---

Installation Secrets

Push Pull Rod Saddles

by Joe Moore, Flight Engineering

Installing an autopilot in an aircraft which uses push-pull rods for the primary control surface control system often offers special challenges. The installation of the servos may require you to employ the usage of "saddles" on the push-pull rods to drive a servo bridle cable. Installation of the "saddles" (brackets) on the push-pull rods is often difficult due to the limited space around the control rods.

In theory, installing the saddles on the rods while they are out on the bench is the best way, but this is normally not feasible. In order to do this within the confines of the airframe try this procedure.

1. First, install the bridle cable on the servo capstan which you installed earlier.

2. Temporarily install the saddles on the control rods using double faced tape.

3. Attach the ends of the bridle cable to the saddles.

4. Rotate the saddles on the control rod to get good alignment of the bridle cables with the capstan.

5. Mark the location of both ends of the saddle.

6. Loosen the jam nuts at both ends of the control rod and rotate it to gain access for the drilling and riveting process. (Be sure to make note of the direction you rotate the control rod so you can return it to its original position).

7. After the drilling and riveting is complete return the control rod to its original position and retighten the jam nuts.

When this process is complete, check the airframe manufacturers maintenance manual to assure that the control surface travel is within the specified limits. Reattach the servo bridle cable and check once more for alignment with the capstan.

I hope this tip will help the next time you are faced with a push-pull rod control system. Please call if you have any questions.

Return to The S-TEC Approach Newsletter Index