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Topic: 787 Delivery To Air India Snagged By Electrical Pr
Username: voodoo
Posted 2013-07-31 04:06:29 and read 11688 times.

Apologies if this news is already hidden amongst other threads,

http://www.livemint.com/Companies/9O...reamliner-delay-for-Air-India.html

Topic: RE: 787 Delivery To Air India Snagged By Electrical Pr
Username: Speedbored
Posted 2013-07-31 04:18:03 and read 11572 times.

Another power panel failure. Not having much luck with them, are they?

Can't help wondering whether it's a quality control issue (of either the panels themselves or components within), or some part of the design has been under-spec'd and needs beefing up a bit.

Topic: RE: 787 Delivery To Air India Snagged By Electrical Pr
Username: MSYtristar
Posted 2013-07-31 04:46:49 and read 11382 times.

Boeing 787 = Quality you can count on!  

At least this problem came to light before the plane entered revenue service.

Honestly I woke up this morning and figured it's been a few days so we're due to hear about another 787 issue.

Topic: RE: 787 Delivery To Air India Snagged By Electrical Pr
Username: Stitch
Posted 2013-07-31 06:48:33 and read 10837 times.

Quoting Speedbored (Reply 1):
Can't help wondering whether it's a quality control issue (of either the panels themselves or components within), or some part of the design has been under-spec'd and needs beefing up a bit.

Possibly a mix of both.

Topic: RE: 787 Delivery To Air India Snagged By Electrical Pr
Username: s5daw
Posted 2013-07-31 07:01:49 and read 10731 times.

What is so hard about designing a power panel?? What does it do?? Isn't it just a bunch of wires and stuff??

Topic: RE: 787 Delivery To Air India Snagged By Electrical Pr
Username: voodoo
Posted 2013-07-31 07:19:06 and read 10625 times.

Makes me wonder if each issue and its solutions then creates further issues down the line.

Topic: RE: 787 Delivery To Air India Snagged By Electrical Pr
Username: Speedbored
Posted 2013-07-31 07:28:19 and read 10544 times.

Quoting s5daw (Reply 4):
Isn't it just a bunch of wires and stuff??

Yes. It's the 'stuff' that's causing all the trouble.  

Topic: RE: 787 Delivery To Air India Snagged By Electrical Pr
Username: Stitch
Posted 2013-07-31 07:30:55 and read 10522 times.

Quoting s5daw (Reply 4):
What is so hard about designing a power panel?? What does it do?? Isn't it just a bunch of wires and stuff??

The 787 uses electrical power for significantly more functions than previous families of commercial aircraft. The electrical system is therefore significantly more complicated and powerful then the systems on other families of commercial aircraft.

Topic: RE: 787 Delivery To Air India Snagged By Electrical Pr
Username: Speedbored
Posted 2013-07-31 07:39:08 and read 10435 times.

Quoting Stitch (Reply 7):
The electrical system is therefore significantly more complicated and powerful then the systems on other families of commercial aircraft.

And I suspect that it also uses a lot of newer generation components than in previous aircraft. So more solid state switches instead of relays, more switch-mode power conversion instead of transformers, etc. etc.

Although a lot of this technology will have been used in other industries for some time, I suspect that in other places where it's been used before, weight has not been an issue so more margin will have been built in. On aircraft, weight is a big issue so I suspect that many of the components have been sized so that they are operating pretty close to their spec. limits. Maybe too close in some cases.

Topic: RE: 787 Delivery To Air India Snagged By Electrical Pr
Username: JBirdAV8r
Posted 2013-07-31 12:40:01 and read 9095 times.

Quoting s5daw (Reply 4):

What is so hard about designing a power panel?? What does it do?? Isn't it just a bunch of wires and stuff??

Well, a TRU (transformer rectifier unit) is more complicated than that. It converts the AC electrical power from the aircraft's various generators (engine-driven gens, APU, RAT) and converts it to DC power for the systems that need it. All transport-category aircraft that I know of utilize them. Sometimes they go bust. That's the point of a customer acceptance flight--develop a squawk list and have it fixed before taking possession. Think of it as a walk-through with your building contractor before getting the keys to your house.

Topic: RE: 787 Delivery To Air India Snagged By Electrical Pr
Username: PITingres
Posted 2013-07-31 14:53:29 and read 7227 times.

I was intrigued by the comment in the linked article about "electric/electronic systems requiring a dust free environment." My 5 year old desktop Mac Pro will be fascinated to learn that it requires a dust-free environment...

I can only think of a handful of plausible reasons for such a statement, very generously assuming that we discount "bogus" or "ignorant" or "blame diverting":

- metallic dust would obviously be a problem, but I've not heard of any excess metallicity in Indian dust;

- cooling fans and air paths can obviously be blocked by dust, but it's hard to imagine an aircraft power panel being designed to a dustless cooling standard;

- CRT high voltage circuits can attract extra fine dust particles, which are more or less hygroscopic (water attracting), which leads to leakage paths via the humid dust. However we're talking about 10K volts or more; I've no idea what the maximum voltage seen in the 787 power panels is, but I'd be amazed if it were more than 440 volts. I don't know if that is enough to provoke dust-borne humidity leakage problems or not.

Does anyone have factual information in response to the "dust free" claim in the article?

Topic: RE: 787 Delivery To Air India Snagged By Electrical Pr
Username: sankaps
Posted 2013-07-31 15:15:59 and read 6912 times.

Quoting PITingres (Reply 10):
I was intrigued by the comment in the linked article about "electric/electronic systems requiring a dust free environment."

Dust and electronics do not mix well in general (though "dust free" is an unrealistically extreme expectation), but leaving that aside I would discount what government bureaucrats say in that part of the world, they tend to shoot their mouths off.

Reminds me of the early A320 days in India in the late 1980s, when the media was full of reports from "experts" saying highly "computerized" aircraft like the A320 require air-conditioning and therefore were doomed to fail in India.

[Edited 2013-07-31 15:28:38]

Topic: RE: 787 Delivery To Air India Snagged By Electrical Pr
Username: tortugamon
Posted 2013-07-31 15:23:15 and read 6808 times.

The problem has evidently been fixed.

http://flightaware.com/live/flight/B...2/history/20130731/1930Z/KPAE/KMWH

tortugamon

Topic: RE: 787 Delivery To Air India Snagged By Electrical Pr
Username: Speedbored
Posted 2013-07-31 15:31:38 and read 6708 times.

Quoting PITingres (Reply 10):
Does anyone have factual information in response to the "dust free" claim in the article?

Sounds to me like the government safety council spokesman is trying to make the failure sound a bit more serious than it really is.

Electronic circuitry is pretty resistant to the levels of environmental dust that it will come across in normal use. The layer of dust I have in my PC is probably thick enough to peel it off like a sheet of fabric and it's not causing any issues.

After all, normal dry dust is not particularly conductive so it's unlikely to significantly affect anything until considerable amounts of dust accumulate. These power panels are not being left out in the open trailing along in the dust behind the undercarriage; they're in their own enclosures, in enclosed parts of the fuselage. I'm sure it would take a few years before any noticeable amounts of dust accumulate on the circuit boards. And I'm sure that the panels will all run more than warm enough to evaporate off any potential moisture due to the humidity.

Topic: RE: 787 Delivery To Air India Snagged By Electrical Pr
Username: TheRedBaron
Posted 2013-07-31 16:45:49 and read 5983 times.

You know a certain product has real issues when the media can and will identify, failing parts by their name.... guess those P panels ( 100,200 300 and such) will be under big scrutiny by the media.

Now, where is the problem or will they carry a Spare panel "just in case"... as long as Boeing doesnt squat the bugs... they are going to have their hands full....

TRB

Topic: RE: 787 Delivery To Air India Snagged By Electrical Pr
Username: DTW2HYD
Posted 2013-07-31 17:40:46 and read 5451 times.

Quoting JBirdAV8r (Reply 9):
Well, a TRU (transformer rectifier unit) is more complicated than that. It converts the AC electrical power from the aircraft's various generators (engine-driven gens, APU, RAT) and converts it to DC power for the systems that need it. All transport-category aircraft that I know of utilize them. Sometimes they go bust.

Is there a redundant TRU or if it is a SPOF by design what happens to all loads on 28 volt DC. Looking at the Electrical Systems Overview, quite a few loads including Flight Deck Displays are on 28 Vdc.

Topic: RE: 787 Delivery To Air India Snagged By Electrical Pr
Username: JBirdAV8r
Posted 2013-07-31 17:59:30 and read 5291 times.

Quoting DTW2HYD (Reply 15):

Is there a redundant TRU or if it is a SPOF by design what happens to all loads on 28 volt DC. Looking at the Electrical Systems Overview, quite a few loads including Flight Deck Displays are on 28 Vdc.

I can only speak for the airplanes I've flown, but there are always multiple TRUs, nominally responsible for different buses for redundancy. One has five TRUs, the other four.


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