Avionics and Panel wiring!

So I've mentioned before that I'm putting in a Garmin G3X avionics system. Over the last few weeks, the boxes have slowly been rolling in.

Putting it together has been kind of fun. Here is what the wiring diagram looks like:

Simple, right?

So, the crazy part is how these things are connected to one another. Think of each rectangle as a "black box" and the lines are the individual signal and power wires that go to each box. They are connected with DSUB pins. These are the kind of connectors you see on older monitors and printers. The only difference is, I am making the connections myself instead of just plugging a monitor cable into the end. 

Another intersting note is that the wire is pretty small - 22 gauge is typical. To put that in perspective, that's about 0.025 inches around. Kinda small. Typically, you would solder these connections. But since this is an airplane, we need a better connection. The answer is a crimped pin. 

Someone on vans air force was nice enough to let me borrow their military-spec crimper. This thing simply crimps down a pin or socket onto the wire. My avionics dealer has a series of videos on the tools, wire, crimping, etc. It's been very helpful. 

I put some Styrofoam models of the black boxes into the plane (this is before I had the real thing, and wanted to avoid damaging the real things moving them around) and planned out where all the wires would go. Then, I used the spaghetti diagram shown above to connect them all together using the tool and wires I was talking about earlier. 

 What's crazy is how precise the crimping is. In the second photo, you can see the slight difference between the top and bottom set of wires. The top set has too much insulation stripped off. The tolerance is 1/32 to 1/64 of an inch. Not much to work with there. The ones on bottom are within spec. 

Anyway, just do wires like that 70, 80 times and call it done! 

So, not much to show here other than I'm wiring away... 

FAB, mixture arm, cowl

Worked on the mixture arm again.

Finished up fabrication on all the subcomponents for the subpanel. Then I primed all the parts, which takes a couple days to dry. I'll have to wait until then to rivet it all together.

Getting the throttle body to work has been a pain in the ass, to say the least. Van's calls the air intake a forward air box (FAB), and it attaches to the bottom of the throttle body. On the other end, the cowl has a snorkel that provides ram air. In the middle of the FAB, there is a filter like you would find in a car. Of course, this means it has to line up with the cowl. On top of that, the captive bolts that connect to the throttle body cannot interfere with the filter. On top of that, the levers and cables for the throttle and mixture have come from either side and can't hit the side of the FAB. On top of that, each cable and lever has to be aligned at a certain angle to give enough torque so that the throttle body can go through it's full range of motion. And on top of that, the fuel servo sits off center on the engine, so it is shifted to one side.

So, all this bitching and moaning is about the fact that there are a lot of variables to account for with the throttle body..and when you mess with one it messes up all the other ones too. The good news is I came up with a solution. First, put the cables and levers into place. Make sure they are aligned correctly so that the throttle can go from the full range from open to closed, and the mixture arm can go through the full range of rich to idle cutoff. Then, go get a clear piece of plexiglass and cut it into the same shape as the aluminum top that serves as the mount to the FAB/throttle servo.

This way, you can see where the filter is and avoid positioning the FAB where the bolts would hit the filter, while keeping clearance for the levers that operate the throttle and mixture.

Even with all this, I'm going to have to make a cutout in the cowl. The end of the bolt is less than 0.25 inches from the side of the cowl, so the solution is to cut out that section and make it balloon out a little. You can see the minimal clearance here

I also fitted on the cowl just for grins to see how it would fit. Not too bad, need to make a few adjustments so everything is square and symmetrical.

The next steps are to get the servo sorted out, figure out the cowl, then start busting out the avionics. After that the wings and tail will go on, and hopefully some flying!

Subpanel and avionics choices

Continued with the subpanel.

Got everything test mounted and installed. Now just priming it before final riveting takes place.

I'm not going to rivet it into place just yet though because it will be a lot easier to install the avionics on the bench instead of inside the plane. But my plan is to have it ready to final-install after the wiring and avionics are complete.

Speaking of avionics, here's the current plan:

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That's the Garmin G3x Touch. It's basically the same thing that business jets have, except with more features like touch screen, angle of attack indication, and an infrared camera inset capability. Here's the expensive verision in a business jet. 

I have to say, this is pretty exciting. I'm hoping for a clean, functional, and capable flight deck and this seems to fit the bill. Other things I'll need to get or want to add are: 

• FAA-approved IFR GPS navigation radio
• Autopilot
• backup instrument (with backup power supply)
• lighting

Of course, all this comes with a pretty hefty price tag so it might be a while till those get added. Anyway, waiting to secure some cash so I can put my order in and install this. Should be fun