Garmin Autopilot Configuration

[rpigeek]

I just recently installed a GSA 28 servos and G3X & GMC 507. Does anyone have settings they’re using for the roll & pitch, but particularly pitch? I’m having difficulty getting it dialed in when the aircraft banks for a turn it drops the nose and is almost impossible getting back to maintaining altitude. It will drop the nose over about 3s and then raise the nose above for about 3s then down again.

I also have the speed adjusted electric pitch trim controlled through the pitch servo and wondering if I made that too slow at speed.

Any settings would be appreciated to start from.

 

[Walt]

Suggest turning off auto pitch trim until you get things sorted.
Servo torque at 30% is usually fine for RV’s but not sure about stick forces for a rocket.

 

[lucas2696]

Definitely need to do the initial setup/testing without auto trim on. Have you done the autopilot setup per the G3X manual? If you do the whole thing start to finish to the T it should yield a good result.

 

[Little Al]

Follow I'm at this point too on my Rocket did all the ground testing and setup according to the manual. Any guidance to what others are using to torque and gain value and setting on a Rocket for a good starting point would be most helpful.

 

[dmattmul]

I just recently installed a GSA 28 servos and G3X & GMC 507. Does anyone have settings they’re using for the roll & pitch, but particularly pitch? I’m having difficulty getting it dialed in when the aircraft banks for a turn it drops the nose and is almost impossible getting back to maintaining altitude. It will drop the nose over about 3s and then raise the nose above for about 3s then down again.

I also have the speed adjusted electric pitch trim controlled through the pitch servo and wondering if I made that too slow at speed.

Any settings would be appreciated to start from.

Vans has recommended settings for the RV-14 autopilot. They are close but slowing the servos down compared to recommendation is what I needed to do. Now very stable for the PID adjustments.

 

[rpigeek]

I'll turn off the auto trim for now and see if that helps. When I asked ChatGPT for a table for each of the Vans Aircraft it put together the following using this site as the source.

 

[mburch]

I asked ChatGPT

For something as important as the autopilot, I would suggest following only the procedures in the installation manual, not a random-word generator...!

 

[dmattmul]

For me this was the key to getting the A/P from "bouncing around". Trim Speed...... Slow the pitch trim speed way down, even approaches are on rails to mins now.

 

[rpigeek]

@dmattmul Mind sharing screen shots of your pitch & roll settings? I disabled trim speed, tried a various of things with pitch trim, emailed @g3xpert and just can't get this tuned. I've gone through the bump test / calibration. Emailed logs. All the other planes I have had no problem dialing in the G3X / GFC 500 (Savage Norde, RV-12, RV-7), but this plane is struggling.

If I have aircraft in heading mode with altitude hold at 200 KTAS, and I command more than a quick turn (i.e. 45 degrees) it'll drop the nose -300 feet, eventually it'll catch it and then go +300 and take a few times to settle back to the altitude. -300 on an approach is a big problem.

I'm currently at the following on pitch. I now have pitch trim disabled and I adjust it manually until I get this sorted and remove that as a factor.

Pitch Servo Max Torque: 50%
Pitch Servo Gain: 0.6
Min Airspeed: 70 kt
Max Airspeed: 200 kt
Vertical Speed Gain: 1.25
Vertical Accel Gain: 1.5
Airspeed Gain: 1.5