Autopilot brackets

[lr172]

I did a pre buy a couple weeks ago on a 10 and found an issue that owners, especially buyers, should look for.

I noticed the ailerons traveled substantially shorter in one direction vs the other. Yes, i know about the differential travel. When i was inspecting the bellcrank area, I observed the servo arm hitting the arm on the safety stop. Went back and saw the aileron was not hitting its stop. The safety arms were acting as the stop. First, this means they were not getting full aileron travel and second, having the servo as a stop puts a LOT of stress on the control system. It appeared that some material needed to be shaved off the safety stop, as there didn’t appear to be enough travel area. It is possible that adjustment would have addressed it, but didn’t look that closely.

I suspect some builders would not take steps to insure this doesn’t happen, so wanted to pass this along for others to look at during a CI.

Larry

 

[Tony Kirk]

If it was a Garmin GSA 28 servo, the G3X Installation Manual (rev. AW), pages 16-33, 34 show how to install the roll servo and the stop bracket properly - no trimming required.

 

[AZSteve053]

I did a pre buy a couple weeks ago on a 10 and found an issue that owners, especially buyers, should look for.

I noticed the ailerons traveled substantially shorter in one direction vs the other. Yes, i know about the differential travel. When i was inspecting the bellcrank area, I observed the servo arm hitting the arm on the safety stop. Went back and saw the aileron was not hitting its stop. The safety arms were acting as the stop. First, this means they were not getting full aileron travel and second, having the servo as a stop puts a LOT of stress on the control system. It appeared that some material needed to be shaved off the safety stop, as there didn’t appear to be enough travel area. It is possible that adjustment would have addressed it, but didn’t look that closely.

I suspect some builders would not take steps to insure this doesn’t happen, so wanted to pass this along for others to look at during a CI.

Larry

Excellent Catch Larry, and Very Excellent post regarding it

 

[lr172]

If it was a Garmin GSA 28 servo, the G3X Installation Manual (rev. AW), pages 16-33, 34 show how to install the roll servo and the stop bracket properly - no trimming required.

View attachment 87806

Yes, it was 28’s. Like i said, this was just an inspection, so didn’t really spend anytime ascertaining reasons why or ways to remediate. It just looked like one of those issues that the non detail oriented builders would miss.

It was installed as shown in your diagram, though I didn’t measure the bell crank hole offset, but the vertical arm position was not adjusted to be the center of aileron travel. Far more to getting this right than just the position of the bracket. Levers, travel and torque seem to throw off a lot of folks.

 

[Walt]

I generally use the middle hole for aileron, allows closer to full throw of the servo in both directions which improves operation.

 

[lr172]

Yes, it was 28’s. Like i said, this was just an inspection, so didn’t really spend anytime ascertaining reasons why or ways to remediate. It just looked like one of those issues that the non detail oriented builders would miss.

I generally use the middle hole for aileron, allows closer to full throw of the servo in both directions which improves operation.

that makes sense. I think I used the far hole on the 10 and it is very stable, but suspect different geometry and flight characteristics compared to the 2 seater models. I am always amazed how refined the g3x AP is on my 10. The GRT on my 6 is nowhere near as smooth and refined. now if they could only make the 28's last lomger than 400 hours.

 

[Tony Kirk]

Yes, it was 28’s. Like i said, this was just an inspection, so didn’t really spend anytime ascertaining reasons why or ways to remediate. It just looked like one of those issues that the non detail oriented builders would miss.

It was installed as shown in your diagram, though I didn’t measure the bell crank hole offset, but the vertical arm position was not adjusted to be the center of aileron travel. Far more to getting this right than just the position of the bracket. Levers, travel and torque seem to throw off a lot of folks.

There is a lot more information in the G3X IM than the little screenshot.