Keep It Simple Stupid
 

Thank you RR for bringing this up.

This whole situation is a massive violation of KISS. This technology, which to the most casual observer should have been seen as too immature, is simply not appropriate for this application.

In a previous life, my job was to look at equipment my employer was considering buying. I certainly would have asked a lot of questions about this Rube Goldberg lash up. Didn't the airlines' technical departments ever look at it or did they just buy "a pig in a poke?"

Obviously the designers realized the fragility of the technology and introduced a convoluted monitoring system (which really didn't work) instead of just using a mature technology which might have weighed a couple of hundred pounds more and been a hell of a lot safer. The cost saving realized by shaving a minor amount of weight from the airplane has already been wiped out in the last month of groundings.

It's fine and dandy to discuss what went wrong with the current technology but that won't get the planes back in the air. Boeing et al need to get to work and substitute a mature technology for this convoluted mess and get back to flying airplanes. :ugh:

DG
 

Hi,

FlightPathOBN:

Even 11 pounds as cargo in PAX planes could be risky.

:{

And it was just a battery
 

Hi,

Smilin_Ed:

:sad:


And it was just a battery...

:{

I am wondering, and perhaps this has been addressed in this thread (somewhere)

But the white wires to the circuit board do not appear to have any heat protection, and it doesnt appear it would take to much to melt this bundle...what effect does one or a few of these wires have if shorted or disconnected?

A friend of mine is a drag racer. His drag racing "hero" has a quote that he always repeats. "The best way to cut 100 lbs off a race car, is to find 1600 ways to cut 1 ounce."

There are thousands of ways Boeing cut a little here and there to achieve weight savings. Every aircraft designer before now, has made the same choices. If you don't think that way, you should design ships instead. Or maybe try being an architect. But not an aeronautical engineer.

It would be easiest thing in the world to add weight here or there to be conservative. But you cannot do that and succeed. To succeed, you have to find a way to do it lighter, and INCREASE reliability at the same time.

If the 787 did not have a few problems, I would lose respect for Boeings' engineers as not being professional enough.

Light. Strong. Cheap.

Pick Two.

Safety Compromised
 

And in this case they compromised safety and DECREASED reliability.

The battery system is just like all of the other pieces of this aircraft that were designed to the micron, without any regard to constructability and general realistic materiels tolerances.

Remember the delamination due to the carbon fiber shims being "out of tolerance" to design specs, by microns? :mad:

it is also interesting to note that Boeing designs and tests the components individually, such as a single wing assembly, while Airbus tests entire wing/fuselage assembly, not only in design, but in aerodynamic modelling and destructive testing...

FlightPathOBN:


A discussion in another forum accidentally led me to the following site:
Battery Life and How To Improve It
Among other things, it explains that in addition to the lower chance of thermal runaway in an LiFePO4 cell compared to an LiCoO2 cell, the LiFePo4 has an almost zero volume change during charge/discharge cycling compared to as much as 11% in the LiCoO2 cell (Boeing 787), and that this repeated mechanical stress can damage the separator [leading to a short circuit]!
The fact that the Boeing batteries were unexpectedly being regularly discharged to a lower SOC than planned (because of ground operations error?) may be a critical factor in the reduced cell life.

Hiya Hangtown....

When Hersman said that NTSB were going to look at the process of certification, and that included manufacture and suitability, she didn't have to elaborate.

BOEING might have missed thermal cycling, and wrinkling, pinching, and abrasion issues, plus pressure cycle as well.

Likely not. Which would be worse, they missed all that, or that they did not?

And fit that LiCoO2 anyway? And folded the electrode instead of winding it?

Welcome, nice to have someone here from El Dorado County....

This is a good read also:

http://www.nfpa.org/assets/files/pdf...rieshazard.pdf

:ok:

Thanks for sharing excellent document.

@inetdog
Perhaps if an airline followed the rules/procedures for battery handling 'to the letter' repeated discharging to a lower SOC was inevitable? (In some areas this method of working is called 'working to rule'). I have lost count of the number of times when 'testing' a set of instructions that the author has said -"but nobody would do that!"

Ian W

Thanks. That takes us back to the beginning, in a good way. There was an energetic discussion regarding the potential problem that resulted in the grounding. My first reaction, and others, too, was that it likely was an ops thing.

New Technology? Well, Yes. If a system is recognized as a challenge, it is incumbent upon the airframer to support its entry into the operational. Training, monitoring, on site assessments, etc.

Especially so if this innovative solution is flight critical?

ROLLS made a minor mistake in the design of its TRENT 900. It was recognized, AD'ed and rectified. But for a "Duff Oil Pipe", the mistake would have gone unnoticed, save by wonks who read the AD's.

The engine builder was in process with a suitable upgrade when QF had an uncontained event, far more serious than what we see with the 787, imo.

What can happen, WILL happen, unless one has a lucky bunny foot.

Were the FRP batteries an upgrade? Or Boeing's willingness to support a poor system with endless replacements at a cost of a quarter million a year per a/c?

I think BOEING had it figured out, was in process, and got caught out by the few units it was gettng to, but did not quite get the problem rectified.

Is there another way to see it?

:ok:

Ian W

For a critical subsystem like this, it would be better to have automatic disconnect of
the battery at min voltage level, rather than depend on someone remembering to
switch the lights off.

Such failures can be designed out...

True, but perhaps it was not considered that someone would wait until that auto-disconnect or the level just before it - every single turnaround -

It might be instructive to look at the fleet of 787s that have been operating and see if every operator had the same battery turnover. Then compare the SOPs (and actual actions) of the highest and lowest turnover operators' .

Ian W


Absolutely. The answer to the entire discussion is in those 150 Batteries, and the reasoning behind the accelerated replacement. Thus far, it is annoying to see NTSB Stalled on the two batteries TAK/BOS....


Those two are the effects. The CAUSE is in researching the FRP.

imo.

:ok:

> There are thousands of ways Boeing cut a little here and there to achieve weight savings. Every aircraft designer before now, has made the same choices. If you don't think that way, you should design ships instead

Good ships are pretty sensitive to weight, especially where it is located. The new American LCS warships are deliberately not painted topsides to reduce weight. A decision they might be starting to regret ... we'll see.

Looking at the pictures of the (fresh) 787 battery unit, the wiring layout and execution doesn't appear to be to the standard you might expect of a safety-critical device. Also, there seems to be just one solitary thermocouple in the middle under a gob of resin.

Contrast that with this, the battery pack for a self-launching glider. Each cell is individually (and redundantly) monitored for voltage and temperature, with the facility to automatically heat the batteries to keep them in the ideal operating range if the OAT is low.

This isn't ultra-new technology, I think the above aeroplane has been around for at least a decade...

The mysterious thermal sensor?
 

This is the 'shadow' of the connection underneath the 'white gob' in the centre of the battery.

Looks like the fixing lug of a thermocouple. :-)

http://i1280.photobucket.com/albums/...ps1396355b.jpg

Just a question. Now that AB seems to be going back to ni-cad due to the uncertanty of lithium has the use of ni-nmh been considered. In model use they do the similar job to ni-cd but are lighter and smaller and seem to be pretty safe.