FAA Grounds 787s
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From: Grassy Valley
And the 787 has two genset per side. That means at least two will be available, plus the RAT. When is 'redundant' beyond the pale?
Did Boeing 'miss' pushing for elimination of the standby power rule? Could they simply apply for offline Battery? Did they bite off a bit much in 'sampling' Lithium technology? Or did FAA deny such a proposal?
If batt is standby, why can't it be isolated in flight, even thirty minutes prior to and post flight?
ANA and JAL problems happened at TO and post parking. This problem may not be as critical as it might have seemed....
"INERTING" the batteries as part of the solution? It does say "STANDBY" in the regs.
Maybe someone who is not "uneducated" could respond?
Did Boeing 'miss' pushing for elimination of the standby power rule? Could they simply apply for offline Battery? Did they bite off a bit much in 'sampling' Lithium technology? Or did FAA deny such a proposal?
If batt is standby, why can't it be isolated in flight, even thirty minutes prior to and post flight?
ANA and JAL problems happened at TO and post parking. This problem may not be as critical as it might have seemed....
"INERTING" the batteries as part of the solution? It does say "STANDBY" in the regs.
Maybe someone who is not "uneducated" could respond?
Last edited by Lyman; 22nd January 2013 at 11:52.
Joined: Jan 2008
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From: Reading, UK
Adding 200lbs to the OEW of a commercial airliner is not hugely significant.
Weight always comes at a cost.
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From: Grassy Valley
Absolutely. 200 Pounds is a seat. The argument will not be, "You will not have a full aircraft every time, so we'll just discount its elimination..."
It will be, "That seat is five hundred dollars iost in revenue per leg."
"And that is two hundred thousand dollars every year...." conservatively...
It will be, "That seat is five hundred dollars iost in revenue per leg."
"And that is two hundred thousand dollars every year...." conservatively...
Joined: Aug 2011
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From: Upsate NY
Cost of 200lb
x 20 years 2M/200 rule of thumb, serveral $1,000 per / pound is what will be paid to get a pound out of a large aircarft (per aircarft). Or 1M could invested in engieering, to get a pound out of new deisgn were several K will be produced. So if 200 pounds of batteries = 50M in egeering and 10K per aircraft is no brainer to go for it.
Joined: Jun 2010
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From: On the ground too often
Is there someone her more knowledgeable who might be able to answer this question:
Is it usually the case that there is just one type of battery fitted across a particular type of airliner? Would this differ by version (i.e. also say a -800 vs. a -900) and by customer spec?
What I am driving at is that it would be very shortsighted of the manufacturer to build a charger compatible with only one specific battery type - be it chemistry or capacity. So perhaps retrofitting a different type of battery as an interim measure with weight penalty is a straightforward option?
I presume what Boeing is struggling to do at the moment is work out what actually did go wrong as the issue might not be in the battery itself.
Is it usually the case that there is just one type of battery fitted across a particular type of airliner? Would this differ by version (i.e. also say a -800 vs. a -900) and by customer spec?
What I am driving at is that it would be very shortsighted of the manufacturer to build a charger compatible with only one specific battery type - be it chemistry or capacity. So perhaps retrofitting a different type of battery as an interim measure with weight penalty is a straightforward option?
I presume what Boeing is struggling to do at the moment is work out what actually did go wrong as the issue might not be in the battery itself.
Joined: Oct 2002
Aviation Qualifications: PPL
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From: London UK
Absolutely. 200 Pounds is a seat. The argument will not be, "You will not have a full aircraft every time, so we'll just discount its elimination..."
It will be, "That seat is five hundred dollars iost in revenue per leg."
"And that is two hundred thousand dollars every year...." conservatively...
It will be, "That seat is five hundred dollars iost in revenue per leg."
"And that is two hundred thousand dollars every year...." conservatively...
Joined: Jan 2008
Posts: 17,728
Likes: 2,095
From: Reading, UK
the manufacturers have only themselves to thank for this perception that seat-mile costs are the be-all and end-all of life
There are some circumstances when SMC is the most relevant metric, and other circumstances where aircraft-mile cost matters more.That said, almost all airlines calculate their yield on a seat-mile/passenger mile basis.
Joined: Aug 2004
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From: Europe
Originally Posted by Sober Lark
... I'm finding it difficult to understand why the aircraft had to be grounded by the FAA rather than pilots or their representative bodies taking the initiative and refusing to fly them first.
Joined: Nov 2012
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From: USA
What's the big deal with this Lithium-Ion battery? Don’t they have a Liquid Ni-Cad certified to replace it? Type Certificate Data Sheets? What a dumb idea to utilize a new concept battery without a ready replacement.
TCDS - T000215E
Lit Bat - Special Conditions - 25-359-SC
Any Body have 25-359-SC details?
I can't find it.
TCDS - T000215E
Lit Bat - Special Conditions - 25-359-SC
Any Body have 25-359-SC details?
I can't find it.
Last edited by Temp Spike; 22nd January 2013 at 16:04.
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From: Blighty (Nth. Downs)
APU Start, and ETOPS
Quote from cod liver oil:
“Power source for B787 APU starting may be airplane battery, a ground power source, or an engine-driven generator.
Wouldn't engine-driven generator be used as primary power source for APU in-flight lightup?”
Probably not. I cannot quote the ETOPS/EROPS requirements, but suspect one of the scenarios they address is likely to be that of complete electrical-generation failure. That MAY mean that the ability to start the APU is mandatory for some or all ETOPS legs. I doubt it would be acceptable to rely on the RAT and its limited generation capability to provide essential services for several hours (although I stand to be corrected).
However, as an interim measure, it might be acceptable to start the APU as a pre-emptive measure prior to commencing the part of the sector where the ETOPS rules apply. If the APU failed to start (due to cold-soak, or whatever), you would have to divert somewhere. So it might make sense to leave it running on departure (off-load), and not shut it down until the ETOPS leg has been completed. The fuel-flow on an idle APU at high altitude is relatively modest.
FOOTNOTE
Wouldn't it be nice to have full schematics of the B787 electrical systems in the public domain, nearly 18 months after this civil aircraft entered service? In April 1988, when we started airline ops on the cutting-edge A320, no one put any pressure on line pilots to treat the contents of the FCOM as sensitive commercial information. Why is Boeing so shy of divulging its engineering achievements?
In the present circumstances, public rumour and speculation becomes all the more rampant when hard facts are so thin on the ground.
“Power source for B787 APU starting may be airplane battery, a ground power source, or an engine-driven generator.
Wouldn't engine-driven generator be used as primary power source for APU in-flight lightup?”
Probably not. I cannot quote the ETOPS/EROPS requirements, but suspect one of the scenarios they address is likely to be that of complete electrical-generation failure. That MAY mean that the ability to start the APU is mandatory for some or all ETOPS legs. I doubt it would be acceptable to rely on the RAT and its limited generation capability to provide essential services for several hours (although I stand to be corrected).
However, as an interim measure, it might be acceptable to start the APU as a pre-emptive measure prior to commencing the part of the sector where the ETOPS rules apply. If the APU failed to start (due to cold-soak, or whatever), you would have to divert somewhere. So it might make sense to leave it running on departure (off-load), and not shut it down until the ETOPS leg has been completed. The fuel-flow on an idle APU at high altitude is relatively modest.
FOOTNOTE
Wouldn't it be nice to have full schematics of the B787 electrical systems in the public domain, nearly 18 months after this civil aircraft entered service? In April 1988, when we started airline ops on the cutting-edge A320, no one put any pressure on line pilots to treat the contents of the FCOM as sensitive commercial information. Why is Boeing so shy of divulging its engineering achievements?
In the present circumstances, public rumour and speculation becomes all the more rampant when hard facts are so thin on the ground.
Joined: Jan 2008
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From: uk
Weight penalty
There do seem to be some wild figures being mentioned in this thread with regard to weight penalty. What we do know for a fact is that the 8 cells used weigh 22 Kg in total. Now multiply that by whatever factor you have for the existing approved technology subtract 22 and you have the weight penalty.
My fear in this instance is that the very fact of the approval process has in this case led to the use of a fundamentally less safe chemistry because it is already approved for aerospace use. The assumption being that the numerous fires that have occurred with LiCo batteries are down to careless use and this would not happen in aviation.
There can be no doubt that the charging arrangements include individual cell voltage monitoring and temperature monitoring seems most likely.
I think the idea mentioned in a much earlier post of isolating the battery during flight has merit as a wokaround solution. After all these batteries are only a standby and have negligible self discharge rates. So charge the batteries on the ground then switch off charging, continue to monitor cell temp and voltage during flight.
My fear in this instance is that the very fact of the approval process has in this case led to the use of a fundamentally less safe chemistry because it is already approved for aerospace use. The assumption being that the numerous fires that have occurred with LiCo batteries are down to careless use and this would not happen in aviation.
There can be no doubt that the charging arrangements include individual cell voltage monitoring and temperature monitoring seems most likely.
I think the idea mentioned in a much earlier post of isolating the battery during flight has merit as a wokaround solution. After all these batteries are only a standby and have negligible self discharge rates. So charge the batteries on the ground then switch off charging, continue to monitor cell temp and voltage during flight.
Joined: Jul 2002
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From: UK
Joined: Jan 2008
Posts: 2,173
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From: Blighty (Nth. Downs)
DozyW,
Am going partly on what TURIN wrote a few days ago.
However, there must be a fair number of grounded B787 crews at the moment, who are kicking their heels and presumably surfing the forums to see what is being speculated. Have you found something I've missed?
Am going partly on what TURIN wrote a few days ago.
However, there must be a fair number of grounded B787 crews at the moment, who are kicking their heels and presumably surfing the forums to see what is being speculated. Have you found something I've missed?
Joined: Dec 2000
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From: on the golf course (Covid permitting)
@Chris Scott
The following link has a basic overview of the electrical architecture in it. Worth noting the Boeing publication os from 2005, so it may well have changed since then!
B787 Systems and Performance
Hope that is of some use.
The following link has a basic overview of the electrical architecture in it. Worth noting the Boeing publication os from 2005, so it may well have changed since then!
B787 Systems and Performance
Hope that is of some use.