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FlyingAY
Posts: 416
Joined: Thu Jun 21, 2007 2:26 pm

RE: FAA Grounds 787 Part 3

Mon Jan 21, 2013 12:29 pm

Quoting airmagnac (Reply 193):
Exactly ! But that does not mean the containement failed in the 2 actual incidents

Fair enough. You were pointing out earlier that there might be differences how we interpret English language. I interpret this in a way that "resulted in release of flammable electrolytes, heat damage, and smoke" means that damage was done or it could have been done to systems or structure outside the container and that FAA is concerned about this and that in certain conditions that kind of release of flammable electrolytes might cause critical damage ("These conditions, if not corrected, could result in damage to critical systems and structures, and the potential for fire in the electrical compartment"). You might interpret this in another way.

If FAA thinks that the current situation is unsafe and warrants for grounding of the plane, I'd expect that either
1) The container failed.
2) The container did not fail, but the certification requirements were not strict enough since the resulting situation was anyway unsafe.

Note that I'm using the word unsafe as a synonym to the "conditions, if not corrected, could result in damage to critical systems and structures, and the potential for fire in the electrical compartment".
 
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Aquila3
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RE: FAA Grounds 787 Part 3

Mon Jan 21, 2013 12:34 pm

Quoting WingedMigrator (Reply 178):
Sure you do: you've had one event per N flight hours. You have a rate from that, albeit with a wide confidence interval. Two observations will give you a tighter confidence interval, three even more, etc.

I beg to disagree.
one event only demonstrates that P(x) >0.
That was already assumed, of course.
You cannot infer (deduce statistics) about P(x) on that.
 
kalvado
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RE: FAA Grounds 787 Part 3

Mon Jan 21, 2013 12:35 pm

Quoting tdscanuck (Reply 174):

It's not about demonstrated effect on safety of flight, it's about demonstration of compliance with regulations. There are lots of ridiculous regulations that you still have to comply with, even if they have no direct bearing on safety of flight.

Just out of curiosity - can you give an example of such "ridiculous regulation"?
As for me, I like an example of a perfectly ridiculous regulation, which has quite a bit of logic behind once you dig deeper:
NYS requires cars to turn headlights on when windshield wipers are in use.
Logic: Wipers are on when weather is such that visibility is reduced. In such low visibility conditions oncoming cars would be much more visible with headlights on, reducing probability of an accident. Just a funny way of establishing a quite reasonable requirement, if you will.
 
PlaneInsomniac
Posts: 423
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RE: FAA Grounds 787 Part 3

Mon Jan 21, 2013 1:08 pm

Quoting KC135Hydraulics (Reply 190):
But the material did not cause damage to any other major system. How was that a failure of the containment?
http://www.wordreference.com/definition/containment
http://www.wordreference.com/definition/contain
http://en.wiktionary.org/wiki/containment

So far the Downplay Crowd has worked on redefining the meanings of the words fire, smoke, safety - and now containment.

Which part of the dictionary will be rewritten next?
 
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breiz
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RE: FAA Grounds 787 Part 3

Mon Jan 21, 2013 1:12 pm

I hope every reader will take this as a joke, even if deemed a bad one.
The B787's batteries are produced by French company Thales.
A good conspiracy theory would be that Thales is the Trojan horse used to delay the B787 in favour of the A350    .

Now on a more serious note, to burn a battery you need a serious overload.
Such a overload is usually created by the electrical system to which the battery is connected, not by the battery itself.
The FAA's review of the architecture is therefore an appropriate move.
 
Cubsrule
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RE: FAA Grounds 787 Part 3

Mon Jan 21, 2013 1:18 pm

Quoting AeroWesty (Reply 159):
But there's a bigger picture here: The complexity of this problem is also raising questions about whether the F-A-A is equipped to oversee such sophisticated technology.

This is a fairly common mainstream media criticism of regulators when they are dealing with new technology. It's hardly ever fair, and to the extent that FAA lacks knowledge about the technology, they can look to other parts of the government for help (probably NASA or the Department of Energy).

Quoting DocLightning (Reply 165):
Darned right it should be grounded. The only "mishandling," if any, was that it took the FAA until the next day to ground it.

You are reading quite a bit in to the statement that was not there. The grounding isn't over yet, and I think it far more likely that folks will criticize FAA for how and when it ends than for how and when it began.

That said, if the discussions in the Japanese media about these batteries coming from a single batch turn out to be accurate, there's probably an argument to be made that the grounding of the whole fleet has already gone on too long.
 
Kaiarahi
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RE: FAA Grounds 787 Part 3

Mon Jan 21, 2013 1:33 pm

For information, the actual text (from the Federal Register) of the conditions for design / installation / use of Li-Ion batteries in the 787.

WARNING: Terms such as "extremely remote", "explosion", "self-sustaining", "failure", "major or more severe failure condition", are technical terms that have a precise definition in the regulations. Wikipedia meanings are irrelevant.

"In lieu of the requirements of 14 CFR 25.1353(c)(1) through (c)(4), the following special conditions apply. Lithium ion batteries on the Boeing Model 787-8 airplane must be designed and installed as follows:

(1) Safe cell temperatures and pressures must be maintained during any foreseeable charging or discharging condition and during any failure of the charging or battery monitoring system not shown to be extremely remote. The lithium ion battery installation must preclude explosion in the event of those failures.

(2) Design of the lithium ion batteries must preclude the occurrence of self-sustaining, uncontrolled increases in temperature or pressure.

(3) No explosive or toxic gases emitted by any lithium ion battery in normal operation, or as the result of any failure of the battery charging system, monitoring system, or battery installation not shown to be extremely remote, may accumulate in hazardous quantities within the airplane.

(4) Installations of lithium ion batteries must meet the requirements of 14 CFR 25.863(a) through (d).

(5) No corrosive fluids or gases that may escape from any lithium ion battery may damage surrounding structure or any adjacent systems, equipment, or electrical wiring of the airplane in such a way as to cause a major or more severe failure condition, in accordance with 14 CFR 25.1309(b) and applicable regulatory guidance.

(6) Each lithium ion battery installation must have provisions to prevent any hazardous effect on structure or essential systems caused by the maximum amount of heat the battery can generate during a short circuit of the battery or of its individual cells.

(7) Lithium ion battery installations must have a system to control the charging rate of the battery automatically, so as to prevent battery overheating or overcharging, and,

(i) A battery temperature sensing and over-temperature warning system with a means for automatically disconnecting the battery from its charging source in the event of an over-temperature condition, or,

(ii) A battery failure sensing and warning system with a means for automatically disconnecting the battery from its charging source in the event of battery failure.

(8) Any lithium ion battery installation whose function is required for safe operation of the airplane must incorporate a monitoring and warning feature that will provide an indication to the appropriate flight crewmembers whenever the state-of-charge of the batteries has fallen below levels considered acceptable for dispatch of the airplane.

(9) The Instructions for Continued Airworthiness required by 14 CFR 25.1529 must contain maintenance requirements for measurements of battery capacity at appropriate intervals to ensure that batteries whose function is required for safe operation of the airplane will perform their intended function as long as the battery is installed in the airplane. The Instructions for Continued Airworthiness must also contain procedures for the maintenance of lithium ion batteries in spares storage to prevent the replacement of batteries whose function is required for safe operation of the airplane with batteries that have experienced degraded charge retention ability or other damage due to prolonged storage at a low state of charge.

[Edited 2013-01-21 05:38:12]

[Edited 2013-01-21 05:39:02]

[Edited 2013-01-21 05:40:44]
 
BlueShamu330s
Posts: 2584
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RE: FAA Grounds 787 Part 3

Mon Jan 21, 2013 1:34 pm

I have tried to wade through all the threads relating to the Dreamliner, but perhaps I have missed comments about a picture which appears in this link with the description "A Japanese investigator examines a scorched fuselage on an ANA plane."

http://news.sky.com/story/1040689/dr...amliner-fire-investigation-widened



I am curious to know whether this scorching is from the inside out or from venting, and how the event can have been considered contained if such external damage was inflicted. I apologise if it has already been covered or if I am coming across as being incredibly dim.

Could someone also educate me on CFRP's resilience to such an event and whether the fuse will require remedial work or simply nothing more than "a wipe down and polish."

Rgds
 
packsonflight
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RE: FAA Grounds 787 Part 3

Mon Jan 21, 2013 1:50 pm

Quoting Cubsrule (Reply 205):
That said, if the discussions in the Japanese media about these batteries coming from a single batch turn out to be accurate, there's probably an argument to be made that the grounding of the whole fleet has already gone on too long.

I dont buy this single batch story.

Apparently the two burned battery are 30 numbers apart, but how big is a batch?
Most likely there are not more than 150 batteries excisting in the world, being produced over more than 5 years. 100 of them sitting in the 50 787 flying and the rest somewhere in the supply chain and spare part houses around the world.

Those batteries have limited shelve life, so nobody wants to many of them sitting around, specially for something like 30-50,000$ a pop.
 
rheinwaldner
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RE: FAA Grounds 787 Part 3

Mon Jan 21, 2013 1:51 pm

Quoting nomadd22 (Reply 199):
No battery is going to have separate charging circuits for each cell, but they can have monitoring circuits for each cell.

Wrong. Even the most stupid charger for RC aviation which costs less than 50 bucks has a balancer. Check e.g. this device for roughly double that price:
http://www.graupner.de/fileadmin/dow...nleitungen/20060213144038_6414.pdf

The english section starts at page 16.

A balancer means, that beside measuring the voltage over each cell exactly, the charger applies differential currents in order to not overload a single cell. So as a result, each cell is treated seprately during charging.

We can safely assume that the 787 charger has a balancer, a cell temperature monitoring (I think it was confirmed by CM in an earlier thread) and normally also cell matching during battery production.

The problem is only, that this setup seems to not work properly. Something did not work as designed.

About the finding, that different reasons caused the two fires:
This is even worse, because the larger the number of actual issues, the larger the number of to be expected but still undetected flaws.
 
nm2582
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RE: FAA Grounds 787 Part 3

Mon Jan 21, 2013 2:30 pm

Quoting nomadd22 (Reply 199):
No battery is going to have separate charging circuits for each cell, but they can have monitoring circuits for each cell.

Quoting rheinwaldner (Reply 209):
Wrong. Even the most stupid charger for RC aviation which costs less than 50 bucks has a balancer. Check e.g. this device for roughly double that price:
http://www.graupner.de/fileadmin/dow...nleitungen/20060213144038_6414.pdf

The english section starts at page 16.

A balancer means, that beside measuring the voltage over each cell exactly, the charger applies differential currents in order to not overload a single cell. So as a result, each cell is treated seprately during charging.

A balancer circuit is NOT inherently the same as a separate charging circuit. The way the charger you referenced works (and in fact all hobby type chargers I'm familiar with) is that they simply pass charge current through the entire pack (one charge circuit) and then they have the ability to selectively and individually apply a load to the individual cells in order to "bleed off" some energy. Typically, the maximum bleed current per cell is some small fraction of the total charge current, so there is a fairly limited amount of capacity differential per cell that they can cope with.

Some charger designs don't have the balancer circuit integrated with the charging logic, so (again in an RC application) for example you might have a balancer doing it's best - applying a 500mA discharge against the highest cell; but if the charger is applying 5A of charge current, you've only reduced the high-voltage cell to 4.5A of effective charge current. The charger won't stop until it sees the "proper" voltage across the entire pack. This design works fine in the case of minor cell mismatch (i.e. within the balancers ability to fully cope with), but it clearly has its limits and has a potential for failure if the mismatch exceeds the balancer's ability. You could easily defeat this design - throw it a pack with a bunch of drained cells and one charged cell, and you WILL have a fire. Each and every time. Guaranteed.

More intelligent/good charger designs monitor the individual cell voltages, AND they will reduce the charge current (there is still only one charge circuit) to absolutely ensure that no single cell exceeds maximum voltage. What typically happens in this case, is the charge current is reduced down to the maximum balancer current - in the above example, the charge current reduces to 500mA, the balancer applies a 500mA load against the cell at max voltage (essentially meaning that cell is no longer charging at all) and the other cells continue to experience 500mA of charge current. This design is very resilient - if you throw it a pack with a bunch of drained cells and one charged cell, it will safely charge the entire pack without any individual cell ever exceeding it's maximum rating.

The above two examples are a bit extreme - it's rare for an RC pack to get that far out of whack, but I HAVE seen it happen.

Although the capacities are far larger on the 787, the same methods apply.

I would love to see a diagram/documentation for the 787 charger design.
 
nm2582
Posts: 213
Joined: Tue Jun 26, 2007 2:15 pm

RE: FAA Grounds 787 Part 3

Mon Jan 21, 2013 2:41 pm

Quoting packsonflight (Reply 208):
I dont buy this single batch story.

Apparently the two burned battery are 30 numbers apart, but how big is a batch?
Most likely there are not more than 150 batteries excisting in the world, being produced over more than 5 years. 100 of them sitting in the 50 787 flying and the rest somewhere in the supply chain and spare part houses around the world.

Those batteries have limited shelve life, so nobody wants to many of them sitting around, specially for something like 30-50,000$ a pop.

It seems possible that the individual cells in the battery may be commodity items (I don't know, it just seems logical that they might be). By "commodity item", I mean that it's possible the individual cells are used for other purposes, and are "generic" building blocks for many different types of batteries. Only once assembled into the 787 form to they become specific to the 787.

If this is true, then it's theoretically entirely possible that "Boeing 787 battery #1" has (for example) cells of sequential number 11001-11008, and "Boeing 787 battery #2" has cells of sequential number 13872-13879.
 
nm2582
Posts: 213
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RE: FAA Grounds 787 Part 3

Mon Jan 21, 2013 2:54 pm

Quoting rheinwaldner (Reply 196):
If contents were spilled the containment has failed. To have spilled content, you don't need a containement.

Since there has already been a few references to RC lithium cell use, I'll throw one more out.

In RC, we have available what we call "LiPo sacks". Essentially, we acknowledge and accept that even under the best circumstances, sometimes "bad things happen" and our batteries will fail. So, we charge them in the LiPo sack. It is an enclosure that is solely designed to keep the flames "smothered" and "contained" inside the sack, while still allowing all the smoke and pressure to be vented (there is no attempt made to even try and control this). It's to keep our equipment, homes, etc. from burning down.

It's entirely possible that Boeing could adapt this technology. They could encase the cells in a steel enclosure (or whatever material is deemed able to 100% withstand the maximum possible energy of a failed battery without melting - the current enclosure may already satisfy this), and then have a sort of fume hood attached, such as a pipe that is several feet long and which contains baffling. It would be a sealed enclosure with the fume hood pipe as the ONLY way out. In the event of a failure of one or more cells, this would let all the pressure and smoke out, but would contain any fire / flammable substance from escaping "containment."

Just like we do in RC with our LiPo sacks.

Anyone see a reason why this idea wouldn't work? I am not a mechanical engineer (I'm a software guy by trade) but I rather like the idea.

[Edited 2013-01-21 06:57:39]
 
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BoeingVista
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RE: FAA Grounds 787 Part 3

Mon Jan 21, 2013 3:07 pm

Quoting packsonflight (Reply 208):
I dont buy this single batch story.

Apparently the two burned battery are 30 numbers apart, but how big is a batch?

I'd be a bit sceptical too if this is how it shook out, lots of separate components will also be produced in different batches and built up into cells before being assembled in the final serial numbered battery.

Also an unanswered question is what happened to the original ANA main battery, when was it changed and why.
 
RNAVFL350
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RE: FAA Grounds 787 Part 3

Mon Jan 21, 2013 3:08 pm

According to the NTSB report as seen on the Aviation Herald, the flight data recorder on JA829J indicates that the nominal battery voltage of 32V was never exceeded. Does this mean that an over-charge state never existed on this battery during this particular event?

If there was no over-voltage state during this event, does this mean that they battery was being charged at its operational design, or does this just mean that 32v was never exceed, but that the battery still may have been put into an overcharge state which has been proven to cause thermal runaway?

From a containment side of things, it is surprising to see how varied the opinions are. According to some the containment worked exactly as designed, while others here seem to think that it failed "spectacularly". I am no engineer, but from viewing the photos of the burnt out battery, it seems that the event was contained quite well. Whether or not it did its job as designed is up to the engineers and regulators to decide, but from what I understand so far from the investigation, there was never any danger due to collateral damage from this event despite what some people have posted here.

Some have posted that this could be the end of the 787 program altogether if another issue arises causing yet another grounding once the current issue is resolved. Seriously? Did the 777 in 2005 not have a serious issue due to icing in the fuel system that actually ended up causing a crash in Heathrow which could have been much worse than it was? This was not an isolated incident either as it had happend to other 777's as well, only at altitude which did not cause a serious problem (excempt maybe maintaining RSVM) as they were eventually able to recover fuel flow to the engines. Pretty sure this did't even cause a grounding, and it did cause a hull loss! I suppose you will find doomsdayers in any forum on the internet.

Does anyone here know what other commercial planes use Li batteries in service? I know the A380 uses them for emergency lighting, but nothing near the capacity of the 787. I also beleive the A350 (currently anyway) intends to use them, pending the outcome of the investigation I suppose.

Thanks all and really enjoy all the comments and information here on a.net. Especially from CM, Tdscancuk, Stitch, Lightsabre, Revelation and a few others who really seem to be at the heart of the aviation industry.

Paul
 
tdscanuck
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RE: FAA Grounds 787 Part 3

Mon Jan 21, 2013 3:11 pm

Quoting BoeingVista (Reply 176):
Do the individual cells on the 787 battery have individual charging circuits?

I don't know.

Quoting BoeingVista (Reply 176):
What if any systems or capabilities does the 787 lose if it loses the main battery?

If the main battery is lost while the airplane is powered down, you can't power up. If it's powered up, the airplane will continue to run on whatever generator sources it has (ground power, any of 4 engine generators, or any of 2 APU generators, or the RAT). If all generator sources fail and the main battery fails, the airplane will go dark except for emergency lighting systems (which have their own internal batteries).

Quoting WingedMigrator (Reply 178):
Quoting tdscanuck (Reply 174):
you don't get any rate data off a single event.

Sure you do: you've had one event per N flight hours. You have a rate from that, albeit with a wide confidence interval. Two observations will give you a tighter confidence interval, three even more, etc.

By "wide confidence band" you mean the variance is infinity...you don't get any rate data because you have no confidence interval at all. Suppose you have a part that really does have a failure rate of 1 per 1 million flight hours. After 1000 flight hours you have a failure...that's completely consistent with one failure you expected and you're good for another 999,000 flight hours (statistically speaking).

Quoting seahawk (Reply 181):
An in-flight fire which can not be put down by any means available on the plane is a huge risk.

Not if the energy is contained, that's the whole point. The batteries are, by design, located in compartments where there is nothing else to burn and they restrict the damage to the battery itself. They don't have infinite energy capacity, they will burn themselves out without breaching containment.

Quoting seahawk (Reply 181):
Just read up how long the fire department in Boston needed to kill the fire and how hard it is to kill such a battery fire, this is a big problem for an ETOPS180 or ETOPS 120 plane.

There's a major repeated confusion going on here...the Boston ARFF extinguished the battery 40 minutes after the fire was reported to them. They did *not* fight the battery fire for 40 minutes.

Quoting seahawk (Reply 181):
The battery should not ignite and it should not spill its contents, which means that the containment also failed.

That's a misunderstanding about what "containment" means in this context. The design contains the damage. It's written right into the FAA special condition...gases and electrolyte do not need to be physically kept inside the battery box, they must be prevented from causing meaningful damage to other equipment. It's somewhat similar to fire containment in large buildings...the requirement is that the fire can't cause damage to the evacuation routes (typically stairwells and elevator cores) for a proscribed period of time, *not* that smoke can't come out of the building. The aircraft equivalent is to keep the damage inside the battery box and safely vent the fire products out of the airplane. Based on all evidence we have from both events, that happened. There may be investigation results that show that damage *did* occur to other aircraft systems but I have never seen any reports of that yet. It's the latter that would mean the containment failed.

Quoting packsonflight (Reply 184):
"The battery failures resulted in release of flammable electrolytes, heat damage, and smoke on two Model 787 airplanes. The root cause of these failures is currently under investigation. These conditions, if not corrected, could result in damage to critical systems and structures, and the potential for fire in the electrical compartment"

I see no argument here!

There is nothing about the regulations or special conditions that says electrolytes or smoke must stay inside the battery box. It's a vented box, so it's pretty obvious it wasn't designed to do that. The regulations say the fire can't spread (it didn't), that smoke can't enter the passenger compartment or flight deck in flight (in didn't), and that the fire can't cause damage (loss of function) to other equipment...and it didn't. It's certainly possible that the NTSB/FAA will find some way it could but claims that it *did* seem to be erroneous.

Quoting seahawk (Reply 186):
One solution could be putting the batteries in similar bags and adding a Halon injection system that fills the bag in case of a runaway cell.

Wouldn't work...lithium battery fires are self-sustaining once they get going.

Quoting RickNRoll (Reply 189):
Smoke and flammable material were not contained, and posed a potential hazard to other aircraft systems. You could say that nothing was damaged by the "containment" that is being disputed, but the FAA feels it is not satisfactory in that it could have damaged important systems.

Smoke and flammable materials were not contained *within the battery box*, nor were they required to be. The FAA's statement that it could have (not did) damage other systems is the important part.

Quoting abba (Reply 192):
I find your argument basically flawed. The fact that the material didn't actually cause damage to any other system doesn't mean that the containment didn't fail. The very fact that the material left the container means that it wasn't contained.
Quoting rheinwaldner (Reply 196):
If contents were spilled the containment has failed.

That's not what fire containment means. The battery box has vents and always has...that tells you right off that bat that the system was never designed for physical containment of all products within the battery box.

Quoting abba (Reply 195):
Now the fact that a totally foreseeable event actually happens - something that everybody - including Boeing - know will happen now and again - should not ground the 787. Either something has happened that has not been foreseen or some (containment) system didn't work as intended. If everything just did work as planed the incident shouldn't have lead to a grounding but only a new battery.

The problem is the rate...batteries aren't supposed to catch fire this often. This means all the fault trees with "battery fire" in them are potentially using the wrong probability, which rolls up into the higher level probabilities of serious or catastrophic events. Until they re-evaluate those possible effects and probabilities, they don't know if they actually meet the regulations.

Quoting rheinwaldner (Reply 196):
As if anybody would really be interested to learn how well the containement would prevent spilled content and held back smoke during a 40min on board fire over the Pacific.

Smoke containment is proven (by actually putting smoke in the bays) for considerably longer than 40 minutes during certification, so we know that actually works. Spilled content is fine per the regulation as long as it doesn't damage other systems. Unless I missed a report somewhere, it didn't damage any other systems.

Quoting kalvado (Reply 202):
Quoting tdscanuck (Reply 174):
It's not about demonstrated effect on safety of flight, it's about demonstration of compliance with regulations. There are lots of ridiculous regulations that you still have to comply with, even if they have no direct bearing on safety of flight.

Just out of curiosity - can you give an example of such "ridiculous regulation"?

My poster child example is the requirement for ashtrays on the lav doors...it's a holdover from when smoking was allowed on flights. Ostensibly, it's still required so that *even* if someone ignores the warnings *and* disables the smoke detectors *and* the lav fire extinguishing fails or they don't actually dispose of the cigarette in the trash, *then* you still have a "safe" place to put it out. Apparently, the sink and toilet are not viable options to extinguish a single cigarette.

Tom.
 
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Stitch
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RE: FAA Grounds 787 Part 3

Mon Jan 21, 2013 3:27 pm

Quoting BoeingVista (Reply 213):
Also an unanswered question is what happened to the original ANA main battery, when was it changed and why.

Japanese media reported it was removed because when they tried to start the engines using the battery, it didn't work. However, the Ships Battery is not used to start the engines. Perhaps they meant starting the APU (the Ship's and APU battery work together to start the APU, though the APU battery can do it on it's own if necessary).
 
nomadd22
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Joined: Fri Feb 22, 2008 7:42 pm

RE: FAA Grounds 787 Part 3

Mon Jan 21, 2013 3:33 pm

Quoting rheinwaldner (Reply 209):
Wrong. Even the most stupid charger for RC aviation which costs less than 50 bucks has a balancer. Check e.g. this device for roughly double that price:
http://www.graupner.de/fileadmin/dow...nleitungen/20060213144038_6414.pdf

The english section starts at page 16.

A balancer means, that beside measuring the voltage over each cell exactly, the charger applies differential currents in order to not overload a single cell. So as a result, each cell is treated seprately during charging.

We can safely assume that the 787 charger has a balancer, a cell temperature monitoring (I think it was confirmed by CM in an earlier thread) and normally also cell matching during battery production.

The problem is only, that this setup seems to not work properly. Something did not work as designed.

About the finding, that different reasons caused the two fires:
This is even worse, because the larger the number of actual issues, the larger the number of to be expected but still undetected flaws.

That link says no such thing and there's no "differential currents" supplied to individual cells. In fact the charger is only made for a single lithium cell. The pdf in the link instructs you to remove the individual cells and discharge them on their own in order to balance them. The only multi cell balancing in the average charger is a higher voltage applied on occasion to force current through after the point most of the cells are fully charged in order to bring weaker cells up.
You can assume whatever you want, but poor cell matching is a definite suspect in this whole thing. And there's no reason to believe that Boeing has included the ability to monitor and disconnect individual cells in a series. Maybe they do, but from the reports so far, it doesn't look like it.
 
cornutt
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Joined: Sun Jan 20, 2013 6:57 am

RE: FAA Grounds 787 Part 3

Mon Jan 21, 2013 4:14 pm

Quoting rheinwaldner (Reply 167):
Thanks, so we now know that a single cell died and did run away thermally. I also have to say that 8 cells is not much for such a high capacity. Why the selection of high currents instead of higher voltages?

A nominal voltage of 28V DC (usually specified as 24-32V range) is a standard for aircraft electrical systems. It's something of a compromise between the larger conductors that would be needed at lower voltages, and the more heavily insulated conductors that would be needed at higher voltages. It was also a convenient voltage for the electro-mechanical avionics systems back in the day. (Not so much for modern electronics, actually, but...)
 
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seahawk
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RE: FAA Grounds 787 Part 3

Mon Jan 21, 2013 4:19 pm

Quoting tdscanuck (Reply 215):


There's a major repeated confusion going on here...the Boston ARFF extinguished the battery 40 minutes after the fire was reported to them. They did *not* fight the battery fire for 40 minutes.

So what where the firemen doing in those 40 minutes? Wait to see if the whole plane will catch fire or maybe it was the more likely situation that they had to "control" the fire until the battery burned itself out, as they had no means to extinguish the fire within the plane, which would not cause excessive damage.

The report also mentions slight damage to the surroundings of the battery - slight damage even though the fire was quickly detected and fire crews arrived on scene quickly. It is every ones guess on how that would have gone 3 hours out over the Pacific. I am asking myself if such a fault would have caused the other batteries to overheat, which would easily cause the same failure on those and a nasty chain reaction.
 
nm2582
Posts: 213
Joined: Tue Jun 26, 2007 2:15 pm

RE: FAA Grounds 787 Part 3

Mon Jan 21, 2013 4:20 pm

Quoting nomadd22 (Reply 217):
That link says no such thing and there's no "differential currents" supplied to individual cells. In fact the charger is only made for a single lithium cell. The pdf in the link instructs you to remove the individual cells and discharge them on their own in order to balance them. The only multi cell balancing in the average charger is a higher voltage applied on occasion to force current through after the point most of the cells are fully charged in order to bring weaker cells up.
You can assume whatever you want, but poor cell matching is a definite suspect in this whole thing. And there's no reason to believe that Boeing has included the ability to monitor and disconnect individual cells in a series. Maybe they do, but from the reports so far, it doesn't look like it.

From the looks of that PDF, you're correct, that particular charger has no built-in balancing abilities. It's probably a several year old design - almost all the modern stuff has built in balancing. Modern lithium packs for RC use have a balancing tap - a second connector with a wire to every individual cell so that the pack can be balanced/monitored etc. per individual cell. Many chargers won't even work without it connected for safety reasons. I can't read German so I can't comment any further on that charger.

A "higher voltage applied on occasion" might work for lead acid, NiCd, NiMH type technologies (where excess energy can (to an extent) be safely dissipated as excess heat, but it's absolutely not possible on Lithium cells. Lithium cells can not dissipate excess energy in this manner. They absorb it until they fail. That's why you can't trickle charge them - you can trickle charge a NiCd indefinitely and it will just stay a little warm (excess energy converting to heat), try that with a lithium cell and it will fail.

The way balancing is done with all balancing chargers I'm familiar with, is to impart a load (resistance) across an individual cell to bleed off energy to maintain the desired voltage. On the charger I use, the balancer is active throughout the entire charge profile - if one cell is 0.05V higher than another midway through the charge profile (but all cells are at completely safe voltage), it will still balance the high cell down, instead of waiting until the very end to limit the cell to 4.2V.

I would agree that cell matching/balancing is definitely an area of interest. I really want to believe that Boeing has experts dedicated to this very topic (how could they not?!), but the NTSB's assertion that the battery never overcharged because it never went over 32V really bugs me. The only proper way to determine that no overcharge took place is to verify that none of the individual cells ever exceeded the maximum safe per-cell voltage.

Stating that the battery never exceeded 32v is absolutely meaningless and tends to imply that no other metric was available.

I hope they are just "dumbing down" their presentation.
 
cornutt
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RE: FAA Grounds 787 Part 3

Mon Jan 21, 2013 4:26 pm

Quoting RNAVFL350 (Reply 214):
If there was no over-voltage state during this event, does this mean that they battery was being charged at its operational design, or does this just mean that 32v was never exceed, but that the battery still may have been put into an overcharge state which has been proven to cause thermal runaway?

IIRC the report said that the data in question came from the flight data recorder. On a modern aircraft, the FDR only records a small subset of the available data. The aircraft's maintenance system maintains a lot more data parameters, at higher sampling rates, and it probably has data on the individual cell temperatures and voltages. I don't know how long it would take to wade through all of that.
 
Kaiarahi
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RE: FAA Grounds 787 Part 3

Mon Jan 21, 2013 4:28 pm

Quoting nomadd22 (Reply 217):
there's no reason to believe that Boeing has included the ability to monitor and disconnect individual cells in a series

Or that they (meaning Yuasa, Securaplane, Thales - not just Boeing, or even primarily Boeing) have not, given the regulatory conditions:

Quoting Kaiarahi (Reply 206):
Safe cell temperatures and pressures must be maintained during any foreseeable charging or discharging condition
Quoting Kaiarahi (Reply 206):
Lithium ion battery installations must have a system to control the charging rate of the battery automatically
Quoting Kaiarahi (Reply 206):
A battery temperature sensing and over-temperature warning system with a means for automatically disconnecting the battery from its charging source in the event of an over-temperature condition, or,

(ii) A battery failure sensing and warning system with a means for automatically disconnecting the battery from its charging source in the event of battery failure.


The prototype was described by the Admin Law Judge hearing a suit against Securaplane as having "a signal connector made to connect with the BCU with roughly 20 to 30 interface signals that go between the two".

[Edited 2013-01-21 08:42:36]
 
PHX787
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RE: FAA Grounds 787 Part 3

Mon Jan 21, 2013 4:30 pm

Hey guys, some more news from Japan today:

ANA reportedly cancelled 355 flights and the JMoT will have the Dreamliner grounded until at least* the 27th

*I say at least, which wasn't mentioned in the article, because of course they cannot unground the plane until the FAA gives the go-ahead.

http://www.japantoday.com/category/b...-due-to-dreamliner-fleet-grounding

Many thousands of pax are stranded which makes me wonder how they are being accommodated?


-Zach
 
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Stitch
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RE: FAA Grounds 787 Part 3

Mon Jan 21, 2013 4:35 pm

Quoting seahawk (Reply 219):
So what where the firemen doing in those 40 minutes?

They had to suit up and drive to the plane. They had to determine if there was anyone aboard the aircraft. Once they determined nobody was, that immediately lowered the sense of urgency. So they then determined what was happening. During that process, they determined they were dealing with a Class D fire and that their extinguishing agents they could deploy inside the bay would be ineffective. They then had to determine how to remove the battery from the plane so they could apply the appropriate agent to extinguish it. They then had to identify who would go into the bay. I imagine the bay is not designed for a fireman with self-contained breathing apparatus to easily enter, easily exit, or move freely around in so that took time to enter. There were claims of "two foot high flames" coming out of the vents on the box, so they apparently applied some type of agent to control those flames to allow them to remove the box from it's mounts and take it outside. They then had to carry the box away from the plane to an area to apply the necessary agents to extinguish the Class D fire.

Forty minutes does not strike me as an unreasonable timeframe to do this, especially when the emphasis is on the safety of the firefighters and not the airframe because there was nobody aboard.

[Edited 2013-01-21 08:52:17]
 
Kaiarahi
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RE: FAA Grounds 787 Part 3

Mon Jan 21, 2013 4:45 pm

Quoting Stitch (Reply 224):

   rcair1 (a firefighter) posted an excellent analysis in an earlier thread of the challenges and decisions.
 
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seahawk
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RE: FAA Grounds 787 Part 3

Mon Jan 21, 2013 4:48 pm

Quoting Stitch (Reply 224):

They had to suit up and drive to the plane. They had to determine if there was anyone aboard the aircraft. Once they determined nobody was, that immediately lowered the sense of urgency. So they then determined what was happening. During that process, they determined they were dealing with a Class D fire and that their extinguishing agents they could deploy inside the bay would be ineffective. They then had to determine how to remove the battery from the plane so they could apply the appropriate agent to extinguish it. They then had to identify who would go into the bay. I imagine the bay is not designed for a fireman with self-contained breathing apparatus to enter, exit, or move freely around in so that took time to enter. There were claims of "two foot high flames" coming out of the vents on the box, so they apparently applied some type of agent to control those flames to allow them to remove the box from it's mounts and take it outside. They then had to carry the box away from the plane to an area to apply the necessary agents to extinguish the Class D fire.

Forty minutes does not strike me as an unreasonable timeframe to do this, especially when the emphasis is on the safety of the firefighters and not the airframe because there was nobody aboard.

And how does that conflict with my first post, that no means available on the plane could have handled the fire and that the battery seemed to have burned (more or less) for around 50 minutes at least? I just wanted to point out that getting the battery fire out is not a simple shot with a normal fire extinguisher or a normal dose of Halon. I had no intention to blame the fire crews for anything, just say that this is not an easy fire to put down, even thought it was limited in size.
 
rheinwaldner
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RE: FAA Grounds 787 Part 3

Mon Jan 21, 2013 4:49 pm

Quoting nm2582 (Reply 210):
A balancer circuit is NOT inherently the same as a separate charging circuit.

The main current goes through all cells in series, that's correct. But the balancing currents still mean, that each cell "sees" an own, independent charging circuit.

The balancer does treat each cell separately and allows to balance the voltage as it builds up over each single cell. Of course and as you explain very well, there are limits on the hobby chargers. But even if the balacing currents are limited (about 20mA in many typical devices IIRC), the charger can still stop charging at all, if the applied differential current no longer allows to keep the voltage over a troubled cell in a safe region.

I would expect on the other hand from the 787 unit to have balacing currents that are not limited....
 
nm2582
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RE: FAA Grounds 787 Part 3

Mon Jan 21, 2013 4:55 pm

On the topic of how long it took to put the fire out:

Keep in mind that a lithium "battery" does not burn up all at once (all cells do not burn down at the same moment). It's comprised of individual cells, and frequently you will see a failure that goes something like this:

One single cell (let's call it #1) fails for whatever reason, and it emits a large amount of heat in a short timeframe (measured in seconds, not minutes). The cell nearest to the failed cell absorbs enough heat to induce a thermal runaway, but it takes a few minutes to occur. Let's call this cell #2.

When cell #2 fails a few minutes later and emits a large amount of heat, yet another cell is forced into thermal runaway, which again takes a few minutes to occur.

The process can repeat several times over as each individual cell fails in its own time. The amount of physical barrier (if any) between cells, the distance between cells, the thickness of the cell casing, etc. etc. all play roles here in determining how long it takes for the cells to fail like this.

So, it's entirely possible that the firefighters knew this, and for the most part let the battery fully fail (i.e. wait until all cells are burned up and failed) while keeping a watching eye on the situation to verify nothing else is set on fire.
 
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airmagnac
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RE: FAA Grounds 787 Part 3

Mon Jan 21, 2013 5:06 pm

Quoting RickNRoll (Reply 198):
something that I would intuitively have thought was very simple to agree on.

This is aviation. Very little about it is intuitive. Even the basic properties of a wing are not intuitive (see the opening paragraph of W. Langewiesche's "Stick and Rudder" (1944)).
And complex, integrated, coupled, layered critical systems are certainly NOT intuitive.

Quoting PlaneInsomniac (Reply 203):
the Downplay Crowd
Quoting rheinwaldner (Reply 196):
There is a lot of wordart in these threads to play down what happened

Just to be clear : the events themselves are not being downplayed by anyone, they have consistently been described as serious, abnormal and to be fixed.
What is being nuanced is some of the interpretations given on this board of the events, of the relevant requirements and of the statements by Boeing, the FAA and the NTSB

And this is not a question of downplaying or minimising events because it's my favourite company in the world.

Personnally, if I had to choose between being pro- or anti-Boeing, I'd definitly choose the "anti" side. If this 787 issue brings Boeing down then my employer has a monopoly on the large airliner market, and I can hope to be paid a fortune while working only 2h a day making crap airplanes. Yipeeee !

But I don't reason in such emotional pro-Boeing/anti-Boeing terms. We're talking about safety here. That requires rational thinking and a no-nonsense approach to the problem. It also requires some subtlety in our representation of reality to preserve both safety and performance ; simplistic thinking on the lines of "it's either good or bad", or "safe/unsafe", are just not accurate enough.
 
rheinwaldner
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RE: FAA Grounds 787 Part 3

Mon Jan 21, 2013 5:15 pm

Quoting RNAVFL350 (Reply 214):
According to the NTSB report as seen on the Aviation Herald, the flight data recorder on JA829J indicates that the nominal battery voltage of 32V was never exceeded. Does this mean that an over-charge state never existed on this battery during this particular event?

No, it is meaningless. While total voltage is still 32V any cell could produce fireworks.

Quoting tdscanuck (Reply 215):
They don't have infinite energy capacity, they will burn themselves out without breaching containment.

Was this tested within an actual fuselage section?

Quoting tdscanuck (Reply 215):
...the Boston ARFF extinguished the battery 40 minutes after the fire was reported to them. They did *not* fight the battery fire for 40 minutes.

So the battery burned for more than 40 minutes.

Quoting tdscanuck (Reply 215):
Quoting rheinwaldner (Reply 196):
If contents were spilled the containment has failed.

That's not what fire containment means. The battery box has vents and always has...that tells you right off that bat that the system was never designed for physical containment of all products within the battery box.

So you claim, that the spilled content in this case does not warrant some attention?

Quoting nomadd22 (Reply 217):
In fact the charger is only made for a single lithium cell

Oops, you are right, I was 100% sure because I have the Ultramat 14. But ... it turned out that I have the Ultramat 14 plus. Here is the right docu:
http://www.graupner.de/mediaroot/fil...4_Ultramat_14_plus_de_en_fr_it.pdf

But everything that I said is valid.
 
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Stitch
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RE: FAA Grounds 787 Part 3

Mon Jan 21, 2013 5:16 pm

Quoting seahawk (Reply 226):
And how does that conflict with my first post, that no means available on the plane could have handled the fire and that the battery seemed to have burned (more or less) for around 50 minutes at least?

First, do we know for a fact that the battery was burning for close to an hour by the time it was removed from the airplane? Yes, people reported a smell almost an hour before then, but when dealing with electrical components, one does not have to have a fire in order to generate a smell.

Second, there is no means aboard to extinguish the fire. That is not the same as saying there was no means to handle it. That was what the containment box was for and it does appear to have been handling it - perhaps for as long as an hour - based on the physical evidence showing the rest of the EE bay was not on fire. And with the physical evidence showing the containment box was intact, it appears to have been able to continue to handle the fire for an even longer period of time.

As to what constitutes the containment box "handling" the fire, that has been stated multiple times in multiple threads by multiple people with direct knowledge - and understanding - of the relevant FARs and Special Conditions. It is quite clear from their postings that a number of people on this forum do not understand those FARs and Special Conditions - that or they are just willfully trolling the thread to advance a personal agenda / vendetta. Some may be reading the text and assuming things based on their own experiences - experiences not related to commercial aviation. And while the discussion of those experiences can in cases add context to the main discussion, they should not be treated as if they were directly relevant to the main discussion.

[Edited 2013-01-21 09:35:01]
 
Skydrol
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RE: FAA Grounds 787 Part 3

Mon Jan 21, 2013 5:23 pm

Quoting airmagnac (Reply 229):
If this 787 issue brings Boeing down then my employer has a monopoly on the large airliner market, and I can hope to be paid a fortune while working only 2h a day making crap airplanes.

Well, thank you for being honest about your products. Many of us have suspected this for some time, but finding out from an 'insider' confirms it.  




✈ LD4 ✈
 
TheSultanOfWing
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RE: FAA Grounds 787 Part 3

Mon Jan 21, 2013 5:39 pm

Quoting BlueShamu330s (Reply 207):

"A Japanese investigator examines a scorched fuselage on an ANA plane."

http://news.sky.com/story/1040689/dr...amliner-fire-investigation-widened

I am curious to know whether this scorching is from the inside out or from venting, and how the event can have been considered contained if such external damage was inflicted. I apologise if it has already been covered or if I am coming across as being incredibly dim.

Could someone also educate me on CFRP's resilience to such an event and whether the fuse will require remedial work or simply nothing more than "a wipe down and polish."

Rgds

Isn't the above pretty significant?


FH
 
BlueShamu330s
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RE: FAA Grounds 787 Part 3

Mon Jan 21, 2013 5:48 pm

Quoting TheSultanOfWing (Reply 233):
Isn't the above pretty significant?

I'm please someone else asked; I'm hopeful someone might yet be able to shed some light on it !

Rgds
 
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Stitch
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RE: FAA Grounds 787 Part 3

Mon Jan 21, 2013 5:49 pm

Quoting BlueShamu330s (Reply 207):
I have tried to wade through all the threads relating to the Dreamliner, but perhaps I have missed comments about a picture which appears in this link with the description "A Japanese investigator examines a scorched fuselage on an ANA plane."

I am curious to know whether this scorching is from the inside out or from venting, and how the event can have been considered contained if such external damage was inflicted.

Electrolyte solution was vented out of the EE bay and was deposited on the side of the fuselage, so this might be what they're referring to and showing a picture of. We know the EE bay did not catch on fire, so it cannot be a case of such a fire burning through the EE bay walls and coming into contact with the fuselage skin.

As to the containment angle, the box is not designed to be a Level 10 containment field from Star Trek: The Next Generation, even if a literal reading of the Special Conditions with no context as to what the FAA intended could create such a belief that it was. It is designed to allow gases and materials to vent from it because if it did not, then it could become an explosive device. And I would like to believe that the FAA would not sign-off on the installation of a bomb.  Silly

[Edited 2013-01-21 09:53:38]
 
CM
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RE: FAA Grounds 787 Part 3

Mon Jan 21, 2013 5:54 pm

Quoting TheSultanOfWing (Reply 233):
Isn't the above pretty significant?

It would be significant if it were true. However, the JTSB already released a statement saying the streaking on the outside if the fuselage near the vents was liquid material from the battery. The fact a journalist decided to use the word "scorched" seems incorrect in light of the JTSB statement.
 
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seahawk
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RE: FAA Grounds 787 Part 3

Mon Jan 21, 2013 5:54 pm

Quoting Stitch (Reply 231):
First, do we know for a fact that the battery was burning for close to an hour by the time it was removed from the airplane? Yes, people reported a smell almost an hour before then, but when dealing with electrical components, one does not have to have a fire in order to generate a smell.

Second, there is no means aboard to extinguish the fire. That is not the same as saying there was no means to handle it. That was what the containment box was for and it does appear to have been handling it - perhaps for as long as an hour - based on the physical evidence showing the rest of the EE bay was not on fire. And with the physical evidence showing the containment box was intact, it appears to have been able to continue to handle the fire for an even longer period of time.

As to what constitutes the containment box "handling" the fire, that has been stated multiple times in multiple threads by multiple people with direct knowledge - and understanding - of the relevant FARs and Special Conditions. It is quite clear from their postings that a number of people on this forum do not understand those FARs and Special Conditions - that or they are just willfully trolling the thread to advance a personal agenda / vendetta. Some may be reading the text and assuming things based on their own experiences - experiences not related to commercial aviation. And while the discussion of those experiences can in cases add context to the main discussion, they should not be treated as if they were directly relevant to the main discussion.

There I do respectfully disagree. The plane at Boston showed burn marks outside the box and the fire was monitored and probably controlled by the fire fighters for the majority of the probably burn time. I am quite certain that they will have made sure to cool the other batteries in the rack to avoid a chain reaction. (Those batteries can get critical at 70-90°C not that much considering how close the packs are mounted)
The plane in Japan had the contents of the battery leak out of the battery onto the floor and out of the plane.

Although not working in aviation, but being used to asses the potential risk of hazard material storages for chemical industries at work, I have doubts that this leakage was designed to happen.

I am aware of the design requirements of the containment, I am not convinced that it is working as intended though.
 
humanitarian
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RE: FAA Grounds 787 Part 3

Mon Jan 21, 2013 6:00 pm

Quoting tdscanuck (Reply 215):
Quoting tdscanuck (Reply 215):
My poster child example is the requirement for ashtrays on the lav doors...it's a holdover from when smoking was allowed on flights. Ostensibly, it's still required so that *even* if someone ignores the warnings *and* disables the smoke detectors *and* the lav fire extinguishing fails or they don't actually dispose of the cigarette in the trash, *then* you still have a "safe" place to put it out. Apparently, the sink and toilet are not viable options to extinguish a single cigarette.

Correct - not having an ashtray inside the lav is a 'no-go' item: You cannot MEL it. I ran into this scenario more than once. It can be missing from outside the lav but not inside. If you do not have one in stock, the solution was to take the one outside the lav and put it 'inside' and then MEL the outside ashtray. Another oddball no-go item found on the Airbus is the pilots sunvisor. If broken, the plane is grounded until it is repaired or replaced. Also got burned on that one.
 
CM
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RE: FAA Grounds 787 Part 3

Mon Jan 21, 2013 6:03 pm

Quoting seahawk (Reply 237):
the other batteries in the rack

There are no other batteries in the rack, or the aft bay at all, for that matter.
 
Kaiarahi
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RE: FAA Grounds 787 Part 3

Mon Jan 21, 2013 6:07 pm

Quoting seahawk (Reply 237):
I am quite certain that they will have made sure to cool the other batteries in the rack to avoid a chain reaction.

What other batteries are in the aft bay?
 
AeroWesty
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RE: FAA Grounds 787 Part 3

Mon Jan 21, 2013 6:07 pm

Quoting PHX787 (Reply 223):
Many thousands of pax are stranded which makes me wonder how they are being accommodated?

The article you linked doesn't use the word "stranded", it uses the word "affected". ANA has been reaccommodating passengers on flights with replacement equipment. Very few flights are actually being cancelled, in the grand scheme of things.

See: http://www.ana.co.jp/topics/notice130116/index_list_e.html
 
justloveplanes
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RE: FAA Grounds 787 Part 3

Mon Jan 21, 2013 6:09 pm

Quoting seahawk (Reply 237):
I am aware of the design requirements of the containment, I am not convinced that it is working as intended though.

I have to agree. The electrolyte leakout must have been a surprise (burnout containment seemed to work), I can't imaging spilling on to the floor was an acceptable scenario to the designers, and one pretty easy to correct with a larger vessel I would think.

So something like fluids boiling over must have happened, like when you fill something to full in the microwave...
 
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airmagnac
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RE: FAA Grounds 787 Part 3

Mon Jan 21, 2013 6:11 pm

Quoting Skydrol (Reply 232):
Quoting airmagnac (Reply 229):
If this 787 issue brings Boeing down then my employer has a monopoly on the large airliner market, and I can hope to be paid a fortune while working only 2h a day making crap airplanes.

Well, thank you for being honest about your products. Many of us have suspected this for some time, but finding out from an 'insider' confirms it.

  
Well now, I would have to slightly correct your interpretation of that sentence becau... ... ... oh hell, whatever  
 
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Stitch
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RE: FAA Grounds 787 Part 3

Mon Jan 21, 2013 6:30 pm

Quoting seahawk (Reply 237):
There I do respectfully disagree. The plane at Boston showed burn marks outside the box and the fire was monitored and probably controlled by the fire fighters for the majority of the probably burn time.

Yes it did. In a very small area, mostly where the battery box was in direct contact. So thermal heating of the containment box resulted in thermal heating and charring of the area that the box was in contact with.

Even the most cursory examination of the photo of the aft EE bay shows that most of it was untouched by fire nor was it exposed to sufficient thermal energy to char, melt or cause discoloration.



Quoting seahawk (Reply 237):
The plane in Japan had the contents of the battery leak out of the battery onto the floor and out of the plane.

Yes it did. And it leaked out of the aircraft via an outflow valve, not by burning/corroding itself through the floor of the EE bay and then the fuselage like the blood of the creatures in the fictional Alien universe. As such, I believe the question to ask is "what was the purpose of that outflow valve"? Was it the one designed to ventilate smoke and gasses from the EE bay and air flow caused the electrolyte to be expelled as well? Or was that outflow valve there to vent electrolyte in the event it spilled out of the containment box?



Quoting justloveplanes (Reply 242):
The electrolyte leakout must have been a surprise (burnout containment seemed to work), I can't imaging spilling on to the floor was an acceptable scenario to the designers, and one pretty easy to correct with a larger vessel I would think.

It was a surprise only if the regulators, Boeing, and the sub-contractors never believed a battery could leak. And if they all believed that, I would think that would have precluded them from designing a containment box in the first place.

That being said, I do agree with you that a second box surrounding the primary box seems prudent - kind of like a "double-hull" on an oil tanker.
 
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Braybuddy
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RE: FAA Grounds 787 Part 3

Mon Jan 21, 2013 6:34 pm

I think we're beginning to enter the realm of Alice in Wonderland in these threads: "When I use a word," Humpty Dumpty said in rather a scornful tone, "it means just what I choose it to mean -- neither more nor less."  
 
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kanban
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RE: FAA Grounds 787 Part 3

Mon Jan 21, 2013 6:47 pm

Quoting nomadd22 (Reply 199):
Being old and inflexible, I'm thinking that they need to rely a little less on computer odds crunching and more on Murphy.

ditto

Quoting rheinwaldner (Reply 230):
No, it is meaningless.

if the information removes, clarifies or indicates a path toward resolution, it is hardly meaningless... however I get your point that this tidbit isn't the keystone they're looking for.

for all the talk about the term "containment" nobody (well Tom and CM might but can't talk about it) knows what the pass fail criteria were written into the spec. We know there is venting capability to prevent gas buildup, we know there was an exit path for the excreted material, we know one vessel received a fireman's axe blow and subsequently showed more smoke residue, while the second was wrapped in plastic and carried out shows more dripping molasses.

So did it fail? maybe/ maybe not since we don't know the design criteria.. and to use our own interpretation of 'containment' as a basis for criticism just muddies the waters. We all want to be right in our opinions, however we need more facts first. like the one person, who maintained that these incidents proved CFRP was a bad material for aircraft, had a righteous opinion totally unsupported by the incident facts so he twisted them to support his opinion.
 
Kaiarahi
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RE: FAA Grounds 787 Part 3

Mon Jan 21, 2013 7:03 pm

Quoting Braybuddy (Reply 245):
"When I use a word," Humpty Dumpty said in rather a scornful tone, "it means just what I choose it to mean -- neither more nor less."

When a doctor says "transmural myocardial infarction", that's exactly what s/he means, and s/he's distinguishing it from a subendocardial infarction. If s/he added "acute", it adds further meaning. "Heart attack" does none of these things.

Believe it or not, aeronautical systems engineering is also a profession with its own precise terminology. Regulators also define and use that terminology to refer to specific actions and states. Hence, when a regulator uses terms such as "extremely remote", "explosion", "self-sustaining", "failure", "major or more severe failure condition" in a regulation addressed to the professional community of aeronautical engineers, it is using them as technical terms which have a defined and precise meaning that is understood by the professionals to whom they are addressed. What Wikipedia or a non-professional non-engineer thinks they might mean is irrelevant - fortunately.
 
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Stitch
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RE: FAA Grounds 787 Part 3

Mon Jan 21, 2013 7:23 pm

Quoting Braybuddy (Reply 245):
I think we're beginning to enter the realm of Alice in Wonderland in these threads: "When I use a word," Humpty Dumpty said in rather a scornful tone, "it means just what I choose it to mean -- neither more nor less."   


Napoleon Bonaparte is quoted as having said "Never ascribe to malice that which is adequately explained by incompetence."

Though in this thread, I believe it's ignorance (willful, in some cases) as opposed to incompetence behind the posts.
 
Kaiarahi
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RE: FAA Grounds 787 Part 3

Mon Jan 21, 2013 7:28 pm

Quoting Stitch (Reply 248):

Ah yes. The second state of knowledge is knowing what you don't know.

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