Wiring runs around the -9A gear weldments

Which is the better route for wires that are run across the top of the fuel and vent lines and then need to penetrate the spar carry through holes that are under the gear leg weldments?
Looks like the wires could go either forward or aft of the fuel & vent lines, then down to the hole.

Here the wires are going forward of the fuel & vent lines.


Here is the opposite side with the wires going behind the fuel & vent lines.


Before I start finishing up the wire runs, which way is preferred?

Bruce-
From my reading of AC43.13, and I could be wrong, wires should not generally be run below fuel lines. I think there might be exceptions to this, and I'm not sure if it is always possible to do so, but that's what I tried to follow when at all possible. (Sorry, don't have 43.13 with me to quote chapter and verse.) Consequently, my wire runs there are, like your second picture, aft of the fuel lines.
Hope this helps.
Steve

I agree with Steve: when possible, route electrical such that dripping flammable fluids can't ignite on a chaffed wire. I know you're not done but just a reminder to put grommets and anti-chaffe where needed around electrical and tubing.

All best

Jeremy Constant

Missing bolts?

I'm not at the hangar and don't have the drawings, but are there some missing bolts/nuts (empty holes) in the gear weldment? I could be wrong, but I seem to remember having to mark a special wrench to tighten a nut around that location...

All best

Jeremy Constant

jjconstant said:

I'm not at the hangar and don't have the drawings, but are there some missing bolts/nuts (empty holes) in the gear weldment? I could be wrong, but I seem to remember having to mark a special wrench to tighten a nut around that location...

All best

Jeremy Constant

Click to expand...

His wings aren't on yet.

wire runs

I think the important thing here is to make sure that the wires do not have any chaffing possibility with the fuel lines.

running the wires behind the tubes in pic 2 keeps the wires from under the tubes, but adds a new risk of the wires bending around a tight corner in a difficult area.

I think I would prefer pic1 with clamps and standoffs so that the wires cannot chaffe even though they now run under the tubes. my .02 is I would rather trade a possible problem with a leak dripping on wires for a guaranteed problem of wires chaffing on a fuel line.

conduit?

I have never seen the wiring for a RV, but did help on an older Glasair. I remember using thin plastic or PVC conduit. It wasn't sprinkler pipe or ribbed like the blue HD conduit, but more like tubing you would use on a fish tank or icemaker. It didn't have fittings at the corners, it was just to protect the wire and enable changes in the future. Looking back on it now, Im sure the guy I helped did not consider fire-smoke issues from the conduit. Maybe that isn't a big deal in places other than the FWF area. It did make a nice looking install with stand off clips. I will have to look at the electrical specifications in the FAA codes to understand what is and isn't allowed. I just started reading them last month - boring as heck, but filled with things I didn't know I had to know!

Per AC 43.13 - Ch.11-126 Wiring must be routed not to run parallel with the fluid line. A 2 inch separation must be maintained between wire and line except when wire is positively clamped to maintain at least 1/2 inch separation. I think if you butterfly clamp the two together and use spiral wrap were required you should be ok. ( Looks good )

There are areas where it's not possible to fully separate the fuel, electrical lines. The center "tunnel" from the fuel selector (especially when using the Airflow HP boost pump) forward to the conduit on the firewall comes to mind.

I decided to run all the center wires through the standard holes at the center of the spar. Then I dropped conduits at both sides from the forward deck down, and these went through the holes at the gear weldments.
The pictures in this post almost show what I did.

I looked but apparently didn't take a good picture of how these runs go through the weldment. I did use snap bushings, the black conduit that you can see, and the wire bundles were wrapped in SteinAir snakeskin.

I'm happy with how this worked out. It simplified wire routing and it's not in my way, even if it's visible in the final product.

You still have radio coax and pitot/static lines to get through those holes. They get too small really fast.

The missing bolts are the ones that hold the wing on. Too early for those!