January 27, 2020

Autopilot Servos Install and Fuselage Wiring

One of my first new year’s resolutions is to complete the fuselage wiring so that I can start tacking on the fuselage skins. So, I spent most of New Year’s Day working on wiring and a few other small tasks.

First, I finished off the install of the roll servo. I was all set to wrap this up and move on when I realized I installed the pushrod into the servo crank arm in the wrong position. The crankarm has 3 holes, and per the Garmin install manual, note 10 in the picture below, you’re supposed to install the pushrod to the innermost hole, unless it interferes with movement (which it did), so in this case the middle hole is the correct one. Well, to move the bolt to the middle hole — that requires removal of the castle nut and cotter pin… ugh. About an hour later, I had it all back together again, with the pushrod bearings reset to the new correct length.

GSA 28 install notes from the Garmin G3X System Install Manual (pub # 190-01115-01, rev AK)
Roll servo install – before fixing the crank arm issue

The pitch servo is loosely installed, but I’m running into a problem that Jim Pavlik also ran into – the crank arm is striking the stops on the servo, even with the pushrod attached to the outermost hole on the crank arm. It’s not supposed to hit the stops on the servo (these are just a backup); instead, the elevator movement should only be limited by the main stops on the long torque tube, which is just aft of the wing spar. Garmin does make a longer crank arm (part # 115-01738-01), but I haven’t found it available for sale, except as part of a RV-6 roll servo install kit. After I determined that staring at it for a good 15 minutes wasn’t going to fix anything, I decided to move on, and will come back to fix this later.

Deep-well 3/8″ socket needed to tighten the nuts for the elevator servo

Next I attached the boots to the firewall for the steering pushrods. Taking a suggestion from Craig M, I put a little glue on the edges of the plates so that the boots would stay in place while I riveted.

Boots for the nose steering pushrods

For the remainder of the day, I resumed running wires. For the wires that are carrying any significant amount of current (e.g., the pitot heater), I am twisting the leads together, just like I did in the wing; this is to help mitigate electromagnetic interference.

Lots and lots of wires!
Building up a collection of wires to run back to the rear fuselage

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