Garmin autopilot with G3X

After 10 hrs. flying with Garmin autopilot GSA28 servos with a G3X system, I've got a few questions.

With the roll servo set to .25 torque and a gain of .35, it tracks a course adequately, but wanders a bit left to right, never more than 1/2 a dot off. In other words, it's a little lazy for my taste, so I increased the gain to .40 and then to .45. At the .45 gain setting, it wanders a little less, but when I hit some light to moderate turbulence the stick whipped left to right several times in rapid succession. I stopped it by just holding the stick, effectively overpowering the servo. Is there a happy medium between .35 and .45 gain setting where I won't get the whipping left to right of the stick in turbulence? My experience with brand TT in turbulenece didn't have the same effect.

In trying to get the autopilot to track a course, after selecting the HDG/NAV button, then the CRS button, the heading would keeping flashing and I couldn't figure out how to stop the flashing without pushing in on the joystick, which would cancel the course select and put me in heading mode. How do I get the flashing heading to extinguish and stay in nav mode?

The vertical mode works very well holding altitude and climbing or desending as directed with the factory settings. The altitude is never off by any more than 10 feet.

Thanks in advance for your responses,

Mike

Can't help with the first half of the question. I am still on the GX pilot.

As for the second half...

What was your NAV source when you were trying to adjust the Course?

If it was a GPS, your GPS will have to be in OBS mode to adjust the GPS course. (Typically only the panel mounts (or the internal G3X GPS) have the ability for the G3X to control their course) Otherwise the course is automatically driven by the GPS's active flight plan.

If it was a NAV receiver, you need to make sure that your CDI source is set correctly to that receiver and that you are in VOR or LOC mode. Be aware that some radio's like the SL30 won't allow changes to the course when tuned to a localizer frequency...

alcladrv said:

After 10 hrs. flying with Garmin autopilot GSA28 servos with a G3X system, I've got a few questions.

With the roll servo set to .25 torque and a gain of .35, it tracks a course adequately, but wanders a bit left to right, never more than 1/2 a dot off. In other words, it's a little lazy for my taste, so I increased the gain to .40 and then to .45. At the .45 gain setting, it wanders a little less, but when I hit some light to moderate turbulence the stick whipped left to right several times in rapid succession. I stopped it by just holding the stick, effectively overpowering the servo. Is there a happy medium between .35 and .45 gain setting where I won't get the whipping left to right of the stick in turbulence?

In trying to get the autopilot to track a course, after selecting the HDG/NAV button, then the CRS button, the heading would keeping flashing and I couldn't figure out how to stop the flashing without pushing in on the joystick, which would cancel the course select and put me in heading mode. How do I get the flashing heading to extinguish and stay in nav mode?

The vertical mode works very well holding altitude and climbing or desending as directed with the factory settings. The altitude is never off by any more than 10 feet.

Thanks in advance for your responses,

Mike

Click to expand...

Hello Mike,

First, the default roll gain is 0.50, which has always flown two place RVs well, so we probably need to get back to basics.

We are reading the post and not fully understanding the autopilot mode that is being used to determine lateral (roll) performance.

We don't know what kind of nav radios you have, but let's assume for now that you have internal flight planning selected, and are using the GPS internal to the display(s) to flight plan and navigate.

As you know, for a G3X system without a GMC 305, the PFD softkeys are used to select the lateral and vertical autopilot modes.

Pressing the HDG/ROLL softkey on the lower left does two things. It exposes the AP lateral mode softkeys (AP HDG, AP NAV) and also selects the HDG bug field for editing.

The flashing you are seeing for the HDG bug field is just the normal behavior when you push this softkey and has little to do with the autopilot. When the HDG field is selected and flashing, you can turn the joystick to change the selected HDG. As you noted, you can press the center of the joystick to de-select this field and stop the flashing, but this does not put the autopilot into heading mode.

For VFR flying using the internal GPS, you have two lateral modes - HDG and NAV. If you want to couple laterally to a flight plan, just enter a flight plan and use the AP NAV softkey to select this lateral mode and track the course line between waypoints.

It sounds like you have already figured out the vertical modes beneath the ALT/PITCH softkey which include vertical speed, pitch and altitude hold.

We are wondering if maybe your autopilot was in ROL mode laterally (instead of NAV mode holding a course line) when your autopilot performance appeared lazy.

If you send us a flight data log file from your SD card taken during this flight we can see many things including active and armed autopilot modes and autopilot performance.

Please contact us via email or phone (see below) and we will help you get everything sorted out. Please also make sure you have the latest software loaded into your system.

Thanks,
Steve

What are the best settings for pitch and roll for a 180hp fixed pitch RV-7 with G5, GMC307 and two servos?

Jesse said:

What are the best settings for pitch and roll for a 180hp fixed pitch RV-7 with G5, GMC307 and two servos?

Click to expand...

Hello Jesse,

These settings should be a good starting point for a RV-6/7/8/9.

Thanks,
Steve

Roll Servo
Max Torque = 15%
Servo Gain = 0.40
Fine Adjust Amount = 1
Fine Adjust Time = 0.20

Pitch Servo
Max Torque = 30%
Servo Gain = 1.30
Fine Adjust Amount = 1
Fine Adjust Time = 0.20

Pitch Gain
Min Airspeed Limit = 65 kt (or as preferred)
Max Airspeed Limit = 180 kt (or as preferred)
Vertical Speed Gain = 1.00
Vertical Accel Gain = 1.00
Airspeed Gain = 1.00
Airspeed Accel Gain = 1.00

Electric Trim
Airspeed Thresholds = 80 kt / 150 kt
Roll Trim Motor Speed = 100% / 25%
Pitch Trim Motor Speed = 100% / 25%

A/P Settings

G3xpert, Is there an equivalent range of settings for the RV-10? I find that with just enough pitch servo gain to maintain altitude during turns (20 degree bank), I'm getting low amplitude pitch oscillations in level cruise in smooth air. If I lower the gain to fix the oscillation in cruise, then the nose drops and then overshoots up during the turn. Can I fix this in the advanced settings maybe?

Paddy said:

G3xpert, Is there an equivalent range of settings for the RV-10? I find that with just enough pitch servo gain to maintain altitude during turns (20 degree bank), I'm getting low amplitude pitch oscillations in level cruise in smooth air. If I lower the gain to fix the oscillation in cruise, then the nose drops and then overshoots up during the turn. Can I fix this in the advanced settings maybe?

Click to expand...

Hello Paddy,

Probably best to shoot us an email with all your present settings and a short description of improvements you are after (like above) and we can suggest some changes.

The vertical speed and vertical accel gains also affect altitude hold (and flying LPV and ILS approaches). While those seldom need to be changed from 1.00, in some cases we may suggest a change there.

We also often ask for a flight data log file which tells us a lot about how the autopilot is flying the plane.

Below are the starting autopilot settings we recommend for a RV-10.

Thanks,
Steve

Roll Servo
Servo Direction = Normal
Max Torque = 75%
Servo Gain = 0.80
Fine Adjust Time = 0.20
Fine Adjust Amount = 0 (disabled)

Pitch Servo
Servo Direction = Reversed (at least in this test plane, probably all)
Max Torque = 100%
Servo Gain = 2.50
Fine Adjust Time = 0.20
Fine Adjust Amount = 1

Pitch Gain
Min Airspeed Limit = 70 kt
Max Airspeed Limit = 180 kt
Vertical Speed Gain = 1.40
Vertical Accel Gain = 1.00
Airspeed Gain = 1.35
Airspeed Accel Gain = 1.00

Yaw Servo
Servo Direction = Normal
Max Torque = 100%
Servo Gain = 1.50

Manual Electric Trim
Airspeed Threshold = 80 kt / 150 kt
Roll Trim Motor Speed = 100% / 50%
Pitch Trim Motor Speed = 100% / 50%

g3xpert said:

Hello Jesse,

These settings should be a good starting point.

Thanks,
Steve

Roll Servo
Max Torque = 15%
Servo Gain = 0.50
Auto Trim Motor Speed = 5%
Fine Adjust Amount = 0
Fine Adjust Time = -.--

Pitch Servo
Max Torque = 30%
Servo Gain = 1.30
Auto Trim Motor Speed = 5%
Fine Adjust Amount = 1
Fine Adjust Time = 0.20

Pitch Gain
Min Airspeed Limit = 65 kt (or as preferred)
Max Airspeed Limit = 180 kt (or as preferred)
Vertical Speed Gain = 1.00
Vertical Accel Gain = 1.00
Airspeed Gain = 1.00
Airspeed Accel Gain = 1.00

Roll Trim Motor Speed = 100% (fastest, 80 kt) / 25% (slowest, 150 kt)
Pitch Trim Motor Speed = 100% (fastest, 80 kt) / 25% (slowest, 150 kt)

Click to expand...

Thanks for this feedback. Jesse posted this question for me. I'm still working through some issues and may end up calling one of you all, but for now I do have 2 quick questions as I try to figure this out.

Components: G5/GMC 307/ 2 axis GSA 28/ Aera 660

Issue: Autopilot does not stop at Altitude and searches up and down continuously

Possible causes:
- G5 has older firmware (2.4) - My G5 menu doesn't not even has some of the recommended settings that you are describing above. So I will upgrade to latest (which I believe is version 2.7 ) change to recommended settings and see if it improves. Hopefully that will fix it or provide additional settings that I can tweak.

- Another possible cause is my existing electric trim. There isn't enough documentation about this that I could find. We tied the auto trim feature into my existing electric trim. I'm not 100% sure this is working correctly or if it's the cause. The existing electric trim is a Ray Allen system controlled by a G307 Stick Grip with Ray Allen Speed Control (SPD-1). If I'm understanding the Garmin system correctly, Garmin unit is essentially taking over the Speed control. So if this is the case, should we eliminate the Ray Allen Speed control or should we disconnect the 2 auto trim cables from the Garmin unit (understand that I would lose auto trim but it may be the cause of my issue).

- 2 other points to note here

1. The Roll settings are working really nice. Holds heading nicely and follows GPS heading from the 660 great. ( so is the aileron trim working properly and not the elevator trim? We wired both exactly the same to the Garmin unit)
   
2. When I hit the Blue "LVL" button it's rock solid. It holds heading and altitude very well. Does this use the trim? Does it only use current heading and altitude values and not the flight director? What's different in the LVL feature that it can hold altitude but the normal Altitude preselect doesn't work....?

Just a little confused and a bit frustrated


I'm basically trying to find out if this is merely a setting issue (maybe wrong software) or a trim issue.

BCP Boys said:

Thanks for this feedback. Jesse posted this question for me. I'm still working through some issues and may end up calling one of you all, but for now I do have 2 quick questions as I try to figure this out.

Components: G5/GMC 307/ 2 axis GSA 28/ Aera 660

Issue: Autopilot does not stop at Altitude and searches up and down continuously

Click to expand...

Hello Amir,

Please install the the V2.70 software update and see if this doesn't significantly improve the altitude hold function.

Changes made from version 2.60 to 2.70:
Improved GPS aiding from GTN and GNS navigators
Improved flight director ALT mode performance
General improvements to system operation
Includes GSA28 software version 3.20

Yes, speed scheduling is provided by the GSA 28 servos, so you should disable speed scheduling provided by any other system.

Please contact us at [email protected] for product support. Much easier and more direct than posting questions on a web forum in hopes that we find them.

Thanks,
Steve

Thanks Steve. I will take out the Speed control and update the software - one at a time of course

Just a quick update:

I updated the software today, went and flew without taking the original speed control off ( trying to do 1 thing at a time) and the autopilot flew great. I have to say I absolutely love the IAS feature.

Thank you Garmin.