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Old 28th Feb 2013, 08:48   #1061 (permalink)
 
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Walnut
Quote:
I note that the a/c needs 2 GPUs to provide engine starting, I have been to numerous outstations where you are lucky to get even one doubtful unit.
I believe this is one reason that the APU can be started by either battery or ground power. The APU can then start the engines, one at a time.
If there is no fuel on board for the APU, the main battery will power the fuel transfer system to allow fuel to be added and made available to the APU.
Quote:
... but again the pilot is faced with pressurisation problems...
I also believe that since pressurization is provided by electrically powered compressors rather than air bleed, minimal cabin pressurization can be powered from the APU or even just the RAT.
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Old 28th Feb 2013, 09:00   #1062 (permalink)
 
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The RAT has absoulutely nothing to do with pressurizing the aircraft. It simply does not have the capability to power the CACs and thus is limited to only the most essential items needed such as hydraulics and flight instruments.

Last edited by Spooky 2; 28th Feb 2013 at 10:35.
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Old 28th Feb 2013, 09:03   #1063 (permalink)
 
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My greater concern is not that these batteries catch fire, but that they fail! On a fly-by-wire aircraft, that gives a whole new meaning to the term "dead stick". Yes, I know almost everything else has to fail before this matters. But consider Sully's celebrated ditching:

He lost both engines. His APU was not running. If his batteries had failed, and his aircraft had been a 787, he would have had no flight controls. At all.
The 787 also has individual back up batteries for the three ACEs (Actuator Control Electronics-part of the fly by wire system) they are also Li-Ion. The 777 is similar.

Quote:
I note that the a/c needs 2 GPUs to provide engine starting, I have been to numerous outstations where you are lucky to get even one doubtful unit.
Boeing have said this a/c is a game changer, I agree, but it is very complex, and as such I can see lots of down line problems.
It's worse than that. Two GPUs is the absolute minimum-engine start cycle can be up to 3 mins due to the lack of power.
For optimum engine starting a third GPU is required-plugged in at the aft EE bay area.

As has been said, getting two 90Kva GPU supplies is hard enough, but three? FORGET IT!
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Old 28th Feb 2013, 09:39   #1064 (permalink)
 
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Have there been many (any?) total electrical power failures that haven't been caused by loss of the engines too? I can't think of any.
Qantas 747's galley leak caused system failure: ATSB report
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Old 28th Feb 2013, 11:17   #1065 (permalink)
 
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Not a total electric failure though. Three of four.

Close but no cigar.
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Old 28th Feb 2013, 11:24   #1066 (permalink)
 
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Hi Turin

B777 is the only type I can think of with a pneumatic starter (in addition to electric).
Are there others? A380 perhaps?

A380 has no pneumatic starter. No other aircraft I know of has one.


Have there been many (any?) total electrical power failures that haven't been caused by loss of the engines too? I can't think of any.

Only major failure when all power was lost on B787 was in the Loerdo incident, when there was a total loss of power and the RAT deployed. As they were on approach at that time they continued in that condition. Details of that incident are sketchy. There was a major fire in the central Electronics bay, where all power panels are located. I don't think NTSB got involved as the aircraft was still in the test phase. The reason for the power loss and fire according to Boeing was FOD !!!
Then there was the United incident and diversion to New Orleans, where power loss from one Gen was not properly restored from the other good generators. When you have 6 Gens loss of one Gen should be a piece of cake. Again the details are sketchy.
The same problem occurred again on a new Qatar B787 after delivery flight. The details are once again limited. the out burst of it's Chairman against Boeing is well documented.
Boeing has mentioned that these problems are now sorted out.

During my time in aviation there were some incidents of total power loss on different aircraft, but did not result in any accident. In one instance the aircraft was B777 that was dispatched with one gen inoperative, and other side engine failed for an unconnected reason. But as the APU was already running, power was automatically restored.
One remarkable incident was on a A300-600, belonging to a charter airline, that was positioning to an MRO. It was dispatched with one Gen inoperative from far east and when over India the other Gen also failed. The flight continued all the way to France with just APU. It was a ferry with just 2 crew. Still it was remarkable that the crew had faith on the APU for 6-7 hours. When I met the crew after landing, both Mexican, I had to tell them that they were bravest crew I have ever met to have faith in the APU for 7 hours.
On airbus there is detector called Avionic smoke Detector, which can trigger a warning (Most instance false), the crew have to kill most of the power and land ASAP. This has happened several times, a recent one is on Air Canada 320 at Edmonton.
Incident: Air Canada A320 near Edmonton on Aug 18th 2012, avionics smoke indication
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Old 28th Feb 2013, 11:49   #1067 (permalink)
 
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Airbus knows when it potentially has a tool to beat its competitor over the head with. Not in an overt way mind you - there will be subtle reminders...
Leahy already jumped on it, in a not so subtle way (quoting from CONF iture's link):

When Airbus redesigned the A350 seven years ago to create the all-new XWB, Leahy admits that he pushed the engineers to follow Boeing's lead on all-electric architecture. But he is pleased he was overruled. Airbus engineers went "back and forth" three times about whether to equip the XWB with electric brakes before deciding to stick with conventional hydraulic architecture. "I'm guilty as the commercial guy for pounding the table saying 'look [the 787's] all-electric - it's game-changing'," Leahy admits. But trade-off studies by Airbus engineers could not justify adopting the technology. Leahy says: "They told me: 'You're not going to like the reliability - it's going to be complex, heavy, and hard to maintain'."

Last edited by deptrai; 28th Feb 2013 at 11:49.
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Old 28th Feb 2013, 12:32   #1068 (permalink)
 
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Walnut

Quote:
I see the flying controls have 3 hydraulic systems, with the centre electrically powered, so with a double engine failure it is essential to start the APU, (from the battery)?

My original post was just to high light how Boeing are in a pickle by doing away with engine bleed. Though a bit old fashioned, engine bleed was reliable power source. Without bleed we need huge power source from generators and batteries etc, and has actually created a problem on basic electric systems which normally do not have any serious problem on most aircraft these days.

Last edited by Hi_Tech; 28th Feb 2013 at 12:36. Reason: Typos
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Old 28th Feb 2013, 13:01   #1069 (permalink)
 
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Quote:
engine bleed was reliable power source
Engine bleed is expensive to maintain, leaks are common and potentially dangerous. Interflug lost an Il-62 due to a bleed air leak causing a fire.
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Old 28th Feb 2013, 13:19   #1070 (permalink)
 
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The Interflug Il-62 crashed back then because of a leaky bleed air pipe crossing the little known cargo compartment between the engines burned through insulation and some electrical wiring which ignited some barrel of deicing fluid that was carried there (not permitted per regs). And all that led to a fire, loss of control, inflight breakup and loss of all lives.
The type received modifications afterwards.

ASN Aircraft accident Ilyushin 62 DM-SEA Knigs Wusterhausen

Last edited by Kerosene Kraut; 28th Feb 2013 at 14:54.
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Old 28th Feb 2013, 13:28   #1071 (permalink)
 
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Agree

Quote:
The RAT has absoulutely nothing to do with pressurizing the aircraft. It simply does not have the capability to power the CACs
It is like attempting to start your car with two AA batteries.
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Old 28th Feb 2013, 13:34   #1072 (permalink)
 
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Engine bleed is expensive to maintain,
Only time will tell how expensive these CACs and power conversion equipment are to maintain.
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Old 28th Feb 2013, 15:23   #1073 (permalink)
 
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Kiskaloo,

Agreed, in that Boeing don't design batteries. They would have looked at the energy density values and at the design stage, Lithium-Ion would have been a no-brainer.

Yuasa's expertise in battery design is beyond reproach, however at this moment it's uncertain what caused the battery pack to ignite. While it may have been a faulty battery, we don't know if the cell spacing exacerbated the problem or if the charge/discharge algorithms were faulty or if it was an as yet unknown factor.

What is clear is that Boeing pretty much went all in on 'Electric plane' concept and this made the Lithium battery a commitment rather than a contribution.

I'm still slightly surprised that there were no indications of potential battery problems during the testing/flight testing regime, these normally take each system to the edge of the envelope, yet no issues reported?
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Old 28th Feb 2013, 16:08   #1074 (permalink)
 
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Quote:
Kiskaloo,

Agreed, in that Boeing don't design batteries. They would have looked at the energy density values and at the design stage, Lithium-Ion would have been a no-brainer.

Yuasa's expertise in battery design is beyond reproach, however at this moment it's uncertain what caused the battery pack to ignite. While it may have been a faulty battery, we don't know if the cell spacing exacerbated the problem or if the charge/discharge algorithms were faulty or if it was an as yet unknown factor.

What is clear is that Boeing pretty much went all in on 'Electric plane' concept and this made the Lithium battery a commitment rather than a contribution.

I'm still slightly surprised that there were no indications of potential battery problems during the testing/flight testing regime, these normally take each system to the edge of the envelope, yet no issues reported?
Hang on a minute shouldn't the design be "Fail Safe"? I wouldn't fancy flying 8 hours with a fire in the cabin. Just redesign the battery.
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Old 28th Feb 2013, 16:14   #1075 (permalink)
 
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I'm still slightly surprised that there were no indications of potential battery problems during the testing/flight testing regime, these normally take each system to the edge of the envelope, yet no issues reported?
Business & Technology | Electrical fire forces emergency landing of 787 test plane | Seattle Times Newspaper You been asleep for a few months? How on Earth did it get certified when a test A/C burst into flames?
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Old 28th Feb 2013, 16:29   #1076 (permalink)
 
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Have there been many (any?) total electrical power failures that haven't been caused by loss of the engines too? I can't think of any.
Qantas B744 Total electrical failure? [Archive] - PPRuNe Forums

The 747-400s APU cannot be started inflight, apparently as failure of all 4 gens was thought impossible.
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Old 28th Feb 2013, 18:40   #1077 (permalink)
 
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Business & Technology | Electrical fire forces emergency landing of 787 test plane | Seattle Times Newspaper You been asleep for a few months? How on Earth did it get certified when a test A/C burst into flames?
Was the actual cause of that fire during test ever released? Was it perhaps a battery incident???
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Old 28th Feb 2013, 19:32   #1078 (permalink)
 
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Ex Cargo Clown, inetdog

As it was a test flight, the incident has not been logged by the NTSB : List by Month
Therefore, no "official" report has been established by an independent body.
"Common" knowledge is that some FOD made its way in the aft electric panel and the whole thing burned down !
Flightblogger published a quite comprehensive summary of that incident No split over similar-looking wingtips - FlightBlogger - Aviation News, Commentary and Analysis
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Old 28th Feb 2013, 20:24   #1079 (permalink)
 
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Do you have any references for that, toffeez.
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Old 28th Feb 2013, 20:37   #1080 (permalink)
 
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glad rag

Just type "like Radio Shack" in the Seattle Times search engine and you'll get the source
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