Electrical Wiring

March 5, 2013

The Early beginning, Planning, etc. - many, many Hours

When it comes to the wiring of the airplane, I must tell my story first. Of all the tasks that go into building an airplane, none of them intimidated me quite like the electrical wiring. I must confess, this is the weakest link in my skill set. I've done a bit of electrical wiring around the house, such as replacing outlets or installing simple devices, but all of that is a far cry from wiring an airplane to industry standards. When I was contemplating all of this, before I got started, I went to a monthly meeting of our local builders group in some guys garage and saw his unfinished project nearing completion. He was in the middle of his wiring and had a forest of wires going everywhere around the Panel area, and all I could think of was "oh my god... how on earth will I learn how to do that?" Fortunately, he saw me standing there with that look on my face, shaking my head. I talked with him at the end of the meeting. He told me to relax, I was looking at the forest. Don't do that. You look at one tree at a time. If you can take one wire at a time from a starting point to an end point, that's all there is to it. I said "yeah! I can do that!" So that's how I got started. It still bugged me though, honestly, all the time while I was building the airframe. But I started reading some resources, learning bits at a time, and looking at a lot of examples from other builders. I made the effort to make some really good friends and ask a lot of questions. You need to surround yourself with resources. And I will get lots of experienced eyes looking at my work, inspecting things for me, and helping me along the way.

I would suggest getting a copy of Bob Nuckol's AeroElectric Connection. This is the classic, much-referred-to source of information and a great place to get started. Another decision I made early on, that I'm happy about, is that I decided to install a Vertical Power VPX system. This saves a lot of headaches with wiring, eliminates all those circuit breakers and so on, I could go on and on about the benefits. Do some reading and check it out. They also have really good documentation that helps you learn a lot more about wiring your aircraft. With these resources in hand, and some good friends and people to call on and follow, I dove in and got started. So where do you begin? If I were writing a book about this, I'd probably call it "Electrical Wiring for Dummies", because that's what I am and how I feel about this. I have friends and I've seen others who design elaborate schematic diagrams, spreadsheets, and other fantastic tools and ways to plan and document everything. I can hardly read a schematic, let alone design one. So you won't see much of that here. And you know what? At the end of the day, those things are all nice, but you don't have to have them. I keep telling myself, one wire at a time; starting point to termination point. One system at a time from there. So with that said, here's literally how I started. I took the 10,000 foot view from above and decided the first thing I needed was a simple drawing, showing everything I wanted to install in my airplane, and roughly where it went. I still have this sketch, and it shows my inexperience in full view. But this really helped me get started. I didn't do this all at once. I actually worked on this in bits and pieces over some time, until I kept staring at it and couldn't think of anything else to add. You can see how I scratched things out, relocated some items, etc. I really have no idea how much time I spent on this.

Another decision I made early on, was to start at the tail and go forward from there. The main reason, as I thought about it, is because there really isn't a whole lot back there, and it's simple. You have your tail lights, and if you have electric trim, you have the servo for the trim tab. That's it. I wanted to start simple and gain some confidence, and I figured that as I moved forward, by the time I got to the panel and the firewall, I might actually know what I'm doing!

I should add a couple more notes to this page. It seems like the best place to mention these things. If you're building an RV, you most likely have some wiring issues in your mind right from the very beginning. One of the early decisions I made, when I was building the wings, was to NOT install the wiring conduit that you see many builders putting in their wings. I actually bought a roll of it from Vans and drilled all the holes for it in the wing ribs, but later changed my mind after a talk with my technical counselor at that time. He pointed out several issues to me, and his thoughts on the solutions, and I found myself agreeing with him. He built 2 RV's after all, both from scratch. One, a beautiful RV-8, and his second plane was an RV-3. Anyway, when you run a bundle of wires through the wings, you will have a few wires coming out along the way for things like Pitot Tube heat (if you have a heated pitot), OAT sensor, autopilot servo, landing lights, and so on. The rest of the wires go all the way out to the wingtip. So how are you going to pull a wire out of the conduit somewhere along the way? You'll have to figure out a way to put a hole in it, and then fish the wire out of it where needed. And how about if you ever need to change or replace THAT wire? Plus, he mentioned that inside a conduit, if a wire gets warm or hot it won't cool as well as it would if it's not inside a conduit. Finally, the material the conduit tubing is made of is highly flammable, according to him, and that's why the airlines don't use it. The solution, since you can reach every bay in the wing through either the ends or the access covers underneath, is to get some spiral wrap material, and bundle the wires in spiral wrap in between wing ribs. So I did drill the holes and install bushings in the wing ribs, and I'm going to use spiral wrap!

While I'm talking about the wiring in the wings, another thing you see a lot of builders do is install a big connector of some kind in the wing root, to connect all the wires in the wing to the fuselage wiring. It makes sense at first glance. Wire the wings, wire the fuselage, and then when you do final assembly, just plug everything in. I'm not doing that. For one thing, wiring up one more connector is something I don't want to do if I don't have to. And then, think about it... are your wings ever coming off? Once those babies are bolted on, they aren't coming off as far as I'm concerned. So why have connectors in the wing roots for all the wiring? I'm choosing to leave a wire bundle zip-tied outside the fuselage at each wing root, and leave it hanging there until I bolt the wings on for good. Then I'll pull the wires through the ribs and bushings, wrap them up with spiral wrap, and I'll be done. I will have continuous wire runs from starting points to ending points. One less failure point, less money spent.

Another decision I made early in the construction of my fuselage, was to install some short conduit runs under the seats, through the center section. This is the one place where I did use some conduit. When the seat pans are riveted on, there's no access under there. Van's doesn't allow much room for a lot of wires, frankly, in their basic plans, and trying to cram them all into the small holes and the limited space in the center tunnel, just isn't the best idea. So I followed the lead of a friend and installed some short conduit runs. You can see pictures, and how I did it, by clicking on this page from November 4, 2009.

Finally, I must also admit that the more wiring I have done, the more my confidence has increased, and the more I have enjoyed this! I will probably find, when it's all said and done, that this was truly one of the most enjoyable parts of the whole project. I will reserve final comment on that until I turn things on, though, and there's no smoke!

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Contact me: swayze "at" europa.com (replace "at" with the @ sign... no spaces... you know the deal)