I didn't know you were an FAA investigator. Good to know!

Also, where is he getting that the fan blade ricocheted forward on SWA1380? That didn't happen. Large chunks of the failed fan blade in that incident were lodged inside the engine, not flung forward. He even then says that it was determined to be a contained engine failure, which is correct! There were not fan blade pieces flug forward, that is what they mean by contained.

I had to stop there.

You're using research from a Rolls Royce engine on an Airbus vs a 777 with a P&W, 2 different platforms probably using 2 different technologies.

Yes, the engines are pulled backwards. What loads do you think are on the tips of these fan blades.

Yes, there is huge deformation. The amount of energy imparted on the casing from these blades is mindblowing. Of course there is huge deformation. Where else do you think the crazy energies go? That is how things work.

You don't need my expertise to know that. Here is a youtube video showing both the blades being pulled backwards and the crazy deformation:
If you want I can explain more the dynamics here and the engineering of systems for fan blade out events.

OK. you're an expert. What I meant to say is:

I did not see the cylinder containing the blades deforming laterally. Sure, the engine 'breathes' behind it, but the cylinder (titanium?), doesn't deform significantly. That would shear all the blades right off.

Basic physics dictates, and the slow mo actually shows, that the exploding blades do move laterally and slightly forward first, not backwards.
Engine pulls backwards, blades get pulled forward relative to the engine. Basic physics.
I mean, they design the blade containment cylinder to extend forwards, but not significantly past the fan blade stage.

So its totally feasible and normal, that the blades could just separate/slice off the cowling at the front of the cylinder? No?
Am I totally wrong on this?
Serious question.

Anyways, doesn't matter. What do you think? Ingestion (unlikely), or more likely a hairline fracture not detected during inspection (x-rays)?.

For sure, this time it's not P&W or BOEING's fault.
.

I don't know the containment design on the P&W engines, but you can get some hints from the photos on the thread. There is generally a large amount of composites in the design, lots of aramid fibers. You can see what looks like a aramid honeycomb in the picture.

No, that is not basic physics here. Yes, the blades do have a load pushing forward, but it is not that simple. These are beams in bending, so that forward load at the place where the blade breaks is moment. This causes the piece of the blade that breaks not to have a forward vector, but a rotation. Going back to pencil example, you will see this. So that is where that energy stored up due to the loading of the blades goes, not forward, but a rotation. Then you have the massive airload on these pieces, that will then push the piece backwards. So while part of the blade does move forward, the blade is not shot forward. It just rotates until it is stopped.

This is why it won't stay in the correct orientation to slice the leading edge, because the piece is rotating on that short axis. For it to hit the cowl like that it would also have to present the greatest surface area to the incoming air, which would make it very hard to keep going forward. So slicing the leading edge like that seem so incredibly unlikely. The damage seen is due to the loads that cause it to be ripped off. And also hitting the ground from thousands of feet in the air.

What you are also thinking is the containment going forward of the blades is actually mostly boundry layer control and some noise insulation.

See South West Airline 1380:



Notice the similar damage to the engine? That is was due to the fan blade out event also. The damage done to the exterior was due to the extreme loads and deflections on the engine casing from the fan blade out event. All of those exterior parts are attached to structure that deformed under the loads and failed. Or structure that unlatched a panel that can open for service.

I don't know why the fan blade failed. Could be all sorts of things. Probably not some ingestion, they are designed to handle some big birds (strangely heavier birds than empennage is designed for, I guess heavy birds will not hit the tail for some strange reason, always seemed like an odd regulation to me). Could be a crack not detected. Or could be a crack that grew much larger following inspection. Or some weird corrosion. All sorts of things could cause that.

I do think we are going to see some regulations in the future to further prevent these fan blade out events from causing parts to depart the airplane. It is just that the loads are so crazy and so many ways for it to fail it is going to be hard.

They don't need regulations on the designs or strengths. This is a known flaw with any turbofan and you can't design them any better than this. Instead you monitor lifetimes and inspect and take them out of service prior to failure. This was most likely a failure of United to properly inspect or monitor the fans (maybe due to operational interruptions from Covid) or it was a 6 sigma crack growth.

A great vid with the cockpit/tower recordings, these pilots have ice water in their veins.
.. https://www.youtube.com/watch?v=q5Wler87pwY

Anyone who travels very much on airlines in the United States soon gets to know the voice of the airline pilot . . . coming over the intercom . . . with a particular drawl, a particular folksiness, a particular down-home calmness that is so exaggerated it begins to parody itself . . . the voice that tells you, as the airliner is caught in thunderheads and goes bolting up and down a thousand feet at a single gulp, to check your seat belts because ‘uh, folks, it might get a little choppy’ . . . Who doesn't know that voice! And who can forget it—even after he is proved right and the emergency is over.