ANA 787 makes emergency landing due 'battery fire warning'
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Originally Posted by m.Berger
When Comets crashed, they were so important as an export earner that the Government gave orders to blame the pilots (as I have heard reported Airbus still do.)..........
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"Like Habsheim and the A330 Test flight? Both long suspected to be computer glitches but successfully blamed on the pilots."
What those two had in common was not computer glitches, but inadequate preparation by the crew.
What those two had in common was not computer glitches, but inadequate preparation by the crew.
Excuse my ignorance, but why are the French Authorities getting involved?
Do they mean EASA?
Do they mean EASA?
Ah yes, of course. Thanks.
Plastic PPRuNer
Seven (7) YEARS to design a battery charger?
Even a VERY VERY special battery charger?
JFK's speech about going to the Moon was in 1961, by 1969 they were there.
I'm confused.
Even a VERY VERY special battery charger?
JFK's speech about going to the Moon was in 1961, by 1969 they were there.
I'm confused.
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How cold does it get in the bay where the battery is located? I recall reading somewhere that charging when cold can lead to problems with short circuits but I think Li manganese cells can work down to -40C.
It's a pressurised and conditioned area. Plenty of heat generated in there by the CMSCs etc. Thats why they are liquid cooled.
Mac the Knife
In industry, time to proof of concept for a design like that would not be more
than 6 months, using rapid development techniques. Time to market is critical in
industry, where you need to steal a march on your competitors, or just get the
product generating revenue. Safety critical products are shielded from all that in
theory, with very complex processes and audit trails covering every aspect of the
design. 7 years does seem a bit long winded, but we have no info on specification
drift, or how many changes or complete rewrites happened during that time.
Of course, all that process still doesn't mean that the design is fit for purpose,
only that it meets the original spec
Turin
One thing I did notice from the battery data sheet was the max temp of 65
degrees C, which doesn't leave much sensing headroom if one or more cells
starts to get hot, assuming a single enclosure temperature sensor.
Max discharge rate is 5C, 325 amps, so they will be limiting the apu starter
current. Typical starter current could be > 500 amps without a starter panel
or other current limiting device.
Seven (7) YEARS to design a battery charger?
than 6 months, using rapid development techniques. Time to market is critical in
industry, where you need to steal a march on your competitors, or just get the
product generating revenue. Safety critical products are shielded from all that in
theory, with very complex processes and audit trails covering every aspect of the
design. 7 years does seem a bit long winded, but we have no info on specification
drift, or how many changes or complete rewrites happened during that time.
Of course, all that process still doesn't mean that the design is fit for purpose,
only that it meets the original spec
Turin
One thing I did notice from the battery data sheet was the max temp of 65
degrees C, which doesn't leave much sensing headroom if one or more cells
starts to get hot, assuming a single enclosure temperature sensor.
Max discharge rate is 5C, 325 amps, so they will be limiting the apu starter
current. Typical starter current could be > 500 amps without a starter panel
or other current limiting device.
FlightPathOBN :
The wiring you are seeing in those photos is for cell voltage sensing. The (unmelted) bundles can be seen through the plastic barrier on the RHS of photo #194. It appears to be bundled, tied and routed neatly, as is common practice in most aircraft electronics.
The high current connections consist of metal straps (probably copper with an insulating coating) between the individual cell studs.
My comments from post #191 and #194 were from looking at the wiring connecting the cells.
The high current connections consist of metal straps (probably copper with an insulating coating) between the individual cell studs.
Quote from syseng68k:
"Max discharge rate is 5C, 325 amps, so they will be limiting the apu starter current. Typical starter current could be > 500 amps without a starter panel or other current limiting device."
Yes, and the rest... See my post on the "787 Batteries and Chargers" thread:
"The A320 uses its 2 main (NiCd) batteries for APU start if no external power is available. In the 1990s, when starting the APU using external power, I was able to monitor the two TR loads. Initially, they would be off-scale but, IIRC, they reappeared as the current was falling through 350 amps (each). So the peak current delivered by the TRs was in excess of 700 amps. But the main (NiCd) battery was also contributing, so this suggests a peak starter load of the order of 1000 amps."
"Max discharge rate is 5C, 325 amps, so they will be limiting the apu starter current. Typical starter current could be > 500 amps without a starter panel or other current limiting device."
Yes, and the rest... See my post on the "787 Batteries and Chargers" thread:
"The A320 uses its 2 main (NiCd) batteries for APU start if no external power is available. In the 1990s, when starting the APU using external power, I was able to monitor the two TR loads. Initially, they would be off-scale but, IIRC, they reappeared as the current was falling through 350 amps (each). So the peak current delivered by the TRs was in excess of 700 amps. But the main (NiCd) battery was also contributing, so this suggests a peak starter load of the order of 1000 amps."
Chris
Agree with everything in that post. I have no professional involvement
with starting issues, but some (murky?) history. There's a loosely connected
group of individuals here in the uk that like to restore and run surplus
gas turbine engines, an offshoot from the historic aviation pastime. Makes
a change from classic cars. One collector in Bristol even has a Derwent that
gets spooled up from time to time. Anyway, my effort was a Rover APU from a
Vulcan a/c, which was remounted in a frame with instruments to run at airshows
such as Bruntingthorpe. I can put up some pics later if anyone's interested,
but that particular engine was quite small, 30Kva + bleed air and 28v electric
start. In a car engine, the starter only runs for a few seconds, while a
turbine engine can take 10's of seconds to spool up, putting a high load
both on starter and battery. On initial testing, measured current was around
700amps, which ran back with increasing speed and rising back emf to
200 or so at lightup. In the Vulcan, the apu had a fairly conventional
starting panel for the time, where the motor was initially started with several
low value resistors in series to limit the current. For those who are old enough
remember trolley busses or trams, there was a tick tick ticjk noise as the tram
accelerated away, progressively shorting out the current limiting resistors.
Same for a turbine engine starter panel, where the series resistors are
progressivly shorted out as the engine spools up.
With modern kit, engines are more fficient and electronics will play a much
bigger role, but if the apu is 1.25Mw rating, ie: a much bigger engine, how do
they manage to get that spooled up within the battery rating of 325A max load
and 65C max temp ?. Quite a technical achievement, however it's done...
Agree with everything in that post. I have no professional involvement
with starting issues, but some (murky?) history. There's a loosely connected
group of individuals here in the uk that like to restore and run surplus
gas turbine engines, an offshoot from the historic aviation pastime. Makes
a change from classic cars. One collector in Bristol even has a Derwent that
gets spooled up from time to time. Anyway, my effort was a Rover APU from a
Vulcan a/c, which was remounted in a frame with instruments to run at airshows
such as Bruntingthorpe. I can put up some pics later if anyone's interested,
but that particular engine was quite small, 30Kva + bleed air and 28v electric
start. In a car engine, the starter only runs for a few seconds, while a
turbine engine can take 10's of seconds to spool up, putting a high load
both on starter and battery. On initial testing, measured current was around
700amps, which ran back with increasing speed and rising back emf to
200 or so at lightup. In the Vulcan, the apu had a fairly conventional
starting panel for the time, where the motor was initially started with several
low value resistors in series to limit the current. For those who are old enough
remember trolley busses or trams, there was a tick tick ticjk noise as the tram
accelerated away, progressively shorting out the current limiting resistors.
Same for a turbine engine starter panel, where the series resistors are
progressivly shorted out as the engine spools up.
With modern kit, engines are more fficient and electronics will play a much
bigger role, but if the apu is 1.25Mw rating, ie: a much bigger engine, how do
they manage to get that spooled up within the battery rating of 325A max load
and 65C max temp ?. Quite a technical achievement, however it's done...
APU Start
On the 787 is via a starter/generator. That's an AC device, fed from the start battery or other source through a variable frequency inverter. So the start characteristics of this will be very different from an APU that uses a 24 Vdc starter motor.
Variable frequency drives can be programmed to limit locked rotor inrush currents, torque vs speed and other parameters. So comparing the A320 to the 787 is apples and oranges.
Variable frequency drives can be programmed to limit locked rotor inrush currents, torque vs speed and other parameters. So comparing the A320 to the 787 is apples and oranges.
EEngr:
Thanks for that. Apart from improved controllability, a vfd would increase
efficiency and reduce weight over a dc solution.
One thing that struck me about the main power distribution was the almost
complete use of dc. This would suggest most of the high power rotating loads
are inverter driven. Apart from efficiency savings, there could be significant
weight gains if high frequency (ie: > 400Hz) motors could be used.
Do you have info w/regard to this ?...
Thanks for that. Apart from improved controllability, a vfd would increase
efficiency and reduce weight over a dc solution.
One thing that struck me about the main power distribution was the almost
complete use of dc. This would suggest most of the high power rotating loads
are inverter driven. Apart from efficiency savings, there could be significant
weight gains if high frequency (ie: > 400Hz) motors could be used.
Do you have info w/regard to this ?...
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Main power distribution almost all DC?
That is confusing. the generated power is almost exclusively AC, and travels to EEBay fror rectifucation and DC distribution. The ECP motors are adjacent the EEBay, and the wing de ice cabling is AC to the wing?
From a cabling weight perspective alone, is it not the plan to carry distribution in AC power as much as possible?
That is confusing. the generated power is almost exclusively AC, and travels to EEBay fror rectifucation and DC distribution. The ECP motors are adjacent the EEBay, and the wing de ice cabling is AC to the wing?
From a cabling weight perspective alone, is it not the plan to carry distribution in AC power as much as possible?
Power FROM the gennies is 235vAC Frequency Wild.
The output TO the users (starters, hydraulic pumps, Cabin Air Compressors ) is +/-270vDC Variable frequency square wave.
To an old fashioned Airframe/Engine Tech such as myself it's still AC but Boeing insist it is DC.
The output TO the users (starters, hydraulic pumps, Cabin Air Compressors ) is +/-270vDC Variable frequency square wave.
To an old fashioned Airframe/Engine Tech such as myself it's still AC but Boeing insist it is DC.
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@ Turin #245 [OT]
+/-270vDC Variable frequency square wave.
a pretty bang up to date aircraft electrical system, but how much excess capacity is left??
Turin:
Looking at the block diagram above your post, all that's in the path
betweeen ac source and 270v bus is a tru, which normally just transforms
and rectifies the ac to provide full wave rectified dc, not a square
wave.
The motor controllers are variable frequency drives, from another post,
which work by chopping (ie: square wave) dc at a much higher frequency
to synthesise a sine wave at the frequency of interest. My guess is that
is what's happening, or do you have other info ?...
Power FROM the gennies is 235vAC Frequency Wild.
The output TO the users (starters, hydraulic pumps, Cabin Air
Compressors ) is +/-270vDC Variable frequency square wave.
To an old fashioned Airframe/Engine Tech such as myself it's
still AC but Boeing insist it is DC.
The output TO the users (starters, hydraulic pumps, Cabin Air
Compressors ) is +/-270vDC Variable frequency square wave.
To an old fashioned Airframe/Engine Tech such as myself it's
still AC but Boeing insist it is DC.
betweeen ac source and 270v bus is a tru, which normally just transforms
and rectifies the ac to provide full wave rectified dc, not a square
wave.
The motor controllers are variable frequency drives, from another post,
which work by chopping (ie: square wave) dc at a much higher frequency
to synthesise a sine wave at the frequency of interest. My guess is that
is what's happening, or do you have other info ?...