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I have just found out Airbus uses aluminium wiring in the A380 to save weight. However, I didn't see anything about whether all the wiring is aluminium, or if copper wiring is also used. What is the logic behind this, and do other aircraft manufacturers do the same? Does Airbus use aluminium wiring in aircraft produced since the A380 was introduced? Are there any risks associated with using aluminium wiring on aircraft?

Juan Jimenez
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huytergan
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  • It's my understanding that most aircraft wiring is aluminum because it weighs less and is almost as conductive as copper. – FreeMan Jun 24 '19 at 14:21
  • Already asked and answered here: https://aviation.stackexchange.com/questions/61510/is-aluminum-electrical-wire-used-on-aircraft/61513#61513 – Therac Jun 24 '19 at 18:17
  • In smaller planes, AL has been used to connect the battery in the tailcone to the starter & other electronics in front of the pilot. That has worked properly for years, with the main thing being to properly terminate the AL in crimped connectors with the proper 'grease' (I don't know what it is) to prevent any galvanic corrosion. My plane has that, built in 1973 and still going strong. – CrossRoads Jun 24 '19 at 21:20
  • These questions are closely related, but they are not duplicate. Instead they appear like "inverse questions" to me. – bogl Jun 25 '19 at 17:33
  • I don't understand how people say these questions are duplicate. I asked more than one question and still didn't get any answer to all of them. For example, "Does airbus use aluminium wiring aircraft produced since the A380 introduced" or "Didnt see anything about whether all the wiring is aluminium or if copper is also used".. – huytergan Jun 26 '19 at 08:22

1 Answers1

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While it is true that copper is 1.6 times more conductive than aluminum per volume,

Conductivity in $\frac{\mathrm{MS}}{\mathrm{m}} = \frac{\mathrm{10^6}}{Ω\,\mathrm{m}}$:

  • copper: 56
  • aluminium: 36 $$\frac{56}{36} = 1.56$$

aluminium is 2.1 times more conductive than copper per weight.

Density in $\frac{\mathrm{g}}{\mathrm{cm^3}}$:

  • copper: 8.96
  • aluminium: 2.7 $$\frac{36 \cdot 8.96}{56 \cdot 2.7} = 2.13$$

Another important metric concerns the cost. The conductivity per cost is 7.1 times higher for aluminium.

Base metal price in $\frac{\mathrm{US$}}{\mathrm{lb}}$ (as of today):

  • copper: 2.71
  • aluminium: 0.81 $$\frac{36 \cdot 8.96 \cdot 2.71}{56 \cdot 2.7 \cdot 0.81} = 7.14$$

Aluminium wiring is safe if it is sized and terminated correctly. In comparison with copper, aluminium is softer, shows more creep, and has 30% stronger thermal expansion.

bogl
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    That's great answer, I appreciate. "use copper where space is limited, and aluminium otherwise" Does that mean copper is usually preffered in fighter jets or UAVs regarding to space? – huytergan Jun 24 '19 at 14:54
  • I don't know much about wiring in fighters. The statement is a theoretical one. In places where the cable concentration is very high, and the harness designer runs out of space, copper might help. – bogl Jun 24 '19 at 15:02
  • @huytergan outside of wiring, it means that landing gears generally use steel alloys where space is at a premium, and aluminium when weight is the main factor and the part can be as large as needed. – AEhere supports Monica Jun 24 '19 at 15:30
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    "There is no risk associated with using aluminium wiring."

    I think you need to expand on that a bit. Aluminium wiring in houses has a very bad reputation (and has been banned for new construction in the US for some time) due to fires caused by gradual growth of oxidization leading to increased resistance at connections. This can be prevented or mitigated but doing so isn't trivial.

     – pericynthion Jun 24 '19 at 15:59
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    One of the factors limiting power transmission in aircraft systems where weight must be minimized is the type of insulation coating the wires. If the wire jacketing can withstand high temperatures, then the size of the wire (for any given conductor material inside it) can be reduced. the increased I-squared-R losses heat the wire more but as long as the jacketing can take it, you're OK. this principle is commonly used in wiring for planes like fighter jets, where the weight of the wiring harness can be reduced by allowing it to run hotter. – niels nielsen Jun 24 '19 at 18:15
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    I'd say there is quite a bit of risk associated with Al wiring. It just can be mitigated by being very thorough with it. For a long time, the rule was Al for thick cables and bus bars, Cu for most cables, as it's much easier to terminate. Only recently has Al been making more inroads. – Therac Jun 24 '19 at 18:18
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    @pericynthion I modified the statement with respect to your comment. I don't know much about the aluminium wiring crisis in the US, but my limited understanding is that due to lack of better knowledge craftsmen installed aluminium as a 1:1 replacement for copper. They didn't account for the additional cross section required and/or using terminals suitable for this material. I don't know if there was a generation of planes that suffered from similar problems, but I am confident that aircraft manufactures learned the rules of aluminium wiring a long time ago. – bogl Jun 24 '19 at 18:29
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    @Therac, yes no doubt. In direct comparison copper is more forgiving, aluminium needs better termination techniques. – bogl Jun 24 '19 at 18:31
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    @pericynthion That's the urban legend, yes. When you look at the facts of the matter, it's actually copper that's the bad actor: copper terminals dislike aluminum wires but everyone else plays nice. Today, service panel lugs are aluminum because they play nice. The 1970s fiasco was due to UL hastily approving small-branch-circuit devices without sufficient testing. It is legal to wire your house today with Al, simply using AA-8000 wire and CO-ALR rated devices.. But no one will buy it, if you do, because ooga-booga. – Harper - Reinstate Monica Jun 24 '19 at 23:48
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    @therac Techniques like using a torque screwdriver on just about everything, and fitting AFCI breakers on most circuits, are now Code for copper wiring, because of a long history of failures that look a lot like the alleged problems with aluminum wiring! – Harper - Reinstate Monica Jun 25 '19 at 00:06
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    If aluminum is 2.1 times more conductive than copper by weight, and also ~3.5 times cheaper by cost-per-weight, shouldn't those stack? Ah, I see it. In the third calc, where did 36 and 56 come from? Since you are multiplying by cost per weight, they should be conductivity per weight. In fact they are conductivity per volume. – Harper - Reinstate Monica Jun 25 '19 at 17:06
  • @Harper, that brings the result to 7.1times cheaper instead of 2.1, if you can agree with the approach. – bogl Jun 25 '19 at 17:27
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    Yes, the approach looks right, and that conforms with my 12:1 back-of-napkin (easily explained by difference in market price) and 3.5-4:1 difference in practical cost of wire (explainable as insulation is a significant factor, in fact on small wires e.g. lighting branch circuits, mineral value pretty much leaves the room; there's little cost savings to aluminum wire for branch circuits). – Harper - Reinstate Monica Jun 25 '19 at 17:41