Aluminum Wiring 1

[swall]

A retired engineer friend of mine had worked for an aerospace component/systems supplier and mentioned one program where the device was over the intended design weight. One solution contemplated was changing the wiring from copper to aluminum. This seemed like a bad idea to me and I was wondering if aluminum wiring is used in any aircraft applications?

 

[thruthefence]

Piper Aircraft used aluminum wiring in a ton of models, back in the 1970's. Primarily in the larger power wiring, battery to Buss, Ground & starter cables, & so forth. Piper SB836A required inspection & replacement, but apparently it wasn't serious enough to warrant an Airworthiness Directive. I think there were a couple of fires blamed on the aluminum wiring. These aircraft (with aluminum wiring) were notoriously "slow starters"; poor terminations & corrosion, I suppose. This went away with the new copper cables.

 

[MiketheEngineer]

They quit using AL in houses years ago... Any guess why?? I didn't work and caused fires, poor connections, etc.

 

[IRstuff]

Actually, most integrated circuits up to about 5-10 yrs ago were all wired with Al-Si inside. I haven't kept up, so I don't know if the bottom layers of metallization are still the same.

TTFN
faq731-376

 

[kontiki99]

Most large commercial jets I've seen have CU gen feeds and at power panel and CU-AL splices to AL wire that runs the length of the fuselage. Likewise to APU electric starters. This is only big 000Ga wire runs.

In theory, there is no difference between theory and practice; experience suggests that in practice, there is.

 

[WKTaylor]

Per AS50881 D Wiring - Aerospace Vehicle

3.8.2 Aluminum Wire
The use of aluminum wire requires procuring activity approval. Aluminum wire shall be restricted to size 8 and larger. Aluminum wire shall neither be directly attached to engine mounted accessories nor installed in other areas of severe vibration. It shall not be installed where frequent connections and disconnections are required. All installations of aluminum wire shall be relatively permanent. Aluminum wire shall not be used where the length of run is less than 3 feet, nor in areas where corrosive fumes exist. Aluminum wire shall be terminated only by terminations specifically approved for this application (see 3.20.2).

There are also aluminum-wire electrical bonding jumpers for permanent [non-flexing] installations.

The major concerns for aluminum wires are: poor resistance to corrosion [including light oxidation], especialy at terminations; and intolerance of flexture or any strain reversals [any reason including due to vibrations, structural deformations and thermal expansion and contraction] which can easily crack/break wires.. or strain/distort connectors.

Copper is much tougher and longer-lasting, especially with tin or nickel plating.

NOTE.

Aluminum-wire electrical bonding jumpers are required to undergo pull-tests [for end terminal security] and ~10-full bend flex cycles.

Copper-wire electrical bonding jumpers are required to undergo pull-tests [for end terminal security] and ~100,000-full bend flex cycles.


Regards, Wil Taylor

Trust - But Verify!

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[swall]

Excellent information. Thank you, Wil.

 

[DHambley]

Swall, To answer your question, aluminum is indeed used still today in aircraft. The main ships transformers in the new Boeing 787 for example, use Al because it's conductance to weight ratio is better than that of Cu.