Gsa28 stop bracket

I'm mounting a GSA28 for pitch in my RV7, I used the second hole on the servo arm. The stop bracket is too small for the travel of the servo arm.

Full aft position, note the location of the stop bracket.


Full forward position, the stop bracket is rotate clockwise.


Is it best to trim the stop bracket to accommodate the larger travel?
Is it better to not install the stop bracket?

I believe the top hole is the recommended location, I would prefer not to install the stop bracket rather than modify it or have it installed incorrectly.

Hi Andy,

In the G3X installation manual it states:

The stops created by installing this bracket are redundant in the sense that the aircraft’s built-in stops should always be used as the primary means of limiting travel of the servo’s control arm.

Click to expand...

You are definitely doing the right thing by using the inner-most hole on the GSA 28 control arm. Always use the inner-most hole unless the geometry simply cannot be made to accommodate it. This will ensure the greatest amount of useable torque and best performance from your autopilot.

- Matt

Thanks for the replies!

g3xpert said:

Hi Andy,


You are definitely doing the right thing by using the inner-most hole on the GSA 28 control arm. Always use the inner-most hole unless the geometry simply cannot be made to accommodate it. This will ensure the greatest amount of useable torque and best performance from your autopilot.

- Matt

Click to expand...

Interesting that the only note to this effect is found on fig 12-8.3 which says use the inner hole, even the drawing on that page shows the outer hole being used.

All the diagrams and aircraft specific installations clearly show the outer hole being used without any such note on those figures.

In your first photo Andy it looks like the cotter pin head comes frighteningly close to contacting the push tube that controls pitch.

It could very well be a photo angle thing with plenty of actual clearance, but please check.

Thanks Kurt,
Yes that pic actually looks like it's hitting the push/pull tube. It actually has a solid 1/8 inch clearance from the nut, it's an average between hitting the nut and going over center when full forward. A 1/4 inch clearance from the nut puts the servo arm slightly more forward, with about 30 lbs (total guess) of force directly on top of the bell crank things flex enough to go over center. I doubt the force could ever be duplicated by actual stick or servo forces but it's my compromise.

Don't forget that an aircraft structure is not rigid and everything is moving and flexing, don't let that bellcrank get anywhere near going over center or jammin on something because if it does, its all over but the screaming

I guess for this reason alone is why I prefer and always use the top hole, this keeps the arm throw at about 45 deg from vertical with no chance of it going over center.

However I'm not sure if the Garmin servos will run out of muscle with the top hole, I do know the TT and Dynon servos work fine this way and generally with less than maximum torque setting.

Solved?

So Andy, What was your solution here? I see the same thing on my installation.