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ANA and Japan Airlines ground all 24 787 aircraft

Boeing's 787 Dreamliner has suffered multiple problems across the aircraft fleet this month. Boeing’s 787 Dreamliner got another ding on its record yesterday when an All Nippon Airways (ANA) aircraft had to make an emergency landing.
 
What is known about the emergency landing is that the cockpit display showed that the aircraft was having battery problems. Presumably, after the battery fire in Boston, pilots were taking no chances and landed the aircraft as soon as possible.
 
The batteries in these aircraft are especially important because the 787 Dreamliner fleet uses electrical systems rather than hydraulic systems found on most passenger aircraft.


All Nippon Airways 787 after emergency landing. [Image Source: Kyodo News]

After these issues, all 24 of the Boeing 787 Dreamliner aircraft operated in Japan by ANA and Japan Airlines have been grounded for safety checks. ANA owns 17 of the 24 aircraft with Japan Airlines owning the remainder. These 24 aircraft are nearly half of the 50 787 Dreamliners that have been delivered and flown commercially around the world.

In response to the issues with the aircraft, the FAA has launched a comprehensive safety review of 787 Dreamliner’s critical systems. This review will include an evaluation of how Boeing designs, manufacturers, and assembles the aircraft. Boeing has pledged to fully participate in review stating that it believes the process would bolster public confidence in the aircraft. 

Source: LA Times



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RE: Lithium Ion Batteries?
By drycrust3 on 1/16/2013 4:07:55 PM , Rating: 2
quote:
lithium ion don't discharge quickly as well as lead acid, that's why they work great for phones

You need to remember the battery kicks in whenever the dc supply voltage drops below the nominal battery voltage. So, for example, say an air conditioning unit suddenly decides to increase air flow speed, the motors all suddenly kick in and demand extra current, that drops the voltage below the nominal voltage, which creates a demand on the battery until the generators can take up the load.
There are several other points to note here.
Firstly, as I understand it, unlike for a lead acid battery, where a single cell of the battery is a complete unit in itself, i.e. a 100 Ampere-hour cell is built from the ground up as a 100 ampere hour cell, a "lithium cell" is actually thousands of smaller lithium cells paralleled together to form the one larger cell. The reason for this, so it was explained to me (on this website actually) is it is very difficult (and thus, expensive) to build large lithium ion cells, but very easy to build small ones, so they build thousands of small ones and stick them together to make the larger cell.
The problem with this approach is that your Mean Time Between Failures is, obviously, less by the factor of x thousand cells than that of the original cell that came off the production line. If some of the smaller cells fail and go "open circuit" then that means the rest of the cells within that cell will be overcharged. Without knowing exactly what happens when overcharged, one scenario is for there to be lots of smoke.
Conversely, if just one of them goes "short circuit" then it is essential to have some sort of fusing in place or ... you get another series of problems, which involve lots of heat (and possibly smoke).
The second point is that unlike a capacitor, which theoretically charges and discharges without any chemical reaction, a battery does use chemical reactions to store the electricity, which means heat is generated every time the battery is charged or discharged. Normally this heat isn't an issue, but if the battery does undergo a rapid discharges then it does.
When I heard this plane had a lithium ion battery it did strike me as being a rather bold move because, as I see it, it wasn't actually necessary (when compared against the total weight of the plane or the space required against what is available), secondly the "Volt" car showed there were reliability issues, thirdly it would be more expensive than an older technology battery, and fourthly, there could be problems obtaining a new one if it was required.
Two factors which raise a red flag are: 1)why this plane has been grounded over something as basic as a battery. To me, a plane of this expense should have been designed to take a lead acid equivalent, even if it never needed one, because it would be better to use a lead acid one than have an entire plane grounded in the event of a problem with the lithium ion one (which is exactly what has happened); and
2) Why the design team didn't go back and re-evaluate the need for a lithium-ion battery when the problems with the Chevy Volt became public.


RE: Lithium Ion Batteries?
By RDO CA on 1/16/2013 4:29:11 PM , Rating: 4
The Chev Volt problem was much different as the fire occured after a crash test on the car. They then stored the car without disconnecting the battery like GM says they should. It sat there leaking water from the battery cooling systen in very cold weather for several weeks before shorting out from the leaks.


RE: Lithium Ion Batteries?
By Samus on 1/16/2013 10:31:55 PM , Rating: 2
quote:
lithium ion don't discharge quickly as well as lead acid, that's why they work great for phones


That is complete bullshit.

Lithium batteries are capable of discharging and recharging at ridiculous rates, some more-so than others.

I've jumpstarted a truck with a 12.4v 4200mAH R/C Car lithium pack and it got warm, but hey, that's a 150 AMP draw, draining the capacity of the battery at 35 times its capacity. Some consumer packs are rated at 50C and higher (50 times capacity draw!)

Charging is different. Most packs are 2C-5C (not to be confused with 'cells', this means you can charge the pack at 2-5x its capacity.) For example, most cell phone battery packs are rated at 1C because they are crap, so a 2200mah battery pack shouldn't be charged at more than 2.2amps. An iPad charger puts out 5v@2a, so if you wanted to charge your 1500mAH iPhone battery in under an hour this would be a way to do it. The battery will get warm, but this won't shorten its life or do anything unsafe. The voltage cutoff and thermal monitor will shut off the charging and wait for it to cool, then resume, if ambient temps are too high for this to happen.

What I suspect Boeing is going to do is replace the chemistry with LiFePO4 or something else more stable at extreme cold/high temperature, pressure and vibration.

Lithium Ion is very delicate to any extreme, Lithium Polymer improves temperature and pressure tolerances but can still become unstable if super-heated or impacted. LiFePo fixes almost all of this, and since Aerospace is generally a safety-rules-all sector, spending a few extra grand on reliable batteries won't be a big deal.

Here's some basic consumer-level information of Li-Ion/LiPo for anybody curious:

http://www.rcgroups.com/forums/showthread.php?t=20...


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