Ethiopean 787 fire at Heathrow

[fenland787]

they seem to be eeping a pretty good track of eventsWell, they do but this passage from the log worries me slightly:

Another important passage is:Using insulated FRPs to repair concrete means that after a fire, it may be possible to replace the FRP system – the FRP and insulation – rather than replace the reinforced concrete member.
Given the likely temperature that the fuselage burned at, it is a testament to the strength of the CFRP outer skin that the amount of damage on the 787 was relatively limited.
...so that's the secret Boeing repair technique then, nice bit of Douglas Fir shuttering ply inside and out, a quick pour of the strongest mix Readymix can deliver and the job's a good'n?

[Speed of Sound]

Thanks green granite and ionagh.

So basically data connections then. These will eventually terminate at the pins on an IC inside the unit and if wired incorrectly will most likely 'confuse' the logic of the processor but unlikely to cause a short circuit to the battery pack.

Given the almost faultless history of this device, installation/location of this device may be where the AAIB should be concentrating their efforts.

[LeadSled]

Other than putting all ELT's in the bin, as some Aussies seem to suggest, maybe one could return the ELT to the condition of entirely isolated from all of the aircraft elecrical systems.

Folks,
This is NOT what Australian regulations are suggesting. Indeed, Australian regulations require most aircraft, on all but very short flights, (some Ultralights are exempt) to carry an ELT.

What is NOT required is a fixed ELT, for the reasons so comprehensively demonstrated by REAL WORLD results, not theoretical claims about design performance real crash loads, not "designer" crashes.

What is the point of carrying a device that has a failure rate of around 95% (100% in water) AND THIS RESULT INCLUDES LARGE AIRLINE AIRCRAFT not just small GA aircraft.

Quite a number of posters here discuss the merits of a fixed ELT in a way that suggests that the device is actually going to perform some useful function, in the event of a crash. The figures are very clear, the likelihood of any useful broadcast is extremely remote.
In the case of the recent crash at KSFO, I think I am on safe ground in saying that the fixed ELT there in the B-777 (if one was fitted) would not have broadcast a useable signal.

The failure reasons are really quite simple, in the crash sequence, in most cases, either or both the aerial cable or the external aerial are damaged. Although less common, failure of the G switch to activate have been recorded, in circumstance where the calculated G load were such that the system should have worked.

The bottom line here is quite clear, as far as any safety contribution is concerned, fixed ELT are a waste of money and add an extra potential failure mode with on-board fire as a result.

Portable ELTs, on the other hand, have a well established record of producing some quite amazing results, even under the old pre-GPS 121.5/243 COSPAR/SARSAT system, in leading searches straight to the wreck, without even a box search being necessary.

The US Civil Air Patrol, as a result of the Australian research, did a study and found, within the limits of the available data, substantially similar result -- which should surprise no one who has ever spent any time at an aircraft accident site.

None of the airline aircraft I ever flew were fitted with fixed ELT and that never stopped them flying in FAA airspace they were all fitted with with multiple portable ELT, in many cases with a water activated power source, so if it was a survivable land accident, a few blokes were going to have to pee in the plastic bag tied to the ELT for just that purpose. In a ditching, no shortage of "activating fluid".

I have actually had a commercial Li AA size and a 9V NiCad battery have a thermal runaway, in each case the manufacturer said it was impossible. Any exothermic chemical reaction which runs away caused by who knows what ? Impurities acting as an unintended catalyst ? The 9V case was interesting, the multimeter case felt warm, I removed the battery, and it continued to get hotter in my hand until I could no longer hold it so I put it on a bench and watched it finally burnt it all took about 15 minutes from the time the battery was removed from any potential short circuit. A short was unlikely, as the multimeter worked OK when another battery was fitted.

[joy ride]

All the known issues relating to the entire electrical and battery system worry me, especially as the wiring is apparently not covered in the usual type of insulation, but an ultra thin coating of Teflon. Teflon is an amazing material, but not good at resisting abrasion. A problem on the coating over aluminium wire in a damp un-insulated area of the plane near the skin could be part of the problem. I will not be surprised if the wiring eventually has to be replaced.

[Green Guard]

The Japan Airlines flight from Boston to Tokyo turned back as a "standard precautionary measure" around five hours after taking off, according to a company spokeswoman.

Pilots landed the plane safely after a maintenance warning indicated a possible fault.


around 5 hours ?

[fenland787]

So basically data connections then. These will eventually terminate at the pins on an IC inside the unit and if wired incorrectly will most likely 'confuse' the logic of the processor but unlikely to cause a short circuit to the battery pack.Yes data but not brought out into airplane wiring I would think, these will be for the 'through the skin' programming/upgrade/testing of the ELT. I think the only wires that are connected will be the four wires which I suspect may well be a CAN interface running to the RDC(s)

[Interested Passenger]

As an engineer in a completely different industry, I often refer to air crash investigations as an example of how to learn from mistakes and improve the product.

One thing that has always impressed me is that AAIB reports are written in clear English with any jargon and acronyms explained, so those not involved in the aviation industry can understand them.

It's a bit of a surprise then, that the first recommendation of the report is ....initiate action for making inert.....

This has been reported in the media as 'switching off' which is plainly the wrong interpretation.

As it is unknown if the fault was internal or external to the battery pack, would it not have been better to recommend removal of the ELT or the ELT battery?

Does 'making inert' offer other options, like encasing the battery pack in a metal box, and surrounding it with a flame suppressant material?

[fenland787]

Does 'making inert' offer other options, like encasing the battery pack in a metal box, and surrounding it with a flame suppressant materialNo, or at least not unless that modification had already been approved. I think 'make inert' means just that - remove any source of energy or other hazard

[Jetstream67]

Inert:
See Chernobyl - I think the inside of the tail section has to be encased in concrete

[Jetstream67]

Seriously I think the investigators know that wrongly calling "Lithium Battery" as the problem would be a PR disaster so they are careful to call it as an internal OR external issue. Not least as they are probably still uncertain of precisely what DID happen. Remember they spent months not finding conclusive evidence of what caused the main batteries to self destruct even with several to examine

I suspect the "Inert" wording is intended to convey "Make harmless" and thereby encourage the fullest practical set of Battery removal, Cable disconnection and removal/isolation actions

[fenland787]

See Chernobyl - I think the inside of the tail section has to be encased in concrete

Were already there - see my post #520

[Speed of Sound]

similar to the jal disaster with the botched up 747

Absolutely no comparison to the JAL flight although a rapid descent knowing that the composite roof section was burning through just in front of the tail, would worry me a bit. :)

[joy ride]

I remember watching the TV documentary about the 777, ("21st Century Jet"?) and was surprised that the plane and engines were to be fully designed on computer and not need testing.

One older engineer insisted that an engine SHOULD be tested for real on a plane and possibly, because of the presence of cameras, the then boss Mullally finally agreed to test fly an engine on an existing plane. As it banked slightly just after take-off there was a compressor stall, and it transpired that the programmers had forgotten to consider Gravity!

I have now learned that rather than strengthen ties between management and engineering, Boeing has separated the two even further by moving management to Chicago, hundreds of miles away.

This division of management from production, then issuing unrealistic demands and deadlines to the "dirty end of the company" is sadly all too common in industry and commerce these days and I feel it is a deeply flawed business model, and one which may be partly responsible for delays and problems with the 787.

We saw this so clearly in UK when companies such as the railways and Water Boards were privatised: engineering staff were rapidly chucked off the management team and side-lined. They were replaced by Business studies graduates with little or no understanding of the dirty end, who soon cut back on maintenance staff and procedures, and a string of serious and fatal accidents soon started.

[SRMman]

There is one aspect which, to my knowledge hasn't been mentioned so far.

The AAIB appear to be recommending that the ELT is removed or disabled, at least on the other 787s. But in the AF447 disaster the ELT might have allowed the aircraft to be found sooner, had the batteries lasted longer. In fact IIRC there was a recommendation in the BEA final report that ELTs be fitted with batteries of longer endurance to give searching teams more time to locate an aircraft (worst case at the bottom of the ocean).

I appreciate that it was a different aircraft type, but surely the principle is the same. I imagine that if AF447 had never happened no one would be particularly concerned whether or not the ELT was fitted or working, but of course this isn't the case now.

[fenland787]

.....But in the AF447 disaster the ELT might have allowed the aircraft to be found sooner, ....Sadly, because AF447 sank and salt water virtually prevents any RF transmission (other than VLF or ELF as used to communicate with submarines), it would not have helped.
I think the FDRs have a sonar type transducer 'pinging' away to allow location underwater but I don't thing the standard ELT does?

[p.j.m]

My interpretation of these words is that the ELT is a suspect but is far from being confirmed as the guilty party. In simple terms, the guy was there, he had a gun, but we can't find any bullets.

lightning strike.

An aluminum body would have safely grounded the energy around the skin.

the composite body allowed it through and into the ELT, setting it on fire.

[Hi_Tech]

ELT like the one fitted on the ET B787 is an option. Many airlines do not have it. In my airline none of the B777 or early Airbus have it. So it makes little difference if you remove all the units fitted to B787. Mind you there are more portable units on aircraft located in the cabin that can be manually deployed. There are also a couple of units on the door slide raft. These are cylindrical in shape. I think the ones fitted to AF flight was one of these units. These are accessible to cabin crew in case they have a run away battery.

Another question if some one can answer. We hear that the fuselage skin of this ET aircraft is not holed as most of us concluded from the video grab. This is as per the AAIB. They have mentioned severe damage to about 8 feet of the skin. The smoke was first noticed by ATC who initiated the emergency action. If all the doors were closed, how did they notice the smoke? From a vent?

[fenland787]

although a rapid descent knowing that the composite roof section was burning through just in front of the tail, would worry me a bit.Yeah, it would be a tough call - stay at 40,000' so the flames go out but pax turn blue, descend to 10,000 and the pax turn rosy pink and so do the flames...

[fenland787]

lightning strike.

An aluminum body would have safely grounded the energy around the skin.

the composite body allowed it through and into the ELT, setting it on fire. Airplane had been on the ground for eight hours, no reports of lightning anywhere near LHR

[E_S_P]

SoS Given the almost faultless history of this device, installation/location of this device may be where the AAIB should be concentrating their efforts.

I have been having the same thoughts, as I 'believe' that ET do not have the rear crew rest areas installed on the 787 at the rear, so straight away there would be differences from standard production types.

I am presuming that all of the original services that would have fed into this rest area would still be roughly in that location, albeit disconnected and (hopefully) all safely capped off and secured. The internal finishes and fittings would therefore also be nonstandard in this area. So could this combination cause some kind of detrimental enviromental change in the area where the ELT is located?

Given the number of ELT's in use its either the ulimate s*ds law that this has happened on a 787, or is there something specific about this ET version?

Is it known if there are any other operators using this configuration?

[Speed of Sound]

that this event was in the tail section behind the bulk head (prob wrong on this)

The ELT is located FORWARD of the rear pressure bulkhead. That is why they were able to tackle the fire from the rear cabin.

If this had been in flight then most likely the flight crew would get down quickly enough to avoid explosive decompression once the fire burned through to the outside. From that point on, aggressive use of the rudder and elevator would need to be avoided as the tail section would more than likely distort as a result of fire/heat damage rather than just fall off as happened with JAL 123.

[Speed of Sound]

What equipment does the cabin crew have to pull down ceiling panels to get to the location, whilst in dense (?) smoke ?

A fire axe and a portable oxygen mask but nothing to protect their heads from falling debris some of which may be burning. :(

It makes me shudder to think of some poor brave soul or souls attempting this in the knowledge that if they are not successful they would need to not only retreat but evacuate passengers forward of this position, all while strapped in for an emergency descent possibly with O2 masks deployed.

In the absence of a final report, we have to assume that this could just as easily have happened in the air.

Anyone working for Boeing PR having a moan about their bad luck needs to catch themselves on.

[Pittsextra]

What a mess:-


Boeing 787 Safety Move Splits Airline Action on Honeywell Beacon
By Robert Wall and Chris Cooper


July 19 (Bloomberg) -- Boeing Co. 787 operators are grappling with conflicting regulatory guidance after U.K. safety authorities called for the deactivation of an emergency beacon linked to a fire on a Dreamliner at Heathrow airport last week.
U.K. charter carrier Thomson Airways removed the Honeywell International Inc. locator within hours, while Japan Airlines Co. has inspected the device but faces a local legal requirement to have it on board, according to spokesman Kazunori Kidosaki. Poland’s LOT said it has made checks and the part is “fine.”
Implementing the recommendation to disable the beacon --which signals a plane’s position after a crash -- may need an airworthiness directive, according to Dominique Fouda, a spokesman for the Cologne-based European Aviation Safety Agency. The emergency locator transmitter is part of a minimum equipment list, though can be made inoperable in some conditions, he said.
“Under European regulations, ELTs can be temporarily deactivated for maintenance while the aircraft continues to fly,” added Richard Taylor, spokesman for the U.K. Civil Aviation Authority, in an e-mail. “The temporary removal can be extended for as long as necessary.”
The U.K. Air Accidents Investigation Branch yesterday urged the U.S. Federal Aviation Administration to initiate action for the deactivation of the Honeywell part after determining it was the only system in the area of the fire on an Ethiopian Airlines Enterprise 787 on July 12, adding that the event “could pose a significant concern” had it occurred with the plane airborne.
Ministry Decree
ANA Holdings Inc., the biggest 787 operator, hasn’t removed the devices because Japanese aviation law requires them aboard, said Tokyo-based spokeswoman Megumi Tezuka. If the FAA, the certification
Boeing 787 Safety Move Splits Airline Action on Honeywell Beacon

authority for the Dreamliner, ordered the removal of the components and Boeing issued a directive it would do so once Japan’s transport ministry published a decree, she said.
The FAA is reviewing the U.K. report “to determine the appropriate action,” spokesman Lynn Lunsford said yesterday.
Boeing would issue instructions to airlines about how to remove the beacon and provide assistance as needed, said Doug Alder, a spokesman for the Chicago-based company. The emergency locator can be removed quickly and won’t idle the 68-jet fleet.
LOT Polish Airlines SA, the first European carrier to get the 787, “anticipated the situation and we had already checked emergency locator beacons on our 787s before the U.K. safety board recommendation,” spokesman Robert Moren said by phone. The beacons “are fine, so we are not deactivating them.”
Visual Checks
United Continental Holdings Inc., the sole U.S. operator of the composite-plastic plane, has performed visual checks of the transmitters on its six 787s “with no findings,” Christen David, a spokeswoman for the Chicago-based company, said by e-mail.
India’s aviation safety regulator will make a decision after Air India Ltd. -- which operates seven 787s -- receives a directive from Boeing, Arun Mishra, director general of civil aviation, said in a phone interview. Rohit Nandan, the carrier’s chairman, didn’t immediately answer calls and a text message.
Indian rules also stipulate that all aircraft be fitted with an ELT device that meets FAA standards. Only aircraft used for training or research are exempt, according to the rules published on the aviation regulator’s website.
Norwegian Air Shuttle AS, which leases Dreamliners from International Air Finance Corp., said it’s in “close contact” with Boeing and civil aviation authorities. “We will of course follow all the instructions that we are given,” spokeswoman Astrid Mannion said by e-mail today.
Qatar Airways Ltd., the only Middle Eastern 787 operator, declined to comment.
The ELT beacon, using lithium-batteries, is suspect because it’s the only power source in the area of the fire, though investigators are still probing whether the device combusted or was set alight by an outside source. The incident is the first involving more than 6,000 such Honeywell devices, the AAIB said.

[meekmok]

METAR says the temperature at LHR was 25C at the time the alarm was raised. Given that heat rises, anyone want to hazard a guess at how warm it becomes just under the crown of a non-insulated fuselage skin which has been baking for the entire day?

25 degrees C is baking? The 787 underwent flight testing in Phoenix and Yuma, where it would of been 45+ every day.

[MacBoero]

METAR says the temperature at LHR was 25C at the time the alarm was raised. Given that heat rises, anyone want to hazard a guess at how warm it becomes just under the crown of a non-insulated fuselage skin which has been baking for the entire day?

And does anyone else leave their 787s outside for a similar time, in similar heat, or do they return to the cool high altitude too regularly?

According this Honeywell Rescu 406 AFN2 Brochure (http://www51.honeywell.com/aero/common/documents/myaerospacecatalog-documents/ATR_Brochures-documents/NEW_RESCU_406_AFN2.pdf), the storage temperature range of the ELT is -55 to +85 Celsius. I could well imagine it getting close to that if not higher if in direct sunlight for long enough. The upper end of the operating temperature range is specified to be lower, 55 Celsius, which I would have thought easily achievable.

Various studies on car interior temperatures, where vehicles are closed up and left in the sun show startling high temperatures. Temperatures for the air alone can be as high as 50 Celsius. Surfaces (especially dark surfaces) inside vehicles tend to be much hotter, as this is the source of heat for warming the air. Dashboards are known to reach about 100 Celsius.

If there is any comparison here, without insulation for the ELT, I would have thought the installation site unsuitable in this instance.

[nitpicker330]

Wouldn't most of the heat in a car be from direct sun through the glass windows?? Surely through a fuselage wouldn't get that hot ever???

[fenland787]

25 degrees C is baking? The 787 underwent flight testing in Phoenix and Yuma, where it would of been 45+ every dayAnd Ethiopia ain't exactly cold? "Danakil Desert is about 125 metres below sea level and the hottest region in Ethiopia where the temperature climbs up to 50 degree Celsius"

[aeromech3]

Speed of Sound & Phil:- Smoke Hoods should be available whereas a fire axe is only mandated by some authorities, if I recall correctly.
Perhaps there is a study on how carbon fibre composites dissipate heat by conduction as compared to aluminium which does it very well.

[MacBoero]

The outside temperature has some effect, but the primary source of energy would be from the sunlight. If there is no cooling breeze either, that could exacerbate the problem.

The heating effect on cars is not down to the glass. From what I have read, it would appear that the presence of glass merely affects the rate of heat rise. One compared cars, buses and vans. The van reached the same temperature as the car, it just took longer.

I also wouldn't expect the ELT to have problems the first time it is exposed to temperatures outside its specifications. It might need several excursions outside the permitted range, before problems can occur. If indeed this is what caused it in the first place.

[Speed of Sound]

Just trying to think outside the box here, but does anyone know where this aircraft was parked during its grounding earlier in the year?

If it was in one, single location, it may have been subjected to three months of regular heat/cooling cycles which may have had a detrimental effect on the folded cathodes inside one of the cells, especially if they were still switched on during the period.

Yes, I know that this happens to most aircraft on a daily basis but we need to look for something which sets this particular device apart from all the others and a regular very hot days followed by very cold nights cycle may have played some part in degrading the battery.

[island_airphoto]

Has any PLB/ELT/EPIRB ever - in the entire history of these devices - burned up and amaged an an airplane, boat or other vehicle :confused:

To me this just does not seem all that likely.

[fenland787]

I certainly wouldn't rule out temperature as a cause and I don't have numbers but I still suspect the difference in solar heating between composite and aluminum will not be vast and given the number of these in service (over 6,000?) if there was a marginal temperature effect we would have seen it by now in something else.

I'm guessing of course but suspect it will turn to be either really bad luck, some installation issue or - and my favorite - that the version of this ELT used in the 787 has been 'tweaked' in some way that has left it vulnerable.

[MurphyWasRight]

... the difference in solar heating between composite and aluminum will not be vast and given the number of these in service (over 6,000?) if there was a marginal temperature effect we would have seen it by now in something else.

But how many of the others sat baking in a dessert for 3 months?

Another difference could be what happens if a battery does go, do the aluminum instalations have a heat sink effect and or nothing flammable nearby?

It seems that something else had to have caught fire to cause the level of damage seen.

It is also possible that protective insulation (if pressent) around the ELT allowed higher temps to devlope from a battery "thermal event".

[cappt]

Grounded 787's sat out in the Houston TX sun for several months recently, no ELT fires.

[MacBoero]

But there has been talk that the Ethiopean plane is different to the standard layout in this area, i.e. the crew compartment is not fitted. This may have changed the way the ELT is mounted/contained in this aircraft. Is it now more enclosed than in other 787's, thus reducing the movement of free air around the ELT? Was any insulation omitted due the absence of the crew compartment, thus reducing or removing any protection the ELT might have normally had?

[MurphyWasRight]

Grounded 787' sat out in the Houston TX sun for several months recently, no ELT fires.

- yet -

Also not as hot and I as I recall the incident 787 was first back in service.

That said even if the "hot soak" is a factor worst case it should have caused a safe battery fail not a fire.

The real question (assuming the battery is the initiater not victim) is why a fire started.

[Speed of Sound]

Grounded 787' sat out in the Houston TX sun for several months recently, no ELT fires.

No but that doesn't mean no ELT battery damage.

If I was Honeywell I'd have that unit swapped out and have the batteries back in the lab for a thorough examination.

[Volume]

Post 502
Fancher said "a good design fix" to dehumidify the interior is being installed and will be tested when the Dreamliners resume flying.
Is the "other aircraft system in the vicinity which, with the aircraft unpowered, [...] capable of initiating a fire in the area of the heat damage" a zonal dryer ?
Those are well known for overheating...

[SLF3]

From previous posts:
- 'Rainliner'
- Wiring thinly coated with non abrasion resistant Teflon
- AAIB request to inert the ELT only applies to the 787 (ie, believe problem is 787 specific and outside the ELT)
- Non standard installation (no crew rest area) - 'unused' wiring

If the problem is moisture and / or abraded wiring leading to a short it would be very bad news for Boeing - because it potentially raises generic questions about the 787 design that are not localised to the area around the ELT.

[syseng68k]

Hi,

Having worked through this thread, cause of fire ranging from coffee
maker to elt, i'm wondering just what we are being fed here.

As far as I can see, the elt batteries are completely encased in
thick aluminium and the batteries also have inline fuses to limit the
current to a safe level in the case of a short circuit, so how could
they ever cause a fire ?.

Some of the most reliable technology, over millions of hours with no
significant event and suddenly we have a major fire in a very new a/c
with a significant history of problems and malfunction.

Sorry, but I just don't believe in such coincidences :-(...

[aeromech3]

I would assume that the mounting of the ELT battery/transmitter would be on a small rack and that only the antenna itself would be direct skin mounting, all be it with a gasket!

[Clipper7]

Haven't seen this gem posted here:


TOULOUSE: A senior Airbus executive hit out at rival Boeing's troubled Dreamliner on Friday, saying the aircraft was clearly not reliable and suggested it was rushed to market.

"It's pretty obvious that this airplane is not reliable and does not have mature systems," Airbus sales chief John Leahy told reporters at a ceremony to mark the 1,000th delivery of the company's A330 plane, to Hong Kong airline Cathay Pacific.

"You can keep it flying but it's going to cost you a lot of maintenance," Leahy said, in the first comments by Airbus management about the Dreamliner's difficulties.

"What they've got is an architecture that is not mature and that will eventually become mature. It's going to take a lot of time, a lot of money, a lot of cancelled flights. And maybe redesign quite a few systems onboard."


Airbus executive says Dreamliner 'not reliable' - The Economic Times (http://economictimes.indiatimes.com/news/international-business/airbus-executive-says-dreamliner-not-reliable/articleshow/21171740.cms)

[fenland787]

TOULOUSE: A senior Airbus executive hit out at rival Boeing's troubled Dreamliner on FridayWhat insightful and helpful comments from someone who, I presume, considers he will not be perceived as having a vested interest in knocking Boeing and it's products!

[amicus]

Speed of sound,
Codswallop, total and utter codswallop.

[amicus]

Jazz Hands,
Around 150=-160 F

[amicus]

Speed of Sound,
And where and doing what are the totally unprotected SLF in all this?

[amicus]

Aeromech3
Good comment, but what are all the SLF doing in all this other than breathing toxic carbon monoxide, cyanide and a host of 90 other toxic nasties in dense smoke via FST or just watching IFE in spite of dense FST smoke with no protection whatsoever?
The whole onboard fire fighting a critical internal FST fire just doesn't wash, sorry. And RIP to all onboard in that event.

[syseng68k]

Does seem to burn quite easily and am quite surprised that some sort of
inerting or halon extinguishant wasn't mandatory for critical areas of
this airfix a/c...

[BOAC]

In flight I suspect one might have to consider using the ocean to put it out.

[HairOfTheDog]

Can anyone explain why there have been no photos of the inside damage? There are many who could have legitimate comments that might help understand what happened with photos.

[awblain]

If it was "burning" batteries in the beacon that started the fire, and they were still involved when the fire crew arrived, then it's unlikely that anything short of cooling the batteries below their reaction temperature would stop the energy release. I understand that the failed batteries do not require external oxygen to start, or continue, to release heat. Presumably halon will quickly stop the burning of the aircraft structure in air, although unless it's also cooled, than the fuselage would presumably reignite if it stays hot and the halon drifts away.

[cappt]

I agree something here doesn't pass the smell test and is being kept quiet. Any fire investigator worth their salt can look over the aft galley and tell you if the fire started in the trash can, coffee pot or other suspected working area the crew may have utilized. This 406ELT has been used on several other aircraft for years with no history of overheating. Also the ELT battery is not of sufficient size to burn hot for more than a couple minutes if it shorted or puffed like lipo's will do when overheated. Can this ELT be activated from the cockpit like other aircraft? if so then it has a wire harness attached. I think the public and crews working this aircraft have reason to want an answer.

[mm43]

@syseng68kSorry, but I just don't believe in such coincidencesSomething doesn't add up. Okay, the AAIB have concerns surrounding the evidence they seen about the actual ignition source. I suspect the Li batteries in the ELT may or may not be to blame. Forensic examination of the battery housing should establish relatively quickly whether an external heat source was involved. Likewise if the heat generated by a battery short radiated beyond the casing etc..

Methinks the AAIB is taking a very cautious approach.

[syseng68k]

One thing to remember is that the elt batteries have only a fraction
of the capacity of the main a/c batteries, have a very different
chemistry and wouldn't suffer from the same problems in service.
Such batteries are also often current limited by design. ie: They
would be very unlikely to have enough available energy to burn
through the metal enclosure.

I had to source some long life lithium batteries for a project some
years ago. They were Lithium Thionyl Chloride chemistry, C cell sized
cell, with a high 19.5A/hours rating, but only at very low drain
current. They were rated for 125 C service, with welded stainless steel
outer case. Also found some other Lithium cells during the search that
were rated at over 200C, for applications such as deep oil well data
logging.

I find it hard to belive that these batteries could have caused the
fire, but we just have to wait and see...

[Huck]

It'd be hard to take this thing on an ETOPS leg right now....

[overstress]

Methinks the AAIB is taking a very cautious approach.

They can do little else.

If you issue an edict to ground an aircraft without knowing precisely why, how do you then release it to fly again?

[kenneth house]

that explains where the oxygen originates that can cause such a strong fire that halon cannot extinguish.

Lithium Battery Failures (http://www.mpoweruk.com/lithium_failures.htm)

[RetiredF4]

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

There are two ELt 406, the new one RESCU 406® AFN2 more than 50% lighter than the older RESCU 406® AFN.
The AFN2 has two cells, the old AFN had 5 cells. Now i'm wondering, if really already 6000 devices of the new one with only two cells are in operation or if that number is related to all 406 ELt's with two and 5 cells.

And i'm further wondering, if this 2 cell design, which saves a 4.3 lbs in weight might have some influence onthe happening.

[JustAnotherPoorSlob]

They can do little else.

If you issue an edict to ground an aircraft without knowing precisely why, how do you then release it to fly again?

The same way they did after the unexplained battery overheats :eek:

(did I say that)

[DWS]

has a few great articles on this issue

1) fire did NOT burn thru airframe- but claims aluminum section would have been weakened more and possibly failed
2) Boeing is planning on fixing - several possiblities in work patch to ferry, replace aft section, etc
Issue will be out monday- but those who have subscription can access via zinio

partial quote via ocr
....Insiders also quietly note that the
composite structure heldup well to the
fire. Compared to conventional aircraftthickness
aluminum, for which FAA
tests have shown burn-through timesof
30-60 sec. in intense fires, Boeing flame
tests exhibited longer burn-through
times for sections representative of
the 787's composite laminate skin. The
aircraft maker also points out that although
the fire was severe enough to
visibly char the exterior of the skin, the
fire did not penetrate the surface."

"This is the largest incident that I
have seen as far as damage from heat
and fire," says Paul Jonas, director of
environmental test labs and special programs
at the National Institute for Aviation
Research at Wichita State University,
"This is a significant event. It does
look like a lot of heating." He estimates
that fire temperatures may have been in
the 1,000-1,200F range to cause the type
of paint damage seen in photographs of
the scene. "Composites are pretty much
self-extinguishing. If you put flame on
and take it off, it doesn't propagate."

I will not copy more

[Nubian Major]

Interesting that halon was used (bcf) in this incident as reported in a previous post, now the 1st ba team initially entering the a/c would've had either a high pressure hosereel or a 45mm line of hose for their own protection and to extinguish the fire.

The fact that ba team(s) were used, that all takes time to implement the correct ba procedures, who made the call for bcf, the time taken for it to be deployed, looking at the pictures posted it was a good job done by heathrow airport fire service.

What hasn't been said is how long it took to extinguish the fire, maybe the fire integrity is better than thought.

[Speed of Sound]

Speed of sound,
Codswallop, total and utter codswallop.

So given the fact that none of these ELTs have been known to have started a fire onboard before, you don't think it is worth examining other ELTs which have undergone similar environmental changes to the 'incident unit', ie sat installed but unused for over three months? :confused:

Reuters:
The Ethiopian Airlines plane sat outside in the hot African sun for months, raising questions about whether that could have affected the battery in the locator beacon, said the source.

[LeadSled]

Island Airphoto,
Not all ELT have Lithium chemistry batteries, or even NiCad.
However, see my last post about my personal experience with both Li and NiCad consumer batteries having a thermal runaway and burning, the Li was an AA size, the NiCad was a 9V battery.

[tilnextime]

Fire investigation is a specialty field of its own. Based on what little I know about it from a colleague who's father was a noted specialist in the field, it can be a painstakingly long process to pinpoint the cause of some fires. While TV and movie investigators always seem to be able to reach their "Eureka!" moment in an hour or so, that is not always the case in the real world. ;)

[BOAC]

fire did NOT burn thru airframe - yet the picture at post 54 looks to me like skin penetration other than fire-axe chopping? What exactly is the definition of 'burn thru'?

[SRMman]

I would have thought "a hole".

[joy ride]

It certainly does look like the skin has burnt through to reveal internal structural members, but perhaps it is just charring and the thicker structural members have shielded adjacent skin enough to prevent charring, as if they have left shadows of themselves.
Still, I think it was Amicus who posted the info that at just 300 degrees the composite looses half its strength, and this fire sounds like it was a lot hotter than that, so my guess is that any repair will have to cover a much larger area than just the charred area.

[BOAC]

OK - Now that SRMman has sorted that for us, are we looking at a 'hole' or sooting/discolouration?

[Northern Flights]

Reuters: "Condensation, humidity and installation - that's the focal point of the investigation," the source said."

Exclusive: Probe of Boeing's 787 focuses on condensation, emergency beacon | Reuters (http://www.reuters.com/article/2013/07/19/us-boeing-dreamliner-investigation-idUSBRE96I18020130719)

[SRMman]

BOAC,
Just looking back at the AAIB Report, they say: " ...examinations of damaged areas revealed that the greatest heat damage and highest temperatures were centred on the rear fuselage close to the crown ... and corresponds to the most damaged external areas, with blackening and peeling paint and damage to the composite structure."

Ref the last part (my italics) I would say that there is no 'hole' as such; I imagine that the Report would have used expressions like 'damage including penetration' had this been the case.

[joy ride]

That report is interesting, it sounds like they are investigating condensation, humidity, corrosion (oxidation), thin insulation and isolation. I wonder if these possible contributory factors could also have contributed to other known electrical and battery problems. It would not surprise me if 787s have to undergo wiring and air conditioning modifications. This would reduce some of their economic advantages, but perhaps be what is needed to improve it.

[fenland787]

Remember the bulk of the wiring is standard copper, I believe the use of aluminum was mostly restricted to the very heavy gauge (aka gage) power stuff. The term 'isolation' caught my eye - I wonder if they mean thermal or electrical?

[SaturnV]

From the New York Times
The 787’s cabin maintains a higher humidity level than other jets to increase passenger comfort. One theory is that the humidity could have created condensation that caused a short circuit in the battery or its wiring.

Another concern is that the composite skin absorbs more heat from the sun than the aluminum on other planes. That has prompted questions about whether the battery in the transmitter could have been degraded by excessive heat from the skin.http://www.nytimes.com/2013/07/20/business/boeing-787-inquiry-zeroes-in-on-transmitters-wire.html?hpw

[Chu Chu]

A couple of thought: Thousands of similar ELTs are used every day without incident, but that doesn't rule out the possibility that this one made it off the assembly line with a defective battery or diode.

Many high-strength aluminum alloys -- for example 7075 -- are artificially aged at around 300 degrees Fahrenheit. Heating them to or above this temperature will start to affect their mechanical properties, possibly quite significantly. There are stories floating around about aluminum scuba tanks that exploded because heat lamps were used to cure a new coat of paint.

I don't know whether aluminum or composite would resist fire damage better, but it's not as simple as looking at the melting point of aluminum.

[NigelOnDraft]

I don't know whether aluminum or composite would resist fire damage better, but it's not as simple as looking at the melting point of aluminumAs you say, not a simple answer.

One area AL may have proved better here is it is a far better heat conductor. So if / while there was a relatively "small fire", the AL skin will conduct away the heat and keep the skin temperature lower.

IIRC the Boeing Tests seen elsewhere were not looking at this aspect, but a blowtorch concentrated on a small skin section. I wonder if that was as realistic as some of the "battery tests" they did?

amicus' thoughts / papers as ever discuss at length...

[India Four Two]

Ref the last part (my italics) I would say that there is no 'hole' as such; I imagine that the Report would have used expressions like 'damage including penetration' had this been the case.

If there are no "holes", what did ATC spot that made them think "fire"?

[Speed of Sound]

I wonder if these possible contributory factors could also have contributed to other known electrical and battery problems.

Condensate was said to be often found in the original battery boxes of 787 Li-Ion Mark I.

This may be one of the reasons that a hermetically sealed blue box was designed for the 'fix'. To keep combustion gases in and to keep water vapour out.

[joy ride]

Interesting.

My understanding is that Teflon, unlike some plastics (eg Nylon and Delrin) does NOT absorb any water. However, we have heard that the 787 has a very thin layer of Teflon to save weight, so I wonder if there is a possibility of flaws in this coating or wear/abrasion damage.

Powder Coated steel can rust anywhere the steel is exposed by flaws or chips in the powder coat, or if the steel is not thoroughly de-rusted before coating. The rust spreads along beneath the powder coat until it starts flaking off, to a faster and greater extent than painted or stove enameled steel.

I am wondering whether aluminium wiring, exposed anywhere to a hot and humid environment, could behave in a similar way to powder coated steel, and oxidise faster than usual and cause increasing damage to the thin Teflon coating.

[simple-simon]

This may be one of the reasons that a hermetically sealed blue box was designed for the 'fix'. To keep combustion gases in and to keep water vapour out.

More than that.... Their "solution" of putting a battery in a box, which looked like avoiding a problem they didn't understand.... included "drain holes" for the battery....

http://assets.sbnation.com/assets/2321443/Boeing-787-solution-presentation-English.pdf

Maybe Boeing had worked out what the real problem was and that's why they were so confident that it wouldn't happen again.

Perhaps they could buy some more boxes to put electrical stuff in.

[Farrell]

Doesn't matter anyway....just remove the ELT

Safety Breaking News: Japan to Let Carriers Remove 787 Emergency Beacons | Watch the video - Yahoo! Screen (http://screen.yahoo.com/safety-breaking-news-japan-let-162716325.html)

[MurphyWasRight]

If there are no "holes", what did ATC spot that made them think "fire"?


Smoke;

Tmperatues sufficient to darken the outside as seen in the photos would also release smoke from the outside surface as it was toasted.

[LASJayhawk]

ELT's are supposed to be watertight, and the Honeywell unit looks to be built like a tank (with I price tag to match I would guess :} )

There are Lithium powered 406's in the tails of King Airs all over the world, sitting on the ramp from Phoenix, to Miami. I doubt the cabin of a 787 is a worse environment.

I don't know quite what to think anymore.... :(

[NigelOnDraft]

If there are no "holes", what did ATC spot that made them think "fire"? Or:Fire fighters equipped with breathing apparatus entered the aircraft at the L2 door and encountered thick smokeIf L2 was left open (hot day)? maybe the smoke was coming from there..?

[Machaca]

Reuters reports (http://www.reuters.com/article/2013/07/20/us-boeing-dreamliner-investigation- idUSBRE96I18020130720):

...condensation in the plane and a possible pinched wire in an emergency beacon may have sparked the blaze...


...[FAA] said on Friday it will call for inspections of the beacons made by Honeywell on Boeing Co 787 jetliners, but stopped short of requiring airlines to disable or remove the devices...


The FAA said inspections should ensure wires are properly routed, and should look for pinched wires or signs of unusual moisture or heat.


...one source close to the inquiry told Reuters that investigators had found a pinched wire in the casing of the emergency locator transmitter (ELT)...


The unit that was involved in the fire had not been opened, suggesting the pinched wire originated at the Honeywell plant...


Investigators also are trying to determine if condensation on the plane seeped into the ELT, triggering a short circuit in the unit's lithium-manganese battery...


Boeing's chief 787 engineer, Mike Sinnett, told Reuters that the humidity controller on the 787, made by CTT Systems AB of Sweden, is designed to "dry out the crown" or upper fuselage, of the aircraft, and prevent moisture from accumulating. Without the system "we would wind up having that water stay in the insulation."


The AAIB also is looking at the placement of the ELT, which is bolted onto a bracket attached to the frame of the plane - exactly where condensation builds up...

[Cows getting bigger]

So the FAA have chosen to ignore another safety recommendation. Marvellous.

[tonytales]

back when the Lpckheed Jetstar came out, they had some peculiar fires involving the wiring. The installers were saving time in routing wires through clamps by using a bent set of needle nosed pliers to pull wites though. The teeth damaged the insulation leaving small pinholes.
Iworked at Lockheed New York and we viewed some films the investigators took through microscopes. of similiarly damage wires. The wires were charged to 28V DC and high humidity introduced. Under the microsope you could see, obviously in time lapse photography, a slow growth of copper crystall form between the cinductor, through the damage and work its way to the airframe which was at ground potential. The small current leak, using the moisture as a conductor was forming a thin film heater which in time grew to the point where it caused a fire. Lockheed New York rewired a number of Jetstars including some Air Force VIP aircraft.
The talk here of condensation and humidity coupled with a constant electrcal potential from a battery makes me wonder if the same mechansm might be at play in the 787.

[Machaca]

Views of section 47/48 that give an idea of insulation fitment:

http://i337.photobucket.com/albums/n385/motidog/787sec4748a_zpsf43245fa.jpg (http://s337.photobucket.com/user/motidog/media/787sec4748a_zpsf43245fa.jpg.html)


http://i337.photobucket.com/albums/n385/motidog/787sec4748b_zps4718781a.jpg (http://s337.photobucket.com/user/motidog/media/787sec4748b_zps4718781a.jpg.html)

[joy ride]

Interesting that Machaca's Reuter link was at 10.16 pm, the one in post 592 was at 6.37 pm and made no mention of pinched wires, clearly additional info led to the edited version. It is all starting to make sense.

[DWS]

Interesting- not too long ago there was an article ( in a boeing publication as I recall ) about some major cost savings being implemented on the 737 program re wiring. Thge story went like this . At various suppliers tom prewired body and cockpit assemblies, the wire bundles were temporarily held together by plastic zip ties- ties by the hundreds as it turns out. So as they go to final assembly and routing, the ties had to be cut/removed and in some areas replaced after re routing. In the process, wires were sometimes nicked by the snippers used- and thus repairs/rewiring was a small but continuing issue. Someone suggested cost savings- it took about 2 years to implement- to use some form of removeable tape for the wirebundles instead of zip ties. Virtually eliminating the cuts and damage, etc and saving a lot of time.

Wonder if the 787 implemented the same method. ?? IMHO - I doubt it. It takes a long time to coordinate with ALL the suppliers, provide the tape, etc

I'll try to find the article and post it here later


Boeing’s Renton plant bustling despite job cuts elsewhere | Business & Technology | The Seattle Times (http://seattletimes.com/html/businesstechnology/2021180748_airshowrentonjobsxml.html)


... The rate increases are achieved not only through reconfiguring the assembly lines but also through changes, suggested by employees, that can be small but have a dramatic impact.

On a tour of the assembly lines, Nishma Shrestha, lead engineer on 737 wire-installation design, said Boeing cut 15 hours of labor out of final assembly for each 737 with one change: having suppliers bundle wiring together with tape instead of plastic zip ties.

The plastic ties had required assembly mechanics to laboriously snip off the little nubs on more than 5,400 ties around the many wire bundles that go into each plane. The task was time-consuming and frequently led to mishaps with cut wires.

This apparently simple change, prompted by a study in 2010, required complex coordination and was finally implemented on all 737s in January....

[fenland787]

The talk here of condensation and humidity coupled with a constant electrcal potential from a battery makes me wonder if the same mechansm might be at play in the 787Could well be! If your box is not hermetically sealed (and most of the 'internal' electronics boxes are not) then it is required to provide drain holes to prevent condensate entrapment. This means all electronics, wiring and connectors within the box are expected to cope with a humid environment - all pcbs conformally coated and so on.

Every piece of equipment is tested for function under high humidity as part of qualification testing.

If the ELT is intended to be sealed - which it would be the case for equipment with an immersion spec - then it will not be expecting to be damp inside and I guess may not work too well if it is! The post above mentioned a 'wire entrapment' I suppose if Dr Murphy's law is working, that could have been the sole cause, wire trapped preventing case closing and sealing correctly plus insulation damage.....just a thought

[glad rag]

Every piece of equipment is tested for function under high humidity as part of qualification testing.

Would be good for Boeing to become transparent about this whole issue....

[fenland787]

Wonder if the 787 implemented the same method. ?? IMHO - I doubt it. It takes a long time to coordinate with ALL the suppliers, provide the tape, etcCan't speak for the whole thing, but the bit I worked on (very early line numbers) the trailing leads for my system were coiled and taped up with the connectors nicely done up in a protective plastic bag.

Would be good for Boeing to become transparent about this whole issue....I'm sure they will be, once all the facts are in. I'm not sure if you mean about testing, but humidity tests for electrical equipment are standard across the industry - either to DO160 or the manufacturer's in-house standards.

[joy ride]

If any wires were to become pinched, and if these wires only had a very thin layer of Teflon insulation, rather than much tougher PVC based coverings....

[zerotohero]

I have tried to troll trough all the info but cant see to find if there is any info as to why it set on fire yet?

Any news from Boeing yet or still all PPRUNE guess work?

[fenland787]

I think the assumption is that any wire that got pinched was internal to the ELT, so nothing to do with the airplane wiring. I'm puzzled by this insulation thing, it really didn't look much different from type 44 and the 230V wiring was better (thicker) insulated so no real difference from most airplane wires. I can always be proved wrong of course - it happens a lot! - but as far as this incident is concerned, the ships wiring could be a bit of a red herring.
rather than much tougher PVC based coverings....
PVC insulation is not permitted on aircraft, toxic when lit!

[Speed of Sound]

but as far as this incident is concerned, the ships wiring could be a bit of a red herring.

It always has been.

The only wiring to and from the ELT is control/data wiring which carrys miliamps of current and is not directly connected to the battery.

If any of these wires were incorrectly connected or short circuit it would cause logic problems for the ELT controller chip but it wouldn't catch on fire.

[NigelOnDraft]

Views of section 47/48 that give an idea of insulation fitment:
Quick work by Boeing fitting out a new Rear Fus 'Barrel' for the ET 787 already :ok:

[DWS]

The only wiring to and from the ELT is control/data wiring which carrys miliamps of current and is not directly connected to the battery.

If any of these wires were incorrectly connected or short circuit it would cause logic problems for the ELT controller chip but it wouldn't catch on fire

Sort of depends on what the control-data circuit wiring was shorted TO external to the ELT --for example like a 32 vdc bus bar or any power circuit or sneak circuit.

remotely drop a piece of 12 gage or smaller wire across your 12 volt car battery AFTER clearing the area . .

[palm47]

Sort of depends on what the control-data circuit wiring was shorted TO external to the ELT --for example like a 32 vdc bus bar or any power circuit or sneak circuit.

remotely drop a piece of 12 gage or smaller wire across your 12 volt car battery AFTER clearing the area . .

Why would a control-bus carry a high current? This would be a major safety issue. I cannot believe anybody would do that.

[Speed of Sound]

Sort of depends on what the control-data circuit wiring was shorted TO external to the ELT --for example like a 32 vdc bus bar or any power circuit or sneak circuit.

Very true, but this would almost certainly fry the IC which would usually lead to an open circuit somewhere along the path to ground. A dead short of the battery via a damaged IC is also likely to result in an open circuit condition. I'd also be surprised if there wasn't a fuse or diode to protect the battery itself from a short circuit condition.

An internal short circuit within the battery is a much more likely cause of a high current/high temperature condition.

[Peter H]

DWS,
Sort of depends on what the control-data circuit wiring was shorted TO external to the ELT --for example like a 32 vdc bus bar or any power circuit or sneak circuit.

Speed of Sound,
... this would almost certainly fry the IC which would usually lead to an open circuit somewhere along the path to ground. A dead short of the battery via a damaged IC
is also likely to result in an open circuit condition. I'd also be surprised if there wasn't a fuse or diode to protect the battery itself from a short circuit condition.

I'm trying to think through the implications of these interesting posts, while remembering that there are two batteries involved in the above scenarios. [One feeding the bus,
the other within the ELT.]

A hypothetical situation is that a fault in the wiring causes the plane's battery to fry the ELT's IC, raising the temperature within the ELT.

In a related scenario the plane's battery might be able to feed current into the ELT's battery via the damaged IC.

Regards, Peter

[LASJayhawk]

Bloomberg reporting a wire smashed under the beacons battery cover.

Boeing 787 Probe Said to Focus on Pinched Beacon Wire - Bloomberg (http://www.bloomberg.com/news/2013-07-20/boeing-787-probe-said-to-focus-on-pinched-beacon-wire.html?)

:ugh:

[fenland787]

I was not aware of this '32VDC bus', can anyone enlighten me?

However - and this is making the assumption that the ELT was indeed the cause and not a victim - all the 'evidence' we have to date makes the most likely cause internal to the ELT. Given the way these things should be protected, for instance if there was a failure mode that could lead to data lines 'back-feeding' the battery a diode would be fitted, likewise a non-resettable fuse in the battery pack to protect against overcurrent, it almost sounds as if the wire that got 'pinched' was within the pack itself and upstream of the protection. That would not be good but I can't see how it would have got through a design review - it's the sort of thing one focuses on big time in battery powered equipment!.

[BOAC]

As someone posted earlier, is this the first ever incident of this kind in this ELT? If so, and it was on a 787.......................what odds?

[fenland787]

As someone posted earlier, is this the first ever incident of this kind in this ELT? If so, and it was on a 787.......................what oddsYeah, what a lousy way to win a lottery!

[Speed of Sound]

As someone posted earlier, is this the first ever incident of this kind in this ELT?

The AAIB stated that there have been 'no significant events' with this unit previously.

The 'pinched' wire, if more than just rumour, puts the ball back in Honeywell's court as the ELT is a customer specification which is simply fitted by Boeing during assembly.

[glad rag]

So I take it the we are to assume an internal short circuit is the "fault"?

Then why didn't it show up during unit assembly or testing??

[However it could also be chaffing/fretting of wire to expose conductors in a longer timescale, but I find it hard to believe an ELT Tech working at a bench in the factory wouldn't spot this during assembly]

[fenland787]

Then why didn't it show up during unit assembly or testing??

[However it could also be chaffing/fretting of wire to expose conductors in a longer timescale, but I find it hard to believe an ELT Tech working at a bench in the factory wouldn't spot this during assembly] I've been there and you can bet your life those questions, and then some, are being asked right now!

However a pinched wire would not necessarily be visible from an external inspection and could well not have created a short straight away. My guess is the combination of a pinched wire followed by the temperature cycling eventually ruptured the wire insulation and if, as I speculated earlier, the fact the wire was pinched also compromised the hermetic seal and allowed the damp in, well - there you go!

[glad rag]

However a pinched wire would not necessarily be visible from an external inspection

That nothing like I posted.

[joy ride]

And assuming this is what occurred, do you think this will this event lead to tough questions about the thin insulation?

[deptrai]

As someone posted earlier, is this the first ever incident of this kind in this ELT? If so, and it was on a 787.......................what odds
Yeah, what a lousy way to win a lottery!

if this turns out to be a pinched wire in an ELT, what are the odds that it happens on the ground...(some operators plan to have the 787 flying up to 18 hours per day...)

so far I dismissed all the speculations about the 787 having more than it's fair share of teething problems, but the way this is developing, I think it's legitimate that some people are starting to ask questions about quality and testing processes, particularly those who built the plane should :oh:

[glad rag]

And not a mention of the K [TM] word.

[fenland787]

so far I dismissed all the speculations about the 787 having more than it's fair share of teething problems, but the way this is developing, I think it's legitimate that some people are starting to ask questions about quality and testing processes, particularly those who built the plane should :oh:Sorry - I must be missing something here. If - and it is still only 'if' at this stage - the problem that this thread is addressing turns out to be an internal manufacturing fault in a piece of tested, certified kit delivered by a third party who supply it to most people who build airplanes, how is that added to the 787 'teething problem' list?

I agree there are teething problems, just this isn't one of them, or did I misunderstand your post?

[TURIN]

The Main & APU batteries are not manufactured by Boeing either.
Quality control?


Posted from Pprune.org App for Android

[deptrai]

I was as just irritated by the odds of this happening in a 787, and expressed myself in a misleading way. I dont think this is necessarily Boeings responsibility, and a 787 issue, from the little we know so far. but in the end they put their name on the airplane, and if I was them, I would be asking some questions, and I am pretty sure they do.

[old dawg]

I've read through all of these posts since this thread was created.

There are three things that may, or indeed may not, be related to one another.

A mention of sparks seen well before the fire though to be from an aircon unit. If that was correct could that have affected the humidity in the area on that day?

The pinched wire discussions as a possible cause to failure of the ELT unit.

The attachment of the cables from the aircraft to the ground cart. Now it is stated that the power was disconnected and observed to be so by the flight engineer, however my question is whether the connection of those cables presented a passive electrical characteristic of some kind. e.g. a ground connection that was significantly related to a fault condition on that day. Note I've said 'fault' because normally it should not be a problem.

I'm not an avionics engineer, btw, but I have experience of EMC and have tested military gear. Some of EMC work is passive where you listen to signals emitted from a system and decide whether they are supposed to be there or not. Other tests involve introducing electrical conditions to see if anything changes.

[fenland787]

And assuming this is what occurred, do you think this will this event lead to tough questions about the thin insulation? If you mean the ship's wiring - no not at all - because it is the internal ELT wire that got pinched, or so we believe.

If you mean will Honeywell be looking at the insulation of whatever wire they used in their box? Well they may, but much more likely they will be figuring out how to re-route the wire so it can't happen again!

[glad rag]

because it is the internal ELT wire that got pinched

I would be VERY wary of reading anything into what has been "released" so far....

Boeing 787 Probe Said to Focus on Pinched Beacon Wire - Bloomberg (http://www.bloomberg.com/news/2013-07-20/boeing-787-probe-said-to-focus-on-pinched-beacon-wire.html?)

:hmm: "said the person, who isn’t authorized to speak publicly." :hmm:

[joy ride]

Thanks fenland! It is just that the reports I have heard of very thin Teflon insulation on aluminium wires make me concerned.

[fenland787]

Glad Rag,
Quote: (mine)
However a pinched wire would not necessarily be visible from an external inspection (yours)
That nothing like I posted. My apologies, I jumped ahead of myself in my reply. You asked how come it was not picked up during assembly and test, my point is that as it is thought from the reports that the outer battery cover did the pinching, there would be nothing to see during the assembly process and once it is assembled, inspection and test is all that is left to you. It is possible that inspection would not show anything and if the insulation was not compromised at that time then the unit would pass it's tests too.

[fenland787]

Thanks fenland! It is just that the reports I have heard of very thin Teflon insulation on aluminium wires make me concerned.
Joy Ride,
You are welcome, I think you will find this 'thin' insulation issue goes back a few years and is in the public domain. Quite early on the insulation thickness on the wires carrying 230VAC in the unpressurized areas was found to be on the limit for incipient discharge (corona) when airframe aging was taken into account so it was increased despite the weight penalty that was incurred.

I'm pretty sure the insulation on other wires is no different from other airplanes and most of it is copper, just the really chunky stuff moved to aluminum.

[glad rag]

Nope! there have been massive developments in the advancement of "alu" conductors and the termination technology to guarantee they match the service life of the aircraft.

[joy ride]

Understood, fenland, but the 787 does seem to be a more risky environment for various proven technologies due to its increased humidity and more easily combustible structure.

[DWS]

Understood, fenland, but the 787 does seem to be a more risky environment for various proven technologies due to its increased humidity and more easily combustible structure.

Uhh right on humidity- WRONG on more easily combustible structure . .

[Chu Chu]

I wonder how they would find moisture on something that had been through a fire. Unless some idiot had sprayed water on it. :8

I guess corrosion products that are chemically different than oxides from combustion?

[joy ride]

DWS, you're, combustible is the wrong word, damageable at a lower temperature than aluminium is probably a better way of putting it.

[olasek]

You are completely WRONG, CFRP has much higher temperature resistance than aluminium, much better temperature-strength curve. It is simply a much superior material. In terms of fire it has self-extinguishing properties.

[m.Berger]

Albeit after the fuse has punctured at 33000 feet.

[Mk 1]

Question for the gurus (sort of OT) on temp/humidity etc. As SLF I have sat in many airframes on the tarmac with the temp and humidity well above what is found at cruise (many airport in an Australian summer - particularly FNQ) Surely the fact that the dreamliner has x% increased humidity compared to older aluminium fuselages pales by comparison to the humidity all aircraft are exposed to in say Cairns with the doors open and the A/c packs switched off. obviously in this condition the circuitry is likely to be shut down, but surely when the aircraft is started the humidity inside could be 98% and fully powered up?

Surely aircraft are tested in these conditions too? Does this invalidate the x% higher humidity argument on the dreamliner?

[ZimmerFly]

The humidity at 98% on the tarmac is not the problem as the airframe will be at the same temperature and will not cause condensation. At altitude where the outside temperature is well below zero, moisture will condense on colder surfaces forming liquid water around and possibly in components that are not completely sealed and/or insulated from the colder surfaces.

[nitpicker330]

The humidity isn't that high is it??
What IS the humidity in a 787 in cruise??

[olasek]

No, humidity inside 787 is around 15% - by absolute standards still a very DRY air. But everything is relative, comparing to any other jetliner with around 4% you can call it 'humid'.

[Karel_x]

Blog on the topic:
Dreamliner 787 sweaty passengers may be causing fires | Plane Talking (http://blogs.crikey.com.au/planetalking/2013/07/20/dreamliners-high-humidity-may-pose-high-electrical-fire-risks/)

Note: If you calculate it, you get dew point -3°C (fuselage conditions 80kPa, 26°C, 15%). That means that at FL no liquid water condensation can occur but only icing on cold surfaces. It can melt lately, when a temperature of the part increases. But I am not sure whether 15% is valid for air inlet, average humidity in the cabin or for outgoing air.

BTW I believe that you can hardly feel difference between 5 and 15 percent of humidity.

[Speed of Sound]

BTW I believe that you can hardly feel difference between 5 and 15 percent of humidity.

I suspect you are right although many passengers have sworn there is a noticeable improvement in 'cabin air comfort' on the 787.

Placebo, anyone? ;)

[Lonewolf_50]

olasek
You are completely WRONG, CFRP has much higher temperature resistance than aluminium, much better temperature-strength curve. It is simply a much superior material. In terms of fire it has self-extinguishing properties.
Can you expand a bit on the bolded part? I am not good at advanced chemistry, nor in some of the exotic materials used nowadays, so I will ask:

once something starts burning, how does it stop itself from burning? :confused:

[Burnie5204]

One way of being 'self extinguishing' is by using/manufacturing a material whose combustion temperature is higher than the temperature of the flame created when it burns.

[olandese_volante]

once something starts burning, how does it stop itself from burning?
Certain materials are said to be self-extinguishing when they will not sustain combustion by themselves, once an external source of flame has been removed.

An example would be a material commonly used for printed circuit boards, known as FR-4, which basically is glass reinforced epoxy containing certain additives, usually bromine-based (and environmentally slightly nasty).

See also: Flame Retardant (WP) (https://en.wikipedia.org/wiki/Flame_retardant) for information on the exact mechanisms involved.

[Karel_x]

Placebo, anyone?
The speed of evaporation depends much more on a velocity of air flow. If I direct an air outlet to my head, my skin and my eyes could be dried several times more (e.g. 300%) whilst decrease of evaporation between old and new a/c (5 vs. 15%RH) is about 5%.

There can also exist some kind of psychosomatic effects in 787. If you feel calm and relaxing (thanks to advertising) your breathing is light and your respiratory system is dried only little. When you are feeling uncomforted and upset, or you worry about it, both heart action and breathing is much higher and your respiratory system is dried more.

[Coagie]

once something starts burning, how does it stop itself from burning? http://images.ibsrv.net/ibsrv/res/src:www.pprune.org/get/images/smilies/confused.gif"Self-extinguishing" material stops burning, because it's already burnt part doesn't shed or become porous, blocking oxygen from the non-burnt part underneath it, so the fire is smothered. Think of a fire in your fireplace. When it's about to go out, you take the poker, and knock the burnt part of the wood off, exposing the unburnt part to oxygen, and the fire increases. In self-extinguishing material, the burnt material tends to stay on and block the oxygen, and, there's no one with a poker, knocking the burnt part off.

[daikilo]

That is one explanation and the other, closer to the sponsored research, is that, like a candle, with heat applied the material gives of vapours which can burn. Remove the heat source and everything cools to being inert again.

The issue in the 787 case is to detremine what was the initial heat source. If it was the ELT itself then it would be a first. If it was something in that area which then caused the ELT to generate enough heat, maybe. But what if the heat source managed to bring e.g. CFRP material up to the temperature where it and/or other local materials gave off combustible gasses which then sustained the burning and then caused the disruption to the ELT?

[DWS]

Boeing 787 Dreamliner: FAA to issue 'airworthiness directive' in wake of fire | Business | guardian.co.uk (http://www.guardian.co.uk/business/2013/jul/22/boeing-787-dreamliner-faa-airworthiness-directive)

Boeing 787 Dreamliner: FAA to issue 'airworthiness directive' in wake of fire

Regulator to order mandatory inspections of 787's emergency beacons just two months after lithium-ion battery problems

..
The Federal Aviation Authority was due to order mandatory inspections of the emergency beacons aboard Boeing (http://www.guardian.co.uk/business/boeing)'s ill-fated 787 Dreamliner as early as Monday after a fire broke out aboard one of the planes in London.
The FAA "airworthiness directive" comes just two months after the 787 was certified to fly again following a global grounding triggered by problems with its lithium-ion battery system.
A fire aboard an Ethiopian Airways jet at London's Heathrow airport earlier this month forced the closure of both runways for more than an hour.
The UK's Air Accidents Investigation Branch (AAIB) concluded that the fire started near the aircraft's emergency locator transmitter – a distress beacon used to help rescuers find a plane if, for example, it is forced to land on water or in polar regions. The focus of attention appears to be whether a pinched wire under the battery cover triggered a short circuit.
The FAA spent the weekend telling other aviation safety regulators around the world of its concerns. It is expected to formally issue the directive early this week, possibly as early as Monday.
The beacons, made by Honeywell, are powered by a lithium manganese battery, which could have suffered a short circuit. Last week the FAA said its inspections would call for operators to check "proper wire routing and any signs of wire damage or pinching, as well as inspect the battery compartment for unusual signs of heating or moisture."
Robert Mann, an aviation expert at consultant RW Mann, said it was unclear whether the latest issue was caused by installation, quality control issues or design issues specifically related to the 787. Honeywell had issues with its emergency locators in 2009 that led to the beacons failing to send out signals. But Mann said the issue could also be specific to the Dreamliner.
The 787 is the world's most technologically advanced passenger jet. Its use of lightweight materials means its uses 20% less fuel than its peers. Aluminum wiring and Teflon coating are used to save weight. "We got rid of aluminum wiring in the US in the 1980s because of the tendency of aluminum oxide to cause problems," said Mann. "And there have been reports of fragility with Teflon insulation." ...

[Ian W]

Quote:
This may be one of the reasons that a hermetically sealed blue box was designed for the 'fix'. To keep combustion gases in and to keep water vapour out.
More than that.... Their "solution" of putting a battery in a box, which looked like avoiding a problem they didn't understand.... included "drain holes" for the battery....

http://assets.sbnation.com/assets/23...on-English.pdf (http://assets.sbnation.com/assets/2321443/Boeing-787-solution-presentation-English.pdf)

Maybe Boeing had worked out what the real problem was and that's why they were so confident that it wouldn't happen again.

Perhaps they could buy some more boxes to put electrical stuff in.

The battery box was to meet the new RTCA standard for LiIon batteries, the new Cessna Citation has a similar box and had to have similar tests.

[simple-simon]

The battery box was to meet the new RTCA standard for LiIon batteries

Could be. I think it's a great solution to the problem.... Here's the scenario:

1) Plane flies high in the sky.... Airframe gets very cold....
2) Airframe made of composites has much lower thermal conductivity than aluminium. Nett result... airframe takes longer to get cold on the way up.... once cold... takes longer to warm up on the way down...
3) Plane lands, doors open, passengers get off. Cabin fills with air far more humid that the 15% talked about on this thread.
4) The moist air, inside the aircraft, getting close to the airframe, forms condensation.... Since the airframe is cooler than we see in aluminium airframes.... we see more condensation....
5) Water and electrical circuits don't go too well together...
6) Issues that previously were unlikely to occur, become more likely, in the more moist environment.

So by putting the battery in a sealed box.... nicely ensures that the condensation doesn't get to the battery... It wasn't poorly made batteries, or overcharging.... it was a short caused by the battery being covered in condensation.... Oh and meant to say.... the technology behind the battery wasn't the problem and this is why it didn't make sense to change to conventional batteries...

I could be wrong of course, just a theory.

[Volume]

Airframe made of composites has much lower thermal conductivity than aluminium. Nett result... airframe takes longer to get cold on the way up.... once cold... takes longer to warm up on the way down...
3) Plane lands, doors open, passengers get off. Cabin fills with air far more humid that the 15% talked about on this thread.
4) The moist air, inside the aircraft, getting close to the airframe, forms condensation.... Since the airframe is cooler than we see in aluminium airframes.... we see more condensation....Not necessarily. Airframe made of composites has much lower thermal capacity as well, so less "coldness" stored in the airframe.
GA experience: Aluminium airframes parked outside have water accumulation inside in the morning, GFRP airframes parked outside do not (or significantly less). Might be an issue of the sandwich construction as well, so for a monolithic dreamliner it may be different again.

[HDRW]

Here's a thought: The new battery-box in the 787 is vented to atmosphere, so at altitude it's going to be at low pressure, and maybe quite cold (I don't know if the box is insulated, or how much of the aircraft's warmth will penetrate). On descent the box will "breathe in" the outside air, and if it's humid, will the cold battery have a tendency for condensation to form on it? I also wonder if they had to strengthen the battery's case to withstand the low pressure around it?

[kenneth house]

@ simple-simon post #666

but could you condense it down to a simple version?


Looking at the pattern of the charred area it appears that the longitudinal struts (also a composite structure?) shielded the skin or acted as a heat-sink to pull heat out of the surface.

i wonder if the coeff of thermal expansion (CTE) of the composite is much greater than aluminum and may allow more aircraft growth and contraction such that wire chaffing might occur?

[fenland787]

The new battery-box in the 787 is vented to atmosphere, so at altitude it's going to be at low pressure,You are presuming no overpressure valve or rupture disk in the vent? I don't know either way but would have assumed the opposite. I cant believe those cells would like to spend most of their flying lives at unpressurised Ps & Ts?

[Speed of Sound]

The new battery-box in the 787 is vented to atmosphere

It's not.

It is only vented to atmosphere once the pressure inside the box ruptures a disc in the vent. This protection is set to rupture at a much higher pressure than the differential at normal altitude.

[Karel_x]

i wonder if the coeff of thermal expansion (CTE) of the composite is much greater than aluminium and may allow more aircraft growth and contraction such that wire chaffing might occur?

Maybe twice as much as aluminium, I am not sure about type of resin:

Aluminium 22.2 . 10-6 m/mK
Epoxy, castings resins & compounds, unfilled 55 . 10-6 m/mK

That means ca 1 mm per 1°C for hole long fuselage. Fuselage is getting shorter at FL so wires are not tighten but some movement surely exists.

2 simple-simon: Interesting hypothesis...

[LASJayhawk]

I think you are all reading way too much into this. If they shorted one of the battery leads under the cover, it would only take time to make an ELT immolate.

[awblain]

CFRP typically has a very low thermal expansion, at most about 6 times less than Aluminum at 300K. If designed right, it can have almost zero. Many sophisticated structures (that are not limited by weight) use it, despite its cost, to take advantage of this property. If there's any chafing it would probably be because the metal wiring changes size while the composite structure does not.

[olasek]

Maybe twice as much as aluminium,
Your data is wrong.
Thermal coefficient of expansion of CFRP is about 5 times smaller than aluminium. (2.3 e-5 per degC for Al and 0.5 e-5 per degC for CFRP).

[fenland787]

Maybe twice as much as aluminium, I am not sure about type of resin:

Aluminium 22.2 . 10-6 m/mK
Epoxy, castings resins & compounds, unfilled 55 . 10-6 m/mKIs 'unfilled resin' the right number to use? I thought carbon composite is much better than that - because of the fiber, optical tables made of it have a COE typically 1/10th that of steel for instance, so I thought the number is lower than Al, not higher.

The hugely dominant effect is flexure in flight, have you seen the wings on takeoff?

[Cathay Boy]

If condensation is the cause of battery fires, and Boeing "knew it", it can be easily tested in test scenario. Are you suggesting conspiracy that Boeing is trying to hide 787's condensation issue as it effects not just the battery but the entire electrical systems on the 787s (which is a lot), and may even force Boeing to redesign the entire plane?

[olasek]

If condensation is the cause of battery fires,
There are a lot of "ifs" in your statement. I could bet my home that condensation did not play any role here. But even if it did you wouldn't have to redesign electricity - you simply turn down humidity to much lower levels. There is nothing in the design of A/C-ventilation in 787 that says you MUST have higher humidity.

[syseng68k]

In light of the discussion re: composites and aluminium alloy in the
presence of fire, I wonder if someone (amicus ?) could comment:

In a composite structure, serious fire at one side of the sheet could
cause serious delamination and strength reduction before it burnt through,
due to the insulating properties of the composite materials. Aluminium
alloy, on the other hand, even though thinner, conducts heat very well
and has a high melting temperature.

Seems to me that, in the same way that an aluminium pan doesn't melt when
exposed to a gas flame, so long as it doesn't boil dry, aluminium should
be safer, especially at 30k feet, lots of air cooling the panel and air
temperature of say, -50 C ?...

[lomapaseo]

There is nothing in the design of A/C-ventilation in 787 that says you MUST have higher humidity.

Wasn't that a selling point of this aircraft to the passengers?

[olasek]

Wasn't that a selling point of this aircraft to the passengers?
Yes, it was ONE OF selling points. It doesn't mean that higher humidity is mandatory.

[amicus]

syseng68k,
Thank you for your kind request and I trust that I can make a sensible and accurate response to your good self regarding conduction and insulative properties of both aluminum alloys and CFRP, whilst simultaneously attempting to correct some misunderstanding by others and make some suitable, accurate and helpful remarks regarding relevant differentials of Coefficients of Thermal Expansion (CTE) and other composite properties.
First, please let me address those who claim that CFRP quote "chars'" and that it thus self extinguishing. Sadly this is not the case for epoxies, I again repeat to those that will hear, the fact that all epoxies have been banned from aircraft interiors for around the last 30 ears and for excellent reasons, and it was not merely the flammability and combustability of such epoxies, but primarily the Fire, Smoke and Toxicity (FST) emisions that occur.
And, yes, a char develops. but only as a result of the epoxy having first burned with deadly initial combustion, flaming, smoking and emitting copious FST hazardous products in the process. Incidentally, that is what we used to employ way back when to make carbon/carbon, but that process was a controlled, pressurised and in an enclosed chamber. We used phenolics, primarily, as they have a greater carbon yield than evil epoxies. However, even that process , required over seven re-denisification and burn cycles to come close to the desired theoretical density of carbon/carbon.
The epoxy itself,and I have both performed or witnessed many 100's or 1000's of OSU ( Ohio State University) tests as developed back in the 60's re testing flammability of epoxy interiors, seat cushions, fittings,overhead bins and the like which became a semi-standard interior burn test over the decades to prove this point. However, and it's a very large however, the OSU test was designed around a mere burning cigarette or lighted pipe scenario, with a 50 watts level, far from 28V electrical fires and shorts and fuel fed fires in a survivable crash which requires 200-250 watts per square metre and their ilk. This point is cited and detailed in my paper as some have read on this board.
But the charring of epoxies does not, repeat NOT, prevent burn-through which is why the FAA and Boeing developed a whole new set of high wattage burners to try and adequately simulate and test for burning fuel fires and resulted in the FAA, over Boeing's weeping, wailing and lobbying to stipulate that the lower half, and, most regrettably only the lower half, of the 787 fuselage be expensively and heavily insulated with a special anti-burn through insulation to allow a five minute escape window in case of a wheels-up or off runway survivable crash.
However, and here is yet another huge however, the FAA and Boeing still had to assume and design the burn-through test only for a totally intact, all doors closed, no slides deployed no doors opened and no fuselage fractures, given the FST loaded epoxies employed by Boeing. Clearly, in most survivable crashes, this is not the case and I supplied the FAA, Boeing and Airbus with over 150 such commercial airline survivable crashes since the 1980's as my paper cites. All were survivable crashes with fuselage fractures and/or opened doors. The simple and clear fact is that Boeing and the Northwest FAA Office did not have a prayer of certificating the 787 unless an intact and closed fuselage was assumed as a basis for fire testing in the realm of 200-250 watts as is the case in fuel fed fires. Specifically, EADS also presented totally independent, but similar findings re the A350 two or three years ago.
Now , allow me to wander back, please, to the char that some have cited. All such claims are nonsensical, tendentious and worthless twaddle, to put it mildly. A "CHARRED" CFRP is no longer CFRP, it is merely a residue of strands of free CF, either woven or UD, but it is no longer a composite structure capable of meeting any design loads or criteria at all. So 'char' is a silly diversionary tactic , pure and simple,with the emphasis on simple to my mind and has nothing whatsoever to do with any structural load carrying ability or any chance to sustain any pressurisation loads. I hope that I see no more silly inputs re"char"and would note that the non-structural and useless char would be blown away by the 500 plus mph airflow.
Next, please let me outline briefly the relative CTE's regarding Aluminum and CFRP and epoxies. Let me work in old fashioned degrees F units, please. just to humour me.
Typically an aerospace alloy will have a CTE of 12-13 x10 to minus 6 inches/inch /degree F, and epoxy will have (in its pristine state epoxy only state it will have 22-23 in same units). But not in a CFRP composite whose CTE is controlled by the CF with a modulus of 40 MSI vs epoxy at a mere MSI of less than 1.
MSI matters, just as loads follow stiffness (same degree F units,of course). This differential generates internal stresses in the composite, but they are usually of a second order concern, but some of we composite folks like lower cure temperatures to minimise such internal and residual autoclave induced curing stresses. For CF itself, as a unidirectional material, it has an expansion close to zero (typically 1 or less re CTE units quoted, which is why it is employed for space mirrors encountering wide night/day temperature swings. This is also why INVAR is typically used as Boeing and other aerospace companies as tooling material to minimise problems involving thermal distortions. Boeing and others typically employ a quasi-isotropic layup, with, I note, emphasis on the quasi, as there are some significant differences between a true isotropic material and a quasi-isotropic material. Such CFRP structures typically have CTE's in F units of around 3-3.5. I hope that this clarifies and settles the CTE issues previously discussed in this thread.
And, prior to getting to my final points regarding thermal insulative and conductivity properties of aluminum alloys and CFRP's as I promised that the outset of this overly long input, let me give some relevant metallic vs. CFRP cross plied properties for others to mull over. CF is widely touted, and oft over-touted, regarding its strength, but let us be very careful here. A decent CFRP will have a tensile composite strength, if a UD material at 60 % fiber volume, of around 280- 320 KSI,( note, this is the sigma 1-1 equivalent to metallics).
A quasi-isotropic composite in the same CFRP will have a tensile value of around 90-120 KSI. Now, let us look a couple of weaknesses without boring you all with the hygroscopic nature of that nasty epoxy.
The shear strength of metallics is typically 60% of the tensile, so for a decent steel, for example, say in the 240 ksi range we will have a shear strength of around 145 KSI. Now look at composites and up pops that nasty epoxy again. Whereas Steel will have a SBS or ILSS strength of 144 KSI, a quasi-isotropic composite will have an ILSS of 8-10 KSI static on a good day and, if we allow for fatigue et al, we are down in the 4 KSI area. And finally another key nasty is the short transverse tensile strength ( equivalent to metallic sigma 3-3), which is entirely epoxy dependent and no CF failure is involved, there we find on a good day around 3-4 KSI with fatigue knocking that down to around 1-1.5 KSI which is close enough to zero in this composite engineer's mind and no tensile Sigma3-3 asallowed by an decent and competent comosites engineer.
Achilles only had one heel , lucky for him, but for we in composite design and analysis,there are plenty of other heels to fret about. This is not an anti-composite rant of any ilk, but rather to emphasise why composites need to be analysed far differently and much more closely than most metallics Further, large scale repairs become much more demanding and possibly questionable in contrast to the blithe assertions of some posters on this board. And, as a final point,why has nobody in the composites community,after a full half a century of designing and using CFRP, has yet developed "A'" basis allowables for composites as is so common for metallics? Why and we are still operating with "B" basis allowables with significantly lower probabilityand confidence levels?
Now, belatedly back to the original question that I was requested to respond to and, perforce, my final zinger for today for those seeking to minimise the magnitude of the 787's inherent epoxy based FST et al difficulties.
Yes,CFRP is indeed an thermal insulator compared with aluminum alloys, but also exhibits significant differences depending upon fiber orientation and layup. This, in turn, leads fires, heat and the like to be concentrated in one local area rather than with aluminum's high thermal conductivity, which lowers and significantly lowers and dampens peak temperatures in event of fires from whatever the source.
I trust that this helps the ongoing discussion.
And now I promised you a zinger and here it is; for all proclaiming and advocating the efficacy and safety and non -flammable nature of CFRP, let me issue this very simple challenge.Go out and buy (or borrow from your missus or similar)some aluminum frying pan. Then please cook something requiring 600-650 degrees F on a gas stove. Next, just to humour me, reproduce that same test, but this time first build a CFRP frying pan of similar size and construction and cook the same food with 600-650 degrees F gas cooker. There is only one stipulation, as I do not want you or your loved ones or pets to suffer or die in such a foolish attempt, please do this test of your cooking skills on an outdoor barbicue well away from all humans and pets and let me know the results. In closing we all know, I would hope, why there are no CFRP cooking utensils on the market and,just as a clue,it is zero to do with cost and all the do with flammability and FST.
Any takers, 787 defenders and "it only chars and is better than aluminum" folks, please put your frying pan where your mouth is?
Cheers and apologise for such a long post, but I hope is deemed of some value.

[Walnut]

Amicus's post is very interesting, I note the Asiana 777 crash at SFO burnt through its upper fuselage, but not the lower, I wonder whether that a/c (777) has any upper insulation.? If composites burn more readily then maybe 787's should?

[Innaflap]

Maybe the only way to answer these questions on flamability is to take a number of aircraft from the world's 2 principal manufacturers and ignite them simultaneously to see which produces the most toxic smoke and which burns longest.

Airbus - A320 and A330

Boeing - 777 and 787

[SRMman]

You've picked the wrong Airbus example, the A330 is mainly metallic. I guess you meant the A350 which is around 50% composite.

[Pittsextra]

Boeing release their Q2 earnings today and have the earnings call at 1530 UK time. Why not call investor relations and ask the question of the executives on the call today?

[joy ride]

Fantastic post Amicus, thanks. I will have to read it again to understand it all better, but it does raise serious questions.

[Pittsextra]

Amicus - I've bee reading this:- (http://stuff.mit.edu/afs/athena.mit.edu/course/3/3.91/OldFiles/www/slides/J_Composite_Materials2002v36p2713.pdf)

Any studies on this from an aerospace perspective?

[Volume]

i wonder if the coeff of thermal expansion (CTE) of the composite is much greater than aluminium and may allow more aircraft growth and contractionCoeff of thermal expansion is negative for carbon fibre. Coeff of thermal expansion of the CFRP depends on the layup, it might be negative in one direction and positive in the other one, it might be very close to zero in a balanced layup of fibres in a matrix.
However, a wound fibre fuselage barrel may increase its diameter (fibre direction) in the cold air at altitude, while increasing additionally due to the pressurisation loop stress, so overall diameter increase may be more than the one of an aluminum fuselage. But I seriously doubt that this is a challange for the wiring, it should be designed to withstand airframe deformation.

And, prior to getting to my final points regarding thermal insulative and conductivity properties of aluminum alloys and CFRP's as I promised that the outset of this overly long input, let me give some relevant metallic vs. CFRP cross plied properties for others to mull over. CF is widely touted, and oft over-touted, regarding its strength, but let us be very careful here. A decent CFRP will have a tensile composite strength, if a UD material at 60 % fiber volume, of around 280- 320 KSI,( note that is the sigma 1-1 equivalent to metallics).
A quasi-isotropic composite in the same CFRP will have a tensile value of around 90-120 KSI. Now, let us look a couple of weaknesses without boring you all with the hygroscopic nature of that nasty epoxy.
The shear strength of metallics is typically 60% of the tensile, so for a decent steel, for example, say in the 240 ksi range we will have a shear strength of around 145 KSI. Now look at composites and up pops that nasty epoxy again. Whereas Steel will have a SBS or ILSS strength of 144 KSI, a quasi-isotropic composite will have an ILSS of 8-10 KSI static on a good day and, if we allow for fatigue et al, we are down in the 4 ksi area. And finally another key nasty is the short transverse tensile strength ( equivalent to metallic sigma 3-3), which is entirely epoxy dependent and no CF failure is involved, there we find on a good day around 3-4 KSI with fatigue knocking that down to around 1-1.5 kSI wihich is close enough to zero in this composite engineer's mind.This is the reason why a composite aircraft structures design should look totally different from a metallic one. Both material types have their superior strengths and their enormous weaknesses. The key to composite deign is to understand this and to design accordingly. For example in a pressurized fuselage skin the loading is almost entirely in-plane, so sigma 3-3 or ILSS is "close enough to zero" to perfectly meet the load carrying capability of a CFRP layup. On the other hand any item loaded in all three dimensions (e.g. a landing gear main fitting) will never be seriously proposed to be made from CFRP. As stated before, composites are more or less artificial wood, the structures design should be fairly the same (except that nails my not be a good idea...). Unfortunately in the large aeroplane world (maunfacturers, operators, authorities) there is little knowledge of wooden aeroplanes, hence there is an awful lot of misconception going on.
Having designed, build, tested to destruction, certified and repaired a CFRP glider wing, I often wonder what those "metal guys" are trying to build from CFRP...

[cockney steve]

Shirley I'm not the only reader of this thread to have ever burnt a fibreglass moulding on a bonfire?

A bath, a caravan roof , a dinghy and part of a vehicle body all exhibit the same characteristics,as regards burning.

Like any other plastics, lots of thick, black smoke is emitted and the flame front spreads rapidly across the surface, accompanied by a typical "sizzling" as the plastic in the heat-path of the flame-front bursts into tiny, popping bubbles which rapidly burst, releasing their inflammable gases and thus progressing the flame-front.


The plastic (resin) burns away completely, leaving a perfect armature of the original moulding....It is, however, more fragile than an eggshell and will often collapse under it's own weight.
Glass fibre /Carbon-fibre/ Kevlar....it doesn't really matter............................of itself, the fibre is soft and pliable, the resin impregnation gives the strength and rigidity...burn the resin and you've little more than a starched textile.

Many a fibreglass/Composite boat has been burnt to the waterline, I would not like to be in a burning Composite aircraft.
I'd take my chance in something like a Cirrus, but not in a commercial airliner with the mass of attendant electricals, water heaters,pax attempting a crafty puff etc. no, IMO there is a good case for composites in aircraft, but the Pax deserve a more robust survival-cell.
Self-extinguishing resins are readily available,their suitability in this application is another issue and if the flames or loss of strength don't get you, the fumes surely will!
Thanks, Amicus for your highly technical treatise. It leads one to believe the public have been hoodwinked by the vested interests.
The "screamliner" *could* have had a huge economic advantage over a conventional aircraft, albeit with a compromised level of safety.

We all take our chances weighing risk and gain in our daily lives.
Generation 2 of the "Plastic -Fantastics" may well bring the much-vaunted benefits, but I fear the 787 was too many steps too far, too soon.

[DWS]

787 fire investigation looks at pinched battery wiring | Business & Technology | The Seattle Times (http://seattletimes.com/html/businesstechnology/2021456975_787firesourcexml.html)

787 fire investigation looks at pinched battery wiring

Investigators believe the July 12 fire on a 787 Dreamliner at Heathrow was likely caused by incorrect installation of a battery that pinched some wires and caused a short circuit.

Boeing and government investigators now believe the July 12 fire on a 787 Dreamliner at Heathrow Airport in London was likely caused by the incorrect installation of a small lithium ion battery inside an electronic device.
If that’s confirmed, the fire was due to human error, not a Boeing design flaw.
U.K. investigators who examined the device, called an Emergency Locator Transmitter (ELT) and made by Honeywell, found that the internal wires connecting the battery to the ELT had been trapped and pinched when the cover was reattached as the batteries were inserted, according to two sources with knowledge of the matter, one inside Boeing and one outside.
In photos of what was left of the device, “You can clearly see the two wires crossed over each other. It’s quite evident the wires show evidence of being smashed,” one source said.
Installing the battery package entails unscrewing the cover of the relatively small device, dropping the battery pack of five cells into a slot and connecting the two wires that protrude from the battery pack to a receptacle in the ELT.


goes on ...


The two sources suggested that Honeywell might have replaced the batteries at some stage before delivery of the jet because the devices sat on the shelf during the years-long 787 program delays.
If this were correct, it could explain why the accident happened to the 787 in particular.
Investigators are also looking at whether overheating of the batteries as they sat parked in the sun during the four-month grounding of the 787 fleet earlier this year could have led to internal damage that contributed to the failure.
There’s no evidence of moisture damaging the batteries, which had been another theory put forward in the press.

[Coagie]

"Self-extinguishing" certainly shouldn't be confused with "fire proof". Self extinguishing materials may stop the spread of fire, but certainly should be replaced at first opportunity. Also, isn't a 777 an aluminum bird? Seems like some think it's a composite.

[David Bass]

I can't help but think that equipment designed such that it allows the wires to be crushed when reassembled suffers more from "design flaw" than "human error". There are billions of devices out there that manage perfectly well to have replaceable batteries that cannot suffer from this problem. SOme of them are probably in safety critical applications, too.

Regardless, Boeing can point the finger at Honeywell if blaming the maintainer doesn't stick.

[funfly]

I know I posted this before but relevant to the current comments, this was my all glass fibre aircraft following a crash land (after I sold it luckily)

http://www.funfly.co.uk/images/KISS.jpg

FF

[HeavyMetallist]

Regardless, Boeing can point the finger at Honeywell if blaming the maintainer doesn't stick.
If analysis shows that the damage to the composite fuselage is as structurally significant as it looks from its external appearance, then Boeing would still have some difficult questions to answer; it wouldn't be acceptable for the integrity of the aircraft to be compromised by a single LRU internal short circuit.

[Speed of Sound]

I can't help but think that equipment designed such that it allows the wires to be crushed when reassembled suffers more from "design flaw" than "human error".

Not necessarily.

From an electronic design point of view, some cables are longer than they need to be so that parts can be removed without having to unplug/disconnect one thing from another.

Making a cable short enough to not become trapped in a reassembled casing, can mean having to disconnect it to remove another part of the circuit which may lead to other problems or puts tension on the wire which could lead to a break.

Much better to have a looser wire which allows greater accessibility and an SOP which involves making sure the wire isn't trapped when the device is manufactured.

Remember these beacons have a battery life of 10 years and once installed should need very little or no attention.

[LiveryMan]

I know I posted this before but relevant to the current comments, this was my all glass fibre aircraft following a crash land (after I sold it luckily)
What point are you making with this picture?
Are you saying CFRP planes burn more or burn the same and Aluminium alloy aircraft?

I've seen plenty burn out hulks of more traditionally constructed aircraft, large and small.

[funfly]

Sorry mate, not making a point. Just though it might be interesting to see what a burnt out glass fibre aircraft hull looked like as there had been a lot of comment about glass fibre burning.

[slacktide]

I see your burnt-out fiberglass light-sport aircraft and raise you three burnt-out aluminum Cessnas and Pipers.

http://www.fiddlersgreen.net/aircraft/Cessna-152/IMAGES/cessna-152-crash-fire.jpg

http://wilko.files.wordpress.com/2010/01/airplane-fire.jpg

http://aviation-safety.net/photodata/22676_4a4bd96da1552Image4.jpg

Of course none of these fires have any relevance to the case at hand, as they are uncertified aircraft (your case) and CAR3 / FAR 23 certified aircraft (my case) which have no requirement to be tested or certified to prevent burn through as FAR 25 aircraft have to be.

This entire argument regarding the autoignition temperature of aluminum and CFRP is bogus from the beginning as it ignores thermal mass. Place a 2" thick paper textbook and an empty aluminum beer can in front of a lit propane torch, and let me know which one burns through first.

[Smilin_Ed]

Shirley I'm not the only reader of this thread to have ever burnt a fibreglass moulding on a bonfire?

Who is "Shirley"?

[jolihokistix]

Re this quote in the Seattle Times article above: "It’s quite evident the wires show evidence of being smashed,” one source said.

How do you 'smash' a wire? With a brick or a rock or a hammer? Is this just bad English, or a typo? Are we supposed to 'correct' the word into another such as 'mash' or 'crush' or 'pinch' or anything that might make some sense, or is that taking liberties and are we expected to take this word at face value? :ugh:

[MurphyWasRight]

Shirley???????????


Shirley I'm not the only reader of this thread to have ever burnt a fibreglass moulding on a bonfire?


Who is "Shirley"?


And stop calling me Shirley....

Sorry could not resist, see the "airplane" movie series for the reference if new to you.

[syseng68k]

Amicus,

Thanks for the lengthy explanation, though not being a materials engineer,
am having a bit of trouble decoding the acronyms and values as to their
relevance. Would be gratefull if you could provide a bit more background in
terms of the basics...

[syseng68k]

slacktide:


This entire argument regarding the autoignition temperature of aluminum and
CFRP is bogus from the beginning as it ignores thermal mass. Place a 2" thick
paper textbook and an empty aluminum beer can in front of a lit propane torch,
and let me know which one burns through first.
Hardly the same conditions, is it ?, as in your example, there isn't the
cooling effect of the outside air rushing by at -50C. The aluminium pan on
a gas stove boiling water is a far better analogy. Fact is, composites are a
good heat insulator, so would get little benefit from outside air cooling.
Of course, all bets are off for both materials on the ground, with no
cooling.

If such a minor fire can cause so much trouble and unknown level of material
degradation, one wonders why fire insulation wasn't fitted to the upper half
of the fuselage. One would think that it should have been mandatory with
such a heat sensitive material...

[syseng68k]

Shirley shom mishtake (that's enough of that. ed) :hmm:

[Coagie]

Has anyone seen pictures of the damage to the inside of the aircraft? There's a chance the damage is pretty extensive, because, with the insulating effect of the composite, it won't transfer the heat to the outside, as quickly as aluminum. It's like the difference of holding a hot cup of coffee in a porcelain cup, instead of a tin cup. You could hold the porcelain cup with your hand, but the tin cup, you'd need to use the handle. In other words, an aluminum skin may have burned clean through, where as the composite skin, only showed burn marks on the outside, but didn't burn through. It may look worse on the interior of the plane than we imagine! Also, imagine the fumes, from the burning composite. Yuck!

[kenneth house]

i enjoy the attention to precision in the written word--it seems to be primarily a British trait as keepers of the king's english. We are after all two countries separated by a common language.

OT: A crushed pair of battery leads eventually shorted together and generated enough heat to start a fire that has a curious burn pattern--it appears as two charred areas, one forward and one aft of a central region with no burning. What is in the central region that wasn't affected?

[bartonflyer]

Queen's English dear boy! We haven't had a King for a while, though now we've got three lined up!

[syseng68k]

Kenneth:

...and, curiously, the smashed wires that are said to have caused the fire are still in good enough condition
that the "smashing" is evident. One would expect that such wire would need to be red hot and melt to cause a
fire in an area with what (?) other nearby combustable materials to spread to.

That and the fact that the elt battery has a current limiting fuse in each leg and is in
a sealed enclosure.

Sorry, but i;'m not buying any of this supposition (perhaps a different word
would be better ?) until there's more concrete evidence...

[Coagie]

OT: A crushed pair of battery leads eventually shorted together and generated enough heat to start a fire that has a curious burn pattern--it appears as two charred areas, one forward and one aft of a central region with no burning. What is in the central region that wasn't affected?I guess that's why a picture is worth a thousand words. I wish they'd publish some pictures of the beacon in question. Maybe the wires weren't pinched, crushed, or smashed after all? Maybe some high voltage got in those wires/leads and arced through the insulation, like a spark plug wire in a car arcing to ground, during wet weather? That's a high tension lead arcing to earth, for British Pruners, I think.

[eminencegrise]

"Investigators believe the July 12 fire on a 787 Dreamliner at Heathrow was likely caused by incorrect installation of a battery that pinched some wires and caused a short circuit." - Seattle Times

The ELT battery (and for that matter other batteries on-board) should have an internal fuse that will open on an over-current condition preventing this type of incident.

[Coagie]

A heck of a coincidence, but maybe, the beacon wires were already burned, from the first time it was powered up, and the fire in question, just happened to be in the proximity of the beacon, so the investigators saw it and said "Well, there's your problem right there!" I've seen this a lot, troubleshooting electrical, electronic, and other technical problems, over the years. People assume that the first problem they see is the problem they are looking for, but it turns out to be unrelated. Wonder if there's a way to test, with some precision, "how fresh" the burned wire insulation is?

[olasek]

Maybe some high voltage From where? And what is 'high'?

[Coagie]

From where? And what is 'high'?High enough to arc through the insulation! Happens on spark plug wires all the time. Could come from lightening, St Elmo's fire, or static discharge. Doesn't necessarily need to be high current, just high voltage, maybe a few thousands of volts. In a moist environment, not as many thousands, as in a dry environment. There's been talk of the insulation being thin, which makes it even more likely to arc to ground.

[Jetstream67]

Well 'Smashed' is certainly not a precise term to apply to cable / wire. . and in this case where reading between the lines the ELT case was closed with the ?battery? leads out of place you would expect some more precision (crushed, crushed together, flattened, split, nicked, trapped etc.)

(And like the other poster I'd think unless the battery fusing was incorrect, omitted or failed this short circuit should simply have blown the battery protective fuse (s) before the battery could overheat.)

You end up thinking the presumed short set fire to some other component in the ELT and that fire then spread to set the battery off . . except very few professional grade electronic components burn for long or that well in a sealed container. . .

[Coagie]

If the fire did originate from the beacon, the cause didn't need to be internal to the beacon. If there were something wrong with the charging voltage, where it was a few volts higher than need be, it could definitely cause a battery, Lithium Ion, or not, to catch fire. A battery is charged at a higher voltage than the battery puts out. A 12 volt car battery might be charged at around 14 volts, but charge it with 20 volts, and it just might explode. I don't know what the supply/charging voltage was to the Honeywell beacon, but if it was supposed to be 30 volts and was 33 volts instead, adjusted wrong, or wrong for some other reason, it could cause a fire or explosion. So the fault not being with the beacon, but with the circuit supplying it.

[olasek]

So the fault not being with the beacon, but with the circuit supplying it. :ugh::ugh:
It has been stated here numerous times - the ELT battery is not chargeable, ELT is completely stand alone unit, it is sealed and not connected with the rest of the aircraft. There are only two wires going outside of ELT to a switch - so a pilot could turn the antenna ON but 787 (or any other aircraft) doesn't supply ELT with any voltage/current.

[Coagie]

You end up thinking the presumed short set fire to some other component in the ELT and that fire then spread to set the battery off . . except very few professional grade electronic components burn for long or that well in a sealed container. . .Jetstream67, I'm with you on that. That's why I wondered if the beacon were a red herring. We need pictures and more information! How does the NTSB and other investigators expect PPRUNE to help them solve the problem, if they don't give us the information! It's almost as if, they don't care if we help or not! BTW: If you European's had used Aluminum, instead of Aluminium, on your aeroplanes, you wouldn't have needed to resort to composites on Airbus! ...Kidding, of course!

[Jetstream67]

Agree - Everything said to date by the investigators suggests the problem was initially something contained within the ELT case before presumably an exploding Lithium battery punched through the ELT casing and spread the fire (as sadly they do rather easily) . . . . and Coagie it has been said many times it was a Primary i.e. non rechargeable Lithium battery

[Coagie]

Olesek, I stand corrected. That makes perfect sense, to not have a charging circuit, since it's battery is good for 10 years. Apologies, too much coffee this morning has made me impulsive! Didn't think it through.

[Jetstream67]

coagie Yep but speling probably not the issue here :)

[Coagie]

I referred to the ELT battery as "Lithium Ion", when it's probably just a Lithium battery, like one might use in a camera, or smoke detector. Sorry about that.

[Coagie]

That and the fact that the elt battery has a current limiting fuse in each leg and is in
a sealed enclosure.Syseng68k, You're right. But, I think, even without fuses, the battery leads, if shorted together or to ground, would probably just melt through, stopping the current flow, before the battery barely got warm to the touch, and in a sealed environment, there wouldn't be enough oxygen to sustain a fire long enough (if one even started inside the ELT), that would burn through the enclosure.

[Yancey Slide]

":ugh::ugh:
It has been stated here numerous times - the ELT battery is not chargeable, ELT is completely stand alone unit, it is sealed and not connected with the rest of the aircraft. There are only two wires going outside of ELT to a switch - so a pilot could turn the antenna ON but 787 (or any other aircraft) doesn't supply ELT with any voltage/current. "

Except for 406MHz which also have at least 2 more wires for GPS feeds for position data and a coax cable to an antenna. However yes, you are correct that they are not externally powered.

[olasek]

The just released July 22 issue of Aviation Week & SP has extensive article on the fire. I can't retype the whole article (online version is for separate subscription) but I can quote some parts (page 23):

....Insiders also quietly note that the composite structure held up well to the fire. Compared to conventional aluminium, for which FAA tests have shown burn-through times of 30-60 sec in intense fires, Boeing flame tests exhibited longer burn-through times for sections representative of 787's composite laminate skin. The aircraft maker also points out that although the fire was severe enough to visibly char the exterior of the skin, the fire did not penetrate the surface.
The composite repair technique, although expected to be complex and costly, is also likely to be relatively easier that a similarly scaled repair to an aluminium-skinned airframe because no testing or checking will be required to match the ductility of the replaced skin with the surrounding structure. All aluminium aircraft skins are subjected to annealing, a heat treatment which makes them more workable and reduces internal stresses, and skins adjacent to those which have been affected by fire must be checked to evaluate their condition.....

[Speed of Sound]

That and the fact that the elt battery has a current limiting fuse in each leg

If the 'crushed' wire was between the positive terminal and the fuse then there is nothing to stop a dead short to the case.

[syseng68k]

SoS:

If the 'crushed' wire was between the positive terminal and the fuse then
there is nothing to stop a dead short to the case.
Agreed, but to get a short circuit, you need current flow from one terminal
of the battery to the other. Even if one side were grounded before the fuse,
the other side would still be floating, so no current flow. The battery
case itself will be provide isolation to the battery internals and the elt
electronics won't be grounded to dc anywhere on the pcbs. That is, the case
will be floating w/respect to the elt electronics.

In any case, as someone else noted, even if an internal elt wire did burn
through, it would be over in a second or two and should not have anything like
enough energy to start a fire externally.

Not being just b awkward here, but none of the evidence released to date adds
up and there does seem to be an intentional information blackout...

[DWS]

If the 'crushed' wire was between the positive terminal and the fuse then there is nothing to stop a dead short to the case.

That would be true IF only about the ELT. But two( or more ) possibilities still exist

1) somewhere in the numerous junction boxes/electrcial load /transfer/boxes and remote switching could be a sneak circuit- by moisture or by abrasion, etc. That would put up to 32 volts from either of two " main" batteries on perhaps the normal isolated cockpit/ data lines to ELT ???

2) early mention of ' sparks" in the A/C unit somewhere- but not clear when. Ground power was connected- but turned off at pad supposedly. IF true that sparks were noticed AFTER ground power disconnected- a whole new story.
IF sparks when connected- then why wasn't it checked out. ( unless there is nothing in check lists for sparks in A/C ??? :uhoh:

[cappt]

is also likely to be relatively easier that a similarly scaled repair to an aluminium-skinned

Sounds like management blowing roses and not the people actually tasked with the repair. I'd take that bet.

[Pittsextra]

Got to be honest overall they were pretty unconcerned about this situation and re the repair a specific question was asked :-

Our next question is from Josh Freed with the Associated Press. Please go ahead.
<Q - Josh Freed>: Hi, there. On the Heathrow 787, can you say whether Boeing is going to pay for that warranty and
conduct a warranty repair, pay for the repair under warranty and pay for it? And then more big picture, can you say sort
of where that fits in with your kind of readiness to carry out repairs like that? I mean, is that something that you guys
are figuring you'll do in-house? Is that more of a contractor thing? How should we think about how future hull repairs
will be done on 787s?
<A - W. James McNerney>: Well, any hull has – gets dinged up, okay? With lots of customers over – and we do have
warranty programs that cover a lot of this. This specific incident you're talking about, I assume, was Ethiopian.
<Q - Josh Freed>: Yeah.
<A - W. James McNerney>: And, yeah, and we're in discussions with them right now about how to handle that. We
want to make sure they are in agreement with our approach. We have – for the last five or six years, we've thought
about how to repair composite structures when they are damaged and we will obviously honor any and all warranty
obligations as we do that. And typically both we and the carrier have insurance that back this up. So this – if the
question eventually gets to a financial impact, there will be very little.
<Q - Josh Freed>: Sure. And is that a repair that you folks would typically carry out in-house? Or does that – or do
you expect that future hull repairs would be done more by third parties?
<A - W. James McNerney>: I think typically as we introduce new airplanes, we disproportionately do the repair. But
over time, the industry learns how to do the repair, and we work with other maintenance and repair operations because
it benefits our customers to have decentralized capability around the world. I think in this case, we will have, I think,
Ethiopia in this case because it's a very new model, very new airplane type, who rely on us disproportionately for the
advice on how to handle it.
<Q - Josh Freed>: All right. Thank you.

[A and C]

I started thirty-five years ago in the aircraft maintenance business repairing metal aircraft, the last twenty years I have been increasingly involved in composite repair and in my view the Boeing statement has a good foundation in truth.

To the metalcentric ways of thinking that pervade this business I can see how you might come to this conclusion but the repair techniques required for composite structures are very different and should not be seen from a "this is how we do a metal repair" point of view.

[old dawg]

@DWS

Mention of sparks in aircon on post 89 on this thread.

Source is article in Financial Times on the 12th July 2013

[Speed of Sound]

Agreed, but to get a short circuit, you need current flow from one terminal
of the battery to the other. Even if one side were grounded before the fuse,
the other side would still be floating, so no current flow.

Sorry, I should have been clearer. The return path is through the damaged battery casing via the ELT casing.

The first announcement we had was that the battery seems to have sustained pre-fire damage and the crushed wire finding came later. Is that still the case?

My statement above was based on a scenario where the crushed wire, from the time of assembly, was a passive and isolated path to the casing until such time as the cell burst and exposed the anode or cathode to the ELT casing. If the crushed wire was the opposite polarity to the part of the battery that had become exposed then, current will flow.

This, of course, assumes that the battery did rupture at some point. As you correctly point out, a crushed wire itself, will not complete the circuit.

[fenland787]

Is it possible that what is being reported as a 'wire' could actually be two wires sleeved together and forming the flying lead from the battery pack?

If that is the case then pinching that may be all you need to short the battery. Trouble with that is I can't imagine that there wasn't a fuse within the battery, so it should still be protected against a short circuit.

Assuming the cause was thermal runaway in the lithium battery, and I can't think how else there was enough fuel to keep a fire going long enough to do the damage, then I think we are left with a failure that somehow didn't draw a high enough current to blow the fuse but was high enough to heat the battery fairly significantly.

That, combined with a very hot day, a closed up airplane and the ELT located in the crown could easily have got the battery temperature to over 60 deg C which is all it takes apparently!

[MPN11]

Fox News scrawl (apologies) says its the ELB. I think ... Now it's time for sport.


Apologies for iPad posting.

[syseng68k]

DWS:

1) somewhere in the numerous junction boxes/electrcial load /transfer/boxes
and remote switching could be a sneak circuit- by moisture or by abrasion,
etc. That would put up to 32 volts from either of two " main" batteries on
perhaps the normal isolated cockpit/ data lines to ELT ???.
Abrasion, loose terminals, crimps or other electrical problem generating
enough heat to cause a fire. I think that's a much more likely scenario, as the
energy density required to set light to the composite would be quite high
(otherwise it has no business being used in a transport a/c) and need to be
sustained for some time to cause what is reported to be major damage, enough
to scorch the outer skin. What materials sustained the fire, once started ?.

The elt batteries are not in that class really, but ok, if we suspend critical
facilities for a moment, what was adjacent to the elt to spread / aggravate
a minor fire into a fairly major one ?. Does anyone have links to a pic of the
elt installation in the a/c, or just a pic of the internals around that area ?.
Would be very helpful to have that...

[Machaca]

This shows the interior of Section 47 being fitted:

http://i337.photobucket.com/albums/n385/motidog/787section47inside_zps396bb1cf.jpg (http://s337.photobucket.com/user/motidog/media/787section47inside_zps396bb1cf.jpg.html)


http://i337.photobucket.com/albums/n385/motidog/787sec4748a_zpsf43245fa.jpg (http://s337.photobucket.com/user/motidog/media/787sec4748a_zpsf43245fa.jpg.html)

[Ancient Mariner]

I have posted this picture earlier in the 787 thread.
It shows a brand new spare Lithium battery for a SART (Search And Rescue Transponder). It was not being charged, it was not being discharged, there were no pinched wires and the manufacturer could not explain why it ignited, but it did. The damages to our store room and office was incredible from this small battery, probably 1/3 of the size on an IPERB/ELB. To protect the battery it had a solid end cap screwed on, see the tops of the remaining batteries, this was blown off and the battery went like a projectile around the store room denting fairly strong steel shelfs and leaving scorched painted steel in its wake before it came to rest with enough energy remaining to burn into the protective casing of the battery it is resting against.
These batteries scare me.
Per

http://i1339.photobucket.com/albums/o702/perebs/DSC_0001cropped_zps979dbacf.jpg (http://s1339.photobucket.com/user/perebs/media/DSC_0001cropped_zps979dbacf.jpg.html)

[syseng68k]

That looks pretty convincing. Had it ever been dropped / physically abused,
was it a manufacturing defect or what ?. Compared to the size of the bricks,
those batteries look much larger than the elt type. Are they the same type
and chemistry, or for a different application ?. You said transponder and the
elt doesn't transpond.

I guess this must also have been reported to the safety authorities, so what
was their reaction ?...

[Ancient Mariner]

The batteries were taken straight out of the box and put on shelves, they were airfreighted! to us and we could not find anything wrong with the boxes. We reported the incident to the manufacturer of the SART and sent them the affected battery which they in turn passed on to the battery manufacturer. The only feedback we got was that they could not find any faults. I left the company a few months later, unrelated.
That particular battery is now obsolete so I am unable to find any dimensions or chemical composition data. Happened about 8 years ago.
And yes, this was a RADAR transponder.
Per

[Ian W]

Syseng68k
Abrasion, loose terminals, crimps or other electrical problem generating
enough heat to cause a fire. I think that's a much more likely scenario, as the
energy density required to set light to the composite would be quite high
(otherwise it has no business being used in a transport a/c) and need to be
sustained for some time to cause what is reported to be major damage, enough
to scorch the outer skin. What materials sustained the fire, once started ?.

The elt batteries are not in that class really, but ok, if we suspend critical
facilities for a moment, what was adjacent to the elt to spread / aggravate
a minor fire into a fairly major one ?. Does anyone have links to a pic of the
elt installation in the a/c, or just a pic of the internals around that area ?.
Would be very helpful to have that... While everyone is hypothesising.... take the report from Ancient Mariner about a "small battery, probably 1/3 of the size on an IPERB/ELB" so scale it up to a much larger battery and put that battery in a strong metal container that has its hermetic seal compromised by crushed power wire(s). The repeated heat from the sun on a hot day expands the metal box and eventually the compromised insulation allows a short while the same heat has already taken the battery to critical temperature. The energy release is inside a hermetically sealed box with the exception of the break caused by the same crushed wire(s). All the exothermic energy that led to Ancient Mariner's battery flying around the room is now focused in a jet through the break in the hermetic seal of the ELT. Effectively the ELT could become a self fuelling blow torch anchored to the crown of the fuselage as the battery goes into thermal runaway.

From Battery fires: keeping the Li-ion caged | Aviation International News (http://www.ainonline.com/aviation-news/aviation-international-news/2012-02-01/battery-fires-keeping-li-ion-caged)

"Thermal runaway can occur when the battery self-heats, which can happen when electrolyte reaches temperatures as low as 158 to 194 degrees F (70 to 90 degrees C), according to the FPRF report. Runaway accelerates quickly at higher temperatures, and the greater the charge in the battery, the faster runaway happens. Temperatures during a runaway can reach 1,110 degrees F (600 degrees C). The battery cells will also experience increased pressure, venting or popping of the cell, possible ignition of cell gases, possible ejection of cell contents and propagation to adjacent cells.According to the FPRF report,

“Venting of isolated small cells (cellphone cells and smaller) seldom results in flame ignition. This is likely due to the limited volumes of vent gases released from these cells–that is, the gases become diluted before ignition can occur. In comparison, ignition of vent gases from 18650 and larger cells [used in some laptops] is fairly common: these cells contain more electrolyte (more fuel), and are usually used in multi-cell battery packs. If the flow of vent gases is ‘restricted’ due to the configuration of a vent port (typical in hard case cells), flames emanating from the cell will be highly directional (flames from 18650 cells are often described as ‘torch-like’)."

My bolding.

That description could explain the damage and the heat in the area of the Ethiopian 787 ELT.

Addition:
A photo of a laptop with a thermal runaway from Lithium-ion Safety Concerns ? Battery University (http://batteryuniversity.com/learn/article/lithium_ion_safety_concerns)

http://www.batteryuniversity.com/images/partone-5b-3.jpg

[syseng68k]

Ian W:

I'm going to look b awkward again, but laptop batteries are rechargeable and
use a different chemistry. We all know some laptop batteries have had issues,
but it's not really relevant to this thread.

Ancient Mariner's post (thanks) triggered memories from years ago about
the volatility and safety of early lithium batteries, primary non rechargeable
types, but haven't heard any reports for years in that respect. My guess
is that the unsafe chemistries from years ago are no longer used. The cells
used in the elt are lithium manganese, nothing like the lithium ion types used
in laptops. The lithium managanese types are also the most common chemistry used
for consumer products, lithium coin cells etc, which are well proven and safe.

Good overview in a Wikipedia article here:

Lithium battery - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/Lithium_battery)

[DWS]

and in a sealed environment, there wouldn't be enough oxygen to sustain a fire long enough (if one even started inside the ELT), that would burn through the enclosure.

LI -x batteries do NOT need Oxygen to continue to flame- the chemistry is such they generate thier OWN oxygen.

ELT batteries are NOT chargeable

ELT is not normally connected to Aircraft electrical system- note I said NORMALLY - but ' sneak" circuits due to poor grounding, flaky connections, crossed wires, etc ** could ** possibly exist. Battery protection diodes can fail for example internally, etc. LI-x fires can be like a cutting torch.

Model airplane LI-x batteries can and do catch fire if abused/shorted/etc but they ARE rechargeable.

:*

[olasek]

. My guess
is that the unsafe chemistries from years ago are no longer used.Technology improves but "safe" never means absolute safety, there is always statistical chance for this first occurrence. "Today" is probably better than "years ago" but far from perfection.

[Coagie]

LI -x batteries do NOT need Oxygen to continue to flame- the chemistry is such they generate thier OWN oxygen.

ELT batteries are NOT chargeable

ELT is not normally connected to Aircraft electrical system- note I said NORMALLY - but ' sneak" circuits due to poor grounding, flaky connections, crossed wires, etc ** could ** possibly exist. Battery protection diodes can fail for example internally, etc. LI-x fires can be like a cutting torch.

Model airplane LI-x batteries can and do catch fire if abused/shorted/etc but they ARE rechargeable.DWS and Ancient Mariner, after reading your posts and looking at the picture of the burned battery, It seems like I have a lot to learn about Lithium batteries. Some of them are really scary. Maybe, like the battery in the closet, the one in the ELT caught fire for no apparent reason without even needing "crushed wires". That is extra scary. In a hermetically sealed box, it might be more like a bomb! I'm making the lithium battery too analogous to more common batteries I'm accustomed to. I may not always be right, but I'm clever enough to know, when I need further study. As much as I know, I learn a lot from our brainstorming, and appreciate everyone's patience with one another.

[kenneth house]

Ancient Mariner showed photos (many thanks) and said:

[The batteries were taken straight out of the box and put on shelves, they were airfreighted! to us and we could not find anything wrong with the boxes. ]

i wonder if the reduced pressure environment of the freight cargo hold may have been an overlooked factor causing internal cell damage that later erupted in the storage room (e.g. venting, cell wall flex and distortion, expansion of the foil roll, shorting of internal electrodes to foils or case, etc.) A cell may look fine on the outside but be damaged and slow-cooking on the inside.

[Volume]

As Reuters (http://www.reuters.com/article/2013/07/26/us-ana-dreamliner-beacon-idUSBRE96P0AK20130726) reports, ANA found damaged wiring in their ELTs.
Japan's ANA Holdings Inc, which operates the world's biggest fleet of Boeing Co Dreamliners, said it found damage to the battery wiring on two 787 locator beacons during checks after the devices were identified as the likely cause of a fire on another aircraft in London this month.

[EEngr]

787 fire investigation looks at pinched battery wiring | Business & Technology | The Seattle Times (http://seattletimes.com/html/businesstechnology/2021456975_787firesourcexml.html)

"The two sources suggested that Honeywell might have replaced the batteries at some stage before delivery of the jet because the devices sat on the shelf during the years-long 787 program delays."

Sat on whose shelf? Are these ELTs 787 specific parts? Or are they used across various models? If its the latter, then I'd expect Honeywell to pull stock and ship it as various orders came in. If the 787 program was a couple of years late, they'd ship units built later on.

If it was Boeing's shelf, then who replaced the batteries? If Boeing took possession of the units and shelved them, then they'd be responsible for maintenance. Seeing how this was not standard in-service fleet maintenance, who did they send into the warehouse, screwdriver in hand, to swap the batteries?

Given several possible scenarios, this looks like it could be a maintenance procedure problem. Airlines take steps to make sure that work is performed by qualified personnel. because this is a part of their normal business function. But out of sequence manufacturing or maintenance can be a planning headache.

[Coagie]

If it was Boeing's shelf, then who replaced the batteries? If Boeing took possession of the units and shelved them, then they'd be responsible for maintenance. Seeing how this was not standard in-service fleet maintenance, who did they send into the warehouse, screwdriver in hand, to swap the batteries?Great point. Say if the ELT were manufactured in 2006, someone might find it prudent to put fresh Lithium batteries in them, since they are supposed to be good for 10 years, before installing them in a plane finished in 2011 or so, so the carrier wouldn't need to turn around in 2016 and replace the battery. Someone unfamilier with the particular ELT, changing the battery, would explain a lot. Honeywell should put a tamper evident seal on there various beacons, and require that, when their battery is 10 years old, the whole unit be swapped with a new one, and the old one sent back, to get a new battery. One of those "No User Serviceable Parts Inside" kind of things. It's for what is sometimes referred to as "Post consumer control of your product". Maybe it's already like that? Maybe someone on the forum knows?

[Coagie]

It's probably more complex than this, but, just a thought or two. If the ELT uses a Lithium Magnesium battery, I hope the Magnesium isn't in the same form as was used in "Mag" wheels! Hard to control fires from car wrecks was the reason "Mag" wheels aren't made of Magnesium any longer, but instead are made of Aluminum. . Maybe this type of battery should only be small, for use in low capacity situations, like in smoke detectors, watches, and cameras, so the stored energy isn't enough to burn through routine precautions. I'm sure an alert beacon transmitter would use a lot of current, if it's to transmit for very long, so it probably has a pretty high capacity battery. I've brushed up on my knowledge of different Lithium battery technologies, and it seems like using high capacity ones and/or storing them in close proximity to each other, may be a no no, across the board, until better practices in quality control, design, and use are practiced!

[theroadie]

"It's probably more complex than this,"

To be sure. It's MANGANESE, not MAGNESIUM. And it's in a dioxide form, not elemental. :ugh:

[Machaca]

Reuters reports (http://www.reuters.com/article/2013/07/26/ana-dreamliner-beacon-idUSL4N0FW2AQ20130726):

...ANA...said it found damage to the battery wiring on two 787 locator beacons during checks...


The damage was slight, but the beacons have been sent to the manufacturer, Honeywell International Inc, for inspection...

[Coagie]

To be sure. It's MANGANESE, not MAGNESIUM. And it's in a dioxide form, not elemental. :ugh:Magnesium, Manganese, ... What's the difference? Ha, ha ...I didn't know what sort of battery the ELT used, I thought it might have been something like this: Torqeedo 24-Volt Lithium Magnesium Battery : Cabela's (http://www.cabelas.com/product/Torqeedo-Volt-Lithium-Magnesium-Battery/1585266.uts?productVariantId=3320596&WT.tsrc=CSE&WT.mc_id=GoogleProductAds&WT.z_mc_id1=03568745&rid=40&channel=GoogleBaseUSA&mr:trackingCode=ECCD2875-F276-E211-BA78-001B21631C34&mr:referralID=NA&mr:adType=pla&mr:ad=29133952031&mr:keyword=&mr:match=&mr:filter=52254830951&gclid=CKv_8e_kzbgCFSpk7AodOzkA0g)
A Lithium Magnesium battery. I thought I'd read, was the battery in Ancient Mariner's picture, but I could be wrong. Anyway, it didn't seem far fetched, that the ELT might use the same type of battery. Of course, the Magnesium, might not be in it's elemental state either, so could be perfectly safe.

[fenland787]

Magnesium, Manganese, ... What's the difference?What's the difference? Cor, strike a light.....no....on second thoughts don't, or you'll find out! :)

[no-hoper]

The type of battery (5 ea /pack) should be one of these:

UHR-CR25650-LVP (U10027) - Battery & Energy Products: Commercial | Ultralife Corporation (http://ultralifecorporation.com/be-commercial/products/cr-cylindrical-limno2/uhr-cr25650-lvt/)

UHR-CR34610-TSO (U10028, U10029) - Battery & Energy Products: Commercial | Ultralife Corporation (http://ultralifecorporation.com/be-commercial/products/cr-cylindrical-limno2/uhr-34610-tso/)

[Machaca]

Coagie: Magnesium, Manganese, ... What's the difference? Ha, ha ...I didn't know what sort of battery the ELT used, I thought it might have been...


All such relevant, and serious, details have been covered in this thread. You would be best served by keeping up before contributing.

[bsieker]

Coagie,

the quoted website also confuses magnesium and manganese: the torqueedo batteries are also Lithium-Mangenese (Mn): This has nothing to do with Magnesium (Mg).

[DWS]

United Continental Holdings Inc. ( UAL (http://www.nasdaq.com/symbol/ual) ) said it has found pinched wiring in one Boeing Co. 787 Emergency Location Transmitter as part of Federal Aviation Administration mandated inspections.
The inspections come in the wake of a fire aboard an empty Ethiopian Airlines 787 at Heathrow Airport on July 12. U.K. Investigators recommended inspections as part of its findings.
A spokeswoman for United said inspections of its fleet of six 787s are now completed and the "defective" transmitter has been sent back to supplier Honeywell International Inc. ( HON (http://www.nasdaq.com/symbol/hon) ) for evaluation.
The spokeswoman said there was no disruption to United's flight schedule as a result of the inspections.

Read more: United Finds Pinched Wiring on Boeing 787 Transmitter (http://www.nasdaq.com/article/united-finds-pinched-wiring-on-boeing-787-transmitter-20130726-00721#ixzz2aBzxJufE)

GEEZE- Ethiopia, Japan, United - all finding pinched wiring on ELT ??

maybe from same batch- ??

Or did the faster and cheaper mantra catch up with Honey-bucket er Well ??

Or were they produced on a Monday like De-troit cars- after a hangover ??

And about inspection and Q/C ??

[Coagie]

the quoted website also confuses magnesium and manganese: the torqueedo batteries are also Lithium-Mangenese (Mn): This has nothing to do with Magnesium (Mg) Bernd, I stand corrected. Thank you. Germans always were good at chemistry. Maybe I should use something other than a Cabela's Outfitters catalog for my research? Anyway, I do stand by my broad brushing of being careful how to use and store higher capacity Lithium batteries. It seems the thermal runaway chance is just too great, to use or store them in anything but a very careful manner! If they are too close together, one bad apple can spoil the bunch. There is some talk of using Magnesium and Sulfur for some kind of electric car batteries. Hope the Magnesium isn't in a dangerous state in that case.

[Coagie]

All such relevant, and serious, details have been covered in this thread. You would be best served by keeping up before contributing. Machaca, Wico! I have read the entire thread, but I got sloppy, and was trying to go by memory, when I should have reviewed the earlier posts. Apologies to all. BTW: Lighten up Machaca, Life is too short.

[Coagie]

GEEZE- Ethiopia, Japan, United - all finding pinched wiring on ELT ??

maybe from same batch- ?? Guess they need to check the lot number, and see if they are from the same production run, then if so, have all of them pulled, in case the person inspecting didn't have his glasses on. I don't know about Honeywell, and I hope this isn't happening at Honeywell, but in some high tech manufacturers, to save money, when there's an item that doesn't require a constant production, rather than have permanent employees to assemble the item, some companies just wait until they have enough orders to justify a production run, and then hire temporary workers, just for that run. They try to get experienced workers, but it sure opens things up for mistakes. Quite often, the mistakes are "pinched wires" as a matter of fact.

[SLFgeek]

If any wires were to become pinched, and if these wires only had a very thin layer of Teflon insulation, rather than much tougher PVC based coverings....

Been lurking quietly and following various aspects of this thread. The above may be an important clue, especially with respect to the ELT. One of the interesting features of teflon insulation (FEP and PTFE) is that in a stressed situation it will slowly do something referred to as 'cold flow'. I first witnessed this about 40 years ago, involving some teflon insulated wire-wrap circuits, on a Univac backplane, where the wires had been pulled too tight against a 90-degree turn, and the teflon insulation eventually cold-flowed to the extent that it made electrical contact with the wire-wrap post that the turn was against. That the battery wire in the ELT appear to have been 'pinched' (based on various sources) and the likelihood that it could be teflon insulated as well, this could be a delayed cold-flow event. The unit was assembled, tested, everything looked good, and then (over time) the pinched insulation flowed back, and a short developed. One possible theory on how this occurred. If so, it is very lucky that the incident happened on an airframe sitting on the stand, with no pax on board.

NASA makes mention of 'cold flow' on this page (right most column, first entry) ...
NASA Parts Selection List (NPSL) - Wire Insulation Selection Guidelines (http://nepp.nasa.gov/npsl/wire/insulation_guide.htm)

[Radix]

............

[fenland787]

Only needs to be marginally watertight, enough to survive just one hour in (only) one meter of waterWell, in a submarine perhaps but airplane terms that is not really 'marginal'!

DO160F 'Waterproofness' doesn't even have immersion listed as a test method.

If the ELT is specified by the manufacturer as "Permanently Hermetically Sealed and airtight' (I don't know if that is the case, but I doubt it) then DO160 exempts it from further waterproofness testing, if not then the relevent tests for airplane use will be in DO160 Section 10 and will be selected from four test methods, in increasing order of severity:

'Condensing Water Drip'
'Drip Proof'
'Spray Proof'
'Continuous Stream' (this one is fun - think big pressure washer jet aimed at the most vulnerable joints and connectors!)

The choice of test will be made based on equipment type and it's location in the airplane. I don't know which was selected for the ELT in question.

So to say "787 is to wet for electronics" is clearly inaccurate however there may need to be a review of matching test method to equipment type and location if, and only if, there are repeated and multiple examples of random bits of electronics failing due to water ingress. I don't think we have any facts to show that yet?

Don't confuse occasional poor manufacturing quality with design failings - and before I get jumped on, I accept repeated manufacturing errors can indicate poor design of course.

....such as several occurrences of the same wires getting pinched when a battery that is designed to be replaced in service is fitted for instance....... (This example picked entirely at random you understand!)

[glad rag]

.......some of the highest rated exe electrical enclosures use water pressure to ensure their sealing underwater......

[LASJayhawk]

Coegie, we've gone away from the "no user serviceable parts inside" , it's a maintenance headache. The older Dukane ULB's (pingers) used to have to go back to the factory for a battery change, the new ones are field replaceable.

What I don't understand is why they are only checking the ones in the '87. Honeywell said there are over 6000 in service. Seems we should be checking them all.
Link to AD http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgAD.nsf/0/7848e4f089b443ec86257bb40048d733/$FILE/2013-15-07.pdf

It does say " This AD is considered to be interim action. Because the fire occurred on a Model 787-8 airplane,required actions in this AD are focused on Honeywell fixed ELTs installed on that model. However,we acknowledge that ELTs are installed on various other aircraft; therefore, continued investigation is required. Once final action has been identified, we might consider further rulemaking. "

ETA: fixed link

[Coagie]

What I don't understand is why they are only checking the ones in the '87. Honeywell said there are over 6000 in service. Seems we should be checking them all.
Link to AD http://rgl.faa.gov/Regulatory_and_Gu...2013-15-07.pdf (http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgAD.nsf/0/7848e4f089b443ec86257bb40048d733/$FILE/2013-15-07.pdf) Maybe the bad lot was just installed on the 787, but, who knows, it may not just be a bad lot? If there is only 6000 out there, it would be a great idea for Honeywell to issue a service bulletin instructing owners and maintenance crews how to check their ELT's for damage..

[amicus]

SLFgeek,
Am very familiar with this issue from Atlas missile days back in the 60's. Looks like Boeing and Honeywell (who installed the batteries??) forgot their basic materials lessons yet again.

[Karel_x]

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

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

I suppose that the AFN2 is used in 787 but is it spread also in older a/c?

[fenland787]

SFL geek and Amicus are correct about cold flow issues, I am just wondering how/why we think we know Honeywell used "thin teflon insulated wire" in the location where the issue occurred?

There was a list of approved wire for the 787, I very much doubt that was on it at all, and if it was it would have been for very specific applications, given it is known to have very poor cut-thru resistance, suffers from cold-flow and is heavy! The only real thing going for it is it's high temperature performance.

Assuming we are talking battery leads, I would expect it more likely that a single or double insulated wire with a polymer such as crosslinked ETFE or PDVF/PVF2 outer sheath would be called out?

Amicus, I too was wondering who actually fitted the batteries, given the production delays it is not beyond the bounds of possibility that the early deliveries of ELT were either without batteries or had them removed to be fitted later and given the focus on only units in 787...makes you wonder?

[EEngr]

What I don't understand is why they are only checking the ones in the '87. Honeywell said there are over 6000 in service. Seems we should be checking them all.It could have something to do with battery replacements performed on the units in storage intended for the 787 line.

Normally, I would expect line maintenance to be performed by techs trained and certified to do such work. Including watching for pinched wiring. So the question is: Who did the work on the units stored at Honeywell/Boeing? Perhaps the regulators were already made aware of this maintenance procedure anomaly and decided not to impose additional costs on their other customers.

[theroadie]

They may find a single undertrained tech did the battery work on all suspect units. Or the design could be conducive to wire pinching during cover install, without provision for a visual inspection.

[Eclectic]

These people seem to have an eye on the Ethipian fire and its ongoing aftermath. Analysis: Boeing 787 Dreamliner In the Hot Seat Again After Fire at Heathrow Airport (http://airchive.com/blog/2013/07/12/analysis-boeing-787-dreamliner-in-the-hot-seat-again-after-fire-at-heathrow-airport/?utm_content=buffer56b53&utm_source=buffer&utm_medium=twitter&utm_campaign=Buffer)

Update 17: Sunday, July 28 11:15AM E.D.T.

ANA and United Airlines have both found problems with the Honeywell ELT beacons. The issues appears to involve a pinched wire in the emergency locator transmitter. United has completed its inspection of its six 787 fleet, where it located one defective transmitter. ANA also found the same issue in its ELT on 1 example of its fleet and on another uninstalled portable beacon. ANA has removed all beacons from the eight 787s used on domestic routes . JAL completed investigations this weekend on its 9 787s. The FAA and Japan’s transport safety ministry followed suit with the UK’s AAIB in recommending removal or inspection of the ELTs, 2 weeks after the Ethiopian issue. European operators LOT, Thomson, Norwegian Air Shuttle, and British Airways (who is set to debut the 787 September 1st) have removed he ELTs from their aircraft but have not reported damage publicly. This far, no airlines other then Ethiopian obviously have suffered service interruptions as result of the ELT issue, though a Qatar 787 has been grounded on Monday due to an unspecified “minor” technical issue. Boeing has now delivered some 70 787s to its customers, around 20 since the grounding order was lifted in April, including new customers China Southern, Norwegian Air Shuttle, Thomson, and British Airways. These ELT issues are still considered unrelated to the lithium-ion battery defects which caused the worldwide grounding back in January.