Stec 30 aileron oscillation

[flyingchump]

So recently my auto pilot started oscillating back and forth.  The plane stays on it's heading but it feels like the autopilot bouncing back and forth from where center should be.  See video attached.  

Any ideas on what causes this?

[EricJ]

It may have developed a dead spot in the center of either the controls (e.g., a bearing wearing somewhere in the aileron system) or the sensor in the TC.   If there is more mechanical slop (deadspot) in the yoke movement center when on the ground than usual this may be contributing.

There are other things that might cause that, but that's a fairly easy one to check.

 

[Rwsavory]

It’s probably an issue with your servo. Short of an overhaul, you can exercise it on the ground by having it travel back and forth through its entire range several times. This worked for me for quite a while until an overhaul was necessary.  

[flyingchump]

50 minutes ago, Rwsavory said:

It’s probably an issue with your servo. Short of an overhaul, you can exercise it on the ground by having it travel back and forth through its entire range several times. This worked for me for quite a while until an overhaul was necessary.  

Any instructions on how to "exercise" the servo?

[flyingchump]

59 minutes ago, EricJ said:

It may have developed a dead spot in the center of either the controls (e.g., a bearing wearing somewhere in the aileron system) or the sensor in the TC.   If there is more mechanical slop (deadspot) in the yoke movement center when on the ground than usual this may be contributing.

There are other things that might cause that, but that's a fairly easy one to check.

 

There is a bit of slop in the alierons on the ground.  Once in the air there is no slop at all. 

[PT20J]

Most autopilot servos are connected to the controls with bridle cables. Proper cable tension is important.

[flyingchump]

22 minutes ago, PT20J said:

Most autopilot servos are connected to the controls with bridle cables. Proper cable tension is important.

I took a look at mine.  It's outboard on the pilots wing.  It's connected via a push pull tube, not cables.

[cbarry]

You can use the left/right turn command or knob on the Stec 30 to exercise the roll servo or possibly just roll the heading bug.  

[EricJ]

4 minutes ago, flyingchump said:

I took a look at mine.  It's outboard on the pilots wing.  It's connected via a push pull tube, not cables.

S-Tec and Century used pushrod controls.   The same idea holds, though, that there should be little to no play in the pushrod to the aileron belcrank.

 

[Ragsf15e]

Also I’ve read on here to exercise the “breakout” by commanding a left turn and then manually forcing a right turn (and vice versa). On the ground, and iaw the before takeoff checks in the checklist addition included in the documentation.