On 13-02-27 04:24, Uwe Klein wrote:
> LOT is bleeding.
> Thus it is possible that they will like money more than efficient planes.
> ( See also Qantas recently publishing results improved by compensation from Boeing )
And for Boeing, it allows it to use LOT's slots to deliver airplanes to
an airline would would be otherwise very angry at more delays. So it is
a win win situation.
> Boeing says it is final fix. ;-)
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 ?
or does this happen just as often except in those cases, it is just a
case of plugging in external power to start the airplane and the NiCd
batteries just get recharged ?
The solution would be to add some timer to deal with situations where
someone forgets to trun the lights off and the plane remains idle
without anyone in it, preventing batteries from being depleted.
Another change that needs to happen is for the battery box to first cut
off power before there is any damage to any cells, and allow inbound
power while outbound is blocked. This will allow the battery pack to be
safely recharged by the airplane and become usable once recharged
sufficiently.
If power is cut when voltage drops below the critical level, it means
that one or more cells are potentially damaged. But if you cut off power
before power drops to critical level, then you can safely recharge the
battery.
> 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. When you have "parents" taking
care of the problem child, they make sure to take good care of it. But
when the plane is at some commercial airport with contractors doing
refueliung, tugging etc, they are the ones which may end up triggering
conditions that the batteries don't like.
> 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 ?
> But there was ony one temp sensor.
Boeing has indicated this will change.
> Yes and/or start an attention grabbing alarm early during depletion.
In fact, in the cockpit, in case of an emergency where engines are out,
the pilots need to know if/when batteries are about to fail. I suspect
the RAT doesn't produce enough power for braking when landing. So if
batteries are nearly out, pilots would need to know to warn crews and
passengers that the plane will likely not be able to stop before end of
runway.
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.
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 ?
Surely in an engine out "glider" situation, the batteries would not be
powering galleys and IFE systems.
>> 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.
It is interesting that if they used regenerative braking, it would help
power the aircraft at landing instead of drawing huge amounts from
batteries.
(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 ?
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.
When a conventional plane is being towed, what systems are needed ? APU
to run hydraulics for steering and braking ?
I take it the 787 could be towed on battery power with batteries running
hydraulics ?
>> 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.
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 ?
What about the 747-800. Would its wiring be totally different from that
of the original 747 ?
> 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 ?
> 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 ? Are there bets who which
will be delivered for commercial use first the 787-900 or the A350 ?
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 !