6 ms·
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 engi
by philip1209 11mo ago
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.
- testplzignore 11mo agoMaybe stupid question: Why not have the #1 engine spin in the opposite direction so that it doesn't go towards the fuselage?
- captaincrowbar 11mo agoBecause making every jet engine in two different models would make them a lot more expensive. It would also cause maintenance issues because of non-interchangeable parts.
- cj 11mo agoThere might be some truth in that. But the report doesn't confirm that theory.
- philip1209 11mo agoI'm presenting it "useful not true" - not an RCA.
- rconti 11mo agoWhat theory? That the mount failed? Or the rotation of the engine in the photos going up and over the fuselage? It seems like both are true, but doesn't necessarily prove WHY the mount failed.
- cj 11mo agoThat the engine was flung into the fuselage due to gyroscopic forces.
- inejge 11mo agoWell, some force flung it inboard and above the fuselage (gods, that CCTV stills sequence.) Knowing that the engine rotates CCW, there are not many candidates.
- JumpCrisscross 11mo ago> Knowing that the engine rotates CCW, there are not many candidates There are lots of candidates for a failing engine yeeting itself in any direction.
- inejge 11mo ago> There are lots of candidates for a failing engine yeeting itself in any direction. For the precise trajectory, certainly; for the general direction, not so much. Could you describe a combination of forces that would have thrown that engine to the left of the direction of travel? (We're talking about this accident, not any engine anywhere.)
- JumpCrisscross 11mo ago> Could you describe a combination of forces that would have thrown that engine to the left of the direction of travel? Foreign object gets yeeted to the right. Internal component gets yeeted to the right. Engine exploded on its right side. I think each of those is more likely than gyroscopics since the engine went to the left. Not left and up.
- inejge 11mo ago> [...] the engine went to the left. Not left and up. Whatever you're describing, it's not this accident. Over and out.
- stackghost 11mo agoThis is a preliminary report. Its purpose is to present initial evidence/information. The final reports are always much more comprehensive.
- londons_explore 11mo agoI assume such forces are calculated and added in when deciding hot thick to make those mounting brackets.
- baggy_trough 11mo agoYes, 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.
- loeg 11mo agoYes, 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.
- shtzvhdx 11mo agoAluminum has limited loading cycles
- dreamcompiler 11mo agoI'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.
- CoastalCoder 11mo agoWouldn't that be true of all cast metal objects? Or are some metals impervious?
- deleted 11mo ago[deleted]
- harshreality 11mo agoNo; roughly, yes. Based on the crystal structure of the metal, fatigue works differently. > 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. https://en.wikipedia.org/wiki/Fatigue_limit https://en.wikipedia.org/wiki/Fatigue_limit
- PunchyHamster 11mo agoI think far simpler explanation is "the back part failed first and engine is making thrust so it just flipped over on now-hinge mounting
- mrb 11mo agoYup. 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.
- dreamcompiler 11mo agoAmerican 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.
- jacobgkau 11mo agoA 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.
- dreamcompiler 11mo agoYes, 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] 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. [0] https://en.wikipedia.org/wiki/American_Airlines_Flight_191#Engine_separation https://en.wikipedia.org/wiki/American_Airlines_Flight_191#E...