New Boeing 787 troubles 1

[thebard3]

Now there is a new problem with some 787s. No detail about what the issue is, other than to say it's a manufacturing defect related to fuselage section connections.

https://www.avweb.com/aviation-news/boeing-tells-airlines-to-ground-eight-dreamliners/

Brad Waybright

The more you know, the more you know you don't know.

 

[verymadmac]

Doesn't appear to be an emergency AD out for it yet! or any other form of AD that I can see.

 

[1503-44]

Kind of expected at this point, corporate cultures being highly adaptive and all.

 

[waross]

I understand that Boeing has identified the affected aircraft and contacted the owners directly without waiting for the FAA to act.
Keeping the FAA informed does not seem to be part of the Boeing culture.
Boeing may have thought that by issuing the grounding pre-emptively, they may limit the grounding to 8 aircraft while the FAA may take a wider view.


Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[IRstuff]

The article states that they identified 8 planes and notified the FAA.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

https://www.youtube.com/watch?v=BKorP55Aqvg

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[verymadmac]

The point being that requests from Boeing not to fly have no legal grounds (wise or otherwise). It warrants an emergency AD or it doesn't. That one isn't out yet, means the FAA is broken or the Boeing press release is largely BS (noting they apparently want to close the unionised 787 fuse production line).

It should also be pointed out that much of the cost savings the 787 was present as offering came from cheaper assembly labour.

 

[thebard3]

No idea yet what the problem is yet. Blaming it on cheap labor seems a little bit (very) premature at this point. It sounds to me like some part of QC was incomplete so there may be no problem with the airframes at all. I'll wait until more information comes out to make a judgement.

Brad Waybright

The more you know, the more you know you don't know.

 

[Alistair_Heaton]

It's "something" to do with mating the tail onto the main body which occurs just behind the pressure bulkhead at the back. Which is an area which is notorious for having issues even on metal planes. The APU sits in the tail and generates all sorts of vibrations and loads. And most of the moments of the stab are dealt with in this area. It where the trim stab screw jack is.

The mating surfaces have to be spot on otherwise you create localised point loads which then screw up your stress transfer calcs. So they developed this robot machine which measured any gaps and then produced a shims to fill the gaps.

From what I have read the shims on these aircraft are not up to QA standards and they are worried that they are going to get individual failures around the attachments which will then lead to a reduction in limitload. There is also something about finish surface roughness which makes matters worse.

Airbus splits the hull in a different place. Just forward of the main spar so doesn't have a join at the back, but it did have an accident with a composite tail falling off due to pilot training.

I also find it very strange that the FAA hasn't issued an emergency AD grounding these airframes. It also smells a bit to me that politics are involved with the cuts to production capacity which will occur in the next 3 months. My gut feel is there will be some funny things happen and statements made until November. And depending on who gets in, will depend where things go next.

 

[davefitz]

Yikes. I wonder if the boeing engineers that are familiar with all of the issues need to take tranquilizers prior to boarding a plane.

"...when logic, and proportion, have fallen, sloppy dead..." Grace Slick

 

[1503-44]

Yeah, in fact why would they stop taking them when boarding.

 

[Alistair_Heaton]

I personally have a lot of sympathy for the Engineering and production employee's. I suspect that they have not willingly produced the quality of item that they want to or could produce. But have been forced into a series of compromises which we are now seeing the results of.

 

[rb1957]

"We the willing, led by the unknowing, are doing the impossible for the ungrateful."

another day in paradise, or is paradise one day closer ?

 

[Lou Scannon]

"the unknowing", AKA products from the "head up the ass school of management"

"Schiefgehen wird, was schiefgehen kann" - das Murphygesetz

 

[SWComposites]

Or, “Engineering is doing the impossible for the ungrateful in an unreasonable amount of time.”

 

[Alistair_Heaton]

Thankyou for rewording my thoughts in a much better way.

 

[Alistair_Heaton]

What I wonder is why put the break there anyway. Before and aft of the wing box would have been my first thoughts.

Also a vertical interface between two sections of huge complex moment transfer load? plus you have the transition between pressurised and un pressurised.

I would have been thinking tenon joint mating faces so there would be some solid material along the centre line limiting the ability for it to rotate and giving more surface to attach it in different axis of primary load.

But then again I am utterly clueless about composites. Although did look in awe of the autoclave and wing making gear in Harrowden when I got a look round the factory.

 

[Alistair_Heaton]

I posted this in the 737 max thread but then this thread started. It gives a quite good picture of the section they have issues with and the mating surface.

Which will give those of you that know what your talking about more scope to comment. Because I will freely admit I don't know what I am talking about in regards to composites and this subject.

https://theaircurrent.com/aviation-...ight-787s-from-service-over-structural-issue/

 

[SWComposites]

a) there are all sorts of errors in that article
b) that section 47 to 48 joint is the essentially the same on all commercial transports, aluminum or composite
c) they apparently didn't shim the joint properly, which usually means there are excessive gaps between the joint members
d) its kind of odd they are calling it a limit load problem; usually these things are critical at ultimate load
e) its very likely the full story has not been disclosed, so what is in the press so far is probably half rubbish at best

 

[Alistair_Heaton]

I wouldn't say its essentially the same, most types I have seen in production have the join in front of the rear door inside the pressure vessel. But they have all been European designs. And I was taught and later on was told by mentors to not put complex load areas over joins if you could help it.


Looking at the pics on the web all the airbus types the join is forward inside the pressure vessel. They may have another section on the tail after the rudder and elevator attachment points but they look more like aerodynamic fairings not load bearing structures.

A220 its rearwards of the door and includes the rear hold but it doesn't have a composite fuselage and the pressure bulkhead is rearwards of it inside the main body. And metal to metal join its much much easier to control load transfer especially rotations. .

This article seems to cover the differences in philosophy between the two ways of thinking.

https://www.intechopen.com/books/ae...omposite-fuselage-a-manufacturing-perspective

But I can understand why they want to end the barrel where they do. It allows them later to stretch the fuselage and not touch the tail section.

I also suspect AA587 investigation gave Airbus plenty of understanding about what the loads are in that area.

 

[Alistair_Heaton]

Just some more articles that might be of interest.

https://aviationweek.com/air-transp...787-problems-spotlight-boeings-quality-issues

And an article reprinted from the WSJ

https://www.dailymail.co.uk/news/ar...t-broad-FAA-review-Dreamliner-lapses-WSJ.html