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.

Post #898

Composite repair techniques are well known in the plastic aircraft sector, there is no need for new things to be "invented" just stress calculations to be done and drawings made so that the work is done to the correct specification.

Post #900

No need for a temporary repair, the structural repair can be done in situ, or at least at LHR, once most of the preparation has been done inside a temporary structure the final lay up will require the aircraft to be in a hangar to prevent the wind moving the aircraft structure around while the resin is curing, as soon as the resin is cured then the aircraft can return to the temporary structure for the rest of the work.

As I have said before on this thread a composite aircraft requires a composite repair........... The last thing in needs is a metal centric patch and rivet job. That just increases the weight and decreases the aerodynamic efficiency.

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.

@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.

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.

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 !

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.”

@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.

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 !

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.......

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.

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.

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?

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 :sad:.
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.

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

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

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.
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?

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.

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.

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.

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

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

If they patch it up and fly it somewhere for a proper repair, will they take off over central London, or M25/ Windsor Castle?

They can always close the M25 and make sure the Queens not at home, and then insist on a westerly departure

just to be safe

Full wings
 

Have you ever done a composite repair on an aircraft primary structure ? I won't dispute the economic part of your post but on the technical issues you fall well short of the mark.

Assuming you're speaking of the JAL 747, the repair was designed correctly - the problem was it wasn't implemented properly.

Or they are speaking of the China Airlines again a case of AMM not being followed

I've owned/operated composite aircraft for the last 30+ years and observed the manufacturing, repairing (and breaking!) of them over that period. What don't you agree with in what I said?

Would it not fit in a Beluga (or Antanov.) ?

That's not going to happen.

Full wings
 

I don't think that Boeing are using an autoclave as you say, I think that the big oven is just that....... A big oven, it does not use the very high pressures that are required for autoclaving. Having looked at it on u tube the structure of the oven appers by the nature of the structure to be incapable of very high pressures.

Boeing have been in the aircraft business long enough to know that aircraft will get damaged in service and simply would not manufacture an aircraft not able to withstand the rough and tumble of airline service. So it follows that they have already given field repair of the structure a very good thinking about. So if you can't put the whole aircraft in a big pressure cooker then you will have to use a resin system that cures at room temperature and then post cure it at a temperature IRO 80c. Some pressure can be applied with vacuum bags and there are a number of ways to get the heat applied in a controlled way.

A well executed scarf repair can achive a strength as near to 100% of the new item as makes no practical diference with a very small increase in weight.

There is no doubt that the size of this repair makes in more challenging than most but it is technically possible just so long as it is left to the composite experts and those with a metal aircraft background don't try to influence the process with metal repair techniques.

The economics and politics are another matter that may well scupper the repair but from a technical point of view a field repair is possible

A and C

Possible, good sir.
Posing is something charlatans enjoy.

Exactly, wasn't the repair done by Boeing technicians?

I thought (reading elsewhere) they were going to build a temporary building structure and bring in a complete new tail section to replace the existing one?

Spot the problem with that suggestion:

http://www.boeingblogs.com/randy/ima...213-2final.jpg

@DaveReidUK:

It seems they can do it with a 747 vertical stab, which is much larger and more unwieldy:

Yes, you can get away with pretty well anything with an aircraft that isn't intended to fly again. :O

Removing the vertical stab is a pretty routine procedure for allowing airplanes to into hangers that otherwise would have inadequate clearance - and those airplanes nearly always fly again (the one exception I can think of was when the hanger burned - along with the airplane).

I'd think the bigger challenge would be moving and aligning that big tail barrel section without the dedicated tooling (as I noted earlier).

Well I've never encountered that, but I'll take your word for it.

I'd say that's a understatement.

I may be wrong, but I don't think we'll be seeing any tents and cranes at Heathrow any time soon.

First ever post on here, not sure why I can't quote TDracer. Removing a Vert Stab to fit it into a hangar, I have never heard of removing a stab of any sort just to get it into a hangar and as for being a routine procedure, do you remove the stab out doors and then bring it in.

Just for clarification, I am not talking about puddle jumpers.

Yes but on this plane they removed wings and tail to put it on a barch from Schiphol to the Lelystad museum. It was not ment to fly again....

In Everett probably anything is routine but I understand you need a special bay and tooling to pull a trick like that.
Never heard of a stab routinely removed, except in case of damage but certainly not to save some hangar space..