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B787 Grounding: Tech/ops Thread Part 2

Sat Mar 09, 2013 8:43 am

Link to the first thread: Tech/Ops Discussion Of The 787 Grounding (by CM Jan 22 2013 in Tech Ops)
 
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kanban
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RE: B787 Grounding: Tech/ops Thread Part 2

Sat Mar 09, 2013 5:08 pm

We've tried to keep this thread limited to facts and data limited to the 787 and it's specific battery. Wild speculations, 'similar to' scenarios, and blame game posts are not welcome.
 
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RE: B787 Grounding: Tech/ops Thread Part 2

Sat Mar 09, 2013 11:09 pm

Is there any truth to this claim.

ound this blog topic on the battery fire in Boston. Can anyone confirm the technical details?


The NTSB interim report into the Japan Airlines 787 battery fire in Boston in January says a second smaller lithium ion battery located above the large battery showed signs of failure before it was physically removed from the belly of the Dreamliner by an airport fire crew.

The implication is that had this main rear lithium-ion battery fire broken out while the JAL flight was making its flight from Narita to Boston there would have been a second stacked lithium ion fire in the same location directly under the rear passenger cabin just behind the trailing edge of the wing.

This smaller battery that was installed on a rack above the battery that burned was also supplied by Japanese manufacturer GS Yuasa, and was intended to provide emergency power for the jet’s flight controls for 10 minutes or more “when no other electrical power is available.”

The NTSB investigators found the exterior of this battery had been “lightly scorched” by the fire below and noted its case had openings at the corners.

The firefighters suppressed the fire before it could spread to that second battery.


http://blogs.crikey.com.au/planetalk...7-was-at-risk-of-2nd-battery-fire/

That is, that there is another, smaller lithium battery that was at risk of catching fire from the main battery catching fire.
Also, it appears that there was fire that had escaped containment. There was debate over weather this was due to the fire fighters, or if it had happened before the fire fighters arrived on the scene.
 
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RE: B787 Grounding: Tech/ops Thread Part 2

Sat Mar 09, 2013 11:57 pm

There was truth that a second battery was "lightly scorched", but I am not sure that means it is true it would have subsequently caught fire itself.

I'm guessing this second battery is the one in the copper-colored box with the Honeywell label. Have to say that it looks completely undamaged in the NTSB picture of the APU battery location.


Quoting RickNRoll (Reply 2):
Also, it appears that there was fire that had escaped containment. There was debate over weather this was due to the fire fighters, or if it had happened before the fire fighters arrived on the scene.

That the firefighters reported flames were visible escaping the box when they arrived in the EE bay should have been clear enough evidence.

[Edited 2013-03-09 16:00:36]
 
hivue
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RE: B787 Grounding: Tech/ops Thread Part 2

Sun Mar 10, 2013 12:32 am

Quoting RickNRoll (Reply 2):
a second smaller lithium ion battery located above the large battery showed signs of failure before it was physically removed from the belly of the Dreamliner by an airport fire crew.
Quoting Stitch (Reply 3):
I'm guessing this second battery is the one in the copper-colored box with the Honeywell label. Have to say that it looks completely undamaged in the NTSB picture of the APU battery location.

How could this "smaller lithium ion battery" appear in the NTSB photograph of the APU battery location in the airplane if the fire crew had removed it from the airplane?
"You're sitting. In a chair. In the SKY!!" ~ Louis C.K.
 
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RE: B787 Grounding: Tech/ops Thread Part 2

Sun Mar 10, 2013 12:45 am

Quoting hivue (Reply 4):
How could this "smaller lithium ion battery" appear in the NTSB photograph of the APU battery location in the airplane if the fire crew had removed it from the airplane?

I don't believe they did. To my knowledge, they only removed the APU battery.
 
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RE: B787 Grounding: Tech/ops Thread Part 2

Sun Mar 10, 2013 2:37 am

Oh, OK. I guess that blogger could use an editor. Will have to check the report to see if what he says is correct.
"You're sitting. In a chair. In the SKY!!" ~ Louis C.K.
 
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RE: B787 Grounding: Tech/ops Thread Part 2

Sun Mar 10, 2013 4:52 am

Quoting Stitch (Reply 3):
There was truth that a second battery was "lightly scorched", but I am not sure that means it is true it would have subsequently caught fire itself.

I dont think that people have looked at the below document that shows anothe 20 odd picyures of the fire scene.

Take a look at the pictures from page 10, the 10 minute avionics backup battery is clearly marked and does sit directly above the APU battery in a non fully sealed container, as it is on a rack directly above the burning APU battery it was receiving flame, heat and expelled electrolyte onto its bottom like it was on a hotplate, this cannot be good. More certification issues.

Also browse the pictures from page 10 down and read the fire-fighters report, the fire was not on its way out and imagine how much further damage could have been caused before it burnt itself out.

http://www.ntsb.gov/investigations/2...ket_documents/787_docket_doc19.pdf
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RE: B787 Grounding: Tech/ops Thread Part 2

Sun Mar 10, 2013 6:59 am

Quoting BoeingVista (Reply 7):

All of the fire/smoke/spillover problems can be solved with containment. What happened didn't happen in the million or so hours of testing by Yuasa and Boeing. The cause of the fire itself is so elusive that the NTSB still doesn't have root cause for either fire...and that's the real problem with these batteries.

Without knowing why they went runaway, you can't fix it. I still hold with my initial reaction; shoehorn an interim battery using already certified chemistry, (NiCd), and get flying. It looks like there's lots of room in there for a longer battery pack to fit on the current batter rails, (if it needed to be longer). I'd be shocked if the 787 charging system couldn't be set for a NiCd pack.

So far, it's impossible to tell exactly what Boeing and the feds are doing, (I'd love to be a fly on the walls), but I'd bail on the current chemistry pronto, and to tell the truth, I'd bail on Li-ion chemistry altogether. No matter how benign the chemistry, (LiFePo4, for example), it's still LITHIUM and that stuff blows up planes, right...? (insert smiley here)
What the...?
 
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RE: B787 Grounding: Tech/ops Thread Part 2

Sun Mar 10, 2013 11:02 am

I have some more (technical ) questions :

- How many Litium-ion batteries are in total installed in the 787 ? Three (3) are known to me up to now.

- Are all Litium-ion batteries affected by the Boeing solution for lifting of the 787 grounding (containment and extra ventilation) ?

- Is battery re-location also included in the Boeing proposed fix ?

- What is(are) exactly the function(s) of each battery ?

To start things up :

- AFAIK the Main and Avionics batteries are installed as the (last) electrical back-up for flight critical systems if all other electrical sources (engine, APU and RAT generators) have failed or after a total electrical grid failure.

- The APU battery is only used for APU starting and is needed for ETOPS certification, to deliver two extra serviceable APU generators, after an APU in flight start, if needed in a non-standard electrical procedure.
AFAIK the APU battery can't be used to augment the main battery in case of an electrical emergency.
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hivue
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RE: B787 Grounding: Tech/ops Thread Part 2

Sun Mar 10, 2013 5:40 pm

Quoting JoeCanuck (Reply 8):
shoehorn an interim battery using already certified chemistry, (NiCd), and get flying. It looks like there's lots of room in there for a longer battery pack to fit on the current batter rails, (if it needed to be longer). I'd be shocked if the 787 charging system couldn't be set for a NiCd pack.

But there remains the major issue of whether any NiCad solution that could possibly be made to fit could also meet the 787's power requirements. In the Boeing video cited in other posts in other threads Mike Sinnett says Li-Ion was not chosen to save weight (i.e., for its size) but because of power requirements.



Quoting 747classic (Reply 9):
The APU battery is only used for APU starting

The APU controller is powered by the APU battery. If a the APU battery tanks the APU shuts down.

Quoting 747classic (Reply 9):
or after a total electrical grid failure

If there is no electrical grid at all available it's unlikely that batteries are going to be of any use.
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RE: B787 Grounding: Tech/ops Thread Part 2

Sun Mar 10, 2013 6:03 pm

Quoting 747classic (Reply 9):
How many Litium-ion batteries are in total installed in the 787 ? Three (3) are known to me up to now.

I don't know precisely - but multiple posts have mentioned that Li-Ion batteries are used throughout many aircraft both from Boeing and AirBus - and presumably others as well. Most of those batteries are quite small and back up individual items - like exit signs and the such.
The uniqueness of the 787 is the use of a large, high capacity Li-Ion for Main Ship and APU batteries. The AB350 was intended to do this as well, but AB has stated they will launch with NiCads and consider upgrade to Li-Ion later.

Quoting 747classic (Reply 9):
Are all Litium-ion batteries affected by the Boeing solution for lifting of the 787 grounding (containment and extra ventilation) ?

I don't think so. If that were the case, many other a/c would be impacted.

Quoting 747classic (Reply 9):
Is battery re-location also included in the Boeing proposed fix ?

I don't think so - but that is not authoritative. Has Boeing's proposal been released to the public?

Quoting 747classic (Reply 9):
What is(are) exactly the function(s) of each battery ?
Quoting 747classic (Reply 9):
To start things up :

I think you have it correct - with one minor comment.. I believe the main battery is intended to be an interim source while alternative sources come up. It is not considered one of the non-time limited extra sources. That is why the APU battery is there - to start the APU. The non-time limited sources include the main engine generators, the APU generators and the RAT.
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RE: B787 Grounding: Tech/ops Thread Part 2

Sun Mar 10, 2013 6:09 pm

Quoting rcair1 (Reply 11):
The AB350 was intended to do this as well, but AB has stated they will launch with NiCads and consider upgrade to Li-Ion later.

Read somewhere they will stay with Li-Ion on the first three test vehicles and change to NiCad on unit 4.. allowing them to meet first flight and test projections avoiding a 787 type delay. Evidently there needs to be software changes with the battery change.
 
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RE: B787 Grounding: Tech/ops Thread Part 2

Sun Mar 10, 2013 6:34 pm

Quoting BoeingVista (Reply 7):
I dont think that people have looked at the below document that shows anothe 20 odd pictures of the fire scene.

Thank you for that. The bottom is indeed where the scorching happened.



Quoting 747classic (Reply 9):
- How many Litium-ion batteries are in total installed in the 787 ? Three (3) are known to me up to now.

Ship's Battery, APU Battery, Avionics Battery (not sure if there is just one in the aft EE bay or also one in the forward EE bay, as well). Li-Ion batteries also power emergency cabin lighting.



Quoting 747classic (Reply 9):
- Are all Litium-ion batteries affected by the Boeing solution for lifting of the 787 grounding (containment and extra ventilation) ?

No. The ones that power the emergency lighting are not considered a risk. The Avionics battery also seems to not be considered a risk.



Quoting 747classic (Reply 9):
- Is battery re-location also included in the Boeing proposed fix?

I am guessing no, but to my knowledge most of the particulars of Boeing's proposed fix have not been made public.

Quoting 747classic (Reply 9):
- What is(are) exactly the function(s) of each battery?

The Ship's Battery assists the APU battery during APU start. It also provides power to the Captain's instrument panel in the event of a loss of generator power (engine; APU; RAT).

The APU battery can start the APU on it's own, but normally is used in conjunction with the Ship's Battery for this function.

The Avionics battery is a new one to me, but it sounds like it's the terminal emergency power source for flight deck instruments.
 
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RE: B787 Grounding: Tech/ops Thread Part 2

Sun Mar 10, 2013 7:13 pm

Quoting hivue (Reply 10):
The APU controller is powered by the APU battery. If a the APU battery tanks the APU shuts down.

Is that correct? What that means is that you can't MEL the APU battery, if you need to have the APU available for ETOPS, doesn't it? The APU could be started with one engine still going, but it can't run at all without the APU battery being functional.
 
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RE: B787 Grounding: Tech/ops Thread Part 2

Sun Mar 10, 2013 7:41 pm

Quoting RickNRoll (Reply 14):
What that means is that you can't MEL the APU battery, if you need to have the APU available for ETOPS, doesn't it?

You can dispatch with the APU battery (or an APU, for that matter) inoperative, but it limits you to ETOPS-180 (you must be within 180 minutes of landing at a suitable airport).

As it has been explained to me, this is the case for other Boeing Commercial Aircraft families, as well.

[Edited 2013-03-10 12:44:12]
 
JoeCanuck
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RE: B787 Grounding: Tech/ops Thread Part 2

Sun Mar 10, 2013 7:42 pm

Quoting hivue (Reply 10):
But there remains the major issue of whether any NiCad solution that could possibly be made to fit could also meet the 787's power requirements. In the Boeing video cited in other posts in other threads Mike Sinnett says Li-Ion was not chosen to save weight (i.e., for its size) but because of power requirements.

Increasing capacity just means increasing the number of cells. Then, the limitations are size and weight.

The 787 battery is nominal 30v, 65Amp/hr, (with a normal operating range of between 20v and 30v) and the 777 battery is 28v, 50Amp/hr capacity. You basically have to add 30% more cells, (which means 30% larger size as well), to get the same capacity as the 787 batter...but I have no idea about the size and weight.

I'm having a heck of a time digging up the physical dimensions of the 777 battery pack, but individual cells don't really care how they're stacked so a pack could probably be built that would fit on the 787 battery rails, but probably stick out further, or be a bit taller.

Anyway, the gist of my position is that I can't wrap my head around why they don't stage the process, using an interim, alternate battery chemistry temporarily. Maybe certifying even a NiCd pack, (since it would have to be a unique pack, regardless of the chemistry being certified), would take as much time as getting the already certified pack fixed.

I don't claim to be an expert in batteries and there are a lot of smart boffins at Boeing working on this. I'm basically trying to understand what the heck is going through their minds, (because inquiring minds want to know), and I want to see that darned plane back in the air, (which I'm pretty sure is their goal as well).

At the same time, I like to solve problems so I don't mind speculating and offering solutions to the ether, which won't make a bit of difference in the long run, but keeps my neurons active.
What the...?
 
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RE: B787 Grounding: Tech/ops Thread Part 2

Sun Mar 10, 2013 7:46 pm

Quoting hivue (Reply 10):
The APU controller is powered by the APU battery. If a the APU battery tanks the APU shuts down.

This apparently did happen on the ground, with no other power sources available (other than the Main battery). I too would like to know whether this is always the case if there are other power sources available: ground power, engine power, RAT, etc. I find it hard to believe that the APU can't be run at all in any circumstances without a functional APU battery.

It does seem a bit odd to have the APU controller requiring the APU battery when the APU itself is running, but no other power source is online. I have to wonder if the APU shutdown on JA829 was due to the way the airplane power was configured at that moment, or if it was a design oversight. I skimmed the NTSB report but I don't recall seeing any information on that point.
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RE: B787 Grounding: Tech/ops Thread Part 2

Sun Mar 10, 2013 7:46 pm

Quoting JoeCanuck (Reply 16):
The 787 battery is nominal 30v, 65Amp/hr, (with a normal operating range of between 20v and 30v) and the 777 battery is 28v, 50Amp/hr capacity.

Is the current provided at airplane power-up an issue? Per a Boeing presentation, the 787 battery can provide 150A while the 777 battery provides 16A.


Quoting JoeCanuck (Reply 16):
The 787 battery is nominal 30v, 65Amp/hr, (with a normal operating range of between 20v and 30v) and the 777 battery is 28v, 50Amp/hr capacity. You basically have to add 30% more cells, (which means 30% larger size as well), to get the same capacity as the 787 batter...but I have no idea about the size and weight.

Per the same Boeing presentation, the 787 battery uses 8 cells while the 777 battery uses 20 cells. That might impact the size and weight (the 777 battery weighs 48.5kg compared to 28.6kg for the 787).



Quoting PITingres (Reply 17):
I find it hard to believe that the APU can't be run at all in any circumstances without a functional APU battery.

This is evidently the case for all Boeing Commercial Airplane families.

[Edited 2013-03-10 12:51:55]
 
hivue
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RE: B787 Grounding: Tech/ops Thread Part 2

Sun Mar 10, 2013 9:20 pm

Quoting RickNRoll (Reply 14):
Is that correct?
Quoting PITingres (Reply 17):
I have to wonder if the APU shutdown on JA829 was due to the way the airplane power was configured at that moment, or if it was a design oversight. I skimmed the NTSB report but I don't recall seeing any information on that point.

See footnote 6 of page 1 of the report:
"The APU battery provides power to start an APU during ground and flight operations. The APU controller (discussed in section 1.6.5) monitors the parameters that are needed to operate the APU. The APU controller is powered by the APU battery bus, which receives its power from the APU battery. If the APU battery fails, then the APU battery bus will no longer receive power, and the APU will shut down."

Quoting JoeCanuck (Reply 16):
Increasing capacity just means increasing the number of cells. Then, the limitations are size and weight.
Quoting Stitch (Reply 18):
Is the current provided at airplane power-up an issue? Per a Boeing presentation, the 787 battery can provide 150A while the 777 battery provides 16A.

I think that when they mention power requirements for the 787 they're talking about how many amps can be delivered, but I don't think it has to do with airplane power up but with emergency backup situations. I suspect that the electric brakes pull a lot of amps.
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RE: B787 Grounding: Tech/ops Thread Part 2

Sun Mar 10, 2013 10:55 pm

Quoting hivue (Reply 19):
I think that when they mention power requirements for the 787 they're talking about how many amps can be delivered, but I don't think it has to do with airplane power up but with emergency backup situations.

The slide specifically noted this was current provided at airplane power-up.
 
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RE: B787 Grounding: Tech/ops Thread Part 2

Mon Mar 11, 2013 1:47 am

Quoting Stitch (Reply 20):
The slide specifically noted this was current provided at airplane power-up.

Thanks. I should look at the video presentation again.

If the 787 actually needs 150A for routine processes it looks like the 777 can do on 16A then there may be no hope at all for a non-Li-Ion solution.
"You're sitting. In a chair. In the SKY!!" ~ Louis C.K.
 
mjoelnir
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RE: B787 Grounding: Tech/ops Thread Part 2

Mon Mar 11, 2013 2:24 am

Quoting Stitch (Reply 18):
Is the current provided at airplane power-up an issue? Per a Boeing presentation, the 787 battery can provide 150A while the 777 battery provides 16A.

You are comparing apples with bananas.

A is the current, A/h is the capacity.
The 787 has a battery of 65 A/h capacity and the 777 has a battery of 50 A/h capacity.

The 16 A draw of the 777 should be the draw (current) on the main battery.
Regarding the APU: if the draw for the APU start on the 787 would be 150 A and on the 777 16 A, than the APU on the 787 should be 10 times the size of the APU on the 777.
I think you should rethink your argument.
 
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Stitch
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RE: B787 Grounding: Tech/ops Thread Part 2

Mon Mar 11, 2013 2:54 am

Quoting mjoelnir (Reply 22):
You are comparing apples with bananas.

No, Boeing is, since it's their slide.

Quoting mjoelnir (Reply 22):
I think you should rethink your argument.

I think you should take it up with Boeing, since it's their slide.



[Edited 2013-03-10 19:57:14]
 
JoeCanuck
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RE: B787 Grounding: Tech/ops Thread Part 2

Mon Mar 11, 2013 3:38 am

NiCd's are famous for being able to handle high power draws. The capacity and current draw may have little to do with each other directly, except for duration of power delivery. Generally speaking, they are considered more reliable in high draw conditions than Li-ions...though I'm betting the 787 batteries aren't your standard power drill units.

It's only recently that power tools, (which tend to have a very high amperage draw), began switching to Li-ion batteries. It would take 44 of my Makita power tool batteries to equal the capacity and voltage of the 787 batteries.

I suspect that the 777 NiCd pack could handle a much higher draw than 16Amps. That's just what the 777 batteries are required to provide, not necessarily the maximum current they can supply 24v.
I'm guessing the 777 pack is made up of packs that resemble flashlight batteries, in series and parallel to provide the voltage and capacity.

IF the NiCd's could handle the higher draw, then the capacity and voltage would both have to be increased to match the 787 requirements and that would mean a battery of at least 150 lbs and probably 50% larger than the 777 batteries.

Even going with lead acid batteries might be possible. The gel battery in my motorcycle, (coincidentally a Yuasa), is 12v and 20 amp/hr. It's completely sealed, quite robust and designed for high current draws and random charging. 9 batteries like this with maybe 25 amp/hr capacity would give 36v and 75 Amp/hr total capacity in a package about 12"x12"x18"...but it would be one heavy sucker...probably in the 200 lb range.

I seriously doubt the charging system of the 787 couldn't be reprogrammed to handle either option. These batteries are not nearly as sensitive to charge and discharge variances as Li-ions. You could practically charge them with jumper cables from the baggage carts.

Bullet proof containment is probably the only way they can possibly get the Li-ion packs recertified and even then, they'll be a tough sell. I have a very difficult time believing they aren't working on a permanent solution using different chemistry, even if they stay within the Li-ion family. Cessna has chosen LiFePo4 for the CJ-4, which I think is a very good choice.

The end solution is the easy part....they'll have lots of time to come up with that. It's the interim solution which gets the planes back in the air that's the tough part.

If only they could come up with a root cause for the fires...then they could actually have something concrete to fix. It's the uncertainty and unpredictability that are the real buggers.
What the...?
 
kalvado
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RE: B787 Grounding: Tech/ops Thread Part 2

Mon Mar 11, 2013 4:19 am

Quoting JoeCanuck (Reply 16):
The 787 battery is nominal 30v, 65Amp/hr, (with a normal operating range of between 20v and 30v) and the 777 battery is 28v, 50Amp/hr capacity. You basically have to add 30% more cells, (which means 30% larger size as well), to get the same capacity as the 787 batter...but I have no idea about the size and weight.
Quoting JoeCanuck (Reply 24):
I suspect that the 777 NiCd pack could handle a much higher draw than 16Amps. That's just what the 777 batteries are required to provide, not necessarily the maximum current they can supply 24v.

This makes me wonder - 777 battery should last for about 3 hours - capacity of 50 Ah/16 A draw.. 3 hours of what? Over the ocean flight with all engine and APU generators inop, and RAT not deployed? Or 3 hours of ground operation?
It doesn't make sense to me - first scenario is too harsh; and why would 3 hours worth of power be needed?
Possibly there is some other operation mode with much higher current draw not mentioned on a chart, and 16 A is to keep essential instruments and controls in flight?
 
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RE: B787 Grounding: Tech/ops Thread Part 2

Mon Mar 11, 2013 6:20 am

Quoting kalvado (Reply 25):
This makes me wonder

Just guessing but I suspect they did some intentional overkill on the battery. They had to use enough cells to get 24v out of 1.2v cells. They may very well have figured that they have the room on the big beast of a plane that they might as well get some extra capacity. It was also early in the ETOPS era so too much was better than not enough.
What the...?
 
mjoelnir
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RE: B787 Grounding: Tech/ops Thread Part 2

Tue Mar 12, 2013 11:26 am

Quoting Stitch (Reply 23):
I think you should take it up with Boeing, since it's their slide.

I do not have to take it up with Boeing, it is your argument in this discussion.

If you look at the advertisement slide of Boeing you presented, it is misleading.

It seems to compare the batteries, but it does not say anything about the maximum current you can draw of the batteries.


The number of 150 A is for the start up of B 787 and the 16 A for the start up of the B 777.
It is plainly misleading to set it up this way.
It has nothing to do with the maximum current both batteries can provide, so it does not say anything about the possibility of using the B 777 battery in the B 787.

As an example a typical automotive lead acid battery of 12 V 65 Ah will provide you with a minimum cold start capability of around 600 A current down to -18°C. 16 A even at 32 V would hardly start even the smallest car.
A typical Ni/Cad D size can provide about 35 A maximum current.

Both the Ni/Cad 50 Ah of the 777 and the Lithium/ion 65 A/h of the 787 are used as a single battery to start the APU.
 
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Stitch
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RE: B787 Grounding: Tech/ops Thread Part 2

Tue Mar 12, 2013 12:16 pm

Quoting mjoelnir (Reply 27):
I do not have to take it up with Boeing, it is your argument in this discussion.

I didn't offer an argument, I asked a question:

Quoting Stitch (Reply 18):
Is the current provided at airplane power-up an issue? Per a Boeing presentation, the 787 battery can provide 150A while the 777 battery provides 16A.

Rather than answer that question, you went with a tangential argument unrelated to my question.
 
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RE: B787 Grounding: Tech/ops Thread Part 2

Tue Mar 12, 2013 12:37 pm

Quoting Stitch (Reply 28):

So about what is your question?

The question could be can the Ni/cad provide the 150 A?
The question could be is 150 A to much for the lithium/ion?
Can the lithium/ion battery provide 150 A a long enough time'
Is an 65 A/h battery not far too small to provide 150 A if in another application a 50 A/h battery used to provide 16 A?

I can imagine a lot of questions.

But you started of with: the 787 battery can provide 150 A while the 777 battery provides 16 A.
So you compare what batteries CAN provide, and I am reasonable sure that the 50 A/h Ni/Cad battery of the B 777 CAN provide more than a current of 16 A.
 
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CARST
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RE: B787 Grounding: Tech/ops Thread Part 2

Tue Mar 12, 2013 2:56 pm

Quoting Stitch (Reply 18):
Per the same Boeing presentation, the 787 battery uses 8 cells while the 777 battery uses 20 cells. That might impact the size and weight (the 777 battery weighs 48.5kg compared to 28.6kg for the 787).
Quoting JoeCanuck (Reply 16):

The 787 battery is nominal 30v, 65Amp/hr, (with a normal operating range of between 20v and 30v) and the 777 battery is 28v, 50Amp/hr capacity. You basically have to add 30% more cells, (which means 30% larger size as well), to get the same capacity as the 787 batter...but I have no idea about the size and weight.
Quoting JoeCanuck (Reply 24):
IF the NiCd's could handle the higher draw, then the capacity and voltage would both have to be increased to match the 787 requirements and that would mean a battery of at least 150 lbs and probably 50% larger than the 777 batteries.

But what could really be Boeings problem? You can not tell me that an 30-50% weight increase resulting in a battery weighing something around 70kg would really be a problem? That are 40kg more, so what? If it would help to lift the grounding why not certify a NiCd battery?

I think there has to be another reason...

Some people said that NiCd batteries have a slightly varying power output what could destroy components which are not made for this varying power inputs. LIon batteries have a more stable power output, could this be the reason? Did they probably use many components on the 787 that would not accept the varying power of a NiCd battery? (Please note that this should not be a speculation, this is a question to the technical more knowledged people here.)
 
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RE: B787 Grounding: Tech/ops Thread Part 2

Tue Mar 12, 2013 3:59 pm

Quoting mjoelnir (Reply 29):

You could do a NiCd battery that would serve the purpose. It would be about 3x the weight and 2x the size based on total watt-hours for the system. You would also need 25-75% extra capacity to account for the differences in charge and discharge characteristics, depending on the total discharge time and regulatory requirements to get the battery back to full strength. This could realistically place it at about 4x weight and 3x volume for comparable performance.

Quoting CARST (Reply 31):
If it would help to lift the grounding why not certify a NiCd battery?

It wouldn't make the process faster. You need a brand new design for the battery management system and charger, and you need to make sure that design is fully vetted and compatible with the 787's power systems.

The reliability of the existing battery is going to need to be addressed, and changes of some sort are likely. Two months after the incidents though, we on a.net still don't really have any idea on the root cause(s). A manufacturing defect in the batteries would have been the easiest to address.

I have no idea of Thales did mimic testing of the flight charge/discharge characteristics to age batteries consistent with real flight conditions (and not just assumed conditions), but hopefully there is enough data in non-failed BMS units that you could do simulation across a large number of units over the course of a month or two and autopsy the cells afterwards to determine if any dendrites have formed, why the premature failures are happening, and if there is something that was unexpected in the behavior.
 
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RE: B787 Grounding: Tech/ops Thread Part 2

Tue Mar 12, 2013 5:16 pm

Quoting JoeCanuck (Reply 8):
Without knowing why they went runaway, you can't fix it. I still hold with my initial reaction; shoehorn an interim battery using already certified chemistry, (NiCd), and get flying. It looks like there's lots of room in there for a longer battery pack to fit on the current batter rails, (if it needed to be longer). I'd be shocked if the 787 charging system couldn't be set for a NiCd pack.

Posted this long ago in another thread which quickly became overrun with so-called 'experts' who knew everything such as the electrolyte makeup. This is not my opinion, but taken from internal messages which for obvious reasons can not be re-posted. A so called Ni-Cad battery solution for the 787 as we are told, would be about 3 times the weight and size of a 777 Ni-Cad battery. The 787 charging system could not be set for Ni-Cads as it is. There is a voltage at which, if the Lion battery drops below this voltage, that the battery and shuts off and can only be brought back to life with specialized GSE. To go to Ni-Cads would need certification of the entire battery and charging system. From what we hear, it is not in the works to go Ni-Cad for now.

Quoting 747classic (Reply 9):
- How many Litium-ion batteries are in total installed in the 787 ? Three (3) are known to me up to now.

4 sets of Li-ion batteries on the 787, Main aircraft and APU batteries- 1 each, 2 total. Flight Control Bus Batteries 2 total. Battery packs for wireless emergency light units supposedly 30 total, size of laptop batteries. DFDR box battery, 1 for each of 2 boxes. Believe this is the total.

Other emergency batteries that were formerly Ni-Cd – EPAS door assist, fuel spar shutoff valves, etc. – have been replaced on the 787 with capacitors.

Quoting hivue (Reply 10):
But there remains the major issue of whether any NiCad solution that could possibly be made to fit could also meet the 787's power requirements. In the Boeing video cited in other posts in other threads Mike Sinnett says Li-Ion was not chosen to save weight (i.e., for its size) but because of power requirements.

Power output of a much smaller and lighter battery Li-Ion versus Ni-Cad.

Quoting JoeCanuck (Reply 16):
The 787 battery is nominal 30v, 65Amp/hr, (with a normal operating range of between 20v and 30v) and the 777 battery is 28v, 50Amp/hr capacity. You basically have to add 30% more cells, (which means 30% larger size as well), to get the same capacity as the 787 batter...but I have no idea about the size and weight.

We have been told long ago that a comparable Ni-Cad battery would be 3 times the size, and weight, of a 777 battery.

Quoting Stitch (Reply 18):
Is the current provided at airplane power-up an issue? Per a Boeing presentation, the 787 battery can provide 150A while the 777 battery provides 16A.

Looking at some battery check outs of a 777 battery, a discharge current of 47 Amps is used with a test box.

Quoting JoeCanuck (Reply 16):
I'm having a heck of a time digging up the physical dimensions of the 777 battery pack, but individual cells don't really care how they're stacked so a pack could probably be built that would fit on the 787 battery rails, but probably stick out further, or be a bit taller.

As reported toi us, the 777 is twice as tall with approx the same footprint of the 787 battery. Twice as heavy too.

Quoting hivue (Reply 19):
I suspect that the electric brakes pull a lot of amps.

Essential electrical power provided by 787 main ship battery does not supply power for cabin pressure, wing and engine anti-ice, or any other pneumatic system. Rather, most of the battery power (a full 50 Ah of the total nominal 65 Ah) must be conserved for the electric/electronic brakes.

Quoting CARST (Reply 31):
Some people said that NiCd batteries have a slightly varying power output what could destroy components which are not made for this varying power inputs. LIon batteries have a more stable power output, could this be the reason?

Yes.

787 main ship battery (65 Ah nominal) has the capacity to provide essential power for only 5-15 minutes (depending on condition of battery), which is intended to allow time for pilots either (a) to re-start engine(s) or (b) to deploy RAT.

"According to the manufacturer, there is no going back to a Ni-Cd battery on the 787, as it would weigh 3 times as much as a 777 main/APU battery in order to be able to meet the 787’s massive electrical demand." This was stated a while ago.
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RE: B787 Grounding: Tech/ops Thread Part 2

Tue Mar 12, 2013 6:28 pm

Quoting CARST (Reply 31):

I think there has to be another reason...

The reason could be as simple as the certification process. Even using a certified chemistry, the charging system and application usage is different so it may actually take years to certify a NiCd battery pack.

The 787 battery has been certified for the plane, (having gone through years of the various tests), and the battery can supply the power required by the 787 for all tested scenarios.

The only glitch, (and it is kind of a biggie), is the failure mode where the thing self immolates. My guess is that they assumed that they would find a root cause and be able to eliminate it, showing one and all that the problem is solved.

Now, after months of testing by a plethora of agencies and labs, they still can't find a root cause...and that's the real problem with getting the batteries recertified. That may be why Boeing is going with the safety box route.

What is very easy to forget is that any battery can burn or explode under the right conditions. Boeing has to create their safety box in such a way that those conditions either cannot or are very unlikely to occur...AND.....if they do occur, no harm will come to the plane.

A safety box with each cell physically isolated from the others in its own fireproof chamber so one runaway won't light up the entire pack. A more robust case that can withstand a bomb, much less a burning battery. (The current case actually held up remarkably well considering it is little more than a tin box). As well, I'd add some active cooling to each cell chamber, possibly using Peltier elements...much like one of those nifty 12v camping coolers...or maybe its own air conditioning unit.

If you think about it, that's not much different than the fuel tanks. In the wings, you carry around thousands of gallons of a very volatile liquid, and it's kept from catching fire simply by containment.

So after scratching my head, the only reason I can think of for so doggedly sticking with these batteries, (which doesn't mean it's the right one...I may just have a limited imagination), is the problem of certifying an interim solution. I suspect any temporary one would have to be certified just as rigorously as the permanent solution, since you never know how long it will take for the final fix to go into service.
What the...?
 
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RE: B787 Grounding: Tech/ops Thread Part 2

Tue Mar 12, 2013 8:12 pm

What exactly do people imagine happens when for example the Japanese or Chinese authorities will not accept a lithium ion solution even if the FAA does. The bigger part of the coming B 787 fleet will be registered somewhere outside the USA.
The FAA told Cessna to replace the lithium/ion battery with a lead acid or Ni/Cad battery in the Citation C14.
That was about 15 month ago after one battery fire. The FAA decided that the lithium ion battery made the air-plane an unsafe product. The aircraft were grounded until the batteries were replaced.
The battery were replaced (they surely had to exchange charges and computer programs) and it started flying again.
So that is something that seems to be possible to do.
I know that the B 787 is far more complex than any business jet, but Boeing has also many more engineers to throw at such a problem than Cessna.

I know that a new containment is a faster solution than a battery change, but I am afraid of the influence on ETOPS for the B 787.

I do not see why a chemistry change to a different kind of lithium/ion battery should be faster in certification than moving to the trusted and in multiple forms certified Ni/Cad, a solution the certifying authorities have long experiences with.

I thing that all the talk about it being impossible to move to Ni/Cad is hype, apart from leading to a hefty weight penalty.
If there are real technical reasons name them.
A battery is a battery if you need more voltage put more cells in series, if you need more capacity, place more series of cells in parallel, if you need a constant voltage for a bus over the discharge of the battery, go to higher battery voltage and regulate it down. All this solutions of course add weight.
But what does this weight increase really matters if it gets the B 787 in the air and again?

I am afraid that dithering will lead to an extended grounding of the B 787, what at least I would not like to see.
 
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RE: B787 Grounding: Tech/ops Thread Part 2

Tue Mar 12, 2013 9:03 pm

The FAA has given Boeing permission to move forward with their proposed fix.

Quote:
The Federal Aviation Administration (FAA) today approved the Boeing Commercial Airplane Company's certification plan for the redesigned 787 battery system, after thoroughly reviewing Boeing's proposed modifications and the company's plan to demonstrate that the system will meet FAA requirements...

...The FAA will approve the redesign only if the company successfully completes all required tests and analysis to demonstrate the new design complies with FAA requirements. The FAA's January 16, 2013 airworthiness directive, which required operators to temporarily cease 787 operations, is still in effect, and the FAA is continuing its comprehensive review of the 787 design, production and manufacturing process.
 
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RE: B787 Grounding: Tech/ops Thread Part 2

Tue Mar 12, 2013 9:04 pm

FAA Press Release:

The Federal Aviation Administration (FAA) today approved the Boeing Commercial Airplane Company’s certification plan for the redesigned 787 battery system, after thoroughly reviewing Boeing’s proposed modifications and the company’s plan to demonstrate that the system will meet FAA requirements. The certification plan is the first step in the process to evaluate the 787’s return to flight and requires Boeing to conduct extensive testing and analysis to demonstrate compliance with the applicable safety regulations and special conditions.

.....

The battery system improvements include a redesign of the internal battery components to minimize initiation of a short circuit within the battery, better insulation of the cells and the addition of a new containment and venting system.

.....

The certification plan requires a series of tests which must be passed before the 787 could return to service. The plan establishes specific pass/fail criteria, defines the parameters that should be measured, prescribes the test methodology and specifies the test setup and design. FAA engineers will be present for the testing and will be closely involved in all aspects of the process.

The FAA also has approved limited test flights for two aircraft. These aircraft will have the prototype versions of the new containment system installed. The purpose of the flight tests will be to validate the aircraft instrumentation for the battery and battery enclosure testing in addition to product improvements for other systems.


[Edited 2013-03-12 14:40:54]
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RE: B787 Grounding: Tech/ops Thread Part 2

Tue Mar 12, 2013 9:18 pm

Quoting mjoelnir (Reply 37):
The battery were replaced (they surely had to exchange charges and computer programs) and it started flying again.
So that is something that seems to be possible to do.

The cj-4 batteries are a different chemistry than the ones in the 787, but they are Li-ion. They chose to go with LiFePo4.
What the...?
 
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RE: B787 Grounding: Tech/ops Thread Part 2

Tue Mar 12, 2013 10:00 pm

Quoting Kaiarahi (Reply 39):
The battery system improvements include a redesign of the internal battery components to minimize initiation of a short circuit within the battery, better insulation of the cells and the addition of a new containment and venting system.

There are 3 things being done here - 2 are clear.

One frustrates me because I'm unclear if precise precise usage of the term cell and battery is being observed.

Specifically, the
'redesign of the internal battery components to minimize...'

I think this refers to the battery - as a whole, the device installed in the aircraft - not the cells. In other words -changes to the structure connecting the cells together and holding the cells. But it could be that it means there are some modifications to the internals of the cells themselves.

Does anybody have an authoritative source on this distinction. Are the cells being changed internally, or not.

That would be interesting because it would signify that some detail about the failure mode inside the cells was understood.

And please - do not turn this into the civ thread - I'm seeing way to much of that here already.
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RE: B787 Grounding: Tech/ops Thread Part 2

Tue Mar 12, 2013 10:28 pm

Quoting rcair1 (Reply 41):
Are the cells being changed internally, or not.

This quote from Conner suggests no:

"” Enhanced production and testing includes more stringent screening of battery cells prior to battery assembly. Operating improvements focus on tightening the system’s voltage range."

More like only selecting 3 stars ping pong balls as opposed to using 1 star balls - all come from the same batch, just select the one that meet more stringent requirements.

But I'm no authoritative.

bt
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RE: B787 Grounding: Tech/ops Thread Part 2

Tue Mar 12, 2013 10:54 pm

Quoting rcair1 (Reply 41):
One frustrates me because I'm unclear if precise precise usage of the term cell and battery is being observed.

Specifically, the
'redesign of the internal battery components to minimize...'

I think this refers to the battery - as a whole, the device installed in the aircraft - not the cells. In other words -changes to the structure connecting the cells together and holding the cells. But it could be that it means there are some modifications to the internals of the cells themselves.

I have no authoritative source.

However, NTSB/JTSB examination and testing has included the cells, connecting bars, BMU, BCU, and APU controller. The BCU and APU controller were "cleared" in NTSB releases. Both are outside the battery case. The cell and connecting bar degradation on the failed batteries has been examined and described in detail in NTSB releases. However, very little has been said about BMU testing, despite several weeks spent by NTSB and JTSB staff at Kanto (the BMU manufacturer). The BMU is inside the battery case.

Given that the FAA surely (at least by now) appreciates the difference between "battery" and "cell", I would tend to interpret "internal battery components" as anything inside the battery case, including the BMU and the cells themselves.
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JoeCanuck
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RE: B787 Grounding: Tech/ops Thread Part 2

Wed Mar 13, 2013 12:21 am

Quoting rcair1 (Reply 41):

It sounds to me like 'cell' refers to each of the 8 battery power units. It looks like they plan to insulate between the cells to prevent one runaway from taking down the whole battery pack. I think for the cells themselves, the answer is to get even pickier with quality control.

All of these changes make good sense. I wonder how much testing will be enough? I imagine they will be bench testing the hell out of those cells as well as flight testing.
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RE: B787 Grounding: Tech/ops Thread Part 2

Wed Mar 13, 2013 8:29 pm

I'm interested in the mechanics of putting a vent to the outside in the battery compartment. (Into both compartments, I assume.) Is this commonly done, putting a valved vent through the skin? Is there anything new that will have to be developed? Is there anything new and unusual when doing it through CFRP? Is this CFRP work something that can be done by airline maintenance out in the field, or will planes have to be brought back to Boeing for the work? (And just how do you cut a hole in the skin, anyway? I assume that it requires more than just a hole saw.) How is the valve to be controlled? Are battery compartments air-tight, or will they have to be reinforced?

Inquiring minds want to know ...  
 
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RE: B787 Grounding: Tech/ops Thread Part 2

Wed Mar 13, 2013 8:50 pm

Quoting bellancacf (Reply 42):
Is this commonly done, putting a valved vent through the skin?

Yes, the lower lobe have these vents to dump air overboard. They are dumpling air all the time. Re-routing the air over the battery and dumping it to an existing vent or a new one would be most logical. As for the hot exhaust from any potential battery fire, they may have to bond on a metal sheet near the area of the vent to prevent damage to the skin.

Quoting bellancacf (Reply 42):
Is this CFRP work something that can be done by airline maintenance out in the field, or will planes have to be brought back to Boeing for the work? (

Probably can be done in the field. They can probably do it when they install the supporting brackets for the new containment box.

Cutting into CFRP require a little more care than regular aluminum, but it can be done and Boeing has already demonstrated it with composite repair demo for the 787.

Quoting bellancacf (Reply 42):
I assume that it requires more than just a hole saw.

Maybe a hole saw and a holding fixture.



bt

[Edited 2013-03-13 13:52:03]
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cornutt
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RE: B787 Grounding: Tech/ops Thread Part 2

Thu Mar 14, 2013 12:49 am

Quoting bikerthai (Reply 43):
Cutting into CFRP require a little more care than regular aluminum, but it can be done and Boeing has already demonstrated it with composite repair demo for the 787.

My understanding is that the main thing you have to do is seal or bond the cut edges so it doesn't de-laminiate there in the future. They do this sort of thing with race cars all the time.
 
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RE: B787 Grounding: Tech/ops Thread Part 2

Thu Mar 14, 2013 12:05 pm

I'm surprised this hasn't been mentioned yet. Boeing will be webcasting a technical briefing on the battery changes. Thursday 6pm US Pacific time, 9pm eastern. Link here
 
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RE: B787 Grounding: Tech/ops Thread Part 2

Thu Mar 14, 2013 1:07 pm

Quoting cornutt (Reply 44):
My understanding is that the main thing you have to do is seal or bond the cut edges so it doesn't de-laminiate there in the future. They do this sort of thing with race cars all the time.

This works fine for race care because the life cycle of the frame is limited and it does not have the delta pressure as seen by an airplane fuselage. For a hole in the 787, even if you use the sharpest cutting tool, you will always expect cracks and micro delamination at the cut edges. Sealing will prevent moisture from getting into the crack (and freeze causing additional delamination). However, most likely they will put some sort of bolted and/or bonded doubler around the cutout so any crack growth would be arrested by the bolt clamp-up.

bt
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Kaiarahi
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RE: B787 Grounding: Tech/ops Thread Part 2

Thu Mar 14, 2013 3:29 pm

Tom and/or CM explained the process in one of the civav threads. Unfortunately, they've both left.

I wonder if they'd even need new vent holes, or if the existing ones could be adapted.

Edit: Found it - Reply 136 in the previous Tech/Ops thread. Titanium doubler plates.

[Edited 2013-03-14 08:41:32]
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humanitarian
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RE: B787 Grounding: Tech/ops Thread Part 2

Thu Mar 14, 2013 3:40 pm

Installing the vent should be routine for an experienced sheet-metal mechanic trained in CFRP. Speaking generally: drill a hole, install a doubler with sealant and then rivet. From what I have read the batteries will be a simple change out using the existing footprint and hardware. They should be able to finish this mod in one shift. BTW, I thought they were going to tap into an existing vent?

These planes will be in the air sooner then people think assuming the tests go well which I suspect they will. I would not be surprised to learn that Boeing has already tested their modified battery to fail on the ground and found it passed. They would have shown that data to the FAA and which agreed to the test flights as the final step.

While the political leaders at the USDoT dithered over this whole fiasco, there was nothing preventing Boeing from performing tests on the proposed modifications. They do not need FAA permission for any tests as long as flights were not involved and don't forget they have been building the new battery boxes for at least a month in anticipation of that approval.
 
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RE: B787 Grounding: Tech/ops Thread Part 2

Thu Mar 14, 2013 4:29 pm

Quoting dynamicsguy (Reply 45):
Boeing will be webcasting a technical briefing on the battery changes.

And from Tokyo.    I guess that makes PR/marketing sense as JAL and ANA are the most affected airlines and Yuasa is the battery cell manufacturer.
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