777ER
Crew
Topic Author
Posts: 9855
Joined: Fri Dec 19, 2003 5:04 pm

FAA Grounds 787, Part 11

Sun Feb 24, 2013 4:35 am

Link to thread #10 FAA Grounds 787, Part 10 (by 777ER Feb 17 2013 in Civil Aviation)#menu209

WARNING: Due to thread 9 going off topic quickly and turning into a 'battle ground', the moderators will be watching this thread frequently and ANY offending/rule breaking posts will be removed. Please respect each others right to have their opinion.
Head Forum Moderator
moderators@airliners.net
 
User avatar
PW100
Posts: 2731
Joined: Mon Jan 28, 2002 9:17 pm

RE: FAA Grounds 787, Part 11

Sun Feb 24, 2013 5:05 am

OK. Recap:

The Nr.1 reason FAA issued the AD (which in effect grounded the 787 fleet) was the fact that Boeing had earlier claimed/demonstrated to a satisfactory level in the design certification, that such an event (battery thermal runaway) would happen less than once in a million hours. Once such an event happened twice in 50,000 hours, or less than two weeks apart, the whole certification basis of the 787 Type Certificate fell away, and the FAA had no other option.

Basically, the AD says Boeing has to redo this part of the design certification, and demonstrate how they will meet their earlier claims, and more importantly, how they can prove their assumptions. And you can count on it that this time there will be a lot more scrutiny than the first time around, when Boeing had a significant level of “delegated authority” to sort of self-demonstrate that the design met certification standards.

Friday 22 Feb 2013 Boeing presented an action plan to the FAA:

Boeing remains tight-lipped about its proposed fix, but according to multiple sources, it includes:
• A stronger, sealed containment box enclosing the eight battery cells;
• A system of venting tubes that in case of an incident would channel any flammable vapors or liquids directly out of the airplane;
• Continuous monitoring of temperature and voltage of individual cells within the battery;
• Better thermal separation of the cells, with some barrier such as high-temperature glass inserted between them.


Good luck to Boeing, and hope to see many 787 contrailing the skies soon!
Immigration officer: "What's the purpose of your visit to the USA?" Spotter: "Shooting airliners with my Canon!"
 
PHX787
Posts: 7877
Joined: Thu Mar 15, 2012 7:46 pm

RE: FAA Grounds 787, Part 11

Sun Feb 24, 2013 5:16 am

Ok I really would like to follow and contribute to this thread as much as I possibly can. I have a plethora of news that keeps getting posted on Japanese websites, but I find it quite difficult for me to post because of how quickly these threads get out of control. I want to second 777ER's post here, and I would like to add thread 7 and 8 went out of control to become a battle ground as well.

Quoting 777ER (Thread starter):
WARNING: Due to thread 9 going off topic quickly and turning into a 'battle ground', the moderators will be watching this thread frequently and ANY offending/rule breaking posts will be removed. Please respect each others right to have their opinion.

We're 11 threads in with actually little progress into the fix, besides the "temporary" fix that B calls "permanent." Let's focus this time on keeping these things news-oriented. Here's something I see.....

Quoting PW100 (Reply 1):
Basically, the AD says Boeing has to redo this part of the design certification, and demonstrate how they will meet their earlier claims, and more importantly, how they can prove their assumptions. And you can count on it that this time there will be a lot more scrutiny than the first time around, when Boeing had a significant level of “delegated authority” to sort of self-demonstrate that the design met certification standards.

What is Boeing seeing with this fix?
What is this fix-- layman's terms?
How much testing will this require
When will the 787, then, get off the ground again?
Follow me on twitter: www.twitter.com/phx787
 
Gemuser
Posts: 4301
Joined: Mon Nov 24, 2003 12:07 pm

RE: FAA Grounds 787, Part 11

Sun Feb 24, 2013 6:07 am

Quoting PW100 (Reply 1):
Once such an event happened twice in 50,000 hours, or less than two weeks apart, the whole certification basis of the 787 Type Certificate fell away,

This is a gross exaggeration! The "whole basis ... Type Certification" did not fall away. It still stands and is valid. What did happen was the two events in 50,000 hours called in to question compliance with one of the special conditions, which have been discussed to death in these threads. That's why the AD was issued. The problem is NOT a threat to the type certification, just one item, out of thousands.
Of course that one item was enough for the FAA to issue a "before further flight" AD, which is their right & proper role.

Gemuser
DC23468910;B72172273373G73873H74374475275376377L77W;A319 320321332333343;BAe146;C402;DHC6;F27;L188;MD80MD85
 
sweair
Posts: 1816
Joined: Sun Nov 20, 2011 9:59 am

RE: FAA Grounds 787, Part 11

Sun Feb 24, 2013 6:56 am

What did the two events have in common? If we would venture on a guess? Prior to thermal runaway they were running the APU? Was there any drain on the batteries in both events?
 
jporterfi
Posts: 463
Joined: Sat Feb 25, 2012 6:25 am

RE: FAA Grounds 787, Part 11

Sun Feb 24, 2013 8:31 am

Quoting PHX787 (Reply 2):
What is Boeing seeing with this fix?

I may be ridiculed for saying this, but I truly believe that Boeing thinks this fix (coupled with necessary modifications to it that the FAA requires before re-certifying the 787) is permanent. Therefore, I think that Boeing is seeing whether the fix will sufficiently contain any thermal runaway, and prevent is from damaging the aircraft outside of the containment box.

Quoting PHX787 (Reply 2):
What is this fix-- layman's terms?

Essentially it is a stronger containment box made out of steel or titanium, as well as a thicker layer of insulated separator (not sure what material) between the cells. I believe the idea is to keep any thermal runaway from spreading to multiple cells and/or out of the battery.

Quoting PHX787 (Reply 2):
How much testing will this require

Someone on another thread mentioned hte batteries would need to be tested to the point of failure, but I hardly see the point in that much testing. An interesting idea that was previously mentioned is conducting a test flight, then mid-flight, inducing thermal runaway in one cell of a battery and seeing if it spreads to other cells or outside of the containment box (most likely within a certain amount of time).

Quoting PHX787 (Reply 2):
When will the 787, then, get off the ground again?

I think it is far to early to tell. We at least need to wait and see if/when the FAA and NTSB approve Boeing's proposal before more educated speculation can commence.
 
AeroWesty
Posts: 19551
Joined: Sat Oct 30, 2004 7:37 am

RE: FAA Grounds 787, Part 11

Sun Feb 24, 2013 8:58 am

Quoting jporterfi (Reply 5):
I think it is far to early to tell. We at least need to wait and see if/when the FAA and NTSB approve Boeing's proposal before more educated speculation can commence.

A lot of these questions are answered in the Seattle Times article linked above. In regards to testing and return to service, it notes a couple of interesting things:

Quote:

What’s unclear is how much testing the FAA will require to validate the safety of the revamped battery.

Barnett said the tests conducted on the batteries by Boeing during the original certification process — baking the battery in an oven, puncturing it with a nail, crushing it, and overcharging it — are standard industry tests but don’t reflect what typically happens when a battery fails due to an internal short circuit.

...

And the FAA will want thorough testing of Boeing’s fix, he said.

“The last thing the FAA can stand is to fast-track this and then have something else go wrong,” Hamilton said.

...

A further uncertainty, he said, is that 24 of the 50 Dreamliners that are grounded worldwide are operated by just two Japanese airlines.

Whatever the FAA decides, the Japan Transport Safety Board is expected to be conservative in allowing those jets to fly.
International Homo of Mystery
 
B777LRF
Posts: 1435
Joined: Sun Nov 02, 2008 4:23 am

RE: FAA Grounds 787, Part 11

Sun Feb 24, 2013 9:55 am

So what Boeing's essentially proposing is something along the lines of "We don't know what happened to the battery, so we can't stop it from happening again. If it does catch fire, here's a solid box to drop it in, a couple of vent tubes and a few extra lines in the QRH for the boys at the sharp end. Job jobbed, can we go back flying again please"?

The whole idea of "let 'er burn, containment will do" as the sole and final fix is utterly perplexing, runs contrary to everything the safety standards of aviation embrace, and should not be allowed to stand.

If the FAA has just a smidgen of testicular fortitude, they'll tell Boeing to sod off and come back when they've got a battery system to present that's no more liable to combustion than "industry best practice". Whether that can be done with Li-Ion, NiCad's or something else is besides the point. And if the FAA won't do it, one hopes there are other NAA's out there who won't be afraid to say "sorry, not on my watch" and thus scuttle this half-baked, non-conforming, abortion from taking flight.
From receips and radials over straight pipes to big fans - been there, done that, got the hearing defects to prove
 
XT6Wagon
Posts: 2637
Joined: Tue Feb 13, 2007 4:06 pm

RE: FAA Grounds 787, Part 11

Sun Feb 24, 2013 10:25 am

Quoting B777LRF (Reply 7):
The whole idea of "let 'er burn, containment will do" as the sole and final fix is utterly perplexing, runs contrary to everything the safety standards of aviation embrace, and should not be allowed to stand.

no it isn't. Lots of things on an airplane are allowed to break. If we use your critera no aircraft would ever fly as engines break more than never. Lets be more blunt. The battery is a back up for *6* units any 2 of which keeps the plane fully powered as far as safety goes. The 4 generators on the engine would all have to offline in one very short event to keep the APU 2 generators from being online. In such a case the batteries would be needed as a bridge between main power system failure and APU start. We are getting into events that are extremely remote, and you can bet that any aircaft with a main battery failure would be diverting as soon as possible regardless of the cause of the failure.

So what Boeing is attempting to do is prove that only the battery would break in the case of thermal run-away. From my perspective they are already most of the way there as the current system clearly worked fine twice. So even better thermal management of the battery in thermal runaway coupled with external venting of the by-products is pretty much golden.
 
AngMoh
Posts: 739
Joined: Fri Nov 04, 2011 5:03 am

RE: FAA Grounds 787, Part 11

Sun Feb 24, 2013 11:02 am

Quoting XT6Wagon (Reply 8):
no it isn't. Lots of things on an airplane are allowed to break.

Yes they are allowed to break, but they are not allowed to go up in flames.

Quoting XT6Wagon (Reply 8):
Lets be more blunt. The battery is a back up for *6* units any 2 of which keeps the plane fully powered as far as safety goes. The 4 generators on the engine would all have to offline in one very short event to keep the APU 2 generators from being online. In such a case the batteries would be needed as a bridge between main power system failure and APU start.

The 787 did not get grounded because the batteries failed. The 787 got grounded because 2 batteries experienced thermal runaway at a rate significantly higher than predicted by the certification process. One resulted in a fire and in the other case the pilot made an emergency landing due to a suspected fire. Had they just failed to work, there would be no fire and no emergency landing and the 787 would not be grounded today.

Quoting XT6Wagon (Reply 8):
So what Boeing is attempting to do is prove that only the battery would break in the case of thermal run-away. From my perspective they are already most of the way there as the current system clearly worked fine twice. So even better thermal management of the battery in thermal runaway coupled with external venting of the by-products is pretty much golden.

Here I disagree strongly and even the FAA disagreed strongly in the Cessna Citation case. First thermal runaway should be extremely rare. Secondly, in the event it happens it should be harmless. And from my perspective, the current system did not work in both events. Boeing is not improving the thermal management as they admit they don't know what caused the thermal runaway. They only try to make the thermal runaway harmless. And here I think Boeing underestimates the degree that other parties will cover their butt. The FAA, being a government organisation, is not going to take any risks because they received enough criticism till now, and airlines are going to play it safe because they can not afford another smoking 787 in the news. Just look at how long it took for the media scrutiny the reduce after the QF32 incident: even today the day to day issues with A380s get blown up (see the Emirates "door blowout" news).
 
AA737-823
Posts: 4897
Joined: Wed Mar 01, 2000 11:10 am

RE: FAA Grounds 787, Part 11

Sun Feb 24, 2013 11:05 am

Quoting XT6Wagon (Reply 8):
The battery is a back up for *6* units any 2 of which keeps the plane fully powered as far as safety goes.

Any one of those *6* units can be MEL'd; the battery cannot. Further, it is fully required to be in full health for ETOPS operations, so at that point, you've got an ETOPS airplane that can't fly target missions, and realistically can't leave the ground.

Quoting B777LRF (Reply 7):
The whole idea of "let 'er burn, containment will do" as the sole and final fix is utterly perplexing, runs contrary to everything the safety standards of aviation embrace, and should not be allowed to stand.

Agreed; consequently, as we can all agree that it is NOT in Boeing's best interest to pay the costs of lawsuits after a fiery 787 crash, I am hoping like you are that BoCo has another plan.

Quoting B777LRF (Reply 7):
If the FAA has just a smidgen of testicular fortitude, they'll tell Boeing to sod off and come back when they've got a battery system to present that's no more liable to combustion than "industry best practice".

The FAA exerts testicular fortitude when and where they wish. We've seen them over-punish some, while simultaneously under-punishing others. But it may be a moot point; in the linked article above, it's reported that the JTSB has no interest in permitting the airplanes into their airspace until the root cause is known and exhausted.
 
sankaps
Posts: 1692
Joined: Fri Jan 04, 2008 6:51 am

RE: FAA Grounds 787, Part 11

Sun Feb 24, 2013 11:14 am

Quoting XT6Wagon (Reply 8):
. From my perspective they are already most of the way there as the current system clearly worked fine twice.

Unfortunately your perspective is not shared by the airlines involved, the FAA, the NTSB, most external technical experts, or even by Boeing's CEO McNerney. And there have been 10 threads which try to explain why the current system did not "clearly work fine twice". A system that works fine does not result in the scenes we saw with both the JAL and ANA incidents.

In a nutshell Boeing has two things to fix: Significantly reduce the probability of batteries failing in this manner, and improve the containment when the battery does fail. What they have proposed thus far is for the latter; they still do not have a solution for the former, as no one yet knows what caused the batteries to fail.
 
mjoelnir
Posts: 3932
Joined: Sun Feb 03, 2013 11:06 pm

RE: FAA Grounds 787, Part 11

Sun Feb 24, 2013 11:16 am

When a robust containment, I am not of the opinion the old one was working, vents directly outside, keeping flame, smoke and explosive gases from entering the e-bay there is one question left, what exactly is the function of the main battery in flight, can the B 787 live without it.

If it is only a backup for electrical generation, than I agree that electrical generation is pretty well covered, having two engines with four generators, apu and rat.

But somewhere in this thread, I am to lazy to find it, it was said that the main battery was a backup for the flight instruments in case of an electrical failure as opposed to a generating failure. That means electrical generation is okay, engines running, generators generating but some electrical fault is scrambling the electrics.
 
AndyEastMids
Posts: 1055
Joined: Wed Jan 24, 2001 10:24 pm

RE: FAA Grounds 787, Part 11

Sun Feb 24, 2013 12:18 pm

“...we won’t allow the 787 to return to commercial service until we’re confident that any proposed solution has addressed the battery failure risks,” said an FAA statement

To me this suggests that the FAA are not requiring Boeing to stop (or reduce the frequency of) batteries failing, but are only expecting Boeing to improve what happens when a battery does fail.
 
art
Posts: 2679
Joined: Tue Feb 08, 2005 11:46 am

RE: FAA Grounds 787, Part 11

Sun Feb 24, 2013 12:24 pm

Quoting XT6Wagon (Reply 8):
So what Boeing is attempting to do is prove that only the battery would break in the case of thermal run-away. From my perspective they are already most of the way there as the current system clearly worked fine twice.

To me the point is that the frequency of failure appears to be higher than that allowed, even if containment worked perfectly.

Quoting AngMoh (Reply 9):
The 787 did not get grounded because the batteries failed. The 787 got grounded because 2 batteries experienced thermal runaway at a rate significantly higher than predicted by the certification process.

Concur with your statement.

Quoting sankaps (Reply 11):
In a nutshell Boeing has two things to fix: Significantly reduce the probability of batteries failing in this manner, and improve the containment when the battery does fail.

Concur with your statement.

I hope Boeing can come up with an acceptable battery system (probability of failure / containment performance in case of failure) without it taking many months. They have not been lucky with this aircraft (although if you can make your own luck they did a bad job of doing that - premature rollout for silly reasons etc).
 
asctty
Posts: 132
Joined: Sat Dec 13, 2008 5:23 am

RE: FAA Grounds 787, Part 11

Sun Feb 24, 2013 1:01 pm

The thing for me is what is the purpose of the battery? If it is a safeguard against a failure of the normal electrical supply? What I have yet to see on any of these threads is what was the status of the battery that went on fire? Was is it on load, or was is it on stand-by? If it was on load did the pilots notice any loss of function? If it was on stand-by, lucky the pilots did not have to rely on it.
A containment will not fix the issue regarding the function of the battery. It will only stop the battery becoming another cause for a hazard, i.e. fire!
There are still many unanswered questions about this issue.
 
Rheinbote
Posts: 1103
Joined: Sun May 21, 2006 9:30 pm

RE: FAA Grounds 787, Part 11

Sun Feb 24, 2013 1:31 pm

Quoting mjoelnir (Reply 12):
But somewhere in this thread, I am to lazy to find it, it was said that the main battery was a backup for the flight instruments in case of an electrical failure as opposed to a generating failure.

The flight control electronics have their own dedicated back-up battery.
 
Wisdom
Posts: 179
Joined: Thu Apr 28, 2011 5:43 pm

RE: FAA Grounds 787, Part 11

Sun Feb 24, 2013 2:09 pm

Quoting XT6Wagon (Reply 8):
no it isn't. Lots of things on an airplane are allowed to break. If we use your critera no aircraft would ever fly as engines break more than never. Lets be more blunt. The battery is a back up for *6* units any 2 of which keeps the plane fully powered as far as safety goes. The 4 generators on the engine would all have to offline in one very short event to keep the APU 2 generators from being online.

This is not what you have the battery for. Batteries are not meant to be used as a transitionary power source.
When you lose one engine, you still have 2 gens and you start firing up the APU immediately (or the APU fires up automatically). You don't wait until the other engine quits and the probability of losing both engines is low (that's what she said... history says otherwise).


The battery is there to deal with a major electrical failure, such as one that could be caused by major short-circuiting, electrical arching, such as could be caused by a major lightning strike, maintenance error, FOD, etc.
These are situations wherein there is no power flowing from any generators, to the essential systems for flight, no matter whether the generators are or are not producing any power.

May I remind you that Boeing has had one similar incident with the 787 already, with the fire caused by FOD on the P100 panel, resulting in cascading electrical failures, and ended up with battery providing power to the essential busbar for the diversion.

Quoting PW100:
First you write that the battery will have to feed the critical systems for the full duration of the diversion:

Quoting Wisdom (Reply 229):
No that's not what a battery is for. The battery is supposed to hold up critical systems for the duration of the diversion in case of an electrical failure. That is standby instruments, a navigation display and if possible, DC pumps to charge the accumulators (electric braking in the 787's case).

5.5 hours is tight on a 2kwh battery

And then you state that the battery will only need to provide power for 10 seconds:

Quoting Wisdom (Reply 229):
An APU takes 10 seconds to fire-up, if other gens are online you don't need the main battery to power anything at all, I don't see why you would fly with any of the 4 engine gens offline on something as hungry on electricity as the 787. So even if you lose an engine, you'd still have 2 gens providing electricity to the essential busbars as their first priority

BTW How do you envision a 5.5 hr glide . . . ? You mean the aircraft will fly for 5.5 hrs without any electrical power generation?

As long as engines are running, you’re pretty much guaranteed to have at least one generator on-line**. If not, then there is the APU gen that will come on-line within a minute or so. If not, then there is the RAT-gen, which surely will provide more accumulated power than a battery can provide over a 5.5 hour period.

** Not to mention that as soon as one engine fails (or even one generator, I think) the APU will be started, which brings and additional two generators on-line.

Quoting Wisdom (Reply 229):
As to the RAT, if it gets that far, ie no generation at all, a battery is a welcome addition. The RAT will have its hands full providing power to the hydraulics, if it works that is. The RAT is, like the battery, a system of last resort. However, the rat is not something that you use on a daily basis so you don't know if it works until it deploys and starts feeding your systems

The RAT also drives a generator. I would tend to believe that there is a good reason Boeing added the weight of a RAT driven generator . . . And the RAT system is very simple, and thus pretty pretty reliable, I would expect.

So the APU and eventually the RAT will take care of your bad day. The battery will cover the delay in getting one of these on-line. And the battery will stop the aircraft at roll-out once airspeed drops below 60 knots or so - above that speed the RAT-gen still provides sufficient power for the electric brakes.

Quoting Wisdom (Reply 229):
Braking doesn't take as much as one would think, once the brakes are engaged, there is barely any power required unless released and reapplied

I find this interesting. I'm not disputing. It is just that I would expect that a significant force would be required to pull the brake discs together. Doing this electrically will require a significant current draw to generate the required EMF force. I did not expect that engaging the brakes will require more current than keeping them engaged.
I can see that what you are saying would apply to hydraulic actuation, but I did not expect that from electrical actuation. I would appreciate if you could provide more insight.

See above.
Again, you're focusing too much on the engine failure scenario.

The battery is not there for an engine failure scenario that would result in partial loss of electrical generation, they are there as a back-up for a major main electrical system failure.

In an aircraft, wires run in bundles and are situated in places that are inaccessible or impossible to inspect. If such bundles chafe against a sharp edge, it could uncover insulation, start a major short-circuit or paired with moisture and Kapton even start an electrical fire that could cascade into multiple electrical failures, in the worst case scenario even a total loss of the AC electrical systems.

All this while all engines are running, and all gens are online (in reality the gens will automatically go on standby).

In such scenario, the RAT is not really useful and I'm not even sure that it would deploy (depends on individual aircraft type's architecture).

Remember that ETOPS ratings are diversion times at one engine cruise speeds/altitudes. So in most scenario's on conventional airliners where you have an electrical failure but still have engines, you would be less than 5.5 hours away from your diversion airport.

The only tricky thing about the B787 is that it runs the A/C and pressurisation on AC electricals. So as I said in the past weeks, a total AC electrical failure would require the B787 to fly a diversion (with both engines) at a low sustainable breathing altitude for the passengers of around 14000 feet, which will result in lower speed and higher fuel burn.

In light of this, I'm not sure that the one-engine out scenario would result in higher fuel consumption than the AC electricals failure scenario, I hope that Boeing and the FAA took that into consideration during certification.

Even worse would be a single engine failure with a total AC electricals failure.
You would need to fly on one engine at 14.000 feet, I hope that that is a scenario that they have taken into account during certification.

[Edited 2013-02-24 06:14:36]
 
Wisdom
Posts: 179
Joined: Thu Apr 28, 2011 5:43 pm

RE: FAA Grounds 787, Part 11

Sun Feb 24, 2013 2:37 pm

Regarding your question about electric braking:

Looking at the picture of the brake assembly (just google it), it looks to me like it's just the hydraulic pistons which press the rotors and stators together to create the braking effect, that have been replaced by electric actuators. Once the actuators are activated the power to maintain the m actuated should be minimal as most of the load will be absorbed by the threads of the screws of the actuator.

Be reminded that emergency braking usually activates only select brake assemblies, meaning that you don't have full control of braking/steering.

The UA497 is a recent event wherein a A320 lost all AC power due to an electric fire, they returned on the batteries and the RAT.
see http://avherald.com/h?article=43a6bc08

Even though the batteries didn't provide sufficient power for a completely controlled stop, everybody walked away.
Batteries are the electric back-up system of last resort, on which a pilot should be able to rely even on the worst of days.

That's what batteries are for.

[Edited 2013-02-24 06:39:35]
 
User avatar
Revelation
Posts: 13827
Joined: Wed Feb 09, 2005 9:37 pm

RE: FAA Grounds 787, Part 11

Sun Feb 24, 2013 2:51 pm

Quoting PW100 (Reply 1):
Continuous monitoring of temperature and voltage of individual cells within the battery

Interesting how the word "monitoring" is used. In the last thread a poster was implying that the BMS could also take an individual cell offline, but I see no evidence of that in the public statements. The existing "special conditions" says the battery charger needs to be able to be disconnected from the battery but nothing about isolating an individual cell as far as I can determine.

Quoting jporterfi (Reply 5):
An interesting idea that was previously mentioned is conducting a test flight, then mid-flight, inducing thermal runaway in one cell of a battery and seeing if it spreads to other cells or outside of the containment box (most likely within a certain amount of time).

They'd never do that in air, they'd do it in an enviornmental simulator.

Quoting AeroWesty (Reply 6):
"The last thing the FAA can stand is to fast-track this and then have something else go wrong," Hamilton said.

That's in essence what I said in the previous thread and got a lot of push-back on it. Actually I said Boeing could not stand such a scenario, but the idea is the same.

Quoting B777LRF (Reply 7):
The whole idea of "let 'er burn, containment will do" as the sole and final fix is utterly perplexing, runs contrary to everything the safety standards of aviation embrace, and should not be allowed to stand.

To be the devil's advocate, and to echo what was said in the last thread, this is how engine blade containment works. The issue we both have is that Boeing is amazingly mute about what they are doing to address the single cell failure issue.

Quoting AngMoh (Reply 9):
Boeing is not improving the thermal management as they admit they don't know what caused the thermal runaway. They only try to make the thermal runaway harmless. And here I think Boeing underestimates the degree that other parties will cover their butt. The FAA, being a government organisation, is not going to take any risks because they received enough criticism till now, and airlines are going to play it safe because they can not afford another smoking 787 in the news.

I think I see FAA manuevering for a climb-down. I don't know to what degree the other players are going to go along.

Quoting AA737-823 (Reply 10):

The FAA exerts testicular fortitude when and where they wish. We've seen them over-punish some, while simultaneously under-punishing others. But it may be a moot point; in the linked article above, it's reported that the JTSB has no interest in permitting the airplanes into their airspace until the root cause is known and exhausted.

Yes, that could be how it plays out. It seems JTSB were the ones who visited the firm that manufactures the cells. Perhaps they are the ones taking the lead on investigating the single cell failures?

Quoting sankaps (Reply 11):
In a nutshell Boeing has two things to fix: Significantly reduce the probability of batteries failing in this manner, and improve the containment when the battery does fail. What they have proposed thus far is for the latter; they still do not have a solution for the former, as no one yet knows what caused the batteries to fail.

We are being told that the root cause for these instances of cell failure might never be known because the evidence has been consumed by fire. I imagine there's a list of suspected root causes and relative probabilities based on the evidence, but it's hard to force an action based on this, IMHO. Still, I'm quite concerned that we aren't being told what is going to be done to address the more probable root causes.

Quoting AndyEastMids (Reply 13):
“...we won’t allow the 787 to return to commercial service until we’re confident that any proposed solution has addressed the battery failure risks,” said an FAA statement

To me this suggests that the FAA are not requiring Boeing to stop (or reduce the frequency of) batteries failing, but are only expecting Boeing to improve what happens when a battery does fail.

Yes, this is a big part of why I think I see FAA manuevering for a climb-down. It's hard to reconcile 10,000% safe with that statement, though.
Inspiration, move me brightly!
 
sankaps
Posts: 1692
Joined: Fri Jan 04, 2008 6:51 am

RE: FAA Grounds 787, Part 11

Sun Feb 24, 2013 2:57 pm

Quoting Revelation (Reply 19):
To be the devil's advocate, and to echo what was said in the last thread, this is how engine blade containment works.

Revelation, that is true. However I am sure there are, in parallel, certain agreed to numbers for what acceptable engine blade failure rates are; if it were happening at what is feared to be 20x the expected rate and containment too was not working exactly as hoped, then it is highly likely the said engines would be grounded too.
 
pugman211
Posts: 194
Joined: Thu Dec 20, 2012 1:55 pm

RE: FAA Grounds 787, Part 11

Sun Feb 24, 2013 3:08 pm

Quoting Wisdom (Reply 18):
Even though the batteries didn't provide sufficient power for a completely controlled stop, everybody walked away.
Batteries are the electric back-up system of last resort, on which a pilot should be able to rely even on the worst of days.

That's what batteries are for.

So long as your battery isn't on fire or bricked....
 
cornutt
Posts: 333
Joined: Sun Jan 20, 2013 6:57 am

RE: FAA Grounds 787, Part 11

Sun Feb 24, 2013 3:20 pm

Quoting B777LRF (Reply 7):
The whole idea of "let 'er burn, containment will do" as the sole and final fix is utterly perplexing, runs contrary to everything the safety standards of aviation embrace, and should not be allowed to stand.

But as I pointed out in the last thread, that's precisely how we handle blade failures in engines. It is not required to design an engine such that it is guaranteed to never throw a blade, nor does anyone know how to do so. We design containment into the engines.

Quoting Wisdom (Reply 17):
The battery is there to deal with a major electrical failure, such as one that could be caused by major short-circuiting, electrical arching, such as could be caused by a major lightning strike, maintenance error, FOD, etc.
These are situations wherein there is no power flowing from any generators, to the essential systems for flight, no matter whether the generators are or are not producing any power.

You're making assumptions about the architecture of the electrical system that are probably not true. First of all, if an essential bus is shorted, then it will still be shorted when the battery is placed on it. So that's no help. Second, there have to be at least two busses, or sets of busses, that are separate up to and including physically separated routing through the aircraft. You can't ever have a situation, battery or no battery, where a fire in one electrical tray takes out all of the electrical systems. I'm pretty sure that what you said about the ZA002 incident is not true; if memory serves they were able to start the APU and it provided power for the diversion. I think there are either three or four main busses. The captain and F/O instruments can probably be switched to at least two essential busses, and each essential bus can probably be switched to at least two different main busses. If what I've read is correct, the main battery is hard-tied to a single main bus. Lose that bus, you've lost the battery.

And as has been pointed out, the battery simply does not have enough capacity to power the aircraft in flight for five-and-a-half hours. Likely it does not enter into the ETOPS calculation at all.
 
a3xx900
Posts: 395
Joined: Sun Jan 18, 2004 8:03 pm

RE: FAA Grounds 787, Part 11

Sun Feb 24, 2013 3:27 pm

I don't know if this has been asked before and excuse me for not searching 11 topics and hundreds of replies for this, but:

Why can't airlines even reposition their aircraft (non-rev) to their home airports? E.g. the ANA 787 sitting in FRA and the JAL sitting in BOS?
Why is 10 afraid of 7? Because 7 8 9.
 
User avatar
Stitch
Posts: 23074
Joined: Wed Jul 06, 2005 4:26 am

RE: FAA Grounds 787, Part 11

Sun Feb 24, 2013 3:29 pm

Quoting a3xx900 (Reply 23):
Why can't airlines even reposition their aircraft (non-rev) to their home airports?

They can with the proper waivers. Evidently they are content to leave the planes where they are for whatever reason(s).
 
cornutt
Posts: 333
Joined: Sun Jan 20, 2013 6:57 am

RE: FAA Grounds 787, Part 11

Sun Feb 24, 2013 3:44 pm

Quoting a3xx900 (Reply 23):
Why can't airlines even reposition their aircraft (non-rev) to their home airports? E.g. the ANA 787 sitting in FRA and the JAL sitting in BOS?

They can, if they do the work to plan a ferry flight with the proper restrictions. In fact, I think that one or two of them have been moved. But right now there's really no motivation, since the airlines don't know what they are going to have to do or where the aircraft will need to be taken. (There's still the possibility, although it looks unlikely now, that they will all have to be flown back to Everett to be modified.) The airlines probably figure that for the time being, as long as the planes are in a place where they are secure and properly "winterized", there's no point in expending the fuel and crew hours to move them.
 
User avatar
par13del
Posts: 6678
Joined: Sun Dec 18, 2005 9:14 pm

RE: FAA Grounds 787, Part 11

Sun Feb 24, 2013 4:00 pm

Quoting Wisdom (Reply 17):
May I remind you that Boeing has had one similar incident with the 787 already, with the fire caused by FOD on the P100 panel, resulting in cascading electrical failures, and ended up with battery providing power to the essential busbar for the diversion.

It should also be mentioned that while on approach most essential systems were coming back online I believe independent of the battery, the experts can confirm, so that incident also showed the redundancies built into the system and that they did function as expected.
 
User avatar
RayChuang
Posts: 8005
Joined: Sat Jun 24, 2000 7:43 am

RE: FAA Grounds 787, Part 11

Sun Feb 24, 2013 5:09 pm

My guess is that Boeing should have a "safer" battery ready by late this summer, and eventually the 787 will go away from the current Li-On battery design to a new, far safer dry-electrode Li-On battery within the next few years.
 
sweair
Posts: 1816
Joined: Sun Nov 20, 2011 9:59 am

RE: FAA Grounds 787, Part 11

Sun Feb 24, 2013 5:15 pm

Too bad no fuel cell options are in the market, as Airbus told, it filled the cargo hold on their A320.. Isn´t there a market to design and build JetA fueled fuel cells for airliners? But what do you do with the waste heat?
 
Rheinbote
Posts: 1103
Joined: Sun May 21, 2006 9:30 pm

RE: FAA Grounds 787, Part 11

Sun Feb 24, 2013 5:33 pm

Quoting sweair (Reply 28):
Too bad no fuel cell options are in the market, as Airbus told, it filled the cargo hold on their A320.. Isn´t there a market to design and build JetA fueled fuel cells for airliners?

That kind of flying refinery would probably be even harder to certify than Lithium-Ion batteries.
 
User avatar
kanban
Posts: 3644
Joined: Sun Jan 06, 2008 1:00 am

RE: FAA Grounds 787, Part 11

Sun Feb 24, 2013 5:57 pm

So as we go into part 11, everybody from the airlines to the FAA, NSTB to Boeing are posturing through releases (leaked or otherwise) and many posters are trying to interpret the posturing. Bottom line, we don't know which line is the actual and which is posturing. Sometimes an agency will release a position the day before a congressional hearing just to defuse the hearing. So while they may not be lying, they may not be telling the whole story or using words in a different context than normal.

Personally I think the FAA will accept the Boeing plan with a token revision that shows they're in charge. Then Boeing will pursue revising the battery/battery chemistry/battery system with various manufacturers. The reason for the proposal to be labeled the ultimate fix may be that Yuasa can not adequately improve the cell chemistry or eliminate all contamination. New supplier's batteries may require more substantive electrical bay revisions and certification so developing them will take longer.

I believe that the Japanese are looking at the APU battery from that ANA plane where one cell showed deformation but no thermal run away.. there may be an answer coming there

As far as ETOPS/ battery functions, EE bay relationships, and fire propagation and extinguishing; please read the posts of Tdscanuck, CM, and Rcair1 .. they have stated plainly what is involved. We've had other vehement posters with do or die positions based on hearsay, opinion and fear.. While in a open forum all opinions are welcome, let's try to base them on fact.
 
User avatar
7BOEING7
Posts: 2357
Joined: Fri Oct 12, 2012 5:28 pm

RE: FAA Grounds 787, Part 11

Sun Feb 24, 2013 6:16 pm

Quoting Wisdom (Reply 17):
The only tricky thing about the B787 is that it runs the A/C and pressurisation on AC electricals. So as I said in the past weeks, a total AC electrical failure would require the B787 to fly a diversion (with both engines) at a low sustainable breathing altitude for the passengers of around 14000 feet, which will result in lower speed and higher fuel burn.

In light of this, I'm not sure that the one-engine out scenario would result in higher fuel consumption than the AC electricals failure scenario, I hope that Boeing and the FAA took that into consideration during certification.

During the 777-300ER certification Boeing did at least one flight with a simulated decompression (flight at 10,000ft) and one engine out for 5 hours or more so I'm sure it was considered if not flown during 787 certification.And I believe in service an ETOPS flight takes simiar issues into consideration.

In the 787 as well as other modern airliners the battery doesn't last forever--30 minutes maybe a little more--it is not expected to power the essential instruments for a 5.5 hour divert.
 
User avatar
Stitch
Posts: 23074
Joined: Wed Jul 06, 2005 4:26 am

RE: FAA Grounds 787, Part 11

Sun Feb 24, 2013 6:18 pm

Been reviewing the PPRune.net threads on this issue and found the following:

In regards to JA804A, NHK News is reporting that the JTSB has determined that the wiring for the APU battery had been installed correctly per the design blueprints. However, electricity continued to flow from the APU battery into the bus that powers the plane's navigation lights even though the flight crew had turned the relevant switches off on the flight deck.

The JTSB has found that the ground wires in the Ship's Battery were fused by an internal short circuit. They also report that the Ship's and APU batteries had been erroneously wired together (this part has me confused - they're supposed to be electrically connected since they work concurrently to start the APU).

The original battery design had only a single temperature sensor. The BMS managed the charging of cells using software that predicted the temperatures from the voltage across the cells. Hence reports Boeing will now install a temperature sensor for each cell going forward.
 
nycdave
Posts: 301
Joined: Mon Aug 16, 2010 4:22 pm

RE: FAA Grounds 787, Part 11

Sun Feb 24, 2013 6:26 pm

Quoting jporterfi (Reply 5):
Someone on another thread mentioned hte batteries would need to be tested to the point of failure, but I hardly see the point in that much testing. An interesting idea that was previously mentioned is conducting a test flight, then mid-flight, inducing thermal runaway in one cell of a battery and seeing if it spreads to other cells or outside of the containment box (most likely within a certain amount of time).

Why would they even need to do this in a test flight? If you're testing the containment between cells, and within the unit as a whole, seems like you could do that on the ground just as well, maybe just adjusting atmosphere or airflow in the testing chamber if you want to see what happens with venting?

Anyhow, according to the NYT today, sounds like Boeing has a fix in the works that would protect against all the theorized causes of failure causing destruction of the whole battery... Would love to hear some of the folks on here comment (if any of it is even slightly new news...)
 
justloveplanes
Posts: 867
Joined: Thu Jul 08, 2004 5:38 am

RE: FAA Grounds 787, Part 11

Sun Feb 24, 2013 6:47 pm

Quoting AngMoh (Reply 9):
Yes they are allowed to break, but they are not allowed to go up in flames.

Containment properly done make this issue a non-event from a thermal safety perspective. As has been stated previously, the total amount of energy releasable in a thermal event from the LiIon battery is known. It can be designed for, and was, but a bit too marginally. The issue is increased containment adds weight, which is why this too light containment strategy was implemented IMHO, to save weight. I would bet the engineers at Boeing considered heavier containment (as Airbus did even before these incidents according to posts on this thread), they are smart folks. The Boeing engineers made the wrong choice, but fixing it isn't an side of body join type of problem. Up the containment, take the weight penalty, on you go.

Quoting AngMoh (Reply 9):
Secondly, in the event it happens it should be harmless.

Easily acheivable as stated above. Take the hit on the weight. I"ll bet Boeing's solution is less than 100 lbs additional.

Quoting AngMoh (Reply 9):
Boeing is not improving the thermal management as they admit they don't know what caused the thermal runaway.

Yes is does, Boeing is designing for a worse thermal case incident on a frequent/continuous basis - assume a runaway every flight and design the system accordingly. An approach like this removes thermal management as a safety issue.

What is left is system availability to address. How is safety affected from a system operations (not thermal hazard) point of view when *both* batteries (main and APU) fail? I am assuming the batteries can cross feed one another's duty loads as stated elsewhere on these threads.

I don't think Boeing's cell isolation solution helps this. Apparently one cell failure may not cause thermal runaway of the pack, but the voltage in series design incapacitates the operational function of a pack with even a single isolated cell failure.

So the new math is what is the probability of both packs (main and APU) failing? If these probabilities go back down to very small numbers within certification targets for system availability for ETOPS, then I see no reason why the plane can't go back up.

If the numbers do work for this scenario, then Boeing would be correct in their assertion that the containment measures do indeed create a permanent fix by previously approved metrics. This would not be a subjective call at this point, if the FAA agrees the thermals hazard has been addressed, and system availability probabilities are within range, the plane should go back up.

[Edited 2013-02-24 11:09:46]

[Edited 2013-02-24 11:13:13]
 
blrsea
Posts: 1434
Joined: Fri May 20, 2005 2:22 am

RE: FAA Grounds 787, Part 11

Sun Feb 24, 2013 6:51 pm

I have a question regarding the new containment and venting design that Boeing has proposed. Will they actually let a battery catch fire and verify that it works properly in such a situation? Or do they simulate a fire inside the box using other materials and verify that containment & venting of smoke to outside works?
 
sweair
Posts: 1816
Joined: Sun Nov 20, 2011 9:59 am

RE: FAA Grounds 787, Part 11

Sun Feb 24, 2013 7:05 pm

Quoting blrsea (Reply 36):

I they can simulate a nuclear blast they surely can simulate a lithium fire. Germany and later China did test to shut down cooling on the HTR reactor, having simulated this earlier and the results were very similar in the real event.

If you know the input energy you know the possible output energy.
 
mjoelnir
Posts: 3932
Joined: Sun Feb 03, 2013 11:06 pm

RE: FAA Grounds 787, Part 11

Sun Feb 24, 2013 7:08 pm

Quoting justloveplanes (Reply 35):
What is left is system availability to address. How is safety affected from a system operations (not thermal hazard) point of view when *both* batteries (main and APU) fail? I am assuming the batteries can cross feed one another's duty loads as stated elsewhere on these threads.

I don't think Boeing's cell isolation solution helps this. Apparently one cell failure may not cause thermal runaway of the pack, but if the voltage in series design incapacitates the operational function of a pack with even a single isolated failure.

So the new math is what is the probability of both packs (main and APU) failing? If these probabilities go back down to very small numbers within certification targets for system availability for ETOPS, then I see no reason why the plane can't go back up.

If the numbers do work for this scenario, then Boeing would be correct in their assertion that the containment measures do indeed create a permanent fix by previously approved metrics. This would not be a subjective call at this point, if the FAA agrees the thermals hazard has been addressed, and system availability probabilities are within range, the plane should go back up.


Here is were Boeing should look at the possibility of subdividing the batteries.
Taken two half sized gives the same KW/h at about the same weight but when one cell goes up you only loose half of the capacity instead of all.

We also have to thing about the possibility that the B 787 will not get its ETOPS 330 straight away. Even ETOPS 180 could be a stretch. In this case the opinion of the FAA is not the only threshold, but as most of the B787 will not be registered in USA, they have to convince all the other regulators.
 
bellancacf
Posts: 148
Joined: Mon May 30, 2011 12:51 am

RE: FAA Grounds 787, Part 11

Sun Feb 24, 2013 7:28 pm

A quick look around the Web hasn't turned up any information on the kind of batteries that Boeing was proposing having in the SUGAR Volt aircraft, that "Prius of the Skies", as the media liked to call it, but I would imagine that Li-xx batteries were the leading candidates. What effect is the present situation having on the SUGAR Volt inside Boeing, or inside any other company that was considering a battery-rich aircraft? Perception problems or not, the thermal runaway issue seems to be very real indeed. Was the SUGAR Volt group sort of putting that issue aside until later, or did they -- like Tesla -- take a strongly proactive and preventive line in their design from early on?
 
sankaps
Posts: 1692
Joined: Fri Jan 04, 2008 6:51 am

RE: FAA Grounds 787, Part 11

Sun Feb 24, 2013 8:01 pm

Quoting cornutt (Reply 22):
But as I pointed out in the last thread, that's precisely how we handle blade failures in engines. It is not required to design an engine such that it is guaranteed to never throw a blade, nor does anyone know how to do so. We design containment into the engines.

I think my earlier comment addressing this line of reasoning was lost in the discussion above:

I am sure there are, in parallel, certain agreed to numbers for what acceptable engine blade failure rates are; if it were happening at what is feared to be 20x the expected rate (ie 2 instances in 50,000 hours instead of 1 in a million hours), and containment too was not working exactly as hoped, then it is highly likely the said engines would be grounded too.
 
packsonflight
Posts: 325
Joined: Tue Jan 12, 2010 2:55 pm

RE: FAA Grounds 787, Part 11

Sun Feb 24, 2013 8:11 pm

Quoting Revelation (Reply 19):
Yes, this is a big part of why I think I see FAA manuevering for a climb-down. It's hard to reconcile 10,000% safe with that statement, though.

The FAA will have to settle for less than 100% security, they are supposed to, but I cannot see FAA climb down from the special requirements set for the Li batteries on the 787, If they do that they have not much credibility left.
 
justloveplanes
Posts: 867
Joined: Thu Jul 08, 2004 5:38 am

RE: FAA Grounds 787, Part 11

Sun Feb 24, 2013 9:07 pm

Quoting packsonflight (Reply 41):
The FAA will have to settle for less than 100% security, they are supposed to, but I cannot see FAA climb down from the special requirements set for the Li batteries on the 787, If they do that they have not much credibility left.

This would depend on the intent of the special requirement. The assumption for this requirement was a design to provide adequate safety margin for failure every 1,000,000 hours I believe.

If the main concern of the failure for this special condition was a thermal hazard, then the FAA has an option to look at this from another angle. i.e. if (sorry for going on like a broken record, but I think this is key) containment is designed for * routine * failure of a battery from a thermal hazard perspective, the special condition is removed. It is assumed the system doesn't fail every 1,000,000 hours, it assumes regular failures and design for this condition. Regular faults, like a circuit breaker in a home are normal conditions, not special ones.

They system availability issue would then become the main issue to address. I am not sure if it is system availability or hazards of thermal risk that are the FAA's main concern when they say the route cause of the fires must be addressed. The system availability issue is much more vexing. New chemistry, cell architecture, additional redundancy or some combination of these is needed if the availability issue turns out to be the show stopper.
 
Rheinbote
Posts: 1103
Joined: Sun May 21, 2006 9:30 pm

RE: FAA Grounds 787, Part 11

Sun Feb 24, 2013 10:22 pm

Quoting bellancacf (Reply 39):
A quick look around the Web hasn't turned up any information on the kind of batteries that Boeing was proposing having in the SUGAR Volt aircraft

A SUGAR Volt concept is like 30 years away at best. You would have to improve energy density by a factor of 100 over Lithium-Ion battery technology to make full-electric large commercial aircraft feasible.
 
packsonflight
Posts: 325
Joined: Tue Jan 12, 2010 2:55 pm

RE: FAA Grounds 787, Part 11

Sun Feb 24, 2013 11:36 pm

Quoting justloveplanes (Reply 42):
This would depend on the intent of the special requirement. The assumption for this requirement was a design to provide adequate safety margin for failure every 1,000,000 hours I believe.

For starters the assumed failure rate was 1:10,000,000 operating hours.

I guess that the regulator wanted firstly: to assure that with Li battery system would not be less reliable than conventional system which has well documented track record.

Secondly they wanted to assure that potential on board battery fire did not pose a risk to the aircraft after the test facility for the 787 battery burned down.

System reliability is a big issue on an aircraft specially if you want to have over 300 minutes ETOPS, and it is perfectly normal for the regulator to demand from Li battery system at least equal reliability level as conventional battery system.
 
allegiantflyer
Posts: 235
Joined: Mon Mar 12, 2012 6:59 pm

RE: FAA Grounds 787, Part 11

Mon Feb 25, 2013 1:01 am

How much money are companies loosing from this grounding?seems to be taking a long period of time.
 
rcair1
Crew
Posts: 1121
Joined: Wed Oct 28, 2009 8:39 pm

RE: FAA Grounds 787, Part 11

Mon Feb 25, 2013 1:24 am

Quoting mjoelnir (Reply 47):
You rcair1 objects to what wisdom is saying, but in reality you say the same thing: you need the battery as a safety while flying.

Please do not equate what I say with what Wisdom is saying. With all due respect, we do not agree. I would expect that Wisdom feels the same way.

By way of example - from the previous thread.
-----
Quoting Wisdom (Reply 229):
No that's not what a battery is for. The battery is supposed to hold up critical systems for the duration of the diversion in case of an electrical failure. That is standby instruments, a navigation display and if possible, DC pumps to charge the accumulators (electric braking in the 787's case).
-----
I have not said that the battery is supposed to 'hold up' (power) critical systems for the duration of a diversion.

Quoting mjoelnir (Reply 47):
It does not matter what is completely right in this case, both of you say the battery is needed in flight!!!

I'm sorry - I disagree. It does matter who is "right" when you are talking about engineering.

We agree that the main battery (not APU battery) is a required flight item - which means if you loose it you land - just like if you lose an engine - or many other systems. You cannot take off with a failed battery. Neither can you with lots of systems on the plane.

....???
rcair1
 
User avatar
7BOEING7
Posts: 2357
Joined: Fri Oct 12, 2012 5:28 pm

RE: FAA Grounds 787, Part 11

Mon Feb 25, 2013 1:33 am

Quoting rcair1 (Reply 48):

I agree totally. Wisdom is completely distorting the actual use of the Main battery in a modern airliner
 
bellancacf
Posts: 148
Joined: Mon May 30, 2011 12:51 am

RE: FAA Grounds 787, Part 11

Mon Feb 25, 2013 1:52 am

to Rheinbote @ 43:

100-fold! That IS some speculation, then. I wonder what they had in mind. Presumably something, or the whole thing seems like a pipedream. On the other hand, when our own lipid deposits ("fat") are converted through mitochondria, etc., I've heard that they actually do have an energy density that is about 2 orders magnitude above NiCad technology. But at any rate, nothing in the SUGAR Volt project would have been able to advise the 787 designers on the best way to deal with larger-than-usual, higher capacity batteries subject to thermal runaway. Oh well.
 
mjoelnir
Posts: 3932
Joined: Sun Feb 03, 2013 11:06 pm

RE: FAA Grounds 787, Part 11

Mon Feb 25, 2013 2:11 am

Quoting rcair1 (Reply 48):

So to talk facts.

You say there is NO WAY that the ac part of the electrical system goes down and does not come up and the batteries have to keep carrying the load of the flight instruments?
That means you have to be 100% sure for your statements.

How many sets of AC/DC rectifiers are there between the AC/DC systems, and there is no possibility that something punches all of them out, no way?


I know there is redundancy I do not talk about that.
 
dtw2hyd
Posts: 2980
Joined: Wed Jan 09, 2013 12:11 pm

RE: FAA Grounds 787, Part 11

Mon Feb 25, 2013 2:20 am

Quoting bellancacf (Reply 50):
But at any rate, nothing in the SUGAR Volt project would have been able to advise the 787 designers on the best way to deal with larger-than-usual, higher capacity batteries subject to thermal runaway.

Boeing is already on record saying they studied every Li-on battery including the ones used in consumer electronics.

Tesla has a white paper on their battery system. It clearly states having large number(6800) of smaller cells creates large surface area to dissipate heat, hence avoid thermal runaway condition. I am not an expert but sounds like a good design idea in the absence of an active cooling system. General Motors has a battery lab continuously testing and improving their VOLT's battery technology. Their battery has 288 cells and a unique aluminum cooling fin design. Both Tesla and GM spent years designing and testing their battery systems. 787 batteries are relatively smaller than these batteries. Chances of car battery getting ruptured is very high than an aircraft. On same note car passengers have higher chance of existing the vehicle after an accident.

Who is online

Users browsing this forum: Baidu [Spider], cougar15, CrimsonNL, N353SK, rutankrd, Scorpio, shengzhurou, SomebodyInTLS, speedygonzales and 187 guests