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  #11  
Old 12-19-2018, 09:56 AM
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bkervaski bkervaski is offline
 
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Location: Birmingham, Alabama
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Quote:
Often times what people think is free and no friction (they are usually comparing to certified airplanes they have flown), is far from that.
It's definitely free and no friction, I can pinky-push it up and down with no effort. Same positive and negative. Very balanced.

Compared to the Cherokee I was flying it's like magic and unicorns.

I'm thinking it's just something with my numbers. Going to take pics and send them to G3Xpert and see what they say.
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  #12  
Old 12-19-2018, 11:11 AM
Ender Ender is offline
 
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I'm an autopilot and trim guy as my day job.

EDITED OUT what I initially said, I saw what handles the other guys have to tuning trim.

If they are running 100% and 25% duty cycle for their trims at those speeds and everything is fine, then maybe it's not the trim parameters.

The other thing would be if maybe the ALT CAP and/or servo gains are too high and they end up using more torque than you need. But you would feel that as it would be pretty sporty.
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Last edited by Ender : 12-19-2018 at 11:15 AM.
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  #13  
Old 12-19-2018, 01:24 PM
BillL BillL is offline
 
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Quote:
Originally Posted by g3xpert View Post
bkervaski,

You should not see this behavior. When properly setup the autopilot should not hunt and should feel rock solid.

Please send us an email including your autopilot and autotrim settings as well as a flight data log of the autopilot hunting.

Thanks,
Levi Self

Team X Project Manager
Follow the instructions and set the speed for auto trim start low and adjust your % speed for the trim as speed increases.

I would not use settings from a 7 for the 14, nor use someone else settings - use the tuning procedure from Garmin.
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  #14  
Old 12-21-2018, 09:09 AM
jdmrv7a jdmrv7a is offline
 
Join Date: Jan 2018
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Default RV 14-A

Thank you Walt for fixing this same problem on my RV14-A last month.

The bolt that connects the elevator push rod to the tail of the airplane was not perfectly adjusted and it was too tight. The pitch servo could not maintain the selected altitude until after the elevator was properly adjusted.

After adjusting this bolt the elevator moved with much less resistance and fixed the problem altitude hunting. I used the Van's recommended autopilot settings for the Garmin G3 touch. Contact Van's for those numbers.
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  #15  
Old 12-21-2018, 09:34 AM
Bavafa Bavafa is offline
 
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Quote:
Originally Posted by jdmrv7a View Post
Thank you Walt for fixing this same problem on my RV14-A last month.

The bolt that connects the elevator push rod to the tail of the airplane was not perfectly adjusted and it was too tight. The pitch servo could not maintain the selected altitude until after the elevator was properly adjusted.

After adjusting this bolt the elevator moved with much less resistance and fixed the problem altitude hunting. I used the Van's recommended autopilot settings for the Garmin G3 touch. Contact Van's for those numbers.
Now I am a bit puzzled by this, would you mind elaborating what adjustment is there with the bolt?
The AN3 bolt that connects the pushrod to the elevator horns go thru a bearing therefore should move freely. Unless there is an extra gaps between the horn and bearing in such way that pulls the horns out of its natural position, I can't see how/what other adjustments are there.

As I recall, mine took two washers (one on each side of the bearing) to align and also have proper shimming for the horn.
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  #16  
Old 12-21-2018, 09:35 AM
Nova RV Nova RV is offline
 
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I used the Vans numbers and found the pitch corrections too aggressive and toned it down by a third and it's much better now. Not as smooth as the roll servo, but close and I think I can tweak it some more to get it just right.
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  #17  
Old 12-21-2018, 09:36 AM
Bavafa Bavafa is offline
 
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Quote:
Originally Posted by bkervaski View Post
It's definitely free and no friction, I can pinky-push it up and down with no effort. Same positive and negative. Very balanced.
How much weight did you end up using to balance your elevators after paint? As I understand it, they need to be balanced individually and not connected together.
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  #18  
Old 12-21-2018, 09:44 AM
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bkervaski bkervaski is offline
 
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If it's not too much trouble, for a sanity check and comparison, can some of you 14 guys post your G3X Touch AP settings?
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  #19  
Old 12-21-2018, 09:50 AM
Bavafa Bavafa is offline
 
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Quote:
Originally Posted by bkervaski View Post
If it's not too much trouble, for a sanity check and comparison, can some of you 14 guys post your G3X Touch AP settings?
Mine is on post #10, I have reduced my pitch trim speed to 20% of the slowest.
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  #20  
Old 12-21-2018, 07:59 PM
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Walt Walt is offline
 
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Quote:
Originally Posted by Bavafa View Post
Now I am a bit puzzled by this, would you mind elaborating what adjustment is there with the bolt?
The AN3 bolt that connects the pushrod to the elevator horns go thru a bearing therefore should move freely. Unless there is an extra gaps between the horn and bearing in such way that pulls the horns out of its natural position, I can't see how/what other adjustments are there.

As I recall, mine took two washers (one on each side of the bearing) to align and also have proper shimming for the horn.
Actually this was the age old problem of the elevator AN4 center support bearing bolt not being properly shimmed. Without the correct spacers installed, when the center bearing bolt is tightened it side loads the elev hinge bearings which then bind the elevators. On a correctly installed elev, all the bolts are tight and the elev continues to "free float".
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