CHAPTER 70 – Autopilot Installation

When Aerotronics received the autopilot, they forwarded it to me so I could install the units and measure for the cabling runs.  I had already decided I would build linkages like the flap control rods and run from the servos to bellcranks instead of trying to attach to pushrods.  The pitch servo was easy; I used some leftover large angle and made a mount under the elevator pushrod.  The roll servo was more difficult.  There wasn’t much room to work under the seat ribs and the clearance for the servo arm was tight because I had to leave room for the control stick to move fore and aft.  The control head I mounted across from and in the same manner as the strobe power supply.

When I mounted the pitch servo, I had intended to attach the linkage to it on the back side of the servo arm.  Unfortunately, there was not enough clearance between the arm and the servo body to allow this, and the angle of the linkage if I mounted it on the other side of the arm was not optimal.  So I ended up relocating the servo.  I used the same mount but moved the servo to the edge of it and fabricated a small bulkhead to support the aft section.  Mounted thusly, the servo is very steady, especially laterally.  The linkage is reasonably close to parallel to the elevator pushrod and there is no binding or interference in the linkages or bearing ends.  Note that I have captured the rod ends with AN970 washers just in case.

The roll linkage was run across the fuselage to the opposite control stick linkage.  This was done to minimize the roll effect caused by movement of the sticks in pitch.  If the linkage was short, the angular displacement would cause a noticeable movement in the aileron as pitch was changed. The last photo shows how close the linkages are when the stick is fully forward; I actually moved the arm aft 1/16” after this photo to increase clearance.

Once the servos were installed and the linkages were made up, the autopilot was sent back to Aerotronics where it will be tested in conjunction with the panel before the whole thing is sent back to me.  At this point, I have little else to do until the panel arrives except to work on some of the wheel fairings.  I’m hoping to go to Aerotronics before the panel is finished to view the process and be sure everything is right before it is completed.  Hopefully, the next update will be soon and will be really eye-catching.  See you then.