FAA Grounds 787s
Willoz269; put simply the battery must not burn except perhaps once or twice during entire life of 787 fleet. If battery does overheat or burn, fire must be contained and emissions safely vented. Of course Boeing was supposed to comply with all of that in the first place. NTSB report already reveals some rash assumptions and skimpy testing that led Boeing to self-certificate a dangerous battery system. Better luck next time!
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Thanks ozaub, amazing it took a kick in the pants before they did the correct thing. It is still concerning that such a "rare event" will remain unresolved for the time being.
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Willoz, I find it rather hard to believe as well. I am hopeful the bench testing of the system will turn something up. Meanwhile, I find it unconscionable that the battery and computerized charging/monitoring electronics in this aircraft could be re-certified without finding the problem that caused the meltdown. Surely there will be no FAA stamp of approval without discovering the flaw(s) in the system.
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ozaub:
Are you implying that driving a nail through a single cell in open air is not just as comprehensive a test as doing the same while it is in a closed box with other cells and connected to the charging unit? Boy you are picky!
... skimpy testing...
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Willoz269
agree amazing conclusions. What about pressure build up in the containment should the worst occur? And at that point you don't have the battery. I don't see how this helps half way across the Pacific or Atlantic.
"So correct me if I am wrong please, but they still dont know what the cause is (and probably never will), so the "fix" from Boeing is to "contain" a runaway battery, ie contain and released fluids and thermal damage inside a stronger box, not stop it from happening in the first place, am I correct? "
More bang for your buck
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So, are Boeing going to have to prove that the new container will work at 40,000ft empirically, or will the back of a fag packet calculations be accepted?
The thought of a trial set up to deliberately abuse the battery so that thermal runaway occurs in flight is an intriguing one.
The thought of a trial set up to deliberately abuse the battery so that thermal runaway occurs in flight is an intriguing one.
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Having flown below FL300 in propeller driven aircraft for most of my life I have seen St Elmo in all his glory, many, many times, and on occasion have listened to, and seen him, on the radio and other instruments. This lead me to wonder whether static electricity build up and/or magnetic induction could not have played a role in the 787 saga. In an aluminium can we have never had any problems but I remember that Beechcraft had some issues in isolating their avionics in the first plastic pusher that they built in the 1980s. Both static buildup and strong military radar caused some problems, if my memory serves. Any thoughts from the specialists?
Last edited by Baron 58P; 14th Mar 2013 at 13:43.
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I don't see the containment kludge being an issue. the outlet of the container could have a 2-way valve,,, venting out if internal pressure raises above standard and normalising (venting inward)when the aircraft drops below cabin-altitude oressure. the vent could discharge into a simple baffle-trap (think sink-waste) and final discharge could be arranged tat the tip of the tail-cone.
the sales-goons could promote this feature as "jet augmentation" to get you to safety quicker,if the battery failed
any fluids not caught by the trap would discharge into the slipstream clear of structure. (maybe a hazard on the ground, but you can't have everything on the wish-list when bodging!
As these "standby" batteries are clearly NOT just that, the 2 controllers could "talk " to each other....should ground-staff over-discharge* either battery, the other could automatically start the APU which would then recharge BOTH to meet despatch requirements.....
*(over-discharge means reduced reserve BUT STILL ABOVE ON-BOARD RECHARGING-LEVEL.
back to battery construction......the coiled,"swiss-roll" method would still suffer similar stresses to folded construction...plates swelling would pressurise the seperator-membrane, shrinkage leave voids. linear expansion would "shuffle" them ,one agains another "wiping" the paste into uneven clumps....not saying this doesn't happen with present folded-construction, but simply restating my opinion that wound circular cells have weaknesses as well.
many posts back, i suggested,- each subcell in a thermal/electrically insulating pot tails of fusible material connecting to an internal busbar to main-cell stud.
thus, any individual subcell going T.U. would self-isolate allowing the cell to carry on delivering full voltage at 2/3 capacity.
An aditional safeguard would be to make the inter-cell straps as fusible-links....the problem there is that current sufficiently high to melt them would mean the battery was already unserviceable , so this would be s "stable-door" action.
Every sub-cell should be monitored...24 delicate devices linked together with the only control being on batches of 3 ,doesn't and hasn't worked.
Any of the millions of model-aircraft and Heli. hobbyists, who ,as a matter of course, run Lipo's to the edge, could have told the boeing bean-counters and engineers that their design was fatally flawed. (not to mention the cellphone and laptop manufacturers who'se products are used by totally untrained and non-technical consumers.....other than ONE recall, BILLIONS of active-service hours...and they don't charge 16K for a laptop-battery, charger and control-system!
IMHO, this is another short-term kludge to get the revenue rolling again before the liability takes them down.
the sales-goons could promote this feature as "jet augmentation" to get you to safety quicker,if the battery failed
any fluids not caught by the trap would discharge into the slipstream clear of structure. (maybe a hazard on the ground, but you can't have everything on the wish-list when bodging!As these "standby" batteries are clearly NOT just that, the 2 controllers could "talk " to each other....should ground-staff over-discharge* either battery, the other could automatically start the APU which would then recharge BOTH to meet despatch requirements.....
*(over-discharge means reduced reserve BUT STILL ABOVE ON-BOARD RECHARGING-LEVEL.
back to battery construction......the coiled,"swiss-roll" method would still suffer similar stresses to folded construction...plates swelling would pressurise the seperator-membrane, shrinkage leave voids. linear expansion would "shuffle" them ,one agains another "wiping" the paste into uneven clumps....not saying this doesn't happen with present folded-construction, but simply restating my opinion that wound circular cells have weaknesses as well.
many posts back, i suggested,- each subcell in a thermal/electrically insulating pot tails of fusible material connecting to an internal busbar to main-cell stud.
thus, any individual subcell going T.U. would self-isolate allowing the cell to carry on delivering full voltage at 2/3 capacity.
An aditional safeguard would be to make the inter-cell straps as fusible-links....the problem there is that current sufficiently high to melt them would mean the battery was already unserviceable , so this would be s "stable-door" action.
Every sub-cell should be monitored...24 delicate devices linked together with the only control being on batches of 3 ,doesn't and hasn't worked.
Any of the millions of model-aircraft and Heli. hobbyists, who ,as a matter of course, run Lipo's to the edge, could have told the boeing bean-counters and engineers that their design was fatally flawed. (not to mention the cellphone and laptop manufacturers who'se products are used by totally untrained and non-technical consumers.....other than ONE recall, BILLIONS of active-service hours...and they don't charge 16K for a laptop-battery, charger and control-system!
IMHO, this is another short-term kludge to get the revenue rolling again before the liability takes them down.
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syseng68k
Indeed. In the last 20 years there has been a steady move in 'management' from:
The bean counters will still think they were right though. They
will probably see the whole exercise in terms of damage limitation and will learn nothing from it at all.
will probably see the whole exercise in terms of damage limitation and will learn nothing from it at all.
- Gain a gold star for making sure nothing goes wrong
to - Gain a gold star for screaming like a sea gull when it goes wrong and blame everyone else.
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CockneySteve is on the right track, ok a LiPo cell is not the same as LiIo cell but some of the characterics are the same. To get the full power of the battery all the cells must be balanced, any out of balance in one cell will reduce the capacity available from the pack. I can well believe that the cells that have failed will be out of balance. It should also be noted that with this out of balance you are still drawing the same current and guess what the pack temperature goes into orbit and the packs swell like a balloon. As all users of Lithuim batteries know balance is critical to get the capacity and also long life. Equally you can still charge an out of balance pack without any issues but you will still be down on capacity and risk of a failure.
Well, if it happened twice in 50,000 hours, and Boeing haven't identified (as I understand it) what the cause was, but only have palliatives, it will happen pretty soon again. Hopefully fully contained inside the strongbox.
What are the FAA going to do then ?
We did notice that the FAA approval to start a test plan was presented by Boeing's PR in a cleverly-worded press release which would imply, unless you read the words carefully, that the aircraft itself had been given the all clear.
What are the FAA going to do then ?
We did notice that the FAA approval to start a test plan was presented by Boeing's PR in a cleverly-worded press release which would imply, unless you read the words carefully, that the aircraft itself had been given the all clear.
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Willoz
I don't think you are (entirely) correct. From what I can gather in reading about this 'fix' and speaking to a 787 engineer who has been in contact with Boeing engineers during the investigation, it is more comprehensive.
Details seem to be under wraps at the moment (why?) but I believe the 'fix' incorporates the following: a software change to the charging system, re-designed cells with better quality-control, re-configured battery internals (cell arrangement), insulation between cells, more comprehensive monitoring of cell condition and monitoring of insulation condition.
All of that was Boeing's solution, and I believe the FAA then insisted on an improvement in the containment device, just in case..
So correct me if I am wrong please, but they still dont know what the cause is (and probably never will), so the "fix" from Boeing is to "contain" a runaway battery, ie contain and released fluids and thermal damage inside a stronger box, not stop it from happening in the first place, am I correct?
Details seem to be under wraps at the moment (why?) but I believe the 'fix' incorporates the following: a software change to the charging system, re-designed cells with better quality-control, re-configured battery internals (cell arrangement), insulation between cells, more comprehensive monitoring of cell condition and monitoring of insulation condition.
All of that was Boeing's solution, and I believe the FAA then insisted on an improvement in the containment device, just in case..
Pub User
In other words: Fiddle with everything (including a few things that have been ruled out already) and hope something works.
Which is just the FAA's way of saying "We don't trust your fixes 100%. So we're putting in this extra layer of protection."
The 'why under wraps' has a lot to do with the public's perception of safety. The 'put it in a heavy box and let it burn' won't sound too safe to the flying public. Even though it may be. In the final analysis, putting the battery in a box and reducing the failure effects from a threat to the aircraft to a maintenance headache may put more pressure on Boeing to find the root cause of the problem. Once the FAA signs off on this, they can't go back.But customer airlines can bring pressure for a solution to bear.
Details seem to be under wraps at the moment (why?) but I believe the 'fix' incorporates the following: a software change to the charging system, re-designed cells with better quality-control, re-configured battery internals (cell arrangement), insulation between cells, more comprehensive monitoring of cell condition and monitoring of insulation condition.
All of that was Boeing's solution, and I believe the FAA then insisted on an improvement in the containment device, just in case..
The 'why under wraps' has a lot to do with the public's perception of safety. The 'put it in a heavy box and let it burn' won't sound too safe to the flying public. Even though it may be. In the final analysis, putting the battery in a box and reducing the failure effects from a threat to the aircraft to a maintenance headache may put more pressure on Boeing to find the root cause of the problem. Once the FAA signs off on this, they can't go back.But customer airlines can bring pressure for a solution to bear.
In reply to inetdog at #1261, I agree that my term “skimpy testing” is far less diplomatic than NTSB’s assessment in http://www.ntsb.gov/investigations/2...cket_doc13.pdf. Note however that Boeing never bench tested complete battery system. Note too that Boeing was involved in development of RTCA’s more comprehensive “Minimum Operational Performance Standards” DO-311 but chose not to follow it. Interestingly Boeing avoided any legal obligation to meet DO-311 by just four months, because Special Certification conditions were set in Nov 2007 whereas DO-311 was issued Mar 2008.
For more info read Leeham media’s post about DO-311 at Special ‘task force’ studied lithium-ion batteries long before JAL 787 incident | Leeham News and Comment It has link to a “Comparison Matrix” of tests, some of which are quite lengthy; e.g. battery shelf life test can take up to a year. So don’t expect a quick return to service. Not if Boeing does the job properly.
For more info read Leeham media’s post about DO-311 at Special ‘task force’ studied lithium-ion batteries long before JAL 787 incident | Leeham News and Comment It has link to a “Comparison Matrix” of tests, some of which are quite lengthy; e.g. battery shelf life test can take up to a year. So don’t expect a quick return to service. Not if Boeing does the job properly.
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"Details seem to be under wraps at the moment (why?) but I believe the 'fix' incorporates the following: a software change to the charging system, re-designed cells with better quality-control, re-configured battery internals (cell arrangement), insulation between cells, more comprehensive monitoring of cell condition and monitoring of insulation condition."
Why are the details under wraps? Because anything is better than admitting you still don't understand what caused the problem in the first place, all the above is either a rehash of known facts or vague in the extreme.
It appears that Boeing's PR team are having more success than their engineers at present, let's hope the engineers play catch-up real soon.
"Details seem to be under wraps at the moment (why?) but I believe the 'fix' incorporates the following: a software change to the charging system, re-designed cells with better quality-control, re-configured battery internals (cell arrangement), insulation between cells, more comprehensive monitoring of cell condition and monitoring of insulation condition."
Why are the details under wraps? Because anything is better than admitting you still don't understand what caused the problem in the first place, all the above is either a rehash of known facts or vague in the extreme.
It appears that Boeing's PR team are having more success than their engineers at present, let's hope the engineers play catch-up real soon.
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@denachtenmai
"savvy SLF"
I doubt the five of us can make a dent
But in all honesty, having spent 30 years in another tech industry, sometimes tossing everything you can think of at a fault does in fact send the not quite identified root gremlin a'scurrying, it's problematic manifestations never to be seen again. Yet of course, this is aviation, where the buckshot approach may not apply - let's see.
I doubt the five of us can make a dent
But in all honesty, having spent 30 years in another tech industry, sometimes tossing everything you can think of at a fault does in fact send the not quite identified root gremlin a'scurrying, it's problematic manifestations never to be seen again. Yet of course, this is aviation, where the buckshot approach may not apply - let's see.