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#201
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Is the 787 a failure ?
On Fri, 22 Mar 2013 16:57:55 -0000, "Keith W"
wrote: GunnerAsch wrote: On Fri, 22 Mar 2013 12:40:50 -0000, "Keith W" wrote: GunnerAsch wrote: On Fri, 22 Mar 2013 09:23:17 -0000, "Keith W" wrote: The conventional Batteries are sometimes called Sealed Lead Acid Batteries but they are actually AGM batteries. Modern passenger aircraft normally use Nickel Cadmium batteries Why havent they converted over to NmH? They have a relatively high self discharge rate and can lose up to 20% of the energy stored in the first 24 hours. This is acceptable for hybrid vehicles where the battery is primarily a temporary buffer to capture the energy from regenerative braking but not good for a system intended to initiate an aircraft startup sequence after a week in the hangar. Keith Thats not true anymore. Since Sanyo developed the Enerloop NiMH battery..they are being shipped charged from the factories. All the makers are using the new tech and have been doing so for at least 3 yrs. Ive got NiMH batteries that I only need to put on the charger ever 6 months, just to top them off. Gunner Trouble is they are not available in the size or capacity to be used in an electric vehicle, last time I checked the largest was a D size. Keith D batteries are what they use in some of the electric vehicles as I recall. Some 300 of them Or was it 3000? Gunner |
#202
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Is the 787 a failure ?
"Keith W" wrote in message
news Jim Wilkins wrote: At 2h 12m ~15s the Pilot Flying made a pitch-down input that brought their forward speed above the stall warning's lower limit of 60 Kts and it sounded again, confusing them. Page 44 of the final report: " If the CAS measurements for the three ADR are lower than 60 kt, the angle of attack values of the three ADR are invalid and the stall warning is then inoperative." My real point is to remind Bill Black that he lives in a glass house and shouldn't throw stones at Boeing. jsw The real point is that the aircraft clearly 1) Indicated that it had reverted to direct law (manual input) 2) Sounded the stall warning 3) Showed that the aircraft was falling at a high angle of attack and low speed The pilot flying seems to have been fixated on keeping the wings level and disregarded the angle of attack which at 2 minutes 12 seconds was 40 degrees ! During the entire crisis it was never less than 35 degrees. Keith "When the calculation of the Vsw speed is not available, this speed is no longer displayed on the PFDs. No visual information is then displayed that is specific to the approach to stall." "The angle of attack is the parameter that allows the stall warning to be triggered. Its value is not directly displayed to the pilots." They knew their small nose-up angle, but not the large relative wind direction component of AoA. Speculation based on similar non-fatal incidents: "The reappearance of the flight directors on the PFD when two airspeeds are calculated as similar may prompt the crew to promptly engage an autopilot. However, although the magnitude of these speeds may be the same, they may be erroneous and low, and could cause the autopilot to command flight control surface movements that are incompatible with the aircraft's actual speed. They dance around the possibility that the Flight Director crossbars on the Primary Flight Display might have misled the crew. The PFD is on page 39. The reconstructon of information available to the crew begins on p.93. jsw |
#203
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Is the 787 a failure ?
"Jim Wilkins" wrote in message
... "The angle of attack is the parameter that allows the stall warning to be triggered. Its value is not directly displayed to the pilots." They knew their small nose-up angle, but not the large relative wind direction component of AoA. jsw If that's unclear, they were pitched up 5 degrees and descending at 35 degrees for a combined AoA of 40 degrees. jsw |
#204
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Is the 787 a failure ?
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#205
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Is the 787 a failure ?
On Fri, 22 Mar 2013 09:22:49 -0400, "Jim Wilkins"
wrote: "Daryl" wrote in message ... ...I have never had a case break open on an AGM. Daryl Then you haven't looked very hard. http://nissandiesel.dyndns.org/viewt...60ab1 12d039d "Problem: APC UPSs sometimes have a float charge voltage that is too high and tends to cook batteries. Here's a pair of gel/AGM batteries from a SUA1000 (not an XL) that have swollen so badly that I had to disassemble the case and pry the batteries out of the metal cage: " VERY common problem on "A Piece of Crap" UPS systems (as well as some cheaper ones) but when they split they don't leak. |
#206
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Is the 787 a failure ?
On Fri, 22 Mar 2013 08:05:23 -0600, Daryl
wrote: On 3/22/2013 6:09 AM, Keith W wrote: Daryl wrote: On 3/22/2013 3:23 AM, Keith W wrote: Daryl wrote: On 3/22/2013 12:55 AM, Mr. B1ack wrote: On Fri, 22 Mar 2013 03:00:07 +0000 (UTC), (Bradley K. Sherman) wrote: Who are you gonna believe, Boeing or your own lying eyes? Boeing Co. (BA)'s assertion that U.S. investigators ruled out a fire within the battery case of a Japan Airlines Co. (9201) 787 is premature, a National Transportation Safety Board spokesman said. Investigators examining the Jan. 7 fire aboard the Dreamliner in Boston haven't ruled out that flames erupted within the lithium-ion battery container, Peter Knudson said today in response to questions about the issue. ... Michael Sinnett, Boeing's chief project engineer, said in the briefing that investigators hadn't found evidence of flames within the Boston battery's container box, an indication it worked as designed to limit damage from a battery failure. A witness who tried to fight the Jan. 7 fire said he saw 3- inch (7.6-centimeter) flames outside the lithium-ion battery, and the NTSB has found evidence of high temperatures within battery cells that failed, according to preliminary safety-board documents released March 7. ... http://www.businessweek.com/news/2013-03-15/ntsb-contradicts-boeing-claim-of-no-fire-in-787-battery --bks Gawd ... is THIS thread still going on ???????????/ Yes, the 787 is a failure. Put it this way ... after hearing about its problems *I* will NEVER fly on one - ever. And I'm hardly the only one who feels this way. Not interested in burning to death over the Pacific .... The conventional Batteries are sometimes called Sealed Lead Acid Batteries but they are actually AGM batteries. Modern passenger aircraft normally use Nickel Cadmium batteries Which are prone to a lot of problems. And it's old tech. Now for the real negatives. If you overcharge them, they overheat. If you let them go down below 20% they will need to be taken out and charged very, very slowly with a special charger. They are very susceptible to temperature ranges. They are the heaviest of the Non Lead Acid batteries, their life span is almost equal to the sealed lead acid if you don't count the fact they damage easy. The cost is more than the AGM. The AGM is just now finding it's way into the aircraft industry. Of course, it has been somewhat over looked because of the Lithiums. But it appears that small aircraft that are worried about initial building costs are not overlooking them. What they are looking at is the replacement hours on the Lithiums. They start out at 800 charges and go to 2000 charges depending on the type of Lithium. The weights in comparison to the AGM is anywhere 3 times to 5 times lighter. But the cost is at least 5 times the cost. Less time between replacements, requires a heated and cooled area but is the most dependable. If that is all that is keeping the 787 from flying, it's a pretty simple fix. Not necessarily as that may need recertification which is a complex and lengthy since the batteries would be heavier and take up more space. They are going to have to be re certified anyway. The AGM isn't that much larger and it's pretty well proven in the Electric Vehicles to day. Most electrical vehicles do not use AGM's, their energy density is too low as is their charge rate examples Toyota Prius - NiMH batteries Nissan Leaf - Lithium ion batteries Chevvy Volt - Lithium ion batteries Tesla - Lithium ion batteries Fisker - Lithium ion batteries VW Electric - Lithium ion batteries Renault - Lithium ion batteries Battery energy density MJ per kilogram Lithium-ion battery 0.720 Alkaline battery 0.671 Nickel-metal 0.28 Lead-acid battery 0.17 The reason the AGM isn't used in larger applications is that it cannot be recharged as it is being discharged. You left out a slew that use Deep Cells. IT does the job if you keep it over 50% just like clockwork and can last at least 2 to 5 years without going below 50% charge if you keep them above freezing and below 100 degrees (the same as the Lithiums). I use AGMs on a daily basis and my battery provider says I am the hardest on batteries he's ever seen. I am getting ready to do another build that uses the heavier Deep Cell which is designed to put up with my punishement. But the AGMs are more rugged than the Lithiums that I also use. Nacads also work but for about one run into town before they overheat. Ever seen a Nacad blow up? IT's pretty anticlimatic. They burst and make a mess out of everything around it. And it's caustic. Same goes for a Lithium except they will go into flame and feed the flame until all the liquid is used up. I have never had a case break open on an AGM. I've crashed em, dump em, drop em, used them for Rocky Mountain Offroad, and more. I can see that the Deep Cell Sealed Lead Acid should be as tough and have a longer run time but they are twice as heavy. Which is something of a problem for aircraft Just leave out that 1 six pack of Tomato Juice to make up the difference. It's not a real problem where an extra 10 pounds is really going to make a difference for something the size of the 787. An added 10 pounds for safety sake is very important. But it is a LOT more than 10 lbs!!!!! The lifespan of the Deep Cell the way I use batteries should be as high as the Lithium and cost less. But the weight means only my 3 wheelers will use them. They just don't make 10 to 15 amp deep cells. But they do make a very solid 35 amp at twice the weight and size of a 12 amp AGM. I am just not sold on Lithiums and I am certainly not sold on Nicads. The Airline Aircraft Industry can use the AGMS and have less problems, almost the same run time as the lower Lithium Mag batteries and save a bunch of money. Airbus use NiCads ,the Boeing 737, 747 (pre-800) and 777 use NiCads , they disagree with you. Nicads are old technology. The AGM batter is much newer. When they were designing the 737, 747 and 777 the AGMs weren't available. Single Airplanes use the AGMs and that is more critical for weight and safety than the big birds are. I use all these batteries in transporation every day. I am a dealer in the AGMs and the Lithiums as well as the motors and kits. I can also get you a good deal in Deep Cells but the shipping would be a killer. I used to handle Nicads but their output amps were just too low for any of the transport applications. They would get hot and burn out the controller after only a few miles of operation. I'll say it again, after a decade of actually using these batteries, using nicads is too problematic to depend on for safety. And the LiCo battery they used has yet to have an application in transportation because it's just too prone to problems as well. Unlike the Nicad that just gets hot or ruptures with no fire, the LiCo battery bursts into a very nasty bonfire. The safest and most dependable battery for them is still the AGM. Daryl |
#207
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Is the 787 a failure ?
On Fri, 22 Mar 2013 08:07:19 -0600, Daryl
wrote: On 3/22/2013 7:22 AM, Jim Wilkins wrote: "Daryl" wrote in message ... ...I have never had a case break open on an AGM. Daryl Then you haven't looked very hard. http://nissandiesel.dyndns.org/viewt...60ab1 12d039d "Problem: APC UPSs sometimes have a float charge voltage that is too high and tends to cook batteries. Here's a pair of gel/AGM batteries from a SUA1000 (not an XL) that have swollen so badly that I had to disassemble the case and pry the batteries out of the metal cage: " And you haven't seen a burst case either. Bulging, deformed, etc. case but the juice is contained in the case. DAryl I've had them split from top to bottom on both ends - but they are a "dry" battery. All of the liquid is absorbed in the mat - and by the time they split they are generally baked dry anyway. |
#208
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Is the 787 a failure ?
On Fri, 22 Mar 2013 16:39:07 -0000, "Keith W"
wrote: Jim Wilkins wrote: "Mr. B1ack" wrote in message ... Not interested in burning to death over the Pacific .... Better to fall into the South Atlantic because the Airbust didn't inform the pilots that it had stalled. Actually it did, they simply chose to disregard the stall warning that sounded continuously for 54 seconds and the stick shaker. Keith Because they believed the air speed indicator that was lying through it's teeth. |
#209
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Is the 787 a failure ?
wrote in message
... VERY common problem on "A Piece of Crap" UPS systems (as well as some cheaper ones) but when they split they don't leak. The acid in an AGM battery is Absorbed in the Glass Mat. jsw |
#210
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Is the 787 a failure ?
"GunnerAsch" wrote in message
... D batteries are what they use in some of the electric vehicles as I recall. Some 300 of them Or was it 3000? Gunner http://www.insightcentral.net/encycl...enbattery.html |
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