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Thread: Wire runs

  1. #11
    Senior Member jiott's Avatar
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    Default Re: Wire runs

    Separating wiring from fuel lines-I've always wondered why this seems to be a big deal. What are the odds you will have a fuel leak at the same place and exact time that the wiring shorts out and causes a spark? Seems pretty remote to me. Only in a bad crash might these odds come together. I'm not saying its a bad idea, just personally would not go to too much effort to keep them separated.
    Jim Ott
    Portland, OR
    Kitfox SS7 flying
    Rotax 912ULS

  2. #12
    Senior Member Esser's Avatar
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    Default Re: Wire runs

    In my centre console, the shut off valve is the only union. My fuel pumps are on the other side of the wall so if I had a leaky hose it would suck air not squirt fuel. I do try to keep them as separate as practical but if they are a few inches from each other I’m not worried
    ------------------
    Josh Esser
    Flying SS7
    Rotax 914iS
    AirMaster Prop

    Edmonton, AB, CWL3

  3. #13
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    Default Re: Wire runs

    Jim, for me it has nothing to do with whether there's potential for fire or explosion if you run the electrons with fluids. After all, many larger aircraft have submerged electrically driven fuel pumps. It's simply a preference, and also helps to leave a bit more real estate in the console tunnel area.
    David
    SS7 Builder

  4. #14
    Senior Member jiott's Avatar
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    Default Re: Wire runs

    That reasoning sounds fine with me. I just mentioned it because several others bring it up from time to time and I have always puzzled over it.
    Jim Ott
    Portland, OR
    Kitfox SS7 flying
    Rotax 912ULS

  5. #15
    Senior Member jrevens's Avatar
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    Default Re: Wire runs

    Quote Originally Posted by jiott View Post
    That reasoning sounds fine with me. I just mentioned it because several others bring it up from time to time and I have always puzzled over it.
    Same here, Jim. The important thing in any case is to use good wiring practice as far as properly supporting and securing your wiring so that it doesn't move and rub against other wires and things, and that includes fuel lines.
    John Evens
    Arvada, CO
    Kitfox SS7 N27JE
    EAA Lifetime
    Chap. 43 honorary Lifetime

  6. #16
    Senior Member efwd's Avatar
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    Default Re: Wire runs

    If Im not mistaken, I read that recommendation in the Aero Electric book everyone is reading.
    Eddie

  7. #17
    Senior Member PapuaPilot's Avatar
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    Default Re: Wire runs

    Here is what the FAA has to say in AC43.13.1B. This is the standard for certified aircraft and it would be advisable to do the same with experimental planes too. For me the best way to keep separation from fuel lines and control cables was to run them totally separtated.

    SECTION 8. WIRING INSTALLATION INSPECTION REQUIREMENTS

    11.96:
    (w). Where practical, route electrical wires and cables above fluid lines and provide a 6 inch separation from any flammable liquid, fuel, or oxygen line, fuel tank wall, or other low voltage wiring that enters a fuel tank and requires electrical isolation to prevent an ignition hazard. Where 6 inch spacing cannot practically be provided, a minimum of 2 inches must be maintained between wiring and such lines, related equipment, fuel tank walls and low voltage wiring that enters a fuel tank. Such wiring should be closely clamped and rigidly supported and tied at intervals such that contact between such lines, related equipment, fuel tank walls or other wires, would not occur, assuming a broken wire and a missing wire tie or clamp.

    (dd). Ensure that wires and electrical cables are separated from mechanical control cables. In no instance should wire be able to come closer than 1/2 inch to such controls light hand pressure is applied to wires or controls. In cases where clearance is less than this, adequate support must be provided to prevent chafing.
    Phil Nelson
    A&P-IA, Maintenance Instructor
    KF 5 Outback, Cont. IO-240
    Flying since 2016

  8. #18
    Senior Member jiott's Avatar
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    Default Re: Wire runs

    Well I guess that explains where the recommendation comes from. The "where practical" is the big variable that each builder must decide for himself.
    Jim Ott
    Portland, OR
    Kitfox SS7 flying
    Rotax 912ULS

  9. #19
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    Default Re: Wire runs

    Thanks for the FAA info Phil. I think the reality, as Jim said earlier, that you get a bared wire close to sparking (earthing) and a fuel leak or more specifically, fuel vapour at the same time, the statistic on that is fairly remote. For certain structural failure probabilities, the FAA requires 1 in a million chance of it happening. I'm guessing the FAA requirement for electrical and fuel system proximity requirements is something similar. With proper tie wrapping and ensuring no potential for chafing, I would have thought all ok for running fuel and electrical systems within the same area. My particular routing was simply choice based on sensible routing for my build.
    Last edited by David47; 01-16-2018 at 05:23 AM.
    David
    SS7 Builder

  10. #20
    Senior Member Esser's Avatar
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    Default Re: Wire runs

    What’s the recommend practice for securing uel lines? I’m assuming zip ties are out. Adel clamps?
    ------------------
    Josh Esser
    Flying SS7
    Rotax 914iS
    AirMaster Prop

    Edmonton, AB, CWL3

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