FAA Grounds 787s
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hetfield, not sure I understand exactly - are you saying a runaway takes place so rapidly that no monitoring can flag the problem more than ~minutes before it's going off?
I'm obviously not familiar with batteries but presumably cell imbalance (voltage or temperature or something else) can be measured, and it's slowly (or not so slowly) getting worse over time?
I'm obviously not familiar with batteries but presumably cell imbalance (voltage or temperature or something else) can be measured, and it's slowly (or not so slowly) getting worse over time?
Dog Tired
Yes, common to have APU running on it's own. Almost all have auto shutdown and some even fire a bottle on their own.
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hetfield, not sure I understand exactly - are you saying a runaway takes place so rapidly that no monitoring can flag the problem more than ~minutes before it's going off?
The messenger (BMS) may be shot, if one cell
off.IMHO, wrong place to put in a monitoring unit.
Just have a look to upper left/right with the PCB after/before:
Last edited by hetfield; 28th Jan 2013 at 18:16.
Do you mean like Airbus has had for the last twenty years?
There are few here getting hung up on this battery and its purpose. It isn't much different to any other big jet.
The battery type is unusual but it does the same as most others. Boeings and Airbus.
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The battery type is unusual but it does the same as most others. Boeings and Airbus.
.It doesn't matter to be "unusual".
It matters, is it safe?
Last edited by hetfield; 28th Jan 2013 at 19:02.
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My point being that if the Main and APU batteries are in casual use in flight, and the FAA has specified a "minimum Charge" to adhere to the definition of "BACKUP", then one or the other or both are constantly being charged, discharged, and for most of the time, the Battery is merely a "conductor" in line, neither powering or being reharged alone, but in constant connection.
My assumption is that the "Minimum charge" is somewhere near "Maximum Charge", so the Battery will be in line enroute. Especialy so with the MAINBAT.
Once the APU starts, can it shutdown whilst the APUBATT is below minimum charge? Since the APUBATT is charged by the vdcSG, the BATT must be restored to full charge, or may not be able to start the APU (a second time) in an emergency.
Having started the APU, perhaps draining the Battery, how can the Battery comply in flight?
This is the thing. Using a Backup Battery in its emergency configuration, not in an emergency, fails even the definition of BACKUP.......
My assumption is that the "Minimum charge" is somewhere near "Maximum Charge", so the Battery will be in line enroute. Especialy so with the MAINBAT.
Once the APU starts, can it shutdown whilst the APUBATT is below minimum charge? Since the APUBATT is charged by the vdcSG, the BATT must be restored to full charge, or may not be able to start the APU (a second time) in an emergency.
Having started the APU, perhaps draining the Battery, how can the Battery comply in flight?
This is the thing. Using a Backup Battery in its emergency configuration, not in an emergency, fails even the definition of BACKUP.......
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Well surprise, surprise, they're now looking at the battery charging circuit.
It was drilled into us early doors on the Tristar and DC 10 that one of the worst malfunctions was thermal runaway of batteries caused by a malfunctioning battery charger.
I don't blame Boeing for going for the easiest option, but (from this distance) I always thought that it looked just like thermal runaway - symptoms fitted perfectly. Sadly, not as cheap a fix as a different battery - unless of course the battery charger is controlled by software.
It was drilled into us early doors on the Tristar and DC 10 that one of the worst malfunctions was thermal runaway of batteries caused by a malfunctioning battery charger.
I don't blame Boeing for going for the easiest option, but (from this distance) I always thought that it looked just like thermal runaway - symptoms fitted perfectly. Sadly, not as cheap a fix as a different battery - unless of course the battery charger is controlled by software.
Last edited by Dengue_Dude; 28th Jan 2013 at 20:17.
Lyman.
The Main Bat is only connected to a live bus when no other electric source is available and Bat Switch 'on'. Therefore it is not discharging unless there is a power failure.
The APU Bat is charged from the F/O's Instrument Bus. This can be powered from a variety of sources, not just the APU. EG. Ext power, Eng Gen. After starting the APU, the APU Bat does nothing but sit there and get recharged. (Unless towing without APU/ENG GEN in which case it powers the Nav lights)
The Main Bat is only connected to a live bus when no other electric source is available and Bat Switch 'on'. Therefore it is not discharging unless there is a power failure.
The APU Bat is charged from the F/O's Instrument Bus. This can be powered from a variety of sources, not just the APU. EG. Ext power, Eng Gen. After starting the APU, the APU Bat does nothing but sit there and get recharged. (Unless towing without APU/ENG GEN in which case it powers the Nav lights)
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The Main Bat is only connected to a live bus when no other electric source is available and Bat Switch 'on'. Therefore it is not discharging unless there is a power failure.
The APU Bat is charged from the F/O's Instrument Bus. This can be powered from a variety of sources, not just the APU. EG. Ext power, Eng Gen. After starting the APU, the APU Bat does nothing but sit there and get recharged. (Unless towing without APU/ENG GEN in which case it powers the Nav lights)
The APU Bat is charged from the F/O's Instrument Bus. This can be powered from a variety of sources, not just the APU. EG. Ext power, Eng Gen. After starting the APU, the APU Bat does nothing but sit there and get recharged. (Unless towing without APU/ENG GEN in which case it powers the Nav lights)
The Main Bat as well as the APU bat f
up!
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TURIN
Many thanks. From that, ANA Main Battery had a spontaneous failure? It must meet basic charge level to launch, so would not be charged after T/O, right?
Is the only start voltage available for APU the APUBATT? It seems unusual to require a backup battery to Start the APU in normal ops. Because if an airborne start, the APU BATT might go below legal level, and be unable to start the APU in an actual abnormal?
Not for use during Flight?
Many thanks. From that, ANA Main Battery had a spontaneous failure? It must meet basic charge level to launch, so would not be charged after T/O, right?
Is the only start voltage available for APU the APUBATT? It seems unusual to require a backup battery to Start the APU in normal ops. Because if an airborne start, the APU BATT might go below legal level, and be unable to start the APU in an actual abnormal?
Not for use during Flight?
Apologies, deleted that post because it should have been sent to tech log as
a follow up to a previous post
cwatters:
They must have some sort of diagnostics internal to the charger / monitoring and
data would ideally be stored locally. The fdr only has limited storage capacity,
but a subset of that data, say bus voltage and any fault codes, might be sent to
it as well. If the data from the charger / battery is lost, the limited fdr data
may be the reason why we have only been told thus far that a battery over charge
condition didn't occur. The fdr data may be the only thing they have at present.
pax2908
As for the thresholds, they would be set below cell voltage and temperature
limits. If the charger is really smart, it should also be able to predict cell
failure before it causes a problem, by comparing known good cell characteristics
against data from individual cells over time. Where data logging is used, it's
normally stored to non volatile memory within the subsystem. Often flash memory,
much like you would find in a usb memory stick, but manufactured and qualified to
a much higher specification.
a follow up to a previous post
cwatters:
They must have some sort of diagnostics internal to the charger / monitoring and
data would ideally be stored locally. The fdr only has limited storage capacity,
but a subset of that data, say bus voltage and any fault codes, might be sent to
it as well. If the data from the charger / battery is lost, the limited fdr data
may be the reason why we have only been told thus far that a battery over charge
condition didn't occur. The fdr data may be the only thing they have at present.
pax2908
As for the thresholds, they would be set below cell voltage and temperature
limits. If the charger is really smart, it should also be able to predict cell
failure before it causes a problem, by comparing known good cell characteristics
against data from individual cells over time. Where data logging is used, it's
normally stored to non volatile memory within the subsystem. Often flash memory,
much like you would find in a usb memory stick, but manufactured and qualified to
a much higher specification.
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Originally Posted by Lyman
ANA Main Battery had a spontaneous failure? It must meet basic charge level to launch, so would not be charged after T/O
(8) Any lithium ion battery installation whose function is required for safe operation of the airplane must incorporate a monitoring and warning feature that will provide an indication to the appropriate flight crewmembers whenever the state-of-charge of the batteries has fallen below levels considered acceptable for dispatch of the airplane.
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Hi HazelNuts39,
The language is not specific, though I anticipate changes in the text.
"....must incorporate a monitoring and warning feature....etc."
The operant is "for dispatch". Since charging is not prohibited, specifically, it leaves rhe option open. BUT, any use of the battery would drop the voltage below minimum (possibly) and instantly violate the condition.
However, "for dispatch" is a threshold.
The meaning of "backup" stands alone, it must take precedence over any function that is not part of the definition. So launching, having met the threshold, implies that the voltage should be available throughout the flight, barring malfunction.
FAA regs are minimums, so I fall back on TURIN......"The Main Bat is only connected to a live bus when no other electric source is available and Bat Switch 'on'. Therefore it is not discharging unless there is a power failure."
A guess would be that ANA charged the batteries to legal, isolated (sel off), and took off. The runaway having begun prior to T/O, the charger would not be in use, but the die was cast....why would one charge after T/O? If the voltage drops below minimum, I suppose the battery could be charged, but still isolated from live bus.......that may change.
The solution is in the interface between FAA and Boeing, each working at cross purpose, but theoretically in concert. Cross purpose is not defeating, it is entirely logical, they have a different mission. FAA has to walk the tighter line, imo; they want Boeing to succeed, (promote aerospace business), while ensuring high standards of safety.
Each of them work to the edge of the mission, and the result is safe prosperous travel....
The language is not specific, though I anticipate changes in the text.
"....must incorporate a monitoring and warning feature....etc."
The operant is "for dispatch". Since charging is not prohibited, specifically, it leaves rhe option open. BUT, any use of the battery would drop the voltage below minimum (possibly) and instantly violate the condition.
However, "for dispatch" is a threshold.
The meaning of "backup" stands alone, it must take precedence over any function that is not part of the definition. So launching, having met the threshold, implies that the voltage should be available throughout the flight, barring malfunction.
FAA regs are minimums, so I fall back on TURIN......"The Main Bat is only connected to a live bus when no other electric source is available and Bat Switch 'on'. Therefore it is not discharging unless there is a power failure."
A guess would be that ANA charged the batteries to legal, isolated (sel off), and took off. The runaway having begun prior to T/O, the charger would not be in use, but the die was cast....why would one charge after T/O? If the voltage drops below minimum, I suppose the battery could be charged, but still isolated from live bus.......that may change.
The solution is in the interface between FAA and Boeing, each working at cross purpose, but theoretically in concert. Cross purpose is not defeating, it is entirely logical, they have a different mission. FAA has to walk the tighter line, imo; they want Boeing to succeed, (promote aerospace business), while ensuring high standards of safety.
Each of them work to the edge of the mission, and the result is safe prosperous travel....
Last edited by Lyman; 28th Jan 2013 at 22:46.
Sorry, haven't the time or energy to go through the whole of this thread, so apologies if this has been covered.
A Chemical Engineer friend of mine told me that Lithium Cobalt mix is a Fire Chiefs worst nightmare, a by product of the fire is oxygen, so there is no chance of smothering it, it just goes on to make its' own O2, and pouring water on it causes a very big bang, so they can only concentrate on cooling the surrounds until it burns itself out.
I've read a couple of posts that suggest that Boeing changed to Lithium Magnesium -so that's alright then, I'd rather be on board a 787 suffering a serious Lithium Magnesium fire than a Lithium Cobalt fire. Much more comforting on an ETOPS sector.
Interesting that these batteries are forbidden to be carried in bulk as freight on passenger aircraft - freighter crews being expendable as recently proved by UPS - but it's OK to have the equivalent of a shipload of them under the floor of a passenger 787.
I wish I was a US Lawyer, I guess there will be a lot of rich ones soon, wonder of Boeing will survive the Loss of Revenue litigation from the airlines with grounded 787's ? Or will they sue the FAA ? US taxpayer are you listening ?
Not good.
A Chemical Engineer friend of mine told me that Lithium Cobalt mix is a Fire Chiefs worst nightmare, a by product of the fire is oxygen, so there is no chance of smothering it, it just goes on to make its' own O2, and pouring water on it causes a very big bang, so they can only concentrate on cooling the surrounds until it burns itself out.
I've read a couple of posts that suggest that Boeing changed to Lithium Magnesium -so that's alright then, I'd rather be on board a 787 suffering a serious Lithium Magnesium fire than a Lithium Cobalt fire. Much more comforting on an ETOPS sector.
Interesting that these batteries are forbidden to be carried in bulk as freight on passenger aircraft - freighter crews being expendable as recently proved by UPS - but it's OK to have the equivalent of a shipload of them under the floor of a passenger 787.
I wish I was a US Lawyer, I guess there will be a lot of rich ones soon, wonder of Boeing will survive the Loss of Revenue litigation from the airlines with grounded 787's ? Or will they sue the FAA ? US taxpayer are you listening ?
Not good.
Last edited by ExSp33db1rd; 29th Jan 2013 at 02:35.
Hetfield.
I am not apologising for the failures, just trying to explaine to Lyman about the system as he/she is misunderstanding lots.
Lyman. The bat switches stay selected on in flight. The breakers and contactors are controlled automatically.
The batteries will still be charging if necessary after engine start. Maintenance and flt crew check list items will determine if bat state is ok for dispatch. This is standard on all big jets. In flight the APU Bat will only be used to start the APU if NO OTHER SOURCE IS AVAILABLE.
Hope this helps.
I am not apologising for the failures, just trying to explaine to Lyman about the system as he/she is misunderstanding lots.
Lyman. The bat switches stay selected on in flight. The breakers and contactors are controlled automatically.
The batteries will still be charging if necessary after engine start. Maintenance and flt crew check list items will determine if bat state is ok for dispatch. This is standard on all big jets. In flight the APU Bat will only be used to start the APU if NO OTHER SOURCE IS AVAILABLE.
Hope this helps.
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There is another difference in the 787 design (main battery use)?
Note: The rationale for this post will be reviewed . The "unprecedented" is not what was imagined. Post will suffer revision, corrections or even deleted.
Hi,
TURIN:
This is unprecedented. Boeing innovated designing the first airliner using Li Ion batteries (as the main battery) AND ALSO:
Using a battery that only delivers (higher) current when there is a (very rare) failure in the DC bus.
This means:
The ANA battery (certainly older than JAL APU unit) probably NEVER* WAS USED. I.e. never delivered (high) current. Just was kept "floating" since was manufactured.
This is a radically different use of a typical battery. At least we can say this could introduce new (and unknown) possibilities. It is a truly backup unit. Not being "exercised" like (as i imagine) in practically 100% of vehicles (land, water and air, main batteries)
AFAIK the designers made the same in A380 (emergency lighting).
The failure mode of the ANA battery (or the reason for the failure) now becomes clear to me could be another completely different. Even with the same charger could be another reason. I am assuming BOS JAL 787 started the APU using the battery. And ANA 787 had no DC bus failure requiring main battery use before the incident.
The timing between both cases (intriguing) could be just a coincidence.
APU battery operates differently than main battery that just waits (charged) an emergency (in the DC bus)
I am assuming something (that will be verified) from what i learned so far on 787. (Use of Diode, APU opp. etc.) Unfortunately we donīt have yet all information (schematic diagrams, etc.) to understand completely the issue.
(*) Unless there is a discharger (between the battery and the diode unit) to cycle it (cycles of charging and discharging, during normal operation) Something not feasible for deeper discharge. (you may need it when it was recovering from the "exercise")
Note: The rationale for this post will be reviewed . The "unprecedented" is not what was imagined. Post will suffer revision, corrections or even deleted.
Hi,
TURIN:
This is unprecedented. Boeing innovated designing the first airliner using Li Ion batteries (as the main battery) AND ALSO:
Using a battery that only delivers (higher) current when there is a (very rare) failure in the DC bus.
This means:
The ANA battery (certainly older than JAL APU unit) probably NEVER* WAS USED. I.e. never delivered (high) current. Just was kept "floating" since was manufactured.
This is a radically different use of a typical battery. At least we can say this could introduce new (and unknown) possibilities. It is a truly backup unit. Not being "exercised" like (as i imagine) in practically 100% of vehicles (land, water and air, main batteries)
AFAIK the designers made the same in A380 (emergency lighting).
The failure mode of the ANA battery (or the reason for the failure) now becomes clear to me could be another completely different. Even with the same charger could be another reason. I am assuming BOS JAL 787 started the APU using the battery. And ANA 787 had no DC bus failure requiring main battery use before the incident.
The timing between both cases (intriguing) could be just a coincidence.
APU battery operates differently than main battery that just waits (charged) an emergency (in the DC bus)
I am assuming something (that will be verified) from what i learned so far on 787. (Use of Diode, APU opp. etc.) Unfortunately we donīt have yet all information (schematic diagrams, etc.) to understand completely the issue.
(*) Unless there is a discharger (between the battery and the diode unit) to cycle it (cycles of charging and discharging, during normal operation) Something not feasible for deeper discharge. (you may need it when it was recovering from the "exercise")
Note: The rationale for this post will be reviewed . The "unprecedented" is not what was imagined. Post will suffer revision, corrections or even deleted.
Last edited by Jetdriver; 30th Jan 2013 at 03:17.
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Li Ion as main battery in 787 and APU battery use
Hi,
And with Li Ion there is another reason for this. It can increase itīs voltage (during charging) providing a false indication of "health" and not be able to deliver the required energy (to the bus) if an emergency situation requires it (bus voltage below, i estimate ~ 30 V). A cell that fall below a given threshold very probably will never recover. Lead Acid in this aspect can go to zero, exhibit a high internal resistance and FULLY RECOVER. I faced this situation and after charging (longer time was required) it returned to the same (anti) capability.
Question:
JAL in BOS probably started the APU using the battery? If so the runaway probably started with hot cells (after high current use starting APU) and when receiving high current (with regime to recharge "fast")
And with Li Ion there is another reason for this. It can increase itīs voltage (during charging) providing a false indication of "health" and not be able to deliver the required energy (to the bus) if an emergency situation requires it (bus voltage below, i estimate ~ 30 V). A cell that fall below a given threshold very probably will never recover. Lead Acid in this aspect can go to zero, exhibit a high internal resistance and FULLY RECOVER. I faced this situation and after charging (longer time was required) it returned to the same (anti) capability.
In flight the APU Bat will only be used to start the APU if NO OTHER SOURCE IS AVAILABLE.
JAL in BOS probably started the APU using the battery? If so the runaway probably started with hot cells (after high current use starting APU) and when receiving high current (with regime to recharge "fast")
Why would they start the APU using the battery when starting with the engines running and providing power is the normal way to start an APU.Or if on the ground an Aux Power unit would be connected surely.
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APU battery not used in BOS
fergineer:
Sure! i was concentrated thinking on main battery and was supposing APU battery as the only source. Certainly is not.
Thanks for questioning. Must go bed...
Fatigue could explain.
This means both Li Ion (main and APU) on 787 are kept "floating" most of their life.
Why would they start the APU using the battery when starting with the engines running and providing power is the normal way to start an APU.Or if on the ground an Aux Power unit would be connected surely.
Sure! i was concentrated thinking on main battery and was supposing APU battery as the only source. Certainly is not.
Thanks for questioning. Must go bed...
Fatigue could explain.This means both Li Ion (main and APU) on 787 are kept "floating" most of their life.
Last edited by Jetdriver; 30th Jan 2013 at 03:18.
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A previous posting suggested a Lithium Cobalt mix is a Fire Chiefs worst nightmare since a fire is self sustaining as it produces its own O2. So despite the latest news that the Japanese have found no faults with their battery manufacture, should such a battery be on an a/c.?
I ask myself why have Boeing gone with this technology?
My suggestion is because the a/c is all electric then there are ultimate failure situations where high energy is needed. On every a/c I have flown before the brakes for example have a brake accumulator. The brakes on this a/c are electric, so the backup has to be the same. A high energy battery?
I ask myself why have Boeing gone with this technology?
My suggestion is because the a/c is all electric then there are ultimate failure situations where high energy is needed. On every a/c I have flown before the brakes for example have a brake accumulator. The brakes on this a/c are electric, so the backup has to be the same. A high energy battery?