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Aileron Trim

Surfdoc

Member
Ordering the fuselage kit and wanted feedback from those who came before. I cant get a straight answer from anyone on the matter. I will have a Dynon autopilot system. Do I need the electric trim servo from Vans when ordering the fuselage? I have seen posts that the auto pilot will trim but Dynon says no. Any opinions are appreciated.
 
No

Autopilot will not trim but will maintain a track. You may find a slight osculation in bank without trim.

You can get away without it if you rig the aircraft such that it has a small roll rate with your hand off the stick. Rudder trim, aileron adjustment etc.

Putting trim in after will be a big job
 
If you have the Dynon autopilot controller as opposed to operating the autopilot from the screen, the autopilot has auto trim. For this to operate you have to have both roll and pitch electric trim. The autopilot controller also allows for wiring trim controls on both the pilot and copilot side without any additional relays.
Hope this is clear and helps.
 
I generally recommend against aileron trim, especially auto trim, due to the spring bias system used for the ailerons on RV's, it generally will not work very well. Not to mention it's unnecessary and adds complication. The AP will easily hold wings level unless perhaps the LH tank is full and the RT side is empty, keep the fuel somewhat balanced and you'll have no issues.
 
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I generally recommend against aileron trim, especially auto trim, due to the spring bias system used for the ailerons on RV's, it generally will not work very well. Not to mention it's unnecessary and adds complication. The AP will easily hold wings level unless perhaps the LH tank is full and the RT side is empty, keep the fuel somewhat balanced and you'll have no issues.

I'll grant you the "adds complication"part, and we may just agree to disagree about "unnecessary", but you're flat wrong about "will not work well". With the Dynon system it works great, not sure what your past experience was with.
 
Hello All, Thank you for the input. Now, quick question for someone who never flew with any type of electrical instruments let alone a, Auto Pilot. Does the Auto Pilot, Dynon, need to be engaged in order to level the wings? Or can I just trim using the dedicated AP control panel? Again, thanks to all for the advise.
 
Hello All, Thank you for the input. Now, quick question for someone who never flew with any type of electrical instruments let alone a, Auto Pilot. Does the Auto Pilot, Dynon, need to be engaged in order to level the wings? Or can I just trim using the dedicated AP control panel? Again, thanks to all for the advise.

The Dynon autopilot does nothing until it is engaged - it won't operate the servos or the trim until you engage it and give it a target to track - you are just hand-flying the airplane. You should have manual trim buttons on your stick or on the panel to adjust your electric trims manually if you need to.

Once the autopilot is engaged and it has a target to track, then it will command the servos (both elevator and aileron) to change pitch and roll as needed to reach those targets. If you have the dedicated autopilot knob panel installed, it will also start to auto-trim your airplane once you activate the autopilot - running the electric trim servos as needed to remove trim forces.

For example - if you are hand-flying the airplane and manually input a boatload of "up" trim and you are having to hold force on the stick to keep it level, and then you activate the autopilot for straight and level - the autopilot servos will take over and hold the airplane there, the servos will feel the out-of-trim condition and report it back to the autopilot controller which will then command the trim servos to run and reduce the trim force. None of that happens without the autopilot activated. Within several seconds of activating the autopilot the trim should be back to near-zero stick force required and the autopilot servos can easily hold the commanded targets.
 
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Hello All, Thank you for the input. Now, quick question for someone who never flew with any type of electrical instruments let alone a, Auto Pilot. Does the Auto Pilot, Dynon, need to be engaged in order to level the wings? Or can I just trim using the dedicated AP control panel? Again, thanks to all for the advise.

What Airguy said.

If you are asking specifically about the “Level” button on the Dynon, no - it works at anytime in flight. It does need the autopilot servos to be functioning with power available, but autopilot mode need not be on.

One other specific - you need to be operating with the SkyView autopilot in “expert” mode, not “simple” mode for the Level feature to work.

This Level function works very well.

Carl
 
Maybe...

My D180 with two axis asks for nose down trim at every engagement of the AP, and coming out of AP results in a pitch down that’s worth about 5-8kt in IAS. Honestly I haven’t done any work to figure it out. When in AP, it’s nicely solid in heading, good in GPS TRACK, and solid in tracing a radial on a VOR until you get close, as you’d expect. Altitude tracking is dead on, which is the odd part.
 
My D180 with two axis asks for nose down trim at every engagement of the AP, and coming out of AP results in a pitch down that’s worth about 5-8kt in IAS. Honestly I haven’t done any work to figure it out. When in AP, it’s nicely solid in heading, good in GPS TRACK, and solid in tracing a radial on a VOR until you get close, as you’d expect. Altitude tracking is dead on, which is the odd part.

Interesting - must be differences in the software. My HDX trims it to zero-force, you can kill the autopilot and not touch the stick and it just keeps doing what it was doing.
 
Clarification....

So when I said my D180 asks for nose down trim when engaging, I meant when eng aging from an already stable trimmed condition. I engage the AP a lot when having to navigate, I’m admittedly a little retentive following the sectional. Truth be told, I usually let the ‘down trim’ light flash, and disengage when I’ve gone back heads up, usually a minute or two. When I do sit on AP for longer than that, I trim the AP to happy.
 
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