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GFC 500 torque and gain rates

pokey

Active Member
About to complete a G3X GFC 500 install on my RV-4 and looking for a guidance that I didn’t find in search. Are there any recommendations for torque and gain rate settings for the initial auto pilot setup? Thoughts appreciated!!
Regards
Bill
 
The installation manual has a very detailed step-by-step guide to configuring and checking the autopilot... be sure to understand and follow it.
 
Servo torque

The servos have a capacity to pull 60 lbs.
I have set my torque percentage to 30 % and it works fine.
This setting makes it relatively easy to over power the servos if needed.
It also reduce the loading on control surfaces in turbulence.
If you set MIN-speed to a setting 80 kt and have the safety feature prevent unusual flight attitudes activated in the background (autopilot off) and would like to land at a speed of 60 kt, the pitch servo will push the nose down.
If you are at 300 ft with a torque setting of 100 % you will have to pull hard.
Start with the standard gain settings for the autopilot.
Climb to 5000 ft and push HDG + ALT hold, then find AUTOPILOT in the menu.
Print out pages from the manual to be handy.

Good luck
 
Start with the standard gain settings for the autopilot. Climb to 5000 ft and push HDG + ALT hold

Definitely do not do it this way - ALT mode is the last thing you configure, not the first. I can tell you from long experience with the configuration of this autopilot that the above advice will likely result in poor performance. Follow the instructions as written.
 
Servo torque and gain rates

Thanks for the input fellows. We have been precise in following the instructions but unlike the install we did on our 180 ( certified equipment) there doesn’t seem to be the same specific guidance for the RV-4 re torque and gain values. Ill get looking and reading.

Kind regards,
Bill
 
AP Gain Settings

About to complete a G3X GFC 500 install on my RV-4 and looking for a guidance that I didn’t find in search. Are there any recommendations for torque and gain rate settings for the initial auto pilot setup? Thoughts appreciated!!
Regards
Bill

Hey Bill,

We don't have standard autopilot settings for experimental aircraft, like we do certified airframes.

The current revision of the G3X Touch Installation Manual is AQ. That is where you will find the info you need to tune your autopilot to your aircraft.

  • Appendix A, at the end of the manual, is the In-Air Flight test procedure that you will use to tune the autopilot gains in flight. Follow the procedures listed here methodically and we should have your aircraft flying very well. It is very important to complete these steps in the order they are listed, and to not jump ahead if you are stuck on any one step. This is one of the more common mistakes made in this process. You can always give us a call if you get stuck on any step of the procedure and we can point you in the right direction.
  • Before completing the flight test procedure listed in Appendix A, Start with Section 35.4.10.3, which begins on page 35-51 and continue through page 35-114. These are critical on ground checkout procedures you will want to complete before ever engaging the autopilot in the air!

Thanks,

Justin
 
Not sure about a 4 but my 14A has torque of 50% and gain of .5 on pitch. Anything more than .5 gain causes the autopilot to be very ham fisted.
 
Auto pilot setting

I have set my:

Min air speed limit 60 kt
Max air speed limit 180 kt
Torque limit 30%
Pitch servo gain 0.5
Vertical speed gain 0.5
Vertical acceleration gain 0.5
Air speed gain 0.5

This works very good.

Installation Manual - GDU 4XX Config and Post Install Checkout
Rev. AT Page 30-79

Good luck
 
180kt is a little fast for max speed in an RV-4, usually 90% of Vne which is 164kt.
I understand why you have set min speed to 60kt, but I disabled the attitude protection (didn't have it before, don't need it now, just gets in the way when you want to turn upside down) and set min speed to Vs x 1.5, which I took as 75kt.
 
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