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Paxboy:
I'm not suggesting Boeing haven't screwed up on the strategic issues such as system integration - which is why I think that's where the answers should be looked for. But when it comes to the individual components and subsystems, I'm confident that all concerned did a good job and met all the specs they were given - which is basically what the NTSB have confirmed. |
The problem with aviation kit is that it's become more about the process
than the end result. The "Medium is the Message", as McLuhan used to say. Yes, it does meet the spec down to the last detail, but the battery system is wrong by design in so many ways, as has been demonstrated by the discussion over in tech log. The fact that this was never integration tested as a complete subsystem beggars belief. In industry, rapid developmnent techniques get product to market fast, often with little or no process, using cheap components and yet most of it works most of the time. Aviation throws millions of $ at the problem and ends up with designs that sometimes look completely irrational and clueless. Why is this ?. Crowdsourcing works, and some are qualified to comment on this half baked design, even with the limited info available... |
Size matters
A 50 pound child's sparkler would make an impressive sparkle.
Some, but not Boeing, might even call it a fire. |
Someone at Boeing thinks the same of this "solution" as I do
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What prevents Boeing from switching to NiCad-batteries? Their 777 has them "ready". |
Stripping back all of the recent PR releases etc, isolating the 'visible' effect of all of this by placing the battery (which as far as we know at this time is the only problem?), inside stronger physical containment is not a solution by definition. As many on here have already speculated on the possible causes, the underlying fault as such is still there.
I would hope that other works are also taking place in the background i.e. modified circuit designs, updated software, operating proceedures etc to address this. However, I suppose the crux of this debate is to establish if these batteries are really a critical part of the systems or not, and can sustain failure without causing any further problems with the AC ? If it proved that it doesn't, then perhaps the 'box' may suffice for now, but if goes the other way and it is proved they are critical, then it surely has to be a non-starter. Excuse the pun :} I see this phase as basically sticking a bigger fuse in to see what happens next. If you don't know why the fuse blew in the first place and keep changing them for larger fuses how do you then know whats really going wrong until there is a larger failure? Perhaps extended tests once it is back flying (with no PAX I hope), with a little more attention focused into this area may eventually find an engineered solution. :ok: |
I was waiting until a little more information was available about Boeing's proposed approach.....
Now it is obvious:
Also, in view of Boeings apparent belief that PR is more important than good engineering, if there is a choice will be following the credo "If it's Boeing I ain't going" when chosing who to fly with (why take the risk?). I'll make an exception for the older, well proven models - but am starting to worry the same approach has been used for all the newer offerings. I will be recommending the same approach to friends and family. I have a degree in Electrical Engineering - so hope I have a reasonable understanding of the issues. |
@OpenCirrus619: do not underestimate Boeing
Don't be so sure Boeing has not identified the cause, or at least some likely cause(s).
I think they have clues, but prefer not to tell, partly because they are not quite sure it is cell damage by deep discharge, water condensation leading to damage by electrolysis, internal cell short by some foreign material, or something else; partly because that would make more painfully apparent that the reasoning in the original certification was bogus, and passengers at (some, likely moderate) risk in previous flights. So they take steps to mitigate the consequences of a thermal-runaway(-at-the-cell-or-battery-level as they call it), with this (not-a-)fire box, and frankly I think it is a sound safety measure given that they keep the same chemistry (perhaps, because of the peak power and relatively high voltage needed). And they take measures to operate the cells in a reduced voltage range, to less stress them. And they implement some (untold) improvement in the cell construction or/and screening. And use better fasteners, just in case. I only wish we had more details on the identified possible root cause(s) and how the measures resolve them. I do not despair that it will come. |
Quote: What prevents Boeing from switching to NiCad-batteries? Their 777 has them "ready".Because of the size of the starter/generator units fitted to the APU, a NiCad cannot produce sufficient current, no matter how big it is. The amperemeter is showing up to 1000 amps... |
The A350 does use a strong 1,268 kW Honeywell APU that seems to be working with NiCad batteries.
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Cartridge Starter?
Because of the size of the starter/generator units fitted to the APU, a NiCad cannot produce sufficient current, no matter how big it is. |
What prevents Boeing from switching to NiCad-batteries? Their 777 has them "ready". Because of the size of the starter/generator units fitted to the APU, a NiCad cannot produce sufficient current, no matter how big it is. My understanding is the main battery is required to have enough power to operate the emergency brakes in the event of an emergency landing with no other source of electrical power other than a rapidly slowing RAT. The APU battery is the same type for the sake of commonality of LRUs. IE. You are carrying a spare to get you home in the unlikely event the main one fails away from base. :O:oh: |
I fear that EEng #1368 and poorjohn #1369 are right. Boeing will contend that cell temperature (>570 deg F) and pressure (enough to rupture cell) which were clearly unsafe at Boston are “safe” in box at 30,000 feet 5 ½ hours from land. Boeing may have a “battery” of lawyers prove compliance with SCCs but won’t win in the court of public opinion.
Delve behind the actual SCCs in Federal Register, Volume 72 Issue 196 (Thursday, October 11, 2007) and ALPA seemed concerned from the outset that Boeing might push a “safe containment” strategy but was reassured that FAA would not allow it. Long ago Boeing relied on its own idea of “safe” to meet fail-safe requirements for 737 fuselage; and it ended badly. Boeing claimed that if the fuselage fatigued, a single "lead crack" would grow along the skin until it reached a fuselage frame, then turn at right angles and a triangular shaped tear would blow out and safely dump fuselage pressure. British and Australian authorities never accepted the concept and a long war of words culminated in Boeing’s glib assurance in letter dated 14 April 1988 that it had "demonstrated safe decompression in lap joints …..". Two weeks later precisely this failure ripped the roof off Aloha Airlines Flight 243. Flight attendant Clarabelle Lansing died and 89 passengers feared they would. Read full story at LESSONS FROM ALOHA and sorry for digression. |
The amperemeter is showing up to 1000 amps... An engineer friend who has worked on the 787 in Seattle told me that the ability to provide a high current was the main reason for using these batteries. There is a hint in this graphic from Boeing: Batteries and Advanced Airplanes - Boeing 787 Updates .... in the unlikely event the main one fails away from base :ok: |
As posted elsewhere, a Li-Ion battery kicking off. MoD trials, 1991. This is a normal battery for a manpack radio.
No-one mentions MoD's total recall and destruction order for BOWMAN HF radio Li-Ion secondaries (2006). Not repair, re-work or modification, but total destruction. http://i214.photobucket.com/albums/c...ps56d3e9e5.jpg |
Following the matters with great interest I am wondering if Boeing is planning to apply the firebox fix to both batteries as it seems so far only the centre EE bay will be modified.
I understand both are interchangable and before they can trace the root cause for all three incidents, which, admitely happened all with the centre battery, I am not very convinced of the safety guarantees they are clayming. |
I understand both are interchangable and before they can trace the root cause for all three incidents, which, admitely happened all with the centre battery, Not sure what third incident you are talking about. :confused: |
There are several articles in the public press saying that Boeing will conduct two test flights approximately this weekend, and that the new system will be / has been subjected to the 2008 RTCA standards. One article NewsDaily: Boeing puts 787 battery to tough tests it once avoided includes some comment about how difficult it will be / was to pass the test with LiCo:
Lukso, who left SecuraPlane to start his own lithium-ion battery business, acknowledged that the RTCA standards are tough. At his new company, he spent $6 million and several years without successfully building a battery that could pass the test now in front of Boeing. Another battery maker, EaglePicher Technologies, of Joplin, Missouri, passed tests modeled on DO-311, but used a less volatile chemistry than Boeing, known as lithium-iron phosphate. "To successfully pass the containment (test), we needed iron phosphate," Ron Nowlin, general manager of aerospace systems for EaglePicher, said in an interview earlier this year. |
Because of the size of the starter/generator units fitted to the APU, a NiCad cannot produce sufficient current, no matter how big it is. current -demand can be met ,simply by having lots more smaller cells. Why do you think the present lithium configuration has 3 sub-cells in parallell.? much easier to make one big one, but the path across the plates to the terminal-post will be far longer. The advantage of lithium technology is 3-fold 1- shape of cell is not as constrained as is the case with others. 2 higher energy-density. (stores more power in the same space) 3 higher discharge/charge current-capability. The downaide is the need to very carefully monitor and control EVERY cell's operation. this is still not being done monitoring batches of 3 is where I think they came unstuck and history will repeat until they treat the technology with due caution. a bigger,stronger firebox is just a big lashup kludge. IMHO, the software in the battery controller should automatically start the APU before the point at which doing-so would over-discharge the battery (IE when about 1/3 of the USABLE capacity has been drawn) this would go some way to ensuring that batteries remained serviceable, charged and rechargeable and met their primary function as reserve supply for ETOPS operation. thus , delays due to batteries not meeting despatch criteria, would be virtually eliminated. A big tin box with a sewage-drain is not going to achieve that! |
Ruffled Feathers!
http://dms.ntsb.gov/pubdms/search/document.cfm?docID=389173&docketID=54251&mkey=85973 :
March 21, 2013 Brett C. Gerry, Esq. Vice President and Assistant General Counsel for Commercial Airplanes The Boeing Company Post Office Box 3707, MC-22-83 Seattle, WA 98124-2207 Dear Mr. Gerry: I am writing to remind The Boeing Company (Boeing) of its obligations as a party to a National Transportation Safety Board (NTSB) investigation. Since the Japan Airlines Boeing 787-8 auxiliary power unit battery fire event at Boston Logan International Airport on January 7, 2013, the NTSB has received technical assistance and cooperation from Boeing as a party to our ongoing investigation. Boeing is also serving as a technical advisor to the NTSB in our role as the accredited representative to the Japan Tran sport Safety Board (JTSB) in its investigation of the battery event that occurred on All Nippon Airways Flight 692 on January 16, 2013. Our Office of Aviation Safety has worked close ly with Boeing throughout the Japan Airlines investigation and our Office of Communications has worked effectively with Boeing regarding the dissemination of information to the media. Boeing is obviously familiar with the NTSB investigative process and its failure to inform the NTSB of the content of the recent technical briefing in Tokyo prior to its occurrence is inconsistent with our expectations for a party. As you know, the role and responsibilities of a party to an NTSB investigation are set forth in the NTSB ' s Certification of Party Representative, agency regulations, and accompanying information and guidance. The Boeing party representative signed this certification on January 7, 2013. The NTSB expects parties to an investigation to comply fully with its requirements and respect the role of the agency in performing its investigative responsibilities independently and with transparency. As a party to our investigation, Boeing's support of and participation in the upcoming NTSB hearing beginning on April 23, 2013, are appreciated. If you or your staff have any questions or concerns about the party agreement or your participation in our upcoming hearing, please do not hesitate to call me. Sincerely, David K. Tochen General Counsel |
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