rb860

I've never seen anything quite this dangerous from a commercial flight before. Experts: what was the actual likelihood that the shaking seen in the passengers video would have further damaged the plane to the point of water crash?

TA

Definitely looks like some reduced power at least:

Edited based on information later in this thread -- the engine out issue happened in the last 40 mins of this flight:

The midflight decrease and increase was part of the normal cruise.

chermorg

Likely very low. If the shaking got bad enough with the engine on, the pilots would have always had the option to turn it off. Twin engine planes flying over the ocean to Hawaii are rated to fly on one engine for much longer than the distance from midpoint of route to Hawaii or back to the west coast - thus it would have been totally fine to fly it on one engine to Hawaii. Would've made landing a little more risky, but they'd be able to get to land most likely.

WineCountryUA

This
additionally, planes are constructed and tested to take a significant amount of stress -- aircraft structures are probably among the most over-designed mechanical structures.

sexykitten7

Wow. And to think I was concerned about a patch of turbulence last month!

Reminds me of this wonderful twilight zone episode in which a gremlin attempts to remove a cowling from a jet. (While you cannot open the window during flight, apparently it is possible to balance on the wing.) And they actually used the word cowling!

phil94028

As others have said this is how it is supposed to work. Fuel planning takes this into account to get you to somewhere and land safely one engine inoperative. Obviously the engine would be shut down. This kind of failure is designed in to be tolerated and trained for, even in the most critical stages of takeoff.

There would be huge amounts of vibration if any of the cowl got pulled into the engine and damaged a fan blade. The engine windmills with the airflow even shut down and is way out of balance. What is reported may just be the airflow over the now, not so aerodynamic, fan/engine core. This would probably still seem like a lot for passengers but neither that safety critical.

It may turn out that un-contained blade or fan blisk failure tore up the cowl in the first place. This is dangerous. There is a lot of protection and is part of certification, so is not supposed to happen. Sure the report on it will be interesting and as usual improve safety.

For the curious, this kind of stuff gets discussed over at pprune which is more pilot and technically oriented.

FlyTheFriendlyMonkey

Has there ever been an engine that sheared off a commercial flight per the anti-vibration design specs?

frebay

I remember watching air disasters where a 747 had an engine shear off (as intended, but it hit the other engine, and the plane crashed.

edit: found it. it was actually a cargo plane.
https://en.wikipedia.org/wiki/El_Al_Flight_1862

"2 engines shearing off. The number 3 engine sheared off shortly after take-off due to metal fatigue related failure of the fuse pins. After separation, the number 3 engine hit the number 4 engine, shearing it off as well."

In The 216

seawolf

The vibration in the Twitter video doesn't look that severe. I think many here have seen more violent shaking during heavy turbulence.

Maxwell Smart

Do you mean relative to other aircraft systems or to other structures in general?

Factors of safety for aircraft structures (generally 1.5-2) can be far lower than those for other structures like bridges or buildings (which, due to redundancy in structural members can be 3-4 or higher). This is based on the simple reality that if you design to much higher safety factor levels, airplanes would simply be too heavy for practical flight. Thus extreme rigor goes into aircraft structural design and load prediction.

Maxwell Smart

Post-flight images showed at least 1 completely missing and 1 partially missing fan blade.

DenverBrian

If the engine had indeed sheared off, I seriously doubt any of the pax would suddenly sigh with relief and say "ah, that takes care of the vibration."

EWR764

eng3

If I was looking out the window, I would be wondering, did the cover just fall off on its own? or did something go wrong inside the engine causing the cover to come off. The later being much worse. With the vibration, I would assume that something inside the engine went wrong.

I think it is in the procedure to shut down the engine if it fails, especially if it starts vibrating alot specifically to avoid having it threaten the rest of the structure. I believe the pylon is built to be extremely strong so I think it would take alot to shear it off (not that it hasnt happened in the past). I had thought the fail safe design feature was when the plane impacted terrain. Or maybe I'm thinking of the landing gears.

I believe you can still fly the plane if the engine comes off, but the pilot has to know the problem. It is good someone actually came out to visually look. I've seen a couple disasters where the pilot had no idea what was going on behind him (because he was so busy dealing with all the warnings) and made some faulty assumptions. The worst disaster in US history (AA191), an engine actually came off, the pilots didnt know. It took out a slat with it also causing the plane to bank and raising the stall speed of the left wing. Unfortunately that engine also powered the captain's instruments and the stall warning system and CVR. The procedure back then caused their speed to be too low so they stalled and crashed. Had they increased their speed or had the warning systems, they could have recovered