Another flaw found for 787 ?

[JF Mezei]

http://www.reuters.com/article/wtUSInvestingNews/idUSTRE57D1ST20090814

Basically, on June 23rd, Alenia stopped work on 2 sections of the 787 it
was producing. "after structural flaws were found on fuselages".

##
Alenia Aeronautica halted production because of wrinkles in the fuselage
skin caused by flaws in subcomponents of the one-piece composite barrel,
said Boeing spokeswoman Loretta Gunter.
##

##
Flaws were found on 23 airplanes, starting with the seventh in
production, Gunter said. She said a solution has been designed and
patches will be applied to all the planes built so far.
##


##
"As we implement this change, we are not going to produce any new
barrels until there is an engineering change that will keep the
subsequent units from needing to be modified," she said.
##


QUESTIONS:

Is this a totally new flaw in the 787, or is it related to the
wing/wingbox attachement ?


I am surprised that Boeing wouldn't have supplied an ECO already,
allowing Alenis to produce 23 sets of fuselage sections. It isn't as if
those would have been produced overnight, all containing the same flaw.


Could this just be some PR strategy where suppliers are stopping
production because they just can't afford to continue producing parts
that Boeing won't need for years to come ?

Until the 787 has had sufficient flight testing, having so many aircraft
parts alrteady produced would be risky if changes are needed. I don't
think it was smart for Boeing to allow suppliers to continue to produce
parts for so long now.
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[Uwe Klein]

Post by JF Mezei
Is this a totally new flaw in the 787, or is it related to the
wing/wingbox attachement ?

Seems to be unconnected.

The way I have understood this, it is an issue with the stringers
embedded in the mandrel for barrel sections resulting in (small) folds
in the wound tape skin of the barrel. ( a photo would help, for sure)
( Hmm: do they produce the 3/4th barrel over the wingbox
as a barrel and cut/ditch the lower segment? whatever.. )

Either layed out fiber tape is displaced sideways or "excess" skin is
folded on itself during resin bakeout under pressure.

It is not clear to me if this is connected to changes in the stringer
raw material or with the (new) CAM manufacturing cell from AGFM
http://www.agfm.com
http://www.agfm.com/Initiatives/ManuFCells.pdf
( or both ).

thinking a bit about working with an inner mandrel:
you have to wind fiber tape under some tension onto the barrel
and the mandrel can not have elastic/plastic inserts otherwise
the fiber layup is transitioned from tension to compression while
the resin is at its most fluid phase.

uwe
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