Originally explained on the blancolirio channel on YouTube -
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.
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.
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.
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.
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?
TIL about this eerily similar DC-10 crash in 2011:
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.
As I told my friends, this preliminary report annoys me. It annoys me for the same reason it seemingly annoys 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.
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 annoyed at this as I am, given that this exact situation should have been fixed already.
Actually, the two accidents are only superficially similar, and there is no basis for saying that "this exact situation" should have already been fixed.
And no, this is not just pedantry. A bulkhead fracturing from impact damage and its mounting point failing from fatigue cracking are nowhere near the same thing, even if they might lead to the same outcome.
I’m not sure where you’re getting these conclusions from, because AA191 was an issue where the engine separated from the wing and took hydraulics with it, creating a sequence of failures that resulted in the loss of the airframe. The UPS flight also had a separation of the engine from the wing and created some sequence of events that resulted in the loss of the airframe, but they’ve made it very clear in the report that the how and the why are still very much open questions.
My point - and from what I see in the report, a grievance shared by the NTSB, given their citation of AA191 - is that both aircraft come from the same lineage (DC-10/MD-11), the same manufacturer (McDonnell-Douglas, now Boeing), had the same failure (engine separating from wing assembly during takeoff roll), and with all involved parties throwing up their hands and swearing they followed all the rules and maintenance schedules.
And that’s too many coincidences to just dismiss outright from the get-go.
> I’m not sure where you’re getting these conclusions from
I'm not sure how to say this in a way that does not come across as rude, and I apologise in advance if it does, but I got those conclusions (in actuality, statements of fact) from actually reading the reports and understanding the terms and diagrams in them, where it is pretty clearly detailed that the sequence of events does not start with engine separation? You can quite literally read for yourself in both reports (as opposed to relying on a shallow pop culture understanding of the parts involved) the differences in the initial damage to the pylon.
Like, it is understandable that not everyone is an aviation nerd, but it is quite a bit silly to go "the engine separated so they're the same thing which should have been fixed by now". Or to put it another way - do you drive a car? Do you understand the car you drive, as well as cars in general - do you understand that e.g. there are many different things that can cause a flat tyre and so it makes little sense to point to two road accidents as being the same because they both "start" with a flat tyre, even if they involve the same vehicle + tyre manufacturer?
> My point - and from what I see in the report, a grievance shared by the NTSB, given their citation of AA191
I feel quite comfortable in saying that you are projecting your grievance on the investigating body, actually, especially considering that you've manufactured a narrative out of whole cloth where "all involved parties [threw] up their hands and [swore] they followed all the rules and maintenance schedules". In reality, the investigation detailed within about a month that American Airlines (as well as Continental Airlines and United) was most decidedly not following the maintenance guidance from McDonnell Douglas, which had directly led to the fracture of the aft pylon bulkhead (again, a different part from the one that failed in the UPS crash). But of course, that does not fit into the easy-to-swallow "McDonnell Douglas bad" story that people prefer over actually reading and understanding these reports for themselves.
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.
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.
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)
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[ 0.31 ms ] story [ 74.0 ms ] thread[0] https://avherald.com/h?article=52f5748f&opt=0
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.
The referenced AA Flight 191 is shockingly similar. It makes me wonder if aviation really is back sliding into a dangerous place.
Dropping an engine entirely is a similar situation to a failure - with the benefit that you now have a substantially lighter if imbalanced aircraft.
Should this plane have been able to fly by design even with an engine fallen off?
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.
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.
https://youtu.be/CmXLQHhUtv4?t=499
> Page not found
> The page you're looking for doesn't exist.
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.
https://en.wikipedia.org/wiki/Omega_Aerial_Refueling_Service...
Obviously the DC-10 is not the MD-11, but the MD-11 is a direct descendant, including the trijet configuration.
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 annoyed at this as I am, given that this exact situation should have been fixed already.
* Annoyed = seething rage
And no, this is not just pedantry. A bulkhead fracturing from impact damage and its mounting point failing from fatigue cracking are nowhere near the same thing, even if they might lead to the same outcome.
My point - and from what I see in the report, a grievance shared by the NTSB, given their citation of AA191 - is that both aircraft come from the same lineage (DC-10/MD-11), the same manufacturer (McDonnell-Douglas, now Boeing), had the same failure (engine separating from wing assembly during takeoff roll), and with all involved parties throwing up their hands and swearing they followed all the rules and maintenance schedules.
And that’s too many coincidences to just dismiss outright from the get-go.
I'm not sure how to say this in a way that does not come across as rude, and I apologise in advance if it does, but I got those conclusions (in actuality, statements of fact) from actually reading the reports and understanding the terms and diagrams in them, where it is pretty clearly detailed that the sequence of events does not start with engine separation? You can quite literally read for yourself in both reports (as opposed to relying on a shallow pop culture understanding of the parts involved) the differences in the initial damage to the pylon.
Like, it is understandable that not everyone is an aviation nerd, but it is quite a bit silly to go "the engine separated so they're the same thing which should have been fixed by now". Or to put it another way - do you drive a car? Do you understand the car you drive, as well as cars in general - do you understand that e.g. there are many different things that can cause a flat tyre and so it makes little sense to point to two road accidents as being the same because they both "start" with a flat tyre, even if they involve the same vehicle + tyre manufacturer?
> My point - and from what I see in the report, a grievance shared by the NTSB, given their citation of AA191
I feel quite comfortable in saying that you are projecting your grievance on the investigating body, actually, especially considering that you've manufactured a narrative out of whole cloth where "all involved parties [threw] up their hands and [swore] they followed all the rules and maintenance schedules". In reality, the investigation detailed within about a month that American Airlines (as well as Continental Airlines and United) was most decidedly not following the maintenance guidance from McDonnell Douglas, which had directly led to the fracture of the aft pylon bulkhead (again, a different part from the one that failed in the UPS crash). But of course, that does not fit into the easy-to-swallow "McDonnell Douglas bad" story that people prefer over actually reading and understanding these reports for themselves.
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.
The NTSB doesn't ever accept the "sometimes bad things happen, shrug" excuse and kudos to the professionals there.