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  #1  
Old 04-13-2019, 09:01 PM
jump4way jump4way is offline
 
Join Date: Sep 2008
Location: Coolidge, AZ
Posts: 339
Default Auto Trim issues

I'm curious to know if anyone else has been having auto trim issues with the Garmin auto pilot and G3X touch system.

I've been getting the occasional trim up or trim down indication when the autopilot is engaged but is unable to trim. In almost all cases, the trim servo will eventually make the requested input from the autopilot servo but it might take 6-10 seconds or so.

I've been through quite extensive troubleshooting with the G3X team and have to admit they have been great. We just have not solved the problem yet.

The parts in the system are an infinity stick grip, phaviation relay board, Garmin autopilot servos, and ray Allen trim motor.

My first autopilot servo was of a batch that needed to be exchanged so I was hopeful that would solve my problem... no luck. I installed the new servo and the problem continued. I swapped the roll servo to the pitch to see if the problem now went to the roll but no luck. I still get the trim up or trim down message.

I've looked at the connectors and wiring at the servo and the relay board with nothing out of the ordinary.

I'm getting 11.8V at the trim servo so there is a little bit of a voltage drop. I'm told from the ray Allen company that 11.8 is acceptable.

Ive been through all of the menus extensively with the G3x team and I'm confident that we have everything configured properly. I've tried various setting for the speed controller and nothing has worked yet.

I've checked for binding at the control arm of the trim servo. I did notice early on that the control arm was contacting a portion of the trim tab so I have relieved that area. Everything looks clear now.

I've spoken to PHaviation and as helpful as they have been we still have not located the issue. The same goes with Ray Allen servos...although they weren't quite as helpful.

Everyone says the same thing... if it works on the ground, our part is working. I cannot replicate the issue on the ground... it all works. I have noticed immediately after adjusting the speed control setting in configuration while on the ground, I will get an occasional delay in trimming. Garmin tells me this is normal in the configuration and should not be an issue while in flight under normal conditions.

I've also updated to the most current software.

Has anyone run in to any of this stuff and had any luck solving their problem?

I just want to reiterate how helpful Garmin and PHaviation have been. They really have gone above and beyond to this point. I'm hopeful I'll find the problem at some point.
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  #2  
Old 04-14-2019, 08:59 AM
BillL BillL is offline
 
Join Date: Sep 2007
Location: Central IL
Posts: 5,170
Default

Can you state the aircraft, flight condition, and what settings you have for torque and speed from the G3X?


My only experience is looking at flight data for a G3X touch & garmin 28 servos where the trim speed is set within the G3X.

Bottom line - the 10 can out accelerate the ability of the auto trim to keep up. I bet most RV's can do the same.

Flight data study is most helpful in determining exactly what is happening. By example: Look at trim command, trim position, and servo torque. If trim is commanded, position is moving, but torque is rising, then the trim speed is too low.
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Last edited by BillL : 04-14-2019 at 09:03 AM.
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  #3  
Old 04-14-2019, 04:30 PM
jump4way jump4way is offline
 
Join Date: Sep 2008
Location: Coolidge, AZ
Posts: 339
Default

This is in my RV-8. Iíve had it act up in various phases even as benign as level cruise flight and initiating a gentle climb. Iíve also tried to get it to act up by initiating drastic climb and descents with speed changes and it work fine. There seems to be no method to the madness.

Iím away from the airplane so I donít have the setting nearby to list. Iíll get back with that information. I have however tried many variations of settings.

I donít believe it is a speed issue. There is something restricting the movement. Once it starts to move, the trim up or down message goes away and all is fine. It just seems to not move on occasion as if itís bound up or restricted somehow.
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  #4  
Old 04-18-2019, 09:13 PM
Robertcropdust Robertcropdust is offline
 
Join Date: Jun 2013
Location: Tx
Posts: 87
Default Autopilot

I have something similar going on with a new g3x system on a new build. Im having trouble with the elevator trim. Iím going to look into it a bit more this weekend. The first and second time I turned the autopilot off it got very exciting on the the elevator control. Iíve only have 7 hrs on the bird and Iím sure I need to make more adjustments. Iím using the rv8 setting and flying speeds on my F1 rocket as a starting point. I have not turned it back on since since the initial testing. Iíve read through the manual a few times but the manual seems outdated.
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  #5  
Old 04-19-2019, 06:39 AM
mturnerb mturnerb is offline
 
Join Date: Apr 2015
Location: Ponte Vedra, FL
Posts: 1,161
Default

Interesting that this thread turns up now. I've been configuring and testing the autopilot on the ground in my RV14A with all Garmin/G3X touch setup, using all the Van's recommended settings. When I test the autopilot on the ground, following the installation manual's recommended steps, I consistently get "trim up" or "trim down" notices but I don't hear the trim motor actuating.

I haven't tested anything in the air yet (1 flight only so far) but when I call the G3X team all they can tell me is to follow the manual and they've sent some documentation that is mostly condensed versions of the manual. I've also been told that the autopilot behaves differently on the ground than in the air - this is concerning to me because while it may be true I'd really like to have a more illuminating explanation: tell me HOW it behaves differently on the ground and whether I should expect the trim motors to actuate on the ground when a climb or descent is commanded. No one seems to know this or want to explain it to me. The mantra is "follow the manual". Well I have followed the manual - please help me understand what I'm seeing and what it means!
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  #6  
Old 04-19-2019, 07:02 AM
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Walt Walt is online now
 
Join Date: Aug 2005
Location: Dallas/Ft Worth, TX
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Can't provide all the info you want but it is normal to see the trim messages when on the ground and the trim does not actuate when you see the messages (those are the manual trim messages).

I send out all aircraft with auto-trim turned off, first you must verify the AP is functioning as it should before turning on AT.

PS: very few (none) complaints from my 7/8 customers with default settings.

PSS: DO NOT grab the stick and fly the AC with the AP on, it will see that as an out of trim condition and try to correct for it, then when you disconnect the AP the AC will be way out of trim.
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Last edited by Walt : 04-19-2019 at 07:08 AM.
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  #7  
Old 04-19-2019, 07:08 AM
mturnerb mturnerb is offline
 
Join Date: Apr 2015
Location: Ponte Vedra, FL
Posts: 1,161
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Quote:
Originally Posted by Walt View Post
Can't provide all the info you want but it is normal to see the trim messages when on the ground and the trim does not actuate when you see the messages (those are the manual trim messages).

I send out all aircraft with auto-trim turned off, first you must verify the AP is functioning as it should before turning on AT.

PS: very few (none) complaints from my 7/8 customers with default settings.
Most helpful information I've seen!! Thanks Walt
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  #8  
Old 04-19-2019, 07:16 AM
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g3xpert g3xpert is offline
 
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Location: Olathe, KS
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Quote:
Originally Posted by mturnerb View Post
Interesting that this thread turns up now. I've been configuring and testing the autopilot on the ground in my RV14A with all Garmin/G3X touch setup, using all the Van's recommended settings. When I test the autopilot on the ground, following the installation manual's recommended steps, I consistently get "trim up" or "trim down" notices but I don't hear the trim motor actuating.

I haven't tested anything in the air yet (1 flight only so far) but when I call the G3X team all they can tell me is to follow the manual and they've sent some documentation that is mostly condensed versions of the manual. I've also been told that the autopilot behaves differently on the ground than in the air - this is concerning to me because while it may be true I'd really like to have a more illuminating explanation: tell me HOW it behaves differently on the ground and whether I should expect the trim motors to actuate on the ground when a climb or descent is commanded. No one seems to know this or want to explain it to me. The mantra is "follow the manual". Well I have followed the manual - please help me understand what I'm seeing and what it means!
Hello Turner,

Congratulations on getting your new RV-14A flying!

The system intentionally does not run the trim on the ground when the autopilot is engaged for a pre-flight test.

The last thing you want is the autopilot changing your trim settings after you have properly setup the aircraft trim prior to takeoff.

There isn't any value in sitting on the ground for extended periods with the autopilot engaged. That would need to happen to see the trim up/dn annunciations.

Thanks,
Steve
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  #9  
Old 04-19-2019, 09:16 AM
mturnerb mturnerb is offline
 
Join Date: Apr 2015
Location: Ponte Vedra, FL
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Quote:
Originally Posted by g3xpert View Post
Hello Turner,

Congratulations on getting your new RV-14A flying!

The system intentionally does not run the trim on the ground when the autopilot is engaged for a pre-flight test.

The last thing you want is the autopilot changing your trim settings after you have properly setup the aircraft trim prior to takeoff.

There isn't any value in sitting on the ground for extended periods with the autopilot engaged. That would need to happen to see the trim up/dn annunciations.

Thanks,
Steve
Steve - along with Walt's comments this is what I needed to know. Makes sense and now that I understand it's a non-issue. Everyone I've talked to at G3Xpert has been helpful - I'm not complaining at all about the effort but sometimes it's just the one piece of knowledge that closes the loop. I understand when I'm told behavior on the ground is "different" but the specifics are what matter. The step-by-step ground testing process in the manual doesn't give this level of detail either - it's good on telling you what to do/not to do (i.e. leave auto-trim off for initial setup and testing) but not so much what you'll see that might be different from expected behavior.
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  #10  
Old 11-14-2019, 02:04 PM
jump4way jump4way is offline
 
Join Date: Sep 2008
Location: Coolidge, AZ
Posts: 339
Default Auto trim

I just wanted to update my previous auto trim issues. After extensive support from Garmin, I was asked to replace the trim motor to see if that resolves my problem. I decided to have the trim motor bench tested by Ray Allen before purchasing new. They bench tested it and turned it around right away with a note stating ďno faults found. Relubed gear trainĒ. I was disappointed that a problem was not located but figured I would install it again just to give it a shot. Apparently, relubing the gear train solved the problem.

I could not be more impressed by the patience and support of the Garmin team in this situation. I hope this helps someone else down the line.
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