Dreamliner grounded?

[DaveB]

My secretary (the wife) told me she'd seen on the box that the Dreamliner had been grounded. Found this on Auntie Beeb.. http://www.bbc.co.uk/news/business-21054089

I read not long ago that one had had a fire down in one of the electrical compartments. Seems the new girl has one or two niggles yet to be ironed out.

ATB
DaveB

[airboatr]

Yes Dave, Tis true, she's grounded. ..... for now.

[FlyTexas]

They'll get her fixed. They'd better be quick about it too.

Brian

[Chris Trott]

The problem it's being grounded for is the Lithium-Ion batteries (LiMH actually) because they've been overheating. The problem is that this part was very stringently tested before certification (and from what I understand was one of the reasons the FAA took so long to give final production authorization) and was having no issues when initially delivered. Now, suddenly they're having problems, every time either as or shortly after starting the APU on the aircraft. This leads me to believe that they are trying to charge the battery while starting the APU, something you NEVER do with such a battery. As with most chargers, unless you manually remove them from the battery, they will continue to charge as load is applied and there's no good way to mechanically or electronically disconnect it just while starting. As such, I think this is an operator issue and not a design problem, although now Boeing will probably be forced to put in some complex system to make it "impossible" to start the APU with the batteries charging or something like that that will only serve to cause more problems than it solves. Only JAL and ANA have had this issue. LOT, Ethiopian, and United have only had issues with the virtual circuit breakers and the generators kicking offline (not unusual on a new plane), not the batteries themselves, and from what I understand, were resolved pretty quickly with software updates.

[DaveB]

That seems an arse about face way of doing things in this day and age. Surely the charger could be electrically isolated when the batteries are online?? I dunno.. Boeing build an aircraft as technologically advanced as the 787 and yet leave a possible hole in the system like this.

ATB
DaveB

[Chris Trott]

I would look at the cell phone you have first. You know how it gets hot if you're charging it and using it? What about your laptop battery? That's why. It's a problem with the battery itself, not the system. Boeing designed a system that when used normally does disconnect the charger, but I get the feeling that JAL and ANA are bypassing it or doing something procedurally that is causing the problem since it's not popped up in any other operator's usage. Now Boeing will have to redesign the system in such a way that it either can't be bypassed or that is "fail-proof" enough to satisfy the FAA.

BTW, R/C model users have been dealing with this problem with this kind of battery for a while. They have special bags you put the batteries in to safely charge them in case of overcharge and rupture of the battery. They also act as a heat sink to help try and keep the battery from over heating during charging. The reason that everyone is acceptable to this kind of danger though is that for their weight, they pack several times the power as a NiMH battery (the previous "best" rechargeable battery type).

[airboatr]

Chris, I have to say, you sure do make us feel smarter.

[DaveB]

Smarter indeed

Most modern RC batteries are Li-Po which, it seems, are inherantly unstable. All of mine are Li-Po's but I don't use those 'charge bags' you mention. I prefer instead to not leave batteries 'on charge' unattended. My mains charger is designed in such a way that when charging is complete, the charge process stops. Also, if it detects the battery doing stuff it doesn't like, it also stops charging. I always use 'balanced charge' which monitors individual cells and charges them at the same rate. It takes longer doing it this way but ultimately, the battery gets a better charge.

Call me old fashioned but I'd not want to be relying on a battery which by it's nature, could be considered unstable, to power an aircraft.. a real one that is. This said, even 'normal'.. lead batteries can rupture and explode and for any number of reasons so I guess you've gotta go with the flow I'm sure Boeing will work something out to cut out the 'human' factor

Oh.. Li-Po's probably get much hotter during use than they do when being charged. Not sure if Li-Nm's are the same. A fast charge can cause a battery to heat up which is one reason why you shouldn't really fast charge but a normal, balanced charge leaves the batteries cool. Take one out of the model after 20mins spirited use.. less depending on the model, and they're suitable hand warmers

ATB
DaveB

[DarrenL]

This link was posted elsewhere - http://seattletimes.com/html/businesste ... onxml.html

Click on the photo on the page, comments were made regarding the standard of the wiring installation.

[Tomliner]

Did you know that the name Li Po comes from the great 'Ying Tong' song by the Goons?
Ying tong ying tong ying tong ying tong ying tong tidd LI PO. EricT
ps find it on YouTube and check.