Ethiopean 787 fire at Heathrow

[Ian W]

Originally Posted by poorjohn

Huh? I haven't paid much attention to this thread - small battery fire, no big deal - so it comes as a surprise that the hull might need strengthening for a ferry flight back to the factory. Can't be true, given the assurances that the composite structure survives fire better than aluminum, etc.

It probably doesn't need strengthening from an engineering viewpoint. From a safety regulator point of view though this is a CYA. As every aircraft incident now is checked to see if its a 787 and if so the peanut gallery gets overexcited. It will be more than the safety regulator's jobsworth to take a simple engineering decision.

[DozyWannabe]

@poorjohn - This wasn't a "small" battery fire as with the incidents to the Japanese B787s, this was something considerably larger and more serious which has potentially damaged structural components.

[joy ride]

It has been very nearly 3 months since the fire, so a lot of lost revenue and storage fees to top the final bill.

I would be interested to know how long it would take to repair a metal plane with similar damage levels as a comparison, but I understand that there are also concerns about toxicity during and after a composite fire like this one, so any necessary deep "clean-up" could also add to the bill.

I do have real concerns about the 787 and other composite airliners, and over other problems which have affected the 787. I also have great concerns about modern management attitudes and practices and how they seem to be compromising quality and reliability in a wide range of different industries as well as avaition.

The 787 does seem to have stumbled into several different areas of concern and I follow the unfolding saga with great interest and a certain amount of doubt. However, that does not make me a 787 hater.

[A and C]

Joy ride

The toxicity issues of the composite structure is much overblown, just like metal aircraft the vast majority of the toxic substances will come from the internal trim, fixtures and fittings.

There is more in the way of toxic substances but in percentage terms of the total clear up I would guess at IRO 10% more than a metal aircraft.......... Hardly a big issue !

[olasek]

Among findings in testing using FAA-approved methodologies were:
• The composite materials used for the 787 do not propagate an in-flight fire.
• The fuselage skin is an excellent fire barrier, and resists flame penetration far longer than an aluminum fuselage
• The toxic gas levels produced in a post-crash fire scenario are similar for both a composite fuselage and an aluminum fuselage

“The standards that the FAA has established for the 787 are intended to provide sufficient time for occupants to safely evacuate the airplane following an emergency situation. FAA research shows that the composite fuselage material significantly increases the time it takes for a post crash fire to burn through to the interior, which increases the time for occupants to evacuate before the exterior fire can endanger them.”

[HeavyMetallist]

@olasek:

That's all very reassuring, if it's a post-crash fire outside the aircraft. However if the fire starts inside the aircraft, as in this case, then that comforting composite fire penetration resistance becomes irrelevant, and the toxicity effects higher for anyone inside than with an equivalent aluminium structure.

[A and C]

Heavy Metalist

Such is the toxic nature of the interior of any aircraft if you have a serious fire you will have a large quantiy of toxic gas that is most likely to kill you.

A small amount of extra toxic gas from the composite primary structure is only likely to kill you for the second time !

[bvcu]

mmm, post crash fire ..... so all that safety stuff after a harrier crash with the composites was tosh then ! Boeing ought to be aware of it now that they own and support the current version of said aeroplane.......

[A and C]

bvcu

It's not just Boeing that you should aim your wrath at after all most Airbus aircraft only use metal for the fuselage tube and main plane box.......the rest is composite.

[SLF3]

Wasn't the Egyptair 777 that had a 'small' electrical fire in the cocpit a write off? I suspect the problem is that the structural repair is the easy bit (be the plane metal or plastic) - it is fixing (and being confident you have fixed) all the heat and smoke damaged stuff that is the real issue.

[YRP]

There is a lot of talk about this being new territory, repairing FRP on this scale with this sort of damage (heat vs mechanical).

I am curious: would this be a straightforward repair of a metal structure? It seems like there was a significant enough fire that even metal would be "challenged", eg perhaps enough to melt or soften metal. From what I recall of photos from some time back, the damage was a good fraction of the way around the curve of the hull, i.e. not just one spot or two but affecting several longitudinal structural members.

I'm out of my depth with structures, but wouldn't this be an unusual type of repair for any construction?

[tdracer]

I've yet to see any pictures of the interior so it's hard to know how widespread the damage is. However as I noted before, depending on the amount of fuselage damage, the most cost effective fix may well be to simply replace the tail barrel section with a new one. Problem is, it may not be practical to replace that section on-site (Boeing has some highly specialized ground handling equipment and tooling to transport and assemble those big barrel pieces in Everett and Charleston).

I wonder if they might do some sort of temporary repair just to make it airworthy, then fly it to Charleston or Everett for proper repairs.

I saw a TV show the other night that talked about the Qantas A380 rotor burst that said it took 18 months and $150 million to fix it .
The other cost aspect is - if they scrap it, how long will it take to replace it. There have been cases where the damaged aircraft cost more to repair than it was worth, but the multi-year wait to get a replacement aircraft meant it made financial sense to fix it anyway. 787 delivery slots are booked pretty solid for the next five years or so - getting a replacement if this one turned into a write-off would not be trivial.

BTW that Egyptair 777 that they wrote off after the flight deck fire isn't a good comparison - it already had nearly 50,000 hours on it so it's value was much lower than if it had been a nearly new 777.

[Una Due Tfc]

I spent about 6 months in the composite repair shop in the MRO I used to work in. Used to make carbon fibre repairs quite often (mostly airbus floorboards as I recall). When working on the stuff we wore filtered face masks and worked in a well filtered room with large suction machines to catch any stray dust and were always warned the fumes when cooking the panels were extremely carcinogenic. If I saw a carbon fibre fire I would keep quite a distance

[beamender99]

I saw a TV show the other night that talked about the Qantas A380 rotor burst that said it took 18 months and $150 million to fix it

Airbus item
Qantas A380 to resume operational service*| Airbus News & Events

[Machinbird]

Just thinking out loud here. I have no hands on experience with CFRP construction or structural repair.

CFRP consist of two key components, the carbon fiber and the epoxy matrix that ties it together. The carbon fiber seems unlikely to have been significantly damaged by the level of apparent heat that was developed in this fire. Primarily, it is the epoxy matrix that has been degraded by thermal effects.

Although epoxies are essentially insoluble, it might be possible to remove thermally degraded matrix without significantly disturbing the carbon fibers.

A laser method of CFRP surface preparation is discussed here.
There may be variations of the water jet technique that will work assuming the proper working fluid.

If the end points of the carbon fibers are still anchored by adjacent structure that has not been thermally degraded, then vacuum assisted resin transfer could then be used to restore the damaged area to nearly new condition. Additional Carbon fiber cloth could be overlaid as needed to restore full strength.

I suspect the professionals in the subject repair will say, 'Why go to all that bother when a stepped ply repair will more easily and reliably restore the same strength.' In any case, although the structural repair may be a bit tedious, it seems to be eminently practicable.

The driver as to whether the aircraft is written off will be the cost to return the interior of the aircraft to serviceability, not the difficulty of structural repair.

Has anyone here actually seen the condition of the interior?

[Bigpants]

Write off logic

Economically it is a write off (in my opinion) because of the time scales involved and the cost of hangarage at LHR but politically Boeing will view it as a repair and fly at all costs.

[A and C]

Machinbird

The stepped repair will not do any good as it is not as strong as scarfing.

The structure needs to be cut back to the undamaged structure and a new section scarfed into place, this type of repair is as strong as the original structure and skillfully done will increase the weight by about 1% in the repaired area. This type of repair also leaves the aerodynamic profile exactly as original.

[FullWings]

Given that it costs around $1.1M in leasing, $150K in parking charges and several $M in lost revenue every month, one would have thought that if it were that straightforward work would have commenced by now. Must be $10M+ and counting, not including the repair.

The fuselage is made of a continuous spiral of automatically tensioned pre-preg carbon, cured in a hangar-sized autoclave. Recreating the original mechanical properties by scarfing and hand layup in the damaged areas is a pretty challenging prospect, unless you go significantly thicker/bulkier/heavier. Then you have the problem of the internal and/or external dimensions not matching the blueprint, so stuff might need re-routing or re-designing.

If I was a betting man, my money would still be on a "bodge" then fly it back somewhere warm and dry where they can chop the burnt section out and attach a new one, which they know how to do as it's part of the manufacturing process. The risk of a repair that goes into service and then fails is far too high, IMHO.

[DaveReidUK]

then fly it back somewhere warm and dry where they can chop the burnt section out and attach a new one

Or, if all else fails, remove the manufacturer's identification plate and attach a new airframe to it ...

[denachtenmai]

which they know how to do as it's part of the manufacturing process.

I think that one far eastern airline would challenge that, and that a/c was not made of exotics