Boeing lithium batteries

On a sunny day (Fri, 8 Feb 2013 09:44:20 -0800 (PST)) it happened Richard Henry wrote in :

No but rumor goes the current plan is to do away with re chargeables, and buy new Duracells before each flight:

Follow articles in Aviation Week, The Wall Street Journal, and The New York Times. Eventually there will be a comprehensive report from the FAA and/or the NTSB.

The article in WSJ this morning said that the cause was traced to a battery cell shorting itself. Why the cell shorted is not yet known, but my guess is that vibration and bumps on landing are involved, mainly because most test labs do not fly, so flying is what's new. Another possibility is voltage spikes on the power busses due to the normal operation of something else in the airplane (other than the charging system).

Another article said that the FAA is pissed off at Boeing because their safety analysis was clearly deficient.

Joe Gwinn

Thanks for the suggestions, but I was hoping for something beyond the front-page ignorance.

What is not new is the corporate incentive to pass tests without any problems such as added cost or schedule delays. The most valuable employee a big company can have is the engineer who asks "But what if...?"

"Jan Panteltje" schreef in bericht news:kf3ima$iju$ snipped-for-privacy@news.albasani.net...

Yeah, but this plan has been cancelled or so I heard. They'd have to get rid of a vast number of exhausted batteries. This batteries could easily be dropped in the ocean when they fly above it but it seems Green Peeche protested and threatened to boycot the planes.

petrus bitbyter

Test labs do have vibe tables, though, and airplane designers do specify vibe and shock standards for avionics. Everything is expected to not only be designed for shock and vibe, but to be thoroughly tested.

Perhaps the difference is that they didn't shake things for 10 hours to simulate a trans-Pacific flight. I dunno. But you can bet they were specified, designed, and tested for vibe.

Again, this is a known phenomenon in avionics, and you design your boxes to withstand such, then test the hell out of them before you ship. If your customer is smart, they review your results, too.

The FAA tends to have a "blame the victim" mentality. If you go flying and you crash because you did something, it's pilot error. If you go flying and you crash because your equipment broke, then unless your mechanic seriously pulled the wool over your eyes it's pilot error because you took off with faulty equipment. If you go flying and you crash because of bad weather, it's your fault because you didn't pay attention to the weather. "Shit happens" is not a phrase to be found in the FAA dictionary.

Obviously, if Boeing did a safety analysis that said the batteries were OK, and they failed anyway, then ipso facto (by FAA logic) Boeing's safety analysis was clearly deficient. Heaven knows -- the FAA may even be right.

that's probably a good thing, their job it to find reasons for accidents and try to prevent them from happening again

remember one of the investigators on "air crash investigations" saying "pilots get too much of the glory and but also too much of the responsibility"

clearly something went wrong, Boeing estimated less than one event per 10million flight hours, now they've had two in fewer than 100,000

-Lasse

NTSB is conducting the investigation, not FAA. FAA has been put on the spot by NTSB and will eventually have to explain their approval of the Boeing testing. FAA and Boeing are both in the same pot of hot water.

I think that every airline that paid $200 - 250 million each is also pissed at Boeing, and will be exercising their rights under their contract to collect damages for their grounded planes.

Jon

Well, it is pretty obvious they took some shortcuts on this system. Either they contracted with Thales to torture-test this battery system, or they should have done it themselves. That would mean thermal cycling, vibration simulating flight plus takeoff/landing cycles, and charge/discharge cycles. They also should have done failure insertion tests to the charge/discharge control systems to deliberately cause over/undercharge situations that would damage the batteries and see how they fared.

So, either they didn't do the torture tests, or they didn't do them for enough cycles. Since some of these planes were delivered in 2011, it is possible they did quite a bit of due diligence, but just hadn't accumulated enough hours to bring on the failures. They have racked up quite a number of flight hours on the just 50 aircraft delivered so far. It would be VERY interesting to know the actual number of hours and flight cycles on the specific batteries that failed! I would almost guess they are among the older units deployed, and if they kept the fleet flying they would have developed more battery failures pretty soon.

Jon

According to another report I read, another point of contention is that the safety analysis claimed that a failure in one cell in the battery would (probably) not affect other cells in the battery.

Turns out it did... the failure of one cell seems to have released enough heat to compromise the adjacent cells, and the damage propagated throughout much of the battery.

I have not heard whether the original testing included a deliberate cascade test (i.e. inject a fault into one cell sufficient to short it internally, and confirm whether the damage remains contained or not).

Considering the amount of energy that these batteries pack in (NPI) I'm not terribly surprised that keeping damage contained to a single cell is difficult.

My theory/guess is that a cell shorted internally because of some anomoly of operating at high altitude.

The BMS certainly can't do a lot about a cell shorting internally.

boB

Yeah, since they are in the Yuasa aviation high reliability line, they would never have thought about the altitude thing...

Didn't the US government loan them (taxpayer) money to buy the planes in the first place? They'll just put an interest free moratorium on the payment schedule.

never have thought about the altitude thing...

Didn't know that. Where did you see that ? Of course none of the news or EE sites I saw said anything about that. Yuasa's been making batteries for quite a while. I would think they would be one of the best for this. Two installs and possibly two internally shorted batteries and BMS is supposedly been weeded out as a problem.

boB

Anything we do , to do with aircraft electronics is subject to strenuous vibration and temperature cycling over a period of days. Mind you, it's 99% Military... but I would have thought the same things/rules apply to civil aircraft ? I would have thought tests would be at least as stringent- many lives are at risk....

On a sunny day (Fri, 08 Feb 2013 17:25:47 -0600) it happened Jon Elson wrote in :

That is not the only problem, they have had a cracked window in the passengers compartment, and a cracked windscreen at the pilot's. This points to stresses in the composite? body. Anybody remember 'comet'? In that time they also tried to make things thinner and lighter, a bit too thin, and like a comet it fell..

And Airbus has also problems with cracks in the wings, some yacht made of composite material just broke into two halves. Those materials can handle stresses in only one direction. Bit of turbulence. Wonder where it will go.

And then there is the stability issue, Boeing had to use active control of the wings to avoid vibrations caused by airflow. Of course that works fine as long as all electronics and servos work.

But better is an airplane that is stable all by itself, and you can land as a glider... when no power.

This society is past the technology era, we are entering, or in -, a past-technology world, no more man on the moon, forget about other planets, even if NASA now says earth like ones are 'only' 15 light years away. We will all be extinct like the dinosaurs by the time that probe arrives...

The only hope now is on China, they are designing their own airplanes, and soon you will be able to buy those on ebay for a fraction of the price of a dreamplane. Probably nuclear powered electric engines...

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(Shrug) Give them 19,900,000 more flight hours and they could still meet spec!

-- john

dreamplane.

You are a true idiot. Why don't you go there, if you are so hep on a communist regime that got EVERYTHING handed to it or they stole it. And they still do.

first place? They'll just put an interest free moratorium on the payment schedule.

They've also got the tanker boondoggle to tide them over. $52bn is a considerably subsidy.

Best regards, Spehro Pefhany