FAA Grounds 787s

[vovachan]

I wonder how much weight they saved by going for Lithium

what they got:
75 ah
60 lbs
32 v

what specs would a "conventional" battery of a similar capacity have?

[Pub User]

what specs would a "conventional" battery of a similar capacity have?

A bit of Googling would suggest that a beast of the sealed lead-acid variety could be made but would weigh a little over double.

That sounds like a trivial cost, but I'm not sure any other technology could produce the peak current required of the 787 battery when starting the APU. Any experts care to comment?

[grebllaw123d]

vovachan,

I read somewhere that the weight saving by going for a Lithium-ion battery system instead of a NiCd system on the A350 project is 180 lbs/82kg.

Furthermore, the NiCd system would occupy twice as much space.

I guess that the figures for the B787 are more or less the same.

[TURIN]

A Ni-Cad battery of similar size and weight is capable of starting a heavier APU for the 777.

I was watching a TV program the other day that mentioned Li-Ion batteries and it suggested that Ni-Cads of similar performance would be six times larger/heavier. I took it with a pinch of salt but you never know.

Bearing in mind that Boeing removed the original access door from the forward hold to the forward electrical bay and replaced it with a fixed panel just to save weight gives you an idea of how weight critical they are.

If the Li-Ion Battery is half the equivelant weight or more of a Ni-Cad......:hmm:

[RR_NDB]

Hi,

Pub User and TURIN:

...but I'm not sure any other technology could produce the peak current required of the 787 battery when starting the APU.No problem!

A Ni-Cad battery of similar size and weight is capable of starting a heavier APU for the 777. (http://www.pprune.org/rumours-news/505455-faa-grounds-787s-39.html#post7687589)
For MAIN the issue is a little bit more "complex". The diode module (certainly) would be removed and there will be new algorithms in the retrofit.

Bearing in mind that Boeing removed the original access door from the forward hold to the forward electrical bay and replaced it with a fixed panel just to save weight gives you an idea of how weight critical they are.
Better to compensate airliners (PAX number) than prolonged grounding. :mad:

If the Li-Ion Battery is half the equivelant weight or more of a Ni-CadI will post ASAP a detailed comparison to Ni Cd. I estimate the same figure.

Certainly Boeing is working considering ALTN solution(s). ABSOLUTELY FEASIBLE

[Mk 1]

From Pub User: A bit of Googling would suggest that a beast of the sealed lead-acid variety could be made but would weigh a little over double.

That sounds like a trivial cost, but I'm not sure any other technology could produce the peak current required of the 787 battery when starting the APU. Any experts care to comment?

Wouldn't describe myself an expert, but I do have experience with Lead acid batteries in the renewable energy field. A little over double is fanciful due to the way apparent battery capacity varies with the rate of discharge.

If you are judging the weight based on a 75Ah lead acid battery, then that battery 'capacity' is obtained by finding that the battery can withstand a 3.75A load for a 20 hour period before the battery voltage drops to a point where the battery is considered fully discharged. If you upped the discharge rate to say 7.5 amps the battery would probably not give a 10 hours of discharge as a linear regression would suggest (75ah/ 7.5A = 10 hours), instead it would probably give 9.5 hours for a capacity of 71.25Ah. If you increase the discharge to say 20 amps, instead of the battery lasting the linearly theoretical 3.75 hours it would probably last 3 hours giving a battery capacity of 60Ah. And it gets worse from there - a 150a discharge current would probably give only 15 minutes before being flat - so 37.5Ah. This is known as the Peukert Effect.

Someone on here mentioned peak loads of 700a when starting the APU - to cope with that load you'd probably need a battery in the 400-500ah range - that much lead will end up weighing well over 140kgs (battery alone - not counting interconnects, racking etc. The end effect of having to redesign the racking etc and the additional space required would mean the impact with lead acid would be several hundreds of Kg's more. Lead acid because of this quirk in its chemistry (Peukert Effect) is not well suited to high current short duration/low weight applications.

[RR_NDB]

Hi,

Some initial information:

Advantages and Limitations of NiCd Batteries
http://www.buchmann.ca/shim.gif Advantages
Fast and simple charge — even after prolonged storage.
High number of charge/discharge cycles — if properly maintained, the NiCd provides over 1000 charge/discharge cycles.
Good load performance — the NiCd allows recharging at low temperatures.
Long shelf life – in any state-of-charge.
Simple storage and transportation — most airfreight companies accept the NiCd without special conditions.
Good low temperature performance.
Forgiving if abused — the NiCd is one of the most rugged rechargeable batteries.
Economically priced — the NiCd is the lowest cost battery in terms of cost per cycle.
Available in a wide range of sizes and performance options — most NiCd cells are cylindrical.
Limitations
Relatively low energy density — compared with newer systems.
Memory effect — the NiCd must periodically be exercised to prevent memory.
Environmentally unfriendly — the NiCd contains toxic metals. Some countries are limiting the use of the NiCd battery.
Has relatively high self-discharge — needs recharging after storage.

Advantages and Limitations of Li-ion Batteries
http://www.buchmann.ca/shim.gif Advantages
High energy density — potential for yet higher capacities.
Relatively low self-discharge — self-discharge is less than half that of NiCd and NiMH.
Low Maintenance — no periodic discharge is needed; no memory.
Limitations
Requires protection circuit — protection circuit limits voltage and current. Battery is safe if not provoked.
Subject to aging, even if not in use — storing the battery in a cool place and at 40 percent state-of-charge reduces the aging effect.
Moderate discharge current.
Subject to transportation regulations — shipment of larger quantities of Li-ion batteries may be subject to regulatory control. This restriction does not apply to personal carry-on batteries.
Expensive to manufacture — about 40 percent higher in cost than NiCd. Better manufacturing techniques and replacement of rare metals with lower cost alternatives will likely reduce the price.
Not fully mature — changes in metal and chemical combinations affect battery test results, especially with some quick test methods.

The following table is for small batteries.

http://i49.tinypic.com/20asxur.jpg

Source (http://www.buchmann.ca/article4-page1.asp):

About the Author
Isidor Buchmann is the founder and CEO of Cadex Electronics Inc., in Richmond (Vancouver) British Columbia, Canada.

[EEngr]

lomapaseo (http://www.pprune.org/members/48942-lomapaseo)

Typically Technical Fellows report to a Sr Vp level. So I imagine that once they assess their short commings in all this they can effect some changes immediately in the process gaps. Nothing would stop them from auditing anything that they feel contributed including vendor performance. (financial contracts not included)"financial contracts not included"

Really? Do you think that its possible to divorce economics from engineering? I don't. There has to be someone that can report to that VP, "Yes, the technology is mature. But No, Boeing isn't prepared to make the necessary investment into the skill sets needed to exploit it. So in the final analysis, the answer is 'No'".

Someone else pointed out that Boeing moved their HQ to Chicago to keep the engineers out of the boardroom. They appear to be reaping the rewards (or consequences) of that decision.

[HeadingSouth]

EEngr et al.

Many thanks for post 715 and following discussing the effect of AC on "DC oriented" power plants. I fully agree with what has been written, having seen these effects as well on large-ish power plants requiring paralleled cells. Having had a slightly different internal resistance was enough to have them sent across Jordan.
This applies more and more to low ESR battery packs - the more current they can deliver, the more dramatic are the (very small) differences within the internal resistances of the batteries.
We've always considered the AC behaviour of our DC installations and I would be very surprised if the engineers at the LiIon battery developer hadn't considered this.

Anyway, thanks for the update, and I'll keep on reading...

[fdr]

not to be too simplistic, but as the calendar pages go by, there will come a point in time when going down to the local apple store and buying a bucket full of iphones and plugging them into the system will be cheaper than the cost of grounding a multi billion dollar program over the concern of a battery mass. The NiCd battery has been running for a fair old time, the guys in the hanger will be pretty familiar with them, and there are enough ex douglas guys there to string some more cabling as they were fond of doing.

Right now, the simple solution is a least risk solution.

[cwatters]

Someone on here mentioned peak loads of 700a when starting the APU

If the battery has a 75AH capacity (reported elsewhere) then the peak draw works out at about 9C (eg 700/75 = 9.3C).

I'm not sure this is the right data sheet (also reported elsewhere) because it's for a 65AH capacity but..

http://www.s399157097.onlinehome.us/SpecSheets/LVP10-65.pdf

It mentions a max discharge rate of 5C for the family. Obviously it's possible to trade off discharge rate vs time but 5C doesn't seem very high. I've seen other LI cells rated at 30C for model aircraft use.

The internal resistance for the 65AH cell is 0.3mohms. At 700A each cell would be dissipating 700 x 700 * 0.3 x10^-3 = 147W. There are 8 in the box so the battery might be dissipating >1kW for however long the APU is drawing 700A. Presumably it doesn't draw that much for long?

Is the battery ever used to start the APU in normal use or just emergency?

[Speed of Sound]

Presumably it doesn't draw that much for long?

Peak current draw will only be for a fraction of the minute or so of the start up, especially with soft starts designed to reduce high torque induced damage of starter shafts.

[green granite]

cwatters, the 75Ah figure is the nominal capacity, ie. right down to total discharge, 65Ah is the usable capacity ie. down to immediately before the 'knee' part of the curve.

[HeadingSouth]

For unmatched, paralleled Li-Ion cells, 5C is already considerable. Or at least it was, not too long ago...
And references to model airplane batteries are a bit difficult as these are LiPo batteries and quite often end in smoke and tears, be it by faulty charging or mechanical damage. So let's keep them to the model world.

[tucumseh]

MoD (UK) has bags of experience with Lithium batteries exhibiting what they euphemistically call “flaming events”. In 2006 there was a total recall and destruction order on Li-Ion secondary batteries (rechargeables) supplied for the BOWMAN HF radio. It took well over two years to replace them, a period in which users had to largely do without; despite being a Critical Enabling Technology.

There were numerous problems, all known in advance and ignored; partly because batteries are seen as faffy and a largely ignored commodity. In short;


1. The battery case was meant to be welded to prevent moisture ingress. It was crimped to save money.


2. The internal sensing electronics were meant to be potted, as a back up to protect from moisture ingress but also to provide robustness. The potting was entirely missing, again to save money.


Additionally, the BOWMAN specification required the “system” (battery, chargers, human) to permit 500 charges before replacement. I include human, because obviously the user has to receive information as to state of charge and be properly trained.



3. A typical battery could be recharged 3-5 times, meaning stocks had to be replenished (typically) 100 times more frequently than anticipated, requiring money for which no provision had been made.
4. It could not be recovered from even moderately deep discharge.
5. The state of charge indicator was not visible to the user in normal use.



Despite users having no control, over 3, 4 and 5, it became an offence in the Army to “permit” a battery to go into deep discharge.
1&2 are clearly Quality Control and Quality Assurance failures on the part of the contractor and MoD respectively (as well as fraud). I won’t say manufacturer, because the selected company didn’t actually make the battery, they bought in and assembled the parts. This is a recipe for disaster when they are also responsible for the chargers; and, indeed, 3, 4 & 5 are primarily a systems integration failure. What realistic chance is there of an assembler having a deep understanding of the system integration requirements? The AC and DC chargers, I think around 12,000 of them, were bought-in and were incompatible with the batteries.



I point this out because, from what I read here (and many of the observations are excellent), there would seem to be some similarities. Much is said of the battery manufacturer, but that is always too simplistic. The first thing I’d look at is the Interface Definition Documents detailing the boundaries of responsibility. One of MoD’s failures was not to have IDDs, which is like handing out blank cheques. In part, this explained why they simply handed the replacement contract to the same company, without competition, paying them twice for the same thing. Despite proper manufacturers selling the same battery (and compatible chargers), manufactured and operating to specification, for half the price. If there is a lesson to be learnt here by Boeing and their suppliers, it is this. Don’t ask MoD for advice! Rather, seek out the company who advised MoD of these forthcoming problems in the first place.

[Lyman]

Ground Politics

The chief of NTSB continues to repeat two basic themes, and Boeing responds in public with a type of response intended to resist these themes.

Theme #1 BOEING have experienced two very serious failures in the Battery system as certificated.

Theme #2 Lithium Ion Battery technology is under scrutiny as a whole, the format is in doubt, regardless of chemistry type.

BOEING answers by assertively requesting "test flights" and "repositioning".
They have got to keep at least a few aircraft operating, the chance that the public will see the fleet as collecting cobwebs on the ramp would be damaging.

BOEING answers by suggesting possible "fixes". Improvement to the case, as you propose, and similar, plus a scheme to keep each of the eight batteries isolated from each other, to prevent "propagation" of failure/fire in one cell.

The purpose of these proposed fixes is to plant their own theme, that the technology is "mature", and the failures are mitigable, in spite of the fact that their best efforts "Failed". (See Theme #2)

Technically, I think you have the solution at the ready. Some form of enclosure that will not conduct electricity, will contain explosive forces, flame, and electrolytic material.

These Press conferences are scripted, but that is to be expected. The playing out of the process at the public level is most instructive.

Hersman, to her credit, has outlined the interplay at each meeting. She is a consummate player, diplomatic, assertive, calm, and professional.

BOEING seem to have found their footing. Their initial response will eventually fade, but those who scrutinize the process will remember how they tipped their hand, and loudly (inadvertently) outlined the flawed relationships that exist in the industry.

FAA....speechless. Feckless, powerless, kept.

[Ranger One]

fdr: not to be too simplistic, but as the calendar pages go by, there will come a point in time when going down to the local apple store and buying a bucket full of iphones and plugging them into the system will be cheaper than the cost of grounding a multi billion dollar program over the concern of a battery mass. The NiCd battery has been running for a fair old time, the guys in the hanger will be pretty familiar with them, and there are enough ex douglas guys there to string some more cabling as they were fond of doing.

Right now, the simple solution is a least risk solution.

As I posted a week or two ago, there's nothing 'simple' about the 'solution' of changing to a different battery technology - and weight is the least of your issues.

First, the charging and monitoring systems and software would have to be redesigned and recertified.

Second, where would you PUT the damn things? Any alternative battery technology will not have the same energy density as lithium. Not only will batteries of equivalent capacity be heavier, they'll be bulkier. Much bulkier. They won't fit in the space available, the space Boeing carved out for lithium batteries. Mk 1 posted on this a few posts back.

They would have to reengineer the structure of the EE bay - or even carve a separate battery compartment out of the hold spaces. Now you have structural engineering changes to design, test, certify, put into the production process, and retrofit to the units already delivered. And do this while synchronized swimming with all those subcontractors you've parceled the project out to...

Now do you see why I said this airplane isn't going anywhere soon?

(the alternative - finding the root of the problem and proving lithium safe enough to use, all over again, could be even harder...)

[no-hoper]

Dimensions of a 50Ah NcCd aircraft battery,which easily will start the APU:
11,7in x11,8in x10,6in.Weight 94 lbs.

Original B787 battery:
19x13.2x10.2 inches and it weighs approximately 63 pounds

[Lyman]

16" L, 10" W, 12" H. 80 AH. 105 lbs. Lead Acid?

[tango.golf.romeo]

Ultimately they'll have it fixed (possibly replaced), make FAA to re-certify, and resume selling again, I think. There's just no other way. The stakes are extremely high.

[RR_NDB]

Hi,

Ranger One:

First, the charging and monitoring systems and software would have to be redesigned and recertified. (http://www.pprune.org/rumours-news/505455-faa-grounds-787s-39.html#post7690319)

For the Main battery the task is much more complex than for the APU batt.

Second, where would you PUT the damn things? Any alternative battery technology will not have the same energy density as lithium. Not only will batteries of equivalent capacity be heavier, they'll be bulkier. Much bulkier. They won't fit in the space available, the space Boeing carved out for lithium batteries. Mk 1 posted on this a few posts back.


Suppose 2 Ni cd´s in two adjacent positions. Could solve the problem you mention.

Much bulkier.

How much? Let´s quantify?

They would have to reengineer the structure of the EE bay - or even carve a separate battery compartment out of the hold spaces. Now you have structural engineering changes to design, test, certify, put into the production process, and retrofit to the units already delivered. And do this while synchronized swimming with all those subcontractors you've parceled the project out to...


Even optimizing (if possible like i am suggesting) would take months.

Now do you see why I said this airplane isn't going anywhere soon?

Problem is not just a BAD battery. There are MANY PROBLEMS. They yet know. We in pprune (with scarce information) detected SEVERAL.

(the alternative - finding the root of the problem and proving lithium safe enough to use, all over again, could be even harder...)

I agree. And the consistency of this point certainly was taken into account by Chicago Boeing guys (most engineers are not there) in the Decision Making.

Boeing (airplanes) is now absolutely optmizing $. The dream is over. $ is the (only) name of the game. Insurance cover grounding. Further comments can be left to other posts...

They are facing other important problems. (http://community.seattletimes.nwsource.com/reader_feedback/public/display.php?thread=816115&direction=DESC&column=rating&offset=0#post_4639888) :{

[Lyman]

It isn't that bad.... The elements of compliance with the Lithium Ion regs are all there.

BOEING (Thales, Yuasa, Securaplane) cut it too close. That is why BOEING pitched such a fit when FAA (AFTER JTSB) GROUNDED the 787.

Had they expanded by as little as 10 per cent their mitigations, well......

FAA and BOEING both knew a thermal runaway would happen; the problem is they were over confident in their design to mitigate a multiple (propagation).

That has been apparent from the outset, and all the way back.....

Now they have to do what they could have done before, and avoided all this nonsense.

Bigger case, more cell separation, stand off (raised) base, stricter assembly standards, etc......

Fix it. I cannot wait to fly in one.

:ok:

[Volume]

FAA and BOEING both knew a thermal runaway would happen
The standard set by the FAA for this safety critical event is one occurrence in one Billion flight hours. IOW not even once in the life of the fleet.
Boeing negotiated a lower threshold, one in ten million flgiht hours. A reduction in standard of 100:1.
There have been two occurrences in less than one hundred thousand Flight Hours. A further reduction in threshold of 100:1.

A very interesting read along those lines dealing with system safety asessments and how they failed is this great NASA report :
Why System Safety Professionals Should Read Accident Reports (http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20060020178_2006096003.pdf)
The potential consequences are often recognized, but their likelihood is thought to be quite a bit lower than it turns out to be.

And by the way, the "standard set by the FAA" of once in one billion flight hours is for catastrophic events, the one for hazardous events is once in ten million hours. So far the events have just been hazardous. Yes, an emergency landing did happen, and some passengers were injured. But there was neither the loss of an airframe nor did any fatalities happen, so formally once in ten million hours is the "correct" number to use. If only that number would have been met...

So maybe here as well the aircraft was desgned in a way that the effects of a thermal runaway were correctly recognized, but the likelihood was underestimated.

[RR_NDB]

Hi,

Volume,

A very interesting read along those lines dealing with system safety asessments and how they failed is this great NASA report (http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20060020178_2006096003.pdf) :

:ok: Thanks

The low MTTR (in previous batt.) IMO should be used proactively by Boeing or Thales long before both battery fires.

Some years ago i´ve heard Boeing maintained in major airports a mechanic just to provide feedback to the 747 program.

Considering the innovations introduced on 787 i hope the data logging in the Systems are better than the HIGHLY PROBABLE loss of cell voltages history in both incidents.

[Lyman]

Hi RR

You are proceeding along a path dictated by your preconception of the cause.

There are two causes here, as I see it. One is PROCURING, the other is PROXIMAL.

Your focus is on the proximal, aggravating cause. The smoking gun. The Electrical system.

There is a procuring cause, the Lithium Ion Battery. Procuring means 'Created'.

Proximal means 'aggravated to disclosure'. I am not sure the 'system' played any part at all. By the time the fire was uncontrolled, the system likely could not have had any effect on controlling it. Certainly not in preventing it.

RUNAWAY. OUT OF CONTROL, CANNOT BE CONTAINED, Land immediately, call the fire department.

That one cell could experience thermal runaway was a given, and the standard beyond which no further runaway would be tolerated.

That is what happened. NTSB told us that. "The fire started in one cell, #6".

That should have been the end of it. One cell self destructs, smoke vents, case contains the incident.

No monitoring can arrest a thermal runaway. Monitoring was intended to prevent Propagation. Boeing prepared for that, per the regulations.

It didn't work as designed. Because the design was insufficient?

NO. It did not work because something happened that exceeded the design's limits.

Boeing did everything just right. Just not enough of it.

Boeing knew what happened before the Fire Department arrived. And they have been working on re-certifying the new system since that day. Probably way before that.

I will be perfectly happy if Boeing provides a system that prevents PROPAGATION. Runaway int the problem.

imho

[RR_NDB]

You are proceeding along a path dictated by your preconception of the cause.

Despite to have some models that could explain BOS and TAK i am completely open minded as any search of the truth should be and MUST be.

Obviously we don´t have all necessary information and so we need to be careful and REDUNDANT when expressing what is our models, what is our mind.

NO. It did not work because something happened that exceeded the design's limits.

Not necessarily. E.g. the algorithms certainly respected design limits but could stressed the cells beyond safe levels. Only time can test certain design characteristics. (E.g. Comet, Electra, etc.)

Boeing did everything just right. Just not enough of it.

Just (another :}) hyperbole or you indeed think this?

Boeing knew what happened before the Fire Department arrived.

Certainly some Boeing engineers, some posting in many forums (http://www.google.com/url?q=http%3A%2F%2Fcommunity.seattletimes.nwsource.com%2Frea der_feedback%2Fpublic%2Fdisplay.php%3Fthread%3D816115%26dire ction%3DDESC%26column%3Drating%26offset%3D0%23post_4639888&sa=D&sntz=1&usg=AFQjCNFb8AC1SNcbRvo9IM-up9CqqlHEMA) probably expected.

I will be perfectly happy if Boeing provides a system that prevents PROPAGATION. Runaway int the problem.

I am convinced NTSB will do an exemplar job when showing FAA their results. Propagation, runaway are important but they are looking to WHY the cell shorted. Runaway and propagation were consequences. In TAK a probable cell short resulted (posted earlier) in a devastating (external to the battery) short circuit. A battery failure DESTROYED an aircraft conductor during the flight. Fortunately transformed in a (non designed :} ) fuse. Thus saving Boeing from a much more serious case:



An inflight fire, outside of battery inside the FWD EE bay.

(The smoke in the vent was just a sample. TAK ATC could see the smoke:

http://i48.tinypic.com/55nrbn.png



And i suspect FAA design review is the BIG ISSUE. :{

[RR_NDB]

Hi,

Reposting:

http://i45.tinypic.com/2nlqq79.png

ANA TAK short circuit of cell # 3 plus terminal to battery case.

[FlightPathOBN]

ICAO moves to remove exemption to carry Li batteries on aircraft.

"A U.N. agency that sets global aviation safety standards is moving to prevent aircraft batteries like the one that caught fire on a Boeing 787 last month from being shipped as cargo on passenger planes, people familiar with the effort said.

Over the past few days, the members of the International Civil Aviation Organization's dangerous goods committee have proposed revoking an exemption that permitted lithium ion aircraft batteries as heavy as 77 pounds to be shipped on passenger planes, the sources told The Associated Press. All other lithium ion battery shipments on passenger planes are limited to 11 pounds or less because of the batteries' susceptibility to short-circuit and ignite."

UN agency moves to kill aircraft battery exemption | Boeing news | The Seattle Times (http://seattletimes.com/html/politics/2020340381_apusboeing787batteryshipments.html)

[Lyman]

That didn't take long.

It's only been allowed for four weeks.... Does any body know what they're doing? Since it was the Department of Transportation that signed off on shipping the Batteries on pax flights, and that did not turn out, is that why the Department's chief, Ray LaHood, Resigned? Was he under pressure to allow the replacements to fly? How had Boeing been shipping the "replacements" before they were blessed by DOT? :ugh:

:E

[RetiredBA/BY]

Heading South:

Based on my experience I wouldn't be too quick to dismiss the relevance of lithium batteries as used in model aircraft . True, most batteries used for this application are lithium polymer and there have been a lot of flame events caused primarily by using the wrong or mis-set charger, the non use of a balancer (essential) as well as physical damage. I use these batteries for their high energy density, high discharge currents and quick charging ability and always remove the batts. from the airframe for charging due to the fire risk. For me so far so good, firewise, although failure rates (voltage collapse, and cell swelling) ) have been high !

However, I have also been using lithium Ion batteries for some years both for airframe electronics (numerous powerful digital servos) and engine power (ECU, Starter and ignition on gas turbine powered models). Although the packs I use have an internal balancer and dedicated, slowish, charger (about .2c) I have noticed a very high failure rate for LiIons compared with NiCd and NiMh chemistry even though the discharge currents on my applications are not excessive. The failures have been non "flaming" but many packs have lost voltage and the ability to accept a charge at way below the cycles one might reasonably expect (some have failed after less than 50 cycles).

With the fire/explosion risk of LiPos, the poor reliabiltity of LiIons a lot of us are moving over to LiFe batteries which appear safer chemistry even though they can't quite deliver the performance of other lithium chemistry but do show an ability to recharge VERY quickly and can deliver quite high currents without much voltage drop off. Never heard of a fire or explosion with LiFe cells, perhaps this may be the way to go.

Still putting my money on a single cell failure and the charger trying to bring the pack upto full voltage, but isn't that what a balancer circuit is supposed to do ?

So, don't totally dismiss our lithium experience !!

(and no, not an aeromodelling troll, ex 75/76 captain who once flew an earlier, nearly, all-electric aeroplane, the Valiant ! Not a lot of people know the Valiant was almost fully electric, inc engine duct anti-icing, except for hydraulic wheelbrakes and N/S, lipos in this days, never been heard of !!)

Anyway I wish Boeing every success in getting to the bottom of this, and rapidly too, the 787 should soon be helping pay my pension !

[RR_NDB]

Hi,

RetiredBA/BY:

Still putting my money on a single cell failure and the charger trying to bring the pack upto full voltage, but isn't that what a balancer circuit is supposed to do ?

Considering i am South of UK :) and you directed your comment to Heading South i will risk to comment something just before i leave:

A balancer is supposed to to this. You are ABSOLUTELY right. unfortunately the circuit being used IS NOT THE BEST for aviation use.

You gave a powerful argument to use another MUCH SAFER approach. Parallel charging of EACH CELL. The "solution" to avoid the condition that may explain very well both cases, i think you touched in your comment.

Synergy between your Valiant (electric) and the dangerous batteries you use today that i prohibited to enter our home in my kids RC models. :}

[cockpitvisit]

No monitoring can arrest a thermal runaway. Monitoring was intended to prevent Propagation. Boeing prepared for that, per the regulations.

It didn't work as designed. Because the design was insufficient?

NO. It did not work because something happened that exceeded the design's limits.

Did Boeing ever test the propagation in a battery installed in an actual airplane? As in, remove all safeguards from one cell, short circuit that cell so that it explodes/burns, then see what happens?

A cell only contains a very fixed amount of chemical energy in it, so it's difficult to imagine that "something happened" and emitted way more energy than expected.

[Lyman]

cockpitvisit

Did Boeing ever test the propagation in a battery installed in an actual airplane?

I'm not sure that is available. Working backward, FAA accepted a single cell would not cause propagation (further runaway). So the assumption is BOEING designed, built, and tested a platform that demonstrated this to the satisfaction of BOEING. And to FAA.

A cell only contains a very fixed amount of chemical energy in it, so it's difficult to imagine that "something happened" and emitted way more energy than expected.

But that is exactly what happened. "Propagation". Clearly, the fire, flares and heat spread to additional cells?

Volume

So maybe here as well the aircraft was desgned in a way that the effects of a thermal runaway were correctly recognized, but the likelihood was underestimated.

So, NTSB have narrowed it down. 1) Battery Design? should the batteries be Prismatic? Cylindrical? Should the batteries be in nonflammable liquid coolant? Active refrigeration or passive heat sink? Should the Enclosure be enlarged, mounted on a stand off platform? 2) Battery construction? High enough standards in layering the Cathode, Anode, Separator stack? Is the environment filtered? Are methods demanding enough as to paste application, folding, wiring, etc.? 3) Monitoring and Management.....

If the controls system caused, (allowed) the thermal runaway, then there is a huge problem. If the battery self ignited, there is a huge problem. If the two cannot be isolated one from the other, (via investigation), the problem is (may be) impossible.

But the third, and most important leg of this three legged stool is the FAA.

Believe it or not, if BOEING can still prove propagation is not possible, the System and Battery don't need to work any better than they did. All Boeing has to prove is one cell will not propagate into multi cell runaway.

The likelihood was recognized and assessed. What was unexpected was the misplaced confidence in the effects of thermal runaway being mitigable. (No Propagation to other cells).

It is this failure in design that is the problem.

If propagation to other cells had not occurred, there would have been no grounding, imo. There would have been smoke, perhaps leakage of electrolyte, and some singeing of the close in structures. But that is allowable, under the regs. (imo).

So it is the regs that offend, because they created the potential for this bizarre argument.

Allowing that single cell Thermal Runaway was acceptable at all turns out to be preposterous.

Which brings up the final turkey. #6 is not a cell, it is a BATTERY. One of eight.
The APU/MAIN BATTERY is (each of them) a group of eight batteries in a stainless steel case.

But FAA says it is allowable to call a BATTERY a CELL.

A ROSE..... by any other name? A lot of what will happen with the Regulations may hinge on nomenclature.....imo.

[HeadingSouth]

RetiredBA/BY, RR_NDB et al.

Albeit it might have come across as such I am not dismissing input from modeller airplane electrics - but there is one significant difference: I haven't seen many _paralleled_ LiPo's in RC aircraft. As I pilot RC aircraft as well I have the standard 1S, 2S, 3S and so on cells, but there are always n cells of 3.7V (nominal) _in series_. This is what the balancing circuit on the charger keeps an eye on - that the charge voltage stays equal at all cells.

The issue I seem to thnk about is more the paralleling of cells; as I mentioned before I consider unmatched cells (matching in terms of internal resistance, in 2nd approximation as well internal capacitance and inductance) not very suitable for high-demanding power applications. Whilst at relatively low current settings there are no issues, there certainly are some at high currents or changing loads (AC behaviour of a DC power cell). For as long as cells are just paralleled I agree with previous statements that the paralleling will provide rather stable DC characteristics. But then at AC conditions this looks certainly different.

Not to speak of the soldering quality of the connecting wires which in the past has not always convinced me of quality either. A minor non-perfect solder joint with some dirt in the solder tin can lead to funny effects, especially after some thermal cycling of the cell.

I fully agree with what has been said before, about the charging circuit not being ideal, about the AC conditions of a DC power source, about mechanical design issues when folding/winding up the cells, etc.
In the end, all these factors (and many others) are contributory to the risk and I wish these issues get solved.

[pax2908]

It would not be the first time compliance is "demonstrated" based only on calculations, not actual tests or direct measurements.

[cwatters]

At least with most RC model packs you can see if the cells have swelled up and not try to recharge them. Would be very interesting to know if any of the 787 cells replaced in service show any swelling.

[RR_NDB]

Hi,

RetiredBA/BY and HeadingSouth:

Still putting my money on a single cell failure and the charger trying to bring the pack upto full voltage, but isn't that what a balancer circuit is supposed to do ? (http://www.pprune.org/rumours-news/505455-faa-grounds-787s-40.html#post7691441)

Most batteries are "series charged" i.e. the charger current flows through all cells from a DC source applying current to it´s plus terminal. (opposite as the current the battery delivers when supplying current to a load. E.g. the 787 APU starter system).

Lithium batteries are not charged directly from a bus. The designers prefer to charge them separately. In 787 the MAIN battery are kept charged separated from the bus by a diode: A "high speed switch" that is controlled by the bus voltage. When the bus drops below (estimated) 30 V the battery (if it is ON) supply current to the bus to maintain it´s voltage at required values. A low voltage in the DC bus would make the loads (electronics) fail.

Well, how Li ion (MAIN and APU) is being charged in 787? From the info we have, serially. I.e. the battery chargers are connected to it´s extreme (minus and plus terminals) and the cells are being monitored to avoid the DANGER of exceeding it´s voltage during the charging. Why? Simply if the current is the same in all cells (series connected) and the cells are different between each other (mismatches due several factors) the voltage in each one could be different, charging it (each cell) not equally. This is normally not a big problem in Lead Acid or even Ni Cd. In Lithium ion this is dangerous.

So the 787 designers (certainly) adopted the cell balancing scheme. This explain the harness over the cells. The several thin wires we imagine were used for individual cell voltage monitoring and to "bypass currents" if and when a given cell starts to present a growing voltage.

This approach requires software algorithms and is used for most of chargers probably also because is cost effective. But there are other ways to charge SAFELY the cells:

Imagine you have one (smaller) independent charger for each cell. This (1/8) little charger could easily (without software algorithms) charge each cell to it´s safe limit AND SIMULTANEOUSLY verify if the cell is “healthy”. A “sick” cell can be e.g. one that despite you pass through it the maximum current (no bypass at all) it´s voltage doesn´t shows the “normal envelope” (by different internal characteristics due ANY kind of fault)

Question:

The charger that were used in 787 fleet until it´s grounding is able to verify this cell condition? And proceed accordingly in order to avoid a thermal runaway?

IMO the best approach would be using a parallel charging scheme. Since ANA incident i am designing a solution (not only the charger) in order to eliminate (or reduce) most of the danger in using these wonderful cells.

The charger is part series charger (high current) and parallel charger (low current) and is being currently used (and tested). The software algorithms being used mainly to check if cells are healthy. Continuous cell characterization. (IMO an essential safety function). And to compare, track and record their electrical characteristics throughout useful life.

PS

Two CPT flying RC (carrying potential fire bombs) has a privileged view of the issues. :ok:

[Mac the Knife]

A few tupenny-ha'penny strain gauges could show swelling for any cell

An Arduino would be enough to monitor 'em!


:(

[RR_NDB]

Hi,

HeadingSouth


The issue I seem to thnk about is more the paralleling of cells; as I mentioned before I consider unmatched cells (matching in terms of internal resistance, in 2nd approximation as well internal capacitance and inductance) not very suitable for high-demanding power applications. Whilst at relatively low current settings there are no issues, there certainly are some at high currents or changing loads (AC behaviour of a DC power cell). For as long as cells are just paralleled I agree with previous statements that the paralleling will provide rather stable DC characteristics. But then at AC conditions this looks certainly different.

The big cells (LVP 65) cells were yet fully characterized WRT to transients, superimposed high frequency ripple, etc. ? Boeing selected this battery due his high performance. Highly optimized. Time tells...

[RR_NDB]

It would not be the first time compliance is "demonstrated" based only on calculations, not actual tests or direct measurements.
(http://www.pprune.org/rumours-news/505455-faa-grounds-787s-40.html#post7692183)


:}

Boeing was lucky in both cases. In TAK the plane was going to have an inflight fire. Underneath cockpit, inside FWD EE bay. :E

Fortunately (probably) the short circuit to ground discharged and "opened" the battery circuit. (http://www.pprune.org/rumours-news/505455-faa-grounds-787s-40.html#post7691355)

[Lyman]

RR NDB

Boeing was lucky in both cases. In TAK the plane was going to have an inflight fire. Underneath cockpit, inside FWD EE bay

I don't follow. Some of what happened to JAL will bear on that statement. A complete report by the firefighting agency would be a good read.

I thorough reading of Lithium Ion regulations seems to permit some pretty nasty stuff, but I venture fire is not included.

The flight crew had only a BATT WARN, and the "smell" to go on. Is there a FIRE EE BAY alert we do not know about?

They had to descend from 31000 feet, which took some time. When was this predicted fire supposed to have started?

So it appears there may be a squishy area not addressed by regs? Of all the nasty stuff that is allowed, the assumption has to be that the airplane is capable of 180 (330) minutes of continued flight?

All these incidents have occurred aloft, save JAL. JAL problem may have begun while airborne?

What seems to be lucky, is the proximity of runways and/or Fire departments to allow emergency procedures.

[RetiredBA/BY]

RR_NDB

Thank you for taking the time to give your explanation, great stuff.

So far as I know model LiPos and LiIons are both charged serially, but the balancer takes a reading from each cell to ensure that cell voltage does not exceed the max value of 4.2. Individual cell voltage can be checked on the charger LED display and in a healthy pack the voltages stay VERY close together, suggesting that the balancer is working well.

Interestingly the LiFe charger that I have actually charges through the balance cable so I presume this is using parallel charging in the form you suggest. Battery reliability of my LiFes has been excellent even though it takes quite a load on engine start, certainly better than LiPos.

Of course we don't charge packs in flight in a model but obviously the 787 does, so is there any way the crew could be advised of a developing internal battery problem such as a defective cell, say through the EICAS, and could a defective cell be automatically isolated from the rest of the battery ?

I certainly like the positive (no pun intended) attributes of lithium for model use and with careful charging, and with a professional radio system which samples and records (both on downlink and internally on an SD card) battery voltage and currents every .1 second, they certainly show good performance, albeit with higher failure rate than NiCds or NiMhs.

I think parallel batteries have been mentioned earlier In some receivers I connect two LiIons to the receiver, (To create redundancy and a very secure power supply to a critical system, although I have never had a LiIon or LiPo failure in flight) one at each end of the receiver bus. One battery always seem to discharge considerably more than the other even though connected to the same bus without isolation.

Other receivers have a main and standby (with automatic switchover at a predefined voltage) for the redundancy but are never paralleled so the standby battery always stays fully charged.

Finally, someone queried whether the main battery could/should be used to start the APU on the 787. Isn't that one of its main functions ? I seem to remember frequently staring the APU on the ground on the 75 and 76 and in the event of double flameout and loss of both gens. in flight starting the APU from the battery would be a very high priority ! One might think that a main battery or separate APU batt should be able to do two or three APU starts with ease.

Anyway, I digress, back to the 787 !

P. S. I may have missed it but no one seems to have mentioned the electrical fire and emergency landing on a 787 during test work. Anyone know the cause of that fire?

[Pub User]

someone queried whether the main battery could/should be used to start the APU on the 787. Isn't that one of its main functions ?

On this machine, I believe this is not the case. The main battery looks after the mainframe computers (Common Core System), while the APU battery is used to start the APU. My (vague) recollection of the 757 system is that the batteries are paralleled for standby-power functions, but I can't recall what they do when starting the APU on the gound.

[RR_NDB]

Hi,

RetiredBA/BY: Ref:18:13

...so is there any way the crew could be advised of a developing internal battery problem such as a defective cell, say through the EICAS, and could a defective cell be automatically isolated from the rest of the battery ?


1) Unfortunately these cells has not "graceful degradation" nor "fault tolerance" a good characteristic of Lead acid and to some extent, Ni Cd. So a message is just to inform the crew battery is INOP. I imagined along this days in a solution using a MAIN battery and a AUX battery. Will comment on advantages later. The AUX could be one to preserve the MAIN.

2) The problem to isolate a defective cell is: You need a costly relay and you reduce the voltage of the battery. It´s not practical.

...someone queried whether the main battery could/should be used to start the APU on the 787. Isn't that one of its main functions ?


Weight (cost and other) considerations led designers to have two independent. Certainly a good approach. But posing inherent operational limitations in a degraded scenario.

I seem to remember frequently staring the APU on the ground on the 75 and 76 and in the event of double flameout and loss of both gens. in flight starting the APU from the battery would be a very high priority ! One might think that a main battery or separate APU batt should be able to do two or three APU starts with ease.

787 designers relied on this battery to provide adequate safety. Problem is the "ideal" battery failed. The a/c design was adequate. (IMO good)

P. S. I may have missed it but no one seems to have mentioned the electrical fire and emergency landing on a 787 during test work. Anyone know the cause of that fire?

The official cause was not a battery related issue. I´ve heard of a distribution panel destroyed by a tool left by a mechanic. :confused: The event was serious.

Will comment later on RC issue.

[FlightPathOBN]

While there was the issue with the tool left behind, the general problem with the panels was the close prox that allowed arcing across parallel panels. That was a major redesign early on.

In regards to the batteries, in the fwd EE bay, it appears this is run like a UPS, where the power is constantly being drawn through the battery system, to provide a clean source for the avionics, else there would not have been an issue in-flight.

IF that is the case, the batteries are in constant use.

[RR_NDB]

Hi,

Bear,

They had to descend from 31000 feet, which took some time. When was this predicted fire supposed to have started?
(http://www.pprune.org/rumours-news/505455-faa-grounds-787s-40.html#post7693080)


The event is recorded in FDR. Voltage fluctuated and went to zero. At this moment cells were no longer capable to deliver energy to battery terminals (inter cell connection was open between cell # 3 and # 4).

The danger of fire (outside battery case) IMO reduced after this moment. (Or a little later.) Battery was yet partially discharged, short to ground no longer existed and temperature of battery probably had an inflexion point minutes after inter cell opening.

This is a "model". Can be confirmed later or not. :8 IMO it´s probable.

All these incidents have occurred aloft, save JAL. JAL problem may have begun while airborne?

I f you look to the time JAL 787 approaching Logan, taxiing, etc. it´s more probable thermal runaway started few minutes before firstly detected. The short circuit (NTSB put as triggering the thermal runaway) would be "visible" if battery voltage is measured before relay/contactor and recorded. I don´t know if it was.

What seems to be lucky, is the proximity of runways and/or Fire departments to allow emergency procedures.

Indeed. But i insist: ANA case was going to be much worse. The short to ground "saved" from a much more serious situation. Similar to BOS thermal runaway consequences. An inside FWD EE bay.

The basis for my post is:

There are many points in common between both cases:

• Same battery
• Not delivering current
• Being charged or being trickle charged
• Thermal runaway

The differences were:

ANA case:

• A short circuit to ground (from cell # 3 region)
• Inter cell connection “broke” (# 3 to # 4)
• Voltage was recorded (fluctuated and went to zero)
• Fire was contained

JAL case:

• Energy was enough to sustain thermal runaway


The rationale is:

ANA battery energy was lost in the external short circuit. The capability to expel fire was reduced and fire was contained inside the battery case. IMO both batteries were going to caught fire.

[RR_NDB]

Hi,

FlightPathOBN:

In regards to the batteries, in the fwd EE bay, it appears this is run like a UPS, where the power is constantly being drawn through the battery system, to provide a clean source for the avionics, else there would not have been an issue in-flight. IF that is the case, the batteries are in constant use.

In your model what is the function of the diode module?

IMO the MAIN and APU batteries are kept OFF LINE.

Exceptions (batt.):

MAIN: DC bus below ~30 V (including obviously, negative going spikes)
APU: APU start or towing lights consumption (with no APU)

(Most of use after you enter the plane and starts to use electricity, if no GPU and before APU)

[Lyman]

Hi RR

The danger of fire (outside battery case) IMO reduced after this moment

After the voltage dropped to zero. To conclude that loss of load on the battery prevented further fire, you have to assune the thermal runaway that had started and spread to other cells, would also cease because there was an open? At this point, how is voltage relevant?

I view the problem the other way, that the monitoring/controls system worked fine, the thermal runaway was due Battery issue, not control issue.

But it does not matter the cause, the runaway was an anticipated event. And a runaway, by definition, won't respond to further controls, hence "runaway"...

The nuts and bolts is the word, "contain". Again, had there been no propagation of thermal event, to other cells, the regs remain satisfied. We had to listen to Boeing repeat ad nauseum that the environmental protections functioned as designed. It seems they did, subject to a heated discussion between paid professionals....

You have to sense how frustrating it is for Boeing. The only thing that went wrong was that runaway propagated. JAL APUBatt burned for 75 minutes.

An hour and fifteen minutes! And yet the aft E/Ebay looked pretty ok...

That goddam pissant propagation! And even then, the house did not burn down.

But they have only themselves to blame. As it should be. They stand to make a half Trillion dollars on this mark.

I think they will.

:ok:

[TURIN]

In 787 the MAIN battery are kept charged separated from the bus by a diode: A "high speed switch" that is controlled by the bus voltage. When the bus drops below (estimated) 30 V the battery (if it is ON) supply current to the bus to maintain it´s voltage at required values. A low voltage in the DC bus would make the loads (electronics) fail.


Thats not how I read it.

The BDM (Bat Diode Module) is there to stop the battery being 'charged' from the Hot Bat Bus in the event the Hot Bat Bus is connected to one of the [live] main DC Busses. It's just a non return valve as a back up to a bus breaker/contactor.

The Battery Charger is supplied from a different source (Capts Instrument Bus).

In regards to the batteries, in the fwd EE bay, it appears this is run like a UPS, where the power is constantly being drawn through the battery system, to provide a clean source for the avionics, else there would not have been an issue in-flight. IF that is the case, the batteries are in constant use.

In your model what is the function of the diode module?

IMO the MAIN and APU batteries are kept OFF LINE.

Exceptions (batt.):

MAIN: DC bus below ~30 V (including obviously, negative going spikes)
APU: APU start or towing lights consumption (with no APU)

(Most of use after you enter the plane and starts to use electricity, if no GPU and before APU)

More or less correct.
The APU Bat will ONLY be used to start the APU if no other AC source is available.
The Main Bat again will only be supplying if main DC is not supplying.

The exceptions are: Towing Switch.
APU Bat supplies the Nav lights.
Main Bat supplies brakes, No.1 VHF Tx, etc.

On Bat refuelling.
Main Bat supplies fuel quantity indicating system and limited refuel valve operation.

For what it's worth my opinion is that the majority of battery replacements have been due to the towing and perhaps refuelling switches being left 'on' for too long.:hmm:

[RR_NDB]

Hi,

TURIN:

Thats not how I read it. The BDM (Bat Diode Module) is there to stop the battery being 'charged' from the Hot Bat Bus in the event the Hot Bat Bus is connected to one of the [live] main DC Busses.

Thats how I read it! Since first moment learned on use of BDM.

The Battery Charger is supplied from a different source (Capts Instrument Bus).

Yes. Designers put the important charger switch in LH side. APU switch was left to RH.

It's just a non return valve as a back up to a bus breaker/contactor.

The BDM assures the only path to charge MAIN batt. is from it´s charger. Why? Because Li ion batteries are far more critical WRT to charging. When i first learned on it´s adoption for 747 i was concerned. The BDM "solved the concerning". You have a good approach.

Return valve is a good analogy.

The APU Bat will ONLY be used to start the APU if no other AC source is available.

Sure! APU batt. Is the secondary (redundant) resource.

The Main Bat again will only be supplying if main DC is not supplying.

I.e. when there is no DC (lower than a given value) in the BUS. I.e. when nothing (from AC source) is feeding DC bus. In this condition MAIN battery supplies (automatically) required energy to the bus through the BDM. (if batt. switch is ON)

The exceptions are: Towing Switch. APU Bat supplies the Nav lights.

:ok:


Main Bat supplies brakes, No.1 VHF Tx, etc.

If "DC bus requires it" BDM allows flow from MAIN batt. to the bus.

On Bat refuelling. Main Bat supplies fuel quantity indicating system and limited refuel valve operation.


:ok: Again, if DC BUS requires it from main batt. As i understand if DC BUS is receiving DC from other sources (from AC of GPU, APU or gennies) MAIN batt. remains OFF LINE.

For what it's worth my opinion is that the majority of battery replacements have been due to the towing and perhaps refuelling switches being left 'on' for too long.


Towing as i imagine is light consumption and "short" duration. It would be more probable more replacement of MAIN batteries. IMO much more probable to be inadvertently discharged below design limits. (designed to preserve and to avoid recharging a yet compromised battery)

In laptop batteries the voltage span from "empty to full" is about JUST ONE VOLT in a 12 V pack (3 cells in series). Therefore a VERY conservative use.

Fact is, these cells are wonderful but requires a lot of care. From design to end of life. And can be dangerous throughout it´s (entire) life. Someone here in pprune commented on fires of Li batteries dumped in trash in UK.

[TURIN]

RR

I think we are both on the same page now.

Just one thing.
The towing switch is a selected function, not automatic.
Depending on Main Batt charge state, there may only be enough power for a half hour tow.

Likewise, refuelling on batt, there is only enough power for approx 15 mins. The logic being that 15 mins is enough time to get enough fuel in to the left main fuel tank to start the APU. :suspect:

Quote:
The Main Bat again will only be supplying if main DC is not supplying.

I.e. when there is no DC (lower than a given value) in the BUS. I.e. when nothing (from AC source) is feeding DC bus. In this condition MAIN battery supplies (automatically) required energy to the bus through the BDM. (if batt. switch is ON)



Just to be clear, the BDM sits beteen the battery and the hot batt bus. The hot bat bus is isolated from the main DC bus unless DC bus power is lost. :ok:

[cockney steve]

@RR-NDB I think we,re all happy with the notion that the main problem is centred around the care of thr battery. As you say, the voltage-range on a laptop "full" to "empty" is only 1V. This has to be taken in context. the discharge characteristics of the cell are such that there is minimal voltage-change over a large portion of the charge/discharge curves. A bit like the "reserve"fuel that every commercial aircraft tankers around on every flight....it only gets used in the rare case like the GIMLI Glider I don't know the statistics but would hazard a guess of once in 5 years worldwide.
Despite the forgoing, the SAFE USABLE amount of power is still ahead on the weight/volume stakes.
Yet here we have 50 aircraft which have, statistically, EACH used up their "reserve electricity" supply 3 TIMES in their service-life.

That doesn't even factor-in the age-spread across deliveries, so the mean aircraft service- life is probably ~2 years....That makes the apparent cover-up even more dramatic.


Were each individual sub-cell to be spaced above and below with a thermal insulator and connected to it's "common" (Paralleling) busbars with fusible-links, this, IMO would go some way towards addressing the present inherent problems.

Any faulty/abused sub-cell would tend to self-isolate and burn itself out without compromising the entire cell and battery-pack. Yes, i appreciate it would reduce the capacity of the individual cell-assembly,but the whole battery could still be available.

Regarding the modellers....there are a LOT more out there than the number of "screamliner2 batteries in service....by the nature of things, their usage is much more erratic, timewise, their charge-discharge cycles are heavy, intense and frequent. there are THOUSANDS of sucessful flights performed worldwide every week...so the "Crash'n burn scenario is statistically miniscule....and these are not "Certified by the CAA" but commercial, cheap as chips, mainstream items bought and operated by untrained/self-taught amateurs..

I'd suggest anyone interested ,should look at the "RUNRYDER" model Heli forum. a perusal of the electric Fora could prove enlightening.

[RR_NDB]

Hi,

TURIN,

Just to be clear, the BDM sits beteen the battery and the hot batt bus. :ok: As i understand to make impossible battery receive energy from the DC BUS (where voltage is not "regulated" i.e. may vary in a range as any DC BUS)

The hot bat bus is isolated from the main DC bus unless DC bus power is lost.I imagine the BDM function as:

If MAIN batt. is switched ON., (normally should be ON because it´s supposed to be "healthy") and DC BUS power is lost BDM "connects" AUTOMATICALLY MAIN batt. to maintain DC BUS with nominal voltage. The automatic (fast in miliseconds range) transfer is ABSOLUTELY NECESSARY. Why? In previous a/c the DC BUS is ALWAYS connected to the battery. Not in 787. The immediate connection is done by the "valve" (BDM) you mentioned. :)

The towing switch is a selected function, not automatic. :ok: As it should be. Not a critical item. Important but not critical. Manual is OK.

Depending on Main Batt charge state, there may only be enough power for a half hour tow. You mean,APU batt. OK? (Not MAIN batt. state)

Likewise, refuelling on batt, there is only enough power for approx 15 mins. The logic being that 15 mins is enough time to get enough fuel in to the left main fuel tank to start the APU.It´s adequate.

cockney steve: Ref 08:12

I think we,re all happy with the notion that the main problem is centred around the care of thr battery.Certainly.

Will comment later on other points.

Rgds,

[green granite]

Likewise, refuelling on batt, there is only enough power for approx 15 mins. The logic being that 15 mins is enough time to get enough fuel in to the left main fuel tank to start the APU.

Are you really saying that the basic circuitry needed to refuel one tank draws 260 Amps?

[RR_NDB]

Hi,

green granite:

(http://www.pprune.org/rumours-news/505455-faa-grounds-787s-41.html#post7694572)Are you really saying that the basic circuitry needed to refuel one tank draws 260 Amps? (http://www.pprune.org/rumours-news/505455-faa-grounds-787s-41.html#post7694572)

May be a limitation in order to leave energy on battery for other uses. :confused:

And the 65 Ah (260 A for 15 minutes) would not happen (remember the Peukert effect) :8 :)

[TURIN]

Are you really saying that the basic circuitry needed to refuel one tank draws 260 Amps?

Nope. Boeing are saying that if you leave the refuel switch 'on' for too long there will not be enough power left in the battery to a, start the APU. b, supply other systems during power up.

An example: Many years ago we had a flat battery on a 737-200. It was so flat that there was insufficient power available to operate the external AC power contactor. Fortunately the 737 also had a DC external power connector in the EE bay.
787 does not have that option.

I don't have the schematics with me and I can't remember whether the refuelling battery switch is connected to the Main hot bat bus or the APU hot bat bus. :O


I imagine the BDM function as:

If MAIN batt. is switched ON., (normally should be ON because it´s supposed to be "healthy") and DC BUS power is lost BDM "connects" AUTOMATICALLY MAIN batt. to maintain DC BUS with nominal voltage. The automatic (fast in miliseconds range) transfer is ABSOLUTELY NECESSARY. Why? In previous a/c the DC BUS is ALWAYS connected to the battery. Not in 787. The immediate connection is done by the "valve" (BDM) you mentioned.

Not quite.

The BDM is between the battery and the HOT BAT BUS not the main DC Busses. As it's name suggests the Hot Bat Bus is always 'live'.

The Hot Bat Bus is connected to the Main DC Busses via the Hot Bat Bus Contactor.

Quote:
Depending on Main Batt charge state, there may only be enough power for a half hour tow.

You mean,APU batt. OK? (Not MAIN batt. state)



No. The APU Bat when towing only powers the Position (Nav) lights.

The Main Bat powers the essential towing items such as VHF1, brakes (& Anti collision beacons-I think).

There is a very simple indicator on the flight deck that shows battery state when the a/c is unpowered. It simply shows High, Medium, Low.
When beginning a tow, this will give the engineer/mechanic a reference to how long they have to complete the tow. I have also heard that automatic load shedding will occur if the bat state gets too low, IE. VHF1 is lost. etc.

[green granite]

Since the discharge curve for lead-acid and Li-Ion batteries are very different Peukert's law would be much nearer to being negligible for Li-Ion, and if the batteries are allowed to rise in temperature to 131°F you get nearly as much energy no matter how hard you drive them.

[Lyman]

TURIN Thanks for your wealth of knowledge and your no nonsense style.

It seems that there are some minimal demands on these Batteries when the a/c is powered down, eg, POS lights, FUEL indicator, DOOR position, etc.

A question I asked long long ago. These Lithium Ion batteries have a well proven long life as to SOC, and a less proven profile relative to daily use, discharge, environmental factors, and Handling error.

Would it have been perhaps a better idea to have a powered down 'Battery system' of a more proven nature to accomplish the mundane chores we are discussing here?

The Backup Batteries are a flight critical system, and perform just fine in that regard, it would seem.....?

Penny wise, pound foolish?

[RR_NDB]

Hi,

TURIN:

Many years ago we had a flat battery on a 737-200. It was so flat that there was insufficient power available to operate the external AC power contactor. Fortunately the 737 also had a DC external power connector in the EE bay.
(http://www.pprune.org/rumours-news/505455-faa-grounds-787s-41.html#post7694707):ok: Redundancy (DC EXT PWR) was necessary. :)

The Hot Bat Bus is connected to the Main DC Busses via the Hot Bat Bus Contactor. So, 787 has:

1) Relay/contactor inside battery (as we imagine from pictures) for batt. ON/OFF
2) BDM between STD batt. connector and HOT BATT BUS
3) HOT BATT BUS contactors to DC BUSsess (LH and RH)

Electrically speaking is similar what first thought.

The APU Bat when towing only powers the Position (Nav) lights.The Main Bat powers the essential towing items such as VHF1, brakes (& Anti collision beacons-I think).

Indeed, brakes, comm and Anti collision beacons, certainly.

I initially thought of APU batt. for this items but to save weight and cost you don´t have higher current cabling between batteries. Just control wiring.

There is a very simple indicator on the flight deck that shows battery state when the a/c is unpowered. It simply shows High, Medium, Low. When beginning a tow, this will give the engineer/mechanic a reference to how long they have to complete the tow. I have also heard that automatic load shedding will occur if the bat state gets too low, IE. VHF1 is lost. etc. I consider it enough! The Li ion actually doesn´t require a voltage indicator. it´s voltage span is small. 3 levels is perfect. Simple and efficient.The load shedding is a good approach to allow a prioritized graceful degradation. Avoiding damage to any cell. (other batteries are more tolerant)

The design sounds perfect.

green granite:

Since the discharge curve for lead-acid and Li-Ion batteries are very different Peukert's law would be much nearer to being negligible for Li-Ion, and if the batteries are allowed to rise in temperature to 131°F you get nearly as much energy no matter how hard you drive them. :ok: One of the appeals for designers adopt it.

no matter how hard you drive them.:eek: For a 65A (75 A nominal) What would be a designers (787) peak limit?
(For MAIN batt. i mean) This specific aspect concerns me.

For APU i guess there is no big problem. Soft start, etc.

My concern in the MAIN also is: Li ion use was really very important?

WHY?

[peter we]

Working backward, FAA accepted a single cell would not cause propagation (further runaway). So the assumption is BOEING designed, built, and tested a platform that demonstrated this to the satisfaction of BOEING. And to FAA.

The battery failed the real world test.
So working backwards, Boeing did not test it for certification, unless they deliberately introduced a battery with known design flaws and covered it up.

2) The problem to isolate a defective cell is: You need a costly relay and you reduce the voltage of the battery. It´s not practical.

Sorry, thats bull****. The individual cells are monitored and isolated if defective, they have to be. A relay costs a few dollars in a $16k battery FFS.

[mm43]

The individual cells are monitored and isolated if defective, they have to be. A relay costs a few dollars in a $16k battery FFSThats 8 relays, and each time you drop a series cell you drop the output by 4V!

Ultimately, where is the power for the relays coming from? A back-up Ni-Cad??

[green granite]

To say nothing of the huge current they would have to be capable of switching, I think you would need an OCB to do that job.

[peter we]

Power and voltage are interchangeable, the overriding principle is to avoid a fire.

[Pub User]

The individual cells are monitored and isolated if defective, they have to be.

Have you seen the picture of the battery? The only thing that will isolate those cells is a spanner.

[Lyman]

Precisely. It's all or nothing, and the Battery better disconnect at the front of the case, from both leads. God forbid an external short from a terminal to the steel case. That could then end up as a dead short for the entire system.

That is what the "Zero Voltage" on ANA was all about. Any shutdown must be an instant complete removal from the circuit. And the reason I think the system worked for ANA.

[ATC Watcher]

Heard this morning that Airbus will make an announcment today that they will switch back to CadNi instead of Lion batteries for the A350.

[cockney steve]

posts 820-824.

individual relays on the 8 cells would not work The real problem in thermal -runaway, is that each "cell" is, in fact a BATTERY

Another member has already pointed this out on one of the numerous therads running.

A "cell" consists of several small cells in PARALLELL this is the only way to achieve the design objectives of discharge-rate/overall capacity/fault-limitation.

I have already suggested, the way forward is to link each of these sub-cells to the "Cell" terminal with a fusible link. If you look at the photos, you will see the terminal post is rivited onto the top of the cell-casing....I'd suggest that Pos. and Neg, busbars go down the stack and the individual sub-cells are parallelled to them. so, fusible links-each cell to busbar....fusible link of the necessarily higher order , to connect the internal busbar to it's terminal.


Cheap, effective AND EVERY SINGLE CELL HAS PROTECTION FROM OVERHEAT

Irrespective of wether it's caused by cell-fault, overcurrent, overcharge or over-discharge.

Assuming Boeing refuse to lose face and ditch the technology altogether, this would majorly address the safety-issue....the charger-unit and the connection direct to a "dirty" bus (OK, via a contactor/relay) are something else.

A failsafe strategy as outlined above would be cheap and easy to integrate and be very cost-effective.

Boeing/Thales can have the benefit of my "expertise" for free!!!!:}

No warranty given or implied. (like the existing batteries, then ?)

[Speed of Sound]

The only thing that will isolate those cells is a spanner.

Sadly not! :-(

http://www.straitstimes.com/sites/straitstimes.com/files/photo_1360260658689-1-0.jpg

[Lyman]

The "APU" Battery, and the "MAIN" Battery. These are misnomers.

Each Battery system is a group of eight separate batteries. Each battery has three cells.

The Eight Batteries are connected in series and contained in a Stainless Steel enclosure.

It is not possible to "isolate" one battery from its seven sisters. To do so interrupts the series.

One bad battery, no more "group". IF the system works correctly.

I hope I have that right, I have been referring to the Back up power system that way since the outset.

For whatever reason the nomenclature took that turn, it misleads. "Ah, just the one "cell", then, not so bad...." Any problem with one of the eight batteries disables the entire back up system. That is a game changer, appearance-wise.

The ANA Captain reported a "zero Voltage". As if that is an anomaly?

That is not an anomaly, that is the design. And it frames the dependability of the flight critical system as suspect.

[WHBM]

Airbus dumping Lithium batteries on A350

http://www.nytimes.com/aponline/2013/02/14/us/ap-us-airbus-batteries.html?_r=0

a clever move by Airbus at just the right time ! This will make it pretty well impossible for Boeing to now claim they can come up with an adequate method to continue with Lithium, where the other mainstream manufacturer also now says they can't be relied on. It will derail the 787 programme for months. Meanwhile the A350 test programme will start with the Lithiums, but without being certified for pax of course.

It is, of course, the right course of action. I wonder if Boeing have even started the drawings for going back to previous battery technology.

[Lyman]

The problem as I see it is that Boeing designed the Backup Battery systems to take on other tasks. That means it will be connected in the distributed system and any problem becomes a systems problem, a 'systemic' problem.

Talk of "isolation" should have stopped with the "Backup Function". If the breakers that remove the Backup system from the distributed system are within the Batteries' enclosure, how is that a dependable "open"?

The switching is remote from the Batteries' case, right?

SoS... There is your "Fusible Link", eh? That is battery #6 @ #5? Let's hope that was not the source of the Captain's "Zero Voltage"....Hopefully the breaker tripped prior?

[RR_NDB]

Zero voltage (very probably) happened when cell # 3 lost it´s plus terminal due intense heat generated in internal Ohmic losses after a severe short circuit to ground.

There are evidences for this "model". This, likely will be publicized by JTSB.


In earlier posts i commented thoroughly on that.

[fc101]

Airbus dumping Lithium batteries on A350

http://www.nytimes.com/aponline/2013...ries.html?_r=0 (http://www.nytimes.com/aponline/2013/02/14/us/ap-us-airbus-batteries.html?_r=0)


It is, of course, the right course of action. I wonder if Boeing have even started the drawings for going back to previous battery technology.Also that Airbus have the chance to redesign parts of the electrical system as necessary. Which brings up another question, *if* Boeing have to change the batteries, how much of a change to the electrical system is required and how much then to recertification?

[bsieker]

Lyman (and others ...),

Each Battery system is a group of eight separate batteries. Each battery has three cells.

Again, please.

Where does this information come from? All I see in the labs are completely unfolded, long, continuous strips. One strip, i. e. one cell, per cell.

The cells are folded. There are no subcells. Neither is it necessary to achieve higher currents. The only relevant parameters are electrode chemistry and effective surface.

Also, it does not matter whether there is a short circuit in one larger cell, or in one of three parallel "subcells".

[Lyman]

RR

Zero voltage (very probably) happened when cell # 3 lost it´s plus terminal due intense heat generated in internal Ohmic losses after a severe short circuit to ground.

God help us all...

I am saying it was severed by a metallic Lithium flare in the battery beneath.

If the system had not shut down (electrically, continuity interrupt), Thales has some "splainin" to do....

Bernd

The cells are folded. There are no subcells. Neither is it necessary to achieve higher currents. The only relevant parameters are electrode chemistry and effective surface.

NO. Not in my understanding. In each battery are three separate electrodes, cells, consisting of a continuous "stack" ten meters long, folded. The length of all three is 30 meters, nominally...

:ok:

Stand to be corrected....

[syseng68k]

C/mon guys, haven't we been through all this stuff about cells ad nauseum already ?.

Boeing should stick with lithium imho. Just bring in some decent systems engineering
bods to fix the problem and lock away the beancounters for a few months :ugh:. Just
because airbus have run scared for political / business reasons doesn't mean the
original ideas were invalid. It's a proven technology and just needs to be properly
engineered.

It will probably take months to fix this, but that's the price you pay when you hand
off responsibity to many vendors, with inadequate engineering oversight and thus
lose track of the big picture...

[Lyman]

syseng68k

C/mon guys, haven't we been through all this stuff about cells ad nauseum already ?.

Given there may have been misunderstanding right along, apparently not?

[RR_NDB]

Just bring in some decent systems engineering bods to fix the problem and lock away the beancounters for a few months . Just because airbus have run scared for political / business reasons doesn't mean the original ideas were invalid.

Competition and Marketing reasons recommended FOR NOW.

It's a proven technology and just needs to be properly engineered.


To show that is PROVEN. :)

I am saying it was severed by a metallic Lithium flare in the battery beneath. (http://www.pprune.org/rumours-news/505455-faa-grounds-787s-42.html#post7696690)

Did you see the ground wire destroyed? Did you understand the equivalent circuit i posted showing a HIGH current path capable to fuse the (ground) wire? Fire crews had to fight against fire in TAK taxiway? (in BOS they had) (http://www.pprune.org/rumours-news/508100-airbus-announces-will-not-use-lithium-batteries-upcoming-model.html#post7696801)

[Lyman]

Hi RR NDB

To make your conclusion requires the circuit breaker to have failed. That is unlikely.

To make your conclusion requires the geometry of the deficit to resemble other melted events, which it does not.

The geometry resembles, clearly, the action of a gas Jet, not a fusing failure.

Look again at the deficit on the top of the Battery. It too is shaped in a triangular, wedge form, suggesting an explosive escape of typical gas flares from this type of battery.

If the Thales designed system worked (I think it did), there would have been no battery voltage available to separate the connecting bar.

This damage is from Thermal runaway; the entire design is structured to avoid the type of event you describe.

I also believe the quantity of heat necessary to so seriously corrupt that connector is not available via Battery voltage alone.

Occam is our friend?

[p1fel]

Porous silicon particle anode 'triples capacity' of lithium-ion battery.

Read more: Porous silicon particle anode 'triples capacity' of lithium-ion battery | News | The Engineer (http://www.theengineer.co.uk/news/porous-silicon-particle-anode-triples-capacity-of-lithium-ion-battery/1015538.article#ixzz2Kzbk80bRBattary) technology

[Mark in CA]

“Airbus considers this to be the most appropriate way forward in the interest of program execution and reliability,” said Marcella Muratore, an Airbus spokeswoman.


Yes, I can understand how this change might reduce production risks, but I can't help thinking this is not just about production risks (unless by that you also include no one wanting to buy your plane). There must be a not-insignificant public relations aspect to this decision, too. No matter how the Boeing situation turns out, Li Ion technology is damaged goods in the public eye, at least for this kind of application. Airbus is probably protecting its sales and marketing by avoiding any potential public backlash against a decision to continue with their use of a suspect technology.

[ZFT]

(unless by that you also include no one wanting to buy your plane).

I thought some 595+ orders sort of negates that statement?

[Momoe]

"I thought some 595+ orders sort of negates that statement?"

595 historical orders, you could start a new thread on the impact this will have on Boeing's sales, suffice to say that Airbus (shrewdly) taking the initiative on reverting to NiCd puts Boeing between a rock and hard place.

To be fair, if Airbus hadn't had the A380 delivery issues and then the AF447, the A350 might be in a similar situation. However, Airbus have scored with this one albeit an own goal by Boeing.

[John Farley]

There must be a not-insignificant public relations aspect to this decision

I'm not so sure about that. I don't feel posters here are typical of the travelling public.The people that keep airlines afloat shuffle on board down a tunnel and in my experience often don't even know what aircraft type they are sitting in "Its a jet isn't it?"

[poorjohn]

Since this thread has gotten to be much about battery technology I feel free to ask "why NiCd (as mentioned upthread re A350 etc) and not NiMH?"

Wikipedia says in part "A NiMH battery can have two to three times the capacity of an equivalent size NiCd, and their energy density approaches that of a lithium-ion cell.

The typical specific energy for ... larger NiMH cells is about 75 W·h/kg (270 kJ/kg). This is significantly better than the typical 40–60 W·h/kg for NiCd, and similar to the 100-160 W·h/kg for lithium-ion batteries. NiMH has a volumetric energy density of about 300 W·h/L (1080 MJ/m³), significantly better than NiCd at 50–150 W·h/L, and about the same as lithium-ion at 250-360 W·h/L.

Useful discharge capacity is a decreasing function of the discharge rate, but up to a rate of around 1×C (full discharge in one hour), it does not differ significantly from the nominal capacity.

The significant disadvantage of NiMH batteries is the high rate of self-discharge; NiMH batteries lose up to 20% of their charge on the first day and up to 4% per day of storage after that. In 2005, a low self-discharge (LSD) variant was developed. LSD NiMH batteries significantly lower self-discharge, but at the cost of lowering capacity by about 20%."

[mm43]

poorjohn,

The following extract from www.mpoweruk.com (http://www.mpoweruk.com/nimh.htm) may provide more insight into the shortcomings of NiMH cells.


High self discharge rate.
Can be stored indefinitely either fully charged or fully discharged, but
Suffers from memory effect though not as pronounced as with NiCad batteries
Battery deteriorates during long time storage. This problem can be solved by charging and discharging the battery several times before reuse. This reconditioning also serves to overcome the problems of the "memory" effect.
High rate discharge not as good as NiCads
Less tolerant of overcharging than NiCads
As with NiCads the cells must incorporate safety vents to protect the cell in case of gas generation.
The coulombic efficiency of nickel metal hydride batteries could be up to 85% but is typically only around 65% and diminishes the faster the charge although this is projected to improve.
While the battery may have a high capacity it is not necessarily all available since it may only deliver full power down to 50% DOD depending on the application.
Cell voltage is only 1.2 Volts which means that many cells are required to make up high voltage batteries. The competing Lithium cells typically have 3 times the cell voltage (3.2 Volts to 3.7 Volts) and a much higher energy density.
Lower capacity and cell voltage than alkaline primary cells.
Limited supplies of rare earth element Lanthanum. Mostly in China.

[poorjohn]

mm43: I appreciate the additional input but only a couple of the points as noted below might argue for NiCd vs NiMH for aircraft use, so I still wonder what really drives the designers in that direction.

"High self-discharge" of little concern in machines that fly much of every day. Plenty of ways to manage exceptions.

"memory effect...not as much as NiCads" is a plus, when comparing to NiCads

the bean-counters hope that ops avoids "long-time-storage" of their fleet

"high discharge" performance would need to be evaluated. Maybe that's a problem.

"less tolerant of overcharge" should be managed by design

"safety vents...as with NiCads" is a null argument in this comparison

"coulombic efficiency" - NiCad is better?

"capacity ... not necessarily all available" - NiCad is better?

"Cell voltage is only 1.2 Volts" sounds exactly like NiCad

"[worse] than alkaline primary cells" makes no sense in the comparison

"Lanthanum [is scarce]" doesn't seem to be an issue for the millions [?] of NiMH cells sold in the consumer market. (I understand that rare earths are in fact present in the U.S. but cheap Chinese supply made mining uneconomical a few years ago.)

[wooski]

seems the eneloop over come a few of the issues of traditional nimh.
really good write up of the tech details, be sure to read the updates from sanyo.

http://www.stefanv.com/electronics/sanyo_eneloop.html

"High self-discharge" of little concern in machines that fly much of every day. Plenty of ways to manage exceptions.

"memory effect...not as much as NiCads" is a plus, when comparing to NiCads

the bean-counters hope that ops avoids "long-time-storage" of their fleet

"high discharge" performance would need to be evaluated. Maybe that's a problem.

"less tolerant of overcharge" should be managed by design

"safety vents...as with NiCads" is a null argument in this comparison

"coulombic efficiency" - NiCad is better?

"capacity ... not necessarily all available" - NiCad is better?

"Cell voltage is only 1.2 Volts" sounds exactly like NiCad

"[worse] than alkaline primary cells" makes no sense in the comparison

"Lanthanum [is scarce]" doesn't seem to be an issue for the millions [?] of NiMH cells sold in the consumer market. (I understand that rare earths are in fact present in the U.S. but cheap Chinese supply made mining uneconomical a few years ago.)

[ozaub]

Surely the 787 engineers and their bosses in Chicago realize that all eight Special Conditions for the use of Lithium Ion batteries (posted at #111) are US Federal Law. It is not a legal option to just contain any battery fire, Boeing must also prove:
(1) Safe cell temperatures and pressures must be maintained during any foreseeable …. condition ….
(2) Design of the lithium ion batteries must preclude the occurrence of self-sustaining, uncontrolled increases in temperature or pressure.
Nor would containment alone be publicly acceptable. Boeing had best follow Airbus and revert to NiCads.
FWIW my views with historic context are published at: Dreamliner's assault and battery on Boeing's name (http://www.smh.com.au/opinion/dreamliners-assault-and-battery-on-boeings-name-20130129-2dj18.html)

[denabol]

Is it possible that loads of humid sweaty passengers are the reason the batteries are having troubles?

The Plane Talking blog often comes at things from a different angle not really technical but this had me wondering if there isn't some left field reason for this all happening once the 787s are in service.

Dreamliner woes: Are sweaty passengers to blame? | Plane Talking (http://blogs.crikey.com.au/planetalking/2013/02/17/dreamliner-woes-are-sweaty-passengers-to-blame/)

[aterpster]

The new issue of Aviation Week is predicting that the 787 will not return to service for this summer peak season.

[Uncle Fred]

I am surprised that the speculation says just over the summer season. I have heard reasonable and sober sources stretch the dates out to the year's end. I do not have purview to venture an estimation but running it out twelve months would not surprise me.

Maybe reduced rates on 777s might fill the breach until the behind the wire reserve battalions can move forward. At least in the U.S. there are an innumerable number or 50 seat regional jets that can step up to do yeomen's duty. They nailed their flag on to the little frames that the passengers
Love...

I do think it will be fall before we see real possibilities for a flying test plan. Could be wrong. Lots of work to be done and the other countries will be watching closely.

[pax2908]

Perhaps somebody who knows could explain (or maybe I missed this) why it was so difficult to have another option open for the batt chemistry. Presumably they became committed to Li-Ion very early in the design? I somehow understood the structural aspect (design of EE bay layout, support structure...) but I find it hard to believe the associated risk was not considered. Regardless of what actually caused the incidents that led to the current situation.

[Mr Optimistic]

JF, ''I'm not so sure about that.''

Indeed. How much damage was done to the public's perception of AB after AF's little mishap ? Suggest all forgotten in general public's mind. Last general disquiet was probably the DC-10 wasn't it ?

[Speed of Sound]

Suggest all forgotten in general public's mind.

Forgotten?

If it was ever there in the first place. I was talking to someone who flies almost as much as I do, about AF 447 and he had no idea what I was talking about.

but I find it hard to believe the associated risk was not considered.

It was, which is why special conditions were put on certification.

[poorjohn]

Hopefully someone with pertinent knowledge will jump in to offer an explanation for why a (hopefully) growing fleet of expensive aircraft would be allowed to remain grounded for months for want of an acceptable battery or two.

1. Corporate insanity?
2. Mountain of internal processes making the path forward glacial-speed?
3. Intense FAA review of certification found other serious non-battery concerns?
4. Battery charge/discharge electronics and software dispersed and tightly woven into the overall aircraft systems, making any change a vast undertaking?
5. Legal battles with suppliers?
6. ...?

Having spent a long career in military aerospace and watching the slide from personal responsibility to crowded meeting rooms deciding minor details, my personal guess would be (2), but since I had nothing to do with Boeing Commercial, please ignore me.

[syseng68k]

poorjohn:

This struck a chord with me:

Boeing's Real Problem With the Dreamliner: Bean Counter vs. Engineer - James Fallows - The Atlantic (http://www.theatlantic.com/business/archive/2013/02/boeings-real-problem-with-the-dreamliner-bean-counter-vs-engineer/272944/)

That and complex outsourcing, with no single responsible individual having enough
technical oversight to maintain a big picture view seems quite likely to me...

Regards,

Chris

[HalloweenJack]

Would oldrer types be kept on longer or sourced to fill any `gaps` - for example A330`s or A340`s , or 777`s on short leases?

[Girom]

Boeing readies short-term battery fix, facing uncertainty | Business & Technology | The Seattle Times (http://seattletimes.com/html/businesstechnology/2020373450_boeing787xml.html)

[EEngr]

poorjohn (http://www.pprune.org/members/213939-poorjohn):

watching the slide from personal responsibility to crowded meeting rooms deciding minor details,Lots of that at Boeing (other large corporations too).

The culture there is to smack down anything that doesn't fit into the team philosophy. One would seriously risk their career by going off an testing their own hypothesis without consensus from the crowd. Its better to fit in than go off on one's own than to pursue some avenue of investigation, even if it had a reasonable probability of succeeding.

I'd suspect that Boeing has a Plan A/Plan B strategy in place. First, take a certain amount of time and resources to investigate the LiON technology and find a fix. Failing that, fall back to an already certified off the shelf battery system (probably NiCad). So now Plan A proceeds, but with everyone having an investment in the team plan and contributing to the consensus. God help the poor fool who grabs a battery, runs off to the lab and finds the solution on his or her own. As long as Plan B exists, why risk a career by playing cowboy?

[toffeez]

Leaving aside national politics, if I were to tell you that Airbus does not have a committee / hierarchy culture I'd be spilling the beans on their success. Boeing knows that.

[Smilin_Ed]

It's hard to understand why someone at one of the airlines interested in the 787 didn't question the use of these batteries to begin with. :ugh:

[BBK]

Are any 787s flying again even if its only for the purposes of a ferry flight?

Actually, I imagine if any have flown it would only be with essential crew. Just curious as I saw the Qatar Airways one at LHR with its anti collision beacon on yesterday. Could just be a maintenance check of course.

[poorjohn]

This AvWeek on-line article dated 2/15 - AvWeek article (http://www.aviationweek.com/Article.aspx?id=/article-xml/avd_02_15_2013_p03-01-549218.xml) - apparently pre-dates the up-thread mention of a prolonged grounding

[grounded27]

At this point this thread needs to be moved to the Spectators group. The B741 was an extremely problematic aircraft yet is still one of the most successful aircraft in the sky. It shared the same new fears and awe.

[WHBM]

The B741 was an extremely problematic aircraft yet is still one of the most successful aircraft in the sky. It shared the same new fears and awe.
The 747 had no safety issues, no in-flight fires, was not three years late on first delivery, managed to deliver over 100 to the airlines in the first 18 months, pretty much at the original dates specified when orders were placed, and of course was not grounded by the FAA, in days when their oversight ability was way greater than now ......

It did have significant issues with the JT9D powerplant (most commonly by going slightly oval and abrading the seals). There were a number of in-flight shutdowns but it was a quad, and in all truth the shutdown rate was little different to what the 707/DC8 generation had experienced beforehand. Most JT9D issues were actually caught before departure, so there was some unreliability. It also had multiplex issues with its electrics. Of course, those were the days when aircraft were designed properly, so there were only cabin comfort items etc, not any critical features, using the multiplex. Boeing's designers in the late 1960s wouldn't have been so silly .......

[Erwin Schroedinger]

Am I missing something in the recent links? There doesn't seem to be much reaction on this thread.

Is Boeing seriously proposing that passenger operation be permitted by the FAA, subject to nothing more than increased monitoring and containment of the consequences of batteries overheating? :confused:

[cockney steve]

The B741 was an extremely problematic aircraft yet is still one of the most successful aircraft in the sky. It shared the same new fears and awe.
YES, but ,unlike the "screamliner", It did'n't suddenly.randomly and spontaneously combust:(
Regarding the article referenced by Girom,- a shower of tossers all trying to pass the buck for an enormous, unprecedented clusterfxxk .

Why the sudden kludge of putting it in a "tin" box with a drain-pipe over the side????....SURELY that was implicit in the original special certification conditions.

90 engineers to take 3 months to design a battery????...C'mon! what are they? high school students in a physics class? (the same shower that designed the present self-destruct system?

I'd call it dereliction of duty, professional malpractice and negligence if MY design-team had integrated a novel charger and battery-system without making sure that proven substitutes could be readily slotted in place.

pissup/brewery/ couldn't /organise... rearrange into a well-known saying and submit to Boeing shareholders.

Agree wholeheartedly with the last few posts by engineers...Boeings 787 pax are all in the boardroom.

[Kerosene Kraut]

The public won't buy any boxed fire approach without a credible root cause permanent fix. Better do it right from the beginning.

[ANW]

Production line conveyor belt continues. Interest times ahead in the parking lots.

787 Storage (http://www.flickr.com/photos/microvolt/8474114511/in/photostream/)

787s stored on Runway 11-29 and the tower apron at Paine Field February 14, 2013. Let's see now, there are about fifteen parking spots left on airport property. Eight 787s on the Boeing ramp, probably six or more in the factory and five coming out every month. Hmm.

[WHBM]

probably six or more in the factory and five coming out every month. Hmm.
Is the production operation still installing lithium batteries in these aircraft still coming down the line ???

[Onceapilot]

Love this quote from that Seattle Times article,

“Good engineers will know how to get the heat out of these cells,” Battaglia said. “If anyone knows how to do that, it’s Boeing."

:ouch:

[Romulus]

I'd call it dereliction of duty, professional malpractice and negligence if MY design-team had integrated a novel charger and battery-system without making sure that proven substitutes could be readily slotted in place.


Any other insights into design you'd like to share with us?

Which other systems should have "proven substitutes"?

All of them?

Hindsight allows a wonderful degree of accuracy, foresight is a bit trickier...

[FlexibleResponse]

787 Battery Containment Plan Firms Up (http://www.aviationweek.com/Article.aspx?id=/article-xml/avd_02_15_2013_p03-01-549218.xml&p=1)

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.

[rmac]

The first jet airliner, the Comet, was victim of a major design flaw and as a result handed the field to the Boeing 707.

Is the lead in civil aviation now headed back to Europe :E

[Heathrow Harry]

never, ever gloat in flight safety

Something horrible will be waiting round the next corner for sure if you do

[WHBM]

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.
I haven't seen any quotes yet about what the operating airlines think. It will be their reputation, and their liability insurance, that will be on the line. I would expect them to tell Boeing where they can stick such a proposal.

[Erwin Schroedinger]

The FAA should do the telling. Sooner rather than later.

Have Boeing lost the plot?

[cockney steve]

@ Romulus

ALL other "innovative" technologies that we are aware of in this particular aircraft construction, are well proven in plenty of other applications.

A "decision" was made to fit an unproven, known to be unstable battery and this was compounded by linking it to a "revolutionary, patented" controller/charger.

Are you REALLY suggesting that this was a well-thought out, well-engineered, safe system that met the SPECIAL CONDITIONS applied to it?

read the Forum ROE....don't know what your gripe with me is, but play the ball, not the player, thank you.

[742]

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

Boeing has not been listening to its engineers since 1997, and I see no indication that the current management and board are going to change.

[slf4life]

So, if I'm understanding Boeing's interim fix - a titanium box with a high pressure venting system should the batteries ignite?

Given the seeming inevitability of these fires, I can see it now, 787s farting fire as a matter of due course :ok:

[Romulus]

don't know what your gripe with me is, but play the ball, not the player, thank you.

No beef with you, the ball being played is the use of hindsight. It's easy to be critical of this decision now, I would suggest Boeing had done their work beforehand but something just hasn't worked as tested.

[RatherBeFlying]

Something similar to the design I saw on a DC-3 where the batteries sit on a tray that slides up into the fuselage.

If things get a bit hot, the retaining latches can be made of low melting point metal and the battery is ejected:}

Sorry, could not hold back until April 1.

[lomapaseo]

It has taken 45 pages to get around to the safety issues rather than how to design an infallible battery.

In the end both Airbus and Boeing have sufficient expertise to design a workable system for this type of battery. The issues have always been acceptable levels of safety under the regulations.

I suspect (without the data) that the regulators were not satisfied with the level of consequential damage to parts of the system as well as the level of concern to the pilots resulting in an emergency landing.

I still await a report from the investigators specifying how and why safety of flight was impacted.

[poorjohn]

Does failure of either battery during ETOPS mandate immediate diversion?

[Cool Guys]

Improving containment of the aircraft’s batteries in case of fire is the most important fix to be done. I have not seen any regulatory reason why the plane could not fly once this is done. I am sure other improvements can and will be done but the lack of containment was the show stopper.

If I was in the plane at FL350 I would be a lot happier with a solid titanium box etc around the battery than some committee’s decision that the cause of the fire was due to Dendrites/Whiskers or whatever and the manufacturing process has improved now.

Good decision Boeing

[Momoe]

If I'm reading the reports correctly, I'm amazed that Boeing are sticking with Lithium.

In fact, the more I read the more amazed I am; the problem appears to stem from an internal battery issue (Dendrites/Whiskers) or whatever, it's irrelevant - the fault lies within the battery.
This appears to be exacerbated by the physical design of the battery, if one cells fails catastrophically, the proximity of the cells causes adjacent cells to overheat and combust.
IMHO, this isn't fail-safe engineering and shouldn't be certified as such by Boeing, the FAA or anyone else.

Good luck to them if they think that encapsulating the battery in a (better) fireproof box as a short term measure will be regarded as a suitable workaround, Heath-Robinson springs to mind (For our friends across the pond, substitute Rube Goldberg for H-R).

C'mon Boeing, you can do better than this,

[Jando]

Improving containment of the aircraft’s batteries in case of fire is the most important fix to be done. I have not seen any regulatory reason why the plane could not fly once this is done. I am sure other improvements can and will be done but the lack of containment was the show stopper. ...


I won't be so sure about that. The ship's main battery is there (and you can't dispatch without it) not for operational reasons but for safety reasons. The battery is your line of defense in case of fuel starvation, fuel contamination, problems with the fuel system in general, remember iced up fuel pipes? The RAT won't cut it at low airspeed.

And now we have a battery with a basically unknown failure rate. Doesn't matter much whether a burning or smoldering battery is contained in that case - you just want it not burning so that the darn thing provides the power for your brakes ...

[Chu Chu]

Anything can fail. Surely a higher failure rate is permissible where there's redundancy. A battery is a redundant source of in-flight electrical power. It's not redundant as a non-cause of fire.

And it's probably a lot easier and faster to prove that a titanium box can contain a battery fire than it is to prove a battery won't burn. So the box may be the fastest way to get flying.

[amicus]

As nobody has mentioned this point yet, I will now, as if B.plans to vent burning electrolyte via a high pressure vent folly scheme, they have a flammable fuselage to contend with also. The only feasible and sensible is reverting to Ni-Cad as Joe Sutter and competent retired B engineers would have done and dump the lethal Li-ion nonsense until an improved and stable versions are developed. Otherwise they will have burning epoxy primary structure with a self ignition temperature around 580 degrees F to add to the present lethal mix. This is folly and nonsense of the highest order and unworthy of any rational aeronautical engineering company.

[ozaub]

Please, if you have not already done so, read the eight Special Certification Conditions which were set for use of Li-Ion batteries on the 787 Federal Register, Volume 72 Issue 196 (Thursday, October 11, 2007) (http://www.gpo.gov/fdsys/pkg/FR-2007-10-11/html/E7-19980.htm). Note that the dangers of using Li-Ion are clearly spelled out and prescient.
Note too that pilots (ALPA) were only respondents to NPRM which preceded SCCs. ALPA was adamant that a battery fire was unacceptable; “The intent of our comments submitted to the Docket for question [Special Condition] Number 4 (see below) is to assure that the FAA includes language or makes it clear in the Special Conditions directing the OEM or a potential STC applicant that a fire from these devices, in any situation, is unacceptable. ALPA requests the FAA reiterate that preventing a fire and not reacting to one, if one occurs, is critical”. FAA reassured them; “The FAA shares the commenter's concern over a fire erupting in flight. The regulations and the rigid requirements defined in these special conditions are intended to prevent lithium battery fires on board the aircraft”.
SCCs are not friendly agreements between consenting adults; they are law. 787 cannot fly unless all SCCs are met.

[Cool Guys]

Please forgive me if I am having a senior moment but I see no ruling under the special conditions 1 to 9 stated in the document Federal Register, Volume 72 Issue 196 (Thursday, October 11, 2007) (http://www.gpo.gov/fdsys/pkg/FR-2007-10-11/html/E7-19980.htm) that states there must never be a fire in the Li batteries under any circumstance. There are rulings that state mechanisms to protect against the possibility of a fire and containment rulings in case these protections fail. Sure, is seems the ALPA was adamant that a battery fire is unacceptable under any situation but no where can I see that the FAA accepted this view and included it in the special conditions 1 to 9 stated later in the document. In my opinion the FAA could not regulate that there must never be a battery fire of any degree under any circumstance but if there is in fact such a ruling then I agree, Boeing should ditch the Li batteries.

I am just talking about the "Special Conditions" regulatory requirements here. I do agree that 2 incidents (1 fire and 1 smoke) in the space of 1 week is too frequent. Such occurrences should be very rare. I also agree that the public perception would not be very good if Boeing does not find the root cause.

[Mk 1]

From FlexibleResponse: "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."

Or Airbus knows when it potentially has a tool to beat its competitor over the head with. Not in an overt way mind you - there will be subtle reminders...

[cockney steve]

in reply to Romulus[QUOTE] [the ball being played is the use of hindsight. It's easy to be critical of this decision now, I would suggest Boeing had done their work beforehand but something just hasn't worked as tested. /QUOTE]

The world was presented with a Certified and working airliner. nobody outside the regulatory authorities has any mandate to investigate the financial or engineering decisions behind the product.

I'd suggest that if you bought a TV,certified to meet international environmental and safety standards,then found it kept losing all it's settings,and reports were coming in that these sets were catching fire........your reaction????

Boeing's test procedures were , defacto, intrinsically flawed.OR they avoided testing the "difficult" areas that are KNOWN to exist.

(otherwise the problems with discharged/self-combusting batteries would have been found and dealt with before release.)

I do NOT accept that NOBODY in the whole of Boeing had any doubts about incorporating this "risky" technology.

Eventually, I suspect, a sacked/disaffected dissenter will spill the beans.

A poor decision was made to put all their eggs in one very fragile basket which failed virtually immediately

These batteries were changed-out at ludicrously low service intervals and still no warning-bells?

IMHO there would have been plenty of engineers who were well aware that the battery/charger/plane combination was sadly lacking.

I would point the finger at "suits" who were desperate to bring a much-hyped, much-delayed project to market.

Nothing to do with "hindsight" I do not accept that the system worked perfectly before release....the Kludge of putting it in a tin box didn't work.so let's make a bigger, stronger Kludge.....FFS...what sort of third-world "engineering" is that???

[Walnut]

So Boeings answer to the fire risk is to surround the battery with a fire proof case. One small problem, the main a/c battery is on board for a purpose, to provide power to various systems when all else fails.. If the battery ends up as a molten mass then that protection is lost. All sorts of systems come off the Hot battery bus. I guess the APU battery could be less of a problem, but it certainly would effect ETOPS.

[Ex Cargo Clown]

Are they using Ti-6Al-4V alloy for the box, if so, they'd better be careful, it's light, but I wouldn't want a fire in it!

[Romulus]

I'd suggest that if you bought a TV,certified to meet international environmental and safety standards,then found it kept losing all it's settings,and reports were coming in that these sets were catching fire........your reaction????

Fix it or Replace it.

I sure wouldn't be carrying on like a pork chop about how obvious the flaw is that was missed based on my brilliant use of hindsight.

[Kerosene Kraut]

Could they get any ETOPS permit with the hotpod-concept? Where's the redundancy for the hotpod?

[Momoe]

"And it's probably a lot easier and faster to prove that a titanium box can contain a battery fire than it is to prove a battery won't burn. So the box may be the fastest way to get flying."

Are you serious???

Before the 787, when was the last time an aircraft battery caught fire? Nope? I can't remember one either.

Two scenario's here, either the design and implementation process is flawed or the battery technology is insufficiently proven in an aviation environment.

Boeing need a solution but redneck engineering isn't it, you might get the planes flying but you then have to convince your business partners, who then have to convince their passengers.

787F anyone?

[green granite]

Boeing need a solution but redneck engineering isn't it, you might get the planes flying but you then have to convince your business partners, who then have to convince their passengers.

You also have to convince the Insurance companies, otherwise premiums might suddenly become uneconomic.

[Hi_Tech]

So shortly, if you are living under the flight path of a dream liner, and see a burning streak in the sky, it said not a meteor. It is just a dream liner ejecting a battery. Sad to see Boeing come to this solution.

[EEngr]

Hi_Tech (http://www.pprune.org/members/267492-hi_tech), it could be an A380 turbine blade.:uhoh:

[EEngr]

Swelling Found In Second ANA 787 Battery (http://news.airwise.com/story/view/1361262235.html)

I have to think that, were all the 787 batteries (failed or not) returned and disassembled for inspection, the cause of these failures would reveal itself in short (no pun intended) order.

[Kerosene Kraut]

They should just switch back to nicad-batteries. They'd have the perfect aircraft again.

[ozaub]

You’re right Cool Guys (#893), in certification we never say “never’. Instead SCCs refer to “extremely remote” possibility. FAA Advisory Circular 25-1309 defines that as “not expected during entire operational life of all airplanes of the type”.
Or as I wrote in an article referenced earlier; “Put simply, batteries must not burn, except possibly once or twice during the lifetime of the entire 787 fleet. If batteries do overheat or burn, any fire must be safely contained within the battery enclosure and any harmful fumes must be vented overboard”.
More recently NTSB quantified the risk; “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”.
BTW only 8 SCCs are necessary for certification. #9 Instructions for Continued Airworthiness can be developed progressively after certification.
I agree with KK, switch back to NiCads and avoid the SCCs completely.

[weekend_ppl]

If you've ever been around this kind of failure investigation before, the question of examining all the in service units you "think" are fine to see if they really are does jump out at you. We'll see if a "deviant" condition discovered in the "believed good" APU battery from the ANA aircarft leads to that. I've Googled and find no evidence to suggest they've been down that path. Yet.

Not like taking all these batteries out of the fleet will keep these aircraft from going anywhere...

One issue with this is that some of these conditions--dendrites in particular--can be very hard to find. The act of looking tends to destroy the evidence that they were there in the first place.

[TSR2]

With no sign of of restoration to flying status in the immediate future, when will Boeing run out of parking places for aircraft coming off the production line, and where will they carry out remedial work when a solution is finally approved ?

[poorjohn]

Any replacement battery needs to be capable of braking the airplane to a stop (under extreme weight and speed conditions, if they were honest in the specs).

People who know batteries (that's not me) have been posting and will enlighten us, but I don't think the discharge characteristics of any lesser chemistry will do that (without huge increase in weight/volume).

[Semaphore Sam]

If, as is inferred above, there has been a progressive marginalization of engineers from decision making at Boeing, then, BEWARE! It has happened before, with catastrophic results. From a perceptive observer of how the Shuttle O-ring disaster developed:

Feynman's account reveals a disconnect between NASA's engineers and executives that was far more striking than he expected. His interviews of NASA's high-ranking managers revealed startling misunderstandings of elementary concepts. For instance, NASA managers claimed that there was a 1 in 100,000 chance of a catastrophic failure aboard the shuttle, but Feynman discovered that NASA's own engineers estimated the chance of a catastrophe at closer to 1 in 100. He concluded that the space shuttle reliability estimate by NASA management was fantastically unrealistic, and he was particularly angered that NASA used these figures to recruit Christa McAuliffe into the Teacher-in-Space program. He warned in his appendix to the commission's report (which was included only after he threatened not to sign the report), "For a successful technology, reality must take precedence over public relations, for nature cannot be fooled."

Notice, that when the Rogers Commission made its findings known, it took the threat of withholding agreement to get his findings published. The bean counters fight like pit bulls to get dissent stifled...Sam

[Dairyground]

Any replacement battery needs to be capable of braking the airplane to a stop (under extreme weight and speed conditions, if they were honest in the specs).


They could redesign the brakes so that they are normally fully on and elictric power is only needed to hold them off. Some bird's feet work that way - by default they grip any twig the bird perches on and effort is needed to release the grip when they want to fly away. That way, the bird can sleep without falling off its perch.

[mm43]

That way, the bird can sleep without falling off its perch. Thanks for that!

Inverse logic at its best. Better to have a few heat plugs blow, rather than not stop at all.:ok:

[blackhand]

They could redesign the brakes so that they are normally fully on and elictric power is only needed to hold them off.Would there be an issue with "Fail -Safe"?

[PickyPerkins]

Any replacement battery needs to be capable of braking the airplane to a stop

When I was a lad I had a bike with electric lights powered by a dynamo driven by the wheels.

This generator was normally inactive, but at night it could be brought into contact with the tires and it then generated power for the head and tail lights.

Isn't it possible that for emergency use during the landing run of a 787 the wheels could supply adequate electric power for the brakes, even down to very low speeds?

Such a generator might be built into the wheels, or it could be a separate generator mechanically lowered onto contact with the tires in the same manner (kind of) as on my bike. A little bit like lowering a RAT into the airstream.

In short, a battery is not the only way to power brakes in an emergency, and an alternative source might be more reliable (the power source is always there) without being a fire hazard.

[cockney steve]

@picky perkins

Currently,the technology being developed includes a motor inside LG wheel
the concept being "tugless pushback and taxiing" to save fuel.

motor-generators are alreadywell-proven technology on this aircraft and was in commercial use in the 1950's-60's Bond and Messerschmitt 3-wheelers both used SIBA DYNASTART.

What you're proposing is regenerative braking -using the energy to supply the power to apply the brakes to absorb the energy....won't work without a huge Capacitor or another s/b battery.
Much better to use an electro-mechanical system-say reversible servo-motor/leadscrew(worm) and nut arrangement which would leave the brake"pressure" at the point the energy gave out.
Nice idea but fundamentally flawed,i'm afraid.

[ColinBJ]

@CockneySteve

No, what PP proposes is quite feasible. This is an example of energy from braking where the power does not need to be stored even momentarily, but is tapped directly as required. As the wheels spin up within the first second of ground contact, enough power to work the brakes in smart antiskid mode becomes available. They'd need to be mechanically locked on before the ground speed drops to a really low value.

(Not a pilot, but have some knowledge of engineering physics.)

[cockney steve]

@ romulus Fix it or Replace it.
Interesting consumer attitude!- so you consider it quite normal to buy a "rigorously" tested developed and certified bit of kit and then be expected to shell out cuntinuously on a component that doesn't make even 10% of it's anticipated life and then have to put your massive,costly investment on hold indefinitely.

To think Ralph Nader risked all to protect "mugs" with that outlook!

His book "unsafe at any speed" should be compulsory reading.
Bean counters decided that releasing a defective product would be more cost-effective after paying victim "hush-money" than the ethical and moral way forward, to engineer a safe product.

Areal sense of Deja Vu , here, Sir,It has nothing to do with HINDSIGHT.

A building burnt down during development....there was,IIRC, an on-board "event" during development. The technology's drawbacks are well -known among mainstream users...Boeing/Thates?planesecure between them managed to gain (self) certification on a system which doesn't work.
the 50 currently laid-up are very expensive"field-trial guinea-pigs"

There was a distinct lack of forward-planning by Boeing "suits" for a fallback -position WHEN or if, they got caught with their pants down
As things stand, a lot of people' livelihoods are at stake because of this poor decision-making.

I've no doubt the technology CAN be made to work sucessfully and meet a (downgraded) performance spec'.

monitoring/charging/bus interfaces. that's the problem area.

the intrigueing question is WHY

[Speed of Sound]

They could redesign the brakes so that they are normally fully on and elictric power is only needed to hold them off. Some bird's feet work that way

As do pretty much all trucks. Lose air pressure and your breaks are locked on.

Not sure that having brakes' locked on' is a good failsafe. Just as hydraulic systems have an accumulator which will provide a set number of braking actions, surely the redundancy here would be to have an 'electrical accumulator' (known as a capacitor) to power the brake actuators when all else fails.

If the capacitor has any spare electrical capacity it could also run a redundant anti-lock system too. :-)

[119.4]

20 February 2013 13:17:51Boeing Co Said to have found a fix for 787 Dreamliner battery problem - financial press (update)- Fix involves increasing the amount of space between battery cells to prevent overheating. ***Note that on Feb 17th, there were reports that a short-term 787 fix could come this week. The short term solution mentioned comprised a heavy-duty titanium or steel containment box around the battery cells, high-pressure evacuation tubes that, in the event of a battery fire, would vent any gases directly to the outside of the jet. - Source TradeTheNews.com (http://www.tradethenews.com/)

[Fargoo]

Boeing close to fixing Dreamliner battery - source | Reuters (http://uk.reuters.com/article/2013/02/20/uk-boeing-dreamliner-battery-idUKBRE91J0BX20130220)

As above, seems an interim fix is close.

[EastMids]

Japan probe finds miswiring of 787 battery

Japan probe finds miswiring of Boeing 787 battery (http://www.usatoday.com/story/travel/flights/2013/02/20/japan-probe-finds-miswiring-of-boeing-787-battery/1932109/)

[AmericanFlyer]

Significant news from Japan: Japan probe finds miswiring of battery on Boeing 787 'Dreamliner' | Fox News (http://www.foxnews.com/world/2013/02/20/japan-probe-finds-miswiring-boeing-787-battery-on-ana-flight/?test=latestnews)

[Speed of Sound]

As above, seems an interim fix is close.

Or not, depending on whether you believe Boeing or JAL/ANA.

If Boeing are saying that they are now physically and thermally separating individual 'cells' as their 'interim fix', then I guess they have already been given the knock back by the FAA on the 'bigger, stronger blue box' idea.

[Self Loading Freight]

Both strands - the 'more space for better cooling' and 'miswiring' - create yet more questions. How can you go through design, testing, certification and operation without spotting an overheat problem in a lithium battery pack where heat is one of your number one enemies and demands the closest of attention? It's like designing a petrol tank and not bothering to make sure it's vapour-tight. Any basic design problem that is first spotted through its combustion products is more than a basic design problem.

As for miswiring - how many levels of test, inspection and approval did the packs go through?

I hope some competent entity is given the brief to shake the regulatory process as hard as possible and see what drops out. Who that might be, alas, I don't know. If the level of incompetence approaches criminality, and as pax in danger of incineration I'm sympathetic to that view, then I wouldn't be at all sad to see the forces of Laura Norder get their size thirteens through the door.

[Heathrow Harry]

well considering they got the wing /fuselage join wrong early on I guess we can't trust very much

[EEngr]

EastMids (http://www.pprune.org/members/46329-eastmids):

Japan probe finds miswiring of Boeing 787 battery (http://www.usatoday.com/story/travel/flights/2013/02/20/japan-probe-finds-miswiring-of-boeing-787-battery/1932109/)

If this is the case (and not a non-tech reporter's mis-stating the problem), its not a battery subsystem problem. Its a Boeing QA problem.

I was there back when the FAA came in following QA and configuration control problems with the 757, 737 and others. It wasn't a pretty sight. I hope Boeing didn't throw out the baby with the bathwater after all the work we put in rescuing Boeing's production certificate. One can find and fix a problem once and be forgiven. Make the same mistake again and people will start wondering if they are really up to the job. The whole self certification and production inspection might have to be revisited, with the solution being FAA inspectors on site signing off each plane.

[SLFandProud]

They could redesign the brakes so that they are normally fully on and elictric power is only needed to hold them off. Some bird's feet work that way - by default they grip any twig the bird perches on and effort is needed to release the grip when they want to fly away. That way, the bird can sleep without falling off its perch.
This is how the brakes on trains* have been designed for decades.

The brakes on every coach are held on (by springs, for example) and released by the action of a round-train circuit, in early days pneumatic/vacuum, these days electrical. The circuit needs to be complete - and everything else needs to be operating correctly - to release the brakes; if the train separates or something else goes wrong, or the power is cut, the brakes apply. Of course a million implausible runaway-train movies ignore this but that's to be expected ;-).

I'm not sure the fail safe function of this in aviation is entirely as clear cut (eg. if a plane were to land with the brakes stuck on would this cause the landing gear to shear off which may be worse than landing with brakes off - a genuine question, I don't know the answer), but the principle is well founded.




* very long trains - primarily freight - suffer from the problem that a braking 'signal' can take an awfully long time to propagate down the train pneumatically, so the train will 'bunch up' on braking and 'string out' on brake release, meaning careful driving skill is required to avoid damaging the train, but electronic signalling obviously eliminates this these days. I believe unbraked wagons were abandoned even for freight about a century ago, but for that reason I won't be surprised if someone can come up with a counterexample...

[stallspeed]

Boeing should solve the problem the was toy manufacturers do when marketing their products ... at the bottom fthe desxription, in the finest print , barely readable without a magnifier...

(Batteries not included, please order separetly) :}

[FlightPathOBN]

Dont forget, the battery changed to LiCo after the first aircraft were built...

[BARKINGMAD]

Was it a Toulouse mole who suggested and pushed the idea of using a glorified laptop battery, as an essential aircrft electrical supply, thereby wrecking Boeings shiny new creation?

Presumably he will be caught and well & truly waterboarded for his efforts.

Anyone know what happened to the carbonfibre delamination of the wing root and internal wingbox on the factory fatigue 787 specimen? Allegedly U-shaped chunks of titanium were grafted in to solve the problem at the wing root!

Maybe 787 is a step too far, stimulated by the radical things being done by the 'bus' makers?

The K I S S principle seems to have been forgotten in design of not only the dirty techie bits, but also of the widgets that the poor evolved Bonobo chimp in the flight deck has to monitor and understand. When the widgets malfunction, said Bonobo has eventually to diagnose and intervene to save the day.


We are seeing many recent accident reports showing the chimp is out of touch with the shiny X-Box360 kit and shows reluctance to throw it away, disconnect A/P & A/T and fly it like the early aircraft on which the chimp learned its trade.


I was horrified to learn that apparently the "bus" has 1 box of electronics to control both nosewheel steering and mainwheel brakes. Presumably done to save a few kilos, easily negated by the arrival of the passenger(s) nowhere near the <80 kilos allowed for in the loadsheet and who we pray will not be sitting beside us in steerage class!

Step forwards management and regulators and take a rollocking for your inaction/inability in addressing these problems!!

Were any old experienced line pilots invited take part in the design phase-a basic qualification for this task should be to have spent say 30+ years flying, submitting and reading Air Safety Reports as a line pilot/trainer. Such a Bonobo chimp will end up with a more cautious and seasoned approach to what's NEEDED by the pilot community, whilst still being aware of the commercial gains due to SOME of the geeks gadgets. :confused:

[TURIN]

Japan’s Transport Safety Board released a report that stated that the battery of the Dreamliner’s auxiliary power unit had been incorrectly connected to the main lithium-ion battery that overheated. It further stated that a protective value would have presented power from the APU from causing any damage.

The Transport Safety Board said in a report that the battery of the aircraft's auxiliary power unit was incorrectly connected to the main battery that overheated, although a protective valve would have prevented power from the APU from doing damage.

Something not right here. How the hell can the APU bat connect to the Main Bat?

That is serious miswiring. I don't buy it.:suspect:

[413X3]

Airbus should thank Boeing for being the guinea pig so they can now release the A350 with none of these big issues. (Even though apparently the A350 is seeing its own delays)

[Romulus]

Airbus should thank Boeing for being the guinea pig so they can now release the A350 with none of these big issues. (Even though apparently the A350 is seeing its own delays)

It's a long standing feature of the aviation industry, Comet being a classic example.

[Speed of Sound]

Something not right here. How the hell can the APU bat connect to the Main Bat?

I have now read two different versions of this story! :-(

One says that the APU was incorrectly connected to the main battery and the other says that the APU battery was incorrectly connected to the main battery.

[ATC Watcher]

In an interview given in the French newspaper " le monde "
Yesterday one LOT executive is quoted to have said that " based on his info the 787 will not be back in service before October " and LOT is "considering delaying the delivery of the remaining 6 they have on order "

October ? That is a 10 month grounding .

[ozaub]

Concorde was grounded for 16 months, so 10 for the 787 looks about right. Given the proven dangers of li-ion, the need to prove compliance with special certification conditions plus the need to cross ts and dot is. We shall see.

[Rocket2]

"Concorde was grounded for 16 months, so 10 for the 787 looks about right" True but Concorde was long out of production then, meanwhile Boeing are producing 10(+?) 787's per month - parking space must be getting a bit tight now. Assuming the return to flight is delayed that long I'd have thought they'll have to slow / stop production soon with all the added cost implications.

[phiggsbroadband]

Hi, the actual statement was...

It further stated that a protective value would have presented power from the APU from causing any damage.

I think this was incorrectly translated, and should read...

It further stated that a protective DIODE would have PREVENTED power from the APU from causing any damage.

[TSR2]

Yesterday one LOT executive is quoted to have said that " based on his info the 787 will not be back in service before October " and LOT is "considering delaying the delivery of the remaining 6 they have on order "


LOT announced a couple of weeks back that they were going to cancel all B787 flights until October. It may well be more connected to their current financial status than the actual time the aircraft will be grounded.

[Speed of Sound]

Assuming the return to flight is delayed that long I'd have thought they'll have to slow / stop production soon with all the added cost implications.

They would be very foolish to stop production.

These are firm orders and it is strictly cash on delivery. Running out of space is not an issue. The US is very big and space can be found. I'm sure FAA exemption can be gained to fly the new aircraft out to a temporary location without an APU battery. It may even pay Boeing/Thales to set up a remote facility at this location to install/rewire the approved new battery/charging system when it is finally certified.

SoS

[TSR2]

It may even pay Boeing/Thales to set up a remote facility at this location to install/rewire the approved new battery/charging system when it is finally certified.


I agree, that sounds like a sensible solution but the production line may have to be 'robbed' of a considerable number of suitably qualified personnel to carry out the modifications. Out-sourcing such sensitive work may not go down too well.

[Speed of Sound]

If it is simply wiring up a new battery, this could feasibly be done by Thales/Securaplane employees supervised by Boeing staff. A revised algorithm or software tweek would be done and tested by the manufacturers.

Where it gets tricky is if we end up with a major redesign, where other parts of the system can't be tested before leaving Everett or Charleston because of a large chunk of the EE system missing awaiting FAA approval. :-(

[HeadingSouth]

...is the fact that the Japanese Investigation Team found "this" fault of a wrongly connected part.

What exactly were the Boeing engineers doing the last few weeks ?

And quite frankly - a fire and heat proof box won't solve "this" problem then, will it ?

So either there are multiple errors in the system or the fault-finding process may be flawed. Either or it's not helping the confidence in the plane or its engineers...

[TURIN]

Barking mad.
Why were you "horrified" to learn of the Airbus' BSCU? It has two independent channels. I'm pretty sure one can be inoperable on MEL. The backup brakes are sufficiently independent to allow it, steering likewise. BSCU. Works well, lasts a long time.

Back to the 787...
I think there is too much lost in translation with that Japanese report.
1. The main bat DOES have a "valve" or diode. So what do they mean.
2. The APU bat supplies the nav lights when the tow switch is selected. Under normal circumstances they are powered from a DC Bus. (I think, no schematics handy so I could be wrong.)

Miswiring or dodgy switch/breakers/contactors?

[Momoe]

Romulus,

It's a long standing feature of the aviation industry, Comet being a classic example.

Since when did the aviation industry have sole rights on learning from other folks errors?

The Titanic sank, shortly thereafter, passenger ships sailed with sufficient lifeboats for ALL on board.

At the end of the day, it's progress - thankfully no-one died this time.

[EEngr]

HeadingSouth (http://www.pprune.org/members/183943-headingsouth)

What worries me most is the fact that the Japanese Investigation Team found "this" fault of a wrongly connected part.It's improbable that this particular miswiring lead to the battery failures experienced. What it does do is to extend the scope of the investigation beyond the components and subsystems. Where there's one manufacturing or configuration control error, there may be more. And with this evidence, investigators can take a closer look at QA processes that may have contributed to the subject failure.

What exactly were the Boeing engineers doing the last few weeks ?Good question. Perhaps armed with this finding, the FAA and JTSB can now go in and find out.

[slamer.]

Boeing temporary battery fix tipped for Dreamliner

5:30 AM Friday Feb 22, 2013


http://media.nzherald.co.nz/webcontent/image/jpg/20138/SCCZEN_AP130125111440_220x147.jpg Expand (http://www.nzherald.co.nz/business/news/article.cfm?c_id=3&objectid=10866939#)

Boeing has developed a plan that it intends to propose to federal regulators to temporarily fix problems with the 787 Dreamliner's batteries that have kept the planes on the ground for more than a month, a congressional official said yesterday. Boeing Commercial Airplanes chief executive Ray Conner is expected to present the plan to Michael Huerta, head of the Federal Aviation Administration, tomorrow, the official said.
Marc Birtel of Boeing said it wouldn't talk in advance about meetings with federal officials. "Everyone is working to get to the answer as quickly as possible, and good progress is being made."
The FAA and overseas aviation authorities grounded all 50 of the planes flying worldwide after a lithium ion battery caught fire on a plane in Boston and a smoking battery led to an emergency landing by one in Japan.
The 787 is Boeing's newest and most advanced plane. It was meant to exemplify the future of commercial aviation, but the groundings have been a public black eye and financial drain for Boeing, which vies with Airbus for the spot as the world's largest commercial aircraft maker.

The plane is also the first airliner to make extensive use of lithium ion batteries to help power its electrical systems.
Lithium ion batteries weigh less, charge faster and hold more energy than other batteries of comparable size. But they are also more susceptible to short-circuiting that can cause fires if they are damaged, have manufacturing flaws, are exposed to too much heat or are overcharged.
The National Transportation Safety Board is investigating the battery fire in a Japan Airlines 787 discovered shortly after the plane landed at Boston's Logan International Airport last month.
Japanese authorities are investigating a battery failure in an All Nippon Airways 787 that made an emergency landing nine days after the fire.
Investigators have said the batteries experienced short-circuiting and thermal runaway, a chemical reaction that causes progressively hotter temperatures, but they haven't found the root cause of the incidents.
Japan's Transport Ministry says its investigation has exposed a new problem - the aircraft's auxiliary power unit, which contains a lithium ion battery, was improperly connected to the main battery that overheated.
NTSB investigators found the Boston fire started with multiple short-circuits in one of the battery's eight cells. That created a thermal runaway, which spread the short-circuiting to the rest of the cells and caused the fire.
The board's findings are at odds with Boeing's initial battery testing before FAA's safety certification of the plane, which found any short-circuiting could be contained within a single cell, preventing thermal runaway and fire from spreading.

Among the measures being discussed to make the batteries safe enough to return the 787 to the skies are adding more ceramic spacers between battery cells to contain any short-circuiting and fire within that cell. That would be in line with Boeing's initial test results.
More ceramic spacers would make the battery larger, which would require a bigger box to contain the battery cells. A more robust box lined with material to prevent any fire from spreading is also under discussion.
"What Boeing is trying to do is fix the battery so [its initial testing] assumption is now valid," said Jon Hansman, a Massachusetts Institute of Technology aeronautics professor and one of the FAA's Research and Development Advisory Committee.
"So if you can fix this part, the rest should be okay," he said.
Imperial Capital analyst Ken Herbert said last week the grounding could cost Boeing US$25 million ($29.95 million) a month in direct costs, with the total cost exceeding US$1 billion, including spending to fix it and expenses for delayed deliveries.
Boeing is still building five 787s each month, and has said it still wants to double that by the end of the year. It had orders for 800 before they were grounded.
It would take more than two months for Boeing to back away from its speed-up plan, UBS analyst David Strauss said.
Eight airlines in seven countries have 787s in their fleets.
Air New Zealand has 10 787-9s due for delivery next year.The grounding has been the most disruptive for Japan's All Nippon Airways, which has 17 of the planes.

[PickyPerkins]

Thank you for your response to Post 913 on alternatives to batteries for powering electric brakes. I found it quite refreshing to have at least one person read and understand the concept suggested, and then go on to defend the idea.

As far as I have been able to find out the electric motors mentioned by cockney steve to be used in the nose wheels of Boeing 737s (for tugless pushback) are induction motors and are not engaged with the wheels on landing, so considerable modifcation would be needed to use such motors for power generation during landing.

The system weight of 300 lbs has already been accepted by Boeing because less fuel has to carried for taxi, and for other cost savings.

[Romulus]

Romulus,

It's a long standing feature of the aviation industry, Comet being a classic example.

Since when did the aviation industry have sole rights on learning from other folks errors?

The Titanic sank, shortly thereafter, passenger ships sailed with sufficient lifeboats for ALL on board.

At the end of the day, it's progress - thankfully no-one died this time.

That was my point. The original post referred specifically to Airbus thanking Boeing hence the aviation context of the Comet.

And yes, thankfully nobody has died. Hopefully we get a resolution relatively soon, the world needs a strong Boeing and a strong Airbus.

[pgarner528]

So, if I have understood this correctly, Boeing are going to basically say "The batteries are going to spontaneously catch fire, but its OK because we can put them in a box".

Here is a test for you Boeing engineers and execs - build your boxes, install them into a couple of 787's, then load yourselves, your wives / husbands, your children and grandchildren. Take the planes up to normal cruising altitude, deliberately set fire to one (or both) of the batteries and then carry on flying for the rated ETOPS time.

If you survive, do it again. And then again and again. Keep doing it until you have come up with a proper solution.

Oh, and if the FAA approve it, load all the FAA execs & their families in there too.

[Momoe]

Seems a little clearer to me now.

Boeing's initial tests concluded that a single cell overheat wouldn't propagate to the rest of the battery, that's obviously not the case as it's been determined that cell # 6 had a fault which took out the whole battery.

Adding ceramic spacers to give more separation to cells sounds like a plan, however prevention is better than cure and better QC/specification on the cells before they get installed would be good.
Even then, the MTBF on any cell should be at least an order of magnitude higher.

One thing, I don't get is how a standby/back-up battery is on what appears to be a common bus, if there's an electrical problem I'd want a clean, uncompromised power supply on a previously isolated bus.

[Volume]

Taking into account that there are 8 cells, the MTBF of the battery is already almost an order of magnitude lower than that for any cell...
If we are sooner or later flying around with 20 times the number of dreamliners, the MTBF should be increased by at least a factor of 100. That would still give us around one burning battery per year, possibly 3 hours away from the next airport.

[Heathrow Harry]

I can see some customer resistance here -passengers don't like the idea of being burnt alive..................

[Tu.114]

For some reasons, I have to think of the old steam ships when reading this proposal. A century ago, a smouldering fire in the coal bunkers was considered no cause for concern. It was deemed sufficient to just use up the coal from the affected bunker first, and until then the fire was considered well contained within the ships structure. For example, the Titanic seems to have sailed under such circumstances. (http://en.wikipedia.org/wiki/RMS_Titanic_alternative_theories#Coal_fire)

Should technology really have progressed so little in the last century?

[HeadingSouth]

EEngr, thanks for your explanation; I'll go back to my study room and try to get a better understanding...

[Momoe]

Airbus have stated (Very publicly) that they are reverting to NiCd on the A350, general perception appears to be that Lithium batteries and aircraft are a bad combination.

With the 787 production line still going, this suggests that whatever the solution is, it will be constrained by having to fit within the existing battery bay.

Not sure that I wouldn't have preferred a blue-sky solution where ultimate safety was the only constraint.

[Autogeorge]

Taking into account that there are 8 cells, the MTBF of the battery is already almost an order of magnitude lower than that for any cell...


Surely the cells are in series; if one fails the whole battery has failed. Even if by chance it failed with zero resistance, the battery will no longer meet its voltage specification.

[LNIDA]

Given that sooner or later this problem will be resolved, its interesting to consider the impact on airline who are/were due to take delivery for this summers program here in Europe, there does not appear to be a lot of long haul capacity to lease in right now or the crews to fly parked desert ships?

Many airline will have been planning crew recruitment and training based on the now defunct delivery schedules, lots of gardening leave i suspect.

[AmericanFlyer]

Japan identifies spate of Boeing 787 jet problems | Fox News (http://www.foxnews.com/world/2013/02/22/japan-identifies-spate-boeing-787-jet-problems-but-still-investigating/?test=latestnews)

[EEngr]

pgarner528 (http://www.pprune.org/members/224340-pgarner528)

and then carry on flying for the rated ETOPS time.The problem is; these battery failures (fire or not) don't directly affect ETOPS range. The batteries are either there or not when they are needed. Their failure probability per flight may depend on the duration of that flight. Or the failure mechanism could turn out to be cycle rather than time dependent. One 'bad' charge or discharge event could initiate the fault.

That we don't understand the mechanism in play means that the probability math needed to ensure extremely unlikely events will be difficult. And involve quite a bit of Boeing/FAA hand-waving.

[TURIN]

One thing, I don't get is how a standby/back-up battery is on what appears to be a common bus, if there's an electrical problem I'd want a clean, uncompromised power supply on a previously isolated bus.

It's not on a common bus.

[poorjohn]

EEngr: The problem is; these battery failures (fire or not) don't directly affect ETOPS range. The batteries are either there or not when they are needed.When is either battery essential?

Loss of both engines has to be "impossible" for ETOPS; is it not equally "impossible" that power from at least one generator [on one remaining engine] will not be available?

Failing that, can the APU and RAT individually supply essential power for the ETOPS period? Can the RAT be deployed at cruise? At what airspeed does the RAT become useless? - that would seem to be the moment you need a battery. Too bad Boeing's math showed it was a waste of money to add a redundancy path between the two identical batteries.


It's amusing that the Boeing CEO and the head of FAA are solving the problem. IIRC the FAA grounding order directed that Boeing engineers satisfy their Renton-area office.

It will be even more amusing (though unlikely) if another jurisdiction took a less political view of the matter. Japan probably has similar commercial pressures given that their airlines are heavily invested, but the EU might have different ideas.

[pgarner528]

EEngr - its not a case of flying without batteries for the ETOPS time, its more the worry of flying round with a battery on fire / that has been on fire while 180 minutes from the nearest airport.

[deptrai]

In reply to MWorth, #964

"Boeing proposed a ten-point package that includes installing a fireproof container around the aircraft’s lithium-ion batteries, new venting system for fumes, and changes in the cockpit checklist. Boeing also said it plans to develop a new battery design that will measure the temperature and any voltage changes in individual cells."

without further explanations from Boeing, to me this sounds less like solving the problem, and more like they are preparing for test flights: trying to mitigate and contain damage with a new fireproof container, more spacing and venting, and at the same time gather more data by installing more sensors.

afaik the root cause is still unknown. yet Boeing claims this is "not an interim fix but a permanent fix". I hope some more information is forthcoming.

[EEngr]

poorjohn (http://www.pprune.org/members/213939-poorjohn)

When is either battery essential?If its not, the obvious fix would be to eliminate the batteries. Just require ground power to fuel/maintain/start the aircraft.

[poorjohn]

...the obvious fix would be to eliminate the batteries. Just require ground power to fuel/maintain/start the aircraft.
Standing behind my usual claim of ignorance, I'd guess that NiCd would be fine in the APU-battery role, and it's lithium just to keep the LRU count down. The real requirements for the two batteries must be hugely different.

Any bets on who'll win the showdown between DOT and Boeing?

[syseng68k]

deptrai:

afaik the root cause is still unknown. yet Boeing claims this is "not an interim fix but a permanent fix". I hope some more information is forthcoming.
Part of it seems more likely to be to fix fundamental flaws in the original design of
the battery subsystem.

If more modern technology with a higher than average risk factor is to be used, then
you need to go further than the usual due diligence and if anything,
over-engineer until enough in service experience is gained.

I'm sure they will make it work with LI batteries, as it is proven technology in other
areas...

[poorjohn]

Syseng68K: I'm sure they will make it work with LI batteries, as it is proven technology in other
areas... Adding ~100 lbs* of 1/2"-thick stainless steel fireproof case (as reported by sources not permitted to report such things) plus miscellaneous paraphenalia to permit the occasional battery to "safely" self-destruct sounds more like saving face and short-term shareholder value than good engineering. *[per battery, guestimating 12"x12"x12" case, stainless steel nominally 4.7 oz/cu-in]

[toffeez]

"A special announcement for the passenger in seat 30H: there has been a battery explosion under the floor near you and there is no extinguishing system installed.
However there is no cause for alarm as the battery is in a heavy steel box. If you start to feel hot please contact a cabin attendant.
Our estimated flying time to the emergency alternate airport is three hours."

ARE THEY KIDDING?
.

[Heathrow Harry]

exactly - who is going to fly on one of these planes when the cause of the problem is unknown but they are willing to ltake the risk of further fires?

Are they planning to actually carry out test flights where they set fire to the batteries in their "fire proof box" and see what happens???

[Romulus]

exactly - who is going to fly on one of these planes when the cause of the problem is unknown but they are willing to ltake the risk of further fires?

Are they planning to actually carry out test flights where they set fire to the batteries in their "fire proof box" and see what happens???

Somehow I suspect this one will remain a rumour, surely there is no way anyone will certify an aircraft to fly on the basis that a known fire hazard in an emergency power system is safely encased in metal...

[SMT Member]

Seems to me that, given the lack of a root cause and Boeing being in a rush to get the aircraft back flying, the proposal submitted utterly fails to address the real problem and is focusing on containment only. In other words, they're not going to fix the root cause.

Don't know about you, but that doesn't wash with me, and I hope the FAA will tell them to bugger off back to the drawing board and design a battery system that's no more liable to combustion then NiCad's.

[toffeez]

"As a result of this extensive use of a new construction material,
the fuselage cannot be assumed to have the fire resistance previously
afforded by aluminum during the in-flight fire scenario mentioned
above. These special conditions require that the 787 provide the same
level of in-flight survivability as a conventional aluminum fuselage
airplane."

"We agree that the heat transfer characteristics of
aluminum influence its response to an in-flight fire, and that a
composite structure will doubtless behave differently. The goal of
these special conditions is to enable continued safe flight and landing
in the event of an in-flight fire that directly impinges on the
fuselage structure."

I bet nobody was then considering the effect of a red hot steel box transmitting heat to the composite structure for up to 180 minutes.
.

[green granite]

The question is of course, would you pilots be prepared to fly it with Boeing's 'fix'? I would avoid it as a passenger, as I did the DC10.

[Ex Cargo Clown]

Can't just be a weight problem, if you can stick it in a Ti box you can put a NiCd in. More than this than meets the eye, must be a load issue.

Whose going to fly on an aircraft which may or may not potentially be on fire?

[HalloweenJack]

Can i ask a question regarding stuffing these things into a box? Will it be covered completely minimising the fire risk? And if what i`ve read on here is true , if thats the case ; surely the self sustaining properties would in fact make a fire hotter in an enclosed space? Thus giving it an increased risk?

[Machinbird]

Can't just be a weight problem, if you can stick it in a Ti box you can put a NiCd in. More than this than meets the eye, must be a load issue.
You do know that Ti can burn under sufficiently intense conditions?

Whose going to fly on an aircraft which may or may not potentially be on fire? The fact that a battery is locked inside a box is just part of the design change proposed.

The heat energy is not bottled in the box heating it to some gosh awful temperature, it is vented to the outside of the aircraft thus limiting the heat buildup inside the aircraft. From an engineering standpoint, complete battery runaway is a containable event. You folks fly with your engines on fire (internally) all the time, and the only time you get excited is when the fire unexpectedly goes out.:}

Give the engineers a little bit of credit for being able to mitigate a problem when their attention is focused on it.

[syseng68k]

green granite:

I'm sure it will be a great aircraft, and I would fly in it, but with the proviso that if
Boeing are starting to go the way of companies like Microsoft, where the last
stage of development is done by the punters, I would wait a few years and at least
service pack 3 before getting on board.

Never pays to be an early adopter, let them shake all the bugs out first :}...

[Momoe]

Give the engineers a little bit of credit for being able to mitigate a problem when their attention is focused on it.

I have issues with that statement at many levels:

First, are these the same engineers who designed the Lithium-Ion battery system (and oversaw the whole design/implementation/testing process) in the first place?

Two, definition of mitigate is to "Make less severe". Any fire (other than the engines), is a no-no on any aircraft, period. I'm not interested in a fire being made less severe, I am however very interested in not having it happen in the first place.

Three, if building an incinerator box for the batteries, albeit a vented one is what these engineers come up with when their attention is focused, I for one am not impressed.

IMO, this is a patch, it's the quickest means possible of getting the planes flying again - beancounter engineering.

[Smilin_Ed]

The question is of course, would you pilots be prepared to fly it with Boeing's 'fix'? I would avoid it as a passenger, as I did the DC10.

This pilot will not get in a 787 until they completely change the battery chemistry.:=

[toffeez]

This should not be a consideration for Boeing, but ... it would be somewhat embarassing if Airbus gets the A350 in the air when the 787 is still grounded.
That gives them about four months.

[EEngr]

Momoe (http://www.pprune.org/members/231371-momoe)

First, are these the same engineers who designed the Lithium-Ion battery system (and oversaw the whole design/implementation/testing process) in the first place?No, and yes (more or less).

The design and manufacturing of the various components of the battery systems were outsourced. So the "put it in a fireproof box" fix is Boeing's way of mitigating someone else's design error.

Three, if building an incinerator box for the batteries, albeit a vented one is what these engineers come up with when their attention is focused, I for one am not impressed. I'm impressed by the fact that the few remaining engineers at Boeing haven't just jumped ship and gone to work for the local power company. With management breathing down their necks and a decade or so of neglect for properly staffed and funded design, testing and analysis capabilities in house, this is about what I'd expect.

I'm just waiting to see if the firebox solution, once signed off by the FAA, doesn't become the long term fix. Following management pulling the budget for solving this problem.

I'm waiting to hear what the final root cause and solution will be. But I'm afraid we may never know. Because no one will continue looking. If they did, the next step would be to retrofit a fix to the fleet. This means millions of dollars more in parts, labor and aircraft down time. The alternative is to fund some poor slob poking around in the lab. With "no solution yet" as an answer.

[Momoe]

Outsourced or not, the buck stops with Boeing.

This is a tough challenge for Boeing, the outsourcing model failed, a lot of folk are looking to Boeing to come up with an elegant, engineered solution that is a rubber-stamp job for the FAA; The current proposal is a crock.

Don't do this - No-one wants one manufacturer to have the monopoly on large passenger aircraft, cons outweigh the pro's.

[WilyB]

I bet nobody was then considering the effect of a red hot steel box transmitting heat to the composite structure for up to 180 minutes.

Or venting heat and flames outside while they are refueling the 787. :ugh:

[WanganuiLad]

"....I bet nobody was then considering the effect of a red hot steel box transmitting heat to the composite structure for up to 180 minutes...."

Maybe they could run a wetback from it to the galley califont
Earn carbon credits

[Spooky 2]

Take it for what it's worth and don't know the original intened audiance.

International Video Player (resizable) (http://video.boeing.com/services/player/bcpid1809231507001?bckey=AQ~~%2cAAAAukPAlqE~%2coAVq1qtdRjxyl cCzuT_XWVzsvEb7ws7a&bctid=2168040449001)

[Mk 1]

WilyB, You cannot be serious asking this question:

Or venting heat and flames outside while they are refueling the 787.

if you knew there was an under bonnet fire in your car as you pulled into the service station, would you attempt to refuel your car?

Give airline staff and airport refuellers a little credit for intelligence.

Besides the presence of a stack of big lime green fire units would probably mean that even the most stupid refueller probably couldn't get close enough anyway.:E

Wily - you seem to misunderstand the situation here. The 787 after receiving this mod will not be flying around the skies totally oblivious to the little lithium furnace burning merrily away trailing smoke like an old 707 over a period of months. In the rare even of this happening again BEFORE a more permanent fix is found, the box and venting are designed to mitigate collateral damage whilst the crew seek out the nearest safe airport so the emergency services can extinguish the blaze.

[Ex Cargo Clown]

You do know that Ti can burn under sufficiently intense conditions?
I'm more than aware of that most will get a bit"flimsy" at around 420 degrees. What's worse though is the alloys have lovely stuff like molybdenum in them, which I wouldn't be sprinkling on my cornflakes.

[syseng68k]

Melting point of Titanium is around 1700 C, not that much different from Stainless
Steel and it would probably take much more to make it burn, though no metallurgist.

Fwir, steel heated to 1000 C looks almost white hot...

[Ex Cargo Clown]

Deforms at 420 degrees, trust me.

[inetdog]

Standing behind my usual claim of ignorance, I'd guess that NiCd would be fine in the APU-battery role, and it's lithium just to keep the LRU count down. The real requirements for the two batteries must be hugely different.
The official explanation is that the Li battery can deliver enough power for several starts of the APU and then be quickly recharged again once the APU or other power source is running. NiCd's higher internal resistance makes very rapid recharging more problematic.
Using the same battery for both purposes is a little harder to justify, but in terms of design, testing and acceptance seems plausible.

[Ex Cargo Clown]

Plausible? are you mad?

[poorjohn]

inetdog: The official explanation is that the Li battery can deliver enough power for several starts of the APU and then be quickly recharged again once the APU or other power source is running. NiCd's higher internal resistance makes very rapid recharging more problematic.I've been poking around trying to learn which of those "facts" about various batteries are true, without much luck. The wikipedia article is not very satisfying, and I don't know the merits of this page Lithium-based Batteries Information (http://batteryuniversity.com/learn/article/lithium_based_batteries). The table would have you believe that LiCobalt is a very poor performer compared to later Li technology. It would be interesting to know Boeing's supplier's reason for that choice.

On the different topic of catching the fuselage on fire, early on I posted a link to a 2007 paper produced by U of Maryland (iirc) for the FAA which showed that Boeing's composite fuselage recipe was well-behaved in that regard. Perhaps someone has revisited that effort, given the embarassment with battery engineering.

[WHBM]

All Nippon cancels the 787 from the next three months of schedules

BBC News - Dreamliner: Japan's ANA cancels more Boeing 787 flights (http://www.bbc.co.uk/news/business-21571545)

Given that Boeing seems about to announce they've "fixed it", this is interesting timing for such an announcement. Is someone in Japan sending a message ?

[Annex14]

I´d rather like to say that the Japanese have kept their sense of responsibility.
It appears more and more to show that some people at Boeing gambled with high stakes, observed in patience by the certification administration.
The socalled"final fix" - as it it is known untill now- is nothing but a continuation of endanger the lifes of innocent passengers and crews.
Hope that strange behavior comes soon and finally to a screeming end.

[toffeez]

I still can't believe that Boeing, once top dog, can be that stupid.

They have been handed enormous good luck: they did not have to drag the debris of ANA flight 692 out of Japan's Inland Sea.

Their CEO will earn his salary if he insists that a durable safe fix be found because one fire-related fatal accident could kill the program.
.

[Heathrow Harry]

not kill the program - it would kill the Company

[WHBM]

Their CEO will earn his salary if he insists that a durable safe fix be found .......
Have any Boeing CEOs had that technical understanding and wisdom since the days of Phil Condit ?

[ATC Watcher]

Sad.
For me, and I guess for the average educated pax , any "temporary" solution that does not eliminate the fire possibilities in that aircraft will not be acceptable.
Fire in a traditional aircraft is already a major issue, but any form of fire anywhere in a composite aircraft will get me even more worried.
I have seen a video of a composite ( small ) aircraft burn , it is not a pretty sight. The speed of propagation is impressive ,but the smoke, not the fire is the most deadly part.
As we sadly learned in the Dusseldorf airport fire a few years back, some composite fumes can kill you in just one breath . The bodies were intact.
In other words, even with a small contained fire ,the structure might survive, but not the pax .

[Joetom]

A great thread indeed.

Even if a short term fix/containment of problem battery can be agreed with Boeing and the FAA, many or most airlines may not elect to fly the 787 in this state.

Just too many issues to deal with using the short term fix/containment, if a battery fails in flight it will not be available to do the things it was put there for so could make many diversions and much more press coverage etc etc etc !!!

Talk of 100/150 787 batts have been replaced up to this point and the recent events in the press, plus any other events that may not be in the public domain, if the 787 goes back in service without the root cause fixed and has any more serious events with paying passengers on board, history may show it would of been better and cheaper for the 787 to spend longer grounded.

My guess with so much info coming out about how Boeing and the FAA got the 787 certified in the first place, the "A350 plan B" type deal will be the one that gets the 787 back in service.

The cost to the 787 project will be a monster, but as previous posters have mentioned, it could of been much worse.

Good luck to the Engineers trying to understand and fixing the issues.

[cockney steve]

@Volume... there are NOT 8 CELLS there are 24!

each "cell"is 3 sub-cells in parallell. These could easily be connected together by attaching each sub-cell to it's main cell-buses with appropriately low-melting point fusible straps....thus any individual cell that went defunct would not compromise the output voltage of the battery-unit.- it would, however, limit current-drawboth safe continuous and peak.

@ Machinbird...As already said by Momo....you can't credit engineers who merely make a gigantic Kludge to sidestep a fundamental problem.

@ Wiley B... they'll probably point the vent-pipes aft and sell it as "emergency auxiliary thrust":}


@ Inetdog.."several starts" NO!!!! there has to be a half-hour cooling-period between APU runs, therefore one start and it recharges it's battery before shutting down. ('cos the batteries charge real quick(when they're not locked out because the start took the voltage too low :* )

SEVERAL ATTEMPTED STARTS may be a different issue and one would question the Captain's decision to go with a dodgy APU.


I suggested Ceramic insulation a long while ago. the general concensus is that wound cylindrical cells are more robust. ceramic pota with screw-on ceramic lids could contain each sub-cell and individual cell temp and voltage-monitors the main cell-casing , similar construction. tails from sub-cells in suitable low melting alloy.

whole battery would thus maintain it's integrity and fulfill an emergency power role until all 3 individual sib-cells in a cell-pack had disconnected themselves, thus open-circuiting the whole battery..

Oh, Wait!! we" only" have 16,000 USD per battery , to play with...thermistors are HOW MUCH? Microchips /CPU's are HOW MUCH....Memory -HOW MUCH

And 48 ceramic pots per aircraft....well, it'd cost MEGABUCKS to make a few thousand a year, 'cos they'd be very special ceramic, dontcha know :p

[WHBM]

It does look like the two major Japanese users of the 787 have ganged up on Boeing this last weekend. In addition to the All Nippon statement, the chairman of Japan Air Lines made an interview with CNN on the same day which really puts the knife in to their longstanding relationship with Boeing. Interesting to view the video.

JAL Chairman: 100% Reliance on Boeing 'Abnormal' (http://www.cnbc.com/id/100488815)

[Ex Cargo Clown]

Surely the only way you can certify "The Box" is to push the batteries to failure and prove no damage?

[deptrai]

annex14,

the Japanese have kept their sense of responsibility

I agree. ANA and JAL were the first to (independently) ground their fleet of 787, before the FAA or Boeing took any initiative. ANA doesn't yet seem convinced by Boeings "quick fix". And now JAL chairman Kazuo Inamori stated "We should have been much, much more careful. The only consolation is that there has been no grave accident".

Boeing definitely got one thing right with the 787 - their choice of launch customers. Maybe Boeing could even learn something from them. I believe the Japanese have done a lot to keep up the public's faith in aviation, and handled this unfortunate situation in a very professional way.

[Cool Guys]

Wow, it sure is easy to kick someone when they are on the ground. Sure, some people at Boeing have screwed up, but they are paying for it financially and with their reputation and fortunately not with lives. However there are many great things about this plane. I don’t have an issue with the battery box except it’s a little late. It should have been in place years ago. The issue is getting the battery fire rate down to that 1 in 10 million figure that was quoted earlier. It seems like Boeing are working on this, just the specifics have not been released.

I think we are seeing a natural progression here. The energy density of batteries has always been low compared with fossil fuels which is why we have never seen electric powered cars or planes to any degree. For the same reason there has never been any real danger from devices such as a lead acid or nicad batteries. Now fuel prices are rising there is more incentive for battery manufacturers to invest in battery technologies so we are seeing the energy densities increase. I suspect it won’t be too far in the future when we see the energy densities of batteries actually get higher than that of fossil fuels. Then we will see electric cars truly competing with their fossil fuel counterparts and we may even see electric powered jet engines, ie the fans are propelled by an electric motor rather than a turbine. I am sure there will be some serious containment issues in those batteries.

The Boeing guys are pushing the boundaries of technology, just like Airbus and many other companies have. The Concorde was sure pushing the boundaries, as was the AB FBW. Boeing have screwed up a little here but I suspect it will be a tempory setback. I am sure they will live another day to release some other new technology in the future and it wouldn’t surprise me if they make the same mistakes again.

[deptrai]

Wow, it sure is easy to kick someone when they are on the ground. If they were flying there would be no reason to kick them :}

Customers expected to buy aircraft that fly, and in the current situation, some barking at Boeing is to be expected. I don't see much drama in that, and I concur that this is just a temporary setback. Boeing has 890 firm orders, airlines love the promise of lower fuel burn, and in the long run, the 787 will deliver exactly that (just to clarify: when it flies).

[Momoe]

Boeing are taking a beating partly because the planes aren't flying for a damn good reason, the other issue is Boeing's perceived lack of clear oversight across the design/implementation.

Outsourcing isn't a bad thing, Airbus has various components made, shipped and assembled on site (And this isn't an Airbus v Boeing thing, I'm just comparing apples with apples).

This is Boeing's first attempt and I do accept that they did push the boundaries with the plane which to all intents and purposes is superb, however the battery issue is serious and Boeing's proposed fix is a patch, not the fix that most folk are looking for.

I might be wrong, but I don't believe that customer confidence will be fully restored until a proper fix is implemented.

Folk keep banging on about 890 firm orders, yes, but that was BEFORE the problem; ANA and JAL have been biding their time and have spoken out now, coincidence?
No-one is naive enough to believe that other carriers aren't considering their options.

[deptrai]

I just read this article from Chemical & Engineering News 2007: Burning Batteries | December 17, 2007 Issue - Vol. 85 Issue 51 | Chemical & Engineering News (http://cen.acs.org/articles/85/i51/Burning-Batteries.html)

probably nothing new to experts, but it confirms that it may be difficult to find a root cause for failures:

One fact that emerged is that it's tough to get solid statistics on the number of lithium-ion batteries that apparently explode or catch fire without having been set off by abusive actions. Unprovoked battery explosions are known as "field failures," and industry experts say such events are rare. They estimate that between one in 1 million and one in 10 million lithium-ion batteries fail that way.

Not only are the statistics of field failures difficult to pin down, but the fundamental mechanisms that trigger the hazardous events are also challenging to elucidate. For one thing, field failures are difficult to reproduce and study in a lab because they happen so infrequently.

Another difficulty in analyzing the causes of spontaneous failures is that batteries that fail in the field come from lots that have already passed abuse and reliability tests, and they appear to have worked normally for a while. Those batteries simply don't give researchers a clue that trouble is brewing inside of them. Furthermore, when one of them catches fire or explodes, not enough battery material may be left behind to determine what went wrong.

[Heathrow Harry]

"It does look like the two major Japanese users of the 787 have ganged up on Boeing this last weekend."

ganged up?? They've invested hundred of of million dollars in something they have to park and may not get to use - I think they have a right to say something

and Boeing should count themselves lucky - if it had been Ryanair or Mr Al Baker at Qatar A/w the airwaves would be really humming

[ImageGear]

In my experience of teaching Japanese Engineers in the USA many years ago, and then working with them to design large vector/scalar computer systems, I was very, very impressed by their commitment to provide the best possible product to their customers. The Japanese culture of what constitutes acceptable design and production risk was then infinitely more refined than anything contemplated by the U.S manufacturers.

Issues of this type, which appear to be relatively minor and therefore tolerable to an early launch customer in Europe or the West would be rejected out of hand as totally inappropriate for a Japanese customer. In the event of a failure of this magnitude, the loss of face and deep shame suffered by the most Senior Japanese Executives may ultimately result in a final but more honourable outcome.

So to find these serious electrical issues occurring in such a high profile and valuable product makes me wonder to what extent the Supplier's Japanese Engineering teams and the Customer's Engineering teams were able to authorise design and production acceptance without prejudice when even to a layman with a laptop the battery systems would have been subject to the most intense scrutiny.

Has the Japanese culture of perfection, performance, reliability and maintainability changed so much in recent years that this type of issue could be overlooked? This aside from the FAA's position which I associate more appropriately with the U.S's position on the acceptance of risk.

..and yes, we also accepted that when the pre-release version of the product went to Japan a significant amount of re-engineering could be necessary to bring it up to the Japanese specification and this was understood.

[toffeez]

Once upon a time a young version of me said in a meeting with Japanese that something we were proposing was "good enough".

I was swiftly told that for the Japanese it's either right or wrong. I never said it again.