Pitch Servo

Time: 1.5 hrs

Things done today:

  • Installed Garmin autopilot pitch servo
  • Installed plastic bushings in ends of rudder pedal tubes

Thanks to Jean and Torrance TAF for getting me the rose joint bearings so I could finish up installing the servos.



Here’s what I ended up with on the pitch servo arm. I used the 970-3 washer on the end (head side) as specified in the Garmin manual (Sling manual says an AN4) same as what was done on the roll servo. There’s a thin AN3 washer on the nut side which can’t be seen in the photo. Also it wasn’t entirely clear in the Sling manual, but it looks like the bolt goes into the middle of the three holes on the arm.

Installing the servo in the mounts was a little bit more challenging then I thought. When I initially looked at it I thought there was no way I was getting the bottom bolts on. It turns out it wasn’t that bad and as luck would have it I had purchased some 1/4″ socket extensions a few days ago which came in extremely handy getting the nuts on the back. Also to note the Sling manual called for AN3-3A bolts which seemed really short. I wanted to put a washer on the front so I went for an AN3-5A which seemed to be the perfect length.


The washers were a little bit of a challenge. I was able to put the washer on my index finger and reach around under the mount. If you pull the bolt back so the nut end is flush with the surface then you just slide the washer up and down and push the bolt through until it lines up and then push it through all the way. With the washer in place I getting the nut onto the bolt was the next puzzle.  I crammed some masking tape into the end of the socket to provide a little fill and some stickiness to keep the nut from falling out. Then used the socket extension by hand to thread the nuts onto the bolts. There are adequate holes in the rib to provide access with the extension. I use a long extension on the more aft bottom bolt and a short one on the front bottom bolt. I think the hardest part was getting the torque seal on the bolt. I had to use a chopstick with the seal on it and then carefully feed it through the hole to dab it on the bolt ends.


Some photos of the servo installed. Not sure where that torque seal on the screw head came from. In the above photo you can see the bottom aft bolt (below the screw). The photo was taken looking through a long cut out in the rib which made it possible to reach this bolt.



This is the control horn off the short elevator control tube. This is the arrangement of washers that I ended up with. It seems to line up well with the bearing on the servo (on the far right). I don’t have the push rod so I won’t be sure until I get that and install it.

Since I finished the brake lines on the rudder pedals I was thinking of how to lessen the rubbing of the brake lines that pass through the pedal tubes. TAF uses some plastic tubing that you put on the plastic brake line. I used stainless steel braided lines so the tubing doesn’t fit over it. The pedal tubes are about 5/8″ ID. I was originally thinking of a rubber stopper and drilling out the middle then slitting it to fit over the line and push it into the end of the tube, but looking through some of the stuff I had I found these split ring bushings (below) which after a little modification worked perfect.


I just needed to cut off a little material from both sides of the split area. The modified one is on the left and the original is on the right.


Slipped it around the brake line, pushed it into the end of the tube, and BOOM exactly what I was looking for.



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