Tech/Ops Discussion Of The 787 Grounding

BoeEngr · Thu Jan 24, 2013 7:50 pm

Quoting Stitch (Reply 48):
Looks to still be planned to start in 10 minutes. There does not appear to be a public-facing option to follow in real-time - no webcast and CSPAN/CSPAN2 are not carrying it. There is a teleconference line, but you must RSVP and it appears to be limited to the press.

It's currently live on NBC:

http://video.msnbc.msn.com/nbcnews.com/50575001/#50575001

Stitch · Thu Jan 24, 2013 8:27 pm

Quoting BoeEngr (Reply 50):
It's currently live on NBC:

Thanks. I came in at the tail-end of the Q&A session, but I heard the spokeswoman noting there was a thermal runaway and short-circuiting inside the battery. The Chicago Sun-Times reported that federal officials found that all eight cells in the APU battery on the JL frame exhibited thermal damage.

BoeEngr · Thu Jan 24, 2013 8:31 pm

Quoting Stitch (Reply 51):
Quoting BoeEngr (Reply 50):
It's currently live on NBC:

Thanks. I came in at the tail-end of the Q&A session, but I heard the spokeswoman noting there was a thermal runaway and short-circuiting inside the battery. The Chicago Sun-Times reported that federal officials found that all eight cells in the APU battery on the JL frame exhibited thermal damage.

I didn't find it overly informative. She confirmed they have, to this date, ruled nothing out, and re-affirmed (multiple times) that they are investigating because they would not expect two battery incidents to occur within a two week period. She noted they will be reviewing whether anything was missed in the certification process, and see if changes need to be made.

She also stated that the JAL incident is being considered a "fire event", but that the NH incident is currently considered a "smoke event", not fire.

Stitch · Thu Jan 24, 2013 8:42 pm

Thank you.

Reuters is reporting the NTSB chairman stated the systems designed to prevent a battery fire aboard a 787 did not work as intended. Did she provide any specifics?

[Edited 2013-01-24 12:49:33]

Kaiarahi · Thu Jan 24, 2013 8:46 pm

Quoting Stitch (Reply 53):

She

BoeEngr · Thu Jan 24, 2013 8:47 pm

My interpretation was simply a statement that it shouldn't have caught fire, but it did, so the preventative measures didn't work. When asked for specifics, she stated "things like battery monitoring". That's how I recall it, anyway. Hopefully there will be a transcript.

Stitch · Thu Jan 24, 2013 8:49 pm

Thanks again.

The Seattle Times just posted an article on the press conference and the details announced.

KELPkid · Thu Jan 24, 2013 9:20 pm

Quoting Stitch (Reply 51):
Thanks. I came in at the tail-end of the Q&A session, but I heard the spokeswoman noting there was a thermal runaway and short-circuiting inside the battery. The Chicago Sun-Times reported that federal officials found that all eight cells in the APU battery on the JL frame exhibited thermal damage.

Would not short circuiting fall under the category of "manufacturing defect?"

I know that in laptop batteries, there are fuses (tiny pieces of metal) that are designed to melt away if a short happens. The battery pack needs replacement if the fuse ever gets blown...but the idea is that the fuse blows before you get a thermal runaway on a LiIon battery.

Pihero · Thu Jan 24, 2013 9:27 pm

Thanks for the link, Stitch.
The picture of the aft electronic bay is quite impressive.
Basically nothing new for another week, iF I understand correctly.
It also seems that they refuise to lump both events into one - just one - chain of events..

Quoting zeke (Reply 45):
In brand A aircraft

... and the NiCad batteries are rated at 37Ah instead of the 2x 65 of the Lion used here.

KELPkid · Thu Jan 24, 2013 9:27 pm

I'm thinking that in the JL incident, sitting on the ground might have contributed to the problem. Seems like the systems designed to ventilate smoke and heat from the E&E bays require 1) the aircraft to be fully on, and 2) a pressure differential to exist betwen the E&E bay and the outside world, with the E&E bay pressure being greater

Tristarsteve · Thu Jan 24, 2013 9:53 pm

Quoting zeke (Reply 45):
The 787 manual shows the 28 Vdc bus being normally powered by the 235 Vac bus via a power converter. I read the 787 FCOM on this part, it lacks any real depth to tell a lot of detail on the system. It does not show any input bus to charge the APU battery. I wonder if the main battery is continuously being charged, or if it has smarts in the system so it is only charged when required.

Just been looking at a B787 Schematics manual. There are too many abbreviations!, but

The Main battery is connected to a Hot battery bus. This is charged by a Battery Charger normaly fed by the Capt Instrument Bus which gets its power from 28V DC1. In normal operation the battery only powers the Hot battery Bus which has tiny loads on it.
The APU battery is connected to the APU Hot battery bus. This is charged by the APU Battery charger which gets power from the F/O Instrument bus which is normaly supplied by 28V DC C2.

Caveat. I have had no training on the aircraft, and it is very different to the B777 at this level.

tdscanuck · Thu Jan 24, 2013 10:29 pm

Quoting KELPkid (Reply 59):
I'm thinking that in the JL incident, sitting on the ground might have contributed to the problem.

That was *the* reason there was smoke on the main deck. None of the smoke containment features will work properly with the ECS off and sitting on the ground. The EE bay cooling fans will still run if the aircraft is powered up but, by themselves, they're not going to do the whole job.

Tom.

kanban · Fri Jan 25, 2013 1:43 am

While we've all heard or read the words from the press conf. here are some interesting pictures of the disassembly.. I think picture three has the second battery of the same plane disassembled in the background.. (I could be wrong)

http://www.king5.com/news/aerospace/...ing-on-battery-fire-188284081.html

nomadd22 · Fri Jan 25, 2013 1:51 pm

Not sure how seriously to take information from anonymous Japanese sources, but they're reporting that the charge controller was burnt up. I'm not clear on the boards being on or in the box or somewhere else.
http://www.chicagotribune.com/busine...rcuit-boards-012513,0,673990.story

"Circuit boards that control and monitor the performance of the plane's lithium-ion battery unit were charred and may be of little use to the teams investigating why the battery effectively melted"

CM · Fri Jan 25, 2013 2:40 pm

Quoting nomadd22 (Reply 64):
the charge controller was burnt up

Not surprising. The charge controller is a small circuit board which is integral to the battery. It is not the same thing as the battery charger itself, which is a separate box directly next to the battery.

nomadd22 · Fri Jan 25, 2013 5:07 pm

Quoting CM (Reply 65):
Not surprising. The charge controller is a small circuit board which is integral to the battery. It is not the same thing as the battery charger itself, which is a separate box directly next to the battery.

Got it. That was probably the part that tracked status of individual cells then. If it had quit first, I'd have expected the system to default to a lower maintenance voltage, like 29.5 to 30 volts.
Any idea if they're intelligent and monitored by the charger, or just simple thermistor like devices to reduce charge current to warm cells?

kanban · Fri Jan 25, 2013 5:59 pm

Aviation Herald has some new pictures including a hole in an electrode

http://avherald.com/h?article=45c377c5&opt=6144

Kaiarahi · Sat Jan 26, 2013 5:58 pm

NTSB update from Jan 24 (slide presentation). There are some new photos / graphics. http://www.ntsb.gov/investigations/2...3/boeing_787/JAL_B-787_1-24-13.pdf

Kaiarahi · Sat Jan 26, 2013 6:40 pm

There's also a new NTSB twitter update: "The battery charging unit passed all significant tests and no anomalies were detected."

So far we have:

- evidence of an internal short (damaged electrode)
- BCU appears to operate correctly (assuming there is no test design deficiency)
- limited information obtainable from the 2 internal circuit boards (which presumably control individual cell charging/monitoring)

So it *seems* (at least to my legal evidentiary mind) that the evidence is pointing towards one or a combination of:

- a cell manufacturing defect (electrode shorting because of improper manufacturing tolerances / FOD is a known cause of Li-Ion failures)
- an internal circuit board design or manufacturing defect.

Pihero · Sat Jan 26, 2013 10:02 pm

Thanks for these posts, Kaiarahi.
My git feelein has always been on manufacturing defects and / or quality control of the battery manufacurer.
That doesn't change the fact that the protection circuit should have worked as specs (but are we still in the realm of original specifications ? ).
Or am I way out of base ?

Aviaponcho · Sat Jan 26, 2013 10:21 pm

Pihero,
http://batteryuniversity.com/learn/article/lithium_ion_safety_concerns
If i'm reading correctly, no protection system can prevent a thermal runaway.... in case of a manufacturing defect.

Quote:
We need to keep in mind that these safety precautions are only effective if the mode of operation comes from the outside, such as with an electrical short or a faulty charger. Under normal circumstances, a lithium-ion battery will simply power down when a short circuit occurs. If, however, a defect is inherent to the electrochemical cell, such as in contamination caused by microscopic metal particles, this anomaly will go undetected. Nor can the safety circuit stop the disintegration once the cell is in thermal runaway mode. Nothing can stop it once triggered

Did I miss something ?

KC135Hydraulics · Sat Jan 26, 2013 10:50 pm

So are we saying that the NTSB may be incorrect in stating that Boeing's protection systems did not work correctly? What I've been reading in the last couple posts, is that if there is an internal defect with the battery, the protection systems are incapable of working to stop the battery from catching fire. If this is the case, then Boeing's systems are adequate to protect a properly manufactured battery but not an incorrectly manufactured battery. Is there any protection system available that can prevent a thermal runaway event in a defective battery? I'm assuming there is not, and in that case then the heat can and should be lifted from Boeing relatively soon.

kanban · Sun Jan 27, 2013 1:07 am

Quoting KC135Hydraulics (Reply 71):
What I've been reading in the last couple posts, is that if there is an internal defect with the battery, the protection systems are incapable of working to stop the battery from catching fire.

That's the way it sounds to me.. And I'm not sure how one would design a protection system that would preclude the failure from an internal defect.

Reading through the NTSB slide show, I can see why a runaway has a very limited duration.. there's just not enough material there.. It's looking like an improved (meaning slightly larger) containment box above a new drip shield/pan. One concern about a larger containment box though is would it provide more combustion room and defeat the purpose. So is it possible to quarter the battery box with double insulated steel walls and have only two cells in each space and still get the benefits out of the unit?

I wonder about ducting to the outside if the electrolyte and gasses are low temperature flammable.. In air probably no problem, but on the ground as the JAL was, what are the possibilities of igniting the CFRP?

The other thing I've been thinking about would be adding either closed circuit cameras continually watching the batteries, or ones that could be turned on and record whenever transient particular matter reached a predetermined threshold. I wouldn't expect these to become long term installations, but just another tool if there is another failure after the fleet is flying again.

Pihero · Sun Jan 27, 2013 2:01 am

Quoting KC135Hydraulics (Reply 71):
. Is there any protection system available that can prevent a thermal runaway event in a defective battery? I'm assuming there is not, and in that case then the heat can and should be lifted from Boeing relatively soon.

I really do not think that would be acceptable for any certifying authorityhowever dearly we would like to see the planes back in the air where they belong.To the contrary : a protection system that fails in 4% of the fleet (two airplanes out of fifty ) is way short of what we call acceptable risk levels.
That's why I posed the question on whether we're still in the realm of the original specifications.
Tom should provide more qualified opinion on this subject. I'm just an operator ( and even then, not of the 787 ).

WingedMigrator · Sun Jan 27, 2013 2:14 am

Quoting kanban (Reply 72):
So is it possible to quarter the battery box with double insulated steel walls and have only two cells in each space and still get the benefits out of the unit?

I'm not sure if that helps... all it would do for you is reduce the size of the fire, and maybe provide battery function during and after the fire. But you've still had a fire. It's the same response, both for immediate measures to ensure everyone's safety, and for the regulatory / public relations mess. So what problem were you solving?

Quoting kanban (Reply 72):
what are the possibilities of igniting the CFRP?

I'm curious about this too. How flammable is CFRP? Epoxy resin seems like a pretty good fuel, at least compared to aluminum...

nomadd22 · Sun Jan 27, 2013 2:25 am

Thanks for finding that Kaiarahi. It answers just about all the questions I had about the design.
Packing the cells like that surprises me a little, given the nature of Lithium batteries. An extra 20 pounds of steel and 2 inches of space should let them come up with a segmented design that would isolate the cells from each other. I'm not in aviation, other than communications, but in my business we'd want to keep whatever happened from happening again, and make sure that it would be handled better if it did happen.
I'm guessing that a bunch new cells and cells from the same batch as the troublemakers are being dissected and analyzed to check for manufacturing issues.

Kaiarahi · Sun Jan 27, 2013 2:37 am

Quoting nomadd22 (Reply 75):
Thanks for finding that Kaiarahi. It answers just about all the questions I had about the design.
Packing the cells like that surprises me a little, given the nature of Lithium batteries.

My first thoughts around the packing are that Li-Ion is mostly used (and designed) for consumer electronic applications, where space is at a premium. Perhaps there's a paradigm shift that needs to happen here, where the battery engineers are not fixated on minimizing physical space.

I can't say much more, but my eldest son is an exec at Yuasa ....

seat55a · Sun Jan 27, 2013 2:58 am

Quoting kanban (Reply 72):
I'm not sure how one would design a protection system that would preclude the failure from an internal defect.

I think one must expand the scope of thinking about fault protection, to include the Quality Control (and production quality engineering) of the cells and the battery assembly. I mean, the chance that a defect can pass through those processes must be part of the fault probability calculation for the airplane as a whole system.

Quoting nomadd22 (Reply 75):
I'm guessing that a bunch new cells and cells from the same batch as the troublemakers are being dissected and analyzed to check for manufacturing issues.

Yes, and suppose an issue is found (with one or more batches), would it not be necessary to explain why the issue is limited to those batches and how it got through? Until they could do so, wouldn't all the production be equally suspect? It would be a big step in understanding for sure, but wouldn't make everything O.K.

[Edited 2013-01-26 19:00:56]

KELPkid · Sun Jan 27, 2013 7:45 am

Quoting WingedMigrator (Reply 74):

I'm curious about this too. How flammable is CFRP? Epoxy resin seems like a pretty good fuel, at least compared to aluminum...

Aluminum is most assuredly flammable.

You haven't thrown beer cans into the camp fire?

Granted, it doesn't go up like magnesium in your high school chemistry class...but it does burn. Aluminum was a key ingredient in the Space Shuttle Solid Rocket Booster propellant....

[Edited 2013-01-26 23:48:07]

deltal1011man · Sun Jan 27, 2013 10:19 am

Just got to say thanks to CM for starting a thread that isn't full of trolls.

Quoting CM (Reply 18):
Not to create a theme, but Would you believe you can get both mechanical and aero degrees with nothing more than grade 10 chemistry? I hated it, did poorly in it, and retained none of it. I will truly be of no use to you on topics of chemistry.

Ha!
Or, say never mind to those degrees, go and get and A&P and a business degree and just go into management (and never, ever have to take a Chemistry class(even in HS). Math = good, Chemistry....run, run as fast as you can!)

Quoting KC135Hydraulics (Reply 21):
Much prefer the discussion on this forum than on civil aviation! I also posted this picture there, but I thought it'd be interesting for conversation here. These are the batteries on the KC-135. They are lead-acid, 28v. These are kept in the latrine... as you can see, the toilet on the left and the urinal can to the right.

Whoa. Could make for a crappy day if the you hit some kind of chop.... (pun intended)

Quoting moose135 (Reply 27):
If it even got to that point, I suspect Boeing might eat some (or most) of the cost of repairs simply to avoid the PR issue of having a 787 written off at this stage of the game.

Agree. I don't see Boeing letting this bird get scraped unless it is reeeeeally bad off.

Quoting moose135 (Reply 27):
And it was never that bright in there. Aim carefully!

no kidding.

sunrisevalley · Sun Jan 27, 2013 12:58 pm

Am I correct in my understanding that in the two incidents in question ( JL and ANA) the batteries had relatively low "hours" and that there are other batteries in service with many more hours on them.
Does it make sense to take each new battery and run it through charge/discharge cycles for "X" hours to take care of the possibility of a manufacturing fault. Perhaps the testing process should require the battery to be able to cope with abnormal loads , say somewhere between 3 and 10% .
My

worth

Stitch · Sun Jan 27, 2013 4:25 pm

Quoting sunrisevalley (Reply 80):
Am I correct in my understanding that in the two incidents in question ( JL and ANA) the batteries had relatively low "hours" and that there are other batteries in service with many more hours on them.

The Ship's Battery on the NH bird was replaced in October. The airframe was delivered in January 2012, so that would make the original battery upwards of 10 months old. The APU battery on that frame would be 12 months old.

JA801A, NH's first delivery, is 17 months old. JA802A is 16 months old and JA805A is 13 months old. If they have their original delivery batteries, then they will be at least that old.

[Edited 2013-01-27 08:29:00]

tdscanuck · Sun Jan 27, 2013 10:04 pm

Quoting kanban (Reply 72):
I wonder about ducting to the outside if the electrolyte and gasses are low temperature flammable.. In air probably no problem, but on the ground as the JAL was, what are the possibilities of igniting the CFRP?

Quoting WingedMigrator (Reply 74):
I'm curious about this too. How flammable is CFRP? Epoxy resin seems like a pretty good fuel, at least compared to aluminum...

Although not totally inflammable, CFRP doesn't burn as well as aluminum. It's harder to light and takes longer to burn through. In virtually ever conceivable fire situation, CFRP is better to have around.

Quoting Pihero (Reply 73):
That's why I posed the question on whether we're still in the realm of the original specifications.
Tom should provide more qualified opinion on this subject.

The original specifications would be contained in something called a Specification Control Document (SCD) that goes from Boeing to the supplier an defines everything in nauseating detail (these things are hundreds of pages for even very simple components...for a battery it would be huge). I do not know if we're in the range of the SCD or not; even if I had the document it would be highly proprietary.

Quoting WingedMigrator (Reply 74):
I'm not sure if that helps... all it would do for you is reduce the size of the fire, and maybe provide battery function during and after the fire. But you've still had a fire.

That's never going to go away. They'll have to convince the FAA/NTSB that they've pushed the probability of a fire down (by identifiying and fixing whatever caused these two fires) *and* convince them you have the fire properly contained.

Quoting sunrisevalley (Reply 80):
Does it make sense to take each new battery and run it through charge/discharge cycles for "X" hours to take care of the possibility of a manufacturing fault.

Quoting sunrisevalley (Reply 80):
Perhaps the testing process should require the battery to be able to cope with abnormal loads , say somewhere between 3 and 10% .

I'd be appalled if this wasn't already part of the manufacturing procedure. It's too obvious to not be.

Tom.

seat55a · Sun Jan 27, 2013 11:03 pm

Quoting sunrisevalley (Reply 80):
Does it make sense to take each new battery and run it through charge/discharge cycles for "X" hours to take care of the possibility of a manufacturing fault.

Is extended quality testing of 100% of articles really normal for any manufacturing process? That's far more than Quality Control. It expresses zero confidence in the quality aspects of the manufacturing process. I don't see how the morale of the company could survive this. I wonder also about marketability of the products where the company itself has this low level of confidence in its processes. I am certainly not an expert in manufacturing Q C and happy to be told I'm wrong.

If the incidents were due to failure of batteries that did undergo such extended testing (if the cause of the fault is the batteries), that's not too good for return to flight.

(edit: clarification)

[Edited 2013-01-27 15:06:02]

[Edited 2013-01-27 15:06:31]

zanl188 · Mon Jan 28, 2013 12:17 am

Todays NTSB update:

January 27, 2013
WASHINGTON – The National Transportation Safety Board today released a fourth update on its investigation into the Jan. 7 fire aboard a Japan Airlines Boeing 787 at Logan International Airport in Boston. The fire occurred after the airplane had landed and no passengers or crew were onboard.

The event airplane, JA829J was delivered to JAL on December 20, 2012. At the time of the battery fire, the aircraft had logged 169 flight hours with 22 cycles. The auxiliary power unit battery was manufactured by GS Yuasa in September 2012.

NTSB investigators have continued disassembling the internal components of the APU battery in its Materials Laboratory in Washington, and disassembly of the last of eight cells has begun. Examinations of the cell elements with a scanning-electron microscope and energy-dispersive spectroscopy are ongoing.

A cursory comparative exam has been conducted on the undamaged main battery. No obvious anomalies were found. More detailed examination will be conducted as the main battery undergoes a thorough tear down and test sequence series of non-destructive examinations.

In addition to the activities at the NTSB lab, members of the investigative team continue working in Seattle and Japan and have completed work in Arizona. Their activities are detailed below.

ARIZONA
The airworthiness group completed testing of the APU start power unit at Securaplane in Tucson and the APU controller at UTC Aerospace Systems in Phoenix. Both units operated normally with no significant findings.

SEATTLE
Two additional NTSB investigators were sent to Seattle to take part in FAA’s comprehensive review. One of the investigators will focus on testing efforts associated with Boeing's root cause corrective action efforts, which FAA is helping to lead. The other will take part in the FAA's ongoing review of the battery and battery system special conditions compliance documentation.

JAPAN
The NTSB-led team completed component examination of the JAL APU battery monitoring unit at Kanto Aircraft Instrument Company, Ltd., in Fujisawa, Kanagawa, Japan. The team cleaned and examined both battery monitoring unit circuit boards, which were housed in the APU battery case. The circuit boards were damaged, which limited the information that could be obtained from tests, however the team found no significant discoveries.

Additional information on the NTSB’s investigation of the Japan Airlines B-787 battery fire in Boston can be found at http://go.usa.gov/4K4J

The NTSB will provide another factual update on Tuesday, Jan. 29, or earlier if developments warrant. To be alerted to any updates or developments, follow the NTSB on Twitter at www.twitter.com/ntsb
#NTSB#

[Edited 2013-01-27 16:19:01]

tdscanuck · Mon Jan 28, 2013 12:52 am

Quoting Seat55A (Reply 83):
Is extended quality testing of 100% of articles really normal for any manufacturing process?

For safety critical applications, it's absolutely normal.

Quoting Seat55A (Reply 83):
That's far more than Quality Control. It expresses zero confidence in the quality aspects of the manufacturing process.

No. It's the reality that complicated assemblies with hundreds or thousands of components have no realistic chance of achieving acceptable reliability through statistical control, even if the individual process are really good. The chance that one of your thousands of parts is bad is too high. If you need 100% pass, you do 100% inspection. Anything less will *always* allow something through, albeit at potentially very low rate. For many types of goods, the potential of a bad unit getting through is just economic and you roll it into the cost of doing business. That's not generally an acceptable practice where a faulty unit could kill someone. Even something as mundane as pre-filled syringes (for vaccines and such) that can be manufactured in the millions and only have four or five parts are 100% inspected.

Quoting Seat55A (Reply 83):
I don't see how the morale of the company could survive this. I wonder also about marketability of the products where the company itself has this low level of confidence in its processes.

It has nothing to do with low confidence. Suppose you've got a 6-sigma process (which almost nobody in aerospace has because their volumes are too low) on every single part you use and your assembly has 1000 parts. There is a 4 per million chance that any *one* of the parts is bad. There is a 4000 per million (0.1%) chance that your assembly is bad due to a single bad part even with absolutely top-notch process confidence, and that's not counting potential errors in all the assembly steps. In the real world, you've got redundancy and part failures aren't independent and other stuff, but the point still stands. Once you have very complicated products and you don't accept defects, you can't rely on process alone with any level of confidence.

Tom.

seat55a · Mon Jan 28, 2013 1:43 am

Quoting zanl188 (Reply 84):

Todays NTSB update:
. . . .
January 27, 2013
SEATTLE
Two additional NTSB investigators were sent to Seattle to take part in FAA’s comprehensive review. One of the investigators will focus on testing efforts associated with Boeing's root cause corrective action efforts,

Is this code for "Boeing has a proposed fix and they need people to try and break it"?

Kaiarahi · Mon Jan 28, 2013 2:20 am

Quoting zanl188 (Reply 84):
The NTSB-led team completed component examination of the JAL APU battery monitoring unit at Kanto Aircraft Instrument Company, Ltd., in Fujisawa, Kanagawa, Japan. The team cleaned and examined both battery monitoring unit circuit boards, which were housed in the APU battery case. The circuit boards were damaged, which limited the information that could be obtained from tests, however the team found no significant discoveries.

Sounds to me that it's getting closer and closer to cell manufacturing defects (cue the shorted electrode), which are the cause of the majority of Li-Ion failures (rcair1 cited a study, which I can't find anymore on the civav compost heap). So far, the charger (Securaplane) and the monitoring boards (Kanto) *seem* to be OK.

My source at Yuasa suggests that they're reviewing QA processes and working on designing better isolation of cells so that thermal runaway does not propagate. In a sense, the latter is containment - within the battery itself, rather than containing the whole unit.

HAWK21M · Mon Jan 28, 2013 6:16 am

Anyone having the list of snags till date on the type.
One Engine issue during test conditions.
One Electrical fire during test conditions that was alleged attributed to a forgotton tool .....
These couple of thermal runways last few days.

KC135Hydraulics · Mon Jan 28, 2013 9:42 am

Quite a few generator failures in flight as well Hawk. Definitely on United and Qatar airlines, maybe others too.

ferpe · Mon Jan 28, 2013 6:53 pm

I feel really sorry for the guys up northwest, the solution seems elusive....

Then it is good to know that one can always rely on our airline ground crews to solve the problem:

(thought it was really nice Big grin

)

[Edited 2013-01-28 10:54:38]

canoecarrier · Mon Jan 28, 2013 7:46 pm

Good discussion here. I won't add much to the discussion and won't post other than this but as Kaiarahi mentioned the Civ-Av threads have become a septic tank so to say.

The Seattle Times is reporting that the NTSB has cleared the battery charger of any faults in the Boston incident and that Japanese investigators have shifted their investigation from the battery manufacturer (Yuasa) to the the manufacturer of the battery monitoring system (Kanto).

http://seattletimes.com/html/busines...2020230485_apasjapanboeing787.html

Aviaponcho · Mon Jan 28, 2013 9:27 pm

Bonsoir,

Tracking tweets I find this pdf from Airbus on Lithium batteries

http://www.multimedia-support.net/fl...-safety-conference/docs/20-3-1.pdf

HAWK21M · Tue Jan 29, 2013 12:09 pm

I've heard the AI ones had Pack trip issues....

prebennorholm · Tue Jan 29, 2013 3:29 pm

Quoting Aviaponcho (Reply 92):
Tracking tweets I find this pdf from Airbus on Lithium batteries

http://www.multimedia-support.net/fl...1.pdf

I provided this link a week ago in the a.net GA forum. Maybe it made its way to Twitter from there???

Page #13 is interesting, especially:

- Independence of cells / cooling areas between cells
- Venting areas within the battery
- Specific venting outside the battery/aircraft when relevant

If this Airbus safety conference had taken place today, and not almost a year ago, then these things would have created a lot of questions from the audience.

But Airbus is silent today. I understand that.

But last week an Airbus spokesman (not JL) did comment hard pressed by Reuters. He said that the A350 containment system was more robust, and they believe it would pass certification without issues. But in case certification conditions got changed, then the A350 would be modified accordingly, which would involve a potential delay depending on the circumstances.

Okie · Tue Jan 29, 2013 4:04 pm

Lots of obvious things keep popping up that one would assume would be addressed long before now.

There are a lot of systems on the 87 that are powered with VFD's which are notorious bad neighbors.
I do not know the architecture of the system or if they use 6, 12 or 18 pulse drives.

What I would say, if you would try to sell me that a high emf harmonic generated by one of the VFD's of a half wave was introduced to the AC bus at the same time the SCR of the battery charger was firing and it damaged the separator of a battery cell then I would sure listen.

Okie

tdscanuck · Tue Jan 29, 2013 4:37 pm

Quoting okie (Reply 95):
There are a lot of systems on the 87 that are powered with VFD's which are notorious bad neighbors.
I do not know the architecture of the system or if they use 6, 12 or 18 pulse drives.

The VFD's "hide" behind the high voltage DC buses. The HVDC buses feed motor controllers that change the DC into appropriate frequency/voltage AC to run the VFD's. The pipe from the motor controllers to the VFD's is dedicated to each VFD. I don't think there's any way for interference to propagate back upstream to the DC side, which is where it would have to go to (eventually) get back into the 28VDC or 115VAC buses that run all the avionics.

Tom.

Okie · Tue Jan 29, 2013 5:05 pm

Quoting tdscanuck (Reply 96):

The VFD's "hide" behind the high voltage DC buses

Yes, I know, something I deal with everyday but larger drives with multiple 3,000+ amp DC busses.
We deal with the harmonics issue with phasing transformers (12 & 18 pulse) and as well as line reactors on the AC supply side for the DC buss to attinuate the harmonics.
I would doubt that an aircraft would take that kind of a weight penalty but again I do not know the architecture of the system.

Okie

KC135Hydraulics · Tue Jan 29, 2013 8:02 pm

What is a VFD and what does it do?

Okie · Tue Jan 29, 2013 8:23 pm

Quoting KC135Hydraulics (Reply 98):
What is a VFD and what does it do?

Varible Frequency Drive.
Used to control speed and torque of a three phase electric motor. There are some exotic 5 and 11 phase out there but not involved here I believe.
Used on the Air Con packs and some hydraulics on the 87 (others I am sure)

A VERY simple explanation would be in the case an air con pack would be that you slow the device down or speed it up in relation demand on the system, saving energy vs the previous applications of running the packs full speed all the time and control with bypass and out flow. Same with a hydraulic pump it just creeps along with nothing going on in the system then speeds up when some hydraulic demand is required.

VFD's are wonderful devices just bad neighbors.

Okie

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