Quoting rheinwaldner (Reply 37): Any other electrloyte would reduce the batteries capacity. So there would be structural changes anyway to make the battery accordingly larger.

It depends on the electrolyte. Lithium nickel manganese cobalt has high energy density and high energy output (like lithium cobalt oxide), so it might very well provide the same performance with the same cell dimensions as the current battery. Lithium iron phosphate, which has a lower energy density, has been reported to be able to provide the same performance with one additional cell.

There is no way the FAA will let the 787 fly with the current lithium ion battery system -- too much evidence that it is unreliable and unsafe -- this will mean a complete redesign and a minimum of 18 months on the ground. This is going to leave a mark.

Quoting NAV20 (Reply 23): Thanks for the replies, guys. But are those 'stabler' and 'safer' versions already in service and fully tested? Or will Boeing have to be the 'pioneer' again?

Cessna is testing, (and may already have certified), Lithium Iron Phosphate batteries for their CJ-4.

Quoting btfarrwm (Reply 26): If most of the problem with the Lithium Ion batteries has to do with improper charging and discharging, as the recent New York Times Article would suggest, how much of a design change would be required to make the batteries removable?

If you look at the famous Sony laptop failures, their runaways were caused by contamination, not improper charging. I understand the investigators have already ruled out improper charging in the 787 cases.

Quoting rheinwaldner (Reply 37): Any other electrloyte would reduce the batteries capacity. So there would be structural changes anyway to make the battery accordingly larger.

There are other Lithium battery chemistries which have been calculated to fit into the current 787 battery box.

Quoting Stitch (Reply 50): Lithium iron phosphate, which has a lower energy density, has been reported to be able to provide the same performance with one additional cell.

Quoting ServantLeader (Reply 51): There is no way the FAA will let the 787 fly with the current lithium ion battery system -- too much evidence that it is unreliable and unsafe -- this will mean a complete redesign and a minimum of 18 months on the ground. This is going to leave a mark.

The could if the faults were manufacturing flaws. Eliminate those and you eliminate the dangers. Couple that with more robust containment, and most issues would be resolved. The current containment was robust enough to contain enough of the residue and energy from the runaway batteries to prevent serious damage to the plane...a better system could surely be found for that.

Quoting ServantLeader (Reply 51): There is no way the FAA will let the 787 fly with the current lithium ion battery system ... this will mean a complete redesign and a minimum of 18 months on the ground.

Well, I'm glad THAT's settled.  

Just a moment of light humor to provide a brief interlude:



Given the FAA's reputation as a ''tombstone agency'' we should be lucky this problem was spotted and addressed as quickly as it was....

Quoting alberchico (Reply 55): Given the FAA's reputation as a ''tombstone agency'' we should be lucky this problem was spotted and addressed as quickly as it was....

The FAA is hardly the only regulatory body in the US, much less the world, with that kind of mentality.

Quoting tropical (Reply 8):

So far as we can tell from working the airplane, the electrical load on the airplane is actually pretty well in the normal range.
Lord KNOWS there's enough power on the airplane for the electrical load. The Bleed less engines are to preserve power in climb and cruise and to increase the fuel economy as there's nothing coming off the gas path of the engines that does NOT produce power out of the exhaust. the lack of Bleed related valves, inter stage, Press regulating, High Pressure, Nose cowl anti-icing, are the key to the range and at this point the 787 with Bleeds would be not much more than the 767 in Carbon Fiber. I'm looking for the engines to be on wing 65-75,000 Hours barring environmental damage.
Even if they can stay on 50-60,000 hours they will have nearly paid for themselves in efficiency.

Quoting rheinwaldner (Reply 47): But the principles of the Tesla battery should be valid for the dreamliner: - Reduce cell size. - Have a layout, where at least a bit better separation can be achieved.

Possibly the reason why Airbus is going with 4 batteries for the A350
On top of that I guess that total battery capacity is way smaller given the conventional architecture of the aircraft.

Semi-interesting article in the New Yorker.

http://www.newyorker.com/talk/financ...013/02/04/130204ta_talk_surowiecki

Quote: The Dreamliner was supposed to become famous for its revolutionary design. Instead, it’s become an object lesson in how not to build an airplane. To understand why, you need to go back to 1997, when Boeing merged with McDonnell Douglas. Technically, Boeing bought McDonnell Douglas. But, as Richard Aboulafia, a noted industry analyst with the Teal Group, told me, “McDonnell Douglas in effect acquired Boeing with Boeing’s money.” McDonnell Douglas executives became key players in the new company, and the McDonnell Douglas culture, averse to risk and obsessed with cost-cutting, weakened Boeing’s historical commitment to making big investments in new products.

Quote: “Some of the board of directors would rather have spent money on a walk-in humidor for shareholders than on a new plane,” Aboulafia says. So the Dreamliner’s advocates came up with a development strategy that was supposed to be cheaper and quicker than the traditional approach: outsourcing.

Quote: In 2011, Jim Albaugh, who took over the program in 2009, said, “We spent a lot more money in trying to recover than we ever would have spent if we’d tried to keep the key technologies closer to home.” And the missed deadlines created other issues. Determined to get the Dreamliners to customers quickly, Boeing built many of them while still waiting for the F.A.A. to certify the plane to fly; then it had to go back and retrofit the planes in line with the F.A.A.’s requirements.

Quoting strfyr51 (Reply 57): the lack of Bleed related valves, inter stage, Press regulating, High Pressure,

Not to mention that by getting rid of bleed air, you eliminate a significant fire hazard.

Quoting tdscanuck (Reply 48): I think the applicability would require the FAA to concede that the over-temperature of a *cell* was permissible as long as it didn't over-temp the battery, and that failure of a cell could not be considered failure of the battery.

I think that is the correct approach, because as you pointed out, the current regs may have been written with the current 787 in mind. With the new design, failures are tolerable to a certain percent of storage capacity, current delivery or voltage deviation. Within say, 5 %, should be good to go and enough to make it to the next airfield as a normal condition. Ideally, individual cells could be replaced, lowering maintenance costs and reducing necessary inventory at airfields.

Quoting SFORunner (Reply 59): Semi-interesting article in the New Yorker.

And it gets its very first paragraph wrong:

"Its braking, pressurization, and air-conditioning systems are run not by hydraulics but by electricity from lithium-ion batteries."

Quoting AeroWesty (Reply 62): And it gets its very first paragraph wrong

First rule of working in the aerospace industry: Never, ever listen to anything the mainstream media has to say about aerospace. Yeah, I trust the New Yorker on technical issues about as much as I trust Jim Albaugh on cuisine issues.

Quoting tdscanuck (Reply 45): If wisps of smoke are escaping, it's not a sealed case, hence doesn't build pressure, hence isn't explosive. We already had people yelling, at considerably length, that release of flammable gas was totally unacceptable and that's what the battery you describe was doing.

But if a small amount or smoke is all that is vented out, then it is going to be pretty easy to have a dedicated tube to vent it to the outside directly through the existing vents. There must be a lot more going on inside that case, so I'm guessing this is a pressure relief valve to limit how much pressure is contained inside.

Quoting rheinwaldner (Reply 37): see that the design is not good at the prevention of failure propagation between cells.

Quoting PW100 (Reply 2): BTW, apparently the Tesla BMS does have a sort of double threshold set-up, as I've not heard or read of any, let alone 100 - 150 of Tesla batteries,

But you can brick them. There are big warnings about not letting your Tesla get too discharged.
BTW - if you brick your tesla - it is not covered under warranty - and the cost to replace the battery is $40K, not the $12K here. That $12K is the pre-plan price you can pay toward replacement at the end. To be fair - not many Teslas have bricked. The new model S's have more aggressive brick control procedures - so it is less likely.

While Tesla is cool - let's stop making like they are the god's of batteries. Plenty of problems with Telsa's.

Too other things about Teslas
- Major driver in the battery choice was cost - these are standard 'off the shelf' batteries.
- Complexity and lower reliability - they are complex. Cells can die - and they allow the car to continue to run - because they know cells will die. How many cells would you allow to die on your 787 before you replaced them? Certification nightmare. What if a cell burned up - and you did such a good job isolating it - you just though it died. Is that 'fire' acceptable - well - depends on the containment.... Hmmmm

The point is - there are design trade-offs that must be made for any battery system. It is really easy to sit here in my office in Colorado and second guess the engineers designing it - but as an EE, I've been on the other side. too

Quoting 7BOEING7 (Reply 4): and if it's your nickel , it's $8-12K.

Quoting ComeAndGo (Reply 6): 8 - 12K vs 16K !! And warranted for 8 years !!

$40K if they brick - warrenty does not cover it.

Quoting tdscanuck (Reply 21): Doesn't that greatly increase the complexity off the BMS, an hence the probability of a BMS or cell failure?

Yes - Twins versus Quads. Which is more reliable (from the previous string). Twins....

Quoting packsonflight (Reply 58): Possibly the reason why Airbus is going with 4 batteries for the A350 On top of that I guess that total battery capacity is way smaller given the conventional architecture of the aircraft.

As was noted above, the evolutionary "architecture" of the airplane has nothing to do with the battery requirement.

Quoting tdscanuck (Reply 21): They're a huge factor in the amount of power the airplane requires. However, that has essentially nothing to do with the battery size or design.

Quoting tdscanuck (Reply 48): If that's really true, I can't see why they'd go for the giant-cell architecture, except maybe maximum power density.

Maybe because on paper the weight of the containment would turn out the lowest. A compact cube offers the largest volume per surface area. That means for a given volume of content, the weight of the shell would be minimized. So having more space between cells and another layout would require more steel (or whatever other material) for the containment.

That might be one argument for the current cramped layout. Possibly again a case of too much emphasis on weigth reduction.

Quoting cornutt (Reply 49): If you have 800 cells, you have a massively complex BMS with 800 sets of sensors, 800 signal conditioning circuits, and 800 relays so that individual cells can be taken off line.

- First the dreamliner would never need 800 cells. Between 8 and 800 there is wide range were a reasonable cellcount could end up. So maybe 160 would be fine (a so called 8s20p-battery).

- Second such a battery would not require 160 (temperature) sensors. The primary parameter to monitor and control is voltage. For temperature monitoring thermography in combination with digital image recognition would be a clever, cheap and 787-worthy solution. Also smoke and fire detection are possible for a larger area of cells.

- Third the signal conditioning would be very cheap technology in the whole context even with 160 cells.

- Fourth you don't need a single relay to cut off a cell. Have you seen the massive, fix steal connectors between the cells on the existing battery? There is no relay! So why would you need relays for the smaller cells if the current whopper-cells don't have one? Just to complete: electronic switches will do that job.

Here is a link where the challenges of large format cells are discussed for automotive applications:
http://www.lithiumbalance.com/automo...e/battery-management-in-automotive

Specifically safety is mentioned as the single biggest challenge with such batteries:
Safety is the single biggest challenge for large format Lithium Ion cells. Smaller cells such as the typical 18650 size cells can be equipped with built-in, passive, safety features. In advent of a mishap, a single cell with a capacity of 2.2AH (9Wh) is of manageable impact compared with a 50AH or even 400AH (1.6kWH) unit.

Quoting rheinwaldner (Reply 67): - First the dreamliner would never need 800 cells. Between 8 and 800 there is wide range were a reasonable cellcount could end up. So maybe 160 would be fine (a so called 8s20p-battery).

So if I understand the terminology, that's 8 "layers" of 20 parallel cells each.

Quoting rheinwaldner (Reply 67): - Second such a battery would not require 160 (temperature) sensors. The primary parameter to monitor and control is voltage. For temperature monitoring thermography in combination with digital image recognition would be a clever, cheap and 787-worthy solution. Also smoke and fire detection are possible for a larger area of cells.

The thermography would be a cool solution if it had been thought of about four years ago. There's no way in hell that software gets developed to DO-178C standards and certified in a few months, even with people working on it 24/7. As a long-range improvement it's worth looking at, but it isn't going to solve the immediate problem.

Quoting rheinwaldner (Reply 67): - Third the signal conditioning would be very cheap technology in the whole context even with 160 cells.

It's a reliability issue. Might be solvable; I haven't had occasion to look at A-spec parts for that sort of thing in a while, so parts with the necessary reliability numbers might be available now. Last time I looked they weren't, but that was years ago.

Quoting rheinwaldner (Reply 67): - Fourth you don't need a single relay to cut off a cell. Have you seen the massive, fix steal connectors between the cells on the existing battery? There is no relay! So why would you need relays for the smaller cells if the current whopper-cells don't have one? Just to complete: electronic switches will do that job.

The current battery has no cell cutouts because there is no point; with all of the cells in series, the battery can't achieve spec voltage with one cell bypassed. If a cell fails, it cuts out the whole battery (at least in theory). Presumably, with a multi-cell battery, we want to continue to operate with some number of cells failed so that we overcome the failure probability calculation with multiple cells. The problem that arises is: what if a cell shorts? If it does that, then even if the resulting event is fully contained to that cell, you've still got the problem of having a short across that layer. That will prevent other cells in the layer from charging and lower the overall battery voltage. (And no, I don't think you can just assume that the short will always burn itself out... carbon tracking and all that...)

So you need to be able to cut out individual cells, or small groups of cells, and once they are cut out you need for them to say cut out until the battery is serviced. Latching relays make a tidy solution for that; the BMS causes the relay to open, and then it stays open until reset via voltage applied to a test bus which the flight system has no connection to. If you do it with electronic devices, the BMS has to remember which ones to keep open, and it has to retain this information across power cycles. That's some more complexity; not a lot, but it's one more bit of software and complex hardware to certify. And the electronic devices themselves probably don't save space or weight vs. the latching relays, considering the amount of current they have to carry.

Look, there are some good ideas here. But it's not as simple as "oh pop this in, and the 787s will be flying again next week". And I'm particularly resenting the implication that the problem would be easily solvable, or could have been entirely avoided in the first place, except for Boeing engineers being stubborn and stupid. We've got some posts here simultaneously arguing that the certification criteria for the existing design should have been a lot more strict, and that they can bypass all those criteria with some magic bit of technology. There is no such thing as a zero-risk solution, and to argue otherwise is dishonest.

Rumor of a fix Boeing is considering.

"Sources say that Boeing is seriously considering a better containment system that solves both the collateral damage to other sensitive equipment and deals with the smoke better. The plan is to build a stronger and larger containment box or dome around the battery, and vent smoke and potential debris overboard through a hose or other channel. "

http://www.king5.com/news/aerospace/...87-battery-problems-189115821.html

Which seems to be in line with I what I have been seeing as a possible solution.

Just a rumor from "sources" though, at the moment.

Quoting RickNRoll (Reply 69): "Sources say that Boeing is seriously considering a better containment system that solves both the collateral damage to other sensitive equipment and deals with the smoke better. The plan is to build a stronger and larger containment box or dome around the battery, and vent smoke and potential debris overboard through a hose or other channel. "

Looks similar to the way the other company was making for Cessna. I believe the details of that company are in the previous thread.

Quoting rcair1 (Reply 65): Yes - Twins versus Quads. Which is more reliable (from the previous string). Twins....

unless of course you're virgin and that A330 hits a flock of vultures on take off in Orlando and both engines are out.

Quoting ComeAndGo (Reply 71): unless of course you're virgin and that A330 hits a flock of vultures on take off in Orlando and both engines are out.

And here was I thinking this was an aviation forum - virgins, vultures?

Quoting RickNRoll (Reply 69): Which seems to be in line with I what I have been seeing as a possible solution. Just a rumor from "sources" though, at the moment.

This story adds the point that the solution would probably be 'interim in nature.'

"The actual mechanics of this would of course be more complex, but the principle of containment and disposal of risk are straightforward, and possibly interim in nature if the unofficial reports are correct.

"The reports make more sense of the confidence Boeing management expressed for a prompt solution to the problem during an earnings conference call earlier this week."

http://blogs.crikey.com.au/planetalk...aks-a-fix-while-ana-seeks-damages/

Pretty obviously the only way Boeing (and the airlines) can hope to get the aircraft back in the air in the short term.

Quoting RickNRoll (Reply 69): Just a rumor from "sources" though, at the moment.

King5 is not the most respected news outlet...

I think we will be witnessing the 787 delay PR spin all over again. How many delays did Boeing officially announce on the 787 program? was it more than 10 or more than 20? In hindsight we see that the management at no time announced more than a fraction of the delay needed at each time.

Take for example the infamous Potemkin rollout of the 787. If the management did not realise the troubles the program was in at that time, they should not be trusted to run a hotdog stand, let alone the mighty Boeing company.

Quoting packsonflight (Reply 74): King5 is not the most respected news outlet...

They are in Seattle, so they likely have better access to Boeing personnel working on the issue than, say, The New Zealand Herald.

Quoting packsonflight (Reply 74): I think we will be witnessing the 787 delay PR spin all over again.

As Boeing will not be the one controlling return to service, I am not sure how they can "delay" it to the point they need to spin.

Quoting PW100 (Reply 52): Quoting tdscanuck (Reply 21): Why would you sacrifice the airframe to protect the battery? Because it is no different then a slightly lower capacity battery freezing up and sacrificing the same airframe because of the BMS protecting the battery against over-dis-charge

Yes, it's hugely different. You're talking about giving the battery the ability to shut down the airplane (that's "Threshold 1" in this scenario). That's what I mean by sacrificing the airplane to save the battery. The current battery can't shut the airplane down, it will continue to power it for as long as it can.

On it's face, the two threshold idea is uncertifiable because you've set up, by design, a single-point failure that will take down the airplane. If the Threshold 1 "nice shutdown" activates in flight you're going to die.

Quoting ServantLeader (Reply 51): this will mean a complete redesign and a minimum of 18 months on the ground.

How do you get 18 months? Boeing (with Thales and Hamilton-Sunstrand) managed to redesign, retrofit, test, and certify a hugely more complex change to the power system in 6 months after the ZA002 power panel issue.

Quoting packsonflight (Reply 58): On top of that I guess that total battery capacity is way smaller given the conventional architecture of the aircraft.

No. The battery capacity is driven, primarily, by the need to keep critical avionics running in the event of total power failure. The A350 and 787 have basically the same avionics architecture and requirements. The unique electrical architecture on the 787 has nothing to do with the batteries.

Quoting packsonflight (Reply 74): How many delays did Boeing officially announce on the 787 program? was it more than 10 or more than 20?

Less than 10.

Tom

Quoting Stitch (Reply 75): As Boeing will not be the one controlling return to service, I am not sure how they can "delay" it to the point they need to spin.

By now I guess Boeing has a pretty good idea what has to be done to get the 787 in to the air again, and what the timeframe will be, but I guess they keep saying the service entry is right around the corner...

Quoting tdscanuck (Reply 76): The unique electrical architecture on the 787 has nothing to do with the batteries.

So you are saying that the capacity of the 787 battery is similar to a battery from a 767 and 330?

Quoting RickNRoll (Reply 69): "Sources say that Boeing is seriously considering a better containment system that solves both the collateral damage to other sensitive equipment and deals with the smoke better. The plan is to build a stronger and larger containment box or dome around the battery, and vent smoke and potential debris overboard through a hose or other channel. "

This is one of the "solutions" which was brought forward here at a.net already in thread #1. It deals with the collateral damage and smoke/smell issues, but it adds weight, takes up space, and it doesn't deal with the reliability issue.

When Boeing says that they sold 2000 replacement batteries for "old type planes" last year, then we can easily calculate that batteries on average last a few years, even if "old planes" have only one single battery - I have no idea how many planes have multiple batteries like the 787, if any.

From a maintenance perspective, won't airlines expect 787 batteries to be at least as reliable as present norm? At least since this rumor indicates that the weight advantage will go away or be much reduced by additional hardware.

Such a system will, if implemented, become a little more complicated than described. The containment box, or dome, will need its own ventilation system, and its outflow pressure valve will have to be made to deal with the thick paste from a thermal runaway to let the gasses/smoke get out, or a filter or other separation system must be included.

Quoting packsonflight (Reply 77): So you are saying that the capacity of the 787 battery is similar to a battery from a 767 and 330?

That's correct. The APU battery is dimensioned to start the APU. Whether the APU shall provide power by compressed air or electric power to start the main engines, that doesn't mean any significant size difference of the APU. Very likely electric power is in fact more efficient, allowing a smaller APU?

If you think about the batteries providing power for actually moving flight controls for any significant time, extending flaps/spoilers, provide anti icing, etc, forget it. If you run out of main engine generators, APU, and RAT at 30,000 feet, then you are no better off than in a traditional airliner. That will never happen, therefore the batteries serve the same purposes as on other airliners.

Those batteries have a capacity of around roughly 2 kw/h each. One could power your vacuum cleaner for a couple of hours, but it could no way wash your underwear in your washing machine.

There has been much talk on this thread about Li-Ion batteries on electric cars. That was relevant from a technology point of view. But these 787 batteries are 20 - 40 times smaller than the batteries of full size electric cars, which are specified with 200+ miles range. One could move a Tesla about 6-7 miles. Maybe 8-9 miles because the Tesla car would be a half ton lighter with a 787 battery only.

[Edited 2013-01-31 20:08:53]

Quoting prebennorholm (Reply 79): , but it could no way wash your underwear in your washing machine.

Hang on. Short cycle, low temperature, I think it could...
 

Quoting prebennorholm (Reply 78): I have no idea how many planes have multiple batteries like the 787

It is my belief that most airliners have 2 batteries. In fact, even small turboprops have 2 batteries as well.

Quoting prebennorholm (Reply 79): That will never happen, therefore the batteries serve the same purposes as on other airliners.

Isn't one of the major differences the fact that it replaces the park brake accumulator in the 787?
No big drain though.

Quoting francoflier (Reply 80): Isn't one of the major differences the fact that it replaces the park brake accumulator in the 787? No big drain though.

Why were so many batteries being locked out because they had been drained compeletly?

Quoting rcair1 (Reply 65): and the cost to replace the battery is $40K, not the $12K here

The cost difference is, because the Tesla battery has much higher capacity. More than four times higher.

Quoting cornutt (Reply 68): Presumably, with a multi-cell battery, we want to continue to operate with some number of cells failed so that we overcome the failure probability calculation with multiple cells.

You can take cells out of order by simply applying the exact same voltage to the cell, that the cell would have if it would be disconnected. If you do that, no longer any current flows through the cell. This could be achieved during charging by reducing the voltage across one cell until the whole current, that flows through the string of the other cells flows parallely to that to that cell. If the voltage would be reduced below the cell idle voltage, the cell would change into discharging mode, which is also not what we want. So applying the cells idle voltage would be the goal.

Quoting cornutt (Reply 68): If you do it with electronic devices, the BMS has to remember which ones to keep open, and it has to retain this information across power cycles.

The BMS needs a memory for a lot more things anyway.

Quoting cornutt (Reply 68): But it's not as simple as "oh pop this in, and the 787s will be flying again next week". And I'm particularly resenting the implication that the problem would be easily solvable

Absolutely, correcting this battery will take a long time.

Quoting cornutt (Reply 68): or could have been entirely avoided in the first place, except for Boeing engineers being stubborn and stupid.

It could have been avoided by a more conservative design. Using still Lithium batteries.

Quoting RickNRoll (Reply 69): "Sources say that Boeing is seriously considering a better containment system that solves both the collateral damage to other sensitive equipment and deals with the smoke better.

Bandaid tactics IMO.

Quoting packsonflight (Reply 77): By now I guess Boeing has a pretty good idea what has to be done to get the 787 in to the air again, and what the timeframe will be

I don't see how they have any better idea than the NTSB does at this point, given that the NTSB are leading the investigation and have said flat out that they have no idea what Boeing needs to do to get the 787 back in the air yet.

Quoting RickNRoll (Reply 69): Rumor of a fix Boeing is considering.

This fix wouldn't accomplish anything as far as getting the plane back in the air unless Boeing has some inside information from the FAA about doing and end-run around the NTSB. This solution doesn't seem to solve the NTSB's main problem at all, which is that destructive battery failures are happening way too frequently on the 787.

Unless Boeing is actively conspiring with the FAA on a way to get the 787 flying before the NTSB releases its findings and recommendations, then they're just tilting at windmills with this "solution". Either that or the rumor is baseless.

The third possibility is that Boeing intentionally leaked this information to gauge reaction from sources inside the FAA and/or NTSB.

Quoting rheinwaldner (Reply 82): Quoting RickNRoll (Reply 69):"Sources say that Boeing is seriously considering a better containment system that solves both the collateral damage to other sensitive equipment and deals with the smoke better. Bandaid tactics IMO.

That's the way many AD's are handled--come up with procedures or a "quick fix" hardware/software wise--get the airplanes back in the air safely--come up with the ideal solution down the road--happens a lot.

Quoting spacecadet (Reply 83): I don't see how they have any better idea than the NTSB does at this point, given that the NTSB are leading the investigation and have said flat out that they have no idea what Boeing needs to do to get the 787 back in the air yet

At some point Boeing needs to come out and say "No more Li-Ion on 787" and retrofit NiCd batteries and get the 787s back in the air - just like Cessna did with the Citation CJ4.

I don't need KING 5 to tell me this plan is detailed out and sitting on an executives desk. If the long lead tasks have not been started (software is my guess) then management should be changed.

If they fix the containment, they fixed the problem. How often the batteries fail is not a safety concern.

Quoting tdscanuck (Reply 76): How do you get 18 months? Boeing (with Thales and Hamilton-Sunstrand) managed to redesign, retrofit, test, and certify a hugely more complex change to the power system in 6 months after the ZA002 power panel issue.

That was easy. The only thing Thales had to do was to put a sticker above the switch panel reading:

"WARNING In order to avoid FOD take your screwdriver with you when you leave the E/E!"

Quoting tdscanuck (Reply 76): Yes, it's hugely different. You're talking about giving the battery the ability to shut down the airplane (that's "Threshold 1" in this scenario). That's what I mean by sacrificing the airplane to save the battery. The current battery can't shut the airplane down, it will continue to power it for as long as it can. On it's face, the two threshold idea is uncertifiable because you've set up, by design, a single-point failure that will take down the airplane. If the Threshold 1 "nice shutdown" activates in flight you're going to die.

Here I don't understand your line of thought (probably for the first time). As I understood, the batteries will normally not be discharged in flight. It was stated several times that the over discharge taking the batteries out of normal operation must have occurred on the ground. Neither the first nor the second threshold should ever be reached in flight.

The second threshold would reduce the amount of energy the battery is able to provide by maybe 5% or 10%. If this reduction would bring down an aircraft, the design with this specific battery size would have to be called not certifiable anyway.

Quoting Unflug (Reply 88): Here I don't understand your line of thought (probably for the first time). As I understood, the batteries will normally not be discharged in flight. It was stated several times that the over discharge taking the batteries out of normal operation must have occurred on the ground. Neither the first nor the second threshold should ever be reached in flight.

It doesn't matter if it "shouldn't" happen, you don't want to tell the regulators that the battery that is the last line of defense against power loss to critical systems will call it a day earlier than it might otherwise have because you want to save a little money. Trust me the FAA would much rather see you say "the battery will set itself on fire to get the last joule to the flight control systems" than "the battery shuts off at 10% above absolute minimum to prevent needing to remove the battery for bench testing". The first indicates you know just how bad things have gotten if you have no engine generators, the APU is dead, and the RAT is broken. Oh and you've managed to burn through quite a bit of stored energy. By the time you reach minimum charge in flight, you are already looking for a place to have the kindest, cuddliest crash possible.

Yet having a early cut out may CAUSE crashes as its a new and exciting failure point.

The real answer is the Airlines that are bricking the batteries need to either fire up the APU or connect ground power to minimize the stress on batteries not designed to keep the plane powered up for long periods.

(oh and yes, the FAA really wants you to shut down the battery just before it sets itself on fire, but if it had to pick too early and too late in this system... well its already mandated containment systems)

Quoting 7BOEING7 (Reply 84): That's the way many AD's are handled--come up with procedures or a "quick fix" hardware/software wise--get the airplanes back in the air safely--come up with the ideal solution down the road--happens a lot.

I am aware of that approach. And it is fine within some limits. But saying, the fire isn't fixed, so we just keep the fire in a safe box is far beyond those limits IMO. Thats like saying, we allow bombs in the baggage if they are just housed in a metal suitcase.

Quoting seahawk (Reply 86): If they fix the containment, they fixed the problem. How often the batteries fail is not a safety concern.

Hopefully you never have to design systems that might cost the live of people in case of failure. And hopefully those who do, don't think like you.

The only problem you would like to have adressed seems to be the short term impact on the pocket... It will bite you the next time, that fire starts. And it will not restore public confidence. Especially after the next fire.

Quoting XT6Wagon (Reply 89): It doesn't matter if it "shouldn't" happen, you don't want to tell the regulators that the battery that is the last line of defense against power loss to critical systems will call it a day earlier than it might otherwise have because you want to save a little money.

What do you mean by "a day earlier"? If ever used in flight the battery will not last for days. The battery normally is kept in a loaded condition and not used in flight. Quoting CM in thread #2:

The main battery is a required redundancy in the system (it provides power to the captain's instruments), but it is never used in flight during normal operations.

Quoting XT6Wagon (Reply 89): Trust me the FAA would much rather see you say "the battery will set itself on fire to get the last joule to the flight control systems" than "the battery shuts off at 10% above absolute minimum to prevent needing to remove the battery for bench testing".

- Even in the worst case the battery does not provide power to the flight control systems.
- 10% less usable energy can be made up by using a 10% larger battery.
- On top of that, no one would prevent the system to use the second threshold only when on the ground.

Quoting XT6Wagon (Reply 89): if you have no engine generators, the APU is dead, and the RAT is broken

In this case, the battery won't save the aircraft anyway. If the battery was to be able to replace engine power, APU and RAT it would have to be much, much larger.

Quoting XT6Wagon (Reply 89): By the time you reach minimum charge in flight, you are already looking for a place to have the kindest, cuddliest crash possible.

Exactly.

Quoting rheinwaldner (Reply 90): Hopefully you never have to design systems that might cost the live of people in case of failure. And hopefully those who do, don't think like you. The only problem you would like to have adressed seems to be the short term impact on the pocket... It will bite you the next time, that fire starts. And it will not restore public confidence. Especially after the next fire.

Batteries fail. It just needs to be made sure that such a failure poses no danger to the whole system. And fixing the containment might not be an easy task, while keeping the current battery design. But any way it is unreasobale to demand that the batteries should not fail, because eventually every battery fails. It must be made sure that such a failure is easily contained.

Quoting seahawk (Reply 92): Quoting XT6Wagon (Reply 89): It doesn't matter if it "shouldn't" happen, you don't want to tell the regulators that the battery that is the last line of defense against power loss to critical systems will call it a day earlier than it might otherwise have because you want to save a little money. What do you mean by "a day earlier"? If ever used in flight the battery will not last for days. The battery normally is kept in a loaded condition and not used in flight.

"Call it a day" is a colloquial phrase used in the US; it means "end of the work day", "stop working", or more generally "stop what you were doing". In this context XT6Wagon meant that the battery would shut down before it was completely exhausted. He did not mean literally '24 hours earlier'. Just a difference in language patterns.

sPh

Quoting rheinwaldner (Reply 82): Bandaid tactics IMO.

There is not a single Airplane, Jetliner, Nuclear Power Plant, or anything in existence that is designed for absolute safety; and in fact what is agreed upon as a "safe enough" approach is often a "band-aid" tactic because there are no perfect design solutions for most issues.

So yes, this problem will in fact be fixed with some kind of "band-aid" approach.

Quoting spacecadet (Reply 83): Unless Boeing is actively conspiring with the FAA on a way to get the 787 flying before the NTSB releases its findings and recommendations, then they're just tilting at windmills with this "solution". Either that or the rumor is baseless.

Welcome to the real world - It is quite common for the FAA to allow aircraft to fly long before the NTSB investigation is completed. In fact; I am not sure if there are any cases where the FAA waited until after the NTSB report was complete before approving some kind of change that allowed the aircraft to return to service. I believe you have a misunderstanding of the functions of the NTSB and the FAA; and their relationship.

Quoting seahawk (Reply 86): If they fix the containment, they fixed the problem. How often the batteries fail is not a safety concern.

I am not sure of that. While a containment upgrade appears to be obvious; there may be changes to the monitoring/charging circuits even if there are no problems with the batteries themselves as roomer seems to indicate.

Quoting rheinwaldner (Reply 90): I am aware of that approach. And it is fine within some limits. But saying, the fire isn't fixed, so we just keep the fire in a safe box is far beyond those limits IMO. Thats like saying, we allow bombs in the baggage if they are just housed in a metal suitcase.

But we do allow bombs in the cargo hold. I used to ship small explosive devices by air all the time (the operative word in this case is "small"; and of course the packaging was designed and tested to contain the detonation of a device - actually had to fully contain a device twice the size of what we were producing and shipping - in 10 out of 10 test with no damage visible to the outer box). The fact is that many things on an Aircraft can fail in such a way to release energy (including items in luggage). All that is required is that they be contained or have adequate space such that the failure/release of energy does not noticeably harm other things in the area.

The fact of the matter is that Boeing and the FAA will agree on at least a temporary fix, and later a permanent fix if needed with the understanding that some batteries will in fact fail and have thermal run away and a battery fire. LI-Ion batteries will not be found to be inherently unsafe for flight.

Have a great day,

Quoting rheinwaldner (Reply 82): You can take cells out of order by simply applying the exact same voltage to the cell, that the cell would have if it would be disconnected. If you do that, no longer any current flows through the cell.

In other words, you need control of the charging current on a per-cell basis. That largely negates the advantage of the multiple cells.

Quoting rheinwaldner (Reply 82): The BMS needs a memory for a lot more things anyway.

The existing BMS only has memory for maintenance purposes, if it has any at all. This is memory for a safety-critical purpose, that has to survive power cycles. You are hugely underestimating the safety implications and the certification effort.

Quoting spacecadet (Reply 83): Unless Boeing is actively conspiring with the FAA on a way to get the 787 flying before the NTSB releases its findings and recommendations, then they're just tilting at windmills with this "solution".

Several points: (1) the NTSB is not the regulatory body, the FAA is. The NTSB has no stake in whether the aviation busines survives or not. They routinely ask for things that are clearly impractical (e.g., that fuel not catch fire in a crash). (2) As others have said, interim solutions are pretty routine for short-term resolution of ADs, and if it gets the top of the fault tree back to a good number and is acceptable to the operators, what's the diff? (3) The NTSB will probably not release its final report for several years. There is no statuatory requirement that the FAA wait on the NTSB's final report. The FAA has the authority to revise the terms of the AD at any time that it sees fit. (4) I'm really getting sick of seeing these trollish statements that say "if the 787 ever flies again, it proves that there is a conspiracy between Boeing and the FAA".

Quoting RickNRoll (Reply 81): Why were so many batteries being locked out because they had been drained compeletly?

In many cases, it was because ground crews were using the batteries for longer than Boeing's recommended time limits.

Quoting spacecadet (Reply 83): This fix wouldn't accomplish anything as far as getting the plane back in the air unless Boeing has some inside information from the FAA about doing and end-run around the NTSB. This solution doesn't seem to solve the NTSB's main problem at all, which is that destructive battery failures are happening way too frequently on the 787.

The NTSB's concern was that a battery fire or leaking electrolytes could damage critical systems. Yes, the NTSB would prefer that a battery never catch fire, but if wishes were horses... NiCad and lead acid batteries can catch fire, as well, even if the statistical probability is much lower than with Li-Ion.

Quoting rheinwaldner (Reply 90): But saying, the fire isn't fixed, so we just keep the fire in a safe box is far beyond those limits IMO.

That is what the Special Conditions call for.

Quoting Stitch (Reply 97): Quoting RickNRoll (Reply 81): Why were so many batteries being locked out because they had been drained compeletly? In many cases, it was because ground crews were using the batteries for longer than Boeing's recommended time limits.

Do you know why?
In normal service we rarely use the Main battery. The aircraft sits on ground power all the time. Once in a while I might be on an off-pier stand, and do a real battery start, but very rarely. Its quite scary on an A320 or B767 to turn on the batteries and see a couple of lights blink on, and nothing else. Then use the batteries to start the APU, and have no indications at all until the APU Generator comes on line.

On the B767 when you shut the aircraft down fully and turn off all power, as you walk away you look back and see the nose gear park brake set light is on. It comes off the hot battery bus. OK for an overnight, but if the aircraft is there for a week, better to unscrew it!
Is there something like this on the B787 that was not seen at Seattle when they had GPU in all the time?

p.s. I have worked on the line for 30 years and changed one battery in all that time.

http://www.japantoday.com/category/n...mages-from-boeing-for-787-troubles


NH wants compensation. Whoever told me in the other threads that they didn't have a right to do this, now u can stop complaining about me.