
Boeing 787 Dreamliner back in US skies - dungerdunger
http://www.csmonitor.com/Environment/Energy-Voices/2013/0520/Boeing-787-Dreamliner-back-in-US-skies.-Battery-questions-linger?nav=92-csm_category-leadStory
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jerrya
Placing the batteries in a steel cased compartment with a vent to the exterior
of the plane to limit future, perhaps inevitable explosions and fires is an
example of

    
    
        1) __ An inspired engineering fix
    
        2) __ A kluge
    
        3) __ A feature, once the proper FAA documentation has been filed

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cmsmith
I would imagine that increasing the spacing between the cells actually fixed
the problem, while the case and vent are just limiting the PR and financial
liability.

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hkmurakami
pooch, your post is appearing as [dead] to me so your account may be
hellbanned, which you may want to get fixed since you've made an informative
post that many users won't be able to see.

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azth
Can you copy/paste it?

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uvdiv
_"From an electrical engineering standpoint, that makes no sense. Thermal
runaway starts when too much power is being drawn from the batteries and they
begin to overheat until exploding or melting, their promixity to each other
may limit the damage of an overloaded or malfunctioning cell, however the core
problem remains, why are 787 electronic systems overloading the batteries?"_

 _"If one cell explodes or melts, you still essentially have a fire in
progress. Protecting the other cells buys you time, but how much time do you
have when there is fire on a plane?"_

 _"Obviously its a design issue, probably very complex that Boeing simply
doesnt have the time and money to investigate thoroughly."_

 _"So this is a patch. Nothing I have read indicates an engineering approach
was taken to prevent the previous result."_

<https://news.ycombinator.com/item?id=5740563>

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yread
Airliners use generally two likelihoods of a failure: once in a billion hours
for events which can bring down the plane and once in 10 million hours for
events which don't take it down alone, but a combination of those can.

The problem with the batteries is that they were certified to fail once in ten
million hours but failed twice in 50000 hours. If both engines fail (unlikely,
but it can happen -birdstrikes, fuel contamination, it is one of the 10
million events), you need the main battery for powering avionics (if it fails
you're screwed) until APU is started and providing power (you have about 10
minutes, 2 APU start attempts). The APU battery is needed to start the APU.
Unfortunately, APU has fire protection which needs power to run, which is
drawn from the APU battery. So if APU battery fails at any time after APU
start, the system will shut the APU down and you'll lose all the power.

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downrightmike
With the mess this thing has been for so many years, there is no way I'm
getting on one.

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jahmed
The 747 has been flying since 1969. No one is 2050 is going to remember or
care about any of these issues.

~~~
downrightmike
This is how I'm seeing it: Look at all the times the 747 exploded and systems
had to be rebuilt. This thing already needs upgrades.

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_pmf_
There's no possible way that this problem has been fixed in a sustainable way
given the short time frame.

~~~
Someone
What do you mean by 'sustainable'/and your argument for that is?

An argument why this would be a working solution: the entire design went for
fuel efficiency. Apparently, they were overconfident in the reliability of
some parts. This fix adds some weight to diminish the impact of the
unreliability of those parts.

On the other hand, give that these planes probably will fly for half a century
or more, it would be very unlikely if they never modified this design in the
future. For example, further testing might show that this new steel container
is stronger than needed, or materials might improve, or new battery technology
will half the volume of these batteries, etc.

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kmasters
One thing to note re engine failure vs battery failures. In the 787 the
electrical power generation for hydraulic systems has been replaced by
electrical systems powered by these batteries.

If an engine fails, you can still land the plane. If these batteries fail, you
cannot. You have no power to guide the plane to a safe landing.

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bdonlan
If the battery fails, you still have power from the engine, APU generators,
and if all else fails the ram air turbine, no? According to [1], one battery
is used only for ground operations or backup braking power (so the primary
braking ought to still be operational if the battery fails) and the other
powers the APU starter motor and provides temporary power in the event of a
failure of engine generators until the RAT is operational.

[1] - [http://www.aviationweek.com/Article.aspx?id=/article-
xml/AW_...](http://www.aviationweek.com/Article.aspx?id=/article-
xml/AW_01_21_2013_p22-537845.xml)

~~~
Wingman4l7
A link with more about the RAT, for those who are curious -- it's a neat bit
of aviation engineering: <http://en.wikipedia.org/wiki/Ram_air_turbine>

