Comment by PunchyHamster
20 hours ago
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
20 hours ago
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.
Yes, and that lateral movement is very important since the debris seems to have caused at least one other engine to the right to fail as well.
From a failure analysis perspective that is much less relevant though. The first failure was the rear engine mount if it had been a secondary failure it would have been deformed first and then broken, and it clearly is not. It just tore in half on one of the four connections and then the rest deformed slightly due to overstress.
2 replies →
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.
Admiral Cloudberg has a great article on AA 191 that covers exactly what happened: https://admiralcloudberg.medium.com/rain-of-fire-falling-the...
Ironically, AA flight 191 could have been salvageable, because the engine detaching didn't start a fire. However, it led to loss of hydraulic pressure on that wing, which led to the flaps/slats retracting on just the left wing, which led to the plane becoming uncontrollable. After that accident, the DC-10 was retrofitted with hydraulic fuses to prevent something like this happening again. Unfortunately, that didn't help the UPS crew, because in their case, the detachment caused more damage to the wing...
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.
13 replies →
The picture of that part that is torn into two pieces certainly seems to suggest so, that's a clean break, not an overstressed part deforming and then breaking.
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.