Pitot harness

Built out the pitot heat extension harness tonight. Unfortunately, the end result wasn’t quite what I’d hoped for, as we’ll see later.

I ordered wire like I mentioned previously, and it came in today. Unlike what I said before, I ended up ordering orange and blue wire instead of just white; the price was basically identical to buying white wire and colored heat shrink, and I figured having some spare wire around was slightly preferable to a whole set of colored heat shrink that I’d probably never use.

Anyway, this was pretty straightforward. I’d previously determined the length of the extension harness as 30”, so I cut the required length of black, orange, and blue wires, and crimped on the required terminals. That left the two tiny-gauge sensor wires; for these, I decided to twist the pair together to help facilitate keeping things neat. Then the small wires got micro Molex pins/sokets, and were installed into their connectors.

Finally, I connected everything to the controller harness, bust out my lacing cord, and bundles everything up. Not strictly necessary, but this should make it easier to feed this through the conduit when required:

Next up was a trial fit in the wing. What I’d hoped to do here was to run both the harness and the pitot/AOA lines through the conduit together. Well, the harness goes through OK, and the lines can be squeezed in there too, but already there there’s an issue: things are pretty tight, like I can hardly pull slack on either the tubes or the harness without dragging something else along. Worse yet, there’s no way to pull through the connector bundle at the tip rib, which is a requirement for getting enough slack at the pitot mount for servicing.

Yeah, it’s kind of tight:

So long story short, running the harness and tubing together seems like a non-starter. Looks like I’m back to routing the lines through snap bushings in the ribs instead. I’m also seriously considering adding another access cover beside the pitot tube to facilitate maintenance. I don’t especially like the idea, but I’m no longer 100% convinced that all my ideas for promoting serviceability are going to work. I think I’ll do one final experiment before going with that – clenching the wing skin in place, and seeing just how hard it is to reach in and over to the pitot bay if it were to become necessary. I think it’s doable, but maybe not preferable.

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