FAA Grounds 787s
Boeing looks for speedy approval after 787 battery tests | Business & Technology | The Seattle Times
Boeing's Hinderberger is reported in the Seattle Times to say that the fire in Boston consisted of only "small flames" outside the blue box.
So, apparently there is no need to worry.
Hinderberger reiterated the assertions of top Boeing executives a day earlier that played down the two events that led to the grounding: the battery fire in a 787 parked on the ground in Boston and the smoldering of a battery on a 787 flight in Japan.
He said that the fire in Boston consisted of small flames outside the blue battery box, but that “there was not a fire inside the blue box.”
He said that the fire in Boston consisted of small flames outside the blue battery box, but that “there was not a fire inside the blue box.”
So, apparently there is no need to worry.
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Surely the batteries are on board for a purpose,? if they have melted or discharged then that function is not met. I can envisage lots of downroute delays/problems even if a future failure/fire is contained? Lots of airlines could be unhappy?
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ITman:
I had a problem with that too, until I looked very hard at the description and realized that what he was referring to was stopping the discharge at a higher voltage/State Of Charge level rather than discharging more deeply.
Similarly on the high end, the are stopping charging sooner.
Together they will avoid larger parts of the battery operation area at either end that are most associated with both inefficiency and stress on the battery.
As a result the nominal energy capacity of the battery will be lower, but the available current will not be affected.
Oh, one other point while I am on the subject: When the aft battery is called on to deliver power, without the APU or other power available, does it also supply power to the charger and FDR so that conditions of discharge are recorded? Since they have had to replace so many batteries for over-discharge, that seems like relevant data.
I like the report in Flight Global especially the first paragraph...., this makes the whole thing very worrying.. Also noted that they are going for a higher discharge level that is a guarantee for battery heating and potential failure IMO.
Similarly on the high end, the are stopping charging sooner.
Together they will avoid larger parts of the battery operation area at either end that are most associated with both inefficiency and stress on the battery.
As a result the nominal energy capacity of the battery will be lower, but the available current will not be affected.
Oh, one other point while I am on the subject: When the aft battery is called on to deliver power, without the APU or other power available, does it also supply power to the charger and FDR so that conditions of discharge are recorded? Since they have had to replace so many batteries for over-discharge, that seems like relevant data.
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FlexibleResponse:
Why do I keep misreading that as Hindenberger? 
Boeing's Hinderberger is reported in the Seattle Times to say that the fire in Boston consisted of only "small flames" outside the blue box.
So, apparently there is no need to worry.
So, apparently there is no need to worry.
Last edited by inetdog; 16th Mar 2013 at 06:25.
What amazes me is that Boeing admit that they still don't really know what caused the problem and in the same breath, say they've fixed it. Classic cognitive dissonance.
Don't get me wrong - the 787 looks like it will be a fine aircraft and one I'll probably pilot in the not too distant future. They *are* going to have to man up and totally redesign the battery part of it before I get on board, though, even as a passenger.
Don't get me wrong - the 787 looks like it will be a fine aircraft and one I'll probably pilot in the not too distant future. They *are* going to have to man up and totally redesign the battery part of it before I get on board, though, even as a passenger.
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Quote:
In Boeing's view, neither incident met the company's internal definition for the condition called "thermal runaway". That is a situation in which there "is so much energy, so much heat and so much flame that it would put the airplane at risk", Sinnett says. "We know very clearly this was not the case in the Logan event and the Takamatsu event."
Agreed - and how will containing such an event in a metal box help?
In Boeing's view, neither incident met the company's internal definition for the condition called "thermal runaway". That is a situation in which there "is so much energy, so much heat and so much flame that it would put the airplane at risk", Sinnett says. "We know very clearly this was not the case in the Logan event and the Takamatsu event."
Full Wings
That assertion doesn't seem to be backed up by the NTSB initial report. If the firefighters had just stood back and done nothing, odds-on we'd be looking at pile of ashes in the outline of a 787 at BOS. It's very difficult to imagine there not being a serious conflagration with all that energy dumped into a confined space.
The "contained" burn damage occurred *despite* a fire crew arriving extremely promptly and using large amounts of extinguishant over the period of an hour or more. A luxury which is not available in the air, where the aeroplane was shortly beforehand.
This is commercial/political spin of the worst order and I wish Boeing would stop it and get on with fixing the problem(s). IMHO they should fire some of the management and hire some more engineers...
That assertion doesn't seem to be backed up by the NTSB initial report. If the firefighters had just stood back and done nothing, odds-on we'd be looking at pile of ashes in the outline of a 787 at BOS. It's very difficult to imagine there not being a serious conflagration with all that energy dumped into a confined space.
The "contained" burn damage occurred *despite* a fire crew arriving extremely promptly and using large amounts of extinguishant over the period of an hour or more. A luxury which is not available in the air, where the aeroplane was shortly beforehand.
This is commercial/political spin of the worst order and I wish Boeing would stop it and get on with fixing the problem(s). IMHO they should fire some of the management and hire some more engineers...
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Definition of thermal runaway
To an engineer, thermal runaway is when temperature elevation triggers something with the effect of releasing energy, further increasing temperature, leading to a self-sustaining positive feedback bringing the temperature outside of the design range.
In the context of a battery,
- the something that's triggered is liberation of the energy stored in electrochemical form, as heat and/or the release/expansion of gazes (this can contribute to the positive feedback by both mechanical and thermal means);
- thermal runaway can be split into two categories: within a cell, or propagating from a cell to adjacent cells; the NTSB report of the Logan incident suggests both categories of thermal runaway occurred (7 out of 8 cells had short circuited, strongly suggesting they released most of their energy).
Prohibition of thermal runaway in aviation Li-ion batteries has been worded as: "Li-ion batteries must be designed to preclude the occurrence of self-sustaining, uncontrolled increases in temperature or pressure", with no reference to the damage such event might cause.
Restricting thermal runaway to an unwanted release of energy at a level endangering the plane would be wreaking havoc with that engineering definition. I see it as a miserable attempt to deny the failure of Boeing's initial analysis that the battery as a whole was safe from thermal runaway.
In the context of a battery,
- the something that's triggered is liberation of the energy stored in electrochemical form, as heat and/or the release/expansion of gazes (this can contribute to the positive feedback by both mechanical and thermal means);
- thermal runaway can be split into two categories: within a cell, or propagating from a cell to adjacent cells; the NTSB report of the Logan incident suggests both categories of thermal runaway occurred (7 out of 8 cells had short circuited, strongly suggesting they released most of their energy).
Prohibition of thermal runaway in aviation Li-ion batteries has been worded as: "Li-ion batteries must be designed to preclude the occurrence of self-sustaining, uncontrolled increases in temperature or pressure", with no reference to the damage such event might cause.
Restricting thermal runaway to an unwanted release of energy at a level endangering the plane would be wreaking havoc with that engineering definition. I see it as a miserable attempt to deny the failure of Boeing's initial analysis that the battery as a whole was safe from thermal runaway.
They never said they fixed it...
What amazes me is that Boeing admit that they still don't really know what caused the problem and in the same breath, say they've fixed it. Classic cognitive dissonance.
I suspect that all of the engineers who understand Lithium-Ion technology "know" what the cause is, but they cannot PROVE it because the occurrence of the problem vaporises the evidence.
I suspect that everyone believes that the proximal cause was dendrites on the battery electrodes. These can occur spontaneously: the root cause may very well be "choosing Lithium-Ion batteries".
We and everyone else could guess that the dendrites were caused by high charge or discharge amperage. But they can occur simply through cycling the battery. Whatever: by the time thermal runaway occurs, the original dendrites have been vaporised long ago.
OK, so the Boeing 787 becomes the first form of locomotion since steam trains to have a fire-box!
Now we have some questions for the Flight Crew among us.
Whether the batteries in their fire boxes are on fire or not, they are not producing electricity. Just above them are the same type of battery that provides the 10-minute backup of last resort for the flight controls. Those batteries are apparently not getting fireboxes.
So: If you were in Sully's position -- both donks failed and APU not running -- are you safe enough? Can you get us back on the ground undamaged?
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So: If you were in Sully's position -- both donks failed and APU not running -- are you safe enough? Can you get us back on the ground undamaged?
The realms of probability are getting so remote by now that I am more worried about being taken down by an asteroid strike.
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So: If you were in Sully's position -- both donks failed and APU not running -- are you safe enough? Can you get us back on the ground?
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Here's what I don't understand. I have read that the 787 batteries had been failing non-catastrophically at some enormous rate prior to the catastrophic failures. I have not seen a single word about the failure analysis of these batteries. What's up with that? Surely A) Boeing must have been concerned that there was a deeper problem as soon as 4-5 batteries had to be swapped out and B) There must have been some clue as to what was going wrong and that the possibility of a catastrophic failure was probably much greater than originally predicted.
I'm an electrical engineer and small businessman in addition to being a private pilot. I design, build and sell electronic equipment that costs anywhere from USD 80 to USD 600. I can absolutely assure you that if my customers have more than one identical failure of my product, they let me know in no uncertain terms that the situation is unacceptable. And for the record, I agree and I get to the root of the problem. It's hard for me to fathom how Boeing could not take the same approach on a $150,000,000 aircraft.
I'm an electrical engineer and small businessman in addition to being a private pilot. I design, build and sell electronic equipment that costs anywhere from USD 80 to USD 600. I can absolutely assure you that if my customers have more than one identical failure of my product, they let me know in no uncertain terms that the situation is unacceptable. And for the record, I agree and I get to the root of the problem. It's hard for me to fathom how Boeing could not take the same approach on a $150,000,000 aircraft.
Last edited by grumpyoldgeek; 16th Mar 2013 at 17:38.
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@grumpyoldgeek
In the majority of cases, the cause was ground crew operating the aircraft solely off battery power for periods longer than Boeing specified. This drained the batteries to a level where the safety systems in the BMU and BCS disconnected the battery to prevent continued discharging.
Once the battery was drained to this state, it could no longer be charged on the airplane using the airplane's charging systems. Instead, the battery had to be returned to Yuasa for recharging and refurbishment. As to why this was the case, I have not seen a definitive explanation. Perhaps because the airplane's battery system could not fully recharge the battery quickly enough. Perhaps Yuasa felt such a deep discharge required the battery cells be examined and replaced, if necessary.
One of the changes Boeing is making is raising that discharge cutoff limit. I would expect the limit will be raised to a point where the onboard charging system can fully recharge it in whatever time period is deemed necessary and therefore the battery will no longer need to be removed.
Here's what I don't understand. I have read that the 787 batteries had been failing non-catastrophically at some enormous rate prior to the catastrophic failures. I have not seen a single word about the failure analysis of these batteries. What's up with that? Surely A) Boeing must have been concerned that there was a deeper problem as soon as 4-5 batteries had to be swapped out and B) There must have been some clue as to what was going wrong and that the possibility of a catastrophic failure was probably much greater than originally predicted.
Once the battery was drained to this state, it could no longer be charged on the airplane using the airplane's charging systems. Instead, the battery had to be returned to Yuasa for recharging and refurbishment. As to why this was the case, I have not seen a definitive explanation. Perhaps because the airplane's battery system could not fully recharge the battery quickly enough. Perhaps Yuasa felt such a deep discharge required the battery cells be examined and replaced, if necessary.
One of the changes Boeing is making is raising that discharge cutoff limit. I would expect the limit will be raised to a point where the onboard charging system can fully recharge it in whatever time period is deemed necessary and therefore the battery will no longer need to be removed.
Last edited by Kiskaloo; 16th Mar 2013 at 19:18.
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In the industry that I work in, if we have a failure of unknown cause, when we get to a solution, we would have two test rigs setup. One with the modification, and one to the previous standard.
If under duplicate testing neither fails, we do not have a fix. We would have to ensure the old design fails, and the new design runs as required.
I hope Boeing is confident with the testing, and solution.
If under duplicate testing neither fails, we do not have a fix. We would have to ensure the old design fails, and the new design runs as required.
I hope Boeing is confident with the testing, and solution.
Last edited by Helix Von Smelix; 16th Mar 2013 at 20:11.
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@Helix Von Smelix
Once the NTSB and JTSB have identified the root causes of the battery failures aboard JL8 and NH692 I fully expect we will see new Airworthiness Directives issued to specifically address them.
In the industry that I work in, if we have a failure of unknown cause, when we get to a solution, we would have two test rigs setup. One with the modification, and one to the previous standard.
If under duplicate testing neither fails, we do not have a fix. We would have to ensure the old design fails, and the new design runs as required.
I hope Boeing is confident with the testing, and solution.
If under duplicate testing neither fails, we do not have a fix. We would have to ensure the old design fails, and the new design runs as required.
I hope Boeing is confident with the testing, and solution.
Last edited by Kiskaloo; 16th Mar 2013 at 20:43.
Once the NTSB and JTSB have identified the root causes of the battery failures aboard JL8 and NH692 I fully expect we will see new Airworthiness Directives issued to specifically address them.
The failure by itself may not be critical to safe flight
Recertification will be even more challenging than procedure outlined by Helix Von Smelix #1312 because the standard is statistical risk, not absolute. NTSB quantified the risk requirement; “Boeing .....determined that the likelihood of a smoke emission event from a 787 battery would occur less than once in every 10 million flight hours”. In real life “there have been two critical battery events on the 787 fleet with fewer than 100,000 flight hours”. In fact fleet hours were only 52,000 so Boeing must substantiate to a critical audience that improvements to the battery system yield at least a 200 fold reduction in risk of failure.
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Boeing Battery deemed to set fire again
it is quite amazing. Boeing , by designing a firebox to enclose the battery is only telling us that the battery will definitely ignite again, but we must be satisfied with a fire box and an exhaust pipe. why the need of testing since the fire will eventually be under control. what is the main reason to undergo a test without adressing the root cause of the failure, which, by the way is unknown.
1 minor changes in the battery= approximately no change in design
2 retrofit a firebox and vent pipe= we expect igntion after modification
Why NTSB should give a credit to this...I doubt
1 minor changes in the battery= approximately no change in design
2 retrofit a firebox and vent pipe= we expect igntion after modification
Why NTSB should give a credit to this...I doubt
Last edited by avogadro; 16th Mar 2013 at 23:16.