FAA Grounds 787s

[ITman]

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.

[WHBM]

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.

[Pub User]

Willoz

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?

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..

[EEngr]

Pub User (http://www.pprune.org/members/23192-pub-user)

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.In other words: Fiddle with everything (including a few things that have been ruled out already) and hope something works.

All of that was Boeing's solution, and I believe the FAA then insisted on an improvement in the containment device, just in case..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.

[denachtenmai]

But customer airlines can bring pressure for a solution to bear.

Especially if savvy SLF refuse to board :}

[worrab]

put it in a heavy box and let it burnThese batteries are weight-saving aren't they?

[ozaub]

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/2013/boeing_787/docket_documents/787_docket_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 (http://leehamnews.wordpress.com/2013/03/13/special-task-force-studied-lithium-ion-batteries-long-before-jal-787-incident/) 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.

[Momoe]

Pub user
"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.

[slf4life]

"savvy SLF"


I doubt the five of us can make a dent :E

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.

[fizz57]

"better quality control"....

I'll admit to having put that down on customer failure reports a few times and know exactly what it means!

[vapilot2004]

whisper to the good Mr Pub User:
All of that was Boeing's solution, and I believe the FAA then insisted on an improvement in the containment device, just in case..

Yes, the containment requirement is an FAA mandate. As to the rest, it is truly an international group to the rescue. For the reshuffling of the computer bits or bytes, Boeing is deferring in this case to the experts at Thales équipe de logique for Lion.v1.2. (patch codename:charger no fue) While I don't have direct knowledge of whether the cell isolation 'solution' originated in Everett or from the folks at GS Yuasa, I have heard from more than one source that the ongoing effort continues to be collaborative all around.

[FlexibleResponse]

I wrote on 18 Feb 2013...


Quote:
787 Battery Containment Plan Firms Up

As Boeing’s 787 enters the second month of its fleet-wide grounding, the U.S. airframer is poring over data collected on a series of flight and ground tests and says it is making “good progress” toward a solution.

The fix, at least in the short term, continues to be focused on improving containment of the aircraft’s two existing lithium-ion batteries and adding more temperature monitors to provide earlier warning of abnormal battery performance via the engine indicating and crew alerting system.
This is a very scary scenario when an aircraft manufacturer decides that the best fix (at least in the short term) is to improve the ability to contain Lithium ion battery fires and explosions that are probable (a certainty?) with statistically significant number of flight cycles over the next year or so.

The concept of trying to cope with flying a passenger aircraft with a ticking time bombs in both battery bays by adding additional layers of fire protection as opposed to the obvious solution of removing said time bomb is ludicrous to the extreme.

This route smacks very much of commercial interference and corruption of due process over what should be a very straight forward engineering solution.

At least Airbus has now demonstrated the strength of their conviction by announcing the decision that they will take the Lithium ion battery out of their A350 and replace it with Ni Cads until Lithium ion technology catches up with the required public transport mandated reliability requirements.

Wake up Boeing! Listen to your engineers. Without you, Airbus will inherit a monopoly and monopolies are bad for aviation.


Unfortunately with the latest Boeing Test Plan that has been approved by the FAA, our worse case scenario now seems to have come to fruition.

Boeing plans to apply tinkering software to the battery control mechanism and include a titanium bandaid to the battery just in case the they got the software tinkering wrong...which would eventuate into an inextinguishable airborne fire in a titanium box...but it won't bother the passengers according to Boeing Management...

If the FAA approves this fix, in the fullness of time and most unfortunately, the NTSB will have their arse (ass for US folk), both the FAA and Boeing...alas...

[Selfloading]

but it won't bother the passengers according to Boeing Management...

It bothers this one, I certainly won't be getting on a 787 any time soon.

[dfstrottersfan]

Quote:
but it won't bother the passengers according to Boeing Management...
It bothers this one, I certainly won't be getting on a 787 any time soon.

Agreed

[fgrieu]

Source: subscription to Boeing media alerts, see
The Boeing Company: Commercial Airplanes - 787 (http://www.boeing.com/787-media-resource/)(..)
The first layer of improvements is taking place during the manufacture of the batteries in Japan. Boeing teamed with Thales, the provider of the integrated power conversion system, and battery maker GS Yuasa to develop and institute enhanced production standards and tests to further reduce any possibility for variation in the production of the individual cells as well as the overall battery.(..)

Four new or revised tests have been added to screen cell production, which now includes 10 distinct tests. Each cell will go through more rigorous testing in the month following its manufacture including a 14-day test during which readings of discharge rates are being taken every hour. This new procedure started in early February and the first cells through the process are already complete. There are more than a dozen production acceptance tests that must be completed for each battery.

Boeing, Thales and GS Yuasa have also decided to narrow the acceptable level of charge for the battery, both by lowering the highest charge allowed and raising the lower level allowed for discharge. Two pieces of equipment in the battery system – the battery monitoring unit and the charger are being redesigned to the narrower definition. The battery charger will also be adapted to soften the charging cycle to put less stress on the battery during charging.
(..)
At least this suggests a possible cause of the issue has been identified and cured. Of course there is more, in particular w.r.t. containment of problem.

Update: the full press release is available here
Boeing Provides Details on 787 Battery Improvements - Mar 14, 2013 (http://boeing.mediaroom.com/index.php?s=43&item=2622)

[Tu.114]

Hm... lower maximum capacity and higher minimum charge state seems to equal less usable capacity. And the reinforced battery casing is also likely not doing anything to keep the weight down.

I cannot help but wonder whether this is just some quick stab at the problem to get the aircraft going again rather than a permanent solution. After all, the original battery capacity must have been determined with something in mind, and this "something" certainly was not "Let´s keep some margin in there for whatever trouble might brew up in the future".

[Falcon666]

BBC News - Dreamliner: Boeing says flights to restart in 'weeks' (http://www.bbc.co.uk/news/business-21796984)

Re the above report I just hope Mr Sinnetts quotes don't come back to haunt him in the future.
"Absolutely" to the question "Is the aircraft safe" and " Among the safest Airplanes our company has ever produced"
Like others my family and I won't be on one any time soon and don't under estimate the public with situations like this!
Once flying this plane will be understandably under so much scrutiny,lots of people's reputations on the line.
Time will tell!

[deefer dog]

So they've identified the problem is their PR line, and are seeking approval to fly on the basis of their "fix."

If they are confident that everything will be okay, I presume that once flights are resumed they will not be wasting any further time investigating this issue. All back to work as usual.

I don't think so! They will be looking at this for a long time to come, and in the meanwhile they'll be praying for a run of good luck.

[Speed of Sound]

At least this suggests a possible cause of the issue has been identified and cured.

Not to me it doesn't.

It was already in the public domain that this particular battery chemistry is more prone to failure at the upper and lower limits of its capacity. If a cause had been found it would likely be at one or other of those limits and that limit only would be altered, thereby preserving at least some of the battery's capacity.

Narrowing the operating window by not charging it as high or letting it discharge so low, suggests to me that they are just improving the odds of a failure by keeping it out of the 'danger zone'. ;)

[Jando]

Can't say I'm happy about the developments. Looks like Boeing has now redefined what a "thermal runaway" is, and, like magic, therefore a thermal runaway never happened. :=

From FlightGobal Boeing details 787 battery redesign, rebuts safety claims (http://www.flightglobal.com/news/articles/boeing-details-787-battery-redesign-rebuts-safety-claims-383475/):

In Boeing's view, neither incident met the company's internal definition for the condition called "thermal runaway". That is a situation in which there "is so much energy, so much heat and so much flame that it would put the airplane at risk", Sinnett says. "We know very clearly this was not the case in the Logan event and the Takamatsu event."

[edmundronald]

Boeing are behaving like King Canute. Putting the batteries in a box will just move the issue up one notch to a "containment failure". So from two problems in 3 months on a fleet of 50 or so planes, we can expect one problem per year or so from 1000 planes, which may not mean a lot in insurance terms but can be pricey when measured in souls.

By choosing to adopt containment at this stage, Boeing is also permanently rejecting the deployment of another battery technology across its fleet.

I think Boeing now needs to convince its shareholders that the 787 will be used mainly outside the US as this makes a marked difference in the risk of lawsuits and death compensation. Although I guess, about $1 Billion payout (3 airframe losses during the service lifetime) is perfectly acceptable for the execs, who hope this problem will only hit after they have left.

[FullWings]

In Boeing's view, neither incident met the company's internal definition for the condition called "thermal runaway". That is a situation in which there "is so much energy, so much heat and so much flame that it would put the airplane at risk", Sinnett says. "We know very clearly this was not the case in the Logan event and the Takamatsu event."
That assertion doesn't seem to be backed up by the NTSB initial report. If the firefighters had just stood back and done nothing, odds-on we'd be looking at pile of ashes in the outline of a 787 at BOS. It's very difficult to imagine there not being a serious conflagration with all that energy dumped into a confined space.

The "contained" burn damage occurred *despite* a fire crew arriving extremely promptly and using large amounts of extinguishant over the period of an hour or more. A luxury which is not available in the air, where the aeroplane was shortly beforehand.

This is commercial/political spin of the worst order and I wish Boeing would stop it and get on with fixing the problem(s). IMHO they should fire some of the management and hire some more engineers...

[edmundronald]

Fullwings -

Everybody who has lit a newspaper knows that unattended fires burn.

The Boeing execs have lost it, and the FAA supervision is craven. Do congresscritters and their families fly in planes?

[ozaub]

Boeing's PR version of "nothing can go wrong, go wrong, go wrong..." is "nothing did go wrong, go wrong,go wrong..."!

[sb_sfo]

In Boeing's view, neither incident met the company's internal definition for the condition called "thermal runaway". That is a situation in which there "is so much energy, so much heat and so much flame that it would put the airplane at risk", Sinnett says. "We know very clearly this was not the case in the Logan event and the Takamatsu event."

Wow, I hope Sinnett didn't take that attitude with either the Japanese regulators or his customers, at least until after a deep bow and an apology.

[kilomikedelta]

sb_sfo: I think the corporate approach is a power tie and swagger.

[sb_sfo]

Anyone else think that a "single validation flight test" and hundreds of hours of laboratory testing is not enough?

Unless the flight test is orbiting for 11 hours over the north Pacific and flight-starting the APU 2 or 3 times. I assume Mike Sinnett will be aboard?

[jbcarioca]

Of course it is enough. Boeing has told us that. As former Boeing executives have made clear the FAA does not have the ability to judge them. By definition none of us do. Supreme arrogance is still that, even if they are correct on specifics. My confidence has not been improved by their attitudes. The word hubris comes to mind.

[kilomikedelta]

sb_sfo: Unfortunately, Mr.Sinnett is booked on a team-building retreat at a ski resort that day.

[ITman]

I like the report in Flight Global especially the first paragraph...., this makes the whole thing very worrying.. Also noted that they are going for a higher discharge level that is a guarantee for battery heating and potential failure IMO.

Qte:

Root cause of 787 battery issues may never be found: Boeing
Print
By: ELLIS TAYLOR SINGAPORE 15 hours ago Source:

Boeing says the root cause of the 787 battery failures may never be established, but that it is moving ahead with a solution aimed at getting the aircraft back in the air.

The 787 fleet was grounded on 16 January following two incidents in which their lithium-ion batteries failed after overheating and leaking electrolyte, resulting in significant charring.

In the first incident, an auxiliary power unit battery on a Japan Airlines 787 failed while the aircraft was on the ground at Boston Logan International Airport, while in the second incident, an All Nippon Airways 787 had to be diverted to Takamatsu in Japan after the crew received a cockpit alert saying that the main battery had failed.

Boeing and battery manufacturer GS Yuasa have been working with the Japan Transport Safety Bureau and the US National Transportation Safety Board to investigate the battery incidents, but no definitive cause has been found for the battery faults so far.

"In the events of Logan and Takamatsu, we may never get to a single root cause, but the process we applied to understand the improvements that can be made is the most robust process that we have ever followed," says Boeing's vice-president and chief project engineer, Mike Sinnett.

Boeing has proposed significant changes to the battery system aimed at making it easier to cool the lithium-ion cells, as well as a new containment solution which would prevent overheated battery cells from starting a fire.

It has also reworked the battery charger with reduced maximum charging levels, a higher maximum discharging level and a softened charging sequence.

The US Federal Aviation Administration has approved a certification plan for the modified systems, which will undergo rigorous laboratory testing and a validation flight test before being certified for use on the global 787 fleet.

[FlexibleResponse]

Boeing looks for speedy approval after 787 battery tests | Business & Technology | The Seattle Times (http://seattletimes.com/html/businesstechnology/2020570076_787batterysolutionxml.html?prmid=4939)

Hinderberger reiterated the assertions of top Boeing executives a day earlier that played down the two events that led to the grounding: the battery fire in a 787 parked on the ground in Boston and the smoldering of a battery on a 787 flight in Japan.

He said that the fire in Boston consisted of small flames outside the blue battery box, but that “there was not a fire inside the blue box.”

Boeing's Hinderberger is reported in the Seattle Times to say that the fire in Boston consisted of only "small flames" outside the blue box.

So, apparently there is no need to worry.

[Walnut]

Surely the batteries are on board for a purpose,? if they have melted or discharged then that function is not met. I can envisage lots of downroute delays/problems even if a future failure/fire is contained? Lots of airlines could be unhappy?

[inetdog]

ITman:
I like the report in Flight Global especially the first paragraph...., this makes the whole thing very worrying.. Also noted that they are going for a higher discharge level that is a guarantee for battery heating and potential failure IMO.
I had a problem with that too, until I looked very hard at the description and realized that what he was referring to was stopping the discharge at a higher voltage/State Of Charge level rather than discharging more deeply.
Similarly on the high end, the are stopping charging sooner.
Together they will avoid larger parts of the battery operation area at either end that are most associated with both inefficiency and stress on the battery.
As a result the nominal energy capacity of the battery will be lower, but the available current will not be affected.

Oh, one other point while I am on the subject: When the aft battery is called on to deliver power, without the APU or other power available, does it also supply power to the charger and FDR so that conditions of discharge are recorded? Since they have had to replace so many batteries for over-discharge, that seems like relevant data.

[inetdog]

FlexibleResponse:
Boeing's Hinderberger is reported in the Seattle Times to say that the fire in Boston consisted of only "small flames" outside the blue box.

So, apparently there is no need to worry.
Why do I keep misreading that as Hindenberger? :rolleyes:

[toffeez]

If a 787 ever does go missing over the ocean, at least Boeing can say "we know the cause, that damn battery". No need to spend millions on a search like AF447.

[FullWings]

What amazes me is that Boeing admit that they still don't really know what caused the problem and in the same breath, say they've fixed it. Classic cognitive dissonance.

Don't get me wrong - the 787 looks like it will be a fine aircraft and one I'll probably pilot in the not too distant future. They *are* going to have to man up and totally redesign the battery part of it before I get on board, though, even as a passenger.

[dfstrottersfan]

Quote:
In Boeing's view, neither incident met the company's internal definition for the condition called "thermal runaway". That is a situation in which there "is so much energy, so much heat and so much flame that it would put the airplane at risk", Sinnett says. "We know very clearly this was not the case in the Logan event and the Takamatsu event."
Full Wings
That assertion doesn't seem to be backed up by the NTSB initial report. If the firefighters had just stood back and done nothing, odds-on we'd be looking at pile of ashes in the outline of a 787 at BOS. It's very difficult to imagine there not being a serious conflagration with all that energy dumped into a confined space.

The "contained" burn damage occurred *despite* a fire crew arriving extremely promptly and using large amounts of extinguishant over the period of an hour or more. A luxury which is not available in the air, where the aeroplane was shortly beforehand.

This is commercial/political spin of the worst order and I wish Boeing would stop it and get on with fixing the problem(s). IMHO they should fire some of the management and hire some more engineers...
Agreed - and how will containing such an event in a metal box help?

[fgrieu]

To an engineer, thermal runaway is when temperature elevation triggers something with the effect of releasing energy, further increasing temperature, leading to a self-sustaining positive feedback bringing the temperature outside of the design range.

In the context of a battery,
- the something that's triggered is liberation of the energy stored in electrochemical form, as heat and/or the release/expansion of gazes (this can contribute to the positive feedback by both mechanical and thermal means);
- thermal runaway can be split into two categories: within a cell, or propagating from a cell to adjacent cells; the NTSB report of the Logan incident suggests both categories of thermal runaway occurred (7 out of 8 cells had short circuited, strongly suggesting they released most of their energy).

Prohibition of thermal runaway in aviation Li-ion batteries has been worded as: "Li-ion batteries must be designed to preclude the occurrence of self-sustaining, uncontrolled increases in temperature or pressure", with no reference to the damage such event might cause.

Restricting thermal runaway to an unwanted release of energy at a level endangering the plane would be wreaking havoc with that engineering definition. I see it as a miserable attempt to deny the failure of Boeing's initial analysis that the battery as a whole was safe from thermal runaway.

[JohnMcGhie]

What amazes me is that Boeing admit that they still don't really know what caused the problem and in the same breath, say they've fixed it. Classic cognitive dissonance.

Well... "ish". They never said they "fixed" it. What they have said is that when it happens again, it will not take the aircraft down.

I suspect that all of the engineers who understand Lithium-Ion technology "know" what the cause is, but they cannot PROVE it because the occurrence of the problem vaporises the evidence.

I suspect that everyone believes that the proximal cause was dendrites on the battery electrodes. These can occur spontaneously: the root cause may very well be "choosing Lithium-Ion batteries".

We and everyone else could guess that the dendrites were caused by high charge or discharge amperage. But they can occur simply through cycling the battery. Whatever: by the time thermal runaway occurs, the original dendrites have been vaporised long ago.

OK, so the Boeing 787 becomes the first form of locomotion since steam trains to have a fire-box!

Now we have some questions for the Flight Crew among us.

Whether the batteries in their fire boxes are on fire or not, they are not producing electricity. Just above them are the same type of battery that provides the 10-minute backup of last resort for the flight controls. Those batteries are apparently not getting fireboxes.

So: If you were in Sully's position -- both donks failed and APU not running -- are you safe enough? Can you get us back on the ground undamaged?

:\

[Pub User]

So: If you were in Sully's position -- both donks failed and APU not running -- are you safe enough? Can you get us back on the ground undamaged?

Sully's position was so extremely unusual that we all know about it. We add the improbability of having already had a battery fire before the double-engine failure, which also damaged the ACE batteries.

The realms of probability are getting so remote by now that I am more worried about being taken down by an asteroid strike. :ok:

[eppy]

So: If you were in Sully's position -- both donks failed and APU not running -- are you safe enough? Can you get us back on the ground?



Just to put this one to bed; Sully's flight had generators from both engines online until the moment of touchdown. Both engines were badly damaged but continued to generate above idle power (enough to keep the generators online and the aircraft fully powered both electrically and hydraulically). This was one of the reasons why the aircraft was able to stay in Normal Law until it touched down. If both engines had completely failed, the aircraft would have reverted to Direct Law.

[grumpyoldgeek]

Here's what I don't understand. I have read that the 787 batteries had been failing non-catastrophically at some enormous rate prior to the catastrophic failures. I have not seen a single word about the failure analysis of these batteries. What's up with that? Surely A) Boeing must have been concerned that there was a deeper problem as soon as 4-5 batteries had to be swapped out and B) There must have been some clue as to what was going wrong and that the possibility of a catastrophic failure was probably much greater than originally predicted.

I'm an electrical engineer and small businessman in addition to being a private pilot. I design, build and sell electronic equipment that costs anywhere from USD 80 to USD 600. I can absolutely assure you that if my customers have more than one identical failure of my product, they let me know in no uncertain terms that the situation is unacceptable. And for the record, I agree and I get to the root of the problem. It's hard for me to fathom how Boeing could not take the same approach on a $150,000,000 aircraft.

[sb_sfo]

Think of Boeing in terms of too big to fail banks, and you'll start to see a pattern.

[Kiskaloo]

@grumpyoldgeek
Here's what I don't understand. I have read that the 787 batteries had been failing non-catastrophically at some enormous rate prior to the catastrophic failures. I have not seen a single word about the failure analysis of these batteries. What's up with that? Surely A) Boeing must have been concerned that there was a deeper problem as soon as 4-5 batteries had to be swapped out and B) There must have been some clue as to what was going wrong and that the possibility of a catastrophic failure was probably much greater than originally predicted.

In the majority of cases, the cause was ground crew operating the aircraft solely off battery power for periods longer than Boeing specified. This drained the batteries to a level where the safety systems in the BMU and BCS disconnected the battery to prevent continued discharging.

Once the battery was drained to this state, it could no longer be charged on the airplane using the airplane's charging systems. Instead, the battery had to be returned to Yuasa for recharging and refurbishment. As to why this was the case, I have not seen a definitive explanation. Perhaps because the airplane's battery system could not fully recharge the battery quickly enough. Perhaps Yuasa felt such a deep discharge required the battery cells be examined and replaced, if necessary.

One of the changes Boeing is making is raising that discharge cutoff limit. I would expect the limit will be raised to a point where the onboard charging system can fully recharge it in whatever time period is deemed necessary and therefore the battery will no longer need to be removed.

[Helix Von Smelix]

In the industry that I work in, if we have a failure of unknown cause, when we get to a solution, we would have two test rigs setup. One with the modification, and one to the previous standard.
If under duplicate testing neither fails, we do not have a fix. We would have to ensure the old design fails, and the new design runs as required.
I hope Boeing is confident with the testing, and solution.

[Kiskaloo]

@Helix Von Smelix
In the industry that I work in, if we have a failure of unknown cause, when we get to a solution, we would have two test rigs setup. One with the modification, and one to the previous standard.
If under duplicate testing neither fails, we do not have a fix. We would have to ensure the old design fails, and the new design runs as required.
I hope Boeing is confident with the testing, and solution.

Once the NTSB and JTSB have identified the root causes of the battery failures aboard JL8 and NH692 I fully expect we will see new Airworthiness Directives issued to specifically address them.

[lomapaseo]

Once the NTSB and JTSB have identified the root causes of the battery failures aboard JL8 and NH692 I fully expect we will see new Airworthiness Directives issued to specifically address them.

Not necessarily, depends on whether there is a remaining unsafe condition with a failed battery.

The failure by itself may not be critical to safe flight

[CONF iture]

Just to put this one to bed ...
Don't go to bed too early ...
Read the report one more time.

[ozaub]

Recertification will be even more challenging than procedure outlined by Helix Von Smelix #1312 because the standard is statistical risk, not absolute. NTSB quantified the risk requirement; “Boeing .....determined that the likelihood of a smoke emission event from a 787 battery would occur less than once in every 10 million flight hours”. In real life “there have been two critical battery events on the 787 fleet with fewer than 100,000 flight hours”. In fact fleet hours were only 52,000 so Boeing must substantiate to a critical audience that improvements to the battery system yield at least a 200 fold reduction in risk of failure.

[avogadro]

it is quite amazing. Boeing , by designing a firebox to enclose the battery is only telling us that the battery will definitely ignite again, but we must be satisfied with a fire box and an exhaust pipe. why the need of testing since the fire will eventually be under control. what is the main reason to undergo a test without adressing the root cause of the failure, which, by the way is unknown.
1 minor changes in the battery= approximately no change in design
2 retrofit a firebox and vent pipe= we expect igntion after modification
Why NTSB should give a credit to this...I doubt

[fgrieu]

Source: report on a Boeing presentation
Boeing outlines fix for 787 batteries ? The Register (http://www.theregister.co.uk/2013/03/15/boeing_787_fix/)

(...Boeing) hinted, during a 90-minute presentation (http://787updates.newairplane.com/certification/webcast) and Q&A session in Tokyo, that a “deep discharge” event occurred in one cell of the planes' batteries, heating it to the point at which it vented so much hot electrolyte that an adjacent cell warmed and also vented. A manufacturing fault seems to be the reason such an event was able to occur (...)Seems not unreasonable to me. Deep discharge of a cell is known to have the potential to leave it in a state of high internal resistance, where current flowing thanks to either the other cells supplying power, or a recharge attempt, will generate a lot of heat in the cell, causing the effect described.

If that is, several things went wrong
- operating procedures and supervising means should prevent using the battery beyond the point where deep discharge of all elements occurs; and only a defect of a cell should make deep discharge of a single cell possible (as hinted above);
- deep discharge of a single cell (always possible, and a clearly dangerous situation) could be detected by the electronics built into the battery, and trigger a fail-safe mode; if that's not designed-in, that's a mistake for a powerful battery, IMHO; and if it is there and did not work, why?

[pax2908]

No doubt, the proposed modifications go in the right direction ... including the new enclosure which is not a fix but a safety feature. Meanwhile, it is a nice demonstration about how people were comfortable calculating probabilities like 1E-9 about a brand new system, with little or no experience operating it in the actual environment.

[toffeez]

The dog sits on the firebox. If he yelps, they've got a problem.

note: this fix is SPA approved. During ETOPS sectors he gets fed and if he's
lucky he lives to work another day. Unlike the canary in the coalmine.

http://www.surlalunefairytales.com/illustrations/tinderbox/images/attwell_tinderbox1.jpg

[PAXboy]

avogadrowhat is the main reason to undergo a test without adressing the root cause of the failure, which, by the way is unknown.

Money
Male Pride

Take your choice which one should be top of the list. :hmm:

[Autogeorge]

In fact fleet hours were only 52,000 so Boeing must substantiate to a critical audience that improvements to the battery system yield at least a 200 fold reduction in risk of failure.

It's worse than that: the odds of two "one per 10 million hour" events happening in the first 50,000 hours is one in 40,000.

[cockney steve]

[The failure by itself may not be critical to safe flight

@ lomapaseo... As these batteries form a strategic last-ditch power-source, I'm baffled by the above assertion.
the ONLY time a flight with "dead" batteries can be (grudgingly) considered "safe", is if said aircraft is within gliding distance of a suitable airfield.....and that would be stretching credulity to the limits.
Boeing refuses to abandon the troublesome technology and therefore are reducing the aircraft to an "in-service" development role. I don't have a problem with that, so long as critical safety is not affected Therefore, IMHO, the strategy I outlined many moons ago, seems the only prudent way forward.

Boeing should eat a large slice of humble pie, admit their lack of understanding of the technology and maybe look to the modellers who fly Helis with over a metre diameter rotors on Lithium technology,pushed to it's limits....I'd venture to suggest these amateurs have a vastly lower failure-rate than Boeing have demonstrated and they don't send their depleted cells back to the manufacturer either.....(nor would they pay 16,000 dollars for a 24 cell pack ;) )

If necessary, the sub-cells could be reduced in size and more of them, in order to reduce the potential thermal danger of any single cell going into "meltdown"
and the isolation in a ceramic "jacket" together with fusible connectors would all help to ensure a safe and reliable storage-system
In any event, it is imperative that ALL cells are monitored and balanced.
Looks like they tried to maximise profits by only monitoring clusters of three....I believe the problems this bought -on is known colloquially as a "Cluster fxxk" :}

Theie "emperor's new clothes" denial of a fire is beyond belief....sit the buggers on a pile of thermite (aluminium-powder plus rust powder , heat to ignition and it reacts strongly enough to melt and join railway-track ) ...then wait for them to deny it was a fire!

[ajd1]

Maybe my memory is playing tricks, but weren't Boeing planning to get the 787 certificated for 330mins ETOPS, at least for the GEnx version?

[RetiredF4]

If deep discharge in one cell was the beginning of the thermal runaway of one cell, what was then the cause of this rapid deep discharge? Could the modifications in the box ---- better isolations of the cells itself and between the cells, of the wires, and the moisture draining capability ------- point to a moisture and isolation problem of the old box?
condensation causing a short between the box and one cell (remember the contact of one celll completely gone at the ANA event)? In such an event the evidence would evaporate due to the heat and no trace be left.
The new sealed box could prevent such an event by being airtight until a defined overpressure opens the new vents.

[peter we]

If necessary, the sub-cells could be reduced in size and more of them, in order to reduce the potential thermal danger of any single cell going into "meltdown"
and the isolation in a ceramic "jacket" together with fusible connectors would all help to ensure a safe and reliable storage-system
In any event, it is imperative that ALL cells are monitored and balanced.

Thats precisely how the Tesla is designed. It contains 6800 of these (18650 cell) -

List of battery sizes - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/18650#Round_lithium-ion_rechargeable)

isolated from each other.

[inetdog]

fgrieu:
Seems not unreasonable to me. Deep discharge of a cell is known to have the potential to leave it in a state of high internal resistance, where current flowing thanks to either the other cells supplying power, or a recharge attempt, will generate a lot of heat in the cell, causing the effect described.

My reading of the Boeing description is rather that "deep discharge event" is a carefully phrased reference to what may have been an internal short circuit. This both reduces the cell voltage and increases the cell's resistance to externally driven current, but only after the real damage has been done by the dissipation of the cell's energy inside the sealed case. That is what led to the venting they refer to, not current being forced through a benignly discharged cell.

[fgrieu]

I'm still looking at where "deep discharge" was originally used by Boeing. Tried browsing that video for an hour, but missed it. Pointers welcome!
Webcast - Boeing 787 Updates (http://787updates.newairplane.com/certification/webcast)

"Deep discharge" of a cell, without context, is a well-known phenomenon in all kind of batteries, where open-circuit cell voltage drops below some rated minimum. At least in some cells technologies (I do not know for Lithium Cobalt Oxide, much less the particular type used), deep discharge can permanently damage a cell, increasing its internal resistance. If that occurs, it is possible that the cell later overheats when subjected to high current, e.g. from a charger, or from other cells powering the load; the later can only happen in batteries with more than say 3 or 4 cells in series, and with one cell that developed significant imbalance w.r.t. the other ones.

A short circuit inside a cell (even a mild one, usually called leakage, as could occur from moisture) can cause deep discharge of a cell, but is not by itself deep discharge.

[gwillie]

What amazes me is that Boeing admit that they still don't really know what caused the problem and in the same breath, say they've fixed it.

Boeing's latest proposal ..
The dog sits on the firebox. If he yelps, they've got a problem.

Gotta luv that!

So, the "Dreamliner" moves to "Scareliner"...and, hopefully not...to "Screamliner"

[mostlylurking]

This is a kludge not an engineering solution.
So they put a volatile battery in a strong box (pressure vessel) and connect it to the outside air via a valve. This valve will be exposed to moisture, whatever materials the battery may vomit and freezing temperatures. It may not be called on to operate for years. Does such a valve exist? Has one been certified for this duty?
Methinks they may be creating a bomb.
On the other hand I may just be paranoid and dumb :)

[badgerh]

"The new sealed box could prevent such an event by being airtight until a defined overpressure opens the new vents"

One would really hope that the system that opens the new vents is big time fail safe. We do not want a bomb - better with leaky hot goo!

[inetdog]

mostlylurking:
Does such a valve exist?
The webcast mentioned a rupture disk. Very old technology which is far more likely to open before needed than to fail closed. There will also be a sensor to alarm when the disk ruptures.

[green granite]

One would also hope there would be a pressure gauge on the box as the line of last resort.

[Speed of Sound]

I'm sorry but that has got to be four times the size and twice the weight of the lead acid battery that will start my 3.5 litre diesel car! :ugh:

http://i1280.photobucket.com/albums/a481/SoS57/K1_zps3268ae09.jpg

[Kerosene Kraut]

I still can't believe this shortcut-strategy. How can a world class company promote such a strategy? Find the root cause or change the battery type please. This is just asking for trouble and like waiting for the next "discoloured" batteries. Ignoring (not knowing) the basic problem will not make things easier and not save money on the long run.

[RobertS975]

A long time ago, I posted something to the effect that fate had been kind to Boeing and the aviation world by presenting us with three separate battery fires, none of which ended in a hull loss or tragedy: the test aircraft which made an emergency landing in Texas, the empty JAL aircraft in BOS, and the ANA aircraft which required an emergency evacuation.

My fear is that fate will not be so kind at some point in the future.

[TURIN]

Do us a favour SoS. Resize that photo. Makes my 'ead hurt.

[Cool Guys]

Speed of Sound:

Are you saying this is the new battery containment box for the 787? What is your source?

Mostlylurking:

It does not look like a gludge to me. This is what I would expect the box to look like. It looks very strong and profesionally built. I am sure the weight is a bit of an issue but im am sure it is lighter than a NiCad in a box. According to an earlier post a LI has about 10 times the energy density of a Nicad

Kerosense Kraut:

You are right, the new box is not addressing the root cause of the fault. It is not a fix. It is there for that 1 in 10,000,000 chance of failure. The root cause is a bit sketchy but it seems the other changes such as modifying the max charge limit are addressing the root cause.

Sorry I dont know how to make the fancy blue quote boxes.

[Ancient Mariner]

Please tell me that's a model, because if that is going on an airplane, I'm not.

[kenneth house]

those three incidents plus the battery pack that Secura burned up in 2006--do you suppose that overcharging just might possibly be involved here, considering the charred remains of a battery thermal runaway, even though supposedly the FDR did not show evidence of overcharge and thus thermal runaway did not occur. Seeing is not believing...

What connects to the battery pack? The battery charger unit and the APU controller. One is a current source, the other a current sink. Overcharging can be caused by overcurrent too, not just overvoltage...although 32 volts is too high for trickle charging that chemistry.

[Speed of Sound]

Sorry about the size of the picture guys.

You can't upload photos on this forum so it is a link to a high definition pic. I have now downloaded it, resized it and uploaded and linked to my Photobucket site.

I assume you guys are using a different browser to me. Mine resizes any photo to 'fit the box'.

The source is Boeing themselves.

The Boeing Company: Commercial Airplanes - 787 Electrical and Battery Systems Photos (http://www.boeing.com/787-media-resource/787_gallery.html)

My second thought was that visual inspection and maintenance of this unit is not going to be quick!;)

[PAXboy]

The first picture (as shown earlier in thread without the cover) has this caption on the Boeing site:
Caption: View of new 787 battery enclosure, which adds another layer of protection and eliminates the potential for fire. (Door not shown)Eeerr, sorry guys but it does NOT eliminate the potential for fire!!! The potential is exactly the same as before. :rolleyes:

[inetdog]

Cool Guys:
Sorry I dont know how to make the fancy blue quote boxes.
Step 1. Hit the "Quote button" (words inside a balloon icon) from the format bar in the reply screen.
Step 2. Paste in the words you want to quote.
Rinse and repeat as needed.

glad rag:
This photo (http://www.boeing.com/787-media-resource/images/K3.jpeg) (follow link) shows the cover as well as the box. Clearly the cables shown connected to the battery in the open box constitute a test harness. The way the real cables come out of the box is much different.
And yes, replacing the battery inside the box will be much more difficult.

[toffeez]

I suggest we don't follow Boeing's choice of "battery containment box" or "battery enclosure" but call it what it is: FIRE BOX.

[118.70]

Can anyone read what the hazard label sticker says on the battery ?

[Pub User]

It says:

"Caution. Electrostatic Sensitive Device, Conductive Connector Cap Required".

[Golf-Sierra]

This photo (follow link) shows the cover as well as the box. Clearly the cables shown connected to the battery in the open box constitute a test harness. The way the real cables come out of the box is much different.
And yes, replacing the battery inside the box will be much more difficult.

From what I can see the plastic cover and the steel one are identical in form. A harness leads from the battery to a terminal on the cover to which a further harness is attached.

I wonder how the case will be vented?


Replacing the battery - about 40 additional screws to undo. Unless - perhaps - the LRU will be the battery and the case.

[Kerosene Kraut]

So what is their concept for operating the box? With a single hot cell will you have to shut down the entire battery and divert? Declare an emergency? What does all this mean for ETOPS?

[WHBM]

which adds another layer of protection and eliminates the potential for fire
Please, please, tell me that this rubbish was written by a PR girlie fresh from a Media Studies college course, and not by one of Boeing's technically-qualified staff. Honestly, if this nonsense had gone out under Boeing's name in Phil Condit's time then HE would have needed a Firebox to contain him !

[TURIN]

Replacing the battery - about 40 additional screws to undo. Unless - perhaps - the LRU will be the battery and the case.



Yes, but batteries don't require replacing often do they.

Oh, wait a minute. :uhoh:

Sos. Thanks very much.:ok:

[Mac the Knife]

"Honestly, if this nonsense had gone out under Boeing's name in Phil Condit's time then HE would have needed a Firebox to contain him !"

Phil Condit eh? Hmmm....

Boeing: What Really Happened - Businessweek (http://www.businessweek.com/stories/2003-12-14/boeing-what-really-happened)

[slf4life]

The pictures, the '...eliminates the potential for fire' captions are made for public consumption I assume. So I'll be generous and surmise they mean a CABIN fire :*

But that would mean Boeing thinks we (pax) are all simpletons, perfectly happy to share a fuselage with a fire/potential fire of ANY kind, no matter how well they claim it's contained. That can't be right can it? They can't be so desperate to restart deliveries that they think we'd swallow that?? :ugh:

[Torquelink]

Even if the FAA approve this lash-up it doesn't necessarily follow that EASA will does it? Or will Boeing then scream Airbus favouritism and protectionism . . . And I can't see the JCAA being pushed into something as apparently unsatisfactory as this either. Boeing seem to have modified their philosophy from "safety above all else" to "safety above all else within reason and provided it can be achieved quickly and with as little disruption and cost as possible" . . .

I for one am not going to rush to fly on it - at least on ETOPS routes.

[toffeez]

Was the only Boeing boss in recent times that Airbus respected and was afraid of. Same goes for his beautiful baby the 777.

The rest, "managers" and products, (747-8, 737Max & 787) are poor, pale, competitors.

[ij_]

Replacing the battery - about 40 additional screws to undo. Unless - perhaps - the LRU will be the battery and the case.

At least the next unlucky firemen will hope so :\.

[Cows getting bigger]

Genuinely ignorant SLF question.

If I were a passenger and I pitched-up with such a battery in a 'fireproof' box, would I be allowed to check it in as hold baggage?

[gcal]

@Cows getting bigger

That to my mind puts the entire thing into a nutshell - well done!

[Kiskaloo]

@kenneth house
those three incidents plus the battery pack that Secura burned up in 2006--do you suppose that overcharging just might possibly be involved here, considering the charred remains of a battery thermal runaway, even though supposedly the FDR did not show evidence of overcharge and thus thermal runaway did not occur.

There was no charge monitoring system attached to the battery that caught fire in 2006 at the Securaplane facility. This improper test set-up was determined to be the cause of the fire, not the design of the battery itself.

Both the JTSB and the NTSB have stated that they could find no faults with the charging system aboard JA829J (JL8) or JA804A (NH692) and both have ruled out overcharging as a possible cause.

[pax2908]

Presumably "no faults with the charging system" simply means that the units went again through some standard factory tests, and passed. In fact these standard tests probably (hopefully) evolved a bit, it would actually be interesting to read more details about that.

And I am not sure how one can "rule out overcharging" at this stage ... does it simply mean that some thresholds were not (never?) exceeded for some measured physical values (which ones?) and if so, the statement is rather weak.

[inetdog]

slf4life:
The pictures, the '...eliminates the potential for fire' captions are made for public consumption I assume. So I'll be generous and surmise they mean a CABIN fire
Actually, they really meant a fire inside the FIRE BOX.
What they are saying is that regardless of to what extent and how violently the battery melts down, and how volatile the liquid and vapor emitted may be, there will not be open flame inside the FIRE BOX. All sorts of exothermic chemical reactions, but not flame. Therefore no chance of fire. This statement was made in technical presentations, not just PR words. You just have to be very careful how the terms are defined.
Earlier comments about how the chemicals in the battery generate their own oxygen and therefore no air was needed to have flame were somewhat misleading. The chemical reactions within the active material and electrodes do not require external oxygen as part of a battery thermal runaway, but they do not release free oxygen nor by themselves count as fire.

[WHBM]

The chemical reactions within the active material and electrodes do not require external oxygen as part of a battery thermal runaway, but they do not release free oxygen nor by themselves count as fire.
Not my original understanding, but if so why not fill the firebox with nitrogen like the tyres ?

[ozaub]

Perhaps we're getting too hung up about the fire. Airport firies and NTSB say there was a fire, and my Gran said there’s no smoke without fire; but Boeing claims there wasn’t one. Who do we believe, who has most credibility?
It may not matter too much because quite apart from fire all Special Certification Conditions must be met. One requires “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”. Quantitatively that’s a target of once in 10 million flight hours, whereas real life had 2 failures in 52,000 hours. Modified battery system certainly looks much safer but Boeing must convince skeptics that it’s at least 200 times more reliable. That's challenging.

[Cool Guys]

Step 1. Hit the "Quote button" (words inside a balloon icon) from the format bar in the reply screen.
Step 2. Paste in the words you want to quote.
Rinse and repeat as needed.

I see, Thanks inetdog

[RobertS975]

I for one am not going to rush to fly on it - at least on ETOPS routes.

I, for one, don't care whether it is ETOPS or not. SR111 caught fire 30 minutes from Halifax and 40 minutes from BOS. It didn't matter, did it? And AC 797 had a rear lav fire over the continental USA about 30 years ago, emergent landing at CVG, but still a couple of dozen pax died.

[Chu Chu]

The box doesn't contain enough oxygen to support combustion for long. So if the products of a thermal runaway ignited, they'd self extinguish pretty quickly without a source of additional oxygen. Of course, you'd still have the heat of the battery event to deal with, but not a significant amount more from combustion.

[illusion]

Chu chu,

Except for the fact that the battery generates its own oxygen when "it lets go"
And is a key reason why it is very difficult to put out the fire.......

[lomapaseo]

Except for the fact that the battery generates its own oxygen when "it lets go"
And is a key reason why it is very difficult to put out the fire.......

True, but in a limted quantity that eventually is consumed and the fire self extinguished. Chidren's sparkelers come to mind

In the meantime simply ensure that the thermal heat and products stay confined.


O2 masks ala valujet etal. are yet other examples of controling the risk.

[EEngr]

ozaub (http://www.pprune.org/members/210563-ozaub):

Modified battery system certainly looks much safer but Boeing must convince skeptics that it’s at least 200 times more reliable. That's challenging.Boeing just put the battery in a heavy box and redefined 'safe'. Now, if one cell runs away, its still safe. Since the surrounding components and structure are protected and dangerous gasses will be vented overboard.

Since they still don't understand the root cause of the runaway, 200 times whatever has no meaning. You can't say that this was a statistical anomaly or that we'll be seeing batteries pop every few months from now on. But it won't matter.

[poorjohn]

Since they still don't understand the root cause of the runaway, 200 times whatever has no meaning. You can't say that this was a statistical anomaly or that we'll be seeing batteries pop every few months from now on. But it won't matter.Safety of the modified system will surely be demonstrated by analysis, and the white paper has almost certainly already been written, by someone with an impeccable reputation, and approved by a lot of others. What can FAA say - "pants-on-fire"? "No sir, no fires around here."

[fgrieu]

Boeing is trying some damage control redefining "thermal runaway" and "fire".

My understanding of the reaction that occurs during thermal runaway (which, that's undisputed, did occur at the cell and battery level) involves recombination of the oxygen originally weakly trapped in the Lithium Cobalt Oxide cathode, with the anode's material (is that graphitic carbon ?). That generates heat (unless I err, chemically in addition of any electrical effect), and smoke, and propagates. Boeing even puts a "fire hazard" sticker on the stuff.
http://i.imgur.com/azNJXh6.png
Draw your own conclusions on if thermal runaway at the cell or battery level qualifies as (contained) fire onboard.

That said, we can have some trust that what Boeing proposes greatly reduces the risk that thermal runaway of a cell degenerate into thermal runaway at the battery level; and trust that thermal runaway at the cell or even battery level, if it occurred, will no longer by itself endanger the plane. Only the combination of these events with some other event where the battery is needed could cause a disaster.

Thus questions now are
1) How likely does cell/battery failure remains ?
2) What if a battery no longer supplies adequate power ? There are variants: open or short circuit, degraded voltage source..
3) Are there other oversight of failure modes elsewhere in that plane?

Answering 1) is important, and depends a lot on what the root cause was in the first place. Unfortunately, here we can only speculate. I guess Boeing, and I hope the NTSB/JTSB, have much more information by analyzing the data available on the battery's history, and the other batteries. My guess is they'll get to the bottom of it.
2) Is about airplane safety, and well understood by the specialists (not me).
3) Well, I hope both Boeing and certification authorities are busy at it.

[fizz57]

Unlike the majority here who seem to think they know better than the qualified guys and girls at Boeing, Thales and Yuasa, I believe that the batteries and associated circuitry are fundamentally well designed and built (and no, I'm not a Boeing fan!)

Well-built batteries should only fail if they are mistreated electrically, and since we know that the entire electrical system was never tested as a whole before the planes started flying, that is where we should look for a root cause.

If this is the case, then the additional margins on charge and discharge adopted by Boeing are a correct measure to enable the battery to absorb abnormal electrical conditions. I would hope that these limits have been worked out on the basis of measurements on actual aircraft, and not plucked out of thin air by the bean-counters.

All this fuss over the battery box is purely political: the FAA mandated that there should be no fire, Boeing believed the batteries wouldn't fail catsatrophically (after all, they ARE an essential system) and perhaps took a rather cavalier attitude towards containment. But they did fail and catch fire, hence the need to show compliance even if all goes well and no other battery will ever catch fire again.

Another reason for the fuss over the box may be to divert attention from the design oversight in not fully testing the complete electrical system before flight, and the consequent self-regulation can of worms.

What would be interesting, and not publicised as far as I know, is how much the battery capacity has been reduced and how this impacts on emergency operations when the battery is doing what it is supposed to do (length of flight without other sources of power, number or duration of brake applications, number of APU start attempts...)

[green granite]

There are millions of Li-ion batteries being recharged perfectly safely every day in 'cheap' stuff such as phones, laptops, tablets etc with an extremely low failure rate (thermal runaway wise) so it's achievable for Boeing surely.

[Ancient Mariner]

This is what a small/medium sized Lithium battery looks like when it goes bang. It was brand new, not being charged, not being discharged and it was stored in an air conditioned environment. The amount of soot and gas was incredible and and it took us ages to clean the premises. The acrid smell lingered for months.
It was shipped back to the manufacturer who could not find any cause for the fire. I simply do not trust these batteries anymore.
Per

http://i1339.photobucket.com/albums/o702/perebs/DSC_0001cropped_zps979dbacf.jpg

[PAXboy]

fizz57Unlike the majority here who seem to think they know better than the qualified guys and girls at Boeing, Thales and Yuasa ...But we do know better BECAUSE:-
... and since we know that the entire electrical system was never tested as a whole before the planes started flying, that is where we should look for a root cause.Had they have tested the complete system in a more rigourous manner that closely replicated in service life, then folks might think that they know less than Boeing and their pals.

Boeing appears to have placed money and marketing above engineering - such as moving head office 2000 miles away to keep their hands clean. Yet, every company that gets to the top of the pile will become over confident and pull itself down several rungs. It is only a question of when, not if.

[Kerosene Kraut]

What prevents Boeing from switching to NiCad-batteries? Their 777 has them "ready".
There must be some blocker?
Duration of recertification? Time to modify existing frames? Functional needs? LiIon-Contracts?

[TURIN]

What prevents Boeing from switching to NiCad-batteries? Their 777 has them "ready".


I suggest you read the Tech Log thread to find out. :ok:

[Kerosene Kraut]

Smart suggestion but no answer.

[fizz57]

Paxboy:

I'm not suggesting Boeing haven't screwed up on the strategic issues such as system integration - which is why I think that's where the answers should be looked for.

But when it comes to the individual components and subsystems, I'm confident that all concerned did a good job and met all the specs they were given - which is basically what the NTSB have confirmed.

[syseng68k]

The problem with aviation kit is that it's become more about the process
than the end result. The "Medium is the Message", as McLuhan used to say.
Yes, it does meet the spec down to the last detail, but the battery system
is wrong by design in so many ways, as has been demonstrated by the
discussion over in tech log. The fact that this was never integration
tested as a complete subsystem beggars belief.

In industry, rapid developmnent techniques get product to market fast,
often with little or no process, using cheap components and yet most of
it works most of the time. Aviation throws millions of $ at the problem
and ends up with designs that sometimes look completely irrational and
clueless. Why is this ?.

Crowdsourcing works, and some are qualified to comment on this half baked
design, even with the limited info available...

[etudiant]

A 50 pound child's sparkler would make an impressive sparkle.
Some, but not Boeing, might even call it a fire.

[toffeez]

They put a hidden red nose on the Firebox.

http://i1325.photobucket.com/albums/u622/oldairbus/K3_zpsd84c90e6.jpg

[Pub User]

What prevents Boeing from switching to NiCad-batteries? Their 777 has them "ready".

Because of the size of the starter/generator units fitted to the APU, a NiCad cannot produce sufficient current, no matter how big it is.

[E_S_P]

Stripping back all of the recent PR releases etc, isolating the 'visible' effect of all of this by placing the battery (which as far as we know at this time is the only problem?), inside stronger physical containment is not a solution by definition. As many on here have already speculated on the possible causes, the underlying fault as such is still there.

I would hope that other works are also taking place in the background i.e. modified circuit designs, updated software, operating proceedures etc to address this. However, I suppose the crux of this debate is to establish if these batteries are really a critical part of the systems or not, and can sustain failure without causing any further problems with the AC ? If it proved that it doesn't, then perhaps the 'box' may suffice for now, but if goes the other way and it is proved they are critical, then it surely has to be a non-starter. Excuse the pun :}

I see this phase as basically sticking a bigger fuse in to see what happens next. If you don't know why the fuse blew in the first place and keep changing them for larger fuses how do you then know whats really going wrong until there is a larger failure? Perhaps extended tests once it is back flying (with no PAX I hope), with a little more attention focused into this area may eventually find an engineered solution. :ok:

[OpenCirrus619]

I was waiting until a little more information was available about Boeing's proposed approach.....

Now it is obvious:

They don't know what caused the fires
They aren't fixing the problem (difficult if you don't know what it is)

I will NOT be getting on a ScreamLiner until it has managed 10,000,000 hours with 0 battery fires (confined or otherwise).

Also, in view of Boeings apparent belief that PR is more important than good engineering, if there is a choice will be following the credo "If it's Boeing I ain't going" when chosing who to fly with (why take the risk?). I'll make an exception for the older, well proven models - but am starting to worry the same approach has been used for all the newer offerings. I will be recommending the same approach to friends and family.

I have a degree in Electrical Engineering - so hope I have a reasonable understanding of the issues.

[fgrieu]

Don't be so sure Boeing has not identified the cause, or at least some likely cause(s).

I think they have clues, but prefer not to tell, partly because they are not quite sure it is cell damage by deep discharge, water condensation leading to damage by electrolysis, internal cell short by some foreign material, or something else; partly because that would make more painfully apparent that the reasoning in the original certification was bogus, and passengers at (some, likely moderate) risk in previous flights.

So they take steps to mitigate the consequences of a thermal-runaway(-at-the-cell-or-battery-level as they call it), with this (not-a-)fire box, and frankly I think it is a sound safety measure given that they keep the same chemistry (perhaps, because of the peak power and relatively high voltage needed). And they take measures to operate the cells in a reduced voltage range, to less stress them. And they implement some (untold) improvement in the cell construction or/and screening. And use better fasteners, just in case. I only wish we had more details on the identified possible root cause(s) and how the measures resolve them. I do not despair that it will come.

[no-hoper]

Quote:
What prevents Boeing from switching to NiCad-batteries? Their 777 has them "ready".Because of the size of the starter/generator units fitted to the APU, a NiCad cannot produce sufficient current, no matter how big it is.

Ok.What about PT-6 and PW-100 engines during a Battery start with an old NiCad system.
The amperemeter is showing up to 1000 amps...

[Kerosene Kraut]

The A350 does use a strong 1,268 kW Honeywell APU that seems to be working with NiCad batteries.

[Smilin_Ed]

Because of the size of the starter/generator units fitted to the APU, a NiCad cannot produce sufficient current, no matter how big it is.

If the only reason they are clinging to Lithium Ion batteries is to get enough current to start the APU when there are no generators on line, they they should consider a cartridge starter. Cartridge starters will get a turbine up to speed in a real hurry. Reliable too.

[TURIN]

What prevents Boeing from switching to NiCad-batteries? Their 777 has them "ready".

Because of the size of the starter/generator units fitted to the APU, a NiCad cannot produce sufficient current, no matter how big it is.


My understanding is the main battery is required to have enough power to operate the emergency brakes in the event of an emergency landing with no other source of electrical power other than a rapidly slowing RAT.

The APU battery is the same type for the sake of commonality of LRUs.
IE. You are carrying a spare to get you home in the unlikely event the main one fails away from base. :O:oh:

[ozaub]

I fear that EEng #1368 and poorjohn #1369 are right. Boeing will contend that cell temperature (>570 deg F) and pressure (enough to rupture cell) which were clearly unsafe at Boston are “safe” in box at 30,000 feet 5 ½ hours from land. Boeing may have a “battery” of lawyers prove compliance with SCCs but won’t win in the court of public opinion.
Delve behind the actual SCCs in Federal Register, Volume 72 Issue 196 (Thursday, October 11, 2007) (http://www.gpo.gov/fdsys/pkg/FR-2007-10-11/html/E7-19980.htm) and ALPA seemed concerned from the outset that Boeing might push a “safe containment” strategy but was reassured that FAA would not allow it.
Long ago Boeing relied on its own idea of “safe” to meet fail-safe requirements for 737 fuselage; and it ended badly. Boeing claimed that if the fuselage fatigued, a single "lead crack" would grow along the skin until it reached a fuselage frame, then turn at right angles and a triangular shaped tear would blow out and safely dump fuselage pressure. British and Australian authorities never accepted the concept and a long war of words culminated in Boeing’s glib assurance in letter dated 14 April 1988 that it had "demonstrated safe decompression in lap joints …..". Two weeks later precisely this failure ripped the roof off Aloha Airlines Flight 243. Flight attendant Clarabelle Lansing died and 89 passengers feared they would.
Read full story at LESSONS FROM ALOHA (http://avstop.com/stories/aloha.html) and sorry for digression.

[Pub User]

The amperemeter is showing up to 1000 amps...

Where were you getting the juice from to power that?!?

An engineer friend who has worked on the 787 in Seattle told me that the ability to provide a high current was the main reason for using these batteries.

There is a hint in this graphic from Boeing:

Batteries and Advanced Airplanes - Boeing 787 Updates (http://787updates.newairplane.com/787-Electrical-Systems/Batteries-and-Advanced-Airplanes#gallery/InfoGraphic2)

.... in the unlikely event the main one fails away from base

Nice one

:ok:

[tucumseh]

As posted elsewhere, a Li-Ion battery kicking off. MoD trials, 1991. This is a normal battery for a manpack radio.

No-one mentions MoD's total recall and destruction order for BOWMAN HF radio Li-Ion secondaries (2006). Not repair, re-work or modification, but total destruction.



http://i214.photobucket.com/albums/cc291/exploringtheblue/LiIon5minsafterimpact_zps56d3e9e5.jpg

[Broomstick Flier]

Following the matters with great interest I am wondering if Boeing is planning to apply the firebox fix to both batteries as it seems so far only the centre EE bay will be modified.

I understand both are interchangable and before they can trace the root cause for all three incidents, which, admitely happened all with the centre battery, I am not very convinced of the safety guarantees they are clayming.

[TURIN]

I understand both are interchangable and before they can trace the root cause for all three incidents, which, admitely happened all with the centre battery,

Not quite. The JAL incident was the APU battery. The ANA, Main battery.

Not sure what third incident you are talking about. :confused:

[poorjohn]

There are several articles in the public press saying that Boeing will conduct two test flights approximately this weekend, and that the new system will be / has been subjected to the 2008 RTCA standards. One article NewsDaily: Boeing puts 787 battery to tough tests it once avoided (http://www.newsdaily.com/stories/bre92h12z-us-boeing-batterytest/) includes some comment about how difficult it will be / was to pass the test with LiCo: Lukso, who left SecuraPlane to start his own lithium-ion battery business, acknowledged that the RTCA standards are tough. At his new company, he spent $6 million and several years without successfully building a battery that could pass the test now in front of Boeing.

Another battery maker, EaglePicher Technologies, of Joplin, Missouri, passed tests modeled on DO-311, but used a less volatile chemistry than Boeing, known as lithium-iron phosphate.

"To successfully pass the containment (test), we needed iron phosphate," Ron Nowlin, general manager of aerospace systems for EaglePicher, said in an interview earlier this year. So I wonder how Boeing accomplished that result in a few weeks. Anyone think they've changed chemistry and aren't hooting about it?

[cockney steve]

Because of the size of the starter/generator units fitted to the APU, a NiCad cannot produce sufficient current, no matter how big it is.
@ pub user,- I'm calling bull**** on that one!
current -demand can be met ,simply by having lots more smaller cells.
Why do you think the present lithium configuration has 3 sub-cells in parallell.? much easier to make one big one, but the path across the plates to the terminal-post will be far longer.

The advantage of lithium technology is 3-fold
1- shape of cell is not as constrained as is the case with others.
2 higher energy-density. (stores more power in the same space)
3 higher discharge/charge current-capability.

The downaide is the need to very carefully monitor and control EVERY cell's operation. this is still not being done monitoring batches of 3 is where I think they came unstuck and history will repeat until they treat the technology with due caution. a bigger,stronger firebox is just a big lashup kludge.
IMHO, the software in the battery controller should automatically start the APU before the point at which doing-so would over-discharge the battery (IE when about 1/3 of the USABLE capacity has been drawn) this would go some way to ensuring that batteries remained serviceable, charged and rechargeable and met their primary function as reserve supply for ETOPS operation. thus , delays due to batteries not meeting despatch criteria, would be virtually eliminated.

A big tin box with a sewage-drain is not going to achieve that!

[inetdog]

http://dms.ntsb.gov/pubdms/search/document.cfm?docID=389173&docketID=54251&mkey=85973 :

March 21, 2013
Brett C. Gerry, Esq.
Vice President and Assistant General Counsel
for Commercial Airplanes
The Boeing Company
Post Office Box 3707, MC-22-83
Seattle, WA 98124-2207
Dear Mr. Gerry:
I am writing to remind The Boeing Company (Boeing) of its obligations as a party to a National
Transportation Safety Board (NTSB) investigation.
Since the Japan Airlines Boeing 787-8 auxiliary power unit battery fire event at Boston Logan
International Airport on January 7, 2013, the NTSB has received technical assistance and cooperation
from Boeing as a party to our ongoing investigation. Boeing is also serving as a technical advisor to the
NTSB in our role as the accredited representative to the Japan Tran sport Safety Board (JTSB) in its
investigation of the battery event that occurred on All Nippon Airways Flight 692 on January 16, 2013.
Our Office of Aviation Safety has worked close ly with Boeing throughout the Japan Airlines
investigation and our Office of Communications has worked effectively with Boeing regarding the
dissemination of information to the media.
Boeing is obviously familiar with the NTSB investigative process and its failure to inform the
NTSB of the content of the recent technical briefing in Tokyo prior to its occurrence is inconsistent with
our expectations for a party. As you know, the role and responsibilities of a party to an NTSB
investigation are set forth in the NTSB ' s Certification of Party Representative, agency regulations, and
accompanying information and guidance. The Boeing party representative signed this certification on
January 7, 2013. The NTSB expects parties to an investigation to comply fully with its requirements
and respect the role of the agency in performing its investigative responsibilities independently and with
transparency.
As a party to our investigation, Boeing's support of and participation in the upcoming
NTSB hearing beginning on April 23, 2013, are appreciated. If you or your staff have any questions or
concerns about the party agreement or your participation in our upcoming hearing, please do not hesitate
to call me.
Sincerely,
David K. Tochen
General Counsel

PS: See http://www.ntsb.gov/doclib/forms/NTSB_Investigation_Party_Form.pdf for information on the responsibilities of parties regarding information disclosure.

[WHBM]

Michael O'Leary's "it's regulatory crap" comment on the 787 issue

Ryanair CEO: Boeing 787 Problems 'Regulatory Crap' - Yahoo! Finance (http://finance.yahoo.com/news/ryanair-ceo-boeing-787-problems-171531994.html)

[Mark in CA]

Excuse me if I missed a post that discussed this, but what exactly are these two Boeing test flights going to test? Will they just confirm that the changes to the system work as planned, or with they also induce various failures to test how the new system reacts? And if the latter, how far along will that go? Will they actually test if the containment box and venting system work as designed in flight?

[green granite]

Will they actually test if the containment box and venting system work as designed in flight?

That would be easy enough to do, empty container with some dye in it in the rear compartment, with an inlet valve. Pressurise it with liquid nitrogen and check the valve releases at the right pressure and it vents satisfactorily. It would mean no APU though which would I would have thought be perfectly acceptable for a test flight.

[SMT Member]

Excuse me if I missed a post that discussed this, but what exactly are these two Boeing test flights going to test?

It's not two, three or more flight "tests". It's one single flight. What they hope to prove is anyone's guess, unless that is they take the kite somewhere over the mid-Pacific, say 330 minutes away from a suitable runway, and deliberately over-charge the battery to induce thermal runaway conditions. Somehow I don't that's going to happen though.

[ITman]

Boeing publicity again... we flew the bird no problems...

Sorry I cannot buy into this one test flight story..

[Finn47]

There might be two test flights after all. Quote from yesterday´s Reuters article:

The testing regimen set by the FAA requires one flight test. But Boeing plans to conduct two flights: One for its own purposes and a second to gather data to submit for FAA approval, according to the sources, who spoke on condition that they not be named.Boeing plans 787 battery test flights for end of week: sources | Reuters (http://www.reuters.com/article/2013/03/21/us-boeing-787testflight-idUSBRE92K01L20130321)

[toffeez]

They need to test the resistance of the composite structure to a red hot firebox.

Go out to mid-Pacific, light up the firebox, and fly home. Volunteers?

[Kerosene Kraut]

Shouldn't they rename it the Drainliner?

[FlightPathOBN]

more fodder...

U.S. officials rebuked Boeing for comments its executives made at a media briefing in Tokyo earlier this month on plans to get the grounded 787 Dreamliner flying again.

Boeing faulted by NTSB for comments on 787 fix | Business & Technology | The Seattle Times (http://seattletimes.com/html/businesstechnology/2020614479_ntsbrebukexml.html)

[Cool Guys]

Volunteers?

I will be flying on it the first chance I get. It seems like a great plane. The nice new box will contain any fire that does occur. Afterall, all the fixes will not prevent a fire from occuring, they should just reduce the chance of occurance to at least 1 in 10,000,000.

[fc101]

1 in 10 million....didn't NASA managers give those odds for the Space Shuttle exploding? Remind me again what the odds were of a battery fire in the first place.

Quoting odds like this is nonsense

[FlightPathOBN]

Here we go with the odds thing again....:ugh:

[avogadro]

Bean counters should not rush into solutions for the sake of airplane image or whatso ever is their goal. I believe NTSB officials with safety minded is calling for bat system modification guided by rootcause of incident. I quote from a japan newspaper.
"Mr. Sinnett said that all of their testing and analysis has concluded the only way a thermal runaway could occur is through overcharging. Boeing’s original designs have four layers of protection against overcharging. A review of data stored on the flight data recorder showed that the system had been “properly charged.”
i am quoting this because Boeing and his beancounters seem to divert from the objective: SAFETY FIRST
1 did thermal runaway really occur?
2 is the thermal runaway due to overcharging?
3 does "system properly charged" = no thermal runaway?
in the mood to get the airplane quickly back into air some hints for solution are being lost. I believe thorough investigations will definitely pave the way for getting the dreamliner back into service for comfort and safe flights.
in case I mistakenly judge please feel free to comment on this. thanks...

[G&T ice n slice]

Anyone any signals from anywhere as to whether the aircraft & associated risk is currently insurable, even with the "firebox" ?

[WHBM]

Anyone any signals from anywhere as to whether the aircraft & associated risk is currently insurable, even with the "firebox" ?
Interesting. Rumour had it this was indeed one of the things that did the MD-11 in for major passenger operators. It was, of course, all fully certified by the FAA and everything, but amazingly quickly ended up as a cargo hauler, and there was a lot of asset value lost by the initial large purchasers who prematurely retired it.

[FlightPathOBN]

"Boeing is going to reduce outsourcing, they have learned their lesson" :ok:

"The 787 production rate is planned to double from five jets per month to 10 per month by year end." :ok:

"Boeing said Friday it will lay off some 800 machinists by the end of this year as workforce needs on its newest jet programs, the 787 Dreamliner and 747-8 jumbo jet, are reduced.
Company spokesman Doug Alder said that other reductions will be made through attrition so that the total number of positions cut this year will be between 2,000 and 2,300." :mad:

Boeing plans to layoff machinists | Business & Technology | The Seattle Times (http://seattletimes.com/html/businesstechnology/2020621699_boeinglayoffsxml.html)

[EEngr]

FlightPathOBN (http://www.pprune.org/members/351467-flightpathobn):

U.S. officials rebuked Boeing for commentsIt looks like Boeing is trying to mount a PR initiative against the NTSB's cautious approach. After all, its the FAA that will have to give the thumbs up/down on flight resumption. The NTSB's input is advisory. So if they are taking the cautious approach by saying 'We're not sure', Boeing is saying, 'We know. Trust us.'

[Cool Guys]

Here we go with the odds thing again

I'm not sure what the issue is with probabilities. Do you think mechanical and electrical devices are perfect? They have a zero chance of failure? Unfortunately this is not true. This is the case for all devices us humans make, including nuclear power stations. There could be another nuclear accident tomorrow, but it is highly unlikely. This is life. This is why we have contingencies and redundancies. If this were not the case every plane would have just have one engine. If there is a 1 in 10 million chance of a blade failure knocking out an engine there is a 1 in 10 trillion chance of a twin engine blade failure. This means the chances are so low that there will probably never be a twin engine blade failure within the time period that humans inhabit earth but unfortunately this is an over simplification. Even though the chances of a twin engine blade failure is so high the chances of hitting a flock of grease and knocking out both engines is probably less than 1 in 10 trillion, but all is not lost, if you hit a flock of geese there is a chance you can still make it safely to the ground with no engines.

Unfortunately with the 787 the chance of battery thermal run away was considerably less than 1 in 10 million (do not know if this is a real probability, it is just what I have read on this thread) It appears the actual chances of a battery failure were down to 1 in 100 thousand. and it seems the contingency for a battery failure, i.e. the containment box had a probability of failure of 100% (in the event of a battery fire) which makes the possibility of a battery fire bringing down the plane an unacceptably high risk which is why the FAA grounded the bird. Hopefully Boeing can get these probabilities back up to where they belong, i.e. 1 in 10 million for the batteries and perhaps 1 in 100 million for the box so the chances of a battery failure and a box failure at the same time bringing down the 787 is so remote that it will probably never occur during the life of the plane.

[inetdog]

Cool Guys:
Even though the chances of a twin engine blade failure is so high the chances of hitting a flock of grease [sic] and knocking out both engines is probably less than 1 in 10 trillion, ...

A lot of people do take the easy way out and say that if the chance of one engine failing it 1 in a million then the chance of two engines failing is 1 in a trillion. That does not take into account that whatever improbable occurrence caused one failure is very likely to cause a second failure at the same time. (As in the flock of geese.)
The meltdown of the US financial derivatives market was not predicted because the SEC statistical experts evaluating the risk assumed that the chances of one mortgage defaulting was independent of the chance of another mortgage defaulting. Instead common causal factors hit them all at once.

[PAXboy]

FlightPathOBN
"Boeing is going to reduce outsourcing, they have learned their lesson" (source ?)

The problem is, I suggest, that they did NOT learn the lesson.

Outsorcing is very complex and requires VERY good managers. Airbus Industrie (the first company name) started in 1970, so they have decades of experiences of making it work.

Boeing started large scale outsourcing with a complex new development and, it appears, made a series of mistakes. If they now pull away from outsourcing, they will have learnt nothing. They had the chance to learn from others and implement outsourcing and development slowly - perhaps with the 73NG range or a new 76 - but they chose to go the fast route and have failed. No one need be surprised.

I am not a particularly advocate of outsourcing but the fault is not outsourcing - but Boeing management and the company will be paying for this for a decade.

[robdean]

..the chances of hitting a flock of grease...

I'm not an expert but I think the term is 'patch' or 'slick'...

:E

[peter we]

Unfortunately with the 787 the chance of battery thermal run away was considerably less than 1 in 10 million

Over a hundred batteries have failed in 50,000 hours, which gives a 1:500 hours failure rate. Over a 10 hour flight thats 1 in 50, the chance of both batteries failing is therefore for 50x50=1:2500. All year flying with a 500 aircraft fleet means 70 dual battery failures per year. And 3500 single battery failures per year.

Mitigating this is Boeing claim that most failures were due to over discharge (which is obviously impossible as its basic preventative circuity requirement). And the less strenuous charging/discharging could make a huge difference - but they would have to find some method to proving this theory with a lot of testing

[Kiskaloo]

FlightPathOBN
"Boeing said Friday it will lay off some 800 machinists by the end of this year as workforce needs on its newest jet programs, the 787 Dreamliner and 747-8 jumbo jet, are reduced.
Company spokesman Doug Alder said that other reductions will be made through attrition so that the total number of positions cut this year will be between 2,000 and 2,300."

The article was specific in noting that these reductions are for personnel working on change incorporation for early-build airframes to bring them up to specification. As the number of those airframes needing said work is reduced, the need for staff is reduced as well.

Heck, the IAM themselves said the reductions were "nothing to be alarmed about" because the demand in other aerospace industries for those workers is so strong they should quickly find new positions.

[glad rag]

Well shucks gee whiz that's okay then.

[FlightPathOBN]

and that they havent sold any 747-8's

[EastMids]

Interesting...

787 Ferry Flights To Resume (http://www.aviationweek.com/Article.aspx?id=/article-xml/AW_03_25_2013_p35-561498.xml&p=1)

[ManaAdaSystem]

“For every battery in service we have a manufacturing record, so we know how each one of the cells behaved when they were tested. We know today which cells will not pass the screening tests and when they return from the fleet we will reject those cells.

Huh? They know they have substandard battery cells on their aircraft?

[Cool Guys]

Huh? They know they have substandard battery cells on their aircraft?

ManaAdaSystem

The statement in the Aviation Week artical is a bit vague but I think you are correct. It seems Boeing have a "manufacturing record" for all cells in service so they can tell which cells will not pass the new tests.

[Cezzna]

Biggest tap dance ever. We have adopted Japanese business practices with all of this 'saving face' and what not. Somewhere there is an engineer waiting to go postal. Or several hundred.

[Max Stryker]

Call me stupid, but I don't get it. Boeing encases the battery in a box and voila! It is magically not only safe, but also exempt from any requrement to actually, you know - work, since the box doesn't address it's reliability in any shape or form.

[toffeez]

I don't know whether this can be called "working":

787 Battery Tests | Video | The Seattle Times (http://video.seattletimes.com/2245764552001/)

[PickyPerkins]

So just how did the cells in the burnt-up batteries behave on test?

[FASRP]

@peterwe:

Over a hundred batteries have failed in 50,000 hours, which gives a 1:500 hours failure rate. Over a 10 hour flight thats 1 in 50, the chance of both batteries failing is therefore for 50x50=1:2500. All year flying with a 500 aircraft fleet means 70 dual battery failures per year. And 3500 single battery failures per year.

That is mathematical nonsense. Let me just replace your numbers with people and it's easy to see how crazy that statement is.

"Over a hundred people have died in less than 100 years, which gives a 1:100 years failure rate. In the first 10 years of life that is a 1:10 chance of dying."

[PickyPerkins]

... Boeing encases the battery in a box and voila! It is magically not only safe, but also exempt from any requrement to actually, you know - work, since the box doesn't address it's reliability in any shape or form. ...

That's right, the box doesn't address the battery's reliability in any shape or form

There two separate problems.

One is the battery problem, and how to make it reliable.

The second is the enclosure, and how to prevent the battery from damaging the aircraft. The enclosure is not intended to contribute to the reliability of the battery. The other changes are intended to take care of the battery problem.

But now we have a third task; how to ensure that the stainless steel enclosure is itself manufactured, assembled, and maintained adequately.

[Blacksheep]

The battery is being so heavily modified it isn't the same battery any longer:
1. Improved cell manufacturing process
2. Additional testing of completed cells.
3. Larger cell relief vents
4. Ceramic heat shielding between cells and between cells and battery case.
5. New intercell link nuts
6. Reduced maximum charge voltage limit combined with increased minimum cell discharge voltage
7. Modifications to the battery internal electronic monitoring logic that monitors cell balancing, charge levels and temperature.
8. Modifications to the battery charger, to accommodate the revised charge/discharge figures.

Then we come to the containment box.
3mm thick stainless steel case with the lid held on by 52 bolts! Scheduled battery changes now become a two hour job. Is it necessary? Will the public be reassured by a modification that includes putting a part of the aircraft into an explosion proof container, or will they assume that an unacceptable risk of serious failure remains?

I think the answer lies in many of the above answers by those unaware of the actual situation. This whole thing has been and remains a pR disaster.

[fizz57]

@FASRP

Peterwe's method of analysis is valid (I haven't checked the numbers) if you assume a constant failure rate, which is typical in mid-life of most objects subject to failure - including people.

The failure rate typically follows a "bathtub curve" with a high initial failure rate, a constant and (hopefully) low rate in mid-life, and then another increase due to old age.

The initial failures are normally screened off by factory stress testing or burn-in - one would hope that the parts Boeing are using have been sufficiently screened. The old-age failures would be avoided by mandating replacement before the bathtub curve starts rising.

From a reliability point of view, what we're seeing with these batteries is either an unexpectedly long infant mortality period, an elevated mid-life failure rate, or a premature ageing: we don't have the numbers to plot the graph and determine which, but Boeing certainly does, and has probably covered these bases with the proposed actions (the other two that don't get much mention here, not the containment vessel which is there just to keep the FAA happy).

[jbcarioca]

That is certainly correct. Boeing has failed to accept culpability in any meaningful way, and insists there never was a major problem. Denial, regardless of the facts, probably is not an optimal response in a situation in which the outcome depends on good will from the party that grounded the aircraft. Upsetting the NTSB is not the same thing at all, since the NTSB has no regulatory function.

Boeing, by intransigence, has given a PR festival to anti-Boeing forces. I wish they were better at such issues. Is has not helped their case that they have announced layoffs more than once since the grounding, insisting they're unrelated.

My opinion of Boeing has become negative since these events, less for the events themselves than for their actions since the grounding.

[FERetd]

Blacksheep, Quote:- "The battery is being so heavily modified it isn't the same battery any longer"

So a "different" battery that still requires a 3mm stainless steel case?

Doesn't show much confidence in the redesign, does it?

[gas path]

Doesn't show much confidence in the redesign, does it?

That box is the PR bit. Having been in Seattle and been party to some of the detail I for one wouldn't have any problem flying on the a/c with just the modified battery. :p

[s e t h]

so one presumes this new fix and 'pr' box has been designed and approved by the exact same engineers using the exact same technology and the exact same oversight as the previos design that everyone said was perfect?

have the same fixes been applied to both batteries or just the ones that caught fire last time?

every RC hobbyist on the planet knows lithium batteries are an accident waiting to happen

i just hope it doesn't take a 787 Helderberg before boeing wakes up

[toffeez]

The FireBox is the worst PR anyone could imagine.

180 mins with an inferno blazing under seat 30H?

PR? Ho Ho.

[Pub User]

Guys, this is supposed to be a professional pilot's forum. If you are going to express yourselves in the sensationalist manner of the (British) gutter press, then you are doing the forum an injustice.

[ITman]

Sadly the truth always hurts regardless of the amount of marketing hype and blah blah.

[RatherBeFlying]

Well a 3 mm steel box is pretty strong -- and heavy:p

Presuming the melting point is above what a runaway battery will produce, the box will also keep oxygen from supporting combustion.

The next question is what will happen to surrounding components and structure from the high temperature?

Hopefully maintenance will be able to disconnect the entire box and take it to the bench to extract the battery.

[mikecsboats]

I thought the problem centres around the fact that lithium batteries produce their own oxygen? In which case any potential fire would not necessarily extinguish inside a container, no matter how airtight.

[A4]

The next question is what will happen to surrounding components and structure from the high temperature?

So why not then surround the box with a similar material to the Space Shuttle protective tiles? HUGE thermal capacity and they weigh practically nothing but should prevent heat transfer to surrounding components.

I too cannot see what this test flight can possibly hope to achieve - unless they replicate a runaway event to ensure that venting takes place as per design. If they just fly it and say "look - it didn't burn" that's not going to get me anywhere near a 787 anytime soon.

This whole thing is being driven by PR. I bet 95% of the public probably have absolutely no idea of the events surrounding the grounding, the "fix" or the implications of a battery fire on board. The customer airlines are caught between a rock and and a hard place - they, in private, may be extremely unhappy with the "solution" but have to put on a public face of "business as usual" and we are fully confident in our product as they have already lost millions and the implications going forward are many times that.

If a 787 subsequently has a serious event after this fix is released.......:\

[fgrieu]

Blacksheep wrote:
The battery is being so heavily modified it isn't the same battery any longer:
1. Improved cell manufacturing process However Boeing is quoted as:
"For every battery in service we have a manufacturing record, so we know how each one of the cells behaved when they were tested. We know today which cells will not pass the screening tests and when they return from the fleet we will reject those cells."that's here
787 Ferry Flights To Resume (http://www.aviationweek.com/Article.aspx?id=/article-xml/AW_03_25_2013_p35-561498.xml&p=2)

If there is a plan to recycle some of the cells returning from the fleet, then there is no redesign of the cells, and only the screening is modified. Seems the most likely, because there was not enough time for a cell redesign and qualification of that.

[cockney steve]

@FASRP...you are well off the ball....
try:- 250 people spent , collectively, 50,000 hours , two at a time, in any one of fifty rooms.
150 of them died during their occupancy :ooh:

That'sthe scenario at "grounding"
Total in-service fleet=50 each containing 2 "serviceable" batteries.

"dead" batteries replaced:- 150

Total hours flown, 50,000 divide total stock into hours flown and you get an average service-life of 200 hours

@ Seth Welcome !...As you'll see, this lot don't take prisoners!:} but a great place for an intellectually stimulating debate.

I' m presuming you meant "Hindenberg "? the infamous Hydrogen-filled Airship.

@ Blacksheep. Totally concur with your remarks , re the firebox.
It's a total victorian-engineering , heath-Robinson lash-up.

52 bolts????WTF -it's supposed to vent at ~ 6000 feet cabin-altitude.
The plate-box already has a lip flange....make the sides and back much bigger and fold back on themselves(upwards)....you now have a slot/runner turn a lip down on the front of the lid. When slid home, the lid and case are securely clamped on all 4 sides...a bolt through the 3 thicknesses,say every 3 inches , would stop any bowing and be mainly in shear.. 12 should do all 4 sides.

Re-ceramics....-been saying this for a long time IMHO each individual sub-cell should be fully thermally insulated and fully monitored for charge-discharge.

These people appear to be attacking the problem from the wrong end!

Preventing an out -of -service battery is a much better "fix" than containing the thermal runaway when one does go TU.... No doubt some of the real Boffins on here can accurately calculate just how much heat-energy is disemitted by 32V 70 Ah discharging in an uncontrolled thermal "event".

[Volume]

787 Battery Tests
This extract from a Boeing video shows a severe test of the proposed 787 battery containment enclosure. Propane gas ignited inside the box explodes. The 1/8th-inch thick steel walls bulge out but hold fast.
So if a box of that size filled with a propane-air mixture holds the same energy than a fully charged battery, then maybe the idea of the cartridge APU starter was no too far off, we just have to route the overborad vent line to the APU, and voilá we have the perfect APU start energy source. A propane-in-a-box cartridge starter. Probably not 16k$ each as well...
Seriously, which percentage of the energy stored in a fully charged battery has been released in this test? My rough estimation is about 2% (Propane having 28.2 kWH/m³, Battery having 75Ah at 29.6V with a size of 15x11x9 in... according to NTSB)

"Over a hundred people have died in less than 100 years, which gives a 1:100 years failure rate. In the first 10 years of life that is a 1:10 chance of dying." So taking into account that a birth takes in average 2 hrs, there is a 1 in 438000 chance to die during birth... Which is a quite optimistic number.
Statistical fugures do only work, if you look at a large enough population/timeframe. So the estimation over 500 aircraft and one year was probably much more realistic than a chance of death during a fraction of the MTBF...

[Frequent Traveller]

Whatever we may think of the firebox, the Proof of the Pudding is in the eating, they say : three testgroups will be called upon to feel the taste of this Boeing battery pudding : (1) Underwriters, who'll quote revised or unchanged fees for the insurance of the modified 787s ?; and (2) travellers, who'll fly or not with 787s ? :cool:

The first group are professional statisticians, they will trim their new quotations to the tune of the firebox' anticipated probabilistic impact upon the overall safety of the 787 and its systems, thoroughly re-assessed. In the background, you have the considered opinion of Lloyd's re-insurance experts. Those people - a special class of 'no-nonsense' bargainers - will tell us whether Boeing were right or wrong ? :confused:
A third group of pudding-tasters : 787 flight and cabin crew ? :hmm:

[FlightPathOBN]

cockney...the bolts would be in tension, not shear...

given that about 150 batteries have been replaced, and the issues, dont you think routine inspection would be in order? So those 52 bolts times 2 boxes..

The test noted that moisture buildup inside the existing box may have been a cause of the short....what is to prevent that in this box?

What about the other Li battery, the backup for the avionics?

I see that most of the news regarding test flights beginning this week is now gone....perhaps the NTSB warning from their lead counsel to Boeing had something to do with that..

[s e t h]

thank for the welcome cockney steve :)

Helderberg was the name of the South African 747 that burnt to a crisp mid air and fell into the sea off Mauritius in the 80's killing everyone

South African Airways Flight 295 - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/South_African_Airways_Flight_295)

[syseng68k]

The other thing about statistics and mtbf is that the figure is not time to next failure.
That is, the mtbf may be calculated as 1 in 10 e6 hours, but that single failure could
happen today, tomorrow, or next week.

As for condensation causing failure, just more red herring bs. Condensation is pretty
much distllled water, which is an insulator. Even with minor impurities, irrelevant
compared to battery charge / discharge currents......

[Mark in CA]

Blacksheep: Will the public be reassured by a modification that includes putting a part of the aircraft into an explosion proof container, or will they assume that an unacceptable risk of serious failure remains?
Um, isn't this how atomic power plants are designed?

[StoneyBridge Radar]

Engines started for the first flight in a while...

Boeing #272 Flight Tracker (http://uk.flightaware.com/live/flight/BOE272)

It's LN86, a LOT example.

Boeing is on the verge of flight testing the modified 787 battery system changes on Line Number 86, an aircraft destined for LOT Polish Airlines. The aircraft is set to undergo a final pre-flight ground test in the afternoon (Pacific time), at Paine Field, Everett on 24th, and if all goes to plan could be cleared for a standard ‘B2’ profile, customer acceptance type flight test on March 25.

Boeing sets up for 787 battery flight test (http://www.aviationweek.com/Blogs.aspx?plckBlogId=Blog:7a78f54e-b3dd-4fa6-ae6e-dff2ffd7bdbb&plckPostId=Blog%3A7a78f54e-b3dd-4fa6-ae6e-dff2ffd7bdbbPost%3Aa71731f4-1598-4e70-89c5-c0edf1740593)

[peter we]

That is mathematical nonsense. Let me just replace your numbers with people and it's easy to see how crazy that statement is.

You don't understand statistics or engineering.

[EEngr]

Anyone have the details of the box and ventilation design handy?

Will this box be sealed during normal operations? Or will there be positive ventilation overboard through an outflow port?

[EEngr]

Boeing #272 Flight Tracker (http://uk.flightaware.com/live/flight/BOE272)

At the moment, it appears to be heading out over water instead of close to the coast.

I hope there's nothing they need to douse.:eek:

[Chu Chu]

I suspect the propane test was to simulate gasses from a thermal runaway mixing with the air in the box and igniting. I haven't heard of a scenario in which the battery's potential energy could be released instantaneously. Were that possible (which I doubt) I suspect the result would be rather grim.

[ATC Watcher]

A question crossing my mind after watching the propane video : Just imagine the lid of the box ( or the whole box) does not really hold in case of a thermal. runaway. Could the explosion , and the velocity of the steel parts flying around in this confined Electric bay area cause more dramatic destruction than a fire ?

I understand Halon 1301 is an oxygen depletive, so I do not understand why a massive Halon discharge in A CLOSE area in case of a Li-ion fire would not work ? Different story in an open area of course. but inside a box ?

[inetdog]

Pub User:
Guys, this is supposed to be a professional pilot's forum. If you are going to express yourselves in the sensationalist manner of the (British) gutter press, then you are doing the forum an injustice.
Right! Professionals should confine themselves to reporting and discussing Rumors (& News), not starting them.
Now if you find a sensational tabloid rumor on the subject, I suppose you are free to report it and even quote it. :p

Rumours & News: Reporting Points that may affect our jobs or lives as professional pilots. Also, items that may be of interest to professional pilots.

[Cool Guys]

Pub User

Guys, this is supposed to be a professional pilot's forum. If you are going to express yourselves in the sensationalist manner of the (British) gutter press, then you are doing the forum an injustice.

I agree with you. Some people also seem to be using this forum to practice their comedian skills.

The improvements to the batteries and containment box seem to be addressing the safety requirements stipuated by the FAA. I felt depressed seeing all these great planes parked up when I flew out of Haneda last night. I am quietly optimistic it will be flying again in the next few weeks. If the 787 is on the schedule for any of the routes I take it will be my first choice.

[Tommytoyz]

"The battery is being so heavily modified it isn't the same battery any longer:"

What has not changed, as far as I know, is the cell chemistry. They're still Cobalt Oxide Batteries (COO2). The most volatile and also the most energy dense of all Lithium based battery chemistry's. No amount of shielding will change the chemical properties of that battery. In that sense, the battery remains identical.

What Boeing is doing in my uneducated view, is hazard mitigation, not cause elimination. Maybe charging and discharging them within a narrower band will make the battery more reliable. Maybe not. Until many have been operated for a statistically useful period, nobody will really know for sure. Even if the new shielding makes them safe, that does not speak to reliability.

Why they didn't switch to a different battery chemistry is really beyond me. What Boeing is doing seems too high risk to me.

[esa-aardvark]

Having once been involved in a very large fire whereby halon
was released, I can say that halon reduces fire by interfering
with the combustion process. In my case it was safe for humans
to be exposed to the halon atmosphere for in the order of hours.
That said surely halon might be useful in the boeing battery box.
If it is certain that there is no way for the contents of the box to
generate oxygen, then an inert atmosphere of any kind should
also work. If the batteries have a major short there still remains
the problem of the heat generated.

By the way, I looked up the battery rating of my ancient diesel's
12v lead acid battery and it is 920 amps for 30 seconds,
with a final voltage of at least 6 volts, and chemical recovery thereafter.
Still I suppose Boeing chose their particular li-ion
technology for some good reason. I see that many electric cars
use li-ion manganese. For the 'ZOE' the makers state that all
cells are monitored for condition, and charging is possible from any state of charge.

[peter we]

The improvements to the batteries and containment box seem to be addressing the safety requirements stipuated by the FAA

Lets be clear here. the FAA said the improvements to the battery were a step towards solving the safety issues with the 787.

The battery box is not a fix or solution to the problem according to the FAA.

No matter what Boeings PR depart claim, until the problem is identified and a solution provided, the 787 is not going to be flying commercially.

Boeing just might be able to lobby the FAA but I doubt the Japanese, Europeans or the NTSC will be so easily to push around.

In my case it was safe for humans to be exposed to the halon atmosphere for in the order of hours.

Halon damages the liver and its unpleasant to breathe, the first time its used in a commercial aircraft would probably be the last, after the lawsuits.

[Cool Guys]

Peter We

The battery box is not a fix or solution to the problem according to the FAA

The JAL Boston and ANA Takamatsu incidents highlighted 2 issues:

1. The battery failure rate (thermal runaway) was considerably higher than expected.

2. The original battery box did not contain the fire which it is supposed to do in the rare instance that there is a battery failure. Special rulings were issued by the FAA during the 787 delvelopment on this. Sorry I have no time to go back through this thread to find this data.

The battery modifications such as the extra insulation between cells addresses issue 1. The stronger box addresses issue 2.

[Frequent Traveller]

@ Cool Guys, re your point 2 : I can't see how the Stainless Steel casing has in any significant way changed the occurrence probability of 'Battery Unserviceable' as an EVENT; (refer to cockney steve in post # 1446) the present-day statistics show some 150 such events in 50,000 flight hours ... the question then comes : is this a 'no-go' event ? The next question is : what is the duration of 'change battery' as a line maintenance task ? (consider that henceforth the battery is to be encased in a sealed - explosion-proof - box, did you count the number of bolts/nuts = 52 ? - what about 'visual inspection' ?) Corollary : does this imply an aircraft change ? ... whence the possible concern of Underwriters : what exactly are we insuring, and for what premium ?

[Kerosene Kraut]

Did yesterday's flight use the new battery box or still the factory stock layout?

[Cool Guys]

Frequent Traveller,

I can't see how the Stainless Steel casing has in any significant way changed the occurrence probability of 'Battery Unserviceable' as an EVENT

You are right, the box makes no differnce to the probability of a battery failure. The issue is the batteries will fail at some point. They are not 100% reliable, nothing is. The Li batteries have a high energy density so when whey do fail the fire etc must be contained.

statistics show some 130 such events in 50,000 flight hours

Apparently most of these events were due to excessive discharge while on a ground. When an LI battery is discharged below its minimum level it should not be recharged up to normal levels again so it is replaced. I am not an expert on this but some smart people earlier in this thread explained this. This is not a safty issue.

what is the duration of 'change battery' as a line maintenance task ?

I have no idea. I am sure it will be complete pain in the ar_e to service but this is not a safety issue.

does this imply an aircraft change ? ... whence the possible concern of Underwriters ?

I have no idea.

[cockney steve]

@ FlightPath OBN....Sorry, I didn't explain my thoughts very clearly....the box-flange is currently about an inch wide.....double it and add the thicknesss of the lid.....fold it back on itself, thus forming a slot...do that on 3 sides and the lid will slide into the slot....bolts (same relative position as the plastic-fronted "Demo" box)would only have tension if a pressure-event tried to force the lid upward....remember it's restrained by a 1" wide cpntinuous flange folded over 3 sides....If the top belly's it will try to pull out from the slot....the flange, being 2 thicknesses with a fold, is unlikely to bow outward anyway....but any bowing tendency would give shear on the bolts....lighter and stronger and cheaper to produce ehan what appears to be a cast /welded flange on the box as pictured....also the lid has nothing stiffening the edge-that's why the bolts have to be so close and so plentiful- to stop the tin-lid blowing between them.

As for maintenance- it's a sealed unit- uncouple the cables, uncouple the vent-pipe, heave out the "dead" box and shove in another....same as before, just a "bit" heavier and a drain to disconnect/reconnect.


@ Seth. Thanks for the correction :O Fascinating reading.

@Syseng. I agree with you , re Condensation....any present across the "live" bits would electrolyse and would "self-heal" anyway....bit of an old wives' tale, like the film-scenario of an electric-fire being chucked in a bath/swimming-pool and electrocuting the occupant(s).....fuse usually blows first!....pos-neg-earth about 5mm apart water, same resistance per linear distance, so victim more than 10 Cm away, is virtually insulated.

@ Mark in CA....Atomic Power Plants are normally occupied by professional engineers, who usually know what they're doing (unlike commercial Pax.)
When they foul up, you getCHERNOBYL ....Nuff said?

[Pub User]

Halon damages the liver and its unpleasant to breathe, the first time its used in a commercial aircraft would probably be the last, after the lawsuits.

Halon (BCF) fire extinguishers are standard cabin equipment, and have been discharged many times in flight, in commercial aircraft. Their toxicity is the reason we are told to don a smokehood before use, if possible.

[Volume]

Apparently most of these events were due to excessive discharge while on a ground. [...] This is not a safty issue.As far as I understood, excessive scharge will make the cells instable and lead to thermal runaway. With that respect, discharge is a safety issue. However, it seems to be perfectly prevented by the integrated logic, switching off the battery and making it unserviceable if it is discharged below a defined (still safe) threshold. So the overall Boeing design for this aspect worked perfectly for safety, but is a nightmare for maintenance cost / unscheduled removal.

[Ex Cargo Clown]

Surely there's a very important Ops aspect to this. You can't ship Li on Pax A/C ! So is every outstation going to have have a huge stockpile?

[FullWings]

That said surely halon might be useful in the boeing battery box.
If it is certain that there is no way for the contents of the box to
generate oxygen, then an inert atmosphere of any kind should
also work. If the batteries have a major short there still remains
the problem of the heat generated.
Unfortunately, LiCoO2 reacts with the electrolyte above c. 130C and decomposes approaching 200C, giving off oxygen in the process. This becomes self-sustaining, i.e. thermal runaway. Halon will suppress naked flames by interfering with the chemistry but can't do much about what's happening inside the cell.

The total energy release from an electrical short and combustion of the materials that make up the battery is enough to raise the temperature by *thousands* of degrees. This would actually be made worse by insulation - disrupted cells get hot enough to melt steel... :eek:

From the FAA 787 "special conditions" for Li-ion:

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

Note that it doesn't say that it's okay if they are in a box, or if it only happens every now-and-then. LiCoO2 batteries are vulnerable to the above due to their chemical composition - whether it is triggered by over/under-charging, excessive current, manufacturing defects, cosmic rays or a change in interest rates, doesn't really matter. So far, there has been no (public) confirmation of *why* these failures occurred, so pushing a solution seems ever so slightly premature.

I do wonder how they're going to get round this provision: either the FAA will have to retract the offending paragraph or Boeing will have to use a different type of battery. I suppose the third way will be to argue "we don't know what caused it but we've changed lots of things so it's OK now"; depends on how much spine the regulator has that morning, I suppose...

[green granite]

I do wonder how they're going to get round this provision: either the FAA will have to retract the offending paragraph or Boeing will have to use a different type of battery. I suppose the third way will be to argue "we don't know what caused it but we've changed lots of things so it's OK now"; depends on how much spine the regulator has that morning, I suppose...

Or perhaps a compromise could be reached for the FAA to say OK so you have done some substantial changes to the battery and given that if it should fail the box will prevent it from setting fire to the aircraft, we will give you a CofA but with a temporary restriction of 180mins ETOPS only, (ie the same as for a non functioning APU.) if after 12 months there have been no more incidents then we will lift this restriction. They could also demand that any batteries swapped out and returned to the manufactures are opened in the presence of an inspector from the Japanese regulators.

[WHBM]

Surely there's a very important Ops aspect to this. You can't ship Li on Pax A/C ! So is every outstation going to have have a huge stockpile?
They will have to be shipped out by freighter aircraft. I believe that UPS have experience with shipping this type of cargo, notably around Dubai ..........

[toffeez]

Airbus has installed on the first flight-test A350 XWB its two flight-ready Rolls-Royce Trent XWB engines and is also installing the new Honeywell HGT1700 APU.

"With the installation of its engines and also the APU, the A350 XWB MSN001 becomes essentially a ‘completed’ aircraft. Following the ongoing ground tests, other preparations and also painting in the coming weeks, MSN001 will then be handed over to the Airbus Flight Test team to commence preparations for ground runs and maiden flight in the summer."
.

[fgrieu]

LiCoO2 reacts with the electrolyte above 130°C and decomposes approaching 200°C, giving off oxygen in the process.My understanding is that any oxygen recombines with the anode material as it is produced, with heat and non-combustible byproducts; if the anode is graphite, which I conjecture is the case, that would be CO2 for a large part.

Any good sources on the exact chemistry in the battery, and how it degenerates in case of thermal runaway ?

Also, independently
(2) Design of the lithium ion batteries must preclude the occurrence of self-sustaining, uncontrolled increases in temperature or pressure(..)I do wonder how they're going to get round this provision: either the FAA will have to retract the offending paragraph or Boeing will have to use a different type of battery. I suppose the third way will be to argue "we don't know what caused it but we've changed lots of things so it's OK now"; depends on how much spine the regulator has that morning(..)This is from http://www.gpo.gov/fdsys/pkg/FR-2007-04-30/pdf/E7-8186.pdf

Any advise on how this could be worked around by Boeing from a legal standpoint? Especially since the design of the cells remains apparently unchanged (only their testing is), and experience has proved that self-sustaining uncontrolled increase in temperature is a real possibility.

Edit: Perhaps uncontrolled is a solution: now that there is the fire box/enclosure, any self-sustaining increase in temperature or pressure is arguably controlled. Or perhaps Boeing can waive the special conditions and re-certify according to general rules.

[inetdog]

fgrieu:Any good sources on the exact chemistry in the battery, and how it degenerates in case of thermal runaway ?

Lithium Battery Failures (http://www.mpoweruk.com/lithium_failures.htm) gives a good overview.

http://www-scf.usc.edu/~rzhao/LFP_study.pdf gives a deeper look at the normal chemistry of Lithium ion batteries.

Types of Lithium-ion Batteries (http://batteryuniversity.com/learn/article/types_of_lithium_ion) compares different variations on the Lithium ion chemistry.

http://www.kta-ev.com/v/vspfiles/assets/images/intertek-battery-technologies.pdf gives another overview of alternative Lithium chemistries, including some safety information and includes the useful point: From a thermal/safety perspective, cobalt is generally considered the least stable cathode chemistry, but among the highest in terms of energy density.

I found a very good scholarly analysis of the exact anode, cathode, and electrode reactions involved in thermal runaway, but I don't have the URL handy at the moment. Possibly later.

[pax britanica]

"Surely there's a very important Ops aspect to this. You can't ship Li on Pax A/C ! So is every outstation going to have have a huge stockpile? "

I assume you cannot ship them because of the potentail risk involved?

So how can it be say to fly around an aircraft with two highly rated LI units bolted to the airframe, I assume I am missing something here.



Pax Brit , but not on a 787 any time soon

[peter we]

The battery modifications such as the extra insulation between cells addresses issue 1. The stronger box addresses issue 2.

Neither address the problem, the cause of the failure. This is why the FAA describe the changes as 'improvements' and a not a fix, solution or answer to the problem.

Apparently most of these events were due to excessive discharge while on a ground. When an LI battery is discharged below its minimum level it should not be recharged up to normal levels again so it is replaced. I am not an expert on this but some smart people earlier in this thread explained this. This is not a safty issue.

I don't believe this. Every LI battery has protection against such possibilities because of the well known danger. A $16k battery in a critical safety situation with a revolutionary over/under charging system failed in its most basic task?

[inetdog]

peter we:I don't believe this. Every LI battery has protection against such possibilities because of the well known danger. A $16k battery in a critical safety situation with a revolutionary over/under charging system failed in its most basic task?
Comments have been made about this, and the only information I have seen is that there is undervoltage protection in the BMU at the cell level which will disconnect the battery and/or notify the BCU which will disconnect the battery.
But once that has been done, the battery is locked into this state and must be returned to Yuasa.
Based on more information since then, I suspect that part of the problem may be that the protective contactor inside the box is Normally Closed, so disconnecting the battery at that point requires constant power consumption which might take the battery from there down to the irreversible level for the cell or cells involved. Or at least requires Yuasa to evaluate its condition.
In the event of overcharge, using an NC protective contactor would be just fine.
Unless, of course, a failure inside the battery of one or more cells dropped the voltage below the operating point of the contactor.

[Cool Guys]

Neither address the problem, the cause of the failure. This is why the FAA describe the changes as 'improvements' and a not a fix, solution or answer to the problem.


The stronger box is addressing numbers 3, 4 & 5 of the FAA's proposed special conditions.

http://www.gpo.gov/fdsys/pkg/FR-2007-04-30/pdf/E7-8186.pdf

[Anilv]

Quoting Pax Britanica
I assume you cannot ship them because of the potentail risk involved?

So how can it be say to fly around an aircraft with two highly rated LI units bolted to the airframe, I assume I am missing something here.


Commercial airliners are equipped with all kinds of dangerous goods, off the top of my head
-flammable liquids- a B744 can carry almost 170 metric tons of fuel. Try calling Fedex and telling them you want to ship 1 bottle of kerosene!
-Oxygen generators - see Valuair
-Compressed Air - Compressed gases are considered as dangerous goods, things like emergency slides, oxygen bottles and even fire extinguishers.
-Deleted uranium - used as weights (I believe 747 uses them in the stabilizers) and while safe to handle I would imagine shipping them will require them to be classed as dangerous goods.


It is possible to get exemption for extremely dangerous items to be carried.

There was a flight in the early 90s transporting a radioactive shipment from Frankfurt to the US. I was supposed to be the loadmaster on board but the permit issued only allowed 'person neccssary for the operation of the flight' so I got bumped off. The item was about the size of a largish oil-drum and weighted about 3 tons. This was a single use charter so only this item was loaded on the 747. Might not work for 787 batteries on aregular basis tho

This was an exceptional case, however lower grades of radioactive material can even be carried on passenger aircraft, here the loading height has to be observed (to have safe distance from the parcel to the roof (which is the floor of the passenger cabin).

On the freighter aircraft I worked on, there would be an Emergency Response Guide on board which gives info on how to handle different types on incidents with DGR.

[s e t h]

just in case anyone is wondering what the terms 'venting' and 'thermal runaway' are more commonly known as.
the PR department clearly doesn't want to use 'explosion' or 'fire' when talking about the batteries. :suspect:

the action starts at 2minutes through the video

Lithium Ion Battery Explosion - YouTube (http://www.youtube.com/watch?v=SMy2_qNO2Y0)

[TURIN]

Quote:
Apparently most of these events were due to excessive discharge while on a ground. When an LI battery is discharged below its minimum level it should not be recharged up to normal levels again so it is replaced. I am not an expert on this but some smart people earlier in this thread explained this. This is not a safty issue.

I don't believe this. Every LI battery has protection against such possibilities because of the well known danger. A $16k battery in a critical safety situation with a revolutionary over/under charging system failed in its most basic task?


What I think is happening here is the battery is designed to be allowed to discharge below it's minimum recharge value. This gives the a/c an extra few minutes of emergency power when required. The operator sacrifices the battery to ensure the whole a/c survives.

Where things have gone wrong (re: 150 batteries changed in service) is the operators have not really ensured that the people at the sharp end are thoroughly briefed as to the consequences of EG. Leaving the towing switch on.

The charging is not the issue (for the 150 battery swaps).

[ITman]

Interesting that the Japanese seem to have a better handle on the situation than the FAA.

Accident: ANA B788 near Takamatsu on Jan 16th 2013, battery problem and burning smell on board (http://avherald.com/h?article=45c377c5&opt=0)

At the same time there is another YUSA battery problem this time on a electric car...

"TOKYO: Japanese automaker Mitsubishi Motors on Wednesday asked 4,000 owners of its hybrid and electric cars to avoid charging their vehicles pending an investigation into overheating batteries.

The move follows the melting of a lithium battery pack in a hybrid Outlander that was due for sale earlier this month, as well as a fire triggered by an overheating unit in a factory which produces the MiEV electric vehicle.

No one was injured in either incident nor was there damage to facilities.

Nearly 4,000 units of the plug-in hybrid model have been sold since its launch in January, "and we asked its owners not to charge the batteries until the cause of the incident can be confirmed," a company spokeswoman said.

The company has sold at least 68 units of its fully electric vehicle with the same battery model.

"We suspect the two cases were caused by a change in the production line of the battery supplier," the spokesman said, adding that the company had not received any similar complaints from owners of the two models.

The troubled batteries were made by a joint venture formed by Mitsubishi Motors, Mitsubishi Corp. and GS Yuasa.

GS Yuasa drew global attention over the worldwide grounding of Boeing's next generation aircraft in January after a battery on a Japan Airlines 787 caught fire and forced an ANA flight to make an emergency landing.

GS Yuasa has the contract for all Dreamliner batteries. Japanese authorities have said they had found no major problem on the company's production line making batteries for Boeing's Dreamliner."

[Mark in CA]

The wire connecting the battery case to ground was broken and showed evidence of having been blown (editorial note: implicitely [sic] suggesting prior to the battery event), however, the aircraft had no history of a lightning strike.

Does this suggest a static buildup situation, perhaps along the lines of what Baron 58P suggested a while back? (FAA Grounds 787s - Page 64 - PPRuNe Forums (http://goo.gl/dx0aQ))

[WHBM]

Where things have gone wrong (re: 150 batteries changed in service) is the operators have not really ensured that the people at the sharp end are thoroughly briefed as to the consequences of EG. Leaving the towing switch on.
I think this is a bit inappropriate, trying to stick it on the front-line staff at ANA and Japan AL (the two principal 787 operators so far, with more than half the total deliveries between them), and on their technical and training staff, for letting 150 batteries at USD 16k each go phut just by leaving a switch on. Remember this is a cutting-edge piece of critical kit, with every bit of software management known to engineering (supposedly) built all around it to keep it in good condition.

[green granite]

Do you have loads of Ni-Cad batteries being swapped out because people leave the towing (or similar) switch on? If not why not?

[TURIN]

In reverse order...

Do you have loads of Ni-Cad batteries being swapped out because people leave the towing (or similar) switch on? If not why not?

No, because...
1. On all other a/c, the towing switch (if fitted) does not send battery power to operate the brakes. Just lights and radio.
2. Ni-Cads, if exhausted, can be rechargd on board the a/c. (Assuming there is enough wiggly amps left to get the ground power on or a seperate battery to start the APU.) The APU battery on a 787 also supplies lights during towing on battery.

I think this is a bit inappropriate, trying to stick it on the front-line staff at ANA and Japan AL (the two principal 787 operators so far, with more than half the total deliveries between them), and on their technical and training staff, for letting 150 batteries at USD 16k each go phut just by leaving a switch on. Remember this is a cutting-edge piece of critical kit, with every bit of software management known to engineering (supposedly) built all around it to keep it in good condition.

Don't get me wrong please. I lay any 'blame' if such exists, firmly at the door of Boeing for not labouring the point (IN LARGE RED LETTERS) during the initial (Boeing delivered) training courses.

It's certainly not something I remember being enforced during my course in Seattle.
Boeing train the airline trainers don't forget. :ok:

[E_S_P]

@ITman good article/photos. :ok:

Are there any other photos knocking about actually showing this "Evidence of large current" as shown/mentioned in the 1st diagram in Accident: ANA B788 near Takamatsu on Jan 16th 2013, battery problem and burning smell on board (http://avherald.com/h?article=45c377c5&opt=0) - specifically between the battery contactor and the BDM?

With "high current" indications occurring before the blocking diode, it points to either an under spec'd design/components which cannot handle the design loadings, or 'something' has drawn excessive current through this area during the meltdown. I would therefore be very interested to see a before and after shot of this area / component if one exists.

The battery case earth (ground) wire looks like it may have blown similar to a fuse, so it would be nice to see if the actual battery ground wire has also suffered "high current" events as well.

[green granite]

Thanks for clarifying that TURIN, it's been about 50 years since I did any work on Aircraft and that was a military Comet 3

[keesje]

The third, smaller Li Ion battery, installed above the big one front of the aircraft, with small holes at the corners, that got slightly damaged according to the NTSB, will it also be re certified?

http://tribkcpq.files.wordpress.com/2013/01/battery.jpg

[Ex Cargo Clown]

I've dealt with RRY and RFL I really wouldn't want Li on any aircraft I was onboard

[SMT Member]

Speaking of transporting Li-Ion batteries as cargo. The bible (IATA DG) allows it, under certain circumstances, to be loaded on the main-deck of freighters. I know of one all-cargo airline who said "bollocks", and mandated all RLI and RLM be loaded lower-deck only, which is a Class C (fire suppression installed) compartment on their aircraft.

The decision was made following a very exhaustive investigation, during which a couple of packages containing Li-Ion batteries caught fire in warehouses around the world. That might have sharpened people's attention, but the decision to impose any kind of restrictions involving the carriage of Li-Ion's was met by a tremendous amount of pressure from the commercial department. Not surprising really; integrators carry an obscene amount of electronics, much of it containing batteries. The airline was actually more intent on banning the things outright, but the compromise "Class C compt. only" was made. For commercial reasons, not safety.

[Kiskaloo]

keesje
The third, smaller Li Ion battery, installed above the big one front of the aircraft, with small holes at the corners, that got slightly damaged according to the NTSB, will it also be re certified?

No.

Like the Li-Ion batteries used to power the emergency lighting on the 787, A380 and A350, it's too small to be considered a dangerous risk.

[mickjoebill]

if a lithium battery is discharged to such a level, no re-charging should occur !

There has been little written about the charging curcuits and I wonder why state of the art technology seems not to have been employed?

Battery chargers made for professional broadcast camera batteries diognose each battery and adjust and regulate the charging according to the health of the battery.https://www.paguk.com/sites/default/files/pdf/Why_Choose_PAG_Chargers.pdf

These intelligent chargers don't need seperate thermal sensors, just two wires to the battery. A micro computer uses algorythms to ensure the battery is not overcharged. The microcomputer can even sense the chemistry of the battery and can run a discharge/charge program. Each battery has a chip so the charger recognises its charging history. This kit designed to work with up to 17 volts and is available for a $1k!

What safty features designed into the Dreamliner charger?

[mickjoebill]

Nearly 4,000 units of the plug-in hybrid model have been sold since its launch in January, "and we asked its owners not to charge the batteries until the cause of the incident can be confirmed," a company spokeswoman said.

Yuasa shares fell 11% in the last few days, according to this report..
The cars had not even been shipped to customers.

Dreamliner battery maker's shares plunge | News.com.au (http://www.news.com.au/business/breaking-news/dreamliner-battery-makers-shares-plunge/story-e6frfkur-1226608645337)

[Cool Guys]

mickjoebill
I wonder why state of the art technology seems not to have been employed?


I think TURIN gave the most likely explanation for this.

What I think is happening here is the battery is designed to be allowed to discharge below it's minimum recharge value. This gives the a/c an extra few minutes of emergency power when required. The operator sacrifices the battery to ensure the whole a/c survives.

[mickjoebill]

This gives the a/c an extra few minutes of emergency power when required.
Thanks cool guys I missed that fact, the issue then is the charging system does not identify that the battery has been discharged?
Over discharge can be identified with a proper diagnostic charger.

[Cool Guys]

Hi mickjoebill

Over discharge can be identified with a proper diagnostic charger.

I think the over discharge is identified, that is why they replaced the batteries so many times. I think TURIN gave the most likely explanation for this also.


Where things have gone wrong (re: 150 batteries changed in service) is the operators have not really ensured that the people at the sharp end are thoroughly briefed as to the consequences of EG. Leaving the towing switch on.

[cockney steve]

crappy,ill-considered system.
very early on, I was shouted-down , suggesting the battery should isolate before reaching non-rechargeable status. the argument, then, as now, was the need for that extra few minutes'power.

How about , the circuits automatically boot the APU if either battery drains down more than, say , 20% that way, the likelihood of a 2-hour battery-change delay would be virtually eliminated. In case of total in-flight generating-loss, a big red "EMERGENCY FINAL BATTERY RESERVE" switch/button could be activated....then the heroic pilots could wrestle it to the ground , safe in the knowledge that they had brakes and the tin-box would provide a bit of heat in adverse temperatures :}

IMO, these batteries are being used as a ground-supply as an alternative to a GPU or the APU.....It's wrong!- they're supposed to be for flight-critical emergency backup. Therefore, the APU should be the main power-source in any case where the main engine(s) are not running. I only see up-sides to an automatically-starting APU when a load is detected.

|It isn't hard! about 60 YES! 60 years ago, I stayed in a remote place in Devon, No mains services. If a light or appliance was switched-on, the generator automatically fired-up with a few seconds' time-lapse.

Job needs sorting and practical and commercial objectives need to be assessed by someone who understands the business. the present bunch of Nero wannabe's don't appear to fit the bill, having now pi55ed -off the authorities that they're supposed to work WITH....if they can't get even the basics of business right......

[Kiskaloo]

It was a customer requirement that a number of the 787's systems be able to be operated without the engines or APU running or the plane having to be connected to external power.

Why Boeing didn't employ two discharge limits - one for ground operations and one for emergencies in the air - is due to it adding complexity to the fault tree and the necessity to take into account the possibility that the ground discharge limit activates during an emergency, denying the flight crew power and possibly directly leading to an accident.

The as-designed system works when operated as-designed. Ground crew need either better training as to how long they can operate the plane off just the battery and/or better supervision to ensure those limits are not exceeded.

[ITman]

I still have trouble understanding why Boeing had decided the 15 minute maximum tow time, if you watch a BA plane at LHR being towed from the maintenance hanger to their terminal 5 is sure as hell takes a lot longer than 15 minutes..... So how is Mr Boeing going to address this I wonder..? and I am sure at other airports around the world as well.

[whatdoesthisbuttondo]

Is there actually a 15 min tow time limit in towing power mode? If there is a time issue, presumably you could start the APU, Would that work?

Reading through this thread, there does seem to be a lot of opinions and guesses that later somehow become facts because "someone said it" earlier. I know it's just a rumour forum in which anyone can post but unfortunately it's easy for something that sounds clever (which was just a guess) to get taken up by others.

It would be helpful if posters background and relevant experience and qualifications appeared next to their posts on technical issues. :)

[gas path]

Is there actually a 15 min tow time limit in towing power mode?
In short No!
There is a battery test switch primarily aimed at tow crews. Pushing the test s/w gives an indication of battery charge state.
The three lights are: High approx. 60 mins available. Med. approx. 30 mins and Low approx. 15 mins.
As said earlier the operators wanted to be able to tow without the use of the APU or other external power source.

[cockney steve]

As said earlier the operators wanted to be able to tow without the use of the APU or other external power source.

Well, they got that, OK, Whilst completely overlooking the fact that their "system" allowed the aircraft to be reduced to an unairworthy state.

Withy the best wil in the world, you can't expect a tug-driver to understand the ins and outs of a lithium battery's charge-discharge characteristics. they're MOVERS not scientists!...The hundreds of posts on here, by a predominantly intelligent membership, prove that the assumption that unskilled personell could be let loose on a fragile system,was deeply flawed.

In a former life, I made, and later serviced, Medical Equipment, including premature-Baby Incubators, Respirators, oxygen tents and and various pumps.

A major part of the designer's efforts , was to make everything "idiot-proof"

We had a saying....
Make it idiot-proof and it'll be ALMOST Nurse-proof.

No matter how well something is placarded, complacency and familiarity will ignore it. safety and protection need to be built-in to pre-empt misuse.

my suggestion of a "bypass" emergency-reserve switch (on the flight-deck)
addresses that issue....

Why Boeing didn't employ two discharge limits - one for ground operations and one for emergencies in the air - is due to it adding complexity to the fault tree and the necessity to take into account the possibility that the ground discharge limit activates during an emergency, denying the flight crew power and possibly directly leading to an accident.

....And a burning battery or a U/s over-discharged one doesn't add complexity to the Aircrew's day???? -

Come on! this would be a very minor mod , in the big scheme of things.

The plane had too much design-input from smartass Graduates and bean-counters and not enough from experienced aeronautical and systems engineers. and it shows!

[toffeez]

"McNerney acknowledges that dealing with the 787 problems has been a "frustrating experience", but says that FAA regulators who had put the airframer "through the paces" had the country's best interests in mind."

The country's (Boeing's?) best interests. Not safety, then?

[barit1]

Anilv:Commercial airliners are equipped with all kinds of dangerous goods, off the top of my head
-flammable liquids- a B744 can carry almost 170 metric tons of fuel. Try calling Fedex and telling them you want to ship 1 bottle of kerosene!

30 years ago a colleague handcarried a half-litre of Jet-A from a customer back to our home base for analysis. It was in a ruggedized poly bottle, wrapped in heavy polyethylene bag, in his briefcase - it probably would have withstood a 20G crash without leaking a drop.

But the young lady at security, seeing the straw-colored liquid, said "What's this?" - and said colleague professed that he raised horses, and one mare was sick, and he was rushing a urine sample to a veterinarian for a diagnosis. She turned up her nose, slammed the briefcase shut and sent him on his way!

By comparison, what about a two-litre (glass, in that day) bottle of 90-proof vodka from duty-free?

[PAXboy]

cockney steveThe plane had too much design-input from smartass Graduates and bean-counters and not enough from experienced aeronautical and systems engineers. and it shows!There is an old saying, origins unknown:

It takes one generation to start a company,
A second generation to run the company,
A third generation to close the company.

Boeing is not going to close over this but it will not be forgotten. Hopefully, it will be used in business schools and text books.

[syseng68k]

cockney Steve, #1487

crappy,ill-considered system.I tend to agree. I different sort of "enough of the bo***cks", right ?.
You can only take things so far via the use of diplomacy :ugh:

The number of areas that have been identified here as indicative of poor
design are many, but for yet another, consider this: If the battery system
is designed to disconnect when the voltage reaches a low limit, the
contactor in the box must be energised (Normally closed contact). When
the battery reaches a low enough level for the contactor to drop out, the
battery becomes connected again. This would eventually discharge the
battery to zero volts, turning it into scrap.

As for the low voltage limit "reserve", I find it difficult to believe
that such a design would pass any design review. Consumer electronics,
perhaps, but not for aviation...

[Momoe]

Syseng68k, post # 1496

I'm not disagreeing with design issues, however if the only source of power is the battery, then it's a question of how long before the plane gets to the ground, if the battery lasts that long then it's fulfilled it's purpose.

If there is one other source of power, wouldn't the contactor remain powered? The battery system doesn't exist as self-contained system although there are degrees of isolation.

[Old Engineer]

@syseng68k

...If the battery system is designed to disconnect when the voltage reaches a low limit, the contactor in the box must be energised (Normally closed contact). When the battery reaches a low enough level for the contactor to drop out, the battery becomes connected again.

If I may, I think the action you describe above (energized coil drops out on low coil voltage) to indicate the behavior of a "normally closed contact" instead describes the behavior of a "normally open contact". That is to say, the ordering description for the contactor which produces the behavior you envision as cause of trouble would be "NO". The "normal" position is the position of the contacts with the coil not energized. "Normal" for a coil device does not refer to the customary position of the contacts when the circuit is in some particular configuration which is considered the normal position when operating.

So, if the contactor is NC, it is not energized when the battery is connected to the bus. Current to lift the contactor armature is only drawn when it is commanded to break the circuit by opening the normally closed contacts. In this application a mechanical latch would be applied and either this latch or the main armature by way of auxiliary contacts, would provide what's called coil clearing. That is, the latch hold the armature up, and once latched the coil clearing removes the operation current from the coil.

Such a contactor (as I described it) cannot be reset other than manually. [There are latching relays that are electrically locked, but I don't think this one would be.] Speaking of relays, the coil current may be provided by a mechanical relay, as a very substantial current would be required to lift a 400-ampere contactor, even more so if it were a motor contactor compared to a lighting contactor.

So, when this NC contactor lifts, it breaks the circuit, latches open, and disconnects its own coil. There is no resetting this puppy without breaking the seal on the battery box. Possibly its setting permits a special charging protocol at the factory to make it serviceable again, possibly not; in any case with remaining capacity around 15 or 20%, lifting the contactor to open the circuit should be no problem (the action is very fast) for the battery in the simple case of nav lights on too long.

An internal cell fault could be a different story, however. Some of the reported data in the cases involving cell damage suggest the contactor may not have opened immediately, and possibly not at all, in at least one of these cases.

As for a design to permit irreparable battery discharge, I have made designs where considerable heating of equipment was permitted by the controls. This involved a battery of motors, in a situation of very substantial life safety hazard. The idea was to get into shortening the ultimate life of the motors, as a reasonable expense in very unusual circumstances, but to stop short of fire.

There were other changes made to the manner in which the motors operated, the type of motor, the equipment building, and the location of the motors and their controls within it. So if maximum possible energy delivery was part of this 787 design, I can see that point of view even if it cost $16k. But I think it is necessary to stop short of fire-- although where that point is, is not easy to judge, it appears.

This was also true of insulation life in motors, in the example I gave. It followed a real failure of the system, very luckily without injuries, which was not our design-- although it had been a very standard design (and so "protected" the motors in preference to the mission), excepting possibly one or two details. Well, the details were important. IIRC, mission failure resulted in the loss of the motors anyway; ditto expensive controls ($10 million worth, years ago).

[syseng68k]

Momoe, #1497

Correct me if i've got this by the wrong end, but the argument seemed to
be suggesting that the battery would be run outside cell data sheet limits
to get that final reserve, which I find difficult to believe.

Aviation kit is generally designed with parts having generous operating
margins to improve reliability and/or safety. The worst case operating
conditions are analysed and components sized accordingly. If a proposed
battery doesn't meet the load requirements, they just fit a bigger one.
It's that simple.

Other than the ntsb report, there seems to be very little added info at
present and the proposed box solution looks more and more surreal with
each week that goes by. Come clean Boeing, tell the truth and publish
everything. It's the only way to really restore confidence. Otherwise
there will always be doubt and the tech pundits will never let the story
die...

[syseng68k]

Old Engineer, #1498

I think the action you describe above (energized coil drops out on low coil
voltage) to indicate the behavior of a "normally closed contact"
If you look at the schematic in the ntsb report, it's quite clear that the
contactor is drawn with normally closed contacts, which is the contactor state
with the coil / solenoid unenergised. While it may be latching to the open
state, there's no evidence for this and in fact, the contactor looks fairly
standard in that respect, but yes, it could be latching to the contacts open
state.

I originally brought this up in tech log, (#902), which might better explain why
this isn't a very good idea..

[WHBM]

An interesting one for Boeing's lawyers :

United, Boeing Agree to 787 Buyback - FlyerTalk Forums (http://www.flyertalk.com/forum/united-mileageplus-consolidated/1454223-united-boeing-agree-787-buyback.html)

[syseng68k]

Yes, very funny. Let's hope it's not predicting the real future :E...

[areobat]

My car has "always-live" convenience outlets (e.g., the ubiquitous cigarette lighter plugs) which incorporate a protective monitoring circuit that keeps them live, but disconnects them before the battery charge state reaches the point where it will not start the car. It seems to me that if it can be done in a car, the Boeing system could monitor battery state and "disconnect" the towing lights when the battery charge state reaches a low, but not damaging state. Full use (even to the point of damage) would be allowed for in-flight non-routine operations (gen failure, etc.). The SOP would call for battery replacement after such an event.

It's interesting, I read the list of "improvements" to the battery system proposed by Boeing, and many of them were things that I (and others) suggested early on in the thread. It seems to me that if these things are obvious to me, they would be obvious to anyone with even a modicum of engineering experience. Given that, I can only conclude that the battery system at Boeing was designed to the requirements of the bean counters rather than the engineers. And is so often the case, designing to a price, has a price, and Boeing sure seems to be paying it.

[mickjoebill]

Why Boeing didn't employ two discharge limits - one for ground operations and one for emergencies in the air - is due to it adding complexity to the fault tree and the necessity to take into account the possibility that the ground discharge limit activates during an emergency, denying the flight crew power and possibly directly leading to an accident.

Why not have a dedicated battery for ground ops?
A simple big fat mechanical switch between the flight battery and the ground battery would not take much of a redesign?

Captain Macgyver could use the ground battery in the event of an inflight emergency.