.<p>It's true that you can never get to zero. There's always a chance of some catastrophic failure. The lesson of modern airline safety is that you can get extremely close to zero by carefully analyzing and learning from the failures, which is exactly why these thorough investigations are done. The lesson from UA232 was to make sure one failure can't take out all of the hydraulic systems.<p>In this specific instance, "the engine fell off and took out another engine, leaving the aircraft with insufficient power to climb" is definitely not in the realm of "probabilities will get you eventually." It's very much in the realm of a mechanical failure that should not happen, combined with a bad design flaw that turns that failure from a mere emergency into pretty much guaranteed death.<p>Cargo is held to a lower standard than passenger service, but I suspect this will still spell the end of the DC-10 and MD-11, at least in the US. Engines <i>will</i> fail, and for an aircraft of this size, that needs to be survivable in all phases of flight just for the safety of people on the ground.
> The lesson of modern airline safety is that you can get extremely close to zero by carefully analyzing and learning from the failures, which is exactly why these thorough investigations are done.<p>I have heard it said that "every air safety rule is written in blood."<p><a href="https://www.cnn.com/2024/01/02/travel/tokyo-plane-crash-safety-rules-analysis-intl" rel="nofollow">https://www.cnn.com/2024/01/02/travel/tokyo-plane-crash-safe...</a>
If the engine had just failed, they would very likely have been fine. Experienced crew, would likely have handled it. But the engine came off the wing, and then another engine was damaged. At that point there was no recovery possible.
This is understating it. Any minimally competent crew should be able to handle a single engine failure on takeoff (in a normal scenario, not this one). It’s absolutely within the performance envelope of the aircraft and is something that crew train for. If pilots were not routinely able to handle this kind of failure, we’d see a lot more crashes.
> Airlines operate to a much stricter standard than one in a million. If one in a million flights ended in a fatal crash, the US alone would see about 3 airline passenger deaths per day on average.<p>I think you conflated flights (several 10Ks per day) with passengers (several million per day).<p>One in a million flights is one accident every few decades.<p>> at least in the US. Engines will fail<p>As per the report, this appears to be a structural failure, not an engine failure.
If randomly distributed, one in a million flights crashing and killing all passengers means that one in a million passengers dies.<p>The US sees about 25,000 airline flights per day, or around 9 million per year. So with one in a million flights crashing, we'd expect roughly 9 crashes per year.
Even if they end the grounding of the MD-11/DC-10 I'd be shocked if any airlines still using them will continue to use them.<p>Seems like the risk/reward just isn't really there for the few of them still in service, and if anything happened it would be a PR nightmare on top of a tragedy.<p>Definitely an end of an era!
UPS and FedEx each have around 25 MD-11s, Western Global has 2 I think, the Orbis Flying Eye Hospital is an MD-10, some cargo airline in Botswana has one, and 10 Tanker has some DC-10 firefighting tankers.<p>That’s the entire worldwide fleet.
Given that the report only mentioned a single other seemingly related accident in 1979 I am not sure that objectively this is a reason to discontinue flying these planes. The fact that these planes have been in service since the early 70s is a testament to their safety and reliability in itself. Of course public perception, especially with the videos of huge fireballs from hitting one of the worst possible locations, might put enough pressure on airlines to retire the planes anyway.<p>I agree on the end of an era. Hearing something else besides just Airbus- or Boeing-something always gives me a bit of joy. Even though MDs and DCs are of course Boeings in a sense now as well.
I think that the Mad Dogs only exist as freighters (~or their derivative KC-10 tankers~-Edited to correct that they retired last year) these days. I think the last pax service for any of them was over a decade ago.<p>And air freight just gets a lot less public attention, I think they are going to keep flying them if they don't get grounded.
Mad dogs are MD-80s.
The airforce retired the KC-10 in 2021.
The KC-10 went out of service last year. None are operating.
Yeah, but DC-10 based tankers for wildfire fighting were still flying until the recent grounding: <a href="https://en.wikipedia.org/wiki/DC-10_Air_Tanker" rel="nofollow">https://en.wikipedia.org/wiki/DC-10_Air_Tanker</a><p>(Blancolirio points out that the DC-10 tanker is what they modernized to relatively recently -- before that they were flying even more dangerous WW2 airframes for firefighting.)
Damnit, I knew that! Just forgot it in the moment.
Most of the DC-10s in service in the US are used for fire fighting.
And with Omega Air, for contracted air refuelling<p><a href="https://www.omegaairrefueling.com/" rel="nofollow">https://www.omegaairrefueling.com/</a>
Yes, but there are many MD-11's still flying as freighters. There are four fire-fighting DC10's out of ~8 still flying, but there are 25 Mad Dogs (MD-11) at UPS, 38 with FedEx, and Western Global has 4, so there are plenty of MD-11F's around.
Here are 4 of them. All grounded now.<p><a href="https://www.10tanker.com/gallery" rel="nofollow">https://www.10tanker.com/gallery</a>
Airlines haven't been using them, or at least not 1st world airlines. Just freight and wilderness fire fighters.
Most of them are used as cargo planes. Which have dramatically lower usage rates than passenger planes (and they are retired passenger planes)<p>Sucks for the pilots flying them for sure tho.
> <i>Grounding all MD-11s and DC-10s is a major move</i><p>Not really. There are zero left in passenger service, they pretty much only serve cargo now.
Captain Steeeve thinks it was actually the starboard engine that also failed due to evidence of compressor stalls in some of the footage<p><a href="https://youtu.be/CmXLQHhUtv4?t=499" rel="nofollow">https://youtu.be/CmXLQHhUtv4?t=499</a>
It wasn't just one engine off, aside from possibly damaging tail engine you also have damage to the wings and control surfaces that might've just not got enough lift because of that.
> EDIT: It seems there was damage to the engine in the tail, even though this was not specified in the preliminary report, likely because it has not been sufficiently confirmed yet.<p>Yes, the initial videos were showing the tail engine flaming out. And in the 1979 crash, the engine also severed hydraulic lines that hold the slats extended. So they folded in due to the aerodynamic pressure, essentially stalling the wing.
Based on the original descriptions of the crash, I assumed the engine fell off.<p>From the photos, it’s clear it went up over the wing and impacted the fuselage with a (at least) minor explosion, which would have thrown foreign objects into the third engine in the tail for sure.<p>Losing 2/3 of the engines isn’t survivable on takeoff for this class of plane, at the weights they were at.
> I assumed the engine fell off<p>It's an engine - the thing pushing the entire plane forwards. Provided it is running (and at takeoff that's <i>definitely</i> the case), an engine being liberated from its plane suddenly has a lot less mass holding it back, so the logical thing to do is to shoot forwards. And because the wing is attached to the upper side of the engine, anything short of an immediate failure of <i>all</i> mounting points is probably also going to give it an upwards trajectory.<p>Add in air resistance, and you get the "swing across the wing and back" seen in the photos.
Sure, but if the engine grenades it can take it’s mounts with it and <i>not</i> shoot off like a bottle rocket in front of and over the plane, dropping down and under the plane instead (or even just sit there). Same with a compressor stall, or whatever.<p>It’s clear from the photos this wasn’t the engine failing at all, and in fact the engine kept producing a ton of thrust (probably until it ran out of fuel as it pulled it’s fuel line apart while departing the wing), and instead the thing that is supposed to be so incredibly strong that it restrains all this chaos failed.<p>Which is a pattern in this family of aircraft, but definitely <i>not</i> a common or normal thing in general eh?<p>Most aircraft, the engine stays with the airframe even if it turns into a giant burning pile of shrapnel and dead hopes and dreams.
Engine pylons are actually usually designed to fail in a particular way to ensure the separation happens as safely as possible; obviously that didn't happen here, which will probably be something the NTSB will have to investigate why.<p>The up and over is usually actually the safer direction I think? But in this case it also moved laterally, which is possibly what fouled the tail engine and made it unrecoverable. Will be interesting to see the final report.
Fully functioning engines departing from aircraft isn't common but it's not unheard of either. Off the top of my head it's happened a few times on the 747 and 737.
Adding summary analysis from AVHerald [0]<p>[0] <a href="https://avherald.com/h?article=52f5748f&opt=0" rel="nofollow">https://avherald.com/h?article=52f5748f&opt=0</a>
"Your IP address 104.28.103.15 has been used for unauthorized accesses and is therefore blocked!
Your IP address belongs to Cloudflare and is being used by many users, some of which are hackers and hide behind the cloud/proxy to avoid being tracked down. Hence the automatic defense closed access from that IP address.<p>"Make sure to not use a proxy/cloud service for visiting AVH (e.g. Apple Users turn off your private relay) but your native IP address, then access should be possible without a problem again."<p>No thank you, AV Herald.
> On the aft lug, on both the inboard and outboard fracture surfaces, a fatigue crack was observed where the aft lug bore met the aft lug forward face. For the forward lug's inboard fracture surface, fatigue cracks were observed along the lug bore. For the forward lug's outboard fracture surface, the fracture consisted entirely of overstress with no indications of fatigue cracking<p>If I'm parsing this correctly, they're saying that fatigue cracks should have been visible in the aft pylon mount, and that the forward mount was similarly fatigued but showed no damage on the outside?
> If I'm parsing this correctly, they're saying that fatigue cracks should have been visible in the aft pylon mount, and that the forward mount was similarly fatigued but showed no damage on the outside?<p>If you can get to the report, Figure 7 shows the left pylon, with the forward and aft lug enlarged in the inset. Both lugs cracked on two sides. They're saying both cracks on the aft lug as well as the inboard crack on the forward lug were observed to be fatigue cracks, but the forward lug outboard fracture was observed to be entirely a stress crack.<p>Outboard and inboard are just away from and towards the center of the plane. On the left pylon, that's left and right, respectively. So, it looks like the left side crack in the forward lug developed from overstress, but the other three cracks were from fatigue. My expectation is that fatigue should be apparent upon the right kind of inspection, if timely, even if the metal has yet to fracture.
It sounds like the aft lug failed first, and then the not quite as compromised forward lug failed in overload.
Link doesn't seem to be available now:<p>> Page not found<p>> The page you're looking for doesn't exist.
I found a link to the PDF that seems to work <a href="https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/201958/pdf" rel="nofollow">https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/G...</a><p>Also in case that link stops working I got it from this page <a href="https://www.ntsb.gov/investigations/Pages/DCA26MA024.aspx" rel="nofollow">https://www.ntsb.gov/investigations/Pages/DCA26MA024.aspx</a><p>EDIT: nevermind immediately after posting this comment it is now giving a 403 error
If anyone saved a copy locally, it'd be great if you could share it somewhere. (I, for once, did not, and the tab is gone now :-/ ).
Appreciate the transparency in these reports. The technical breakdowns always highlight how complex aviation safety is.
Revised URL -<a href="https://www.ntsb.gov/investigations/Documents/DCA26MA024%20Preliminary%20Report.pdf" rel="nofollow">https://www.ntsb.gov/investigations/Documents/DCA26MA024%20P...</a>
TIL about this eerily similar DC-10 crash in 2011:<p><i>Shortly after liftoff, 20 feet (6.1 m) above and 7,000 feet (2,100 m) down the runway, the No. 2 engine separated from the wing and struck the No. 1 engine's inlet cowling, causing it to produce drag and reduced thrust. Even with full right aileron and rudder, the plane started to descend and drift to the left. The captain lowered the nose and leveled the wings, which was followed by the plane making multiple contacts with the runway. After touchdown, the plane drifted left and departed the runway, crossing a taxiway before coming to rest in a saltwater marsh. A fire erupted which consumed the top of the cabin and the cockpit. All three crew members survived.</i><p><a href="https://en.wikipedia.org/wiki/Omega_Aerial_Refueling_Services_Flight_70" rel="nofollow">https://en.wikipedia.org/wiki/Omega_Aerial_Refueling_Service...</a><p>Obviously the DC-10 is not the MD-11, but the MD-11 is a direct descendant, including the trijet configuration.
The article you linked is talking about a 707, not a trijet. In particular, engine 2 on the MD-11 is the tail engine, not a wing engine.
...is this a bot comment? The accident you linked is very clearly of a Boeing 707, which has zero relation to a DC-10 and is most decidedly not a trijet.
Link to page that links to the report, as of now: <a href="https://www.ntsb.gov/investigations/Pages/DCA26MA024.aspx" rel="nofollow">https://www.ntsb.gov/investigations/Pages/DCA26MA024.aspx</a>
surprised to see typos in aviation terms and acronyms: ADS-8 (page 3) and 747-BF (page 5)
Swapping B and 8 in both cases, which is typically something that happens with OCR. Weird.
Reminds me of xerox scanner fun, maybe someone scanned it to pdf to publicise?<p>Nontheless the pdfs have been replaced and the newer ones don't seem contain these errors anymore.
pretty weird...<p><pre><code> NATIONAL TRANSPORTATION SAFEN'BOAFID
:J11...:i= of ArutiOn SMel@LA5 301
A.,r Tral1C.IYU';UQlt-Ort!!
NTS,B ri@ss @at.Joo JurtJer
DCA26 22\C2<</code></pre>
That's terrible. If the NTSB had flagged this flaw before then someone failed with an inspection regime or maintenance.<p>The NTSB doesn't ever accept the "sometimes bad things happen, shrug" excuse and kudos to the professionals there.
A commenter in HN thread covering the initial crash mentioned that the left engine detaching might have been the cause <a href="https://news.ycombinator.com/item?id=45821537">https://news.ycombinator.com/item?id=45821537</a><p>The referenced AA Flight 191 is shockingly similar. It makes me wonder if aviation really is back sliding into a dangerous place.
40 years between severe accidents is fine in terms of expected failures. It's also not a good comparison because in the 70s maintenance crew were using a forklift to remive engines, improperly stressing the engine pylon. This was done as a shortcut
I don't know if it's "sliding back" as much as it is that this plane is also fundamentally from the 1970s.
Are you referring to AA 191 in 1979? That seems like low enough frequency event to not be worried about it.<p>The murder suicides in the last few decades seem more concerning.
Rather the opposite: if the cause is similar to AA 191, why weren't the actions taken after AA 191 to prevent a repeat effective? If we can get a repeat of <i>that</i> incident, what's preventing the industry from repeating the mistakes from all those <i>other</i> incidents from the past decades? Why aren't they learning from their past mistakes - often paid for in blood?
I understood the post I responded to to be referring to the cause as the engine detaching from the same type of plane, not the root cause for why the engine detached. Per the “investigation section” in the wikipedia article, I would be surprised if it was the same root cause:<p><a href="https://en.wikipedia.org/wiki/American_Airlines_Flight_191" rel="nofollow">https://en.wikipedia.org/wiki/American_Airlines_Flight_191</a><p>I assume the erroneous maintenance procedures that led to the loss of AA191 were rectified a long time ago.
>rectified a long time ago.<p>There's no such thing as "This is fixed forever". If lax maintenance oversight has led to companies re-introducing known dangerous maintenance procedures or departing from known good ones, then we will be back in the 70s in terms of airplane safety and people will have to die again to relearn those lessons.<p>Someone's always trying to claw you in the less safe direction. It's a constant battle to not regress.<p>But IDK, hopefully this plane just got some sort of "unlucky" about fatigue somehow, and it doesn't have far reaching consequences.
> The referenced AA Flight 191 is shockingly similar. It makes me wonder if aviation really is back sliding into a dangerous place.<p>I think it's cut throat capitalism at its best. Surely it was much too safe before, let's see how far back we can scale maintenance on the operations front but also how far back can you scale cost during development and production and then see where it takes us. If that changes the risk for population from 0.005 to 0.010, the shareholders won't care and it's great for profits.<p>I think we can see both but especially the latter with Boeing.
The entire MD-11 project was a budget-limited rush-job to try to capture some market share before the A340 and 777 came into service.<p>It produced an aircraft that failed to meet its performance targets, was a brute to fly and was obsolete the moment its rivals flew.<p>Douglas* by the early 1990s was a basket-case of warmed-over 1960s designs without the managerial courage to launch the clean-sheet project they needed to survive.<p>* as a division of MDC
I was under the impression that a plane could deal with an engine failure at any point in flight - including during takeoff.<p>Dropping an engine entirely is a similar situation to a failure - with the benefit that you now have a substantially lighter if imbalanced aircraft.<p>Should this plane have been able to fly by design even with an engine fallen off?
El Al 1862 was another flight [1] that had an engine fall off, taking another engine out with it. The pilots managed to fly around for a few minutes and attempt a landing, but there was too much structural damage.<p>It doesn't seem aircraft are designed to survive these types of catastrophic failures.<p>[1] - <a href="https://en.wikipedia.org/wiki/El_Al_Flight_1862" rel="nofollow">https://en.wikipedia.org/wiki/El_Al_Flight_1862</a>
They seem to have lost the tail engine too. Yes, it is a significant problem that engine failures aren't independent, so trijets are kind of a bad design.
Not only did it happen at the worst possible moment, it took out a second engine on it's way out and over the plane. Two engines should've been enough to get off the ground and potentially land the plane, but one engine on a trijet isn't enough.
It nuked the tail engine so actually TWO engines failed.
From the wing down I assumed it may have depended if the engine coming out unintentionally means redundant hydraulic lines and mounts are also getting disconnected causing a complete loss of control <i>not that it would have helped much at that point beyond minimizing ground damages</i>.
Yes, but when the engine came off, it also disrupted the third engine in the tail. Can't take off in this model with 2 out of 3 engines gone.
Yeah, pilots I know saw puffs of flame coming out of the engine, and said that that's a tell-tale sign of a compressor stall. Which could have been caused by debris from the separating left engine striking the turbine.
Even if they had the thrust (doubtful) there wouldn't be enough lift with a gaping hole in the leading edge of one wing.
The video of the aircraft crossing the road wings level (well after #1 separated) and maintaining relatively controlled flight until too much energy bled off suggests to me the aircraft was likely to be controllable to a landing if sufficient thrust was available.
..for a moment. If there was sufficient hydraulics damage it might've stopped being controllable.<p>And even if they worked the fire might've damaged the plane enough.<p>For example <a href="https://www.faa.gov/lessons_learned/transport_airplane/accidents/N1819U" rel="nofollow">https://www.faa.gov/lessons_learned/transport_airplane/accid...</a><p>when they lost tail engine, all of the hydraulics went down
To be clear, we don't yet know if the UPS flight lost hydraulics or not. There are several somewhat redundant hydraulic systems.<p>(Also, as a result of the Sioux City crash you linked, there were several ADs issued requiring changes to hydraulics in these airframes.)
I thought the leading edge of the wing was intact in this case? I may be misremembering.
Yeah, if they had had more altitude, I would guess that this would have looked even more like the AA 191 crash from 1979, with the left wing stalling and causing a roll and pitch down.<p>That in turn reminds me of the DHL flight out of Baghdad in 2003 that was hit by a missile [0]. Absolutely amazing that they managed to keep it together and land with damage like that.<p>[0] <a href="https://en.wikipedia.org/wiki/2003_Baghdad_DHL_attempted_shootdown_incident" rel="nofollow">https://en.wikipedia.org/wiki/2003_Baghdad_DHL_attempted_sho...</a>
An important factor in AA 191 is that the engine leaving did significant damage to the hydraulic lines in that wing - including those for the leading-edge slats. At the time the plane was not equipped with any mechanism to keep the slats extended, so after hydraulic pressure was lost airflow over the wings caused them to retract, which significantly lowered that wing's stall speed.<p>After AA 191 the DC-10 was equipped with a locking system: loss of pressure now results in the slats getting stuck in their current position. The MD-11 will undoubtedly also have this system, so a direct repeat of AA 191 is unlikely.
It didn’t fall off, it flew up and then landed back on the plane.<p><a href="https://www.reddit.com/r/aviation/comments/1p276xx/ntsb_issues_the_preliminary_report_for_its/?utm_source=share&utm_medium=mweb3x&utm_name=mweb3xcss&utm_term=1&utm_content=share_button" rel="nofollow">https://www.reddit.com/r/aviation/comments/1p276xx/ntsb_issu...</a>
This engine didn’t just fail, it failed catastrophically and took out another engine with it.
I'm surprised at how many years the plane went without having that part inspected. It looks like the failure was due to fatigue cracks, but the last time the part was inspected was in 2001?
I believe the part was at least visually inspected in 2021:<p>> A review of the inspection tasks for the left pylon aft mount found both a general visual inspection (GVI) and a detailed visual inspection of the left pylon aft mount, required by UPS's maintenance program at a 72-month interval, was last accomplished on October 28, 2021.
I’m seeing 2021 on page 10 - an I missing something?
The surveillance video mentioned in page 2 -- from which the series of still images are shown -- is that available publicly?
As I told my friends, this preliminary report <i>annoys me</i>. It <i>annoys</i> me for the same reason it seemingly <i>annoys</i> the NTSB: American 191 is nearly identical on the surface, right down to the engine detachment and resultant loss of the aircraft, in almost the exact same spot on the airframe, ~45 years later.<p>Needless to say they’re going to be scrutinizing everything to determine what the cause is and the sequence of events that created the accident, but I also suspect everyone involved is just as <i>annoyed</i> at this as I am, given that this exact situation <i>should</i> have been fixed already.<p>* <i>Annoyed</i> = seething rage
Not an aviation expert, nor I want to be one, but the images look pretty intense.
It's just time to kill the MD-11 entirely. These 3-engine aircraft are too risky to continue flying.
McDonnell-Douglass right there that's where the problems start.
Gyroscopic precession took the left engine to the right. In AA 191 the right engine departing to the right did not affect the center engine. Sadly the engine failure procedure at the time mandated slowing down to V2 which was below the stall speed with slats retracted. There's now revised procedure and hydraulic fuses.<p>I expect all remaining aircraft will be getting new rear pylon lugs with shortened inspection intervals - provided the replacement cost is below the value of continued usage.