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Qatar Airways grounds 13 Airbus A350s as fuselage degrading

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Re: Qatar Airways grounds 13 Airbus A350s as fuselage degrading

#51

Post by systemvoltage »

EMM_386 wrote: post #5

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.

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?

Re: Qatar Airways grounds 13 Airbus A350s as fuselage degrading

#52

Post by bobthepanda »

walrus01 wrote: post #27
EMM_386 wrote: post #8

Earlier quoted context omitted.

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).

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.

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

Re: Qatar Airways grounds 13 Airbus A350s as fuselage degrading

#53

Post by jeffbee »

JKCalhoun wrote: post #6

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 mat…

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.

Re: Qatar Airways grounds 13 Airbus A350s as fuselage degrading

#54

Post by jeffbee »

orra wrote: post #24
IshKebab wrote: post #19

Earlier quoted context omitted.

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.

Re: Qatar Airways grounds 13 Airbus A350s as fuselage degrading

#55

Post by InTheArena »

jacquesm wrote: post #43
InTheArena wrote: post #20

Earlier quoted context omitted.

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.

Re: Qatar Airways grounds 13 Airbus A350s as fuselage degrading

#56

Post by jacquesm »

InTheArena wrote: post #55
jacquesm wrote: post #43

Earlier quoted context omitted.

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.

Re: Qatar Airways grounds 13 Airbus A350s as fuselage degrading

#57

Post by namibj »

himinlomax wrote: post #23
JKCalhoun wrote: post #6

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 mat…

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.

Re: Qatar Airways grounds 13 Airbus A350s as fuselage degrading

#58

Post by samstave »

EMM_386 wrote: post #5

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.

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.

Re: Qatar Airways grounds 13 Airbus A350s as fuselage degrading

#59

Post by EMM_386 »

systemvoltage wrote: post #51
EMM_386 wrote: post #5

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.

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?

> 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.

Re: Qatar Airways grounds 13 Airbus A350s as fuselage degrading

#60

Post by philjohn »

himinlomax wrote: post #23
JKCalhoun wrote: post #6

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 mat…

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.

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).
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