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ET 787 On Fire At Heathrow Part 6

Fri Jul 19, 2013 12:20 am

Hello All,

The previous thread has gotten quite large so Part 6 is being created in order to further the conversation.

Part 5 can be found here ET 787 On Fire At Heathrow Part 5 (by moderators Jul 16 2013 in Civil Aviation)

Please remember the Airliners.net forum rules when posting. Posts found in violation of the rules will be removed.

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BEG2IAH
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RE: ET 787 On Fire At Heathrow Part 6

Fri Jul 19, 2013 12:42 am

To repeat, the AAIB published a special bulletin:

Special Bulletin S5/2013 - Boeing 787, ET-AOP
S5-2013%20ET-AOP.pdf" target="_blank">http://www.aaib.gov.uk/cms_resources/S5-2013%20ET-AOP.pdf
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Stitch
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RE: ET 787 On Fire At Heathrow Part 6

Fri Jul 19, 2013 1:00 am

To summarize the AAIB report, the source of the fire was in the area of the Emergency Locator Transmitter [ELT] and the ELT was the only device in the area that could provide a source of stored energy capable in initiating a fire. The lithium-manganese dioxide batteries in the ELT suffered damage, but it is unknown if the batteries themselves initiated the fire or if they were damaged by an external mechanism such as an electrical short. If there was a short that damaged the batteries, they could have initiated the fire. There is extensive heat damage to the upper portion of the rear fuselage with thermal damage to the insulation and structure - reported to be paint peeling and damage to the composite structure.

The ELT is self-powered. It does not receive any power from the 787's electrical system, though there is signaling wiring to the ELT. The 787 was connected to a ground power outlet at the time, but power to the outlet had been shut off. The batteries are tested on an annual basis and have a 10-year shelf life. There have been no reports of an ELT battery failing in such a way as to initiate a fire. Nonetheless, the AAIB has recommended ELTs be removed from the 787 fleet until an AD can be determined and implemented and an examination of their installation on other aircraft be performed by the FAA.

[Edited 2013-07-18 18:08:26]
 
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golfradio
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RE: ET 787 On Fire At Heathrow Part 6

Fri Jul 19, 2013 1:21 am

Quoting Stitch (Reply 2):
The ELT is self-powered. It does not receive any power from the 787's electrical system, though there is signaling wiring to the ELT

How is the battery charged if it is not connected to the aircraft's bus?
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WestWing
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RE: ET 787 On Fire At Heathrow Part 6

Fri Jul 19, 2013 1:25 am

Quoting Stitch (Reply 2):
the AAIB has recommended ELTs be removed from the 787

The phraseology was a recommendation to "make [the ELT] inert". I guess for a device with batteries that cannot be removed, the only way to achieve "inertness" is to remove the ELT in toto?
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RE: ET 787 On Fire At Heathrow Part 6

Fri Jul 19, 2013 1:26 am

Quoting Stitch (Reply 2):
There is extensive heat damage to the upper portion of the rear fuselage with thermal damage to the insulation and structure - reported to be paint peeling and damage to the composite structure.

Does anyone know if the fuselage was breached as extensively as the photo's depict?

I'm just scanning though the report for a second time, but unless I missed a section on the first read though I can't recall it going into detail regarding the damage.
 
KELPkid
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RE: ET 787 On Fire At Heathrow Part 6

Fri Jul 19, 2013 1:29 am

Finally!

I was waiting fo the mods to start a new thread...

Now, according to the report:

"Surveying and detailed examinations of damaged areas revealed that the greatest heat damage and highest temperatures were centered on the rear fuselage close to the crown and displaced to the left of the aircraft centre (sp?) line. This corresponds to the most damaged external areas, with blackened and peeling paint and damage to the composite structure. It also coincides with the location of the aircraft's Emergency Locator Transmitter (ELT) and its associated system wiring which is mounted internally on the structure close to the aircraft skin. There are no other aircraft systems in this vicinity which, with the aircraft unpowered, contain stored energy capable of initiating a fire in the area of heat damage."

This means:
1). No burn through. There were no holes on the exterior of the aircraft (as per a.net speculation...).
2). If something started burning, it did so at least ~10 hours earlier. Nothing on the plane was able to initiate a fire, other than perhaps the ELT (by way of its battery).

The report confirms that ground power was disonnected. I'm sure they checked the airframe to confirm that the master switch wasn't accidentally left on  
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KELPkid
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RE: ET 787 On Fire At Heathrow Part 6

Fri Jul 19, 2013 1:31 am

Quoting golfradio (Reply 3):
How is the battery charged if it is not connected to the aircraft's bus?

It has a factory charge which is supposed to last approximately 10 years on the shelf (with regular testing intervals)... My guess is it isn't actually rechargeable, and is more akin to a dry cell battery, where once the charge is gone, the battery is discarded.
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RE: ET 787 On Fire At Heathrow Part 6

Fri Jul 19, 2013 1:32 am

Quoting golfradio (Reply 3):
How is the battery charged if it is not connected to the aircraft's bus?

They are not rechargeable. They are disposable. So after 10 years (or should they fail a test), you replace them with new ones.
 
Sgarr
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RE: ET 787 On Fire At Heathrow Part 6

Fri Jul 19, 2013 1:33 am

This is a little out there, but is it conceivable there could be issues related to accumulated static charge creating a large potential between the aircraft hull and whatever the reference ground is for the electronics? If so perhaps a discharge through the ELT antenna kicked off the battery failure. Like I said, the idea seems far fetched, but so do other proposed causes.
 
BEG2IAH
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RE: ET 787 On Fire At Heathrow Part 6

Fri Jul 19, 2013 1:42 am

Quoting Daysleeper (Reply 5):
I'm just scanning though the report for a second time

You make it sound like the report is 300 pages long when it's only 3.  
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flood
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RE: ET 787 On Fire At Heathrow Part 6

Fri Jul 19, 2013 1:47 am

Quoting Daysleeper (Reply 5):
Does anyone know if the fuselage was breached as extensively as the photo's depict?

There apparently was no breach. The AAIB report which made no mention of such and Ostrower, citing a source familiar with the investigation, reported the fire didn't burn through the fuselage.
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RE: ET 787 On Fire At Heathrow Part 6

Fri Jul 19, 2013 2:08 am

Quoting Sgarr (Reply 9):

I thing you are looking way to far. Chasing fantom gremlims.
We can suggest many different theories here on A.net yet there were actual professionals on board looking at what actually took place.
The statement by the authorities are pretty difinitive.

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TheRedBaron
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RE: ET 787 On Fire At Heathrow Part 6

Fri Jul 19, 2013 2:10 am

My post got lost on the other thread, so I reported it here sorry for the format...


Quoting 2175301 (Reply 279):
Since the ELT only emits power to the antenna if it has been triggered (and no one has reported that the ETL went into transmit mode); and should not emit any power to any of the other wires connected to the ELT from the 787 - that would indicate that something had to fail inside the ELT for power to be applied to those wires. Now, given some kind of failure inside the ELT it may be possible that a short outside the ELT also occurred which could then be the source of the fire. But, it is just as likely that if there was a short that it was inside the ELT itself with the resulting start of the fire occurred inside the ELT. The AAIB has not said where any potential short was (or most likely was) - and is continuing the investigation in the hopes of sorting this out.

Correct and let me add some pertinent questions: Does the battery inside the ELT has enough energy (joules) to generate the heat and subsequent ignition-fire...

Quoting hivue (Reply 285):
Yes, it sounds like the AAIB has yet to determine where any putative short was. A third possibility is a defective battery that overheated spontaneously.

If the Battery overheated, man this Airplane does need some exorcising, ther have been lot of those units on other aircraft and it happens in a 787 for God´s Sakes? Bad Luck?

Quoting Daysleeper (Reply 291):
I just find it incredibly hard to believe that the ELT is solely responsible for this incident, if that's writing off possibility's then yes, guilty as charged.

I find it hard to believe and if it was the real cause, those ELT are badly designed...

Quoting Klaus (Reply 294):
Battery fires are usually not fed by atmospheric oxygen but by the components of the battery itself – that is why they're so hard to extinguish.

These fires are basically the result of the charge of the battery not being turned into electical energy as it should be normally, but instead into thermal energy.

How much energy conversion does that battery has to cause so much damage....??? good question dont you think KLaus?

Quoting Klaus (Reply 314):
At least MacBooks have built-in microcontrollers in each removable battery pack plus at least one in each computer which do in fact keep track of the charging history (both current charging state and global charging / discharging cycles), computer state and so on. They are always powered as long as the power cord is connected (desktop Macs) or battery power is available (MacBooks).

It is absolutely feasible to have a similar facility in an airliner, fed by the standby/battery buses and keeping track of power usage even in the absence of ground or generator power.

Great Observation, if a Macbook of 1000 USD$ has microcontroller protection, why a multimillion aircraft lacks it?

Quoting Finn350 (Reply 318):
The AAIB report ALMOST says the following:

The aircraft Emergency Locator Transmitter (ELT) initiated fire (because it is the only system which contains stored energy capable of initiating fire with aircraft unpowered in the vicinity of the area of the heat damage ).

They have facts and they have to use logic and place the blame on the component that is near the damage and has enough energy to cause such damage... they suspect the ELT and have made recommendations, but if the remove the components on other 787 and we have another "event" what THEN?

Does somebody know how many different batteries the 787 has? because maybe they need to check all of them... just sayin´

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Daysleeper
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RE: ET 787 On Fire At Heathrow Part 6

Fri Jul 19, 2013 2:18 am

Quoting BEG2IAH (Reply 10):
You make it sound like the report is 300 pages long when it's only 3

I hate it when a document has multiple columns per page, I always manage to a section no matter how long or short the document is. I've never quite understood why the format is still used outside of a newspaper.
 
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RE: ET 787 On Fire At Heathrow Part 6

Fri Jul 19, 2013 2:30 am

Quoting KELPkid (Reply 6):
"Surveying and detailed examinations of damaged areas revealed that the greatest heat damage and highest temperatures were centered on the rear fuselage close to the crown and displaced to the left of the aircraft centre (sp?) line.

It's from England. Of course it is spelled "centre"!
 
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RE: ET 787 On Fire At Heathrow Part 6

Fri Jul 19, 2013 2:36 am

Quoting TheRedBaron (Reply 13):
Great Observation, if a Macbook of 1000 USD$ has microcontroller protection, why a multimillion aircraft lacks it?

I can think of a couple of reasons: One is the need to certify that circuitry, and whatever software is embedded within it. Here's a problem that people are running into when they try to build avionics with off-the-shelf components: In order to get the hardware and/or software certified, you need access to design information and source code, and also to process documentation from the development process. In a lot of cases, for COTS components, the process documentation is lacking or doesn't exist at all, and the vendor has no interest in releasing their intellectual property for the purpose of certification. They look at and say, "We might sell 1000 of these to the avionics market, but we can sell 10 million of them to the phone manufacturers. So if we have to go out of our way even a little bit for the avionics market, screw it."

The other problem with the COTS battery manager is that they have a nasty habit of shutting off the battery when they *think* the charge is sufficiently depleted. We've all had the experience with laptops and tablets and so forth, that when the battery starts to age a bit, the available time on a battery charge drops abruptly. Transient conditions can trick those battery manager controllers into thinking the battery capacity has been greatly reduced. Obviously this is not what you want with an ELT; if and when the battery is needed for its intended purpose, you want that damn thing to keep discharging down to the last electron.
 
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Stitch
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RE: ET 787 On Fire At Heathrow Part 6

Fri Jul 19, 2013 2:38 am

Quoting TheRedBaron (Reply 13):
Great Observation, if a Macbook of 1000 USD$ has microcontroller protection, why a multimillion aircraft lacks it?

It's irrelevant in the case of the ELT battery since it is not rechargeable.
 
Klaus
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RE: ET 787 On Fire At Heathrow Part 6

Fri Jul 19, 2013 2:39 am

Quoting Sgarr (Reply 9):
This is a little out there, but is it conceivable there could be issues related to accumulated static charge creating a large potential between the aircraft hull and whatever the reference ground is for the electronics? If so perhaps a discharge through the ELT antenna kicked off the battery failure. Like I said, the idea seems far fetched, but so do other proposed causes.

Shouldn't happen, since signal reference ground should be connected to the fuselage (embedded mesh in this case).

And the ground power connector should also have tied the whole system to actual ground, even while the actual power supply remained switched off according to the engineer.

Quoting billreid (Reply 12):
The statement by the authorities are pretty difinitive.

Not this one – this is very clearly and explicitly just a provisional "Special Bulletin".

It draws no definitive conclusions at all.

Quoting TheRedBaron (Reply 13):
How much energy conversion does that battery has to cause so much damage....??? good question dont you think KLaus?

About as much as the electrical charge it can hold. Depends on circumstances and the chemical makeup.

An important variable dependent on the construction of the battery is the speed and thus violence of a battery failure (the cobalt-based Li-Ion main batteries are pretty much at the top of that ranking).

Quoting TheRedBaron (Reply 13):
Great Observation, if a Macbook of 1000 USD$ has microcontroller protection, why a multimillion aircraft lacks it?

I don't say it does – it's quite possible the 787 have permanent power monitoring facilities built in. It would be quite a bit more complex for an airplane than for a notebook computer, though.

Active power monitoring should be present in any case – it's necessary for safe operation to keep track of how much power is consumed where and to kick off some less critical consumers (load shedding) when power supply is strained (for instance when some of the generators go offline).

Quoting Stitch (Reply 17):
It's irrelevant in the case of the ELT battery since it is not rechargeable.

That's not the point – if the ELT (or a related component) should have been cooked with power from the main supply due to a short, such fault currents would most likely turn up in the log of a power monitor.

[Edited 2013-07-18 19:43:30]
 
hivue
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RE: ET 787 On Fire At Heathrow Part 6

Fri Jul 19, 2013 3:35 am

Haven't seen this posted yet from Reuters:
http://finance.yahoo.com/news/dreaml...robe-focuses-beacon-174527528.html

"Boeing's new plane has a relatively high humidity, which helps keeps (sic) passengers more comfortable, and investigators are now looking at whether there is enough insulation to prevent moisture from condensing and short circuiting systems such as the beacon, said the source, who was not authorized to speak publicly.

"A source close to Boeing, speaking on condition that he not be named, said the 787 may need better isolation of electrical components from the plane's high humidity, something industry people refer to as 'rain in the plane.'"
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Stitch
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RE: ET 787 On Fire At Heathrow Part 6

Fri Jul 19, 2013 4:01 am

Quoting Klaus (Reply 18):
That's not the point – if the ELT (or a related component) should have been cooked with power from the main supply due to a short, such fault currents would most likely turn up in the log of a power monitor.

But based on the post of an employee of a 787 operator, it appears the ELT is not near any power conduits. So could such an event happen? Does anyone know the voltage and current of the wires that are connect the ELT to the cockpit?


The condensation issue is an interesting one. Is the ELT installed underneath the fuselage or in a blister on top?
 
airtechy
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RE: ET 787 On Fire At Heathrow Part 6

Fri Jul 19, 2013 4:09 am

As I said in an earlier post, the ELT is mounted directly under it's antenna in the upper fuselage. You want the antenna to be on top so it can radiate and you want the connection to the antenna to remain intact if the airplane gets torn apart in a crash.

AT
 
KELPkid
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RE: ET 787 On Fire At Heathrow Part 6

Fri Jul 19, 2013 4:32 am

Quoting hivue (Reply 19):
"Boeing's new plane has a relatively high humidity, which helps keeps (sic) passengers more comfortable, and investigators are now looking at whether there is enough insulation to prevent moisture from condensing and short circuiting systems such as the beacon, said the source, who was not authorized to speak publicly.

"A source close to Boeing, speaking on condition that he not be named, said the 787 may need better isolation of electrical components from the plane's high humidity, something industry people refer to as 'rain in the plane.'"

Well, the crown of an aircraft, baking in the sun, on a hot afternoon is not exactly a condusive environment for condensation to form...
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gators312
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RE: ET 787 On Fire At Heathrow Part 6

Fri Jul 19, 2013 4:52 am

Could a lightning strike in flight to the ELT antenna have begun the thermal runaway of the battery inside the ELT?
 
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seahawk
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RE: ET 787 On Fire At Heathrow Part 6

Fri Jul 19, 2013 5:40 am

It must be some kind of special bad luck, when on a new auirplane you get thermal events on 3 different batteries in 3 different incidents.
 
Ruscoe
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RE: ET 787 On Fire At Heathrow Part 6

Fri Jul 19, 2013 6:25 am

Currently the two things I find most interesting are;

1. Boeing is saying that the ELT is a customer option item

and

2. The AAIB is recommending to the appropriate authorities that all Lithium based batteries in ELT's be looked at, which obviously includes a lot of aircraft from all manufacturers

Ruscoe
 
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speedbored
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RE: ET 787 On Fire At Heathrow Part 6

Fri Jul 19, 2013 6:38 am

Hi from a long-time lurker who's not previously been allowed to post due to contractual obligations working for an employer paranoid about protecting client confidentiality. Now that I am semi-retired, however, it's probably time to start contributing. Here's hoping I don't live to regret it.  

Just for the record, I would like to point out that I am neither an Airbus fanboy nor a Boeing fanboy. I am simply interested in aviation, regardless of manufacturer, having worked in and around the industry for just over 25 years.

Having read the AAIB special bulletin very carefully, the only definitive conclusion that I've been able to come to based on it is that there was a fire on an Ethiopian 787 at Heathrow (which I knew already). It seems to me that many people are reading a lot more into the bulletin than is actually there. What we all need to bear in mind is that the AAIB press release and special bulletin are both very very carefully worded so as to avoid drawing any conclusions at all at this stage. The investigators are keeping their minds open and so should we.

For example, the holes in the fuselage question. The AAIB simply says that there is "damage to the composite structure". So this damage may or may not include holes penetrating the skin. The fact is we simply don't know at the moment. I have to admit that from the public images I have seen, I struggle to see how some of the very black patches can be anything other than holes, but I'm content to wait for more information from the AAIB to find out for sure.

Then there's the source of the fire. It seems that a lot of people are reading the AAIB bulletin as saying that it started in the ELT battery, either caused by a fault in the ELT itself or as a result of an external short. I would agree that is what it infers if the fire started while the aircraft was "unpowered". But the inclusion of the "with the aircraft unpowered" statement in this part of the bulletin suggests to me that the AAIB are still entertaining the possibility that the fire could have started while the aircraft was "powered", so the energy to start the fire could have come from elsewhere. I know that it's been stated very firmly by some people that there are no power cables to the ELT, so the energy could not have come from elsewhere, but there are 4 (or was it 3?) data cables connecting to the ELT and a data cable will become a power cable if you apply power to it. Perhaps there was a fault in the flightdeck control panel or a data concentrator, or a short between a data cable and a nearby power cable or one of the many connectors somewhere en-route.

I'm of the opinion that it's entirely plausible that the fire could have started a long time before it was noticed by the control tower, possibly even while external power was still on, many hours earlier. There are a lot of flame resistant (as opposed to flameproof) materials on an aircraft and many of these can smoulder for a very long time before sufficient heat builds up to sustain a proper fire.

So, again, I think we need to keep an open mind on the source of the fire until we get more information. The AAIB certainly seems to be doing so: "Detailed examination of the ELT and the possible mechanisms for the initiation and sustaining of the fire in this aircraft continues."

The rumour about condensation is interesting. My understanding of condensation is that it mostly forms at altitude in the form of ice on the inner skin of the aircraft which then melts after landing to form the water that gets blown around by the aircon or tipped out of the ceiling panels on take-off. Certainly seems plausible that ice could have formed in or around the ELT at altitude, or in or around any of the cable bundles and connectors, causing a short when it later melted. Perhaps water running down cable bundles into the power panels or other electronics could explain some of the other issues that have occurred. Might explain why the culprit has been hard to find - it evaporated.

The thing that I find most interesting in the special bulletin, however, is the safety recommendations. I'm surprised that noone else has picked up on it yet but I suspect that Boeing might be more than a little concerned about the fact that the AAIB is only recommending inerting the roughly 1% of these ELTs that are installed on 787s. Without wanting to jump to any unwarranted conclusions, I can't help wondering why, if the AAIB has concluded that the ELT is a risk, they have not also recommended that all 6000 of them are inerted on every aircraft type. Why do the other 99% only warrant a "safety review"? Food for thought.

Personally, I'm keeping an open mind as to whether or not there's any underlying systemic issue with the 787. With the small number of incidents so far, and the lack of confirmed information as to their underlying causes, it's impossible to be certain one way or another right now. Could be a problem with the system or could just be bad luck. But it sure is fun reading all of the discussions about it in the very many threads.
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Pellegrine
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RE: ET 787 On Fire At Heathrow Part 6

Fri Jul 19, 2013 6:46 am

Quoting Speedbored (Reply 26):

Thank you! This was my point earlier...the AAIB bulletin does not say anything of note. I am a lover of the aviation industry overall... It is very hard to believe an ELT battery produced enough sustained power to initiate this damage. It's like a smoke detector burning down a house.
oh boy, here we go!!!
 
Flyglobal
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RE: ET 787 On Fire At Heathrow Part 6

Fri Jul 19, 2013 6:48 am

I don't believe so much in bad luck.

Having seen electronic devices behavior different depending on environment and built in conditions in car industrie, my engineering experience tells me that it may have to do something in with the speific built in / environment conditions in the 787.
So any failure analysis I would start with: Lets check what is different and probably unique in the 787 to other airplanes.

Starting:
1) Composite instead of metal
2) Humidity higher then all other planes before.
3) Ventilation situation around the ELT ower then in other planes?

Special conditions at the day of incidence:
Very high otside temperatures
Probably humidity left when the plane was sent to parking position?

Make a Lab test with the 787 conditions inside the plane as expected:
Humidity and tempereture - 8h in the burning sun? getting the battery to about 60°C +? In humidity of ??.

Anyhow again: My engineering brain and gutt feeeling points me to this.

regards

Flyglobal
 
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Finn350
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RE: ET 787 On Fire At Heathrow Part 6

Fri Jul 19, 2013 7:20 am

Quoting Speedbored (Reply 26):
I can't help wondering why, if the AAIB has concluded that the ELT is a risk, they have not also recommended that all 6000 of them are inerted on every aircraft type

Well written post. And the recommendation regarding the safety review of ELTs installed in other aircraft types covers ALL Lithium-powered ELTs, not just those manufactured by Honeywell.

The AAIB report is quite clear on ELT being the initiator of the fire (only "loopholes" mentioned are if the aircraft was powered, fire started when the aircraft was powered, or fire started outside the area of the heat damage, which all sound quite implausible).

The report specifies two different possible initiators to the combustion: either the ELT battery itself or an electrical short powered by the ELT battery (and leaves open there might be other initiators besides an electrical short in case of an external mechanism to ELT). What I find hard to see how an electrical short among the few cables that come out of the ELT could lead to an ignition, no matter how you short those cables.

Regarding the root cause, the AAIB report does not speculate at all on that.
 
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speedbored
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RE: ET 787 On Fire At Heathrow Part 6

Fri Jul 19, 2013 7:31 am

Quoting flyglobal (Reply 28):

I can't see it being temperature - Lithium Manganese Dioxide batteries are usually rated to at least 60°C so I doubt that there would be any likelihood of temperature causing spontaneous combustion until well over 90°C. And there are loads of these batteries in ELTs on top of aircraft operating from far hotter airports than Heathrow, and with darker bodywork, with no issues.

I agree that the humidity/condensation issue probably warrants further investigation but, as has been stated by others earlier, there have been many instances of water flowing from ceilings in other aircraft without it causing issues. Is there something very different about the way wiring and connections are done in a 787?

Composite instead of metal? That's one area where I think there could be issues. Previous metal aircraft have relied on the aircraft structure to provide a common earth for the electrics and electronics. Obviously, this isn't possible with non-conducting composite, which is why Boeing have added a metal mesh to the structure. I can't help wondering whether something went wrong with the earthing of the ELT. I do not know how Boeing ensures that the electrical earth is properly connected but if they are relying on rivets or bolts making contact with a mesh at some point, I can see how it may have failed to connect, especially if the ELT has been removed and replaced at some point. If improperly earthed, the ELT antenna would be ideally placed to build up a significant static charge, given its location sitting out there in the slipstream. And the only way for that charge to discharge itself would be via the electronics and data cables, which could cause trouble.
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LTC8K6
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RE: ET 787 On Fire At Heathrow Part 6

Fri Jul 19, 2013 7:31 am

Why would there be high humidity when it's parked? The "high humidity" for pax is when the plane is flying, provided by the aircon system.

The "high humidity" in the 787 is something like 15% at a cabin altitude of 6K feet, just like the newest airbuses, iirc.

So it's hardly what you'd call high humidity, if you weren't in an airplane.
 
RedChili
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RE: ET 787 On Fire At Heathrow Part 6

Fri Jul 19, 2013 7:40 am

Quoting Speedbored (Reply 26):
Hi from a long-time lurker who's not previously been allowed to post due to contractual obligations working for an employer paranoid about protecting client confidentiality. Now that I am semi-retired, however, it's probably time to start contributing. Here's hoping I don't live to regret it.

  

One of the best posts so far in this entire discussion!
Top 10 airplanes: B737, T154, B747, IL96, T134, IL62, A320, MD80, B757, DC10
 
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speedbored
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RE: ET 787 On Fire At Heathrow Part 6

Fri Jul 19, 2013 7:41 am

Quoting Finn350 (Reply 29):
The AAIB report is quite clear on ELT being the initiator of the fire (only "loopholes" mentioned are if the aircraft was powered, fire started when the aircraft was powered, or fire started outside the area of the heat damage, which all sound quite implausible).

I agree that the report seems to be hinting very strongly at the battery being the source (though not necessarily the cause) of the fire. But the AAIB is deliberately avoiding saying so as there are still many other possibilities to discount, however implausible they might be.

Quoting Finn350 (Reply 29):
What I find hard to see how an electrical short among the few cables that come out of the ELT could lead to an ignition, no matter how you short those cables.

I also fail to see how shorting out two data cables could cause a problem. It probably happens many times a day in offices all over the world without problems. I'm guessing that they are suggesting the possibility of a short between one of the data cables and some other cabling with a bit more oomph.
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RE: ET 787 On Fire At Heathrow Part 6

Fri Jul 19, 2013 7:47 am

Quoting RedChili (Reply 32):
One of the best posts so far in this entire discussion!

Well, thank you.

One lesson I learnt many many moons ago was to engage brain before speaking (or typing these days). Sadly, it seems to be a lesson that quite a few people who post here have yet to learn.
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RE: ET 787 On Fire At Heathrow Part 6

Fri Jul 19, 2013 7:48 am

I am not sure if we can be sure that the ELT started the fire. Obviously the battery can be a source of flamable material to keep a fire going, but is it strong enough to work through its containment and then ignite flame resistant materials? This would the third battery containment failure in the 787. My gut says, this is unlikely to be bad luck.

[Edited 2013-07-19 01:31:24]
 
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RE: ET 787 On Fire At Heathrow Part 6

Fri Jul 19, 2013 8:00 am

Quoting seahawk (Reply 35):
I am not sure if we can be sure that the ELT started teh fire.

I agree, we can't. But we also can't be sure that it didn't.

The only thing we can be sure of is that we're not sure.
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Faro
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RE: ET 787 On Fire At Heathrow Part 6

Fri Jul 19, 2013 8:07 am

Is the following understanding re the 787 incidents accurate:

- The exact cause of the JL/NH 787 battery thermal runaway is not known with 100% certainty but the measures taken to contain any such occurence in the future are sufficient to meet regulatory safety requirements; and

- The exact cause of the ET 787 rear fuselage crown fire is not known with 100% certainty but the measures which may be envisaged to prevent any such occurence in the future (presumed source of fire = ELT => removal of the ELT) would be sufficient to meet regulatory safety requirements.

If this is correct, I would imagine that Boeing engineers are looking very very hard at the the design -if not design philosophy- of the underlying 787 electrical system to ensure that it does not harbour an unknown, systemic risk...

One more electrical-related problem with the 787 and we may see more drastic measures taken by both Boeing and the regulators than a formal investigation...


Faro

[Edited 2013-07-19 01:43:53]
The chalice not my son
 
sankaps
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RE: ET 787 On Fire At Heathrow Part 6

Fri Jul 19, 2013 8:30 am

Quoting flyglobal (Reply 28):
Special conditions at the day of incidence: Very high otside temperatures

I think this is more of a red herring.... the high in London that day was around 30-31C -- hot for London maybe, but positively mild relative to places like Dubai, Doha, Delhi, Dallas where 787s and other ELT-equipped aircraft freely operate. Temperatures in those places can get to 45C or higher.

Quoting Speedbored (Reply 30):
I can't see it being temperature - Lithium Manganese Dioxide batteries are usually rated to at least 60°C so I doubt that there would be any likelihood of temperature causing spontaneous combustion until well over 90°C. And there are loads of these batteries in ELTs on top of aircraft operating from far hotter airports than Heathrow, and with darker bodywork, with no issues.

Exactly.

[Edited 2013-07-19 02:01:11]
 
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RE: ET 787 On Fire At Heathrow Part 6

Fri Jul 19, 2013 9:29 am

I find all these posts that say

Quote:
I can't believe that the ELT battery could start a fire

laughable.

There is enough energy in a small chemical battery to start a fire. It's a fact and there are documented cases of this happening in all kinds of device. People who say that even a "cheap" iPhone has protection against it don't know what they are talking about. Yes, most electronic devices have protection circuits to prevent overcharge, short circuits, etc. And every day these types of circuits fail. $hit happens. Just Google "iPhone on fire" and you will find dozens of examples of iPhones that have burned spontaneously. And iPads. And Blackberries. And many other phones, computers, etc. The only difference is that when an iPhone burns, nobody talks about. An ELT in an airplane catches fire and it's front page news.

People love conspiracy theories and will disregard any evidence that contradicts their beliefs. People believe all kinds of stupid things. 40% of the people in the US do not believe in evolution, in spite of overwhelming evidence. Many believe that the Earth is 6000 years old. And many will believe that B787 is unsafe. You just can't argue with idiots.

Sorry for venting, but being and engineer and scientist, who uses data and EVIDENCE as basis for my work every day, I am tired of people who argue "yes, the evidence is, but I BELIEVE ...". Stop BELIEVING and start REASONING.
 
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RE: ET 787 On Fire At Heathrow Part 6

Fri Jul 19, 2013 10:33 am

But if a fire sock is enough to contain a laptop battery, I wonder how the ELT (which must withstand 1100° for 2 minutes and still work) managed to cause a fire that was able to spread in an area made of fire retardent or resistent materials.
 
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RE: ET 787 On Fire At Heathrow Part 6

Fri Jul 19, 2013 10:43 am

Quoting seahawk (Reply 40):
But if a fire sock is enough to contain a laptop battery, I wonder how the ELT (which must withstand 1100° for 2 minutes and still work) managed to cause a fire that was able to spread in an area made of fire retardent or resistent materials.

The ELT is only required to prevent a fire from getting in for 2 minutes. As far as I'm aware, there is no requirement for it to withstand a fire trying to get out. I suspect that the pressure produced by a battery fire inside the ELT will easily breach whatever vessel is used to keep fire out.
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RE: ET 787 On Fire At Heathrow Part 6

Fri Jul 19, 2013 10:50 am

Quoting katekebo (Reply 39):
People love conspiracy theories and will disregard any evidence that contradicts their beliefs. People believe all kinds of stupid things. 40% of the people in the US do not believe in evolution, in spite of overwhelming evidence. Many believe that the Earth is 6000 years old. And many will believe that B787 is unsafe. You just can't argue with idiots.

Sorry for venting, but being and engineer and scientist, who uses data and EVIDENCE as basis for my work every day, I am tired of people who argue "yes, the evidence is, but I BELIEVE ...". Stop BELIEVING and start REASONING.

"There is none so blind as those who will not see"..............

I believe that this phrase is VERY pertinent in this situation. From BOTH sides - the 'Head in the Sanders' and the 'Sky is Fallingers'. The truth will out eventually. As you so elequently put above - evidence is the key. However, the current evidence is not categorical, no final recoomendations have been made, and the investigation is still ongoing. Therefore i find your 'vent' a little hypocritical - could you not level the same arguments to those who think that there is not an issue with the airplane?

Why do some people (on both sides) want to play judge, jury and executioner so badly??

Human nature? Payback? Bitterness? Who knows.
 
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RE: ET 787 On Fire At Heathrow Part 6

Fri Jul 19, 2013 10:56 am

Quoting ZB052 (Reply 42):
Human nature? Payback? Bitterness? Who knows.

Don't mess with holders of Boeing shares, here on a.net.  
Wer nichts weiss muss alles glauben
 
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RE: ET 787 On Fire At Heathrow Part 6

Fri Jul 19, 2013 11:02 am

Quoting katekebo (Reply 39):
There is enough energy in a small chemical battery to start a fire. It's a fact and there are documented cases of this happening in all kinds of device. People who say that even a "cheap" iPhone has protection against it don't know what they are talking about.

I'm sure there are more iPhones (not mentioning other consumer electronic devices) on every flight than there are ELTs, yet no iPhone in the cabin has caused such an extensive damage to a plane.

Of course you cannot compare consumer electronics with aviation components, but keep in mind that there are a few thousand ELTs with Lithium batteries that are used in very stable and predictable environments and then there are more than 100 millions of iPhones that are being used by the consumers in all kinds of ways imaginable in all kinds of places imaginable. Considering this I can accept that a few iPhones burn every now and then, but I cannot accept that an ELT ignites a fire in a plane in a way that makes AAIB write "had this event occurred in flight it could pose a significant safety concern and raise challenges for the cabin crew in tackling the resulting fire."
 
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RE: ET 787 On Fire At Heathrow Part 6

Fri Jul 19, 2013 11:11 am

Quoting Speedbored (Reply 41):
The ELT is only required to prevent a fire from getting in for 2 minutes. As far as I'm aware, there is no requirement for it to withstand a fire trying to get out. I suspect that the pressure produced by a battery fire inside the ELT will easily breach whatever vessel is used to keep fire out.

Yet is a fully enclosed aluminium case, that is carsh resistant, fire resistant, water proof and held together by screws. Add the fact that the type of batteries in the Honeywell ELT of the 787 is not only used in Honeywell ELTs on other aircraft, but also by Pointer ELTs too. (and probably many other) That is probably 10.000 units or more. And the first recorded thermal event happens in a 787. The same plane which had thermal events on other batteries, also enclosed in an aluminium case at the time those events happened. As an engineer I find that unlikely. Maybe condesation water could really be pointing into the correct direction, with the water collecting inside the aluminium cases and causing a short in the battery.
 
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RE: ET 787 On Fire At Heathrow Part 6

Fri Jul 19, 2013 11:40 am

Looks like that ELT uses 5 of these cells according to various web sites:

http://ultralifecorporation.com/be-m...oducts/cylindrical/U10013-CR34610/
 
sphealey
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RE: ET 787 On Fire At Heathrow Part 6

Fri Jul 19, 2013 11:58 am

Quoting FlyingAY (Reply 44):
I'm sure there are more iPhones (not mentioning other consumer electronic devices) on every flight than there are ELTs, yet no iPhone in the cabin has caused such an extensive damage to a plane.

Here's a link that will lead you to the FAA's guidelines and training materials for fighting a lithium battery fire in the cabin. It is a matter of some concern to both the FAA and NTSB given the rapid growth of lithium chemistry devices over the last 5 years:

http://www.faa.gov/other_visit/aviat...all_safos/media/2009/SAFO09013.pdf

sPh
 
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RE: ET 787 On Fire At Heathrow Part 6

Fri Jul 19, 2013 12:02 pm

While I'm linking things   Here's a calculator for estimating the fusing (melt-through) current for copper wire at various gauges. For 24 gauge solid wire (instrument wire) I get a 5-second melt-through current of ~29 amps.

http://www.cirris.com/testing/resistance/fuse.html

sPh
 
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RE: ET 787 On Fire At Heathrow Part 6

Fri Jul 19, 2013 1:09 pm

Quoting seahawk (Reply 45):
As an engineer I find that unlikely.

With the information available to me at present, I can't disagree with you or anyone else who says that it looks like there might be a systemic issue with the 787. But I'd also find it a bit difficult to disagree with anyone who claims the 787 is fine. I simply don't have enough information to be certain either way right now.

Personally, I don't feel that the 787 is significantly more dangerous than other aircraft but then I do have the luxury of not having any travel planned this year on routes served by the 787. Maybe I'd feel differently if I did, and I'm certainly not going to berate anyone for not wishing to "take the risk".

Given that the most recent event is different in a number of respects from the first two, it looks to me that the three fire or "fire-like" issues so far can just about be accommodated within the normal bounds of probability. Once-in-a-million-flight-hours doesn't have to mean that there will be a million event free hours before the first event, nor that there must be a million hours between the first and second events. Another event happening this year, however, might make the statisticians think twice.

Just for discussions sake, if we hypothetically assume that there is a systemic issue behind these events, what could possible causes be? Condensation has already been mentioned. I can think of a few others but without detailed designs, construction records and investigation results, cannot hope to even guess at how likely, or otherwise, they might be:

1) Electrical Earth Bonding.
I've been reading recently in other threads how Airbus are investing a lot of time and money in ensuring that the A350 has a good earthing skeleton, both for lightning protection and for earth bonding of the electrical systems. I presume that Boeing did the same during 787 development and I also assume that Airbus will have learnt many lessons from what Boeing has done. Unlike a metal plane where the earthing system gets joined up simply by assembling the aircraft, with a CFRP frame, there will necessarily be many points at which the various metal parts of the earth bonding skeleton need to be electrically connected together. I can't help wondering, however, why Airbus didn't include some CFRP into the iron bird to test electrical bonding during their system tests.

Aircraft are very good at building up static charges, and I suspect that plastic aircraft are even better at it. If any of the earth bonding connections are missing due to bad design, or mis-assembly (perhaps loose, or assembled with dirt in the connection) then there will be a very good possibility of high voltage static charges building up in some parts of the electrical system, which could then, when something switches on or off, be suddenly discharged via very unpredictable routes through sensitive equipment (electronics, maybe batteries), causing damage which could trigger events such as we've seen.

2) Voltage spikes.
It's no secret on Anet that Boeing might have made some mistakes on the outsourcing of the design and development of the electrical system. I get the impression that Boeing designed the system at a high level and then delegated the detailed design and development of individual parts of the system to many different contractors and subcontractors. I can't help wondering whether this might have led to the development that of lots of subsystems that work well in isolation but maybe have issues when interacting with one another.

In any electrical system with things regularly switching on and off, voltage spikes will be created by the switching, even when using solid-state switches. These spikes are usually smoothed out using accumulator devices such as capacitors or magnetic coils. As accumulator devices contain a lot of metal, they are heavy, so I can see why some of the subsystem developers might have taken the approach of "we'll assume that the signals and power that we get will be smooth" to keep the weight of their own sub-assemblies down. i.e. assume it's someone else's problem to smooth out the spikes. And, as Boeing only concerned themselves with the high level design, maybe they didn't pay much attention to this until it was too late. Or maybe any spikes they found during testing were insignificant enough to not cause damage. Perhaps the spikes only get sufficiently large to cause damage when a flap motor, a toilet flusher, an oven and a coffee pot all switch off at the same time. So perhaps it was the coffee pot's fault after all.  

And finally, as they say on the other side of the pond, the "curveball". I suspect that I'll probably get laughed at for this one but I don't think it's completely outside the realms of possibility, so bear with me on this:

3) Vibration.
And I'm not talking the sort of vibrations the aircraft manufacturers try to get rid of during flutter testing. I'm talking about the low level "humming" type vibrations caused by the engines or A/C power buses.

After the first battery meltdown, and seeing how the battery was constructed, I couldn't help wondering whether sudden shocks or vibrations might cause the electrodes or electrolyte to move around within the battery, and possibly cause a short. I then got wondering about the difference between aluminium and CFRP in terms of absorption of low level vibrations. My guess is that metal, being softer, will absorb more of the vibrations than CFRP which, being more rigid, probably passes on the vibrations to be absorbed by softer materials elsewhere like seat cushions, bodies or battery electrolyte, perhaps?


Would be interested to hear what other people's thoughts are.
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