FAA Grounds 787s
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To gather relevant data this time (contrary to the test standards obviously not able to duplicate the issue and real in-service conditions), the 787 should be operated as it is intended to do, as a point-to-point long range aircraft connecting totally different climate zones.
Last edited by FlightlessParrot; 12th Apr 2013 at 08:13.
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Turn the present fleet into freighters, equip all flight-crew with parachutes and personal oxy. supplies....pay 'em danger-money.......THERE, ! job sorted, on the cheap. revenue generating, data accumulating, minimal number of Humans at risk..
Easy, aint it!
Easy, aint it!
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Rubbish
To gather relevant data this time (contrary to the test standards obviously not able to duplicate the issue and real in-service conditions)
What a load of crap, so fly the 787 180 Etops, it catches on fire and then its ok..
No the 787 should be Non ETOPS till they find the cause, if they cant then good bye to Li Ion baterries and redesign with proven Nicads and recertify the electrical system..
You cant let an aircraft fly ETOPS if it has a fault and you cant find the cause, thats just tombstone statistics to even try!
What a load of crap, so fly the 787 180 Etops, it catches on fire and then its ok..
No the 787 should be Non ETOPS till they find the cause, if they cant then good bye to Li Ion baterries and redesign with proven Nicads and recertify the electrical system..
You cant let an aircraft fly ETOPS if it has a fault and you cant find the cause, thats just tombstone statistics to even try!
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United has aready announced June 10 service of the 787. I guess the FAA is happy with the battery fix. It seems like a fine airplane so expect it to do well. Boeing has never made a bad plane so I am sure this one will do well also.
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inetdog
That I do not know. I have not heard anything about the JTSB reducing ETOPS, but I expect we'll know when both carriers re-start operations.
Kiskaloo, does this temporary loss of certification (or at least loss of confidence) restart the clock, or has the time been put in and only approval is needed?
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What a load of crap, so fly the 787 180 Etops, it catches on fire and then its ok..
No the 787 should be Non ETOPS till they find the cause, if they cant then good bye to Li Ion baterries and redesign with proven Nicads and recertify the electrical system..
Suggesting NiCads is foolish and reveals a lack of understanding of the system.
You cant let an aircraft fly ETOPS if it has a fault and you cant find the cause, thats just tombstone statistics to even try!
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Well, after watching some of the NTSB hearing, it will be very interesting to see what happens, and how the FAA will react to the NTSB.
There were very clear directions that the NTSB went down in the questioning.
I thought there were some surprising answers from the panels.
It will be interesting to see what the press picks up on from this.
The next hearing, on the 787 specific, will likely be even more entertaining.
There were very clear directions that the NTSB went down in the questioning.
I thought there were some surprising answers from the panels.
It will be interesting to see what the press picks up on from this.
The next hearing, on the 787 specific, will likely be even more entertaining.
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@Machaca
I would not read redundancy into having the engine and APU generators in pairs at each of the three locations. Rather, I would identify reasons for the smaller generators, having nothing to do with redundancy.
1. At 250 kva each at the chosen voltage (230 volts 3-phase), the amperage per phase at the main engines is already over 600 amperes in each unit. It has got already to be difficult to build a unit this size for 400/800 cycle service.
2. Starting an engine can apparently be accomplished by one of the two generator/starter on the engine. This materially reduces the problem of throwing this machine, in starter mode, across the line. Should the main turbine be having a bad day, the second generator/starter can be added after the first is turning; that is very much easier as being geared to the turbine, it's already turning also. It is initially putting current into a non-moving electric machine that is a real problem. The diesel engines that drive the ramp generators just do not have any short-term higher power output, in contrast to the short-time needs of starting rotating electrical machines. It's a common cause of diesel engine-generator stalling.
3. The 250 (or 225 @APU) KVA generator/starter size has a potential market in lesser planes, which is an economic factor.
4. Loss of a main turbine takes out two generators. How realistic is it to call one generator a back up to the other? The APU generators are the back up, hence the importance of being able to start that system aloft.
5. The 787 electric power load is double or more its predecessors. Double the number of generators is more necessary than redundant.
I would not assume those who raise questions here necessarily fail to understand these types of systems.
OE
All potential causes are addressed in the updated system. Of course it should fly ETOPS - the 787 has twice the electrical redundancies of a 767: four engine generators vs two, two APU generators vs 1.
1. At 250 kva each at the chosen voltage (230 volts 3-phase), the amperage per phase at the main engines is already over 600 amperes in each unit. It has got already to be difficult to build a unit this size for 400/800 cycle service.
2. Starting an engine can apparently be accomplished by one of the two generator/starter on the engine. This materially reduces the problem of throwing this machine, in starter mode, across the line. Should the main turbine be having a bad day, the second generator/starter can be added after the first is turning; that is very much easier as being geared to the turbine, it's already turning also. It is initially putting current into a non-moving electric machine that is a real problem. The diesel engines that drive the ramp generators just do not have any short-term higher power output, in contrast to the short-time needs of starting rotating electrical machines. It's a common cause of diesel engine-generator stalling.
3. The 250 (or 225 @APU) KVA generator/starter size has a potential market in lesser planes, which is an economic factor.
4. Loss of a main turbine takes out two generators. How realistic is it to call one generator a back up to the other? The APU generators are the back up, hence the importance of being able to start that system aloft.
5. The 787 electric power load is double or more its predecessors. Double the number of generators is more necessary than redundant.
I would not assume those who raise questions here necessarily fail to understand these types of systems.
OE
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Old Engineer:
2. Starting an engine can apparently be accomplished by one of the two generator/starter on the engine.
4. Loss of a main turbine takes out two generators. How realistic is it to call one generator a back up to the other? The APU generators are the back up, hence the importance of being able to start that system aloft.
2. My understanding it that even though the two S/Gs are identical, only one of them is wired to be used for starting via the APU battery. It is not selectable. So you have two generators, but only one starter, at least when only battery power is available.
4. I have seen the claim seriously made by Boeing that the APU is needed for ground operation only and that flight safety without engines can be maintained well enough by the RAT. According to this argument, the two APU generators are only important for delivering enough power for comfort and convenience on the ground and for starting the main engines without needing an excessive number of ground power units. I do not know whether just one of the generators is sufficient for that or if both are needed, going along with your point #1.
Yet, at the same time, Boeing PR is going strong pushing how safe the plane is with six redundant generators. Trying to have it both ways, I guess.
2. Starting an engine can apparently be accomplished by one of the two generator/starter on the engine.
4. Loss of a main turbine takes out two generators. How realistic is it to call one generator a back up to the other? The APU generators are the back up, hence the importance of being able to start that system aloft.
4. I have seen the claim seriously made by Boeing that the APU is needed for ground operation only and that flight safety without engines can be maintained well enough by the RAT. According to this argument, the two APU generators are only important for delivering enough power for comfort and convenience on the ground and for starting the main engines without needing an excessive number of ground power units. I do not know whether just one of the generators is sufficient for that or if both are needed, going along with your point #1.
Yet, at the same time, Boeing PR is going strong pushing how safe the plane is with six redundant generators. Trying to have it both ways, I guess.
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Boeing PR is going strong pushing how safe the plane is with six redundant generators. Trying to have it both ways, I guess.
IMHO, this once-proud company is being sold down the river by a bunch of city slickers.
(deafening muteness on the P.M.Alternators,as well....if an ENGINEER had been consulted ,before releasing this diarrhoea, you can be sure he will have corrected the TRUE redundancy -figures,and ADDED the Alty's.
As O E so rightly points out, the redundancy-level is only down to the motive-power.....Granted, If one starter/gen. croaks, that engine only loses HALF it's generating-capacity.....but if both engines DID stop...you lose the lot and rely on the APU battery's integrity , plus the RAT.
The scenario is extremely unlikely ,but the regulatory authorities have determined that it's a REAL POSSIBILITY and therefore LEGISLATED PROTECTIVE MEASURES to mitigate the risk.
An unstable battery in a tin box, does not, IMHO, demonstrate any moral, legal or financial will to comply with the spirit.
Maybe i'd fly on it in 5 years time.
Inetdog
I think you are confusing Engine starter/generators and APU starter/generators.
Only one starter is required to start an engine, it's slow (3 mins) but it will do it. Normally both are used but it needs both APU generators supplying or three ground power units.
The APU on the other hand only uses one starter at a time. One 'hard wired' as it were, to the APU Bat Bus, the other from one of the main distribution busses.
Essentially correct but it depends on what you mean by 'redundancy'.
The APU generators will need to be operational if the a/c is dispatched with an engine generator inop.
The statistical evidence from many years of ETOPs OPS is that the chances of a single engine failure mean that the APU can be inop for dispatch.
However if you dispatch with one engine generator inop the chances of losing the other (generator) increase, therefore APU (generator) must be operational.
This is standard ETOPs policy.
Is the 787 any different in this regard? No. Unless of course you are mid atlantic on an MEL with one gen inop, you lose the other engine and then the APU battery gives up, shutting down the APU.
In the past, all very unlikely, but with the 787 a bit more likely. Too much more for my liking. An independent power source for the APU is a must until these batteries can prove their reliability. The main engines will keep running if you lose all electrical supplies because they have a PMG. Why not on the APU?
I think you are confusing Engine starter/generators and APU starter/generators.
Only one starter is required to start an engine, it's slow (3 mins) but it will do it. Normally both are used but it needs both APU generators supplying or three ground power units.
The APU on the other hand only uses one starter at a time. One 'hard wired' as it were, to the APU Bat Bus, the other from one of the main distribution busses.
4. I have seen the claim seriously made by Boeing that the APU is needed for ground operation only and that flight safety without engines can be maintained well enough by the RAT. According to this argument, the two APU generators are only important for delivering enough power for comfort and convenience on the ground and for starting the main engines without needing an excessive number of ground power units. I do not know whether just one of the generators is sufficient for that or if both are needed, going along with your point #1.
Yet, at the same time, Boeing PR is going strong pushing how safe the plane is with six redundant generators. Trying to have it both ways, I guess.
Yet, at the same time, Boeing PR is going strong pushing how safe the plane is with six redundant generators. Trying to have it both ways, I guess.
The APU generators will need to be operational if the a/c is dispatched with an engine generator inop.
The statistical evidence from many years of ETOPs OPS is that the chances of a single engine failure mean that the APU can be inop for dispatch.
However if you dispatch with one engine generator inop the chances of losing the other (generator) increase, therefore APU (generator) must be operational.
This is standard ETOPs policy.
Is the 787 any different in this regard? No. Unless of course you are mid atlantic on an MEL with one gen inop, you lose the other engine and then the APU battery gives up, shutting down the APU.
In the past, all very unlikely, but with the 787 a bit more likely. Too much more for my liking. An independent power source for the APU is a must until these batteries can prove their reliability. The main engines will keep running if you lose all electrical supplies because they have a PMG. Why not on the APU?
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Utter Rubbish
Quote "All potential causes are addressed in the updated system. Of course it should fly ETOPS - the 787 has twice the electrical redundancies of a 767: four engine generators vs two, two APU generators vs 1."
The 787 is a pure electrical aircraft for for airconditioning and Hydraulics, even thought the left and right have electrical & engine driven pumps...to say it has twice the redundancies is garbage.
A valid scenario...one Engine driven generator inop so as per the MEL permissible to operate supposely ETOPS with the APU running...
Aircraft dispatches...APU Battery fails - APU will shutdown due no APU battery on the APU Hot Batt Bus.
Left with one engine generator supplying the whole aircraft plus a RAT which only supplies limited power....if the main battery fails, what are the results, no contactor management availability, so the position of main power contacts stay in there last place, possible dead short on the Hot Battery Bus...
Yeah fly the 787 ETOPS and risk a major disaster...
The 787 should loose all ETOPS! Till it can prove the Li ion Battery technology is safe, building a Band Aid box to contain a fire or thermal runaway isnt a fix!
The 787 is a pure electrical aircraft for for airconditioning and Hydraulics, even thought the left and right have electrical & engine driven pumps...to say it has twice the redundancies is garbage.
A valid scenario...one Engine driven generator inop so as per the MEL permissible to operate supposely ETOPS with the APU running...
Aircraft dispatches...APU Battery fails - APU will shutdown due no APU battery on the APU Hot Batt Bus.
Left with one engine generator supplying the whole aircraft plus a RAT which only supplies limited power....if the main battery fails, what are the results, no contactor management availability, so the position of main power contacts stay in there last place, possible dead short on the Hot Battery Bus...
Yeah fly the 787 ETOPS and risk a major disaster...
The 787 should loose all ETOPS! Till it can prove the Li ion Battery technology is safe, building a Band Aid box to contain a fire or thermal runaway isnt a fix!
Last edited by Goddamnslacker; 14th Apr 2013 at 09:30.
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A box around the battery isn't the fix, the fix is the modified BMU processors. The box is there largely to keep the public happy. I expect the box itself will be gone before too long.
If you look at the 787 battery solution as being largely about containment, you've missed most of the alterations made to the batteries and their charging and monitoring systems.
If you look at the 787 battery solution as being largely about containment, you've missed most of the alterations made to the batteries and their charging and monitoring systems.
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[QUOTE][ you've missed most of the alterations made to the batteries and their charging and monitoring systems.
/QUOTE]
Which begs the question,- How the hell did a "not fit for purpose" system ever get certified in the first place?
The smokescreen continues!
/QUOTE]
Which begs the question,- How the hell did a "not fit for purpose" system ever get certified in the first place?
The smokescreen continues!
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where can we find those BMU-fix details?
@whatdoes..
[A box around the battery isn't the fix, the fix is the modified BMU processors...the alterations made to the batteries and their charging and monitoring systems.]
[A box around the battery isn't the fix, the fix is the modified BMU processors...the alterations made to the batteries and their charging and monitoring systems.]
Mac, #1611
Funny, have been looking for weeks to find a list of the bmu / charger modifications,
even an overview, but can find nothing. Perhaps you could post a link or two ?...
.
Funny, have been looking for weeks to find a list of the bmu / charger modifications,
even an overview, but can find nothing. Perhaps you could post a link or two ?...
.
Last edited by syseng68k; 14th Apr 2013 at 21:15.
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Goddamnslacker
Each engine has two generators, so if you depart with one engine generator MEL'd, you have three other engine generators available. Should you lose the APU battery and APU, you still have three engine generators available to provide power. Even if you should lose the engine with two good generators and the APU, you still have one engine generator available and it can carry the load.
A valid scenario...one Engine driven generator inop so as per the MEL permissible to operate supposely ETOPS with the APU running...
Aircraft dispatches...APU Battery fails - APU will shutdown due no APU battery on the APU Hot Batt Bus.
Left with one engine generator supplying the whole aircraft plus a RAT which only supplies limited power….
Aircraft dispatches...APU Battery fails - APU will shutdown due no APU battery on the APU Hot Batt Bus.
Left with one engine generator supplying the whole aircraft plus a RAT which only supplies limited power….
Last edited by Kiskaloo; 16th Apr 2013 at 02:03.
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Even if you should lose the engine with two good generators and the APU, you still have one engine generator available and it can carry the load.
I've seen a statement that the compressors, combined, are the single largest load on the electrical system. I have no CFM output per compressor figure, but I do have a CFM per pax figure. So whether there is extra compressor capacity that would permit reduced input and under what conditions is a question.
I do know that the compressors have to heat their output air to 200*F, and there is supplemental electric heat if necessary, no kw seen for electric heat. This is required by the ozone reversion system to work correctly or adequately. Thus an air-cooling refrigeration plant is required to bring it back to cabin temperature-- no data on the power input to this, but I do know that typically it takes about one-third the energy represented by the heat removed to move it outboard, but I do not know if this system can achieve that.
Some of the larger control surface loads are hydraulically driven. These loads can be of fairly short duration, but of large magnitude-- a Boeing statement there, but no hint at how large. I'd take it to approach the compressor load, depending perhaps on how many surfaces move at once.
It is true that both the alternators and compressors use synchronous motors, which could mean that the power factor in that loop could possibly be adjusted close to 1.0-- meaning one kva generated could supply one kw load, excepting the transformer-rectifier loss in the DC link, and the wiring and motor-controller loss.
I won't add up all the numbers above right now, but I think it's obvious by inspection that one generator (250 kva at the engines, or 225 kva at the APU) will not do it. My considered guess (an engineering term
) is that three generators could do it, that is, I would allow for one of the four remaining to be out. But I am not now sure that Boeing would have allowed that much margin.I continue to be puzzled as the why the APU battery must remain connected after it has started the APU. I have read that sometimes a DC voltage is used as a reference in controlling the AC voltage out on an altenator generator, but I am uncertain as to why this battery must supply that. I will have no time the rest of this week to follow up on this, or to sort and include all the system data I have run down.
I did listen to the NTSB video of the first morning session; nearly at the end, questioning by a board member elicted a comment by a manufacturer's specialist that while there are many examples of sucessful lithium-ion battery applications-- almost all, perhaps all-- are so only after problems found in the field in use were solved. That is, design instructions as to requirements, by the buyers, never quite reflected what the situation in the field turned out to require of the batteries. I'll ask someone over on the Tech side to ferret out that comment in my absence.
OE
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@ OE
My understanding is that safety protections/fire extinguishing etc.. require the APU battery.
... puzzled as the why the APU battery must remain connected after it has started the APU.