Wire runs

[Flybyjim]

I am looking at my plane today working on the wire runs for the strobes/landing lights/neg/pos wires. Where did you find the best place to have connections/disconnect plugs. Did you run all wiring through the center of the fuselage or up the side panels. These are things I did not note when looking at others planes.

[Esser]

I went in the centre. I dont think the sides would work as well. For how often I will never take off my wings, I’m not putting plugs but if I did, it would be at the wing root. Instead I’m putting plugs at the wing tips. If I ever need to remove a wing ill pull the wire all the way out from the wing tip.

[Floog]

Unlike many, I ran my fuel line through the center between the seats. I ran the wing wiring cables down center as well but on the floor. Which brings up the main point: keep wires away from fuel lines as much as possible. I put connectors behind the seat (only because the cables weren't long enough to make the run all the way to the panel😣). Might come in handy some day......

[Floog]

Disregard the &#128457 butt entry?????

[jmodguy]

I ran all my wiring through the center of the fuselage and up behind the seats. Running them under the door made me think they would be easier to damage and or chafe.
For the wings and wingtips, since they are easily removable, I installed DB9 connectors (computer type 9 pin) at the root and at the wingtip. These connectors are used in many aviation electrical connections both civil and military with very good reliability.
I also installed a 3/8" thinwall plastic tube in the wing to act as a conduit for the wiring. You can get the tubing at the aviation aisle in Lowes/Home Depot/Menards etc.

Edit
I also ran my fuel/ lines through the center console along with duplex valve, fuel pumps, filters, and flow sensors. See pics in my Album.
Lots of room under the center console.

[PapuaPilot]

I avoided going down the middle bottom of the plane to avoid the fuel lines, flap and elevator controls. Starting from the backside of the panel most of my wiring goes to the right, down to the floor and aft under the doors. Then the wing wires go up the rear door post and into the wing spars. The left wing wiring goes to the left side of the panel and followed a similar route. I made channels to hold the wing wiring that I mounted to the front of the aft triangle windows, I didn't want to run the wing wires on the angle tube along with the fuel hoses.

I also chose not to put plugs at the wing root as it can readily be disconnected at the wingtips and pulled out. I used the black plastic sheathing inside the spars and in any other area where protections from rubbing could occur.

[jiott]

My wiring runs thru the center between the seats in some aluminum angles and light plastic conduit. Used Weatherseal connectors at the wing roots and at the tips. The plastic header tank was replaced with aluminum shortly after photo was taken.

[jrevens]

I used the same connectors for my wing lights as you did, Jim... at the wingtips & behind the seats. Ran my wires through 3/8” black thin-wall sprinkler system tubing through the spars. Running your fuel line towards the center takes 1 or 2 less bends than going around the right side like I did, which is good. I made an aluminum channel for a wire chase located under the pilots seat, and ran another bundle under the right seat supported by Adel clamps and the airframe tubing, transitioning to a couple more channels under the center counsel going up to the firewall area.

[Flybyjim]

Thanks, guys,
It is always amazing to me how many wires we need for simple planes!

[David47]

I've done the same routing as Phil; i.e. rear fuselage wire cables down the RH side and wing cables down the LH and RH sides. I've reserved the centre console area for fuel and brake lines only, rudder cables excepted of course .... Separates electrons from fluids.

[jiott]

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.

[Esser]

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

[David47]

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.

[jiott]

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.

[jrevens]

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.

[efwd]

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

[PapuaPilot]

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.

[jiott]

Well I guess that explains where the recommendation comes from. The "where practical" is the big variable that each builder must decide for himself.

[David47]

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.

[Esser]

What’s the recommend practice for securing uel lines? I’m assuming zip ties are out. Adel clamps?

[efwd]

I believe most use Adel with rubber guards.

[jiott]

I used a combination of adel clamps and zip ties on the rubber fuel hoses.

[PapuaPilot]

What’s the recommend practice for securing uel lines? I’m assuming zip ties are out. Adel clamps?

Here is the info from AC-43.13-1B:
b. Routing. Make sure that the line does not chafe against control cables, airframe structure, etc., or come in contact with electrical wiring or conduit. Where physical separation of the fuel lines from electrical wiring or conduit is impracticable, locate the fuel line below the wiring and clamp it securely to the
airframe structure. In no case should wiring be supported by the fuel line.

d. Bonding. Bond metallic fuel lines at each point where they are clamped to the
structure. Integrally bonded and cushioned line support clamps are preferred to other clamping and bonding methods.

f. Support clamps.
(1) Place support clamps or brackets for metallic lines as follows.
Tube O.D. . . . . . . Approximate distance between supports
1/8”-3/16”--------------------------------- 9”
1/4”-5/16”--------------------------------- 12”
3/8”-1/2”----------------------------------- 16”
5/8”-3/4”----------------------------------- 22”
1”-1 1/4”----------------------------------- 30”
1 1/2”-2”----------------------------------- 40”

(2) Locate clamps or brackets as close to bends as possible to reduce overhang. (See figure 8-12.)


These comments are from me:
Notice they say cushioned clamps are the preferred method (i.e. adel clamps). They also touch the metal line to do the bonding to the airframe.

FYI tie wraps are bad on metal fuel hoses as they can chaff and make a weak spot or hole.