Ethiopean 787 fire at Heathrow

[A and C]

The tent is to keep the workers dry and walm and dirt out of the repair. It is NOT part of the temp critical post cure prosess.

What is so pleasing about the posts above is the total lack of understanding shown by most above about composite repair techniques and the scale of what can be done, on the basis of this I feel that my income over the next few years is very secure.

[DaveReidUK]

Good article here in the Seattle Times about the repair technique:

Boeing readies patch for fire-damaged 787 | Business & Technology | The Seattle Times (http://seattletimes.com/html/businesstechnology/2022097759_787repairxml.html)

Apparently it's scheduled to take 5 weeks, and will be followed by flight tests of the aircraft while fitted with strain gauges before the repair can finally be signed off.

ET expect to have the aircraft back in service in about two months' time.

[Northern Flights]

Let´s hope the gale forcasted for tonight will not be stronger than the VS stand...

...not to mention the tent!

[John Marsh]

DWS:
I'm sure Boeing plans to learn a lot about relatively large scale composite repair in this case.Excellent point.:ok:

A source of valuable new data, which hasn't cost any lives. Not forgetting, the ELT lesson for Honeywell.

[Big Pistons Forever]

Deleted wrong thread

[Volume]

Boeing will cut out the skin damaged by the fire probably in a rectangular cut with rounded edges, he said.
It will cut the patch to the same size and shape and drop it into the space as a plug. The tiny gap around the patch will be filled with paintable sealant that will stretch and compress as the fuselage is pressurized and unpressurized.Hopefully not!
It would be much more reasonable to cut skin damaged by the fire probably in a rectangular cut and scarfen the edges, then to cut out the patch several inches larger than the hole, scarfen the edges and bond it in place with an epoxy resin which will transfer the loads as the fuselage is pressurized and unpressurized...

because otherwise indeed
Boeing’s repair is going to be pushing the limits of what’s been done in the past

[DaveReidUK]

cut skin damaged by the fire probably in a rectangular cut and scarfen the edges, then to cut out the patch several inches larger than the hole, scarfen the edges and bond it in place with an epoxy resinPardon my (already demonstrated) ignorance of composite repair techniques, but what does to "scarfen the edges" mean ?

[joy ride]

A scarf joint is often used in wood work, e.g. for hat boxes and drums. Each end is "scarfed" with a diagonal /overlapping face, so when bent into a circle there is consistent thickness and strength, but a long diagonal overlap so that there is a large surface area for glue to hold to.

Volume's idea seems totally sound to me, but whether it is normal or needed with composites is beyond my knowledge. If the taper of the scarf joints
were in the orientation in which the panel would "plug" into a "socket" on the inside of the fuselage it would thus be almost impossible for it to blow out even in the event of serious adhesive failure.

On a lighter note, the breeze is steadily increasing as predicted, so I am hoping the Queen of Sheba's tail does not blow off with the wind.
(Apologies to Peter Cook and Dudley Moore).

[E_S_P]

what does to "scarfen the edges" mean ?

It’s when you in essence chamfer the mating faces of a butt joint to increase the surface (bonding) area to achieve a higher strength repair. :ok:

[Scuffers]

how thick is the 'panel' here?

I assume we are talking <2mm? so not much point in "scarfen the edges"?

[Volume]

Actually it is not primarily to increase the bonding area (compared to a simple overlap), but to adopt the parts thickness to the loading, so that the deformation remains constant over the length of the bonding joint, hence the shear stress in the bond is almost constant. In a simple lap joint you would have enormous stress peaks at the ends of the bond joint, and the center would not carry any loads.
You smoothly transfer loads from one item to the other and you proportionally transition the wallthickness from full at the begining to zero at the end of the joint.

[joy ride]

I noticed that the report said that the edges of the panel and the hole in the fuselage would be rounded. Would they both be convex with an "hour glass" section of sealant, concave with a "circle" section of sealant, or a convex meeting a concave and a unison thickness of selant?

I believe I did spot the word "sealant" and assume this would be a specialist adhesive/resin rather than bathroom sealant!

[A and C]

I think the report you have seen is wide of the mark by some considerable distance.

I have nothing to add to the very good posts by Volume.

[Capot]

The Boeing method seems to be very similar to what has been done with GRP boats for decades, although in a different order, for relatively small damage to hulls.

With a boat, you clean up the hole/damage, usually squaring it off, and then bond a patch on the inside of the hull, but at least 4X its area , so that it overlaps the hole by a lot. The patch is the same thickness as the hull. The patch must follow the curve of the hull precisely, very difficult with a double curve. This patch is the strength of the repair.

A second patch, also the same thickness and curve as the hull but fitting the hole very accurately, is then bonded into the the hole itself. A really skilled worker will reverse scarf it if possible.

The gap is then made invisible with gelcoat matched to the hull.

Insead of pre-manufactured patches, a yard may plug the hole and then lay several layers of GRP to the same strength as the hull over the plug and surrounding GRP, then remove the plug and when the first stage has cured lay more GRP on the outside, in the hole, finishing off with gelcoat over the whole repair. This method is best when the curve makes a pre-made patch impractical.

With a boat, the pressure is from the outside, below the waterline. With the aircraft it is from the inside so this method would be even stronger.

[tdracer]

how thick is the 'panel' here?

I assume we are talking <2mm? so not much point in "scarfen the edges"?

No first hand knowledge of the area in question, but based on the composite fuselage pieces I have, seen I'd say 1/4 inch minimum (~6 mm), probably closer to 3/8 inch (~9 mm). Granted, I never actually measured anything, but visually I was a bit surprised at how thick they were (then again, I had a similar reaction the first time I saw an aluminum fuselage skin - they are thicker than most people think). Remember, unlike that access panel that fell off in India, we're talking primary structure here.

[A and C]

Your boat repair may work and deal with the load transfer but at massive weight increase, as for filling in the gaps with gel coat I think that is just setting up for further problems in the future.

The whole point about the repair techniques so well discribed above by Volume is that the repair when finished is exactly the same as the original structure both in load transfer and weight.

What we are seeing above with all this talk of patches is a metalcentric view to load transfer and an assumption that the " glue" joint is weaker than the original structure, this is simply untrue, the "glue" or more correctly resin IS exactly the same as the original structure and so correctly installed will react exactly like the original structure. Therefore no additional patches or plates are required as long as a sufficient scarff area is avalable.

[TURIN]

Another airline has already had a skin puncture repaired as described, clean up the damage to a defined shape (in this case it was an L shape) scarfed edges, drop in a plug of the same dimensions.
You can't see the join. Admittedly, this Ethiopian job is much bigger but the principle seems the same.

[Capot]

A & C
I intended only to remark on the similarity of the approach developed over the decades for GRP boats and the method devised by Boeing for its aircraft.

There is NO suggestion that the standard required is remotely similar in any respect, or that the details of the process are or even could be the same!

[Volume]

I assume we are talking <2mm? so not much point in "scarfen the edges"? Typically we scarfen unidirectinal CFRP 1:50, so that would give a 100 mm scarfened overlap.
Depending the exact layup of the barrel the value might be a bit lower, as it for sure is not fully unidirectional.
Some Information from a very old glider repair handbook (http://www.8kcab.com/aswlib/ASW20%20Repair%20Manual.pdf) (all glassfibre)

[poorjohn]

A and C: What we are seeing above with all this talk of patches is a metalcentric view to load transfer and an assumption that the " glue" joint is weaker than the original structure, this is simply untrue, the "glue" or more correctly resin IS exactly the same as the original structure and so correctly installed will react exactly like the original structure. Therefore no additional patches or plates are required as long as a sufficient scarff area is avalable.Why shouldn't it bother me that there's no continuous carbon fiber running through/across the new joint?

[A and C]

In answer to your question.............Because a properly executed scarf joint replicates the load transfer property's of the original structure.

When doing such repairs normally a test sample is made and sent to the aircraft manufacturer for destruction testing, we have never had a test sample fail to meet the new specification and on average the test samples are 1-3 % stronger than new items.

[MurphyWasRight]

Why shouldn't it bother me that there's no continuous carbon fiber running through/across the new joint?

Poorjohn


In answer to your question.............Because a properly executed scarf joint replicates the load transfer property's of the original structure

One way to think of this is to consider 2 hypothetical joints:

At one extreme would be a "butt" joint with resin (glue) in the gap, in this case there would be no fibers "across" the joint.
BTW: Does not matter if the resin or composite is stronger (actually stiffer) this creates a discontinuity / stress concentration aka not a good thing.

At the other extreme is a joint made by taking two barrel sections and tapering each from full thickness to none over the full length so one exactly fits inside of the other.

In this case there will be continouse fiber over the entire joint, although none transitions from one section to the other.

A scarf joint is similar to the second case expcept for the overlap distance.

BTW: Although I have some understanding of stress and transitions etc I am not a composites expert (at all) so feel free to correct/clarify the above. I am writing this partly to clarify my own understanding.

[barit1]

Scarf joints in wood (same situation, no continuous fibre, but substantial overlapping of parallel fibres) have been successfully used in both new construction and field repair. For perhaps a century!

Beveling wing skin plywood for scarf joint

BTW, the Howard DGA-8 has a Vne of 250 kt.

[fenland787]

Scarf joints in wood ..... have been successfully used in both new construction and field repair. For perhaps a century!
Well actually even longer than that! The burial ship at Sutton Hoo which is thought to date from around 620 AD was found to use splayed scarf joints. I think that is thought to be the oldest known use in the UK but that means they were probably used elsewhere in Europe even earlier.

[DaveReidUK]

I haven't seen this previously reported, but around the time that the ETH 787 repair was starting at Heathrow, a mile or so away in the BA hangars the 787 that was hit by a truck at Toronto last week was undergoing repair, reportedly involving a titanium patch applied to the damaged baggage door.

[A and C]

So a technically poor repair has been carried out to enable the aircraft to return to service quickly, this is not unusual and the reason an aircrafts weight will grow during years of service.

The big question is if BA considers the extra weight and the disturbance of aerodynamic profile an issue that requires attention at the next major maintenance check.

[gas path]

Er! the repair to the BA a/c was no more than the replacement of a Ti edge protector strip to the forward cargo door. Unfortunately it had to come from the manufacturer, (in this case China) so it took over 24 hours by the time it had been shipped and gone through customs etc. These sacrificial edge protectors are in segments around each door aperature.

[DaveReidUK]

Thanks for the clarification, GP. It did seem rather strange that a permanent metallic repair would be made to a door, with the associated weight and aerodynamic penalty, rather than simply replacing it. That the repair was to the protective strip around the aperture makes much more sense.

[Dave Cummings]

Hi
Does anyone have any further info on this repair to the BA.787 like the reg of the effected airframe and which door had to be replaced/repaired?

[Mechta]

Having assisted with a repair to a glass fibre glider fuselage, it is worth noting that it considerable effort was taken to make sure each layer of glass fibre matched that in the original fuselage in both type density and weave of glass clothas well as the direction of the fibres. The repairer in this case was a graduate of one of the German Akaflieg universities where they tend to know their stuff about composites.

The technique used was to mark both the material to be removed and the remaining structure to ensure correct alignment of the removed portion, then to burn off the resin on the edges of the removed portion to expose the fibres in the glass layers to ascertain the fibres' orientation.

[poorjohn]

the forward cargo door. Unfortunately it had to come from the manufacturer, (in this case China)Made me wonder how Boeing plans to make replacements of all the bits and pieces available later in life. Did they in every case obtain the rights and capability to build replacements themselves if made necessary by the demise or disinterest of the OEM?

[andrasz]

Did they in every case obtain the rights...

You're holding the sheet upside down. It is Boeing who has all the rights, and licenses manufacturing to various suppliers. Subject to terms of agreement they can withdraw that license and give it to someone else or do the job themselves. Been like that since the times of the 247, nothing new.

[speedbump59]

The article says that for the repair, Boeing fabricated a complete new fuselage barrel, and then cut it to pieces to make a new patch. That just seems so wrong.

I trust they already looked at it in lots of detail, but I would think the smarter repair would be:


Cut out a few test pieces from the burnt section. Test them to see how much strength was lost (and I expect it would really not be that much).
Make a temporary patch to bring up the strength to the necessary level (if needed at all).
Fly an unpressurized flight back to the factory (to reduce the stresses on the body and patch). Can you imagine if Boeing was able to fly the airplane back to the factory (even if unpressurized) with little or no repair work done first? That would really impress people with the strength of Boeing's "plastic body".
Replace the whole barrel in the factory.

Maybe the above method would cost a little more, but you would have an airplane just as good as brand new. Just as strong, with no weight penalty, and no risk of any future "de-patching" problems.

But now, with the "patch" everyone will be looking at this airplane as "damaged goods" and just waiting for the top to pop off at altitude.

I think this airplane is a great candidate for a new paint job and a creative advertising company to market their stop-smoking products (patch).

[olasek]

and then cut it to pieces to make a new patch. That just seems so wrong. No, it isn't wrong. As they said the fabricated piece was cut up to be used for other potential future repairs.
Replacing the whole barrel was looked at and it was deemed way too costly and risky due to cutting/reconnecting countless lines that run through it.

[A and C]

All you have shown is how little you understand about load transfer within a composite structure and how these structures can be repaired with almost no increase in weight.

To call the repair a patch is incorrect what Boeing are doing is inserting new structure into the hole and bonding it into place using the scarf technique.

The only people who would see this sort of repair as damaged goods are those who know nothing about the subject.

Please read the posts by Volume & Barit1, these guys have a true understanding of the subject.

[NWSRG]

But now, with the "patch" everyone will be looking at this airplane as "damaged goods" and just waiting for the top to pop off at altitude.

Not so sure...given that an aluminium aircraft may have been written off by the same incident, I think this one will stand Boeing in good stead. They couldn't have had a better demonstration that they have the ability to repair a major composite damage in the field.

[joy ride]

I think it is a mixed bag for Boeing. Although the cause of the fire seems not to have been Boeing's fault, the bad publicity has cast further public and industry doubts on the 787.

A good repair will be great news, and increase confidence in the chosen material, but the length of time and complexity of the repair operation, plus its costs, including airport fees and lost revenue, is going to be high.

I eagerly await progress eagerly.

[phiggsbroadband]

I think there is a lot of hype going about, questioning the strength of any patch repair. It is not beyond reason that Boing could take the opportunity to make that hole into an escape hatch, in case of any water landings. Or even a celestial observation dome for those passengers who may be amateur astronomers.
There are many other openings into the fuselage, that just have hinges and locks as the strength bearing mechanism.

[MurphyWasRight]

Quote:
and then cut it to pieces to make a new patch. That just seems so wrong.
No, it isn't wrong. As they said the fabricated piece was cut up to be used for other potential future repairs.
Replacing the whole barrel was looked at and it was deemed way too costly and risky due to cutting/reconnecting countless lines that run through it.

Only thing that puzzles me is why cut up the remainder at all.
Seems that keeping it as whole unit would allow for a better chance of having the required segment available for random shaped damage than trying to predict in advance where to cut.

Could be based on cost to store the full article vs sections or possibly they are only cutting it into into a couple of easier to store pieces based on "cant cut here anyway" lines.

[olasek]

Only thing that puzzles me is why cut up the remainder at all.
Perhaps I misspoke and there was no cutting mentioned in this news segment, possibly it only said that the whole barrel will be kept in inventory with future fixes in mind.

[MurphyWasRight]

Perhaps I misspoke and there was no cutting mentioned in this news segment, possibly it only said that the whole barrel will be kept in inventory with future fixes in mind.


Thanks makes sense.
Would not be surprised if some of the news reports did say they would cut it up in advance of need.

Any time I have seen news reports on something I have first hand knowledge of I am amazed at how creative reporters can be.

[tdracer]

Any time I have seen news reports on something I have first hand knowledge of I am amazed at how creative reporters can be.

"Creative" is a lot more polite than I would have phrased it. Anytime you get reporters reporting on a subject that they know little about (which appears to be most of the time), the results tend to be somewhat sketchy.

[Volume]

the whole barrel will be kept in inventory with future fixes in mind.The first airline to experience a tail strike will be more than happy to buy the lower portion of that barrel...

Cut out a few test pieces from the burnt section. Test them to see how much strength was lost (and I expect it would really not be that much).
You are again metal minded (nothing bad, that´s what 99% of the aviation people are). If you "cut out" a test piece it will fail where you clamp it into your text fixture. Composite test pieces must be especially designed and build to really load them realistically and get test results you can work with. Coupon testing of composites just makes sense for certain specific properties, otherwise you should test larger pieces of substructure.

Replace the whole barrel in the factory.That would require a design of the joints to allow for re-drilling and using oversized fasteners. I am not sure whether Boeing has designed the barrels for that. The fact that they had to remove the window at the joint seems to indicate that it is just barely possible to do the joint with no strength penalty. Re-doing the joint by re-drilling the holes may not be possible. Just like you can not do a simple rivet joined in the pocketed area of a chemically milled fuselage skin, the composite layup needs to have higher wallthickness and different layup for bearing strength in the area where you want to install fasteners. Unless you build your aircraft from "black metal" and waste a lot of weight on panels which are strengthened for fasteners everywhere. As we did in the past, just to allow riveted patch repair everywhere.

If Boeing is doing the composite repair right, using the same technique that is used in small composite aircraft since 1956, and regularly inspects this repair during the remaining life of that aircraft to collect data, potentially doing a destructive test of that repair once the aircraft retires, then this incident and the according repair may mean a quantum leap in large aircraft composite design. It would mean we finally build and repair large composite aircraft, not large aircraft from "black aluminium" anymore. This could be the long term test that should have been done 20 years ago to get confident in real composite repair.
In 20 years we will laugh about riveted titanium patch repair of composite aircraft, just like the small aircraft industry is laughing about what "the big guys" do up to now.
And maybe some day we will even learn that there are more clever ways to build composite aircraft than using stringer stiffened shells and ribs/frames with mouseholes cut into them joined by clips, cleats and fasteners...

[manrow]

Everything seems to have gone quiet on the in-service performance of this aircraft. That could be because Boeing have fixed all the problems, although that seems unlikely as some of the well-publicised problems are not going to be quick fixes.
The airworthiness authorities are presumably happy with operations continuing, so what is the airlines experience?
Apparently the flight crews love it, the engineers are not so happy as a result of almost constant modifications, and the travelling public are happy if their intended flight on a 787 occurs at all.
Sounds a win win to me.

[Tray Surfer]

I work on them and I am very happy...

[olasek]

constant modifications
Probably a gross exaggeration. Yes, some tweaking, etc to improve reliability is to be expected with any aircraft within first years in operation, 777 was going through the same phase.

[tdracer]

Boeing is quoting 97% dispatch reliability - which isn't great but also isn't horrible for a new airplane (I remember one operator at 80% for the 747-400 a year after EIS :eek:). I'm no longer hearing the claim that the 787 is better than the 777 was at the same point after EIS so I'm guessing it's not :rolleyes:.

Problem areas appear to be electrical power and APU.

[Wannabe Flyer]

Not sure if this is being reported but seems to be at least twice a week in the news with this carrier

Snags soar in Dreamliner but Air India gets 10th aircraft | Firstpost (http://www.firstpost.com/business/snags-soar-in-dreamliner-but-air-india-gets-10th-aircraft-1214867.html)

However who ever has flown it says it is a beauty....

[nitpicker330]

Yep and when they finally bed down the niggling issues she'll be even better.

Can't beat a Boeing. :ok:

[newvisitor]

Recent composites conference, talk by Learjet/BBD about the Learjet85 development and certification - synopsis at Bombardier sheds light on Learjet 85 composites manufacturing : CompositesWorld (http://www.compositesworld.com/blog/post/bombardier-sheds-light-on-learjet-85-composites-manufacturing?goback=.gde_1327417_member_5804436627421945856 #!)

quote of relevance "Harter related that after processes were optimized, Bombardier faced the daunting task of achieving FAA certification. Much like the Boeing 787 and the Airbus A350 XWB, intensive use of composites on the Learjet 85 meant Bombardier had to perform extensive testing to satisfy the FAA’s special conditions for certification. Much of this, Harter said, focused on in-flight flammability, post-crash flammability, crashworthiness, durability, toxicity in burn, damage tolerance and thermal expansion at interactions with metals. Results, across the board, were positive. In fact, noted Harter, composite materials on the Learjet 85 outperformed aluminum in flammability and crashworthiness tests — a fact that he believes needs to be emphasized more by the aerospace composites professionals. Composite readiness testing is now complete and certification testing has begun."

Even if you discount for spin, interesting statement.

Also, with apologies for long delay in posting the following comment, I was at a major conference in the summer, where I had a chance to speak to two key (composites flammability) academic experts quoted by Amicus earlier in the thread. I posed them the question "two airplanes side by side, one aluminum, one composite, both on fire, which one would you rather be in?" One answered they would rather be in the composite airplane, the other said it made little difference.

[speedbump59]

If the replaced area of composite is going to be relatively large (more than a couple of square meters or so) I will be quite amazed if they can just brush a bit of resin on a scarfed joint and call it good to go.

Even if it is scarfed, since there will be no carbon fibers running through the glued joint, it seems difficult to believe that just a resin bond will stand up to 20 or more years of flexing and pressure cycles. I would think they would need the composite equivalent of a doubler plate across the joint to be sure.

I don't remember exactly why, but I seem to remember that for some of the very early build 787's weren't some of the fuselages disassembled and reassembled (maybe even more than once)? In that case, it seems clear that the fuselage barrels can be replaced if necessary. It may mean some new connectors in the electrical cables and hydraulic lines, but there are already plenty of those on the airplane.

Of course Boeing is very keen to show the world that it is not too difficult to repair even a large area of composite. But I really hope that they are not going to regret their decision to patch the airplane instead of replace the whole barrel.

[A and C]

Speedbump59

They say when in a hole stop digging !

A scarf joint replicates the way the original structure transmits the load, that is why it as strong as the original structure, the fact that Boeing lay up the structure with a wound filament is all about efficient construction rather than a need from a structural point of view and in reality each layer of the wound filament could be veiwed as one very long scarf joint.

Until you rid yourself of you metalcentric way of viewing structures you will never understand composites.

[gas path]

It will not be 'scarfed' in.;)

[olasek]

newvisitor - excellent post, too bad it wasn't here months ago when the 'composite hysteria' was in full swing.

[speedbump59]

A and C:

A scarfed joint is simply a slightly improved butt joint. With no fibers going through the joint, it does not have the same strength characteristics as the surrounding material.

Your concept of an "infinitely scarfed joint" is very nice! However it precisely highlights the reason that a scarf joint would not be used: the weakest direction in a composite is in the direction that there are no fibers, i.e delamination.

In my opinion, a simple scarf joint cannot be used for this repair. There will need to be a significant lap joint most likely with some kind of reinforcement (either interally bonded to the composite or something similar to a riveted doubler plate).

The reason for this is that for a large area of repair, strains become more critical than stresses. And a simple scarfed joint will not be able to tolerate those strains (flexing due to flight and pressure cycles) for any significant time period.

I will be happy if I am proven wrong and learn something new, but for now this is my story and I am sticking to it.

I hope that we will soon learn the details of the actual repair method so that one of us will be eating crow for dinner!

Disclaimer: the above comments have not been reviewed for accuracy by the Society for Metalcentric Thinking.

[crippen]

http://www.annular.org.uk/wp-content/uploads/2009/03/gs-finger-joint_hr.jpg


how it is done with wood.

[A and C]

I am guessing that you have never been involved In composite repair because you simply lack understanding of the subject, the company that I am involved with has been involved with the maintenance and repair of aeronautical composite structures since the late 1960's and myself have been involved since the early 90's. I am the guy who puts his name to the release to service paperwork......... We have yet to have a structural problem with an aircraft we have repaired.

Unlike a metal repair were you aim to have the edges of the repair very smooth to avoid inducing a fatigue crack the surfaces of a scarf joint are comparably rough and I am sure that under a microscope the fibers would look fluffy. This results in both sides of the repair being slightly porus, this allows the resin to soak into both sides of the repair and the fibers to intermingle within the joint in the same was as within the original structure.


As I have said before all critical structural repairs are subject to samples being tested to distruction by the original manufactures, these samples usually fail at 1-3 % above the average fail point for new items........ We have never had a test sample fail to meet the new specification.

The fact of the matter is that Boeing would never have built an aircraft structure using a totaly new Technology, composite structure has been about in aviation for 50 years now and bonding Technology since the Wright brothers, metal bonding since the DH Comet and Dove so the techniques for repair are well understood by all except the metalcentrics.

I have no idea what Boeing are planning for this repair but if it is not a scaf respair the wieght will go up for little structural advantage,

[pgarner528]

Sorry Crippen, thats a finger joint not a scarf joint. They are completely different.

[barit1]

Sorry Crippen, thats a finger joint not a scarf joint. They are completely different.

Well, not so completely different after all. Similar in principle (parallel orientation of spliced fibres), sort of a multiple scarf joint rotated 90 degrees, but the finger joint is used on thicker stock.

[crippen]

I know !! Just saying like.

:ouch:

[ATC Watcher]

I am completely novice in the field of large aircraft composite repairs. However I fly regularly in composite aircraft ( high performance gliders) and there when a (large) repair is done it always adds weight ( unlike in repairs in aluminium or wood/fabric) . For aerodynamically fine tuned gliders , if repair is in fuselage it can affect CG, if it is in or near control surfaces it can add instability and sometime vibrations at certains speed .
Is this irrelevant in large aircraft such as the 787 ?

[MrSnuggles]

What type of scarf joint do you believe is the most probable?

Some types of scarf joints need removing of rather large areas of original materials to be proven effective and as strong as the original type. From the side they would look like very sharp dart-like objects, one on top of the other, a bit similar as in crippen's post.

Other scarf joints are more like "step" joints (sorry, non-native English writer here..) where the "steps" can be subject to stress and creep but this saves on material.

One of the most material effective scarf joints is where you cover a piece of the original material with the repair (whilst doing this "step" joint - sorry for not knowing the proper name!), this would lead to a "bump" and may affect aerodynamics. My guess is that something like this is what happened to ATC Watcher's glideplane.

[Ian W]

I would expect that when the repair is finished the engineers involved will generate a 'paper' for one of the aviation engineering journals. This may not satisfy the 'peanut gallery' but for those in the business it will be welcome elucidation of the repair and repair technology used. An effective repair with no limitations on subsequent operations of the repaired airframe will be extremely good news for both Boeing and Airbus.

[A and C]

The amount of weight a repair adds to an area of structure largely depends on the skill of the guy doing the job, there will always be some extra weight but it will always be a lot less in percentage terms than a metal repair.

Scarf joints are usually stronger than the original material by a small percentage, on a wooden aircraft you always make a test sample using off cuts of the wood you have used and the glue, once the glue has cured you take a hammer to the joint, if the wood fails that is good, if the glue fails then you have to re-do the job.

Composite work is much the same as wood when it comes to scarf joints except the glue is replaced by resin that is exactly the same as the original structure so as long as you have room to get the correct amount of scarf area there is no need for for extra structure as all you are doing is replacing like with like.

The most exacting repairs are on glider flying controls were the allowable extra weight is measured in grams, depending on how well the original manufacture was will determine if the control surface has enough margin to make a repair.

[olasek]

the engineers involved will generate a 'paper' It may not happen after what they had said before that the method of repair was a confidential matter between Boeing, Ethiopian and the insurance co.

[poorjohn]

It may not happen after what they had said before that the method of repair was a confidential matter between Boeing, Ethiopian and the insurance co.Don't the FAA and its various equivalents have to agree that the repaired aircraft is airworthy?

[lincman]

That type of repair would be done by Boeing employed FAA DERs (Designated Engineering Reps.) and most likely using the FAA 8110 form, which at some point is submitted to the FAA. So it is highly likely the FAA will have a lot of oversight of the repair.

[olasek]

Don't the FAA and its various equivalents have to agree that the repaired aircraft is airworthy?
Yeah, but it doesn't necessarily mean FAA will make public the method of repair. There was a similar story with the 787's lightning protection during certification, FAA had to approve it but Boeing made sure no specifics got to public domain (they even intervened to snuff out some early press leaks/drawings) claiming their system is highly proprietary.

[MrSnuggles]

I do not question the strength of composite repairs. I am sorry if I implied such a thing.

Only thing I was pondering was how the joint would look. There are several ways to join composites and I may very well have used the wrong words.

I was thinking that the sharp long angle scarf joint would be preferred (due to strength etc), but the negative with this approach would be that a lot of unharmed material would have to be removed.

Then there are scarf joints that looks like small steps and of these there is one that I suppose have been used on the aforementioned glider.

Sorry in advance if I use wrong words. I am not familiar with the technical terms in English. I really should try to find pics to explain how I mean...

[mickyman]

Isn't it a mute point with 'fixing composite materials' that its taken this long to fathom out just what to do/how to proceed/fix the 787 - three months + from the incident and are we any nearer solving the problems?

[MrSnuggles]

This is what I mean when I say scarf join:

http://www.jimsboats.com/scarf1.gif

Obviously Boeing would use something more like length = 15 times thickness or so.

But there are many other types of scarf joins, some that looks like steps and they can be with or without "pegs" going through the material (no such join shown in this pic but often used in wood):

http://pic3.picturetrail.com/VOL12/1104763/2595357/70507451.jpg

And here is one that has small "steps" where the join overlaps and creates a thicker material over the join. Maybe this happened to the glider. I do not find it credible that Boeing would use this method on the 787 though.

http://pressurevesseltech.asmedigitalcollection.asme.org/data/Journals/JPVTAS/28543/007006jpv1.jpeg

[gas path]

It will not be a scarfed in joint!;)

[olasek]

and are we any nearer solving the problems?And what problems are WE supposed to be solving? :rolleyes:

[mickyman]

olasek

I use the term 'we' royally....

Static aircraft fire.......no repair after 3 and a half months.....

or did I miss the aircraft departing Heathrow and returning to service?

If there wasn't a few problems to solve the aircraft would have flown by now wouln't you think?

[olasek]

If there wasn't a few problems to solve the aircraft would have flown by now wouln't you think? Yeah, there were a few problems to solve, the whole engineering analysis took months, agreement between various parties, FAA, etc. so what's new??

[Nige321]

It will not be a scarfed in joint!
So what type of joint will it be...:ugh:

[A and C]

Normaly if there is room on the structure you would use what you have termed a traditional scarf joint with a face exceeding 15:1.

We have a contributor on here who keeps telling us that this won't be a scarf joint, perhaps he would like to illuminate us with his reasoning ?

[Volume]

A scarfed joint is simply a slightly improved butt joint.A scarfed joint is an improved lap joint !
The peak stress in the bond line is "slightly" improved by factors of 50 or so compared to a lap joint, and "slightly" improved by factors of 500 or so over a butt joint.
For those who understand metal:
If you do a riveted lap joint with one row of rivets it is bloody simple to calculate. (at least if you cover the excentric issue by corrective factors for your rivet strength, which is readily avaible in the MS standards or in the SRM of your aircraft). If you do a riveted lap joint with two row of rivets, it is still all easy, the load is distributed 50/50 to the two rows. However, using flush rivets the first row is still the more critical one, as the "bypass" load around the rivets lacks the additional material of the countersunk, but that is a relatively small effect.
Now it becomes tricky, if you do a 3 row rivet joint you no longer have an even load distribution, it will be an (around) 40/20/40 load distribution. If you increase the number of rivet rows, the loads of the critical rivets do not reduce further significantly. If you would do a 10 row rivet joint, the center 4 rows of rivets will be practically free of loads, while the first row of rivets will still transfer around 25% of the load.
This can be compared to a simple bonded lap joint, the edges of the bond line do carry most of the shear stress, the center area does not transfer any laods (and that is the portion perfectly protected from all environmental influences and hence the most durable portion...).
What would you do for a riveted metal joint? You would use stepped wallthickness, you would design "fingers" on the sheets to reduce cross section according to the desired load carried. This is exactly what you would do for a bonded joint, you adapt wallthickness to the amount of load you want each sheet to carry. If you adapt it fully from full thickness to zero (practically not possible), you get a constand bondline load, hence significantly reducing the peak stress at the most vulnerable edges. As a secondary effect you also reduce excentricity of the joint, reducing secondary bending stress.

Woodworkers do it that way for centuries, and it works.
If you look at an old, crashed wooden aircraft, you typically see the wood broken, not the glue joints.

Additionally you should always remember that there is nothing like a "continuous fibre", you always have some ruptures in the filaments so it is absolutely normal that indivindiual fibres do transfer their load to neibouring fibres via the resin. This creates the famous "inherent damage tolerance" of composites material. When single fibres fail locally, their load is taken over by other fibres. Already during manufacturing of the fibres you produce a lot of broken fibres, and during part manufacturing you add more of those. Additionally not all fibres are perfectly straight, perfectly parallel or perfectly tensioned, there will always be some fibres with "slack". However, load will always be transferred to the "best" fibres via the resin matrix.
In a bonded joint exactly the same happens. The only issue is to prevent the bondline from deterioration due to the environment and from secondary stresses due to misalignment, impact etc. Therefore periodic inspections of the repair may be required. Just like you would do for a riveted metal repair.

[speedbump59]

Whatever the design of the joint will be, it is probably being done these very days by skilled craftspeople, separated from our curious eyes by just a single layer of canvas tarp flapping in the breeze at LHR.

Really it would be great if there was somebody who could poke their head under the tarp for a few minutes at LHR, or surreptitiously take a peek at a drawing or two at Boeing's design office.

Given the amazing amount of "inside" information that sometimes pops out on this website, I am really hoping for something on this quite soon.

[lincman]

There's a pic of the aircraft under repair at this link. All looks very neat and orderly.

http://cdn-www.airliners.net/aviation-photos/middle/5/2/6/2344625.jpg

[speedbump59]

On condition of anonymity, this engineer explained the likely repair process.
Boeing will cut out the skin damaged by the fire probably in a rectangular cut with rounded edges, he said.
It will cut the patch to the same size and shape and drop it into the space as a plug. The tiny gap around the patch will be filled with paintable sealant that will stretch and compress as the fuselage is pressurized and unpressurized.
Then mechanics will work on the inside, gluing a splice plate to the original skin and to the patch, overlapping both by about 4 inches.
The glue is a superstrong adhesive that is cured using heat blankets that are held under pressure by vacuum bags applied to the area.


The above was published in Seattle Times, 21 October. If correct, it should stop the discussion on scarfing the joint.



Speedbump

[MrSnuggles]

From speedbump59It will cut the patch to the same size and shape and drop it into the space as a plug. The tiny gap around the patch will be filled with paintable sealant that will stretch and compress as the fuselage is pressurized and unpressurized.
Then mechanics will work on the inside, gluing a splice plate to the original skin and to the patch, overlapping both by about 4 inches.

Interesting... this is a somewhat unexpected approach. Sounds like a mix between metal repair and wood repair. My spontaneous(sp?) reaction is that I would want to invert the plug method (that is, inserting it from the inside), but if it works, it works. Would love to see a paper on this!

[joy ride]

Thanks for that, speedbump59, I am fascinated by all the talk here of how this repair will be done. That sounds like a surprisingly "primitive" way of repairing it compared to some suggestions here, but being familiar with wood and metal work it also sounds "good" to me! I am eager to find out exactly what is done and hope in the fullness of time we will know for sure.

[Lemain]

I am very uneasy about this. Long before any novel material is decided upon for production of civil aircraft repair should have been investigated and repairs exhaustively tested in lab and field conditions. For repairs carried out ex-factory or specialist repair workshop, the means of carrying out such repairs should have been tested at remote non-specialised workshops.

That it has taken almost four months to decide how to do it is deeply concerning and implies a serious oversight in the design and production programme. Certainly the method of repair should be in the public domain, including all test data taken, confidential proprietary information or not. It is only by publishing the full details to the wider engineering world that peers can comment. If there is a paper, it sounds as though it won't be peer-reviewed and won't have had any proper field trial.

[MrSnuggles]

From Lemain:

I am very uneasy about this. Long before any novel material is decided upon for production of civil aircraft repair should have been investigated and repairs exhaustively tested in lab and field conditions. For repairs carried out ex-factory or specialist repair workshop, the means of carrying out such repairs should have been tested at remote non-specialised workshops.
Carbon fiber composites are not new materials, although being a bit novel to the aircraft world. There are plenty of repair technology documentations.


That it has taken almost four months to decide how to do it is deeply concerning and implies a serious oversight in the design and production programme. Certainly the method of repair should be in the public domain, including all test data taken, confidential proprietary information or not. It is only by publishing the full details to the wider engineering world that peers can comment. If there is a paper, it sounds as though it won't be peer-reviewed and won't have had any proper field trial.
i) The lenghty process could very well have been due to insurance questions, responsibility division, contract agreements etc, as others have pointed out.

ii) Yes, a paper would be most interesting but I venture a guess that that won't happen. Sadly, because this is a very interesting case due to the placement of the damaged area.

[Lemain]

clandestine Carbon fiber composites are not new materials, although being a bit novel to the aircraft world. There are plenty of repair technology documentations. The materials used in the Comet 1 were not 'novel' in themselves. With a 200 tonne+ heavy jet flying at near the speed of sound, with 15 psi internal pressure, for fifteen hours a day in turbulence, taking off and landing, the airframe is in a very severe environment, hard to replicate in the laboratory. Forces, changes in force magnitude and direction, vibration, temperature and chemical/moisture attack are hard to replicate in any faithful manner together as a complete structure. With a new aircraft, tens of thousands of hours are flown in real conditions long before the a/c enters service.

Yes, a paper would be most interesting but I venture a guess that that won't happen. Sadly, because this is a very interesting case due to the placement of the damaged area. I don't think that 'most interesting' is the appropriate term. It is vital that the proposals are peer reviewed by a range of materials and aviation specialists if the repair is going to be tested on the public (or line flight crew, come to that).

[MrSnuggles]

Lemain.

1) Yes, and...?

2) You are correct, that would be most helpful. I hope that a paper will be released, but not holding my breath over here... where there's money there always is an incentive to keep things proprietary...

[Lemain]

1) Yes, and...? Indeed. That's the issue. Even if you wrote-off this hull you are going to face another ding before long. They happen and when they do you don't expect the Mfr to sit in smoke-filled rooms deciding what to do for the next four months - and then come up with a solution that is essentially un-tested. You know what I'm saying but nobody wants to come out with it. The only way for damage limitation in this product (and loss of public confidence in the Industry) is for the Industry as a whole to address the problem and not treat it as 'proprietary'. I can't see a safe alternative.

Heaven forbid they'll be a bad outcome and I'm sure many of the best minds have looked at it. Out of curiosity, I wonder if the decision-makers have indemnity insurance covering this?

[joy ride]

I think it was closer to 3 months to prepare for the repair a five weeks estimated repair time. Perhaps a good deal of the three months was putting into action a well-researched operation, but Boeing did apparently build a whole new rear fuselage barrel to cut the repair patch from. I presume this would have taken quite a while, and in the mean time they had to plan/hire/build the shelter and heating/ventilation equipment. There is quite a lot of "stuff" there; sourcing, making and/or hiring all of that would take a while, especially as composites need controlled stable environments, and winter at LHR is hardly stable!

[Lemain]

I think it was closer to 3 months to prepare for the repair a five weeks estimated repair time. Perhaps a good deal of the three months was putting into action a well-researched operation, but Boeing did apparently build a whole new rear fuselage barrel to cut the repair patch from. I presume this would have taken quite a while,Presumably the need to cut out of a new whole section is to preserve the pre-stressing inherent in the manufacture of a whole section? Obviously they wouldn't have done so if a section could have been laid by itself, so it must presumably must be in order to match the original. I presume that the problem is strain rather than stress and that the composite is anisotropic - i.e. the Young's modulus is not the same in all directions. This would affect the natural frequency of the section and it's possible that unexpected resonances would show up after completion of the repair. Resonances are likely to be a greater risk than absolute strength.

I wonder what this tells us about the cost and time to repair less sensational cases such as collision damage on the ground. Could be very expensive for the insurers.

....and in the mean time they had to plan/hire/build the shelter and heating/ventilation equipment. There is quite a lot of "stuff" there; sourcing, making and/or hiring all of that would take a while, especially as composites need controlled stable environments, and winter at LHR is hardly stable! Many composites need stable environments when curing and until the final seal is applied (to prevent ingress of water) but a panel from the factory should be fine to handle. Obviously the outside and inside surfaces are completely safe as they are designed to resist moisture, ice, glycol, salt and common cleaning fluids and I presume that the edges will have been treated with a suitable sealant. The prepared edges of the a/c hull section are susceptible to ingress of water though environmental control beyond a normal maintenance hangar is unlikely to be needed. A plastic tent around a given section is a well-established technique and can be set up over a weekend. If it needs more than that I would be surprised.

[A and C]

While not being in a position to say exactly why Boeing have decided on this plug repair it seems like it has not been driven by conventional composite repair techniques but it has rather more in common with metal repair techniques.

I would be very interested to see the compleated repair and find out quite why Boeing went down a road that seems to abandon the advantages of composite construction.

[MrSnuggles]

A and C:
While not being in a position to say exactly why Boeing have decided on this plug repair it seems like it has not been driven by conventional composite repair techniques but it has rather more in common with metal repair techniques.

Been pondering over this during the day and one thing I realised... MAYBE it is because the damage is so close to the tail fin. This would MAYBE make the scarf joint unreliable (because there would be less material for the angle on one side) regardless of pegs, nibs and hooks, and thus they opted for this intriguing solution. Very interesting indeed.

[gas path]

Speedbump... that's fairly close.
joy ride etal... The Boeing repair teams never turn up on site until they have absolutely everything in place and ready to go.
http://images.ibsrv.net/ibsrv/res/src:www.pprune.org/get/images/smilies/nerd.gif

[NWSRG]

It's important to remember that no-one could have anticipated a damage of this nature.

Had this been a metal aircraft, it would surely have been damaged beyond repair. But with the 787, the composite structure gave Boeing a change to salvage an aircraft that otherwise would have been written off. And while Boeing have no doubt developed detailed plans for dealing with normal 'ramp rash', this repair has probably been developed from first principles.

So 5 months is not unreasonable, in fact, I think its pretty impressive to think that this frame will be flying again in a few weeks.

This could turn out to be a remarkable testimony to the ability of a composite aircraft to sustain major, yet repairable, damage. Boeing will gain invaluable data on such a repair.

And hopefully a paper will come out to tell the story...who knows, maybe the Discovery Channel is in there with them!

[Old Engineer]

Well, from an engineering standpoint, as I see it:

The replacement section is already on site;
The interior finish reeks of smoke and hazardous particulates, and so is likely already out...

Just disconnect the various lines, unbolt the damaged section, and bolt the replacement section back in, shim to align as required. Replace or renew the lines. Cover with new interior.

Whisk the damaged section back to the factory; make whatever repair might have been contemplated at some time, and test at leisure to see if it would have worked.

Why take any chances? So let people think that a marvelously cheap repair has been devised, since that seems to be the drift right now. But just do the sensible thing.

We used to sometimes say in the engineering office that sometimes it's cheaper just to do the job. And I'd say, it always was.

OE

[barit1]

The Boeing repair teams never turn up on site until they have absolutely everything in place and ready to go.

Harr-UMPH!

About 25 years ago I was assigned to a project across the pond. I had never been associated with this hardware set to that point, but was assured it was "just like the last job".

So when I stepped off the plane, I was immediately hit with "Where is xxx? And we're still missing yyy and zzz!" about three IPC pages' worth of hardware was nowhere in sight, because of configuration differences.

After ten days of followup from the logistics gurus, who had been gathering bits and pieces from three countries on two continents, the customer said I might as well go back home for two-three weeks while they worked on production schedule. I was left holding the bag; my only excuse was that I never should have taken the job under false pretense. :uhoh:

But when I finally returned, the job went smoothly, per plan!

[joy ride]

Lemain, post 1108, your comments about the need to make a whole section and cut a panel from it make sense to me. On reflection it seems odd to me that Boeing did not make a complete sacrificial shell, either now, or in the past as part of the development plan.
Airliners do get all sorts of knocks - just recently a BA 787 was slightly damaged by a set of flying steps borne by high winds which had been predicted at least 3 days earlier!
Perhaps Boeing did contemplate a donor hull but this was by-passed due to project delays.

[speedbump59]

If indeed the Seattle Times article is correct and Boeing will use a metalcentric type repair with a lap joint strip, then maybe there are a few more things to think about:

The patch will have a large pressure on it from the inside. Thus the joint between the patch and the 8 inch wide lap joint strip will be in tension (as well as shear). I think it is absolutely impossible that Boeing would trust a resin glued joint in tension. Thus I think the lapped joints must have rivets or the composite equivalent. This makes it even more of a metalcentric type repair.

If they use this method, I assume this means that the cut out and repaired area will not go across any barrel joins. In other words the whole repair area will be confined to within one barrel section. Also the Seattle Times article says they made a barrel section to cut the patch, not that they made two or three barrel sections for patches. But if this repair does have to go across a barrel join, it would add immensely to the complexity. Hard to believe that it would be possible. Anybody know the locations of the barrel joins with respect to the external damage that we could see in the photos?

Thus it seems that the size of the repair is relatively large (thus needing the specially made cut out patch) but limited in size to being within one barrel. Did the fire actually penetrate the barrel (make a hole in the fuselage?) Are there any better photos or newer information? I haven't seen anything that shows a hole, just heat damage (charring) on the outside.

If there is no significant hole, I am now surprised that they will cut out the fire damaged section. Why bother? Given that carbon fibre is pretty heat resistant, even the damaged section probably still has a fair amount of strength remaining. Just leave the damaged section in place. For the patch design, assume the damaged area has zero strength, but we get some extra strength benefit by knowing that it still has some.

Take your lovely patch, glue it on the inside of the barrel, bang in whatever rivets are needed, and put a bit of bondo on the outside of the airplane to smooth out the surface damage. Yes, some modest weight penalty to do this way (anyone have an idea what a 1 m x 2 m sized piece of the fuselage would weigh?). This method seems more secure than cutting away all the carbon fibre material that, although damaged by the fire, almost certainly still has some significant strength remaining.

Speedbump

[MrSnuggles]

To Speedbump:

Yes, I have been thinking along the same lines as you, that is what makes this such an interesting case.

I really would love to know how they decided upon this approach. I am especially curious about the "plug from outside" technology. There are many pros to have a plug inserted from inside - especially in an airplane.

Plug from inside would require a sharp angle scarf joint (or something with these pegs, nibs, hooks etc) though, otherwise the material might weaken in the edges, enough to MAYBE compromise the plug enough to make it fail catastrophically. A blunt angle scarf joint (which is, I believe, the case with this plane) could theoretically vibrate the glue enough over time to make it unstable.

Now they plugged it from outside. The theoretical case with the glue still stands but they removed the feature for the plug to "plug itself" into the hole. Speculating here, maybe that is to reduce compression stress on the glue. This would correlate well with the patch from inside that supposedly could reduce the effects of pressurisation (which would cause a tension stress on the glue), thus trying to keep glue properties stable. Just speculation from my side.

Thoughts on this?

[A and C]

You make the assumption that the plug would be fitted from the outside, there is no technical reason with a well executed scarf joint that this should be any weaker than the original structure.

There seems to be the assumption on these pages that a scarf joint is weaker than the original structure....... It is not weaker or stronger it is exactly the same.

My preferred option would have been to fit the new section as a plug from the inside as this would be less disruptive to the outside of the aircraft.

All this assumes than there is enough room to get the required surface area to perform a scarf joint.

[MrSnuggles]

A and C
My preferred option would have been to fit the new section as a plug from the inside as this would be less disruptive to the outside of the aircraft.

I would opt for this too.

That is why it is so interesting to know why Boeing do what they do. There must be a very well thought out reason for their repair technique - I would love to follow that reasoning!

[speedbump59]

A and C

Indeed perhaps it will be a combination:

1. A scarfed joint with the patch installed as a plug from the inside, and then
2. The 8 inch wide extra strips placed over the scarfed joint on the inside (glued and/or riveted in place to give extra support to the scarfed joint).

That might be a good combination.

However there might be a lot of interference from structure inside the plane (ribs, etc) to make this more challenging.

Speedbump

[MrSnuggles]

Re plugs:

It will cut the patch to the same size and shape and drop it into the space as a plug. The tiny gap around the patch will be filled with paintable sealant that will stretch and compress as the fuselage is pressurized and unpressurized.
Then mechanics will work on the inside, gluing a splice plate to the original skin and to the patch, overlapping both by about 4 inches.

I thought the above stated that they are plugging it from the outside. Did I misinterpret the description? "Drop it into the space" etc...

[speedbump59]

I thought the same. But calling the patch a "plug" kind of indicates that it will be installed from the inside to plug the hole (maybe scarfed).

Presumably the Seattle Times reporter is not an expert on composite repair and we should not read too much into the finer details of what he wrote.

And who knows how accurate his source is anyhow.

Speedbump

[gas path]

Try insert repair!http://images.ibsrv.net/ibsrv/res/src:www.pprune.org/get/images/smilies/nerd.gif

[andycba]

Looks like the tail has gone back on now.

https://twitter.com/Tartn52/status/404304481317163008/photo/1

[joy ride]

Thanks for the photo; I presume this indicates that the repair has been completed and re-assembly is now underway. I would still like to learn more about the actual repair but time will tell.

[gas path]

Nearly finishedhttp://images.ibsrv.net/ibsrv/res/src:www.pprune.org/get/images/smilies/thumbs.gif

[NWSRG]

Looking forward to hearing how this repair was finally carried out.

I've said it on here before, but I think this is a great story for Boeing and the 787...a fire that would have destroyed a metal frame, and yet this aircraft is being repaired, and will fly again. CFRP is the way ahead, and Boeing will have learnt even more in developing this fix. Well done to all...:D

[Lemain]

I've said it on here before, but I think this is a great story for Boeing and the 787...a fire that would have destroyed a metal frame, and yet this aircraft is being repaired, and will fly again. CFRP is the way ahead, and Boeing will have learnt even more in developing this fix. Well done to all...:DWould not a metal frame have dissipated more energy resulting in a lower temperature, when the ELT battery failed? Maybe there would have been no fire and no need for an extensive repair had the a/c been constructed in a conventional way?

[amicus]

Lemain.
Well said and I completely concur that it would have been a non-event or very minor repair for a metallic as the ELT battery is very small with little energy and I bet we never find out the repair cost either.

[A and C]

I don't think we have enough data to predict the damage that would have been done to a metal airframe and I would suggest that it would not be the ELT battery that would do the damage but rather the burning of what it sets fire to.

As to the time the repair has taken, it looks to me as if the legal wrangling and getting the logistics sorted has taken longer than fixing the aircraft. I think Boeing have done rather well, after all this is the first major field repair of a large composite airliner being done by a company that is not yet well versed in composite repair techniques and no doubt being hindered by those who know a lot about metal aircraft and very little about composites.

I would very much like to get a look at the repair to see what techniques were used.

[barit1]

Would not a metal frame have dissipated more energy resulting in a lower temperature, when the ELT battery failed?

Aluminum is one of the best thermal conductor materials, and often employed as a "heat sink" or thermal radiator for power semiconductors. For this reason I'd expect results as described above by Lemain.

Conversely, carbon composites are better thermal insulators, and contain the heat as seen in this 787.

[amicus]

A and C,
As the auto ignition temperature of the Toray 3900-2 epoxy as used on the 787 is a mere 580 degrees F per FAA tests and the autoignition temperature of aluminum alloys is around 2000 degrees F plus CFRP being and good insulator and aluminum an excellent conductor, I think that we can predict and state with full confidence that the damage of an ELT short and fire would be a whole lot less for metallics and we already have proof of small fires in 787 CFRP sitting at Heathrow.

[porterhouse]

I think that we can predict and state with full confidence that the damage of an ELT short and fire would be a whole lot less for metallics
Reading the DOT/FAA I am reaching an opposite conclusion, specially the executive summary of the results where a comparison to aluminium is made.

[WHBM]

As to the time the repair has taken, it looks to me as if the legal wrangling and getting the logistics sorted has taken longer than fixing the aircraft. I think Boeing have done rather well, after all this is the first major field repair of a large composite airliner being done by a company that is not yet well versed in composite repair techniques and no doubt being hindered by those who know a lot about metal aircraft and very little about composites.
I seem to remember that in all the earlier questioning of composite fuselages, it was always emphasised by Boeing that it was not an unknown, that they had done military aircraft fuselages like this, they therefore had all the experience necessary of field operations, they were the experts ..... yadda yadda yadda.

Which is correct ?

[MrSnuggles]

WHBM

Military chain of commands is so much shorter (ok, generally speaking...) so it's more "fix this YESTERDAY and that's an order!" (ok, overemphazising on purpose).

Civil aviation has all kinds of "red tape" running all across the world and with an Ethiopian plane on a UK tarmac with a US built airframe, insured by Someone and on top of that a major PR stunt for Boeing, of course it takes time no matter how well prepared the engineers might be.

Once the work started it seems they did pretty well - remember we don't know how extensive it was on the inside. I do believe that composite materials are pretty well understood IF Boeing chooses to use the military knowledge people in the civilian process. I am not at all familiar with Boeing's corporate structure but there are occasions where military and civilian engineers are completely separate within the same company (you know, secret stuff, classified stuff, not allowed to share because of the safety of the nation etc), leading to peculiar gaps in information exchange. This will of course hamper the development of products, mainly on the civilian side because that side is the one that really has to consider price tags.

Now, as for how they actually fixed it, I am a curious beast. Any gossip, loose rumours, uneducated guesses, anything besides the post in Seattle Times? ;-D

[joy ride]

Is the repair work complete now? I too am fascinated by all the discussion here but would love to know some solid facts about the damage done and the repair itself; wishful thinking perhaps!

[porterhouse]

and the repair itself; wishful thinking perhaps!
Yes!, wishful thinking...
Aviation Week And Space Technology had recently (just about 2 weeks ago) an article on the subject, they said that repair method was 'confidential', and if this very influential and otherwise extremely well informed weekly doesn't know there is a fat chance someone on this forum will ...

[cockney steve]

if this very influential and otherwise extremely well informed weekly doesn't know there is a fat chance someone on this forum will ...
So you think it's highly unlikely that a PPrUner has worked on it , then?
You think it's highly unlikely that a PPruner will know somebody who worked on the repair and wheedle some info?

IT ISN'T A STATE SECRET....Maybe a confidential industrial one, but as with virtually all industrial secrets, it will eventually out.
Also, some of those involved are likely to set up their own Composite repair business in this niche market where they'd be able to virtually name their own price.
let's sit and wait....who knows, Boeing may, just may want to trumpet their success!

[olasek]

You think it's highly unlikely that a PPruner will know somebody who worked on the repair and wheedle some info?
I personally think that it is very unlikely that a PPruner would tell us something that simultaneously 1. would be 100% accurate and 2. not available at the same time from other sources.

[kingstonboy]

and 3. extremely career limiting !!!!
quick RDC inspection and QCR and on to main base !!!!!
and yes i am jesting .

[Bigt]

Flight International saying the aircraft will fly around 22 December and was repaired using ` a composite section bolted to the airframe`. This information coming from the CE of the operator....

[MrSnuggles]

I really hope "bolted" can mean something like "carefully glued together" or I will really question the validity of that source... LOL!

It would be a sad sad moment if composites were "bolted" in the meaning I am used to hear the word... again, the reservation for being non-native English speaker.

But a nice piece of gossip, I acknowledge that!

[peterhr]

It will be very interesting to see where it flies to, whether it be a Boeing plant to have a 'temporary fix made good' or it would be back into service...

[Helix Von Smelix]

ET-AOP off to Manston. Departed LHR 10:35 ish

[TopBunk]

May well be headed to Manston, but it left LHR went up over East Anglia, headed north up the morth sea climbing to FL390 before turning south - presumably to Manston.

[joy ride]

I had a feeling it would be off today, before the stated date! Are there service/inspection facilities at Manston to see how all is shaping up before returning home?

[Helix Von Smelix]

Once arrived at Manston, expected to leave again at 14-15:00.

Has the cabin interior been fixed? Would expect that to be done somewhere other that LHR, Cardiff ?

[joy ride]

On FR24 as BOE787, currently heading NW

[superq7]

Looks like a test flight ?

[phiggsbroadband]

It looks like it is doing some manoeuvres over the North Sea at FL150...


BOE787 live flight tracking - Plane Finder (http://planefinder.net/flight/BOE787)

[joy ride]

That would be my guess! Circling at various altitudes to keep an eye on pressure and electrical functions, then perhaps re-fuelling at Manston, then possibly home or to Boeing. Ethiopean will be VERY pleased to get it back into service and return the leased "wrong airport" 767!

[phiggsbroadband]

Also notice that they are squalking 6060, which is a Malmo code... but could be pronounced 'Sick Oh Sick Oh'.


Looks like they have just done a minimum radius turn at constant height...
Can't wait to see if Wing-Overs and Hammer-Heads are in their repertoire...

[joy ride]

Seems to be heading to Manston now. Is it my imagination or does their flight path from top left to bottom right read "AOK" ?!

[MrSnuggles]

Anyone seeing what they are doing now over Norwich? It seems they are hovering at altitude... strange...

[joy ride]

Missed that, but now appears to be heading back to Heathrow. Just flew over, too much Yuletide murkiness to see it, but heard it, making an unusual blaring sound, odd.

[MrSnuggles]

I'd love for someone to meet it at gateway (or whatever) with a camera to take pics of the repair!

[phiggsbroadband]

Well after two holds at 8000ft it landed back Ok at Heathrow at 14:38.
The following IB A320 landed 5 minutes later, having allowed some time for the runway inspection perhaps.


So it wasn't Manston... most likely the pilots wanted to return to their cars after a successful flight.

[joy ride]

Perhaps they have to sign off the repair work as acceptable.

[Lemain]

Due diligence would surely require that the whole area of the repair is instrumented with strain gauges to check for load, stress and vibration over a range of flight configurations, speeds, altitudes,.....and then analysed in the lab with design engineering scrutiny leading to certification. Could be flown back stateside under a special cat CofA, tho'.

[gas path]

If the test flight was successful I think the plan was to go into revenue service.:8

[Lemain]

If the test flight was successful I think the plan was to go into revenue service.http://images.ibsrv.net/ibsrv/res/src:www.pprune.org/get/images/smilies/nerd.gifLeaving my derrière in Blighty.

[porterhouse]

I really hope "bolted" can mean something like "carefully glued together" or I will really question the validity of that source...Both glued and bolted.

Has the cabin interior been fixed?Yes, the plan was to completely replace it due to smoke damage.

[LH2000]

Its back in operation, been flying since the 23rd.
It ferried to Frankfurt and did ET707. Been flying pretty much every day since.

So i would consider Boeing's repair as the permanent repair.

Pretty impressive

[peterhr]

It appears that it's back in service Flightradar24.com - Live flight tracker! (http://www.flightradar24.com/reg/etaop)

[MrSnuggles]

Some keen plane spotter who can take pictures of our flying friend? I would LOOVE to see a close up on the repaired part.

[phiggsbroadband]

Quote... I would LOOVE to see a close up on the repaired part.


My bet is that it will not be painted blue, with yellow dots around the outside edge of it...

[LH2000]

Have a look in Airliners.net photo Id 2362630, it's taken after the tail was put back on. Looks like a nice flush repair. No obvious bumps from this distance. I have seen another photo with all the scaffolding taken away, but not as high res but the repair is all but invisible.

[kiiyt]

Page 59, whew! So much content!

Some weeks ago following the fin removal, I visited the aircraft and iscussed the repair with the on-site Boeing project manager. Though he was officially unable to disclose any details about the repair, he did not deny that the repair would take the form of a splice repair, and that it would be full, permanent repair, with the aircraft re-entering commercial service upon completion.

Though the fin was removed to improve aircraft stability, I have never seen such a heavily trestled aircraft in my whole career. When Boeing carry out an AOG repair it is nothing but impressive; a tented facility/factory manned by 60 Engineers & Composite Specialists, with the aircraft shrouded in an environmentally controlled enclosure. Good stuff!

Though details were not forthcoming, I got the impression that the damaged area would be removed, and replaced with an identical piece cut from an existing (or purposely made) aft fuselage section and spliced together. Note: Being a 'plastic' aircraft does mean it is necessarily 'glued together', and as such does not exclude the use of near conventional fasteners.

With regard to the LHR-LHR test flight on the 23rd, this is nothing unusual, especially given the circumstances and depth of work carried out.

Commenting on the earlier 'metal vs plastic' arguements; had this been a metal aircraft it would have been repaired months ago, using conventional methods.

It might also be worth dwelling on the fact that to achieve certification from the regulatory authorities prior to EIS, Boeing would have been required have in place a working Structural Repair Manaul (or equivalent) and been able demonstrate a AOG Repair Scheme support program.

Good to see it flying again, and the speculation put to bed!

[guided]

AAIB posted a Special bulletin

http://www.aaib.gov.uk/cms_resources.cfm?file=/S4-2014%20ET-AOP.pdf

It's quite damning to Honeywell - 6 months before they identified an issue in manufacturing the ELTs and changed the process, but haven't recalled the existing ones. As a result there were 28 ELTs (out of 3600) with crossed wires ready to start a fire in an inaccessible area in an airplane

[amicus]

For all those interested, the AAIB published the final report regarding this incident on August 19th and it can be downloaded from aaib.gov.uk or you can PM me and I will forward it to you. It is 182 pages and is, I note, replete with detailed photographs of both the interior and exterior extensive structural damage and it had approximately 11 square yards of major fuselage crown damage and now the FAA , as a result of this AAIB report, is finally "reviewing their certification procedures and flammability testing for composite aircraft flammability" with obvious potential huge implications for both Boeing and Airbus.