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  #1  
Old 04-15-2021, 09:54 AM
flyindoorman flyindoorman is offline
 
Join Date: Apr 2009
Location: San Antonio, Texas
Posts: 139
Default GRT Autopilot

I recently purchased a new to me RV8 and knew that the autopilot needed to finish being tweaked for peak performance. I have it pretty well dialed in now except for when tracking the GPS signal it is in a constant left then right weave back in forth. Can anyone head me in the rite direction of which adjustment needs to be tweaked now?

Thanks
Randy
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  #2  
Old 04-15-2021, 10:07 AM
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rv8ch rv8ch is offline
 
Join Date: Feb 2005
Location: LSGY
Posts: 3,755
Default

Is the autopilot moving the stick left and right, or just a tail wag?

If the first, then you need to back off on the servo gain a bit. That solved it for me. If you have tail wag, you need to leave a foot on the rudder, or install a rudder trim tab, or a bungee cord to hold a bit of pressure on the rudder cable.

I'm using my foot today, but one day will install a bungee.

Do you have the autopilot install and setup guide?

https://grtavionics.com/product/grt-autopilot-servos/

https://grtavionics.com/media/Autopi...tup-071718.pdf
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  #3  
Old 04-15-2021, 11:10 AM
flyindoorman flyindoorman is offline
 
Join Date: Apr 2009
Location: San Antonio, Texas
Posts: 139
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I believe the stick is moving slightly I will confirm on next flight.

Randy
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N9LR RV8
N38DG RV7 sold
N204GS RV10 Traded
N63AZ Harmon Rocket II Purchased Sold
N433RV sold
RV10
Dues paid 2020
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  #4  
Old 04-15-2021, 11:36 AM
lr172 lr172 is offline
 
Join Date: Oct 2013
Location: Schaumburg, IL
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best to read the manuals for guidance. The tracking sensitivity is set by both the roll servo gain AND a lateral tracking gain that I cannot remeber the name of. They need a bit of finessing to get the balance right. Changing just the roll servo gain will also affect localizer, VOR and GPS approach tracking sensitivity, as well has heading tracking which also has a separate gain setting.

There are intercept tests as well that will help you dial it in based upon over/under shoot and number or oscillations before stabilization.

Larry
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Last edited by lr172 : 04-15-2021 at 11:41 AM.
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  #5  
Old 04-15-2021, 01:34 PM
flyindoorman flyindoorman is offline
 
Join Date: Apr 2009
Location: San Antonio, Texas
Posts: 139
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Larry thanks for the reply I will take the manual up and try and adjust based on the flight test.
PS It doesn't stabilize just hunts back and forth.
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Randy
N9LR RV8
N38DG RV7 sold
N204GS RV10 Traded
N63AZ Harmon Rocket II Purchased Sold
N433RV sold
RV10
Dues paid 2020
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