Qatar Airways grounds 13 Airbus A350s as fuselage degrading | Hacker News Reader

Qatar Airways grounds 13 Airbus A350s as fuselage degrading

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129 pointsjryle7066 comments

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.

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.

Is there a link or some other substantiation to the rumor? I'm quite interested in this (but for an entirely unrelated field).

It's being talked about on the airline forums (PPRUNE and airliners.net), but no definitive source from what I can see yet.

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.

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.

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?

Are they losing money grounding them? They're probably operating fewer flights that pre covid so they could have more planes then needed and be using this opportunity to 'ground' planes with minor issues as a negotiation tactic to extract concessions from Airbus.

> 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.

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.

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).

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.

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.

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.

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.

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...

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

I live in Qatar, and the Qataris are notorious for finding ways to avoid paying their bills, delaying payment for extremely long periods, or asking for unreasonable reductions. Claiming something is wrong or faulty is a common tactic, another one is to substantially expand the scope of a project, and then refuse to pay when the project inevitably runs over the original deadline.

Akbar Al Baker pulled similar cons with the construction of Doha airport, demanding the project be accelerated but refusing to pay for the extra work that would be involved. Bechtel and Lindner/ Depa Interiors are two companies that spring to mind. They also suffered due to the erratic and insanely inefficient bureaucracy that is endemic in Qatar - 60-70% of Qataris "Work" in government jobs.

Similar stories can be heard of tower construction in Qatar. Empty and unfinished towers littler the country due the Qataris failing to pay their dues to construction companies. This article superficially covers it: https://www.constructionweekonline.com/business/article-3775...

Will be interesting to see if the pill the world cup off next year with this style of bullshit.

You don't know the half of it. When they held the Asian cup, they were so concerned with the stadiums looking empty, they forced laborers to go and fill the seats. Problem is that many legitimate ticket holders were then denied entry! Of course people got angry about that, so the police saw fit to start administering beatings to people.

Now image that scenario with drunken football hooligans instead!

The pill -> they pull. Hard enough with alcohol in the shithole never mind pills ;)

> Qatar

Could it be the Qatar weather, typically over 40°C (100°F)?

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).

Even if so, for such an expensive product, the customer would expect it to withstand local weather conditions.

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.

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).

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.

Yes, and quite possibly they did not factor in the long term differences between interaction of paint and materials.

Sounds plausible, if someone told me that this can of paint designed for that epoxy destroys this thermoplastic, I’d just believe it.

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.

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?

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).

You want your plane to be mostly white in color to reflect solar heat and reduce the load on the air conditioning packs.

White paint also weighs slightly less which, across a fleet, adds up to an economically relevant fuel cost.

Why would you think that? You think these aerospace engineers are a bunch of goof offs?

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.

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.

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.

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.

road cycling is probably less harsh than a plane cycling through 0 to 30k+ feet multiple times a day, though.

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.

If it's cosmetic only, why the grounding?

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.

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.

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).

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.

Does the impact resistance degrade during the expected lifetime of those composites?

No, except inasmuch as the resin may degrade over time, but that's not just an issue for impact resistance.

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.

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.

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.

> [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.

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.

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).

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

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?

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.

This could well be interaction between the paint or primer used and the resin/polymer used to make the carbon fiber hull parts.

"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/

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.

This has no bearing on this article, it is not about fatigue but about surface defects, not structural defects.

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.

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.

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.

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

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.

See comment above from InTheArena.

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