I was just reading about the A380 on Wiki and my eyes bulged out when I saw mentioned "The A380 uses aluminium power cables instead of copper for weight reduction."

Holy crap!

Fact: Aluminum wiring is something that you look for when buying a house. Some cheaply built houses have aluminum wiring since the 60s and 70s, and that is generally a good enough reason to run (not walk) away from the deal.

Fact: Fire on an airplane is even worse than in your house. See SR 111 for an example.

So if aluminum wiring is considered a bad idea for houses, how is it a good idea in an airplane? How many other planes have aluminum wiring?

There’s nothing wrong with aluminum as electrical wiring.

The issue with aluminum wiring in older homes is that the connections were often incorrectly terminated, leading to faults, and a fire hazard. Done correctly, it’s a non-issue. In particular, the alloy using before the early ‘70s had significantly different mechanical and expansion characteristic than what it was often connected to, which lead to things working themselves apart, if not connected correctly to compatible hardware. Newer alloys pretty closely match the properties of copper, and are still legal to use (although between the fairly modest cost differences in small gauges, and the bad reputation, you see very little new aluminum wire in residential applications, although there’s a fair bit in commercial applications).

Aluminum wiring is considerable lighter than copper for a given current, so you often see it in applications where weight is important. Obviously aircraft, but also most of the high-tension distribution lines are aluminum (those long cables are heavy, lightening them cuts down on the number and size of towers you need, plus there’s a lot of metal in those thick cables, with copper being triple the cost of aluminum).

Aluminum was substituted for copper in house wiring when the price of copper increased in the 70's without re-engineering the devices the wires connected to. House fires ensued.

When properly engineered for aluminum in the first place the wiring is fine. High voltage transmission lines have been aluminum for about a century. I suspect the A380 wiring is just fine, even on Qantas.

Quoting rwessel (Reply 1): There’s nothing wrong with aluminum as electrical wiring.

   I think you pretty much nailed it. I would add that aluminum oxide is a problem at the connections. There are numerous products available for cleaning and coating the wire and terminals which make for long term reliable connections.
Thanks,
Cary

The L-1011 also used aluminum for the feeder cables to save weight. Copper was spliced to the aluminum cable for terminations. In my 40 plus years of involvement with the TriStar I have never heard of the aluminum cables causing a problem.

Quoting aklrno (Reply 2): even on Qantas.

this just made me LOL

never heard of aluminium wiring before. but airbus must have had a good reason to use it.

Quoting horstroad (Reply 6): never heard of aluminium wiring before. but airbus must have had a good reason to use it.

Because its' use for over 40 years in the TriStar has proven it works.

Quoting Dreadnought (Thread starter): So if aluminum wiring is considered a bad idea for houses, how is it a good idea in an airplane?

Because the way it's installed in airplanes it works very well, the way it was originally installed in houses it worked terribly. Same reason that building an airplane out of aluminum or cfrp is a great idea but building a house out of it is a terrible idea.

Quoting Dreadnought (Thread starter): How many other planes have aluminum wiring?

I would bet big money that everything in production today is using at least some aluminum wiring.

Tom.

Disadvantages of aluminium (over copper).
- It has a considerable higher electrical specific resistance, which means that for the same current the wire diameter must be larger, to keep loss in check.

http://en.wikipedia.org/wiki/Electrical_resistivity_and_conductivity

- It immediately forms a protective alluminium oxide layer in contact with air. This layer is a bad conductor which is the cause of the connection problems.

Advantages
- Cheaper and lower density

Wherever the advantages outweigh the disadvantages aluminium is used. For the same reason silver and gold are used for certain applications
- Silver because it is the best conductor on earth but is expensive (Microvave components).
- Gold because it does not corrode so it makes excellent connections but is very expensive (Micrchips)

Aluminium wiring is only used for wire Gages 6 and larger.

Even if a larger gage aluminum wire (Gage 4) was required in lieu of Gage 6 copper the weight savings for 100 feet of wire would be sufficient, 3.8 lbs for aluminum vs 11.1 lbs for copper.

I know there have been some fires on Pipers that started due to aluminum wiring. Apparently it's popular to replace the wires with copper.

Copper is a better conductor & heavy whereas Aluminium is a bit less better than copper but is lighter,something that can save valuable weight on an Aircraft is welcome.

Probably Gold would be the among the best corrosion resistant....So make an entire Airplane out of it......I wonder why no one did this  

Quoting kalvado (Reply 9): As a matter of fact, internal chip wiring switched from aluminum to copper a few years ago. gold is only used as contact pad plating.

I am afraid that this is not the case. Aluminium, copper, as well as gold are/were used as bonding wire in microchips. It all depends on the price of the chip. The decision which metal to use is based on the same criteria. That's for instance the reason why aluminum is generally not used for high power semiconductors since the required thicker wire is hard to do within a limited space.

http://en.wikipedia.org/wiki/Wire_bonding

The aluminium connection problem is not an issue in microchips because the wire is welded onto the pin contrary to electrical wiring in buildings which is just fixed by a screw in a terminal. I don't know much about aircraft but I assume they use similar techniques to make a proper aluminium connections in the aviation industry.

Quoting YokoTsuno (Reply 13): I don't know much about aircraft but I assume they use similar techniques to make a proper aluminium connections in the aviation industry.

Copper cable is spliced on the ends of the aluminum cable just prior to the terminations.

Quoting 474218 (Reply 14): Copper cable is spliced on the ends of the aluminum cable just prior to the terminations.

Is this done by crimping a short length of copper wire onto the aluminium wire? Basically like in cars, or in electronics equipment.

http://autorepair.about.com/od/fixityourself/ss/wiring_basics_3.htm

Quoting YokoTsuno (Reply 15): Is this done by crimping a short length of copper wire onto the aluminium wire? Basically like in cars, or in electronics equipment.

I am not sure, but since we are talking wires that are up to 1/4" in diameter I don't think they make crimp sleeves that large!

Quoting aklrno (Reply 2): even on Qantas

   Nice one!

gibbo

Quoting YokoTsuno (Reply 8): - It has a considerable higher electrical specific resistance, which means that for the same current the wire diameter must be larger, to keep loss in check.

Al has about 67% higher resistance than Cu, but is 3.3 times less dense, which basically means you halve the required mass of the conductors. At current raw metal prices, that's something like a six-fold decrease in cost for the conductors in Al wires (Cu is unusually expensive right now, in historical terms it's more like three times, and for small gauge wires, stuff besides the conductor adds substantial cost).

Quoting YokoTsuno (Reply 8): - It immediately forms a protective alluminium oxide layer in contact with air. This layer is a bad conductor which is the cause of the connection problems.

Unless the wire was not cleaned before installation, the oxide layer is very thin (a few nm), and is not really an issue in most power distribution situations. In any event, a proper mechanical connection will punch right through it. Even if not, it's so thin that the net resistance is negligible.

The major issue is different coefficients of expansion in the Al wire and the copper devices attached to it. The repeated heating from current flow tends to work the connections loose, which leads to arcing, and a fire hazard. For hardware designed for the connection, it's a non-issue.

Quoting kalvado (Reply 9): As a matter of fact, internal chip wiring switched from aluminum to copper a few years ago. gold is only used as contact pad plating.

The lower levels of wire on high end chips on the smallest processes, true. But the vast majority of Si semiconductors are still manufactured with just Al and poly “wires.” Cu is a huge PITA to work with, Cu atoms leach into the semiconductor substrate and wreak it. You have to put a near-perfect barrier layer between the Cu and Si, which adds considerable complexity to the manufacturing process.

Quoting YokoTsuno (Reply 13): The aluminium connection problem is not an issue in microchips because the wire is welded onto the pin contrary to electrical wiring in buildings which is just fixed by a screw in a terminal. I don't know much about aircraft but I assume they use similar techniques to make a proper aluminium connections in the aviation industry.

Terminals, pins and splices are usually crimped connections. For aluminium wires there exist special terminals, which contain an abrasive paste, which, during the crimping process, removes the oxide layer on the surface so that there will be a direct metal to metal contact. The crimping is being done with regularly calibrated tools (which are quite expensive) to ensure that there is the correct pressure being applied. Such a crimping connection properly made is stronger than the wire itself. For bigger wire diametres (e.g. for generator feeder cables, wire size 0 - 0000 AWG) the crimping tools are hydraulically operated.
For aluminium/copper connections there exists special splices, which prevent dissimilar metal corrosion issues.
BTW, both the Boeing 747-400 and the MD-11 use aluminium wires as generator feeders inside the fuselage. I never had a problem with those wires.

Jan

Quoting MD11Engineer (Reply 20):

Thanks. That's a clear explanation.

Sigh. It appears that some posting on here never read the old threads on the Airbus "aluminium" wiring, or did not understand what was written.

A380 Not State Of The Art-Due 2 Aluminum Wiring? (by Coelacanth Oct 22 2006 in Civil Aviation)?threadid=3056107&searchid=3062099&s=ElGreco#ID3062099
This is not the post I was looking for, but it will suffice I think.

ElGreco From France, joined exactly 6 years ago today! , 164 posts, RR: 1
Reply 7, posted Mon Oct 23 2006 12:11:22 your local time (5 years 2 weeks 1 day 12 hours ago) and read 10683 times:

Good afternoon everybody,

I had already answer few times about these questions on aluminium cable technology on A380, but I will do it again with pleasure.

1) few pure aluminium cables are used by Airbus, Boeing, Bombardier,... for years on feeders for power cables to save weight (from A320 for Airbus).

2) A380 is the first plane in the world to use that technology for smaller cables (e.i.: up to #22 contact with #24 cables) but we used aluminium/cooper cable with nickel plated, and not pure aluminium cable (e.i.: each wire is aluminium with 10µ of cooper around and 2µ of nickel deposit).

3) contacts are in copper with nickel and gold plating (as for copper technology) but with longer design to be crimped on the cable and on the insulation cable as well. Furthermore, a ferule is installed in the contact as interface between cable and contact.

4) this technology is based on patent made in 1965, and we are working on that technology from 1967, as many others companies).

5) This technology have been choose in 2002 by Airbus and qualify in 2003. Weight saving is closed from 500kg per A380, it's used on A400M and it will be use as well on A350XWB.

In conclusion don't worry be happy.

El Greco

IIRC El Greco had something to do with making/designing the wiring. Somewhere I think you will find he told us that the Al and Cu are co-extruded and then Ni Plated.

If you want to think that Al with copper, nickel and gold plating is vanilla style Aluminium, well that is fine, but it ain't.

[Edited 2011-11-06 05:40:30]

Quoting MD11Engineer (Reply 20): For aluminium/copper connections there exists special splices, which prevent dissimilar metal corrosion issues

I remember that the L-1011 had these splices in the MESC ceiling ....They were clearly marked "Cu/Al special splice" with placards.

Quoting Baroque (Reply 22): 2) A380 is the first plane in the world to use that technology for smaller cables (e.i.: up to #22 contact with #24 cables) but we used aluminium/cooper cable with nickel plated, and not pure aluminium cable (e.i.: each wire is aluminium with 10µ of cooper around and 2µ of nickel deposit).

Thanks for the link. I had this feeling that methods like that could have been used. Amazing, in very old houses and buildings here you see copper wire with rubber insulation instead of the plastic used today. This copper was plated with tin, I believe to prevent the chemicals in the rubber from reacting with the copper.

Quoting Baroque (Reply 22): I had already answer few times about these questions on aluminium cable technology on A380, but I will do it again with pleasure.

The poor guy has given up this time. This is what you get when you abuse people   A.net should do something about the search engine.

Quoting YokoTsuno (Reply 24): The poor guy has given up this time.

ElGreco was a really nice guy and patient as well as being knowledgeable. Re the search engine you are dead right. The system needs to be able to search by, for example ElGreco AND A380 wiring. I know I am hopeless with the system but it gave me quite a run for my money before I found that thread. And I am near positive there was a preceding one that was better.

Another in that thread who is sorely missed is RichardPrice, although he might be lurking, he was a few years ago. Also Halibut.

Also worth - as usual - a (re)read is the Lightsaber post, reply 42 on aircraft wiring in general.

Quoting YokoTsuno (Reply 24): This copper was plated with tin, I believe to prevent the chemicals in the rubber from reacting with the copper.

I think they spend some considerable time first to develop the general plan of the coated Al wiring, and even more on how to produce it at a reasonable cost.

Whatever the reasons were for the Al wiring, A chose that system when copper was something like USD3000 a tonne and it has been over USD9000 a tonne for most of the past couple of years. So aside from the weight, which was their first aim, even allowing for production costs, they much have a nice little saving in materials costs by now with the whale.

Quoting 474218 (Reply 16): I am not sure, but since we are talking wires that are up to 1/4" in diameter I don't think they make crimp sleeves that large!

Go take a look at the battery cables in your car ... 1/4" or larger, and crimped connectors ... if you have an older car that's had cable repairs (due to acid damage), you probably even have some butt connector sleeves crimped on there, too, to restore proper wire length.

Quoting litz (Reply 26): Go take a look at the battery cables in your car ... 1/4" or larger, and crimped connectors ... if you have an older car that's had cable repairs (due to acid damage), you probably even have some butt connector sleeves crimped on there, too, to restore proper wire length.

How old does this car have to be? I have a 1966 Dodge Coronet and 1969 Plymouth Road Runner and I have not seen a crimped connector on either of them! But then I take better care of them than most airline do their airplanes!

Quoting 474218 (Reply 16): I am not sure, but since we are talking wires that are up to 1/4" in diameter I don't think they make crimp sleeves that large!

A few weeks ago we had to make a main bonding jumper for the APU of a 747-400. We used 0000AWG crimped terminals.
Check SAE AS7928 and SAE AS 81824 for the standards. A good description is also given in the FAA Aviation Circular AC21-99 Aircraft Wiring and Bonding, especially in Section 2 Chapter 6.

Jan

I've done Aluminium large Gauge splices on feeder cables in Boeing 757s many times before so using aluminium cables isn't new to Airbus or aircraft in general. You need a huge hydraulic hand pump to crimp the splices.

I have no doubt though using aluminium for the small gauge wires will turn into a maintenance nightmare in the later life of the A380 with all sorts of niggles caused by oxidisation at joints and connections. Time will tell.

Quoting 767eng (Reply 29): I have no doubt though using aluminium for the small gauge wires will turn into a maintenance nightmare in the later life of the A380 with all sorts of niggles caused by oxidisation at joints and connections. Time will tell.

Time will tell, but how do you suppose the oxidation will get through the copper co-extrusion and the nickel plating?

Wear and tear my old friend , I've yet to see any form of aircraft wiring that isn't affected by time and intervention defects.

I could be proved wrong, who knows. Hopefully for my jobs sake they will continue to go wrong.

Quoting Baroque (Reply 30): Quoting 767eng (Reply 29): I have no doubt though using aluminium for the small gauge wires will turn into a maintenance nightmare in the later life of the A380 with all sorts of niggles caused by oxidisation at joints and connections. Time will tell. Time will tell, but how do you suppose the oxidation will get through the copper co-extrusion and the nickel plating?

Cracks and damage to the plating, especially, where the insulation has been removed where the wire is being inserted into the crimped terminals. If you add a little moisture, you´ll have the same effect as with tin plated steel. As long as the coating is intact, there won´t be problems, but as soon as the coating gets damaged, there will be electrolytic oxydation of the core material (aluminium).
Also most standard terminals (pins) are gold or nickel plated, all of them nobler than aluminium.

Jan

Quoting MD11Engineer (Reply 32): Cracks and damage to the plating, especially, where the insulation has been removed where the wire is being inserted into the crimped terminals.

Hmmm. Tin plate is a bit special - if it goes slightly off spec you get structures through which chemical reactions can take place. You happen to have referred to something I did once - for some strange reason - work on. The effects of drought affected mutton on tin plate as opposed to those of well-fed mutton!!! And believe it or not, there is a big difference and much more amazing we figured out what the problem was!

I don't work these days with a bunch of crazy metallurgists, but the properties of the co-extruded copper will presumably have been controlled to try to prevent crack development and they are putting the Ni plating on for some reason. Wish ElGreco was here to tell us. They worked on it for a coon's age before putting it in planes.

[quote=rwessel,reply=1]you see very little new aluminum wire in residential applications, although there’s a fair bit in commercial applications).


From the service entrance panel to the house wiring, that's correct; but from the pole transformer to the service entrance panel, it's almost all aluminum.

Aluminum is not quite as good of a conductor as is copper, so it requires a slightly heavier gauge to conduct the same current. Aluminum's big fault is it's propensity to combine with oxygen, (causing oxidation), which impedes current flow, and also it's differing expansion characteristics, which can cause loose connections over time.

All of these problems have been taken care of quite well with modern technology; aluminum service entrance conductors (all of which are quite large as compared to the wiring in the house) are terminated with special connectors, which contain a black anti-oxidation paste, and the connector is "crimped" on, using a very heavy duty, (and expensive) mechanical device. No bare aluminum is left exposed to the air.

Think about this.........who works on or ever comes in contact with the heavy service entrance conductors from the house to the pole ? Either people from the power company, or an electrical contractor, both of whom "know what they are doing", how to do it properly and safely, and have the proper tools and equipment to do what needs to be done.

Next........from the service entrance panel on into the house wiring..........who "works" on that ? The answer of course is.......just about EVERYONE; ( many of whom have very little ( if any ) knowledge of electricity, but who possibly just bought a "how to" book at Home Depot, and are going to "save" a ton of money by putting in than new electric stove or dryer for the "old lady", by not getting a qualified electrician to do the job.

Back in the 60's and 70's there was a lot of this going on; aluminum wiring was being installed with switches, connectors, etc. which were made to be used with copper wire. It worked "kinda" for a short time, and then the firefighters started getting a lot more calls.

I'm very confident that Airbus Industries has installed their aluminum wiring using the appropriate connecting devices, and I'm pretty sure they do in fact "know what they are doing". So I really don't think the fact that the A 380 uses aluminum in it's wiring, is any cause for concern. ( And I'm a BIG Boeing "fan" ! )

One more thing............I recently sold a house in Ohio that I lived in for over 50 years, and in cleaning the place up, I happened to take several hundred pounds of scrap copper plumbing, 4 or 5 old air conditioners, and a bunch of old copper wire to a scrap yard; they have a whole bunch of prices, depending on grades, etc. but I got around $ 3.50 a pound for No.1 grade copper. Copper is EXPENSIVE ! So I think you will be seeing more rather than less aluminum wiring in the future.

Charley