JF Mezei wrote:
> On 13-02-27 04:24, Uwe Klein wrote:
> Out of curiosity, how come refueling other airplanes doesn't result in
> their batteries being depleted because crews forget to turn off the
> battery after they are done ?
They don't start a bunch of powerhungry computers whenever some
access panel is opened.
>>They still need to find what strange effects kill the batteries.
> The problem is that ZA005 isn't being used in a commercial setting at
> some airport with normal airport workers.
There has been talk that sweaty passengers could well be
the deciding incredient. The Laredo incident was connected to
rain in the plane. condensation can be seen as FOD.
>>i.e. they took an arrangement for vented nonexpanding cells
>>and copied the physical arrangement of cells over to Li-Ion
>>hermetic and potentially expanding cells. dumb!
> I thought the Boeing Lithium Ion were not sealed and had vents ?
no the LVP65 Yuasa cells are prismatic 3.7V 65Ah nominal sealed Li-Ion
cells. The cells have burstplate in the upper third of the small sides.
Burst pressure should be around 650psi.
> Consider the Air Transat glider over the Atlantic, they ended up landing
> hard/fast, and without thrust reversers, I suspect the wheel brakes
> would be the big ticket item to get the plane to stop.
Yes. below speeds that allow power from the RAT the battery has
to power the brakes.
> Running out of fuel isn't something that is far fetched. It has
> happened. It will happen.
>>>787: LiIon: 32 volts, 28.6kg, 150amps for start up.
>>less than 30min endurance. no wonder customers run the battery down
>>in this mode.
> How can you draw the conclusion it only has 30 minute endurance ?
65Ah nominal will give you 30min @ 130A power draw ( actually a bit less )
> Surely in an engine out "glider" situation, the batteries would not be
> powering galleys and IFE systems.
they never do that. Theoretically the load on the batteries shouldn't
be all that much different from an 380 or A350.
But there is some kind of hitch hidden in that plane that Boeing has not divulged yet.
>>>So there is a huge difference with ability to provide huge current.
>>Current requirements for APU start are similar.
> I guess Boeing may state that LiIon can give 150amps, but they would
> need to specify how many amps are needed for APU start, and more
> importantly to brake aircraft without any engines.
I've done some well educated guessing.
APU start is 5..8 kW for 50seconds or a max of ~240A current draw
taking ~15% of battery charge for one start cycle.
incidentaly: Main engine start (GEnx-1B) takes 350kW max / 200kW average ;-)
> It is interesting that if they used regenerative braking, it would help
> power the aircraft at landing instead of drawing huge amounts from
purely friction braking.
> (and be able to brake with less heat generated at the wheel).
>>777 just has less loads in start up.
> When the plane is dark, wouldn't startup being roughly the same. A few
> lights, and turn on cockpit ?
Going by Boeings word : NO.
> Since Airbus appears to be able to easily switch the 350 to the NiCd
> batteries, it would appear that APU start doesn't need 150amps of power.
Boeing seems to use intrisic Li-Ion properties in some unconventional
( actually abusive ) way.
> When a conventional plane is being towed, what systems are needed ? APU
> to run hydraulics for steering and braking ?
a towed plane is passive. only lights.
> I take it the 787 could be towed on battery power with batteries running
> hydraulics ?
battery running nav lights. ( and always a bunch of computers.)
>>>BTW, on the 30 minute video, it is stated that eliminating high pressure
>>>bleed system saves about 2% of fuel.
>>I would contest that. ( viewing from a systemic approach. )
>>tsfc for the GEnx-2B is worse as it has less propulsive efficiency than
>>that larger fan -1B version.
> A fair comparison would be 2 engines of the same size, one with bleed
> air and the other with bigger generators.
> I think one of the big advantages with electric is that when you don't
> need de-icing, the electrical load is far less so the generators take
> less power from engines.
When you don't use much bleed you get full efficiency of the engine ;-)
> Do bleed air system have ability to vary amount of air allowed to escape
> from the compressor ?
> If de-icing is not needed at cruise, can they
> reduce bleed air and thus increase engine efficiency ?
>>All these "improvements" are really only true in relation to the 767.
> Since the 767-300ER dates from late 1980s, could its wiring system
> differ significantly from the original 767 with distributed power
> controlers to reduce amount of wiring etc, or would the "type
> certification" prevent such a big change in wiring philosophy ?
I don't thinks so. Boeing seems to have been rather conservative in that respect.
> What about the 747-800. Would its wiring be totally different from that
> of the original 747 ?
I don't think so. ( though it has the partial FBW from the A310 ;-)
It is a grandfathered cert.
After recent information gave some insight into FAA <> Boeing relationship
in respect to how certification is achieved ( self cert with FAA rubberstamping )
I understood how the grandfathering for the 737 and 747 was achieved.
EASA with a similar undertaking would have balked to no end.
And Boeing appears to be regularly unable to best Airbus under
the same certification requirements. i.e. only with newest tech
and the leeway older certification requirements provide is Boeing
able to be competitive.
>>To sum it up: There is not much on the 787 that you could not by
>>in Airbus craft before.( well, no electric aircon and antiice.)
> How does the 777 compare to the 787 in terms of wiring architecture ?
> Does it also have distributed power with reduced wiring requirememnts,
> or did Boeing still use more conventional power distribution on the 777 ?
The 777 has the cockpit section from the 767 while the rest could be seen
as a scaled 757. ( only partly joking )
The cockpit stuffing is said to be significantly different.
But I have no information about remote power control on the 777.
>>There are regular "on time, on spec or better" PR releases.
> Does "on time" mean anything for the 787 programme ?
>>We will have to wait for First Flight as an unfakable event.
> Has Boeing begun to assemble the first -900 ?
Part are said to be piling up.
> Are there bets who which
> will be delivered for commercial use first the 787-900 or the A350 ?
Haven't heard of any.
A350 seems to make good and securely achieved progress.
Airbus is contemplating to expand production beyond 10/month in 2019.
floated 180frames/a . Potential decission this summer.
Fixing problems early is the way to go. See "The Mythical Man Month",
IT related but a very good read. ( anything is IT related today ;-)
> And it isn't just a question of first flight and certification, but also
> of how/whether Boeing can ramp up production. At current rates, by the
> time Boeing will be done delivering launch orders, the aircraft will be
> senile already !
Some 787-8 frames will be 5..7 years old when delivered ( if ever )
I expect the 787 Mk2 to fare significantly better.
( Old english saying : never buy a Mk1 )
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