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Power Wiring for Avionics -- Shielded?

1001001

Well Known Member
I'm working on writing up a wiring schedule for the purpose of buying multiconductor and shielded cables. Reading through various installation manuals I see many signal cables with shields, which I would expect to see.

I would also expect to see shields on power wiring for some items, but they're not called out...for instance the GSA 28 autopilot servos don't show shields on their power/ground wiring.

I know there are recommendations out there for shielding certain types of wiring like strobes and that wiring in the vicinity of, e.g., magnetometers should be shielded.

Are there general recommendations for shielding power wiring to devices? I'm not seeing them in AC43-13, but may be missing them.

I do intend to return power ground wires back to a common ground bus, or in some cases a local ground terminal block that is in turn gorunded to the main ground bus. Should these be shielded?

I've also seen some recommedations for using twisted pairs for power wiring running near sensitive devices.


Are there some solid best practices out there that people can recommend? I don't want to add weight unnecessarily, but don't want to have to revisit wiring once it's pulled, either.
 
Wiring

If my memory serves me correctly:
1. purchase Bob Nuchols book on A/C wiring practices.
2. I wired my RV7 grounds to a common buss on firewall.
3. to prevent "ground loops", I only grounded 1 end of shielded wires.
4. keep "pigtails" for shield as short as practical with a stress loop.
5. I can't stress enough the need to draw all wiring diagrams and follow the diagram.
6. Invest in a power supply (120V primary to 12Volt output) to allow checking operation even before connecting to aircraft battery.
7. Take your time and enjoy the journey...;)
 
I'm working on writing up a wiring schedule for the purpose of buying multiconductor and shielded cables. Reading through various installation manuals I see many signal cables with shields, which I would expect to see.

I would also expect to see shields on power wiring for some items, but they're not called out...for instance the GSA 28 autopilot servos don't show shields on their power/ground wiring.

I know there are recommendations out there for shielding certain types of wiring like strobes and that wiring in the vicinity of, e.g., magnetometers should be shielded.

Are there general recommendations for shielding power wiring to devices? I'm not seeing them in AC43-13, but may be missing them.

I do intend to return power ground wires back to a common ground bus, or in some cases a local ground terminal block that is in turn gorunded to the main ground bus. Should these be shielded?

I've also seen some recommedations for using twisted pairs for power wiring running near sensitive devices.


Are there some solid best practices out there that people can recommend? I don't want to add weight unnecessarily, but don't want to have to revisit wiring once it's pulled, either.

Two planes with standard wire for ALL power connections and most high draw devices used a frame ground. Did wired grounds for all avionics. Anything behind the panel got wired grounds and everything else go frame ground. Zero noise on the 10 and only the faintest of noise from the old school strobes on the 6, though highly doubt that is coming from the input power wire. I did use shielded wire for the supply to strobe connection, as I expected that to be a bit noisy.

Larry
 
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I am only an electrical installer, not a designer, very similar for most Vans builders. I followed the Dynon wiring diagram with regard to the shielding and only used the shielded wires called out in the diagram. I realize adding extra unneeded shielded wiring carry a good amount of weight penalty for the longer wire runs, and extra installation time.

For the non-avionic related wiring, I referenced Bob Nuckols books and add shielded wiring to the magnetos. Being an installer, I do ohm checking and create wiring pigtails to check for power once the wiring are completed and "hope" for the best. I know some in the forum thinks "hope" is a four-letter word but I hope my plane holds together, and my piloting skill won't make me a statistic.
 
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