FAA Grounds 787s
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Guys, this is supposed to be a professional pilot's forum. If you are going to express yourselves in the sensationalist manner of the (British) gutter press, then you are doing the forum an injustice.
Well a 3 mm steel box is pretty strong -- and heavy
Presuming the melting point is above what a runaway battery will produce, the box will also keep oxygen from supporting combustion.
The next question is what will happen to surrounding components and structure from the high temperature?
Hopefully maintenance will be able to disconnect the entire box and take it to the bench to extract the battery.
Presuming the melting point is above what a runaway battery will produce, the box will also keep oxygen from supporting combustion.
The next question is what will happen to surrounding components and structure from the high temperature?
Hopefully maintenance will be able to disconnect the entire box and take it to the bench to extract the battery.
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RatherBeFlying
I thought the problem centres around the fact that lithium batteries produce their own oxygen? In which case any potential fire would not necessarily extinguish inside a container, no matter how airtight.
Ut Sementem Feeceris
The next question is what will happen to surrounding components and structure from the high temperature?
I too cannot see what this test flight can possibly hope to achieve - unless they replicate a runaway event to ensure that venting takes place as per design. If they just fly it and say "look - it didn't burn" that's not going to get me anywhere near a 787 anytime soon.
This whole thing is being driven by PR. I bet 95% of the public probably have absolutely no idea of the events surrounding the grounding, the "fix" or the implications of a battery fire on board. The customer airlines are caught between a rock and and a hard place - they, in private, may be extremely unhappy with the "solution" but have to put on a public face of "business as usual" and we are fully confident in our product as they have already lost millions and the implications going forward are many times that.
If a 787 subsequently has a serious event after this fix is released.......
Last edited by A4; 25th Mar 2013 at 08:50.
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Cells redesigned, or NOT?
Blacksheep wrote:
However Boeing is quoted as:
that's here
787 Ferry Flights To Resume
If there is a plan to recycle some of the cells returning from the fleet, then there is no redesign of the cells, and only the screening is modified. Seems the most likely, because there was not enough time for a cell redesign and qualification of that.
The battery is being so heavily modified it isn't the same battery any longer:
1. Improved cell manufacturing process
1. Improved cell manufacturing process
"For every battery in service we have a manufacturing record, so we know how each one of the cells behaved when they were tested. We know today which cells will not pass the screening tests and when they return from the fleet we will reject those cells."
787 Ferry Flights To Resume
If there is a plan to recycle some of the cells returning from the fleet, then there is no redesign of the cells, and only the screening is modified. Seems the most likely, because there was not enough time for a cell redesign and qualification of that.
Last edited by fgrieu; 25th Mar 2013 at 10:43.
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@FASRP...you are well off the ball....
try:- 250 people spent , collectively, 50,000 hours , two at a time, in any one of fifty rooms.
150 of them died during their occupancy
That'sthe scenario at "grounding"
Total in-service fleet=50 each containing 2 "serviceable" batteries.
"dead" batteries replaced:- 150
Total hours flown, 50,000 divide total stock into hours flown and you get an average service-life of 200 hours
@ Seth Welcome !...As you'll see, this lot don't take prisoners!
but a great place for an intellectually stimulating debate.
I' m presuming you meant "Hindenberg "? the infamous Hydrogen-filled Airship.
@ Blacksheep. Totally concur with your remarks , re the firebox.
It's a total victorian-engineering , heath-Robinson lash-up.
52 bolts????WTF -it's supposed to vent at ~ 6000 feet cabin-altitude.
The plate-box already has a lip flange....make the sides and back much bigger and fold back on themselves(upwards)....you now have a slot/runner turn a lip down on the front of the lid. When slid home, the lid and case are securely clamped on all 4 sides...a bolt through the 3 thicknesses,say every 3 inches , would stop any bowing and be mainly in shear.. 12 should do all 4 sides.
Re-ceramics....-been saying this for a long time IMHO each individual sub-cell should be fully thermally insulated and fully monitored for charge-discharge.
These people appear to be attacking the problem from the wrong end!
Preventing an out -of -service battery is a much better "fix" than containing the thermal runaway when one does go TU.... No doubt some of the real Boffins on here can accurately calculate just how much heat-energy is disemitted by 32V 70 Ah discharging in an uncontrolled thermal "event".
try:- 250 people spent , collectively, 50,000 hours , two at a time, in any one of fifty rooms.
150 of them died during their occupancy
That'sthe scenario at "grounding"
Total in-service fleet=50 each containing 2 "serviceable" batteries.
"dead" batteries replaced:- 150
Total hours flown, 50,000 divide total stock into hours flown and you get an average service-life of 200 hours
@ Seth Welcome !...As you'll see, this lot don't take prisoners!
but a great place for an intellectually stimulating debate.I' m presuming you meant "Hindenberg "? the infamous Hydrogen-filled Airship.
@ Blacksheep. Totally concur with your remarks , re the firebox.
It's a total victorian-engineering , heath-Robinson lash-up.
52 bolts????WTF -it's supposed to vent at ~ 6000 feet cabin-altitude.
The plate-box already has a lip flange....make the sides and back much bigger and fold back on themselves(upwards)....you now have a slot/runner turn a lip down on the front of the lid. When slid home, the lid and case are securely clamped on all 4 sides...a bolt through the 3 thicknesses,say every 3 inches , would stop any bowing and be mainly in shear.. 12 should do all 4 sides.
Re-ceramics....-been saying this for a long time IMHO each individual sub-cell should be fully thermally insulated and fully monitored for charge-discharge.
These people appear to be attacking the problem from the wrong end!
Preventing an out -of -service battery is a much better "fix" than containing the thermal runaway when one does go TU.... No doubt some of the real Boffins on here can accurately calculate just how much heat-energy is disemitted by 32V 70 Ah discharging in an uncontrolled thermal "event".
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787 Battery Tests
This extract from a Boeing video shows a severe test of the proposed 787 battery containment enclosure. Propane gas ignited inside the box explodes. The 1/8th-inch thick steel walls bulge out but hold fast.
This extract from a Boeing video shows a severe test of the proposed 787 battery containment enclosure. Propane gas ignited inside the box explodes. The 1/8th-inch thick steel walls bulge out but hold fast.
Seriously, which percentage of the energy stored in a fully charged battery has been released in this test? My rough estimation is about 2% (Propane having 28.2 kWH/m³, Battery having 75Ah at 29.6V with a size of 15x11x9 in... according to NTSB)
"Over a hundred people have died in less than 100 years, which gives a 1:100 years failure rate. In the first 10 years of life that is a 1:10 chance of dying."
Statistical fugures do only work, if you look at a large enough population/timeframe. So the estimation over 500 aircraft and one year was probably much more realistic than a chance of death during a fraction of the MTBF...
Last edited by Volume; 25th Mar 2013 at 13:25.
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Underwriters' viewpoint ?
Whatever we may think of the firebox, the Proof of the Pudding is in the eating, they say : three testgroups will be called upon to feel the taste of this Boeing battery pudding : (1) Underwriters, who'll quote revised or unchanged fees for the insurance of the modified 787s ?; and (2) travellers, who'll fly or not with 787s ? 
The first group are professional statisticians, they will trim their new quotations to the tune of the firebox' anticipated probabilistic impact upon the overall safety of the 787 and its systems, thoroughly re-assessed. In the background, you have the considered opinion of Lloyd's re-insurance experts. Those people - a special class of 'no-nonsense' bargainers - will tell us whether Boeing were right or wrong ?
A third group of pudding-tasters : 787 flight and cabin crew ?
The first group are professional statisticians, they will trim their new quotations to the tune of the firebox' anticipated probabilistic impact upon the overall safety of the 787 and its systems, thoroughly re-assessed. In the background, you have the considered opinion of Lloyd's re-insurance experts. Those people - a special class of 'no-nonsense' bargainers - will tell us whether Boeing were right or wrong ?
A third group of pudding-tasters : 787 flight and cabin crew ?
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cockney...the bolts would be in tension, not shear...
given that about 150 batteries have been replaced, and the issues, dont you think routine inspection would be in order? So those 52 bolts times 2 boxes..
The test noted that moisture buildup inside the existing box may have been a cause of the short....what is to prevent that in this box?
What about the other Li battery, the backup for the avionics?
I see that most of the news regarding test flights beginning this week is now gone....perhaps the NTSB warning from their lead counsel to Boeing had something to do with that..
given that about 150 batteries have been replaced, and the issues, dont you think routine inspection would be in order? So those 52 bolts times 2 boxes..
The test noted that moisture buildup inside the existing box may have been a cause of the short....what is to prevent that in this box?
What about the other Li battery, the backup for the avionics?
I see that most of the news regarding test flights beginning this week is now gone....perhaps the NTSB warning from their lead counsel to Boeing had something to do with that..
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thank for the welcome cockney steve 
Helderberg was the name of the South African 747 that burnt to a crisp mid air and fell into the sea off Mauritius in the 80's killing everyone
South African Airways Flight 295 - Wikipedia, the free encyclopedia
Helderberg was the name of the South African 747 that burnt to a crisp mid air and fell into the sea off Mauritius in the 80's killing everyone
South African Airways Flight 295 - Wikipedia, the free encyclopedia
The other thing about statistics and mtbf is that the figure is not time to next failure.
That is, the mtbf may be calculated as 1 in 10 e6 hours, but that single failure could
happen today, tomorrow, or next week.
As for condensation causing failure, just more red herring bs. Condensation is pretty
much distllled water, which is an insulator. Even with minor impurities, irrelevant
compared to battery charge / discharge currents......
That is, the mtbf may be calculated as 1 in 10 e6 hours, but that single failure could
happen today, tomorrow, or next week.
As for condensation causing failure, just more red herring bs. Condensation is pretty
much distllled water, which is an insulator. Even with minor impurities, irrelevant
compared to battery charge / discharge currents......
Last edited by syseng68k; 25th Mar 2013 at 16:31.
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Blacksheep: Will the public be reassured by a modification that includes putting a part of the aircraft into an explosion proof container, or will they assume that an unacceptable risk of serious failure remains?
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Engines started for the first flight in a while...
Boeing #272 Flight Tracker
It's LN86, a LOT example.
Boeing sets up for 787 battery flight test
Boeing #272 Flight Tracker
It's LN86, a LOT example.
Boeing is on the verge of flight testing the modified 787 battery system changes on Line Number 86, an aircraft destined for LOT Polish Airlines. The aircraft is set to undergo a final pre-flight ground test in the afternoon (Pacific time), at Paine Field, Everett on 24th, and if all goes to plan could be cleared for a standard ‘B2’ profile, customer acceptance type flight test on March 25.
Last edited by StoneyBridge Radar; 25th Mar 2013 at 18:25.
That is mathematical nonsense. Let me just replace your numbers with people and it's easy to see how crazy that statement is.
Last edited by peter we; 25th Mar 2013 at 19:05.
Anyone have the details of the box and ventilation design handy?
Will this box be sealed during normal operations? Or will there be positive ventilation overboard through an outflow port?
Will this box be sealed during normal operations? Or will there be positive ventilation overboard through an outflow port?
Hmm
Boeing #272 Flight Tracker
At the moment, it appears to be heading out over water instead of close to the coast.
I hope there's nothing they need to douse.
At the moment, it appears to be heading out over water instead of close to the coast.
I hope there's nothing they need to douse.
I suspect the propane test was to simulate gasses from a thermal runaway mixing with the air in the box and igniting. I haven't heard of a scenario in which the battery's potential energy could be released instantaneously. Were that possible (which I doubt) I suspect the result would be rather grim.
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A question crossing my mind after watching the propane video : Just imagine the lid of the box ( or the whole box) does not really hold in case of a thermal. runaway. Could the explosion , and the velocity of the steel parts flying around in this confined Electric bay area cause more dramatic destruction than a fire ?
I understand Halon 1301 is an oxygen depletive, so I do not understand why a massive Halon discharge in A CLOSE area in case of a Li-ion fire would not work ? Different story in an open area of course. but inside a box ?
I understand Halon 1301 is an oxygen depletive, so I do not understand why a massive Halon discharge in A CLOSE area in case of a Li-ion fire would not work ? Different story in an open area of course. but inside a box ?