Ethiopean 787 fire at Heathrow

[Speed of Sound]

It looks that there are two generations of this ELT classic AFN and new (half sized) AFN2:

More than half sized!

Less than half the weight and less than half the batteries needed to power it.

So both units have a 50 hour operating time and a ten year battery life and yet both generate the same 150mW/5W RF output. If the new unit (the 406AFN2) is doing this using only two cells instead of five, then either the circuit losses in the new ELT are more than halved or the battery chemistry in the AFN2 is producing more than twice as much power!

Do we know that the new unit is also using Lithium-Manganese chemistry or are we just assuming it?

Could this fire have been caused by a trapped wire AND a damaged battery with a much higher energy density than its predecessor? We keep hearing that 6000 of these units have been used without incident but how many of the Mark 2 version are in service?

This may not be solely a 787 thing, it may be a problem with the new version of the beacon. :eek:

[Mr @ Spotty M]

Where do you get your info that all European operators have removed their ELTs?

[fenland787]

We keep hearing that 6000 of these units have been used without incident but how many of the Mark 2 version are in service?
A really good question! I would hope that the 6000 figure Honeywell claimed when this started relates to 6000 of the same model as is fitted to the 787, it would be very far from honest of Honeywell to have claimed that if, for example there are 5900 Mk1 and 100 MkII in use and those are all shipped to 787s!

[Finn47]

The AAIB Special Bulletin specifically identifies the ELT in question as the RESCU406 AFN (see Safety Recommendation). If the model would be AFN2, don´t you think the AAIB would have said so?

Air Accidents Investigation: Download PDF document (http://www.aaib.gov.uk/cms_resources/S5-2013%20ET-AOP.pdf)

[Eclectic]

@ Mr @ Spotty M

Click the link I provided.

[John Marsh]

Question from non-engineer SLF:

What would it cost to design in a supply-rail fuse for the ELT battery? Or failing that, a length of fusible PCB track.

With the glorious benefit of hindsight, a pinched wire seems a rather simple and thus probable error.

[fenland787]

What would it cost to design in a supply-rail fuse for the ELT battery? Or failing that, a length of fusible PCB track.Initially - practically nothing, retrospectively - quite a lot! (re-design, re-qualification, recall.....)

However, as I said in earlier posts Honeywell have been at this game a very long time, I really can't believe they didn't think of that and the need to protect the cells from shorts 'upstream' of the PCB(s), so the question we are left with is:

What failure mode did the box and it's installation manage to come up with that meant it didn't work?

[Speed of Sound]

I wondered the same, so last week I contacted Honeywell on exactly that point. Honeywell confirmed it was AFN2.

Very interesting!

I can see the AAIB possibly just referring the unit as its base model name RESCU406AFN but it also refers to it containing a 'set' of batteries rather than a 'pair' and makes reference to '6000 units' which clearly must be the original model.

The first safety recommendation (2013-16) refers specifically to the RESCU406AFN model but the second recommendation (2013-17) refers to "installations of
Lithium-powered Emergency Locator Transmitter systems" which I assume means both mark 1 and mark 2.

http://i1280.photobucket.com/albums/a481/SoS57/RESCU604AFN_zpsbc2f73fc.jpg (http://s1280.photobucket.com/user/SoS57/media/RESCU604AFN_zpsbc2f73fc.jpg.html)

For some reason the mark 2 model has the wording RESCU406AFN on the case, which may be the cause of the confusion.

Very strange! :sad:

[theroadie]

The pinched wires, I would suppose, are on the wiring between the battery and the connector to the PCB, which could be subject to being moved and not fixed in location and routing. More like the design of a portable phone battery than a cell phone. Only fuses right at the place where the wiring enters the battery, or inside the battery casing, would be total protection.

However, they add another layer of risk in the failure flowchart, and engineers could have decided the cost outweighed the benefit.

Of course, this is all guessing, that could be halted by one decent picture of an open unit.

[Eclectic]

I don't know if it is any help, but here is the company product brochure for the Honeywell RESCU406AFN2

http://www51.honeywell.com/aero/common/documents/myaerospacecatalog-documents/ATR_Brochures-documents/NEW_RESCU_406_AFN2.pdf

[fenland787]

However, they add another layer of risk in the failure flowchart,

Very true and the FIT number for thermal fuses is horrid but given the aviation world's dislike of battery powered equipment and their potential failure modes, I would have hoped the fuse would have won out. Especially as there was, by the look of it, scope for a good margin between fault and operating current?

[RetiredF4]

Electic
I don't know if it is any help, but here is the company product brochure for the Honeywell RESCU406AFN2

http://www51.honeywell.com/aero/comm...U_406_AFN2.pdf

Meanwhile everybody should be aware, as it was already posted in post 581,

post 581 (http://www.pprune.org/7950305-post581.html)

Karel_x posted it in post 769,
Post 769 (http://www.pprune.org/7963399-post769.html)

What has not been discussed is, how they could save over 50% of weight by maintaining the same power output. Could this weight saving be on behalf of less built in safety, insulation and more risk when using 2 cells instead of 6 cells?

[archae86]

Bloomberg is posting a story (http://www.bloomberg.com/news/2013-07-29/boeing-urges-beacon-inspections-on-some-planes-other-than-787s.html) stating that Boeing "asked specific operators of 717, next-generation 737, 747-400, 767 and 777 airplanes to also inspect aircraft with fixed emergency locator transmitters, or ELTs, from Honeywell". This is described as pursuant to an AAIB recommendation.

The Bloomberg story is directly sourced to Randy Tinseth's (Boeing marketing VP) blog, which you can find easily enough, but which when updated will no longer carry this entry at the top.

[Karel_x]

how they could save over 50% of weight by maintaining the same power output

Except it, that new battery could have greater capacity, I can imagine one more way. I suppose that in standby mode the consumption of ELT is very low, lower then 1 mW and battery life is limiting by its self discharging process. In case of emergency, I suppose that the transmission of data is not continuous, that between data blocks could be time breaks, eg. 5s "telegrams" in 30s interval. If you have not energy enough, you can make intervals longer. My speculation.

[ironbutt57]

And of all the airplanes it decides to catch on fire on:uhoh:

[Speed of Sound]

What has not been discussed is, how they could save over 50% of weight by maintaining the same power output.

I did, only 13 posts ago! :ok:

http://www.pprune.org/rumours-news/518971-ethiopean-787-fire-heathrow-39.html#post7964412

[mm43]

@ SoS

Following from Honeywell -Specifications (RESCU 406 AFN2)
MTBF 100,000 hours (estimated)
Certifications Approved by Boeing, Airbus, Dassault, FAA
RF Power 100 mW 121.5 MHz, 5 watts (406 MHz)
Battery Service Life 12 Years
Compatibility Backwards compatible with RESCU 406 AFNNote the 12 year battery life.

I believe there are 2 packs comprising 4 cells in each and most likely of the Li-MnO2 type.

[mangere1957]

Can anybody tell me the cost per life saved by fixed ELTs in heavy transport aircraft? My strong suspicion is that not a SINGLE life has been saved and the cumulative cost over the last thirty years probably in the hundreds of millions of dollars. As well as the cost, the PROVEN increase in risk must be taken into account.

Just because a thing CAN be done doesn't mean that it is sensible that it should be done*.

In my view fixed ELTs MIGHT be justifiable in aircraft up to light twins but that is all.

*In the mid seventies the head of training, on F27, of a national carrier, carried out a GA from 1500 ft on final on glide path below all cloud, with gear down and locked**, after there was an explosion in one wheel well. He could do it, but should he have? Nah.

** There were still three greens after the explosion. That's all one needs to land an F27 on 10000'.

[Speed of Sound]

Thanks for that.

There seems to be a number of data sheets around giving different information.

I'm still struggling to understand how a greatly reduced number of cells can provide the same amount of power or even more, using the same Li-MnO2 chemistry. :confused::confused:

[fenland787]

I'm still struggling to understand how a greatly reduced number of cells can provide the same amount of power or even more, using the same Li-MnO2 chemistryBigger capacity cells, combined with more modern electronics that run at a lower voltage = lower cell count?

As others have said too, we don't know how long the transmissions have to last when used in anger perhaps the MKI battery was over specified in that respect?

[Mr @ Spotty M]

The 12 year life for the battery is the same for the portable RESCU 406 ELT that Honeywell makes, which is also fitted to some B787 aircraft.
My guess would be the same type of battery, but l am not in a position to check at this time.
The batteries are replaced however at 10 years as per the MPD for the fixed ELT.
It is the same interval also for the portable ELT, which aligns with the second 5 year off wing inspections.

[LeadSled]

Can anybody tell me the cost per life saved by fixed ELTs in heavy transport aircraft? My strong suspicion is that not a SINGLE life has been saved and the cumulative cost over the last thirty years probably in the hundreds of millions of dollars. As well as the cost, the PROVEN increase in risk must be taken into account.

Just because a thing CAN be done doesn't mean that it is sensible that it should be done*.

In my view fixed ELTs MIGHT be justifiable in aircraft up to light twins but that is all.

Mangere1957,
As you suppose, the answer is NIL!
See my posts a few pages back, the in-service failure rate in accidents for fixed ELT is better (or worse)than 95%, or 100% in water.
They are simply not justified on any aircraft. The Australian research and results on the subject is very clear.
Fixed ELT are an utter waste of money, without regard to any additional risks they may introduce.
What other piece of equipment with a 95%+ failure rate is tolerated on an aircraft??
Tootle pip!!

[WHBM]

787 Chief Project Engineer at Boeing, Mike Sinnett, sidelined :

Boeing changes chief 787 engineer in management shuffle | Reuters (http://www.reuters.com/article/2013/07/26/us-boeing-changes-idUSBRE96P14M20130726)

[Speed of Sound]

Bigger capacity cells,

That 's what I am getting at.

If the same, or greater power can be derived from a 60% smaller volume of cells, then the energy density of those cells must be more than double.

Energy efficiency savings gained by better circuit design would be somewhere around 5-10%, and only then if the mark one electronics were very inefficient to start with.

[noughtsnones]

A further thought on battery size and life...
The monthly system self-test described in the data sheet is declared as having a total duration of 5 seconds (unchanged between unit types), elsewhere the data sheet states "Enhanced ... and self test".
There is a merit in keeping the outside observable maintenance procedures unchanged, to eliminate possible adverse risks of forward and backwards compatibility.
A reduced battery size can be speculated, based upon a system self-test using less power per usage (month), by enhancement to the test sequences and better test result data integration.

[fenland787]

If the same, or greater power can be derived from a 60% smaller volume of cells, then the energy density of those cells must be more than double.Agreed, do we know the cell volume is decreased by 60% or just the housing/battery pack? Not disputing, just asking! :)

[joy ride]

On the BBC Business news:

BBC News - Boeing requests worldwide inspection of aircraft (http://www.bbc.co.uk/news/business-23486472)

[Ian W]

In the Bloomberg report Boeing changes chief 787 engineer in management shuffle | Reuters (http://www.reuters.com/article/2013/07/26/us-boeing-changes-idUSBRE96P14M20130726)


is the following throwaway line...

Investigators traced that incident to pinched wires in an emergency beacon and regulators instructed airlines to inspect or replace the units. Since then, other reports of fires have surfaced.

Obviously, a fire in another aircraft type would be of zero interest to the baying peanut gallery - but when it happened in a 787 it is suddenly worldwide news. So the various regulatory bodies only took action after the media interest?

[Speed of Sound]

Agreed, do we know the cell volume is decreased by 60% or just the housing/battery pack? Not disputing, just asking!

I am basing this on a low-res pic of a section through both a AFN and an AFN2 which showed 5 batteries in the former and 2 batteries in the latter. They looked identical in shape and size and only the amount installed differed.

I wish I could find the damn jpeg as a few people have asked what the inside of the beacon looks like! :ugh:

[Mr @ Spotty M]

Don't believe all that you read from the unreliable press. :=
Not all EASA supervised airlines operating the B787 have removed the fixed ELT, l know of one that is inspecting the wiring around the ELT and the outer case for signs of overheating, on a daily basis. :ok:

[fenland787]

, l know of one that is inspecting the wiring around the ELT and the outer case for signs of overheating, on a daily basis. Well that's reassuring - has anyone told them just how quick these things can go up if they decide they are going to? :eek:

[mangere1957]

LeadSled @ #796

Thanks for that(to others; confirming my conjecture that ELTs are useless).

Because ELTs have never saved, and will never save, a single life in heavy transport operations, but cost a lot and introduce risk they should be removed at once.

Prognosis: This will not happen. Regulatory authorities(and manufacturers) will never admit that they stuffed up mightily(just imagine AI admitting that having un-moving thrust levers was a bad idea).

All discussion of battery size, capacity, etc is irrelevant. ELTs must be removed.

[fenland787]

All discussion of battery size, capacity, etc is irrelevant.Only irrelevant if your prognosis is incorrect surely? If your prognosis is correct these things need to be made safe. So the failure mode needs to be first understood, then fixed.

[Fly380]

Well the ELT didn't help with finding the Kenyan Airways 737-800 at Douala a few years ago. They were looking miles away when all the time it was in a swamp at the end of the runway.:rolleyes:

[Ian W]

Fixed ELT's have a one hundred percent failure rate.:hmm:

[Yankee Whisky]

Tell that to all the crew and aircraft found and saved (in some cases) in Canada's North, and elsewhere in NA ! If it had not been for the ELT signal being received for direction to its location, we'd still be looking for an appreciable amount of crashes with the loss of more life.
Signals now include GPS co-ordinates and that speeds up a search.
Unfortunately there are too many misuses of the ELT's causing false alarms and, possibly, delayed reactions. :=

It seems that some readers and writers on this forum never had their asses over unlandable terrain for a long time !!!

[olasek]

I don't think anybody doubts the value of ELT in General Aviation (specially for VFR flights) but I think they are much less useful for larger air transport aircraft whence for example FAA in the US doesn't mandate them for airliners.

[Kerosene Kraut]

Do you remember how difficult it was to track AF447?

[ExSimGuy]

Do you remember how difficult it was to track AF447?

Possibly for the same reason that submarines come to the surface to use their radios, rather than transmitting from 12,000 feet down? :ugh:

[Kerosene Kraut]

This is why I would prefer to maybe add even more buoy ELTs/PLBs/EPIRPs and whatnot instead of completely removing them.

[NWA SLF]

It's the old news axiom dog bites man is not news, man bites dog is news. Frequently hear of various airliners making unscheduled/emergency landing due to cockpit smoke, but they are back page slow news day fillers. Smoke in a 787 overwhelms even the birth of Prince George (naw, even here in a colony fighting to rid themselves of control by another George it overrode everything). But now I read, "Oh, yeah, there have been other ELT fires." To be honest the current alert to travelers resulting from intelligence sources that a terrorist attack planned very soon overrides thoughts of there maybe being an in flight 787 fire or an uncontained A-380 engine explosion that damages much of a wing structure. Scarier yet is seeing the evac photos of people carrying their luggage away from the emergency escape slides. Those are all people who could have blocked my exit and killed me as sure as if they shot me.

[DWS]

or in other terms- the fail safe may not have been a fail safe ??

Still seeking cause of 787 fire in U.K. | Business & Technology | The Seattle Times (http://seattletimes.com/html/businesstechnology/2021528093_honeywelleltxml.html)

Still seeking cause of 787 fire in U.K.
As Canada’s Transport Ministry examines Honeywell’s emergency beacons, the company confirms the devices should have been able to prevent overheating in case of a short circuit.

By Dominic Gates
Seattle Times aerospace reporter
:confused:
The small off-the-shelf electronic device at the center of the investigation of a fire aboard a Boeing 787 Dreamliner at Heathrow airport last month contains a fail-safe mechanism that should have prevented overheating even in the event of a wiring short-circuit, a Honeywell spokesman confirmed Friday.

The Emergency Locator Transmitter (ELT), supplied to Boeing by Honeywell and used in many other aircraft besides the 787, contains a current limiter — a standard feature, like a fuse, that shuts off the current if it gets above a certain level.

Boeing and government investigators inspecting the damaged ELT from the Ethiopian Airlines jet found that internal wires connected to the device’s lithium battery had been trapped and pinched when the cover was reattached as the batteries were inserted.

That led to a theory that the pinching of the wires compromised the insulation, and that crossed wires short-circuited to start the fire.

Honeywell spokesman Steve Brecken said Friday that the ELT contained a current limiter that should have stopped any surge of current caused by a short.

Did the limiter somehow fail? Or was the fire started some other way?

Brecken said all that’s known is that the fire was “in the area” of the ELT and that the investigation led by the U.K’s Air Accidents Investigation Branch is continuing. “We don’t know that the current limiter failed,” he said.

The Wall Street Journal reported Friday that Transport Canada, the aviation regulator in Canada, is preparing to order the inspection of ELTs in all types of planes carrying the device, including Airbus and Dassault.

Last week, Boeing sent out a service bulletin to operators of all its planes — not only the Dreamliner — recommending inspections of the ELTs.

The ELT is manufactured and assembled by a Honeywell subcontractor, Instrumar, of St. John’s, Newfoundland. Instrumar’s main business is technology connected with the production of carpet fiber, and the ELT appears to be its only aerospace product.

Brecken said Instrumar ships the ELTs for the 787 to Honeywell’s Deer Valley facility, near Phoenix, Ariz., and from there they are sent to Boeing.

He said Instrumar ships ELTs for other aircraft and for other manufacturers to Honeywell’s Mississauga facility, outside Toronto.

The Journal said Transport Canada this week inspected the Mississauga facility and will inspect Instrumar’s plant next week.

[olasek]

.That led to a theory that the pinching of the wires compromised the insulation, and that crossed wires short-circuited to start the fire.
I imagine it should not be tough to test this theory, they don't need the whole 787 for that, just a small section of a fuselage with all the relevant tubing/insulation/electrics, etc.

[fenland787]

I imagine it should not be tough to test this theory, they don't need the whole 787 for that, just a small section of a fuselage with all the relevant tubing/insulation/electrics, etc. Not even that, all that is needed initially is an ELT, or perhaps even just some of the battery packs.

I'm not sure what the 'Current limiter' is, but that is not a description I would use for a 'conventional' fuse so I suspect it is a self-resetting fuse of some sort. These work by increasing their resistance with temperature and that increase in temperature is caused by resistive losses due to the current flow through the device then, as the resistance increases, the current drops or limits.

If the sizing of that device is wrong for the equipment, or the device was faulty, and it is in thermal contact with the battery I could imagine a scenario where it is possible to get a combination of over-current and temperature where the device is cycling 'on and off' (I know it's not quite on and off but you get the idea) and the combination of a hot day, hot limiting device and self-heating in the battery due to the fault current could be, over time, that the Li battery is heated to the point of thermal runaway.

How's that for speculation from someone who doesn't speculate?

[ZFT]

It can’t be coincidental the Honeywell are one of the worst OEMs to deal with in just about every aspect and every division.

Whether it’s APUs, Avionics, spares, repairs, rip off pricing policies, general support issues such as updating EGPWS, there are a myriad of issues. These issues are spread across the complete aviation community too. Absolutely nothing to do with Boeing.

These aren’t new issues and maybe, just maybe they are indicative of cultural issues within a corporation that has lost its way?

[EEngr]

The Emergency Locator Transmitter (ELT), supplied to Boeing by Honeywell and used in many other aircraft besides the 787, contains a current limiter — a standard feature, like a fuse, that shuts off the current if it gets above a certain level.Where is the current limiter located? On the ELT circuit board? That would be too far along the current path to be of any use in the case of a pinched battery wire. The current limiter would have to be in the battery pack itself.

Which raises another interesting issue: If the original Honeywell batteries were replaced (and they incorporated said limiter), were they replaced with OEM batteries? Or is there a generic 'equivalent' that may have been substituted?

[olasek]

Not even that, all that is needed initially is an ELTOnly initially perhaps, but at some point they better get more aircraft structure to replicate the overall damage, fire propagation, etc.

[fenland787]

There is no way anything other than a Honeywell part could be used and maintain certification I would hope?

As you point out, the polyfuse (or whatever) must be part of the battery pack to be any use, hence my thought about it being in close thermal contact with the cells - perhaps deliberately in the hope that it would shut things down if the cells got to hot? Wouldn't be any use in a thermal runaway situation though.

[fenland787]

at some point they better get more aircraft structure to replicate the overall damage, fire propagation, etc.True, but that could apply to almost any part of the airplane, regardless of what started it? I would have hoped that kind of thing was done already, though someone may be wanting to revisit their ideas in the light of what they've seen in this incident!

Hmmmm....Sorry "in the light of" might be an unfortunate phrase to use in the circumstances......

[Jetstream67]

I cannot speak for the particular cell pack in the ELT but having dismantled and rebuilt quite a number used outside aviation it is standard to include a fuse or a polyfuse (effectively a self resetting fuse) in a pack. These often turn up as links between the actual cells of multi cell batteries but on single cell designs they are at the cell ends of the leads or on an attached protection circuit board.

Whoever did that design would have been expected to test their design (i.e. apply both increasing and random levels of excess discharge current and finally an immediate short circuit across the battery terminals or wires) to ensure the battery shut down and stayed shut down safely in each case.

From the reports the two leads were shorted together which should have resulted in a very short pulse of current then a drop to a hugely limited current for the duration of the fault thanks to the action of the polyfuse. If the polyfuse failed to work or failed to reduce the fault current enough for safety the cells would then be able to potentially overheat over time running the risk of Cell thermal runaway. If the short circuit was intermittent this might have been the subject of many repeated cycles of short, shutdown and recovery and perhaps this is where the issue arose

Once the cells reach a critical internal temperature (c 135c IIRC) they proceed to break down and self ignite and no fuse is going to help them after that point

[olasek]

. I would have hoped that kind of thing was done already, though someone may be wanting to revisit their ideas in the light of what they've seen in this incident!
Was done what?
I doubt recreation of chain of events had been done in this case, it takes time to set it up, it is much more expensive proposition than fiddling with just ELT in the lab environment. It may not be as hard as NTSB's multiple attempts to reproduce sparks in the 747 main fuel tank but it may be difficult and time consuming nevertheless.

[EEngr]

There is no way anything other than a Honeywell part could be used and maintain certification I would hope?I think more than hope should be involved in a QA program. On the other hand, this battery replacement isn't something Boeing usually deals with and planned for. It was forced on them by the program slide.

[Interested Passenger]

Once the cells reach a critical internal temperature (c 135c IIRC) they proceed to break down and self ignite and no fuse is going to help them after that pointpolyfuses trip at 125'c either from external heating or internal heating and will stay at that temp while there is a fault. Hope the protection device didn't overheat thebattery it was supposed to protect.

[Peter H]

Jetstream67 (http://www.pprune.org/members/302385-jetstream67)
I cannot speak for the particular cell pack in the ELT but having dismantled and rebuilt quite a number used outside aviation it is
standard to include a fuse or a polyfuse (effectively a self resetting fuse) in a pack. These often turn up as links between the actual
cells of multi cell batteries but on single cell designs they are at the cell ends of the leads or on an attached protection circuit board.

Whoever did that design would have been expected to test their design (i.e. apply both increasing and random levels of excess
discharge current and finally an immediate short circuit across the battery terminals or wires) to ensure the battery shut down
and stayed shut down safely in each case.

I assume that a polyfuse would effectively restrict the current during the "short circuit" to that necessary to keep it at ~125C.

If so, the heat-flow from the polyfuse might become significant. Two extreme examples are:
1) If thermally clamped to the battery, the polyfuse would presumably heat the battery to ~125C at the point of thermal contact.
2) If thermally clamped to the ELT case (via the shorting wire), the polyfuse might need to pass a significant current to maintain
its ~125C temperature.

I assume that (1) is designed out, as it's effects would occur in all short-circuit testing situations. However (2) would only arise if
the short-circuit event also provided a "new" thermal pathway, so might not appear in "normal" testing.

Do you have any thoughts on the polyfuse's likely degree of thermal isolation in this incident; both from the battery and from the ELT case?

[grumpyoldgeek]

Electrical engineer and PP here. I looked at Polyfuses in a design I was working on about a year ago. After playing around with them and a bench power supply, I decided that they could not be trusted for my application. Went with a time-tested fuse. Looks like it was a good idea.

[Volume]

I imagine it should not be tough to test this theory, they don't need the whole 787 for that, just a small section of a fuselage with all the relevant tubing/insulation/electrics, etc. Well, I remember many fellow ppruners accusing Boeing and its subcontractors to simplify many of their tests too much, missing to simulate real in-service conditions...

[olasek]

Well, I remember many fellow ppruners accusing Boeing and its subcontractors to simplify many of their tests too much, missing to simulate real in-service conditions...Yeah, rather completely different subject.
Boeing (like any other aircraft manufacturer) did exactly what tests were required for the certification of their 787, if you try to blame someone for "simplifying tests" blame FAA. Certainly such tests do not require it simulate ELT fires. But if British (or any other) aviation agency wants to be satisfied as to completeness of this ELT accident investigation they could attempt to do full scale tests which would include portions of the fuselage.

[Jetstream67]

Polyfuses 'blow' in a fairly traditional manner and the fault current falls back to a very low level - basically enough to confirm the fault remains.. After all fault current ceases they fully recover over a number of hours to being fully conductive again. So no they do not sit at 125c in an overload state as a protective resistor might.

The issues are :
* they do not cut off all current entirely
* Their correct operation under all cyclic short and recovery conditions is not generally specified (i.e they are seen as an occasional safety precaution not 100 cycles a day etc.) although it might have been tested in this scenario

But unlike traditional fused they are less sensitive to impact forces while in operation (pretty important in an ELT) and they can recover to allow normal operation after a temporary short circuit is removed. For an ELT the latter two factors might be considered valuable

[DWS]

Microsoft Word - SAFITA_for_Website - SAFITA_2013.pdf


http://aerosociety.com/Assets/Docs/Events/SAFITA_2013.pdf

[TomOfCT]

This has really gone quiet. Any further developments/rumours swirling?

[RCav8or]

http://www.pprune.org/7994995-post124.html

[amicus]

Regarding the Ethiopian fire of ELT battery, I have already cited my opinion that the CFRP as an insulator rather than aluminum as a thermal conductor mightily contributed to this fiasco and rendered what might have proved to be a minor incident in metallics into a major and ongoing issue re 787.
First, I am a mechanical engineer specializing in composites for a mere 48 years in aviation and am not a thermodynamicist, albeit I know enough thermodynamics to pinpoint this issue, I believe.
Let me give this thread some thermal conductivity values for various materials and then conclude with the dire effects regarding low thermal conductivity rewiring shorts, arcs and the like.
Some typical thermal conductivity values for metallics are: (all units are in the widely accepted and used W/m/K):

Aluminum and its various alloys = 167
Brass = 116
Copper = 339
Steel = 48


And for CFRP it is 0.13, HA!

Thus, when any short or arc occurs close to CFRP, the skin temperature always peaks higher than the highly conductive aluminum alloys, thereby exacerbating any or all fires besides which, incurring permanent structural damage starting at around 375 degrees F and being flammable with a very low self ignition temperature of 580 degrees F.
Hence, fire damage will always be far worse in CFRP with irreversible structural damage vis-a-vis metallics. This plight, of course, also incurs the rightly dreaded FST products of combustion.
This is the case for any or all electrical shorts, arcs, or any other fire sources not merely ELT's. Hence, any fire adjacent to fuselage skin or wing skin will always be far worse for CFRP versus metallics.
Now, was this accounted for in any FAA Special conditions, was it tested for extensively during certification, and finally has Boeing properly assessed all very low thermal conductivity risks due to shorts,chafing, aging, arcs of all electrical wiring, batteries, et al ?
I do not believe such to be the case and now we have a forlorn, and possibly terminally damaged Ethiopian 787, based upon actual repair costs . This aircraft is still sitting in a remote LHR hanger while Boeing and the insurance underwriters presumably debate its final fate. And what might have been merely a minor ELT shorting incident on a metallic aircraft is looking like a total hull loss or a huge and very difficult repair face-saving exercise.
And this present exercise will be replicated many more times for the 787, particularly as electrics age even assuming that they are correctly wired in the first place, I venture to predict. Some airlines and MRO's might care to ponder this note.

[fantom]

Holey moley.

I am an A-team person of many years standing but I would not wish that on the B team.

Sorry.

[lomapaseo]

Thus, when any short or arc occurs close to CFRP, the skin temperature always peaks higher than the highly conductive aluminum alloys, thereby exacerbating any or all fires besides which, incurring permanent structural damage starting at around 375 degrees F and being flammable with a very low self ignition temperature of 580 degrees F.
Hence, fire damage will always be far worse in CFRP with irreversible structural damage vis-a-vis metallics. This plight, of course, also incurs the rightly dreaded FST products of combustion.
This is the case for any or all electrical shorts, arcs, or any other fire sources not merely ELT's. Hence, any fire adjacent to fuselage skin or wing skin will always be far worse for CFRP versus metallics.
Now, was this accounted for in any FAA Special conditions, was it tested for extensively during certification, and finally has Boeing properly assessed all very low thermal conductivity risks due to shorts,chafing, aging, arcs of all electrical wiring, batteries, et al ?
I do not believe such to be the case and now we have a forlorn, and possibly terminally damaged Ethiopian 787, based upon actual repair costs . This aircraft is still sitting in a remote LHR hanger while Boeing and the insurance underwriters presumably debate its final fate. And what might have been merely a minor ELT shorting incident on a metallic aircraft is looking like a total hull loss or a huge and very difficult repair face-saving exercise.
And this present exercise will be replicated many more times for the 787, particularly as electrics age even assuming that they are correctly wired in the first place, I venture to predict. Some airlines and MRO's might care to ponder this note.



Repair issues are between the manufacturer, the operator and the insurer.

Damage assessment is the concern of the regulator and the flying public and that is of my interest as well.

If I understand correctly what you are saying, is that given a small area of overheat will lead to a more severe level of damage in a non-metallic structure. That the lower ignition point contributes to this damage and that said ignition and subsequent flammability gives off noxious fumes.

But yet no confirmation is given that the area of damage thus occurred will grow to the point where safety of flight is affected as compared to the same heat source in an metallic skinned aircraft.

Likewise no confirmation is given that the noxious by-products for such level of "structurally safe" damage will be perfused to affect the passengers.

[A and C]

I don't dispute your opinion for one second about the thermodynamic issues with composite structures, what I do dispute is your opinion on the viability of repair of the structure.

The industry is metalcentric and up untill very recently most people tryed to impose a metal style repair on a composite structure, this was usually expensive, disruptive to the shape of the structure and added weight to the structure, in short just about all the things you do not want in an aircraft repair.

Things have moved on, composite repair is now better understood and even Boeing one of the worst practitioners of composite repairs have moved on considerably. I don't agree with your bleak outlook on the Ethiopean aircraft and think that a repair can be made on an economic basis and not just to save face at Boeing......... Just as long as it is left to those who understand composite repair techniques and the metalcentrics are kept away from the aircraft.

[amicus]

lomapaseo,

Well now, there are a three points to be made and cited. First, all epoxies were banned for aircraft interiors back in the 70's due to passengers being killed by FST. Do you think that edict by the regulatory authorities was unwarranted or without facts?
Secondly, at the LHR Ethiopian incident the fire department reported dense smoke when they entered the aircraft wearing, I would bet, full portable oxygen masks and gear plus full Hazmat. If passengers had been on board would they still be alive?
Finally, why is it taking Boeing and its insurers so long to even decide whether to repair or scrap since July if no safety of flight issue? We are coming up on two months with no actions
You asked for some facts and there they are, I would hope they satisfy you or, at least, give you pause.

[olasek]

Finally, why is it taking Boeing and its insurers so long to even decide whether to repair or scrap since July if no safety of flight issue? We are coming up on two months with no actions The fact that you don't know about it doesn't mean there is no "action".
Boeing stated long time ago that the jet will in fact be repaired but the method of repair will be a private matter between Boeing-insurer-Ethiopian. By the way I see zero evidence (based on aviation literature out there) that this event was "worse" because the fuselage was CFRP. You are entitled to your opinions of course. Ethiopian clearly doesn't share your bleak view of composite airframes - they laud 787's performance, efficiency and they want 8 more.

[Machinbird]

Some typical thermal conductivity values for metallics are: (all units are in the widely accepted and used W/m/K):

Aluminum and its various alloys = 167
Brass = 116
Copper = 339
Steel = 48


And for CFRP it is 0.13, HA!
Yes, CFRP seems to be a pretty good insulator seems to be your point, and will not wick heat away into the adjacent structure, thus the local structural temperature can reach higher temperatures near a thermal event.
What you have omitted to show is information on how rapidly the other side of the structure heats. Heating one side of the skin does not create near-equal temperatures on the other side of a CFRP skin.

I do not think we will ever find molten CFRP flowing back in the airstream in a fire the way we see aluminum flowing during structural fires. It is going to sit there and char and continue to insulate until it is finally burnt through to the other side. If it also has structural loads on it, then it will eventually fail as it degrades and loses strength. In the case of aircraft skin in flight, it may hang on quite a while if the surface can dump enough heat to the local airflow since the layer of char formed near the fire will act as an insulator.

One of the key material issues in a fire is whether or not it will spread a fire. If it self-extinguishes away from the source of heat, then that is what is desired, and I would expect that it could not be certified if it did not self-extinguish.
Fume generation from hot CFRP is an issue, but that should be an engineering challenge that can be solved without making the cabin into a gas chamber.

It is just a different material with different properties. We have to learn what is different about it and adapt our thinking and engineering concepts.

[DaveReidUK]

Finally, why is it taking Boeing and its insurers so long to even decide whether to repair or scrap since July if no safety of flight issue?It may have nothing to do with safety of flight - but it has everything to do with public perception, not to mention Boeing's stock price.

To acknowledge that at this early stage in the 787's career the first one has been written off would be a PR disaster (though arguably Boeing are getting used to those).

[Volume]

Thus, when any short or arc occurs close to CFRP, the skin temperature always peaks higher than the highly conductive aluminum alloys, thereby exacerbating any or all fires besides which, incurring permanent structural damage starting at around 375 degrees F and being flammable with a very low self ignition temperature of 580 degrees FOn the other hand, the thermal conduvtivity of molten aluminum is still about the same as for solid one, while the thermal conductivity of charred CFRP is far less, than the one of intact one. Therefore thick CFRP will protect itself from a localized heat source, while Aluminium will burn through locally. However, this means structural damage and requires a repair. It also means toxic fumes. But especially for thicker material, CFRP stands a local fire better than aluminum from a load carrying standpoint. For thin material both will fail anyway. A hot spot like a shorted wire or an arcing one may do more and more localized damage to CFRP than to aluminum, due to the localized heat which is better dissipated for metals. But when charred on the surface, this effect will quickly compensate the localized heating.
Also remember that for items mainly loaded in plane tension (e.g. a fuselage skin), burning of the resin does not keep the carbon fibres (good for > 2000 °C) from carrying tension loads. Molten Aluminum does not carry anything.
You simply can not compare apples and oranges. And I do not say CFRP is better!

[fenland787]

Finally, why is it taking Boeing and its insurers so long to even decide whether to repair or scrap since July if no safety of flight issue?
It could just be, given that it seems the Honeywell ELT was a key player in all this, that there are some 'full and frank' discussions going on behind the scenes as to exactly who's insurance company is going to be paying anyway?

[tdracer]

It may have nothing to do with safety of flight - but it has everything to do with public perception, not to mention Boeing's stock price.

Boeing stock is trading within a percent or so of it's all time high (and that all time high occurred after the Ethiopian 787 fire) . I'm guessing the public perception can't be all that bad.

[Spooky 2]

tdracer, you don't understand. The sky is falling, or at least for those that wish to remain clueless about this business. ;)

[Chu Chu]

Lots of aluminum airplanes have been lost or badly damaged due to fires. I'd guess almost all of those fires started small, then found fuel somewhere besides the aircraft skin.

Perhaps there will be a whole new class of fires caused by heat sources in proximity only to composite skins. I personally doubt that will happen, but time will tell.

[poorjohn]

Sorry I can't find the reference again - I mentioned it a couple of times in the original battery thread - but the FAA commissioned a study at a university on composite material that iirc was specifically that which was intended for the B787. I have no expertise in the area but glanced through the report and at least did not see anything obviously bogus about the tests or conclusions (that the skin would survive fire well.) Of course, they thought the Li-Ion battery system was perfectly safe, too, so some of the points mentioned up-thread here might have been overlooked.

If anyone is interested in the report and can't find it, ask and I'll dig out a link to it.

[DaveReidUK]

If anyone is interested in the report and can't find it, ask and I'll dig out a link to it.

If you have the link handy, I'd certainly appreciate it, thanks.

[Ian W]

If you have the link handy, I'd certainly appreciate it, thanks.

There is one here http://www.fire.tc.faa.gov/pdf/07-57.pdf

[Machaca]

From Boeing's 787 Aircraft Rescue & Firefighting Composite Structure (http://www.boeing.com/assets/pdf/commercial/airports/faqs/787_composite_arff_data.pdf)


http://i337.photobucket.com/albums/n385/motidog/2013-09-11_105622_zps86f4de32.jpg (http://s337.photobucket.com/user/motidog/media/2013-09-11_105622_zps86f4de32.jpg.html)


http://i337.photobucket.com/albums/n385/motidog/2013-09-11_105653_zpsb4c3e184.jpg (http://s337.photobucket.com/user/motidog/media/2013-09-11_105653_zpsb4c3e184.jpg.html)

[amicus]

Machaca
Boeing total PR codswallop And if not a problem, why epoxies banned for interiors since 1970's?

[Machaca]

Why are you conflating interior fitment and structural epoxies?

Seems disingenuous, particularly when you don't address the specific burn properties of the modern epoxy developed for the 787.

Please enlighten us all by addressing the seven bullet points above.

[lomapaseo]

My read between the lines of the Boeing PR is the major source of toxicity is the interior panels of the aircraft.

Neither the aluminum nor the 787 outer structure contribute significantly except for the time to be defeated by an external fire.

My memory of such external fires is almost solely comprised of ground fuel-pooled fires.

An internal cabin fire is clearly another problem.

I am curious what a Asiana fuselage might look like along the fuselage top after the fire breaks through to inside the cabin, but that's just a structural damage question and not germain to toxicity.

[amicus]

lomapaseo

My concern is that the vast majority of survivable crashes, (in fact the norm) for commercial aircraft result in compromised, fractured, open doors , open slides,etc, thus allowing ingress into the cabin of toxix gases and smoke from the external CFRP fire. I have cited over 150 such commercial airline survivable crashes to both Boeing and FAA since 1970, all involving compromised and fractured fuselages to no avail.
To my knowledge this critical safety condition was never tested for during development and certification of the 787. Specifically, Boeing did burn-through tests via cone calorimeters only on intact and non-compromised panels and the FAA and Boeing both refused to replicate the Air France A340 Malton overrun crash a few years back, which would serve as an ideal and totally reproducible example of such survivable fuel fed fire crashes. This could easily be performed on on of the four now non-flying 787 prototypes and such a test, replicating a survivable fuel fed fire crash with 100% passenger and crew survival in the case in the A340 with a fuel fed ground fire would end the debate on either side of the FST issue.

To quote the old aviation aphorism "One test is worth 1000 expert opinions".

[Kiskaloo]

Then I guess, amicus, passengers flying on the CFRP A350 and the significantly CFRP and composite (GLARE) A380 are also pretty much whistling past the graveyard every time they board one of those planes, as well.

In fact, having flown the 787 and A380 a number of times (and with my airlines of choice also choosing the A350), I guess I better make sure my life insurance is up to date. :mad:

And god save us when the CFRP A320 and B737 replacements start entering service in the 2030s... Ralph Nader is no doubt working on a new book to lambast Airbus and Boeing on their decision to move to CFRP. I suggest he go with the title Unsafe At Any Altitude. :D

[Machaca]

amicus: ...the FAA and Boeing both refused to replicate the Air France A340 Malton overrun crash...


Refused who? Why reproduce an accident from which everyone successfully evacuated?

[olasek]

Refused who?I assume refused HIM. HE suggested and they refused, how nasty and inconsiderate of them.
would end the debate on either side of the FST issue.Assuming there is a debate. This forum is hardly a place to find out if there is a debate (among real 'experts') or not.

[Kiskaloo]

Well if Boeing should destroy one of the 787s in such a test, Airbus should also be required to sacrifice MSN001 of the A380 and A350, as well. :rolleyes:

[esscee]

Now that the -9 is flying and gaining orders, what odds on Boeing slipping out the bad news regarding the Ethiopian 787 being "beyond economical repair".

[bvcu]

Wouldnt put the A380 'Glare' in the same league as carbon fibre . Anyone remember the hazards with the harrier composite materials in an accident . Boeing wouldnt be aware of that having responsibility for the AV8B now......!

[neilki]

Qantas'll have her... :ouch:

[Machaca]

FAA to issue AD (http://www.faa.gov/news/updates/?newsId=73882):

The FAA is issuing an Airworthiness Directive (AD) identical to the August 26 Transport Canada Civil Aviation (TCCA) directive which requires airlines to inspect Honeywell emergency locator transmitters (ELTs) by January 14, 2014 to prevent an electrical short and possible ignition source. The FAA AD has the same deadline for the U.S. fleet and will impact approximately 4,000 airplanes at a total cost of approximately $325,720. The investigation of the July 12, 2013 Ethiopian Airlines Boeing 787 fire at Heathrow Airport continues under the leadership of the United Kingdom Air Accident Investigation Branch (AAIB).

[Volume]

Wouldnt put the A380 'Glare' in the same league as carbon fibre Actually Glare is certified to be fireproof. It outperforms aluminum by several orders of magnitude. It even outperforms steel depending on the exact test setup. It is used as firewall and as cargo liner fire barrier. It´s a shame that Airbus did abandon it on the A350.

[inducedrag]

Will the aircraft become flyable and return to normal flying or will be grounded :ugh:

[Hi_Tech]

Has anyone got news on the repair status of this grounded Ethiopian aircraft? Would like to hear about the progress - just curious.:ouch:

[Dave Cummings]

I am led to believe she had had her engines removed and parts of the interior. As far as the repair is concernee no one really knows. I run a website that catalogues the dreamliner airframes and incidents etc (b787register) and I have tried to contact Ethiopian but they never respond.
I wouldn't at all be surprised to see her broken up

[JT Eagle]

But until I do, here it is:
Ethiopian 787 'Queen of Sheba' | Flickr - Photo Sharing! (http://www.flickr.com/photos/38857033@N08/9895245333/)

[poorjohn]

b787register.co.uk for the curious

[DaveReidUK]

But until I do, here it isAnd it certainly hasn't had its engines removed in the two weeks since that photo was taken.

It's currently occupying Stand 616 at LHR (western side of the Cargo cul-de-sac) while its fate is being considered.

[Dave Cummings]

I wonder if she had the engines removed for some knida maintenance or even if I had been fed some duff info.
It looks like from the photo she has the inlets covered for her engines. Perhaps thats where the confusion was someone saw people putting these covers on and assumed the engines where being removed?

[lomapaseo]

OTHO why would you leave engines sitting idle for several weeks when they should be located in a spares location in case somebody needs one immediately ?

[DaveReidUK]

OTHO why would you leave engines sitting idle for several weeks when they should be located in a spares location in case somebody needs one immediately ?If somebody needed one immediately, that would only help if they had conveniently gone u/s at wherever you had chosen to locate the spares. :O

I suspect there are enough spare GEnx engines already to support the fleet, anyway.

There is also the issue of perception - while ETH and Boeing are trying to maintain the impression (whether true or not) that the aircraft isn't a write-off, it wouldn't be good PR to have the aircraft start to look like a Christmas tree.

[E_S_P]

OTHO why would you leave engines sitting idle for several weeks when they should be located in a spares location in case somebody needs one immediately ?

I would presume that until the lawyers/insurance underwriters have fully established the cause/liabilty, the a/c would remain intact until the time a descision is made about what will happen to it.

[Dave Cummings]

Let's be hones if they could repair it they would have started working on it and not prepared it for what looks like long term storage or worse

[glad rag]

OTHO why would you leave engines sitting idle for several weeks when they should be located in a spares location in case somebody needs one immediately ?

:ugh: Depends if they have fuel filters is one guess. :ugh:

[DaveReidUK]

they would have started working on it and not prepared it for what looks like long term storage or worseOther than wheel covers and engine blanks (both readily removable) I can't see any evidence of preparation for long-term storage. The doors haven't been taped, the transparencies haven't been blanked, etc, and even if it were destined for storage that clearly wouldn't be in situ, where it must be clocking up a fortune in airport parking charges.

[tdracer]

If the decision had been made to scrap it, I'd expect the engines and other high value LRUs would already be removed.

Without knowing the extent of the (non-structural) fire damage to the interior, I'd think the easiest repair would be to simply replace the aft fuselage tail section. The 787 fuselage is manufactured as sections - nose, a few constant diameter pieces, and tail - based on the pieces I see sitting around at Boeing waiting for final assembly, the tail section would have most if not all of the structural damage.

A bigger issue might the interior - I suspect most of the interior suffered smoke damage and would need to be replaced (that smell simply does not go away).

It's also possible that if the air safety investigation is still open, it may be quarantined in case the authorities want to do further inspections.

[glad rag]

It's also possible that if the air safety investigation is still open, it may be quarantined in case the authorities want to do further inspections.

Nail hit on head.

[lomapaseo]

It's also possible that if the air safety investigation is still open, it may be quarantined in case the authorities want to do further inspections.

No way,

none of this "just in case" stuff when it comes to million dollar resources.

The investigators will be happy to continue a leisurely investigation only if the owner is not actively using the plane for anything else.

[tdracer]

No way,

none of this "just in case" stuff when it comes to million dollar resources.

The investigators will be happy to continue a leisurely investigation only if the owner is not actively using the plane for anything else.

I take it you've never been involved in an air safety investigation. Getting an asset back into service is pretty low on their priority scale.

[glad rag]

I take it you've never been involved in an air safety investigation. Getting an asset back into service is pretty low on their priority scale.

I think he was being sarcastic.

maybe.

[lomapaseo]

Not being sarcastic.

It's one thing to have an active investigation with a timeline. Quite another to have a pseudo investigation with no time line when it comes to high value assets.

If you leave this open then you will quickly have no industry to investigate.

We may have different opinions but I see no data to support frozen high value assets without a time line.

[olasek]

It's also possible that if the air safety investigation is still openIt is possible but I see slim to zero chance it will uncover anything new or significantly change the current findings, otherwise we would have known by now.

[DaveReidUK]

"Detailed examination of the ELT and the possible mechanisms for the initiation and sustaining of the fire in this aircraft continues. Further updates on progress will be published as appropriate."

http://www.aaib.gov.uk/cms_resources.cfm?file=/S5-2013%20ET-AOP.pdf

Sounds like an open investigation to me.

[TwoStep]

Re: Ethiopian 787 'Queen of Sheba' | Flickr - Photo Sharing! (http://www.flickr.com/photos/38857033@N08/9895245333/)

Is it me, or have the once clearly visible scorch marks at the base of the fin disappeared?

http://www.nycaviation.com/newspage/wp-content/uploads/2013/07/snip6.jpg

http://farm3.staticflickr.com/2881/9895245333_d5c02e76cb_c.jpg

[bvcu]

white speedtape........

[tdracer]

white speedtape........ Or Krylon rattle-can spray paint :rolleyes:

[Fzz]

Even right after the fire, it doesn't look like the damage was very visible from the starboard side:
http://www.airlinereporter.com/wp-content/uploads/2013/07/EhtReg-640x351.jpg

[lomapaseo]

Sounds like an open investigation to me.

Agree


but using what required resources. Are they by demand (impounding) or as available under some terms of agreement?

[LHRops]

With ref the 787 that is parked up on stand 616 in cargo, there is a pile of scaffolding on the ground to erect so they can start some sort of work,

watch this space over the next few days for something to happen !!!

[poorjohn]

It is possible but I see slim to zero chance it will uncover anything new or significantly change the current findings, otherwise we would have known by now.The fact that the a/c has been on the ground for lo these many $$$$ suggests that someone thinks there is something important to learn. Yet another 787 surprise for Boeing engineers to unwrap?

[olasek]

$$$$ suggests that someone thinks there is something important to learn.Your own guesswork.

It was recently explained in an article in AW&ST that Boeing is working with Ethiopian and insurer to come up with the best fix and a lot of engineering work is required.

Even though the investigation is ongoing I doubt (and I am sticking with it) anything new will be learned about the fire since there would be plenty of leaks by now.

The 787 haters must wait for something else ...

[Machinbird]

There probably is quite a bit to learn from this accident in the direction of structural repair techniques for CFRP.

I'll expect that the engineers are hard at work inventing and testing new techniques for restoring heat damaged CFRP structure. Perhaps even something other than just cutting the damaged structure away and replacing it.

Then there are going to be a lot of damaged internal systems in the vicinity of the fire that will need outright replacement and thus will need to be procured.

[denachtenmai]

Boeing is working with Ethiopian and insurer to come up with the best fix

The 787 haters must wait for something else ...
The first reassures me, not, is it the engineers or the beancounters driving this "fix"?
The second is just :yuk: SLF, like me now, don't hate the 787, we are just, shall we say, apprehensive about flying on one.

[cockney steve]

Den, the fixed costs should be readily estimated......cost of capital to finance aircraft......cost of time -constrained maint/overhaul/replacement
depreciation.
Fluid costs are storage and admin (plus lawyers?)

Assets are the reusable components/contents of the hull, less cost of dismantling and removal.

Bean-counters will want a big gap between the projected cost of re-commissioning and net revenue from breaking.
the repaired hull may well have a reduced resale value but that's not relevant as the owner would tend to use it's full life in revenue service (this (ethiopian) would produce the same return as a non-repaired hull)

The longer it sits, the more the gap in viability of repair shrinks. Remember, the "industry" surrounding the loss/ repair all want paying, as does the airport.

Rome /Nero / Fiddle /Burn (highly appropriate under the circumstances :\ )

[Chu Chu]

Steve,

Seems to me the gap shrinks significantly only if you know in advance that the aircraft will sit for an extended period before repairs begin. If the repair decision is made (or reconsidered) at the end of the waiting period, the storage/debt service/etc. costs are sunk and have to be subtracted from either the salvage value or the value of the repaired hull.

[edmundronald]

If the engineers are busy inventing and testing repair techniques, as has been suggested, does this mean they are going to use the plane and SLF as a flying test bench?

[foxvc10]

IF they do scrap it, its not going to be cheap.

All that yummy carbon fibre with no home to go to.

[FullWings]

I'd have thought there were two main options:

1. Repair what they can in-situ, then add enough strengthening inside and outside to make it airworthy (but ugly). Fly it empty and depressurised to Boeing or somewhere that can do the job properly in a controlled environment. This will probably involve the replacement of a large section of the fuselage with a new construct.

2. Attempt to get it back to 'showroom standard' while it's parked outside at LHR during the winter (if they can't hire some hangar space). Largely a voyage into the unknown, I'd guess.

[denachtenmai]

C/Steve, I understand.
Whichever way one looks at it though, this is going to be costly for Boeing.
I hope they succeed in overcoming their problems, Thomson's 787's go over me at around FL 15-20 and they look nice through the video amps :)

[poorjohn]

Repair what they can in-situ, then add enough strengthening inside and outside to make it airworthy (but ugly). Fly it empty and depressurised to Boeing or somewhere that can do the job properly in a controlled environment. This will probably involve the replacement of a large section of the fuselage with a new construct.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.

[A and C]

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.

[Ian W]

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

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

[DozyWannabe]

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

[joy ride]

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

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

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

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

[A and C]

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

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

[olasek]

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

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

[HeavyMetallist]

@olasek:

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

[A and C]

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

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

[bvcu]

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

[A and C]

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

[SLF3]

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

[YRP]

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

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

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

[tdracer]

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

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

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

[Una Due Tfc]

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

[beamender99]

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

Airbus item
Qantas A380 to resume operational service*| Airbus News & Events (http://www.airbus.com/newsevents/news-events-single/detail/qantas-a380-to-resume-operational-service/)

[Machinbird]

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

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

Although epoxies are essentially insoluble, it might be possible to remove thermally degraded matrix without significantly disturbing the carbon fibers. A laser method of CFRP surface preparation is discussed here. (http://cleanlaser.de/wEnglish/anwendungen/cfrp-repair.php)
There may be variations of the water jet technique that will work assuming the proper working fluid.


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

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

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

Has anyone here actually seen the condition of the interior?

[Bigpants]

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

[A and C]

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

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

[FullWings]

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

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

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

[DaveReidUK]

then fly it back somewhere warm and dry where they can chop the burnt section out and attach a new oneOr, if all else fails, remove the manufacturer's identification plate and attach a new airframe to it ...

[denachtenmai]

which they know how to do as it's part of the manufacturing process.
I think that one far eastern airline would challenge that, and that a/c was not made of exotics:(

[Interested Passenger]

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

[A and C]

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.

[tdracer]

I think that one far eastern airline would challenge that, and that a/c was not made of exoticshttp://images.ibsrv.net/ibsrv/res/src:www.pprune.org/get/images/smilies/sowee.gif


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

[Una Due Tfc]

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

[FullWings]

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.
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?

[phiggsbroadband]

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

[DaveReidUK]

That's not going to happen.

[A and C]

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

[wild goose]

A and C

Possible, good sir.
Posing is something charlatans enjoy.

[denachtenmai]

Assuming you're speaking of the JAL 747, the repair was designed correctly - the problem was it wasn't implemented properly.
Exactly, wasn't the repair done by Boeing technicians?

[peter we]

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?

[DaveReidUK]

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/images/060213-2final.jpg

[DozyWannabe]

@DaveReidUK:

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

Photos: Boeing 747-206BM(SUD) Aircraft Pictures | Airliners.net (http://www.airliners.net/photo/KLM---Royal/Boeing-747-206BM(SUD)/0952826/L/)

[DaveReidUK]

It seems they can do it with a 747 vertical stab, which is much larger and more unwieldyYes, you can get away with pretty well anything with an aircraft that isn't intended to fly again. :O

[tdracer]

Yes, you can get away with pretty well anything with an aircraft that isn't intended to fly again. http://images.ibsrv.net/ibsrv/res/src:www.pprune.org/get/images/smilies/embarass.gif


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).

[DaveReidUK]

Removing the vertical stab is a pretty routine procedure for allowing airplanes to into hangers that otherwise would have inadequate clearanceWell I've never encountered that, but I'll take your word for it.

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

[DHC4]

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.

[golfyankeesierra]

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

Removing the vertical stab is a pretty routine procedure for allowing airplanes to into hangers that otherwise would have inadequate clearance
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..

[tdracer]

25 years ago I watched them, (well technically I watched them re-install, not remove the vertical stab) on the second Air Force One 747 so that it would fit in a hanger in Wichita. They didn't use any fancy tooling - a portable crane and lots of people. I didn't watch the whole thing (it was something like an all-day procedure) but I know it was completed successfully.

When I asked it this was unique, I was told "not particularly" - there are a lot of hangers put there that can take the length and width but not the height of a 747.

[Mr @ Spotty M]

tdracer is spot on, we used to back in the 70s routinely swing the Vertical Stab over on B720 & B707 aircraft to get the aircraft into the corner of the hangar.
By the way, l have recently been at a conference held by Boeing on the B787 and someone asked within Boeing if they could info us what is going on with the a/c.
He was told Boeing is not allowed to comment, it is up to the operator to give details.
Guess it lies with the insurers, airline & Boeing to come up with a plan.

[KelvinD]

I think all the above has now become irrelevant. It looks as if work is underway to repair it where it stands: http://pbs.twimg.com/media/BWT9ytwIQAEurvq.jpg:large

[bvcu]

think that looks more like the white paint going on !

[DaveReidUK]

think that looks more like the white paint going on !Quick, before anyone twigs what airline it belongs to ! :ugh:

[Ian W]

tdracer is spot on, we used to back in the 70s routinely swing the Vertical Stab over on B720 & B707 aircraft to get the aircraft into the corner of the hangar.
By the way, l have recently been at a conference held by Boeing on the B787 and someone asked within Boeing if they could info us what is going on with the a/c.
He was told Boeing is not allowed to comment, it is up to the operator to give details.
Guess it lies with the insurers, airline & Boeing to come up with a plan.

It is not Boeing's aircraft - they sold it. So decisions will be based on the Insurer and the owner Ethiopian, I would not be surprised if Honeywell is not being drawn in by a claim against their insurers due to the ELT being blamed. All this insurer to insurer negotiation takes an inordinate length of time. The only information Boeing could give is costs of various repair options and their expected outcomes.

I would suspect that Boeing would really like to have that fuselage barrel for strength testing by an independent assessor so they could set customer's minds at rest on the effect of an airborne fire (and perhaps quieten the peanut gallery). But it is not Boeing's decision.

[A and C]

For a professional aviation website some of the comments above surprise me, there seems to be a total lack of understanding of just how much you can do in terms of repairing aircraft ( be it composite or metal).

I can only assume that this is a reflection on today's throw away culture and the fact that people no longer fix things. I notice this cultural change most in the young FO's I fly with most are driving almost new cars that are maintained professionally, at their age I was riding old motorcycles that without constant attention from myself simply would not run.

[Mr @ Spotty M]

I know its not Boeing's aircraft and l did not say it was.
You seem to be little naive of Boeing's involvement with regards to the insurer.
The aircraft can only be repaired with repair instructions from Boeing.
The Insurer and Boeing will work out the repair with its costs and then relay that to the owner Ethiopian (if they do own it).
Ethiopian could decide to write it off, but they will only receive the money that the insurer is willing to pay.

[lomapaseo]

In spite of the appearance that posters are sniping at each other, if you merge some of these posts together there are some pretty good assessments here.


:ok:

[TURIN]

The aircraft can only be repaired with repair instructions from Boeing.

I understood that some of the bigger MROs/airlines had received design approval for repairs on type. I could be wrong of course.

Rumours are that the repair patch (for want of a better word) arrived at LHR on far eastern airline (SIA?) last week.

[WHBM]

For all this talk about insurer's liability for the fire damage, I presume the aircraft is actually still under manufacturers warranty. It was only delivered in November 2012, less than 8 weeks later it was grounded, returned to service in April 2013, and 11 weeks after that a component had a fire. I would have thought it was still very much Boeing's warranty liability at that point.

[KelvinD]

It may be. On the other hand, look at all the generator sets parked alongside; as if someone is planning to do some serious work. And isn't it ironic, that when you look closely at the right hand edge of the photo, there is another aircraft. Another Ethiopian!

[Charlie_Fox]

Something else about that photo: the steps to L1 door are from DNATA which makes me think Dubai rather than Heathrow. Mind you I haven't been to Heathrow for five or six years - has DNATA established a foothold at Heathrow?

[Cows getting bigger]

Dunno about the steps but the control tower is a bit of a giveaway! :)

[KelvinD]

DNATA are all over Heathrow now. When I first saw them there, I had the same surprise. I had always associated them with Abu Dhabi & Dubai.

[tdracer]

Rumours are that the repair patch (for want of a better word) arrived at LHR on far eastern airline (SIA?) last week.
If true, that would pretty much rule out replacement of the tail barrel section - there is only one aircraft out there that can carry the 787 barrel sections and that is the Boeing Large Cargo Freighter (LCF - better known outside Boeing as the "Dreamlifter").

I figure Airbus was quite happy that Boeing came up with the LCF - it's the only airplane out there that's more :mad: ugly than the A380 :E.

[Rwy in Sight]

Since we did get the conversation on the insurance aspects who pays the parking fees for the time the aircarft remains at Heathrow? Even with a discount the cost could be pretty high if the airport does not give a discount.

[LiveryMan]

I figure Airbus was quite happy that Boeing came up with the LCF - it's the only airplane out there that's more http://images.ibsrv.net/ibsrv/res/src:www.pprune.org/get/images/smilies/censored.gif ugly than the A380 http://images.ibsrv.net/ibsrv/res/src:www.pprune.org/get/images/smilies/evil.gif.

I beg to differ, the A350 with the A380 cockpit section shoehorned onto it looks worse. And painting the window surround black in an effort to make it look as slick as the 787 doesn't cut it! The whole plane looks out of balance.

[nicktabs]

Another view of the repair from @MPSinthesky

https://pbs.twimg.com/media/BWig9I1IEAAPWCk.jpg:large

[fenland787]

I heard Mike Carriker say that when they first flew the Dreamlifter into a french airport they had painted a third row of windows on the side. Not sure if it was true, but a great idea!

[Cows getting bigger]

Slightly more complex than a sheet of aluminium and a rivet gun.:eek:

[superq7]

Cows

Agree and a lot more expensive.

[fenland787]

Presume there is going to be need to control internal and external temp and humidity if a composite repair is done too (hence the scaffolding frames going up?) that ain't gonna be cheap through the UK winter!

[Machinbird]

Looks like forward scaffold is for staging internal components in and out of the aircraft.
The aft scaffold is for conducting structural repairs.

They are building a regular tent city there behind the aircraft.

[DaveReidUK]

I suspect that once the repair gets under way, the Met Police will be leant on not to publish any more photos taken by their helicopter pilots.

[A and C]

You could not be more wrong about the control of the temp & humidity for the final stages of the repaires. I would put the cost of doing so at £1500-2500.

The big tent is about keeping the workers dry and walm during the preparation work.

[Romulus]

You could not be more wrong about the control of the temp & humidity for the final stages of the repaires. I would put the cost of doing so at £1500-2500.

I rather suspect they have blown that budget already...

No figures in here but it is interesting to consider some of the prior commentary.

Boeing Switches To Repair Mode After 787 Fire (http://www.aviationweek.com/Article.aspx?id=/article-xml/AW_07_22_2013_p22-598174.xml)

[DozyWannabe]

Nice article, and recommended reading - even if it only summarises the questions rather than providing answers. The possibility of performing a patch repair to allow for a ferry flight to Boeing's facilities for a more permanent solution is an intriguing one.

[A and C]

You will note that I said that was for the final post cure part of the repair and adressing the temp & humidity issues, as with all things composite the real work is in the preparation...........and you won't be doing that on the cheap !!

[VFD]

Nice article, and recommended reading - even if it only summarises the questions rather than providing answers. The possibility of performing a patch repair to allow for a ferry flight to Boeing's facilities for a more permanent solution is an intriguing one

I believe that somewhere in the process that the aircraft is going to return to PAE. Whether it be for some type of re-certification or to do a final structural analysis on the repair. Then clean and replace heat and smoke damaged interior parts. Just a guess.

Cost, I suspect there is some negotiations between Honeywell, Boeing, Ethiopian and the insurance company with Ethiopian getting some kind of guarantee of performance of the aircraft after the Boeing repair. I would doubt that Ethiopian would accept flying around a multi-thousand pound weight penalty for doubled panels to repair the damage on a new aircraft for the rest of its life.

So far other than the external pictures we have no real idea of the actual structural damage to the fuselage and the heat damage to the rest of the aircraft. We can guess from the number of containers, tents and scaffolding that this is going to be a major time consuming and costly repair.

[tdracer]

There were a couple 787 tail barrel sections parked outside the office building today. Comparing those to the published pictures of the Ethiopian airplane, notice forward of the aft door, there are a few windows and then a 'missing' window? The 'missing' window is the break where the fuselage pieces are joined. At least externally, the worst of the fire damage appears to be aft of that joint.

Again, not knowing what the internal damage looks like - I'm leaning towards the most cost effective fix being to replace that tail barrel section. Either on site at Heathrow, or if the GSE is too complex, a temp fix to get it back to Everett or Charleston where the tooling is available.

Even if it's a $100+ million price tag, compared to a new 787 it would still likely make economic sense (recall the A380 $150 million/18 month repair bill after the Qantas turbine failure)

[Machinbird]

So far other than the external pictures we have no real idea of the actual structural damage to the fuselage and the heat damage to the rest of the aircraft. We can guess from the number of containers, tents and scaffolding that this is going to be a major time consuming and costly repair.I think this is going to be a complete repair with a fully airworthy aircraft the result and it will occur where it sits now.

Everyone is agonizing over the structural repair feasibility and some are speculating that the aircraft will be made ferryable and flown elsewhere.

If they were going to ferry the aircraft, you would see a much smaller operation. It doesn't have to be pretty to ferry an aircraft. A ferryable aircraft does not have to meet full airworthiness standards. It merely needs to be demonstrated to the applicable airworthiness authorities that it is capable of the ferry mission.

The interior of the aircraft is going to be stripped from the aircraft and processed in those tents or in an industrial setting as appropriate to the component. Actual fire damaged components are going to be scrapped and replaced, not overhauled. Same for interior furnishings that are not recoverable due to smoke damage. Part of the delay in starting the repairs had to be the process of gathering the known replacement items.

When the interior is out, and the exterior preparations made, the structural repair will commence. There will be sufficient design engineering staff on site to advise and coordinate on any unexpected discoveries.

I would be personally surprised if the structural repair lasts more than 60 days, and by ~90 days the aircraft should be back together and ready for flight, but I wouldn't claim to be an expert on the subject. I've only been involved in aviation for half a century.

[DaveReidUK]

There were a couple 787 tail barrel sections parked outside the office building today. Comparing those to the published pictures of the Ethiopian airplane, notice forward of the aft door, there are a few windows and then a 'missing' window? The 'missing' window is the break where the fuselage pieces are joined. At least externally, the worst of the fire damage appears to be aft of that joint. Fire doesn't care about manufacturing joints, so it might be premature to rule out significant damage forward of the tail break. I wouldn't be surprised if not only Section 48, but also Section 47 is deemed unrepairable and is replaced.

http://i.bnet.com/blogs/787-sections.jpg

Again, not knowing what the internal damage looks like - I'm leaning towards the most cost effective fix being to replace that tail barrel section. Either on site at Heathrow, or if the GSE is too complex, a temp fix to get it back to Everett or Charleston where the tooling is available.I would agree that it's not going to fly out of Heathrow in a factory-fresh state. I can't see a permanent repair being carried out, whether or not it involves replacing major parts of the structure, al fresco during the British autumn and winter.

Even if it's a $100+ million price tag, compared to a new 787 it would still likely make economic sense (recall the A380 $150 million/18 month repair bill after the Qantas turbine failure) Not that economics is the sole consideration, any more than it was for the Qantas A380.

[E_S_P]

tdracer

Comparing those to the published pictures of the Ethiopian airplane, notice forward of the aft door, there are a few windows and then a 'missing' window? The 'missing' window is the break where the fuselage pieces are joined. At least externally, the worst of the fire damage appears to be aft of that joint.


Just looking back at the original photos of the incident and what tdracer has confirmed, that the missing window was a join. It does appear that the area of damage extends forward of this joint, and you can see a 'band' of where the charring hasn't penetrated the outer layer - presumably where either the reinforcement ring is. Given this is a highly stressed area, could they be looking at 2 sections "if" they end up replacing rather than repairing....?

Either way, it should be fun (not) for them working under canvas if the hard winter forcasts are correct. :sad:

[A and C]

I'm very glad that most of the people posting above don't work for me, the negative attitude is remarkable.

It will be interesting to see the course of action that Boeing take with the aircraft, I fear that the metalcentric lobby has won the day if the whole fuselage section is going to be replaced but I guess we will never know if this is driven by political or technical reasons.

As to working in a "tent" that is no problem as long as you double skin it and have the appropriate heating rigged up.........done that...... No drama.

[TwoStep]

Reliably informed that the tail was removed from ET-AOP today in the first part of the repair work.

[DaveReidUK]

Reliably informed that the tail was removed from ET-AOP today in the first part of the repair work.

Yes - the vertical stabilizer, to be precise.

[DaveReidUK]

Photo here: ET-AOP EGLL 18-10-13 | Flickr - Photo Sharing! (http://www.flickr.com/photos/57530104@N02/10341011313/)

[barit1]

I take it as given this exercise is more than just a repair/return to service to ET-AOP.

It is also Boeing's experiment in major structural repair of composites. As such, the first objective may see some overkill.

[Yancey Slide]

Apparently Boeing has a tech team who goes around and does major repairs in the field. National Geographic had a show which documented the replacement of an aft pressure bulkhead on a 767 by removing the aft sections. I found it pretty interesting. Course, on this one you can't use 5,000,000 rivets on this to put it all back together, but generically it wouldn't be the first time that they'd split a hull at a seam, done work, and put it all back together somewhere other than at the factory.

[Ian W]

I take it as given this exercise is more than just a repair/return to service to ET-AOP.

It is also Boeing's experiment in major structural repair of composites. As such, the first objective may see some overkill.

Experiment is probably the incorrect term, they will have had many 'experiments' before going with the composites. It would be correct to call this a "demonstration of a major structural repair of composites." the prime objective will be to get it right.

From an industry point of view everyone will be interested - it is not a Boeing only problem, A-350's will be in the same boat. An effective repair and back to flight will quieten the noise from the peanut gallery about composites. Already, thanks to the prolonged flame throwing ELT strapped right against the composite hull, it is apparent that composites will not irretrievably combust.

This mishap although unwelcome could in the longer term become a positive.

[superq7]

Ian

Am not Boeing bashing but the A350 is manufactured using composite panels I would think a lot easier to repair than Boeings barrel construction.

[DaveReidUK]

it wouldn't be the first time that they'd split a hull at a seam, done work, and put it all back together somewhere other than at the factoryAssuming that's what they are going to do this time ...

[Machinbird]

I interpret the Flickr picture as follows:
The VS is off the aircraft because it was in the way for some of the structural repair that will occur. The aft scaffolding defines the area that will be receiving significant structural repair along the crown of the fuselage.

Next, They will build a tent over the scaffolding that spans the aft fuselage.

Watch the forward scaffolding and the lower deck of the aft scaffolding for action. That will be the outflow of internal components as the strip out commences. Start your repair stop watch then. What you see now is facilitation.

The total operation is likely phased so that the expensive repair crew spends minimum time on site.

All you sidewalk superintendents pull up a seat.:}

[lomapaseo]

I expect them to erect a tent over the whole thing so all the sidewalk superintendents will have to guess what's happening inside

[LiveryMan]

Am not Boeing bashing but the A350 is manufactured using composite panels I would think a lot easier to repair than Boeings barrel construction.

Assuming of course the fire did not melt/burn the aluminium composite frame the panels attach to. How easy is that to replace?

In actual fact, the fire may have been propagated on the A350, as aluminium is a very good heat conductor. Who is to say the fire would not have taken out the whole crown and thus write the thing off?

But, like your suggestion the A350 would be easier to repair, that's idle speculation :ok:

[DozyWannabe]

It would be correct to call this a "demonstration of a major structural repair of composites."

Agreed.

An effective repair and back to flight will quieten the noise from the peanut gallery about composites.

Most of the grousing comes from those who are thinking of older types of composite, or those who are basing their reasoning on flawed, outdated or simply incorrect information. Admittedly when the concept was first floated I was thinking of the Comet days and that it would be a leap into the lesser-known material properties of a similar magnitude - but later reading somewhat calmed this opinion when it became clear that the level of modelling and physical testing as well as materials knowledge was much more thorough.

[glad rag]

Ian

Am not Boeing bashing but the A350 is manufactured using composite panels I would think a lot easier to repair than Boeings barrel construction.

Biggest Airbus A350 XWB carbon fuselage panel manufactured | AVIATIONNEWS.EU (http://www.aviationnews.eu/2011/03/18/biggest-airbus-a350-xwb-carbon-fuselage-panel-manufactured/)

http://www.eads.com/dms/Press-DB/EADS/Financial_Communication/2011/March/Photo-release/panel_pag_490_318.jpg

http://www.aviationnews.eu/blog/wp-content/uploads/2011/03/panel_a350xwb_490_318-400x259.jpg

Very interesting indeed!

[oliver2002]

some more info: Sources: Damaged Ethiopian Airlines Boeing 787 to Undergo Major Repair in London » Airchive (http://airchive.com/blog/2013/10/17/ethiopian-airlines-boeing-787-repaired-london-patch/)

[DaveReidUK]

Sources: Damaged Ethiopian Airlines Boeing 787 to Undergo Major Repair in London » Airchive (http://airchive.com/blog/2013/10/17/ethiopian-airlines-boeing-787-repaired-london-patch/)"once the damaged areas are sanded away" - love it !!

[FORDGT40]

Even better "The incident was sparked on July 12th......"

[Ozlander1]

"once the damaged areas are sanded away" - love it !!
The workers are probably union and paid by the hour. :bored:

[jimjim1]

Ozlander:-

"The workers are probably union and paid by the hour"

If that was the case I would say good for them. Why would anyone do otherwise?

The tragedy is that in Britain today (and for the last 30 years) workers are getting poorer year by year and bosses (to make it simple) are getting commensurately richer.

The whole British economy is now run on a Pay To Fly basis.

If you do not think that you can get yourself into the top 10% (today about £160k) then I recommend that you leave Britain. The top 10% are presently in the process of rendering the rest of the population destitute.

Because they can.

[Scuffers]

£160k puts you well into the top 1% of UK tax payers, and this 1% contribute some 30% of tax revenue.

so yes, they are really ripping off the system :ugh:

[Volume]

An effective repair and back to flight will quieten the noise from the peanut gallery about composites. That will be highly depending on the price tag that is attached to the repair.
Nobody said it would not be possible to repair composites. The remaining question is whether it is economic to do so.
And this event, linked to an incident and an investigation, is probably not representative for the time it requires to do such a repair.
So there will be more noise in the future

[olasek]

The remaining question is whether it is economic to do so
This has been settled long time ago.
Every repair is different but airlines are interested in repairs that happen most often - bends and nicks caused by service vehicles at airports. This is where they loose a lot of $$ every year. The repair techniques developed for such repairs in the composite world are multiple time faster than with the aluminium body and some small damages that require repairs on aluminium aircraft will require no repair at all on a 787.

[superq7]

olasek

As I'm sure your aware this "incident " hardly comes into said " bends and nicks" category.

[Machinbird]

So. Does anyone have some fresh pictures of what is going on?

Have they started stripping out the interior?

You don't have to see into the tent to make an educated guess as to what is going on inside. Just observe the flow of material in and out.

[olasek]

As I'm sure your aware this "incident " hardly comes into said " bends and nicks" category.
No, it doesn't but you clearly missed the thrust of my argument. I was talking about aircraft skin repair in general, those that produce largest losses for airlines. Also, there are many aluminium repairs that are no longer economical.

[denachtenmai]

olasek

some small damages that require repairs on aluminium aircraft will require no repair at all on a 787.

Care to elaborate, and by the way, how do you know this is correct?

[joy ride]

Regardless of construction materials I see little similarity between a minor ding caused by a service vehicle and the damage caused by this fire. This has taken 3 months of planning and a fair build up of tents, equipment and materials.

The cost of all this, plus the cost of all the airport space, the repair team and the loss of revenue put this event into an entirely different category, one which will hurt the Insurers, Boeing, Honeywell and Ethiopean.

[A and C]

Your surprise at the comments about " sanding the damaged part away" show your lack of understanding of composite repair techniques, to my surprise and delight it would seem that the composite engineers have won the day and we are not going to see a metalcentric repair if this report is true.

Full marks to Boeing for keeping faith in the composite technology.

[DaveReidUK]

Your surprise at the comments about "sanding the damaged part away" show your lack of understanding of composite repair techniques.Gosh, that's told me.

And to think that I turned down the chance to buy shares in that sandpaper manufacturer. :ugh:

But I suspect that whatever repair technique and materials are being used, cutting out the damaged structure doesn't just involve a bloke with a Black & Decker and a few sheets of abrasive, wouldn't you say ?

[DWS]

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

Originally published October 21, 2013 at 8:56 PM | Page modified October 22, 2013 at 6:27 AM


Boeing readies patch for fire-damaged 787
Boeing will repair the 787 Dreamliner jet damaged in a fire at Heathrow by making a duplicate fuselage section and cutting out a piece of it to create a giant patch, in a process one expert says is “pushing the limits of what’s been done in the past.”

Goes on ...

[superq7]

Excellent post DWS :ok:

[A and C]

You are quite correct that it would involve a bit more than a bloke with a black & decker orbital sander but the discription although a bit rough and ready is a lot closer to the truth than a lot of the stuff written above.

The repair is not pushing the limits of what has been done in terms of technology............ It's just a bit bigger than other repairs and the whole world is watching and looking forward to Boeing getting it wrong............ My money is on the peanut gallery being disappointed!

[olasek]

Care to elaborate, and by the way, how do you know this is correct?
There was a PDF article on the subject. They were talking about ADL (allowable damage limits) for both aluminium and carbon fibre fuselage aircraft in typical airport ground operations, carbon fibre is much stronger and will absorb significant hit by a ground vehicle before reaching the ADL while the same collision will necessitate pulling aluminium aircraft from service and repair. Such ground collisions are more frequent than people think, airlines lose a (~) billion $$ every year, anyway there was an exact figure and it was pretty staggering.

[DWS]

Cured composites as in the 787 can be lightly sanded- BUT for any serious work as in drilling or cutting, either carbide and or diamond abrasive tools are needed.

For example regular HSS drills wear very rapidly in just a few holes- although some specialized surface treatments reduce the wear factor.

One of the problems in the normal cutting and trimming of composites was the abrasive dust involved in trimming large panels at a reasonable rate wtih high speed cutters.

In the 1980's- I designed a brazed diamond cutter " grinder " which was used to cut major composite sections of the B2

Several years earlier- another BA employee designed a carbide drill for similar material looking like a sharp pointed fluted reamer.

I mention this cuz most seem to think that carbon composite is easily cut. yes pure carbon threads can be cut- But when combined with epoxy like material and cured, its a whole different story.

Yes one can take a normal HSS drill used on aluminum and steel and drill a hole or two or three - but then the diameter of the drill will be somewhat less than when started. In a production environment - this is unacceptable.

And yes - industrial diamonds can be brazed on steel tools ..

[joy ride]

Thanks for that interesting post DWS.

I worked a fair bit with fibre-glass in the past and found sanding to be very unpleasant and there are now various health concerns about it too!

I would be very interested to know what Health and Safety precautions the repair team in this job (complete with their "sanding discs!") will have to take...will it cause the itching that Fibre-Glass does, is the dust hazardous, that sort of thing?

[G-ARZG]

'Cirque du Seattle' latest - the fin (sorry, vertical stabiliser) is off !

[BOAC]

'Cirque du Seattle' latest - the fin (sorry, vertical stabiliser) is off ! - you mean they put it back on again? Posts #976/7:confused:

[G-ARZG]

Sorree, hadn't seen those threads......been a long day !

[Grunff]

DWS: Aren't most of the holes in composite panels done by orbital drilling nowadays? Drilling CFRP panels with ordinary drills usually leaves irregular holes with chaffed edges.

Movie of the orbital drill

Edit: at least it seems that 787 panels are drilled this way: Boeing Places Subsequent Order for Orbital Drilling Equipment for 787 Dreamliner Final Assembly (http://www.aviationpros.com/press_release/10455693/boeing-places-subsequent-order-for-orbital-drilling-equipment-for-787-dreamliner-final-assembly)

[DWS]

My comments were intended to be specific to field repair. Orbital drilling if you note is a factory- machine tool- sub assembly drilling of large holes prior to or during final assembly and not likely to be used in the field.

In then field, hand drilling and reaming are the most common methods used, or in some cases, a bolted on drilling/assembly - alignment jig may be used.

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

Side note for a long time, people were worried about composite ' dust' being able to short circut electrial- electronics - base on conductivity of carbon.

so a ' cigar box ' sized clear plastic box was made, and filled with composite grindings, slivers, etc. probes were placed in the box ( like your standard ohm-meter ) and as I rcall, the box was shaken rattled, turned, etc and measurements were made of any conductivity. Answer of course was zip- nada- nothing.

What most did not realize was that for conductivity to take place with coated carbon fibers - a few hundred pieces of ' dust'- slivers would have to line upm end to end and make contact with the carbon fiber. Sort of like gettting a bunch of hot-dogs to line up end to end while surrounded by a bun.

That being said- the dust is still something to be avoided in electronics..

[Volume]

the composite engineers have won the day and we are not going to see a metalcentric repair Which dates even further back than this repair design. Composite engineers have already won in the design phase and the fuselage is no longer built from riveted (black metal) panels but the wound fibre design of the pressurized fuselage really takes benefit of the superior properties of composites. However, in an anisotropic material strengthened in only one direction (where the hoop stress dominates the laoding) may simply no longer have the bearing strength to do a metalcentric riveted repair. A scarf joint bonded repair may be the only method to repair the wound fibre barrel. So now we get a "better" composite repair than in the past of transport aircraft (in fact we get exactly that type of repair which has alwys been done to wooden aircraft and has been done for composite gliders since the 60s) which may however take a little longer and cost a little more, but will ultimately give the much better results.
To be exact the prefabrication of "spare parts" in the original production mold and splicing that into the damaged airframe by a bonded repair is more the style of wooden aircraft repair, than that of composite gliders where you often build the "spare part" in situ with a special tooling mold, so that producing and bonding is a single step.

Finally we do not only get transport aircraft made from composites, but we really get composite aircraft...

[A and C]

You are the first person on this thread who has demonstrated a practical understanding of the composite repair subject.

Some above have a grasp of the theory, but not the practice.:D

[andycba]

The latest photo shows the tent erected over the rear fuselage and the VS standing upright not too far away:

Boeing 787-860 Dreamliner (ET-AOP) Aircraft Pictures & Photos - AirTeamImages.com (http://www.airteamimages.com/boeing-787-8-dreamliner_ET-AOP_ethiopian-airlines_187546.html)

[VFD]

Thanks for the picture Andy.

I looks like as pointed out up post that providing environment for the repairs of the CRFP may be of extreme importance.
The down side is we will not get to see much of what goes on.

[seacat001]

2 months of tent time

[Monoccular]

Anyone volunteering for the test flight?

[peterhr]

Would anyone hazard a guess if this would be a permanent repair or a temporary fix to get the aircraft to one of the two assembly plants?

[Volume]

Anyone volunteering for the test flight?If I would have been involved in the repair? At any time!
I did already aerobatics on a composite glider where the wing was in 3 pieces before we repaired it. A scarf joint repair of unidirectional carbon fibre spar caps works fine. Why should a wound fibre fuselage be different ?

the VS standing upright not too far awayLet´s hope the gale forcasted for tonight will not be stronger than the VS stand... Otherwise we have the next composite repair :ouch: