[quote=DocLightning,reply=74]

what if they cant establish any reasonable cause?
in the end, they probably need more data. that is incidents. will they put the plane back into the air and await performance? guess they have to at some point. what about insurance companies? would they go along with such a decision without raising charges?

Quoting spacecadet (Reply 97): The NTSB has made it clear that they're not going to accept fires on airliners, period.

This may be a silly point - but I disagree that the NTSB has said that in the way you imply they have said it. The jet engines have fires in them. Piston engines have fires in them. APU's have fires in them. All totally acceptable.

Of course, if indeed their intent is to indeed ban all fires - then that would prevent such an event like this because there would be no aircraft at all (even gliders need an engine to pull them up).


Have a great day,

I didn't think there would be a pressurization problem if the valve in one of the EE bay was blocked by a burning battery, if it came to that the pressure build-up would unblock it anyway. I was suggesting/wondering that it may lead to smoke not being evacuated in the designed way but instead going exactly where we don't want it to go.

Quoting Stitch (Reply 99): JA804A operated for a year without a problem. 10 months with one battery and 3 months with another. And NH has three birds between 12 and 17 months with no issues.And yet JA829J operated some two weeks before it had a problem. But JL has other birds going on 9+ months with no issues.To my mind, something has to have changed. Some new variable has been introduced that significantly altered the probabilities of a battery issue. I've heard third-hand of a software update being applied to some 787s, but to date nobody else has picked it up so I don't know if there is any truth to it.

You are talking about the cause, not the containment. That would have been tested too, wouldn't it?

Quoting RickNRoll (Reply 103): You are talking about the cause, not the containment. That would have been tested too, wouldn't it?

I'm assuming it was as I can't see the FAA not requiring such validation.

I've asked for details, but so far nobody has provided any. I'm assuming that is because either nobody knows, or they're under an NDA.

I'd like to know how the leaking compared on the NH plane and the JL plane. The JL plane was on the ground with no airflow in the bay. So leaking electrolyte should have just dripped down the side and fallen to the floor. With no external forces acting on it, would it make it to the drain plugs, or just pool? And with no airflow, smoke, fumes and vapors would likely collect.

The NH plane had active airflow and flight forces in play. Did that affect the flow of electrolyte once it left the battery? Or did it to just drip down the sides and pool at the bottom? And with active air flow, smoke, fumes and vapors would have been purged via the outflow valves once activated by the flight deck (once they detected the initial smell).

[Edited 2013-01-28 17:47:32]

Quoting 2175301 (Reply 101): This may be a silly point - but I disagree that the NTSB has said that in the way you imply they have said it. The jet engines have fires in them.

They're fine with very controlled combustion. When we say that an engine is on fire we rarely mean it's functioning as intended.

Quoting 2175301 (Reply 101): there would be no aircraft at all (even gliders need an engine to pull them up).

Some gliders can be launched by foot. Some gliders have electric engines and...you got it, Li-ion batteries allowing them to take off and go up to 3000m AGL.

Quoting AeroWesty (Reply 88):

Quoting AeroWesty (Reply 88): Quoting michiganatc (Reply 87): With the 787's all grounded, what airports did United's end up at? Location/plane number: IAH: 901, 902, 905 & 906 LAX: 903 NRT: 904

wait didn't the FAA grant a waiver allowing these birds to be flown back to their home bases ?

Quoting RickNRoll (Reply 94): Another question. Wouldn't Boeing have had to do a battery failure containment test during certification. Given the design of the container, I would assume it would have behaved pretty much the same then as it did in the recent events. Would it not have had flammable electrolyte leaking out in those tests, and have generated the same amount of heat. Why would that have been acceptable then, but not now?

Possibly this was never tested, and the FAA relayed on documents provided by Boeing. I guess now when on two occasions the battery have failed it did not happen as expected or described in the documents provided by Boeing.

Quoting spacecadet (Reply 97): The FAA could always go against the NTSB's recommendations and remove or revise the AD, and there's a chance that they might do that if things drag on for an indeterminate amount of time, but that would probably be a foolish PR move because they'd basically be telling people "we know we said we were grounding the plane for safety reasons, but... well, yeah, just go fly it anyway."

Why should FAA go against NTSB in the first place? isn't the aircraft grounded for a good reason? There are already allegations of cozy relationship between Boeing and FAA and it would be stupid for them to take a chance like that, and it would be reckless to do so without at least being able to pinpoint the reason for those two battery fires.

Quoting alberchico (Reply 106): wait didn't the FAA grant a waiver allowing these birds to be flown back to their home bases ?

I'm not sure but the LOT 787 wasn't even covered by the FAA grounding and I was told it was still in Chicago as of two days ago.

Quoting RickNRoll (Reply 92): However, there is no controlled means of releasing pressure in the existing design.

Actually, if I understand this right, there is. There's an overboard vent connected to the containment; it's clearly visible in one of the photos on Aviation Herald. What controls it, and under what circumstances it opens, is the part that isn't clear to me. I don't think it's just an open hole.

Quoting alberchico (Reply 106): wait didn't the FAA grant a waiver allowing these birds to be flown back to their home bases ?

The FAA doesn't grant blanket waivers for those sorts of things; an airline that wanted to ferry their planes would have to ask for waivers for each flight, with specific information about the procedures to be used and the routing of the flight. Right now, I don't think there is any motivation to ferry them anywhere, since the airlines don't know where they will have to take them: is the work that will be needed something that they can do at their maintenance facilities, or will all the planes have to be flown back to Everett?

Quoting PanAmPaul (Reply 108): Quoting alberchico (Reply 106): wait didn't the FAA grant a waiver allowing these birds to be flown back to their home bases ? I'm not sure but the LOT 787 wasn't even covered by the FAA grounding and I was told it was still in Chicago as of two days ago.

The EASA (EU equivalent of the FAA) issued their own grounding order almost immediately after the FAA order was issued.

Quoting Stitch (Reply 104): The JL plane was on the ground with no airflow in the bay. So leaking electrolyte should have just dripped down the side and fallen to the floor. With no external forces acting on it, would it make it to the drain plugs, or just pool?

If it was thin enough it would have found a body drain and dripped out of the airplane. I guessing that it was thick and grew thicker as it cooled and may not have made it to the body drain for that area.

Quoting Stitch (Reply 104): The NH plane had active airflow and flight forces in play. Did that affect the flow of electrolyte once it left the battery? Or did it to just drip down the sides and pool at the bottom? And with active air flow, smoke, fumes and vapors would have been purged via the outflow valves once activated by the flight deck (once they detected the initial smell).

Up until the smoke set off the smoke detector in the fwd E&E bay one of the cooling fans were blowing air over the equipment and into the cargo area. When smoke is detected the system automatically reconfigures and uses differencial pressure to suck the air past the equiptment and out of the airplane through the overboard venturi.

Quoting cornutt (Reply 109): Actually, if I understand this right, there is. There's an overboard vent connected to the containment; it's clearly visible in one of the photos on Aviation Herald. What controls it, and under what circumstances it opens, is the part that isn't clear to me. I don't think it's just an open hole.

If its the photo of the airplane with the two insets showing "stains" down the side of the airplane, the botttom inset shows the fwd overboard vent valve and the upper one is form the overboard venturi which would have opened once smoke was detected. Neither is directly connected to the battery box.

Quoting asctty (Reply 83): Don't forget that if the Rupture Valve is activated then the battery is now useless in its function as a safety supply to the aircraft electrical system. Now that is really important is it not?

It's important for the main battery, not really for the APU battery. The APU battery really has no foreseeable purpose in flight, since the only time you'd need it is if the airplane managed to get all the way from normal configuration to no generators in less time than it takes to start the APU via some failure that would still allow the APU to run (i.e. you still have fuel) and still allow the power system to function (i.e. you're capable of even using the APU power). That's a pretty small failure space...small enough that, as far as I know, it's never happened in the history of modern airliners.

For the main battery, it also has no purpose in flight unless all the other electrical sources fail. This does play into the ultimate reliability of the power system but it's far out in the 1 in a million to 1 in a billion territory (among other things, if you're all the way down to battery power with no RAT you've completely lost ETOPS capability) so, though important, the probability of it actually coming up is extremely remote. The same special conditions that govern battery failure modes also require that the flight crew be notified any time the main battery isn't capable of doing it's job in the event that it's needed, so a crew would know they had no battery available and could take appropriate action (e.g. preemptively start the APU, drop the RAT, divert, etc.)

Quoting asctty (Reply 86): What if the battery was called upon to supply emergency power and permit safe landing of the aircraft?

If the battery had been on fire, it would not provide that function. However, in order to get to that state, you have to have all four engine generators fail and both APU generators fail (or the APU itself fail) and the RAT fail, all at the same time.

Quoting asctty (Reply 86): Please reassure me this is not the normal hazard assessment approach in the airline industry?

I'm not sure what you're referring to with "this" but yes, this is the normal hazard assessment approach in the airline industry. You ensure that no single failure, no matter how remote, can threaten safe flight and landing. Then you look at the probability of all foreseeable failure combinations and make sure that the probability is below thresholds corresponding to the magnitude of the effect...for threats to continued safe flight and landing, the probability of reaching that state is supposed to be extremely remote, which means less than 1 per billion flight hours.

Quoting RickNRoll (Reply 92): However, there is no controlled means of releasing pressure in the existing design. The case is sealed, until pressure forces it to deform, allowing flammable material to be released.

The case isn't sealed...steel that thin wouldn't stand up to pressurization cycles. The battery would blow up like a balloon the first time you took off.

Quoting RickNRoll (Reply 92): It allows heat damage to occur to surrounding equipment, so the case is not protecting the environment adequately either, in respect to the heat generated by a thermal runaway.

The requirement is:
http://www.gpo.gov/fdsys/pkg/FR-2007-10-11/html/E7-19980.htm

(5) No corrosive fluids or gases that may escape from any lithium
ion battery may damage surrounding structure or any adjacent systems,
equipment, or electrical wiring of the airplane in such a way as to
cause a major or more severe failure condition

and

(6) Each lithium ion battery installation must have provisions to
prevent any hazardous effect on structure or essential systems caused
by the maximum amount of heat the battery can generate during a short
circuit of the battery or of its individual cells.

Heat damage to surrounding equipment is allowed if that damage does not have any hazardous effect on the structure or system. So, for example, scorching of the rack is heat damage but is allowed by the special condition since it doesn't have a hazardous effect on any structure or system.

Quoting RickNRoll (Reply 92): The enhanced case is obviously the answer, but what would this require in respect of design, manufacturing, testing and certification?

That's not obviously the answer because it doesn't address the FAA & NTSB concern that the battery failure rate is too high.

Quoting RickNRoll (Reply 92): How long would this process take?

To do a new case...a month, maybe two.

Quoting RickNRoll (Reply 92): Would the FAA keep the 787 grounded till this whole process is complete.

Probably.

Quoting AeroWesty (Reply 93): Other than just looking at the photo of the EE bay from the JAL plane, has there been any indication what other than the battery pack was damaged, and how long it would take to repair the ancillary damage the plane sustained?

So far, there has been no indication that anything was damaged to the point of impairing it's function. There was scorching, burned blobs of battery goo in the bilge, etc. but no report that any other systems quit working or that any structure was damaged in a way that impaired it's ability to function.

Quoting RickNRoll (Reply 94): Wouldn't Boeing have had to do a battery failure containment test during certification.

Not necessarily. Containment is, in general, a pretty well established discipline so it could have been done by analysis. It also could have been tested at the assembly level (which is still part of certification but it would have been the battery vendor, not Boeing, doing the test).

Quoting RickNRoll (Reply 94): Would it not have had flammable electrolyte leaking out in those tests, and have generated the same amount of heat. Why would that have been acceptable then, but not now?

Because the FAA requirements were not that no heat escape or that no electrolyte escape. The requirements were that whatever does escape can't damage surrounding systems or structure in a hazardous way. So far, I don't see any reports that such damage occurred, which is why I'm curious what the FAA/NTSB are seeing that they're not saying yet.

Quoting RickNRoll (Reply 96): Which does not answer the question. If the events now would have been pretty well identical to the tests then, why is it different now?

Because of other parts of the special condition:
(1) Safe cell temperatures and pressures must be maintained during
any foreseeable charging or discharging condition and during any
failure of the charging or battery monitoring system not shown to be
extremely remote. The lithium ion battery installation must preclude
explosion in the event of those failures.
(2) Design of the lithium ion batteries must preclude the
occurrence of self-sustaining, uncontrolled increases in temperature or
pressure.

Whether or not the containment worked as designed, the batteries did not maintain safe cell temperature (assuming this occurred during charge/discharge/failure of the BMS) and did have uncontrolled increases in temperature.

So the FAA/NTSB is rightly concerned that the batteries aren't behaving they were designed to do.

Quoting Aesma (Reply 102): I didn't think there would be a pressurization problem if the valve in one of the EE bay was blocked by a burning battery, if it came to that the pressure build-up would unblock it anyway. I was suggesting/wondering that it may lead to smoke not being evacuated in the designed way but instead going exactly where we don't want it to go.

All outflows are on the lower lobe. If one outflow valve plugged, the other valve would automatically open to maintain pressure and the flow patterns would switch around but everything should still stay on the lower lobe. If both outflow valves plugged (I'm not sure how that's physically possible but we'll assume so for the sake of argument) then the airplane would go up to maximum design pressure then the overpressure relief valves would open. They're also in the lower lobe so things should still stay on the lower deck. If the ECS system failed, an emergency scoop opens up to provide airflow (although not pressurization). If even that fails, the flight deck has an extra emergency scoop to keep the flight deck clear so the pilots can still fly.

Quoting Stitch (Reply 104): The NH plane had active airflow and flight forces in play. Did that affect the flow of electrolyte once it left the battery?

Flight forces might. Airflow probably wouldn't. Although the airflow is carefully designed, it's not like a noticeable wind in the EE bay. It's not going to blow electrolyte around, it's more like other "high" airflow environments like a cleanroom or OR.

Quoting Stitch (Reply 104): And with active air flow, smoke, fumes and vapors would have been purged via the outflow valves once activated by the flight deck (once they detected the initial smell).

Smoke would be caught by the smoke detectors and trigger reconfiguration. Smell/fumes/vapors might cause the flight crew to trigger it earlier if they noticed that and took action before they got all the way to smoke.

Tom.

Quoting tdscanuck (Reply 114): The case isn't sealed...steel that thin wouldn't stand up to pressurization cycles. The battery would blow up like a balloon the first time you took off.

I just got the most hilarious mental image...  

Quoting macc (Reply 100): what if they cant establish any reasonable cause?

Yes, well that's what I'm worried about. What if they simply cannot ascertain a cause? At what point do they give up?

Tom? Do you know what would happen in that eventuality? Has it ever happened?

Quoting packsonflight (Reply 107): Possibly this was never tested, and the FAA relayed on documents provided by Boeing.

The FAA almost never tests anything themselves as part of certification (they do their own R&D and investigation testing though). They, or their designates, witness the testing done by others.

Quoting packsonflight (Reply 107): Why should FAA go against NTSB in the first place?

NTSB's mission is purely accident investigation and safety; many of their recommendations, though technically correct, aren't viable for various reasons. FAA, not NTSB, is the one who decides what makes sense to actually implement. This practice is so old that the NTSB maintains a "Top 10" list of things they want that the FAA hasn't implemented.

Quoting packsonflight (Reply 107): There are already allegations of cozy relationship between Boeing and FAA

These allegations can only come from people who've never actually worked with a regulator.

Tom.

Quoting tdscanuck (Reply 114): That's not obviously the answer because it doesn't address the FAA & NTSB concern that the battery failure rate is too high.

It's not the answer to the cause, I was referring to the containment requirement.

If the cause is never found, it will likely be even more important.

[Edited 2013-01-28 20:18:08]

Quoting tdscanuck (Reply 114): If the ECS system failed, an emergency scoop opens up to provide airflow (although not pressurization). If even that fails, the flight deck has an extra emergency scoop to keep the flight deck clear so the pilots can still fly.

If the both packs fail, pressurization can't be maintained and the pilot descends to the lowest safe altitude or 10.000 ft whichever is higher. Depending on the external temperature the cabin or the cockpit or both is liable to get too hot and the alternate ventilation system allows external air to flow through the airplane in an attempt to cool the interior. There is one switch that controls one valve that is flush mounted. This isn't Baskin & Robbins--you don't get two scoops and it is not used in smoke situations.

Quoting Stitch (Reply 95): BECAUSE THE SPECIAL CONDITIONS DO ALLOW THE CONTAINMENT VESSEL TO LEAK ELECTROLYTES

But the FAA says "The battery failures resulted in release of flammable electrolytes, heat damage, and smoke on two Model 787 airplanes."

Am I reading this wrong? The release of electrolytes seems to be one of their major concerns, because they are flammable. Have they simply changed their minds between then and now, having seen the effects of the leakage.

[Edited 2013-01-28 20:28:05]

[Edited 2013-01-28 20:51:59]

Quoting cornutt (Reply 110): Right now, I don't think there is any motivation to ferry them anywhere, since the airlines don't know where they will have to take them

EASA would be authority to issue a wavier for the LOT aircraft BUT it would also need the agreement of all countries under the flight path, because of the AD. GC ORD-WAW would require agreement from USA, Canada, Denmark, Iceland, Norway & Sweden. You might be able to route around Norway & Sweden.

Too much trouble at the moment as, as cornutt says, they don't know where they will have to send the birds to get fixed.

Gemuser

Quoting tdscanuck (Reply 82): Quoting mham001 (Reply 63): I do think however having the BMS in the same box is absurd. This would not have have happened were I in charge of that design. The farther you move the BMS from the battery, the more potential failure points you inject into the fault tree.

Probably minor ones compared to whatever happened. But I agree, that the BMS does not depend on its location for it to function. And that there is no longer a job to do for the BMS once a cell runs away.

Quoting Stitch (Reply 95): BECAUSE THE SPECIAL CONDITIONS DO ALLOW THE CONTAINMENT VESSEL TO LEAK ELECTROLYTES. If it did not, it risks explosion.

Leaking electrolytes don't change the total volume in the vessel. So why on earth should that vessel explode because of electrolytes?

Quoting tdscanuck (Reply 114): Quoting RickNRoll (Reply 96): Which does not answer the question. If the events now would have been pretty well identical to the tests then, why is it different now? Because of other parts of the special condition: (1) Safe cell temperatures and pressures must be maintained during any foreseeable charging or discharging condition and during any failure of the charging or battery monitoring system not shown to be extremely remote. The lithium ion battery installation must preclude explosion in the event of those failures. (2) Design of the lithium ion batteries must preclude the occurrence of self-sustaining, uncontrolled increases in temperature or pressure. Whether or not the containment worked as designed, the batteries did not maintain safe cell temperature (assuming this occurred during charge/discharge/failure of the BMS) and did have uncontrolled increases in temperature. So the FAA/NTSB is rightly concerned that the batteries aren't behaving they were designed to do.

Requirement (1) and (2) cover also the requirement (6) somehow redundantly and in a more generic way. Requirement (6) only adds a further condition, under which (1) and (2) specifically are not allowed to happen. While (1) and (2) rule out any cause of a thermal runaway in a very generic, broad way already in the first place.

IMO the requirements are not 100% solid and may require adjustments:
e.g. (2) lays the focus of preventing a thermal runaway on the design of the battery. As if a thermal runaway induced by a failing BMS would be ok. In reality the larger responsibility and risk lays on the side of the charger. So its design should have been included in (2). Because we do agree that thermal runaways coming from misdesigned batteries is equally bad as thermal runaways that come from something else, don't we?

Quoting rheinwaldner (Reply 121): Leaking electrolytes don't change the total volume in the vessel. So why on earth should that vessel explode because of electrolytes?

Because in order to contain all of the temperature and pressure in that fire, it would have to be made of 6"-thick steel plate.

Quoting spacecadet (Reply 97): The NTSB has made it clear that they're not going to accept fires on airliners, period. As various people have said, there's always going to be that chance, however remote and with any kind of battery, so you're never going to make it impossible.

That makes sense of course, and totally understandable. It might be possible to take the position, however, that a contained combustion event is not a fire (such as the burning of tons of aircraft fuel as was mentioned). You can design, without much magic and feasibly, containment that makes any battery combustion event non-hazardous in and of itself.

It will add significant weight to the aircraft, maybe 50 - 100 lbs. But it wont be any more of a thermal event from a safety perspective, than say, a warming oven for inflight meals.

Of course, long term, with that containment requirement for LiIon, and all that extra weight and complexity, might as well just go NiCad.

I think NiCads are the ultimate solution, LiIon too flaky. What ever is burning up those batteries is doing it in a pretty stable electrical environment it seems (unless measurements are wrong for the charging loop and indeed the thing is being overcharged, we should know that shortly).

NiCad's aside, new containment is something Boeing might need to do now to get out its current fix. Take the fire event out of the equation by transforming the environment.

Quoting Stitch (Reply 95): If it did not, it risks explosion. That is why the top of the container has a handful of screws holding it on and it overlaps the sides of the case so it can vent electrolyte. If it was designed to not allow a leak, they would have welded the top shut, as well. What is NOT allowed to happen is that the leaked electrolytes subsequently take out a flight-critical system. And while JA804A didn't suffer damage to critical systems from the electrolyte, the FAA and NTSB are not convinced that it cannot happen.

In any container that can have an overpressure event, you obviously do not weld it shut, but you have exhausts for the gases and spare storage room for any escaping liquids. I am quite shocked reading up on the requirements the FAA put up for the battery installation. This is less than what is expected by various US agencies for lead acid batteries in buildings or telecom applications:

http://www.battery-usa.com/Regulations-SpillContainment.htm

Quoting justloveplanes (Reply 123): I think NiCads are the ultimate solution,

NiMh has an even greater power density than Li-ion...but has a much lower power to weight ratio. They are slightly heavier than NiCd's, just as reliable but much superior power density, same voltage per cell and use the same chargers.

I have no idea if they are certified for aircraft but it's just about impossible to find NiCd's used on earth anymore.

Quoting beau222 (Reply 43): Does the 748 series use the same type of battery or batteries that the 787 is having issues with?

Quoting Stitch (Reply 62): No. I's probably NiCad (747s before the 747-400 use lead acid).

It is a Saft CVH531KA, a 20-cell, 53 Ah 24V NiCad rechargeable pack. It weights exactly 96 pounds.

NS

Quoting rheinwaldner (Reply 121): Leaking electrolytes don't change the total volume in the vessel. So why on earth should that vessel explode because of electrolytes?

It has been mentioned 50+ times in these threads that thermal runaway results in release of gasses and many posters want to have the battery sealed so nothing leaks. Gasses build pressure if they are produced in a sealed pressure vessel and eventually if vessel fails you have an explosion. Volume of electrolyte has nothing to do with pressures built by thermal runaway. How hard can it be to understand this?

Quoting RickNRoll (Reply 119): But the FAA says "The battery failures resulted in release of flammable electrolytes, heat damage, and smoke on two Model 787 airplanes."

After 300 posts, you are still asking the same questions. Let's try again: yes, it did. As Tom quoted from the special requirements (emphasis mine):

(5) No corrosive fluids or gases that may escape [MAY ESCAPE, meaning they are allowed to leak!!!] from any lithium ion battery may damage surrounding structure or any adjacent systems, equipment, or electrical wiring of the airplane in such a way as to cause a major or more severe failure condition

I really don't understand what's not clear in the above sentence.

[Edited 2013-01-29 00:52:46]

Quoting DocLightning (Reply 122): Because in order to contain all of the temperature and pressure in that fire

You speak about fire, pressure and temperature. I only about leaked electrolytes. These are two things.
Stitch wrote with large letters, that leaking electrolytes would lead to an explosion.
Thruth is, that leaking electrolytes are a result of a fire and heat in the first place. And the containment sure would exlode without some venting. But not because of the electrolytes. Responsible for that would be first the heat and the fire, which then produce gases that increase the volume, with results in pressure. Leaking electrolyte are not involved in that chain.

Quoting BEG2IAH (Reply 127): It has been mentioned 50+ times in these threads that thermal runaway results in release of gasses and many posters want to have the battery sealed so nothing leaks. Gasses build pressure if they are produced in a sealed pressure vessel and eventually if vessel fails you have an explosion. Volume of electrolyte has nothing to do with pressures built by thermal runaway. How hard can it be to understand this?

I dare say that it is not really rocket science to built a containment vessel that keeps the liquids in and lets the gas out. Even if the liquids should increase their volume with a temeprature increase, it is not hard to make provisions for that as well.

Quoting BEG2IAH (Reply 127): (5) No corrosive fluids or gases that may escape [MAY ESCAPE, meaning they are allowed to leak!!!] from any lithium ion battery may damage surrounding structure or any adjacent systems, equipment, or electrical wiring of the airplane in such a way as to cause a major or more severe failure condition I really don't understand what's not clear in the above sentence.

It doesn't say "fluids or gases that may escape", it says "NO corrosive fluids or liquids that may escape", there is a big negative at the start of that sentence. So I asked, in his terms, does that mean that they have changed their minds, since their statement clearly indicates that corrosive fluids or liquids that have escaped are an issue for them.

Well it would also depend on what you define as the battery. If the baterry is just the cells and the charger and the metal box around it is the containment, than this actually makes sense. Becuase the cells will leak in a failure, so demanding that they do not leak, would be impossible.

Quoting JoeCanuck (Reply 125): NiMh has an even greater power density than Li-ion...but has a much lower power to weight ratio. They are slightly heavier than NiCd's, just as reliable but much superior power density, same voltage per cell and use the same chargers.

NiMH does sound interesting. Obviously seems more stable than LiIon? Less prone to runaway? Same current delivery (Per Ah reserve) and recharge cycle capable? Re: you said slightly heavier that NiCad, on what basis? lb/Amp-hour?

Quoting gigneil (Reply 126): It is a Saft CVH531KA, a 20-cell, 53 Ah 24V NiCad rechargeable pack. It weights exactly 96 pounds.

Design questions, why use NiCads instead of NiMh on the 748? Certification?

I recall that the statement was made that other chemistries couldn't work in the 787, I have to assume that means same weight, etc and a few other items. If you can deliver voltage and current and have a decent recharge cycle life, what else is a factor in the 787? Are there complex loads that require driving in a certain impedence and current profile? If it's just to start a big gas engine like an APU, I can't imagine that is the case.

Why else would NiMh/NiCad not work in the 787 if you are willing to live with the weight penalty? What would the weight difference be for similar current delivery and Ah reserve of these chemistries vs Li-Ion?

Quoting flyglobal (Reply 16): For Air Planes the design requirements are different - less environmental temperature span at the battery location

Just my own 2 cents.

Based on my own line of work there would [probably] have been a separate environmental requirement for the battery as opposed to the plane. But it would have been dictated by Boeing as the end user. So I'm wondering if the requirement was based on the batteries used in their other planes?

Having said that, I know from experience that when designing/providing a system to a customer, we test the system/component not just to confirm that it works as designed but also to prove that if something goes wrong it will fail in a controlled manner without risk to the user. I absolutely guarantee that Yuasa's tests covered not just battery failure but catastrophic battery failure. Boeing would have expected proof before accepting.

Quoting vivekman2006 (Reply 37): 100C is the temperature at which water boils and is absolutely un-survivable! The highest temperature ever recorded on Earth is 56.7C (134F) in Death Valley, CA http://www.foxnews.com/science/2012/...ared/

Was almost going to accept this [highest temp recorded] but then I noticed who your source is so...     

Quoting justloveplanes (Reply 132): Design questions, why use NiCads instead of NiMh on the 748? Certification?

NiMH has higher capacity than NiCad. But unfortunately NiMH has by far the highest internal resistance when cold of all relevant battery types, including Lead-acid.

For winter use they would have to be vastly oversized compared to NiCad in order to deliver the amps needed. That's the reason why NiMH has never been considered relevant as starter battery for airliners.

NiCad is vastly superior for short duration high power applications.

For starting at 0 deg. F ( -18 deg. C) a NiMH battery would be two or three times heavier than a NiCad. It would, however, do more consecutive starts without recharging, but that's not a selling point.

NiMH is the perfect choise for household application where low temperature is not an issue, and where weight issues don't call for Li-Ion.

Quoting DocLightning (Reply 115): What if they simply cannot ascertain a cause? At what point do they give up? Tom? Do you know what would happen in that eventuality? Has it ever happened?

I was just talking about that with some friends last night...the short answer is, I don't know, because I don't think anyone has been in this situation before. All other prior groundings (that we could think of) were preceded by multiple fatal crashes. We couldn't think of a prior grounding with (relatively) so little known cause. That's not a criticism of the grounding, the industry has progressed a lot in safety since then, but it sets up an interesting problem. In this case, the FAA has somewhat painted themselves into a corner...they really can't lift the grounding until they know root cause and have a fix. But there's a non-zero chance that they won't be able to find root cause. And I don't think anyone (yet) know's what to do then. I have no idea how you'd handle the certification or PR in that situation...in some respects, it would be worse than the DC-10 type situation where, at least, you could point to the cause, point to the fix, and say, "See, we're good now."

Quoting 7BOEING7 (Reply 118): Depending on the external temperature the cabin or the cockpit or both is liable to get too hot and the alternate ventilation system allows external air to flow through the airplane in an attempt to cool the interior. There is one switch that controls one valve that is flush mounted. This isn't Baskin & Robbins--you don't get two scoops and it is not used in smoke situations.

The alternate ventilation scoop/vent/take-your-pick (the one with the switch) is down on the lower fuselage. The other one is manual and built into the flight deck escape hatch (you need to pull down the cover to access it). It's called the "flight deck overhead vent" and is part of the "cabin too hot" checklist, which shows up in (among other things) the depressurization checklist. You're correct that it's not an explicit part of the smoke checklist but several other parts of the smoke checklist, notably putting the EE cooling into alternate ventilation, may result in heat buildup in the flight deck. If I were a flight crew, I'd also seriously consider using the overhead vent if the other smoke/fume removal steps were not successful.

Quoting RickNRoll (Reply 119): Quoting Stitch (Reply 95): BECAUSE THE SPECIAL CONDITIONS DO ALLOW THE CONTAINMENT VESSEL TO LEAK ELECTROLYTES But the FAA says "The battery failures resulted in release of flammable electrolytes, heat damage, and smoke on two Model 787 airplanes."

And the FAA's statement is absolutely true. It's a factual statement about what happened. That's quite a bit different than a statement that the release caused hazardous damage to any other systems or structure, which is what would be required to violate that part of the special conditions (it may have, but they haven't said that and we probably won't know until more investigation results come out).

Quoting RickNRoll (Reply 119): Am I reading this wrong? The release of electrolytes seems to be one of their major concerns, because they are flammable. Have they simply changed their minds between then and now, having seen the effects of the leakage.

Their major concern, as they said, is that the released electrolytes *could* (not "did") result in damage to other systems. This suggests that something with the initial fault tree analysis isn't right, or at least the FAA isn't convinved it was right...it's pretty obvious that the probability of battery failures must have been wrong, but they may also have seen something in the incidents that suggests the connection between electrolyte release and damage to other equipment may not have been correct...but if they have, they're not talking about it yet.

Quoting rheinwaldner (Reply 121): Quoting Stitch (Reply 95): BECAUSE THE SPECIAL CONDITIONS DO ALLOW THE CONTAINMENT VESSEL TO LEAK ELECTROLYTES. If it did not, it risks explosion. Leaking electrolytes don't change the total volume in the vessel. So why on earth should that vessel explode because of electrolytes?

Absent physical compromise of the battery case, electrolytes leak because of a thermal runaway. Thermal runaway is hot enough to vapourize part of the electrolytes, which means you're releasing gas in the battery case. You're also heating the air that was already in the battery case. Both of those mean a pressure rise if you've got a sealed case. It's not that the electolyte, by itself, spontaneously causes a pressure rise. But the fact of leaking electrolyte, in this context, means you've also got enough heat to cause a pressure rise, where one of the big contributors is vapourized electrolyte.

Quoting rheinwaldner (Reply 121): Because we do agree that thermal runaways coming from misdesigned batteries is equally bad as thermal runaways that come from something else, don't we?

The end result, yes. Ability to fix is better mis-designed batteries (since it's a contained LRU) rather than something else (which would imply more of a system effect).

Quoting justloveplanes (Reply 123): It might be possible to take the position, however, that a contained combustion event is not a fire (such as the burning of tons of aircraft fuel as was mentioned).

I think you'd have to admit it's a fire, just like combustion in the engines, just that it's acceptable if you can "guarantee" it's fully contained and the system level effects are acceptable.

Quoting rheinwaldner (Reply 128): Stitch wrote with large letters, that leaking electrolytes would lead to an explosion. Thruth is, that leaking electrolytes are a result of a fire and heat in the first place. And the containment sure would exlode without some venting. But not because of the electrolytes.

This started from the claim that the battery box should be (or was) sealed. If you have leaking electrolytes from a sealed battery case, that means you built up pressure of hot, flammable gas inside a box with it's own oxidizer...that's a recipe for an explosion.

Quoting seahawk (Reply 129): I dare say that it is not really rocket science to built a containment vessel that keeps the liquids in and lets the gas out. Even if the liquids should increase their volume with a temeprature increase, it is not hard to make provisions for that as well.

Agreed. I strongly suspect that's got to be one of the possible fixes being examined. It's a different (heavier) way to implement the containment but might be what's required to satisfy the FAA/NTSB now.

Tom.

Quoting RickNRoll (Reply 130): It doesn't say "fluids or gases that may escape", it says "NO corrosive fluids or liquids that may escape", there is a big negative at the start of that sentence. So I asked, in his terms, does that mean that they have changed their minds, since their statement clearly indicates that corrosive fluids or liquids that have escaped are an issue for them.

The grammar is perfectly clear to me - if corrosive fluids or liquids do escape they may not damage surrounding structures.

So the FAA and NTSB have not changed their position. What has changed is their confidence level about any escaping fluids or gases not damaging surrounding structure or any adjacent systems, equipment, or electrical wiring of the airplane in such a way as to cause a major or more severe failure condition.



If the intention was to say no corrosive fluids or liquids may escape, that entire section would be written as such: "No corrosive fluids or liquids may escape from any lithium ion battery."

Quoting tdscanuck (Reply 135): Quoting seahawk (Reply 129):I dare say that it is not really rocket science to built a containment vessel that keeps the liquids in and lets the gas out. Even if the liquids should increase their volume with a temeprature increase, it is not hard to make provisions for that as well. Agreed. I strongly suspect that's got to be one of the possible fixes being examined. It's a different (heavier) way to implement the containment but might be what's required to satisfy the FAA/NTSB now.

Any reason why it wouldn't work to just enlarge the dimensions of the battery case by an inch or two and and use it as a (secondary) container for the existing battery? Gas would still be vented and any electrolyte escaping the inner case would be contained in the outer.

Quoting tdscanuck (Reply 135): I was just talking about that with some friends last night...the short answer is, I don't know, because I don't think anyone has been in this situation before. All other prior groundings (that we could think of) were preceded by multiple fatal crashes. We couldn't think of a prior grounding with (relatively) so little known cause. That's not a criticism of the grounding, the industry has progressed a lot in safety since then, but it sets up an interesting problem. In this case, the FAA has somewhat painted themselves into a corner...they really can't lift the grounding until they know root cause and have a fix. But there's a non-zero chance that they won't be able to find root cause. And I don't think anyone (yet) know's what to do then. I have no idea how you'd handle the certification or PR in that situation...in some respects, it would be worse than the DC-10 type situation where, at least, you could point to the cause, point to the fix, and say, "See, we're good now."

Me thinks they will add a bunch of inspections (maint) and procedures (flight crew) and once an airline has met the requirements they will be allowed to resume ops.

Longer term (different ADs) could be that they add additional monitoring (dual) and probably lower some of the control limits, such as thermal protection and probably add some drip shields.

Cheers

Quoting vzlet (Reply 137): Any reason why it wouldn't work to just enlarge the dimensions of the battery case by an inch or two and and use it as a (secondary) container for the existing battery?

The only obvious issue I can see is that I'm sure there's some clearance requirement between the battery and surrounding parts, precisely to avoid meaningful heat damage to other parts from a runaway battery. I'm not sure how much room there is between the existing case and the point where they have to start revisiting the clearances or moving other things.

Tom.

look guys,
Everybody is going on and ON about the Lithium-Ion Batteries and their safety, But NOBODY seems to question the Manufacturer OF said batteries and whether THEY had any culpability in their Manufacturing process According to Aviation Week 21Jan,2013, GS YASA of Japan was the manufacturer. I've seen nowhere that their manufacturing and testing process was reviewed or compared to a company like SAFT to determine it's effectiveness or to root out flaws. The airplanes involved were among the first to be delivered. There have only BEEN 51 deliveries to date. United (whom I work for) has had other problems with the airplane due to it's new systems technology got NOT with the batteries so it could be that a change in manufacturers might more be in order than the Lithium ion battery itself or install a third Ni cad battery in the rear compartment for the extra OOMPH starting the engines, apu or ground operation might take and drive ON! I know Boeing might not want to hear this but they're going to be on the hook for 51 airplanes sitting gathering DUST if the don't do something PDQ.

Quoting rheinwaldner (Reply 121): Probably minor ones compared to whatever happened. But I agree, that the BMS does not depend on its location for it to function. And that there is no longer a job to do for the BMS once a cell runs away.

Don't underestimate the amount of work that it might take to do that. Some sensors, particularly passive things like thermocouples, often rely on the physical conductor distance between the sensor and the receiving circuit being very short. If you move the electronics further away, now you might need additional signal conditioning circuitry, and you might also potentially run into grounding/EMI problems.

Some years ago my dad was involved in something like this. Some people that were setting up a Space Shuttle Main Engine test stand wanted to move the controller off of the engine and into a room inside the hard stand, so that the controller would survive if the engine blew. They had no end of problems with it, and my dad was called in to help straighten things out. It took about six months to get it all working.

Quoting tdscanuck (Reply 135): I was just talking about that with some friends last night...the short answer is, I don't know, because I don't think anyone has been in this situation before. All other prior groundings (that we could think of) were preceded by multiple fatal crashes.

But would it be any different if the grounding were the result of a crash due to a battery fire? They would still have to find the root cause, no?

Quoting strfyr51 (Reply 140): The airplanes involved were among the first to be delivered. There have only BEEN 51 deliveries to date.

No, the ANA plane was one of the first delivered. And there have been 50 deliveries.

Quoting strfyr51 (Reply 140): install a third Ni cad battery in the rear compartment for the extra OOMPH starting the engines, apu or ground operation might take and drive ON!

As a passenger, I don't even know what to make of malarkey such as this. I hope that's not the general attitude at United.

Quoting tdscanuck (Reply 139): The only obvious issue I can see is that I'm sure there's some clearance requirement between the battery and surrounding parts, precisely to avoid meaningful heat damage to other parts from a runaway battery. I'm not sure how much room there is between the existing case and the point where they have to start revisiting the clearances or moving other things.

You could make it an aluminum box with some fins in the direction that is clear of obstacles, it would help dissipate the heat of potential leaks.

I'm appalled and angry that some people on here have suggested that the 787 was grounded prematurely and then comparing to past aircraft (737 crashes, DC10 crashes, etc, etc) which weren't grounded even after fatal accidents. The fact is that scores of people needlessly DIED due to problems with those aircraft. Deaths occurred before issues were identified and fixed.

While we still don't know the causes of the battery problems...I'm thankful we live in a different and safer aviation world now where issues are caught before a single fatality.

Quoting Aesma (Reply 144): You could make it an aluminum box with some fins in the direction that is clear of obstacles, it would help dissipate the heat of potential leaks.

Steel box. Wrapping flaming lithium with potentially flaming aluminum will likely not pass muster with the FAA.

Quoting max999 (Reply 145): I'm appalled and angry that some people on here have suggested that the 787 was grounded prematurely and then comparing to past aircraft (737 crashes, DC10 crashes, etc, etc) which weren't grounded even after fatal accidents.

Well, groundings don't happen very often...what else are we going to compare to? The point isn't so much that the 787 shouldn't be grounded, it's that the goalposts around grounding have obviously moved and it's legitimate to talk about how far they moved and whether they moved too far.

Quoting max999 (Reply 145): While we still don't know the causes of the battery problems...I'm thankful we live in a different and safer aviation world now where issues are caught before a single fatality.

Most issues are caught before a fatality *without* a grounding. The FAA drops AD's on a very regular basis, they haven't grounded an entire type for decades. I don't think anybody is arguing that the FAA shouldn't have taken action. I think there is legitimate discussion around whether the action they did take was too conservative or "just right" (I don't think anyone has argued their action wasn't strong enough, just maybe not fast enough). However, as I've said before, they had to take some action and, now that they've done it, they should see it through to the end properly and not try to second guess themselves. These issues are, fortunately, relatively rare so we'd be remiss to not learn all we can about this specific problem *and* the process so that the whole industry can do better next time.

Tom.

[Edited 2013-01-29 11:19:25]

Quoting tdscanuck (Reply 146): Steel box. Wrapping flaming lithium with potentially flaming aluminum will likely not pass muster with the FAA.

If it was, say, 2 cm aluminum plate with fins, the fire would have to get pretty damn hot.

Quoting tdscanuck (Reply 146): The FAA drops AD's on a very regular basis, they haven't grounded an entire type for decades.

ADs have very specific actions / fixes specified. The FAA cannot issue an AD if they don't know what to recommend to fix the problem. Therefore their only choice (short of risking more potentially catastrophic battery fires) is a grounding.

Quoting sankaps (Reply 148): The FAA cannot issue an AD if they don't know what to recommend to fix the problem.

Sure they can. For example:
"As a result of an in-flight, Boeing 787 battery incident earlier today in Japan, the FAA will issue an emergency airworthiness directive (AD) to address a potential battery fire risk in the 787 and require operators to temporarily cease operations. Before further flight, operators of U.S.-registered, Boeing 787 aircraft must demonstrate to the Federal Aviation Administration (FAA) that the batteries are safe."
http://www.faa.gov/news/press_releases/news_story.cfm?newsId=14233

An AD is simply a notification that there are aircraft that don't comply with regulations. It's strongly preferred that the AD include the action to restore compliance but that's not required.

Quoting sankaps (Reply 148): Therefore their only choice (short of risking more potentially catastrophic battery fires) is a grounding.

They had lots of choices...the AD could have imposed an operating limitation like "inspect the battery after every flight" or something like that. I'm not suggesting that that would actually work in this case, just that they can specify actions without fixing the problem.

Tom.