[HN Gopher] Qatar Airways grounds 13 Airbus A350s as fuselage de...
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Qatar Airways grounds 13 Airbus A350s as fuselage degrading
Author : jryle70
Score : 118 points
Date : 2021-08-07 14:36 UTC (8 hours ago)
(HTM) web link (www.msn.com)
(TXT) w3m dump (www.msn.com)
| jacquesm wrote:
| This could well be interaction between the paint or primer used
| and the resin/polymer used to make the carbon fiber hull parts.
| naturalauction wrote:
| Given that the Qatari regulator ordered the grounding and that
| Qatar Airways is state owned that seems like a pretty big
| conflict of interest. Especially with Qatar Airways refusing
| delivery of any more a350s until the problem is fixed (in a time
| of extremely low levels of international air travel).
| [deleted]
| baybal2 wrote:
| Well, a good time to say Bravo to their regulator then.
|
| Imagine if the regulator, and the state airline was ran by
| people half of whom shared the same surname, and it happened,
| say, in USA.
| dathinab wrote:
| Except that imagine the issue is non-safety related and the
| regulator which happens to be related to the Airline company
| grounded them on requests of the Airline during low traffic
| times to put more pressure on the manufacturer and maybe
| profit from higher damage payments.... (Purely speculative to
| give a point for the next argument.)
|
| I.e. we can't say if the regulator acted correct with safety
| concern or corrupt until we know what is actually going one.
| Just because something seems to be "proper safety orientated
| acting" on the first sight doesn't mean it is and neither
| mean it's not corrupt...
| bdjddd77 wrote:
| I'd say this is correct. Qataris have one rule for them and
| another for everyone visiting or working ( the flippas,
| Nepalese etc), a friend is quite well connected as part of
| chemical supplies to oil industry, more like store at
| origin and broker nowadays, they live by different laws
| than the mere mortal (like me) passing through. You can
| live it large if you have the right connections -
| connection to above - one form of corruption doesn't exists
| it's systematic so yeah making the regulator act to protect
| a private contract condition is very plausible in qatar
| akiselev wrote:
| Qatar has a population of over 2.5 million but only about
| 300,000 of those are native Qataris. Even if they have
| different last names, chances are they're somehow related.
| bdjddd77 wrote:
| This is true, briefly thought I was in manila when doing a
| hotel stop over, only the hotel manager seems to be a
| native. Horrible country, but I'll do the gov subsided
| stopover frequently when travelling back and forth.
| InTheArena wrote:
| Qatar is bringing A330s out of storage and up-gauging some
| routes to 77Ws, which have significantly higher fuel-burn (due
| to more seats, and a older airframe). I doubt this is just a
| negotiating position.
| belter wrote:
| "How safe are modern aircraft with carbon fiber composite
| fuselages in a survivable crash?"
| https://www.materialstoday.com/carbon-fiber/features/how-saf...
|
| PDF direct link: https://www.materialstoday.com/download/127653/
|
| In Space, but relevant:
|
| "Thermomechanical Fatigue of Unidirectional Carbon Fiber/Epoxy
| Composite in Space"
|
| https://www.hindawi.com/journals/je/2020/9702957/
| jacquesm wrote:
| This has no bearing on this article, it is not about fatigue
| but about surface defects, not structural defects.
| belter wrote:
| The mention of cracks was coming from this post:
|
| "A QR A350, A7-ALL MSN 036, a 4 year A350, was being prepped
| for paint removal from the standard QR livery and repaint
| into the Qatari World Cup 2022 livery at SNN when IAC
| engineering discovered that the airframe had premature cracks
| in the composite fuselage..."
|
| https://www.airliners.net/forum/viewtopic.php?f=3&t=1456315&.
| ..
|
| I am aware of Airbus statement that is only surface related.
| It is surprising they took the airplane back to Toulouse. So
| its certainly something more than just a paint issue.
| avs733 wrote:
| It's not surprising, they wanted more ability to look at it
| than was available at the paint shop.
|
| If they were comfortable flying it that should tell you
| something.
|
| This seems like the first time they've encountered the
| phenomenon so they want to do a deeper investigation to
| understand it.
|
| This whole thread is akin to saying that if you have to
| debug your code it must be beyond repair or poorly
| designed.
| jacquesm wrote:
| Interesting. I'm curious what the eventual outcome of this
| will be but it is always very hard to keep track of such
| stories further down the line, especially if the result is
| non-spectacular.
| belter wrote:
| See comment above from InTheArena.
| AceyMan wrote:
| On the assumption these panels are a component of the
| pressure vessel--and it would seem that they are--then they
| very much are structural components. Not in "the wing will
| fall off" kind of way but in "the whole cabin will
| explosively decompress" way.
|
| /Acey
| jacquesm wrote:
| Yes, they are structural components but as far as I
| understand the article they are not structurally damaged,
| though the company is - of course, and as they should -
| taking the proper precautions to ensure that it _really_ is
| just a surface issue without affecting the structural
| integrity of the panels.
|
| I'm quite interested in what the root cause here is,
| whether it is process related or some formulation issue or
| an un-anticipated reaction.
|
| As a -small- point of order it is against HN convention to
| sign your comments.
| InTheArena wrote:
| The 320s have had composite parts forever. So have virtually
| every plane since then, The 787, for all it's other faults,
| hasn't had this issue, and uses a more radical design for it's
| 787, versus the A350 which still uses stringers and panels,
| rather then put more load on the CFRP.
|
| But that said, given that Lufthansa is also apparently pulling
| and repainting it's A350s, there may be some reaction here.
| [deleted]
| danuker wrote:
| > Qatar
|
| Could it be the Qatar weather, typically over 40degC (100degF)?
|
| How much time do planes spend parked there? I would assume more,
| since the pandemic.
|
| Keeping them in the sun would make them even hotter than the air
| temperature (which is measured in the shade).
| EMM_386 wrote:
| This was first reported back in January when a Qatar Airways
| Airbus A350 was in Shannon for a repaint. When the paint was
| stripped they found surface coating irregularities. This is
| apparently cosmetic and not structural.
|
| This was one of the first A350s to be repainted.
|
| Qatar has 53 Airbus A350 aircraft, so why these particular 13 is
| the question now.
| samstave wrote:
| Wasn't Qatar one of the first countries to purchase these? I
| wonder where in the production line these particular 13 came
| off the line?
|
| It would be interesting to know if these are older or newer in
| their inventory.
| jacquesm wrote:
| Are they in a particular sequence or randomly distributed
| across the 53 hull numbers? If the former it might be a process
| change somewhere in the paint or resin/polymer formulation.
| InTheArena wrote:
| The rumor is that some combination of paint, stripper and CFRP
| led to the actual mesh being exposed. If so, that goes
| considerably further then cosmetic.
| jacquesm wrote:
| Is there a link or some other substantiation to the rumor?
| I'm quite interested in this (but for an entirely unrelated
| field).
| InTheArena wrote:
| It's being talked about on the airline forums (PPRUNE and
| airliners.net), but no definitive source from what I can
| see yet.
| jacquesm wrote:
| Ok. This combination is also used in windturbine blades
| of some manufacturers, it may have substantial impact if
| it is something structural involving the base material,
| less so if it is just a rare combination of
| process/chemicals.
| systemvoltage wrote:
| If it is cosmetic, that doesn't explain millions of dollars of
| loss from grounding the aircraft.
|
| Respectfully, this makes zero sense. Is there something more?
| EMM_386 wrote:
| > Respectfully, this makes zero sense. Is there something
| more?
|
| Yes, the rumors that are swirling that this may just be
| something being used as leverage by Qatar against Airbus for
| contract negotiations.
|
| But those are just rumors.
| JKCalhoun wrote:
| I've been a long time carbon-fiber skeptic.
|
| Only an armchair materials enthusiast but carbon fiber
| construction seems to lack the margin for fatigue that aluminum
| has. It seems to me that when carbon fails it fails
| catastrophically, while aluminum allows some "give".
|
| Now it seems carbon fiber doesn't have the longevity either? I am
| aware the aluminum can "work harden" over time and become more
| brittle as well. No material appears to be perfect but carbon has
| always felt to me to not be going in the right direction.
| IshKebab wrote:
| Yeah I worked in NDT for a bit and it's very difficult to test
| carbon fibre for damage or delamination under the surface.
| There are techniques but not as good as for aluminium. And as
| you said they don't have a nice plastic region like metals.
| orra wrote:
| > [carbon fibre] don't have a nice plastic region like
| metals.
|
| An amusing turn of phrase, given we are presumably talking
| about carbon fibre reinforced plastics.
| jeffbee wrote:
| Metals don't have a "nice plastic region " either. If the
| parts of your aircraft have been permanently elongated by
| plastic deformation, you've destroyed it.
| EMM_386 wrote:
| Keep in mind we have 30-year old A320s flying around using
| carbon-fiber, so we would seem to be out of the trial-period
| phase.
|
| This issue appears to be a cosmetic one with regards to the
| paint layers, not structural (see my other comment).
| walrus01 wrote:
| there are also a number of enthusiastic road cyclists riding
| 20, 25 year old carbon fiber frames - if not crashed or
| mechanically damaged (in a way that would also total beyond
| repair a thin walled aluminum frame like a cannondale CAAD8),
| they last quite a while.
| mihaaly wrote:
| The loads and operating conditions are quite different for
| bicycles and airplanes.
|
| As I wouldn't use the characteristics of my steel
| coffemaker to predict the behaviour of an LNG vessel I
| wouldn't do the same with bicycles and airliners.
| jacquesm wrote:
| I had one of these until very recently, a first generation
| CADEX frame (1987, so now a good 35 years old), still as
| good as new, it went to Germany and is now plying the
| streets of Berlin.
|
| Unless you smash them up just keep them clean and they seem
| to last quite long, at least as long as comparable steel or
| aluminum frames.
|
| The weak points are where aluminum is bonded to the carbon,
| those spots you need to monitor and if there is any damage
| at all you should count the frame as lost.
| rorykoehler wrote:
| When I raced mountain bikes I always found the feel of
| aluminium frames to deaden after a few years. They would
| be super responsive at first and then slowly lose that
| snappiness and with it trail feel as the years went by.
| bobthepanda wrote:
| road cycling is probably less harsh than a plane cycling
| through 0 to 30k+ feet multiple times a day, though.
| numpad0 wrote:
| Apparently A350 are built with Teijin Tenax thermoplastic
| carbon. Brochures say it cures in one minute, eliminating
| autoclave. Could be different from normal resin based
| carbons.
| jacquesm wrote:
| Yes, and quite possibly they did not factor in the long
| term differences between interaction of paint and
| materials.
| avs733 wrote:
| Why would you think that? You think these aerospace
| engineers are a bunch of goof offs?
| jacquesm wrote:
| Because sometimes process optimizations have complex
| downstream effects.
|
| Aerospace engineers are anything but a bunch of goof
| offs, which is why flying is as safe as it is. And that's
| why they pulled the aircraft from service even though it
| is 'just a surface issue' they want to make sure that it
| really is just that before releasing them - freshly
| painted - back into service again.
|
| The history of aerospace quality control is written in
| blood, not because they are goof offs but because
| materials science is complex and sometimes the only
| warning you get that something is wrong is a crash.
| Avoiding those is what this sort of action is all about,
| in any other industry they would have slapped some new
| paint on it and kept going.
| dylan604 wrote:
| Is the paint for anything more than cosmetics/branding
| purposes? Does it provide a benefit like UV shielding
| etc? In otherwords, do we use the paint for anything
| other than ego of corps owning them?
| jacquesm wrote:
| Some paint is more slippery than the substrate it is
| painted on for lower air resistance:
|
| https://www.skybrary.aero/index.php/Surface_Coatings_and_
| Dra...
|
| Then there is corrosion protection, protection from
| ablation (especially on leading edges which usually have
| other protection against this as well), ice adherence and
| so on. So it is far from just cosmetic, and given the
| weight of a single coat of paint (500+ pounds on a 777
| for instance) airlines make sure they optimize for fuel
| consumption because just hauling 500+ pounds along for
| the lifetime of the aircraft costs a pretty penny.
|
| Aircraft are fairly regularly stripped and re-painted too
| (I lived near a special purpose facility in Canada that
| did this, pretty weird to see a widebody come down in a
| location that is not near any major airfield, the first
| time I saw that I thought it was about to crash, but it
| turned out it was there for a paint job).
| chiph wrote:
| You want your plane to be mostly white in color to
| reflect solar heat and reduce the load on the air
| conditioning packs.
| sandworm101 wrote:
| White paint also weighs slightly less which, across a
| fleet, adds up to an economically relevant fuel cost.
| numpad0 wrote:
| Sounds plausible, if someone told me that this can of
| paint designed for that epoxy destroys this
| thermoplastic, I'd just believe it.
| jacquesm wrote:
| That could be, or it could be a process related issue, or
| a change in formulation of a paint that performed well,
| or a change in formulation of the polymer that the fiber
| is embedded in, there are a very large number of options
| to choose from.
| throwawayboise wrote:
| If it's cosmetic only, why the grounding?
| dathinab wrote:
| It's way to early to speculate about this, as we don't really
| have information from either side.
|
| The fact that only Qatar Airways seem to have such problems
| (for now) is also interesting.
|
| The reason could be anything from manufacturing errors with a
| specific batch of them which happened to have been bought by
| Qatar Airways to wrong maintenance by Qatar Airways or the
| planes having been to often exposed to to extreme weather
| conditions as they are not that unusual in Qatar. And even this
| "wide range" speculation is not really usable given the facts
| we (don't) have.
| benhurmarcel wrote:
| A likely reason for why only Qatar airways reports this is
| that they are notorious about regularly publicly complaining
| about "quality issues" in the press during commercial
| negotiations. It's a trick to pressure the aircraft
| manufacturer.
|
| That's not to say that quality issues don't happen, they
| certainly do. But QTR is known to be very quick to refuse to
| work with their supplier and publish the complaint in the
| press, instead of working it out like is the norm, especially
| if it's near a time of contract negotiation.
| yread wrote:
| I am more worried about fire safety. Fire in CF is difficult to
| extinguish. How well and for how long does it protect occupants
| from fire, does it produce poisonous gases and lose structural
| integrity as it heats up?
| Scene_Cast2 wrote:
| If anyone is curious about material science, some keywords are
| "stress strain curve", "plastic vs elastic deformation", and
| "fatigue limit" (that last one is really cool).
| Someone wrote:
| https://en.wikipedia.org/wiki/Stress-strain_curve
|
| https://en.wikipedia.org/wiki/Deformation_(engineering)#Plas.
| .. vs https://en.wikipedia.org/wiki/Deformation_(engineering)
| #Elas...
|
| https://en.wikipedia.org/wiki/Fatigue_limit
| himinlomax wrote:
| Carbon fiber and other composites are actually much better wrt
| fatigue than aluminium. In fact they are pretty much immune to
| it, if you mean the word in the sense it's used in metallurgy.
| They are however much worse for impact resistance.
| philjohn wrote:
| Which is why Aluminium drop-handlebars on bikes freak me out
| - when they fatigue they become brittle and can just snap one
| day if you put too much weight on them (e.g. out of the
| saddle sprinting).
| msandford wrote:
| The only time I've ever had aluminum drop bars go out on me
| was when the salt brine from sweat corroded the aluminum a
| lot.
|
| I was on a hill in a mild rain riding next to a friend. I
| managed not to take her out and stay upright which was
| great. The cycling team I participated on in college said
| road bars need to have the tape off and inspected every
| year. They were right.
| danmaz74 wrote:
| Does the impact resistance degrade during the expected
| lifetime of those composites?
| himinlomax wrote:
| No, except inasmuch as the resin may degrade over time, but
| that's not just an issue for impact resistance.
| namibj wrote:
| To elaborate, carbon-fiber reinforced carbon, the expensive
| ceramic used for very heat-resistant lightweight structural
| members (like the leading edges of the space shuttle, and
| some jigs for use in metallurgy furnaces, where it's lack of
| deformation and low heat capacity is beneficial) can handle
| something around 20% of it's ultimate tensile strength for
| millions of full load cycles.
|
| This is, going by fatigue-limited-strength to weight ratio,
| far better than steel or aluminium. The difference is mostly
| that it's a brittle ceramic and retains most of it's strength
| at temperatures where steel can be poured.
| jeffbee wrote:
| Fatigue is not a concept applicable to carbon fiber reinforced
| materials. Carbon is anisotropic, unlike bulk metals which can
| be modeled as isotropic. Carbon may suddenly delaminate or
| whatever, but it doesn't have a cycling limit.
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