Trim with the Garmin G3x

[tracstarr]

Hmm, booster eh... i'll have to find out about that.

I've decided to pass on the AP right now.

But sounds like a trim position sensor - if not too expensive - is what's needed here too. So many things.

[efwd]

Just kinda reviewing this post.
I see we have two aspects that we are discussing. The G3X will adjust the rate at which the trim will move and its based on the airspeeds that you program in as when to move fast and when to move slow when you hit the switch. The G3X wont actually auto trim unless you have the AP as I believe Brian states how Dynon works. What the Garmin lacks is the amperage needed to drive our Pitch servo motor hence the Safety Trim Booster.
FWIW the Vertical Power unit also has the "trim rate" function for low and fast air speeds.

[aviator79]

The G3X wont actually auto trim unless you have the AP as I believe Brian states how Dynon works.

"Auto trim" is a deceiving term. One might think that the airplane will keep itself in trim while you're flying it. It won't. It allows the autopilot to operate the trim to alleviate the load on the AP pitch servo, just like the pilot would.

What the Garmin lacks is the amperage needed to drive our Pitch servo motor hence the Safety Trim Booster.

Just to clarify, by Pitch servo motor, you mean the trim motor, not autopilot servo correct? The Vertical Power and Advanced Control Module both have "smart trim" built in, and can supply the trim motor with adequate current. It might be something to consider when deciding to spend the $$$ on one of these systems. They incorporate a lot of functionality into a single red box.

[tracstarr]

Just kinda reviewing this post.
I see we have two aspects that we are discussing. The G3X will adjust the rate at which the trim will move and its based on the airspeeds that you program in as when to move fast and when to move slow when you hit the switch. The G3X wont actually auto trim unless you have the AP as I believe Brian states how Dynon works. What the Garmin lacks is the amperage needed to drive our Pitch servo motor hence the Safety Trim Booster.
FWIW the Vertical Power unit also has the "trim rate" function for low and fast air speeds.

Right. I was just reviewing the VPX docs as I am planning on using it. The trim is locked at 1 amp, so no good either.

[efwd]

yes, pitch trim motor not the AP servo.

[patrick.hvac]

Sorry to bring back an old thread. Been searching on the trim motor issue.
Is the current solution still to install the booster module?
Currently drafting wiring diagrams for VPX GSA28 integration and it looks like regardless of configuration the GSA will supply the trim motor and require a boost.
Confirmation would be excellent.
TIA!
Pat.

[Geek]

Pat,

Think the booster is the only way. The trim motor wants too much current for the GSA to supply. I am in the process of doing some of my wiring and this is the schematic I came up with. NOTE that I have not tested this so can't tell you it's right with 100% confidence but think it's in the right Zip code. Also I am using a trim switch on the stick and not the center console so you won't see the switch wiring that Kitfox uses. I think the VPX will swap the power and ground when you command nose up or down.

Hope this helps

Gary

Autopilot and Trim.jpg

[Geek]

With regard to the VPX and whether or not it swaps polarity on trim output pins (J1 pins 11 and 12). I emailed VPX the drawing and asked the question because if it didn't, I was going to have to replace the VPX in my trim system with two relays (not hard but just another component in the system). Really happy with the response time from VPX- great support. Turns out the VPX does swap the polarity on those two pins so it puts out both the 12VDC and ground needed to correctly send signals to the auto pilot that then passes the commands to the trim booster. You still need the trim booster to power the trim motor since both the Garmin auto pilot and the VPX are limited to provide a max of only 1Amp and I've heard that the trim motor requires something along the lines of 7 amps. Only thing on the drawing that VPX noted was that I show power on J2 and there is no power available on J2. That is there only as a reminder to me because I am still laying out my power distribution (adding an external alternator). Hope this helps

Pat,

Think the booster is the only way. The trim motor wants too much current for the GSA to supply. I am in the process of doing some of my wiring and this is the schematic I came up with. NOTE that I have not tested this so can't tell you it's right with 100% confidence but think it's in the right Zip code. Also I am using a trim switch on the stick and not the center console so you won't see the switch wiring that Kitfox uses. I think the VPX will swap the power and ground when you command nose up or down.

Hope this helps

Gary

Autopilot and Trim.jpg

[Shadowrider]

Yes you need the safety trim from TWC. It provides power to the trim motor.