To achieve certification the engine must pass a 'blade off' test. The engine casing immediately surrounding the fan must be capable of containing the rogue blade. Kevlar is used on some. In the pictures above of this incident, the fan case is intact (or at least looks so). The fan inlet cowl however is severly damaged and largely missing. It is not designed to withstand a thrown fan blade.
You tube has a few videos of engine blade off tests. :ok:

The engine must demonstrate that it can withstand the intentional loss of a single blade and its consequences (e.g multiple blades in a domino affect, imbalance and/or seizure forces and fire and explosions).

The engine is normally defined by its front and rear flanges and as-shipped accessories.

Under the oversight of, continued airworthiness, corrective action against a demonstrated threat to safety need be addressed (could be at the engine level or the aircraft level)

I have doubts that blade parts took out that window

At this point, I have not seen enough of what's going on at the bottom of the engine that might have affected the cowl latches.

Pax video onboard
 

You know - you really should lighten up - one passenger is dead and others were injured. Quite a few of those folks likely thought this was their last day. People do what you might consider "strange" things when faced with certain death . . . write notes, leave mementos, whatever.

For most of the passengers on that flight - there was an explosion outside - and it appears as though bits of the outside came inside - injuring several passengers. I'm sure there were some horrid sounds associated with the event, coupled with the masks dropping, the aircraft "dropping" and a passenger being sucked out of the plane (or whatever actually happened). It is the stuff of movies.

Certainly better of you to think you'd be a smooth operator in any given emergency - and not fumbling for a clean set of drawers.

There's really nothing funny about what happened - and, sorry, but I don't fault the passengers for putting that ridiculously-sized mask on incorrectly. Folks panicked . . . give them a bit of a break.

This is the best image I've found of the engine. I've given it some mild enhancement. The damage pattern is... interesting. The fan looks substantially intact, or at least not completely disrupted - but the engine forward of the fan looks completely munted. It looks almost as if (note, as if, not saying that actually happened!) it hit something fairly substantial, but didn't ingest it.

Any thoughts on what could cause that damage? The other thing it looks kinda like is the 'explosive' damage you might expect from something like a compressor surge on steroids - you know the really loud BANG type with flames out the front of the engine; like that but something worse.

Interestingly, Southwest 438 back in 2007 was determined to be "...due to the No. 2 engine experiencing a release of its fan spinner through the fan cowl as a result of an unidentified object striking the spinner, separating it from the fan disk and causing the spinner to be ingested into the fan blades."

Damage in that incident: severe to fan, much less to cowling:

http://avherald.com/img/southwest_733_dal_3_640.jpg

EDIT for clarification: above is engine from Southwest 438 in 2007; below is today's failure:

Looking at the available pictures I would agree. I would suggest it is more likely that the outboard fan cowl flipped up and exited over the top of the wing and caught the window at 15A on its way past. Not nice for the pax sitting in that seat judging by the amount of blood on the outside of the fuselage.

Lots of miss-information on this thread, and Stumpy you're not helping. I also hate repeating myself, but here goes:
1) Released/broken blades are not considered 'infinite energy' - engines are certified to contain blade failures - fan blades by the fan case containment ring (used to always be steel - many newer engines use Kevlar). Compressor and turbine blades are contained by the engine case (nearly always steel). Fan blades can and do initially move forward when released - remember they are basically pulling the aircraft forward so there is a significant forward force vector on the blade. The fan case containment ring extends well ahead of the fan to account for that but it's certainly not uncommon for fan debris to damage the inlet forward of the fan case.
2) Burst engine discs are considered 'infinite energy' and are allowed to be uncontained since sufficient shielding would be impractical (they are also not supposed to ever happen). The Iowa City DC-10 was a burst fan disc, the Qantas A380 was a burst turbine disc.
This event does not appear to be a burst disc.
3)The fan inlet cowl is not intended to contain engine parts - the fan case does that. It's purpose is purely aerodynamic (to provide 'clean' airflow to the fan face and a smooth aerodynamic surface around the engine) along with acoustic treatment to suppress fan noise. However it's not supposed to fail due to the forces of a fan blade out - and they are designed to contend with the forces associated with a fan blade out event. I'm sure the NTSB, FAA, and Boeing are all concerned that there have been recent fan blade out events where the inlet departed the aircraft.
4) The preliminary report on the 2016 Southwest fan blade out event attributed the release to metal fatigue, and the fan blade inspection requirements were supposed to updated to address that failure.

fan detail image
 

New images on twitter: https://twitter.com/NTSB_Newsroom

Looks awfully like a missing fan blade in the elbow/forearm area...

https://pbs.twimg.com/media/DbBjwpkWAAAGTux.jpg

I used to like being seated over the wing, seemed a quieter and safer spot, wondering about the pax sucked into the blown out window, did she have her seatbelt on, would a belt hold you from a similar fate.

Tragic though the loss of one passenger is (RIP), it does demonstrate just how spectacularly safe flying by jet transport (in the USA at least) has become.

Since 2009 you would be more likely to win the lottery twice than to perish in a jet transport incident.

Hold that thought.

I always figured that sitting over the wing box structure was a good place for the more survivable crash scenarios. Nobody plans for a freak window removal, and this does seem like just very bad luck in where the debris hit.

Too early to tell if the blown window caused the major trauma or anything after that, so a seatbelt might not have made a difference. They'll be talking about this one for years.

tdracer
There's nothing special about the behaviour of a CF56 fan blade, yet given that there is a fan blade release the B737 inlet cowls have more damage than most other cowls on Boeing aircraft.

It shouldn't be difficult to address

Hopefully this isn't 'fake news' - story about the Southwest pilot during the event:

https://heavy.com/news/2018/04/tammi...0-engine-hero/

Not quite Sully territory, but a job well done none the less.

Anyone else find reports that the cabin staff were trying to plug the hole odd? There would be bugger all items in the cabin with anywhere near the structural strength to do that - and items being fed through the hole could have snagged.

That seems strange...

In an interview on CBC Radio, the passenger Martinez said that the unfortunate lady in the seat next to the window did have her seatbelt on. He said that a male passenger forward of her seat came back and was the main individual engaged in restraining her from being sucked out.

Not just the CFM56/737 - an event a couple months back on a PW4000 777.

https://www.pprune.org/rumours-news/...ghlight=PW4000

BTW that photo posted by infrequentflyer shows surprising little damage to the surrounding blades. Interesting...

Not if it started out small. If it were an entry hole from a small fast object they may have tried to plug it to slow loss of cabin pressure (it is a thing for a slow deconpression) but may not have realised it's not going to do much with structural damage.

The procedure is usually used when you have a faulty door seal and getting noise from it not for plugging a hole. Confusion perhaps?

The 7 minute CBC Radio interview with Marty Martinez can be heard via the following URL. 'This plane is going down': Passenger describes moments leading up to emergency landing | CBC Radio

Indeed great job from the cockpit both during and after the event.

However we are back to seeing the word 'hero' thrown about again. It was as much in Tammy's own interest as it was the rest of the passengers to get the airframe down in one piece. Heroism should be left to describe those who deliberately and selflessly risk their own lives to save the lives of others.

In this scenario, if the hole had been much larger and an entire seat with passenger was about to be sucked out, yet another passenger seated in a 'safe' part of the fuselage undid their seatbelt to hold the person from falling out - that would be heroic. They would be endangering their own life to save others.

Pedant mode off.

Agreed!

Yet to be verified, but here's the report in NYT:
https://www.nytimes.com/2018/04/17/u...pgtype=article

Maybe all of that was unnecessary, but it sounds like not just flight crew but pax were trying to help out. If true, that deserves some credit.