Kitfox - Trim Tabs to Fly By Wire

[kitfoxjim]

The name suggests that you can fly your Kitfox by wire, and you can, and do it quite cheaply. What you need is 3 axis trim tabs to control roll, pitch and yaw. This idea is not an autopilot, but that it can be added later, and also quite inexpensively.

What I am suggesting is the use of R/C servos which can control trim tab position precisely. I think most readers do not realize how simple this can be. Starting in the mid 90's I installed servos on all 3 axis of my Model 2. They worked very well and he aircraft could be trimmed hands-off at any speed. I went on to develop my own autopilot, which worked and was successful in that it would maintain GPS altitude and heading. Several iterations were tried over the years, but I was always behind development technologies. Works perfectly in calm air but lagged a little when the going gets rough in turbulence.

So: WHAT DO YOU NEED?

1: You need 3 or 4 servos, dependant on whether you want one on both ailerons or just one. There are hundreds of suitable servos available, source at your local R/C shop or browse listings here. Cost $20.00 - $60.00 for each axis or I have had good luck with even less expensive.

https://hobbyking.com/en_us/turnigy-...asc=1985125349
https://hobbyking.com/en_us/turnigyt...asc=5982608624

2: You need a controller for each Axis. Your local R/C shop should have servo testers which will work or you could try one of these. Approx $20.00 each axis

https://hobbyking.com/en_us/turnigy-...asc=9144583950
https://hobbyking.com/en_us/hobbykin...asc=3606071541

3: You need a 5 - 6 volt power supply for the servos, this will run off your aircraft 12-14 volt aircraft power.
https://hobbyking.com/en_us/turnigy-...asc=7484766100.
Again a $20.00 item and you only need one for all the servos. An alternate option here would be a USB power supply.

The mounting of the servos can be a big challenge especially after the a/c is covered, I can provide photos of several solutions if there is any interest. My model 5 has the servos all built in before covering. You could also start with one Axis trim control and add more if you like what is happening.

Aircraftautomation.com has servo trim tabs, servos and controller available which could be an easy route to follow. After many years of developing my own system I have ordered their autopilot which will be an easy conversion for me. A 5% discount is available at aircraftautomation.com by using code " JIMCORNER10 "

[Eric Page]

Jim, I'd be interested in photos/info about your rudder trim installation. I bought a servo, then designed and built a power supply and controller for it that works well. I plan to do something simple with a piece of piano hinge for the tab, but I seem to be over-thinking the physical installation. I'd appreciate seeing how you did it. Thanks.

[avidflyer]

Thanks for the added info and links. I was about to contact aircraft automation again to see how the auto pilot is working on the Kitfox in Florida that Carlos told me about. JImChuk

[kitfoxjim]

Jim, I'd be interested in photos/info about your rudder trim installation. I bought a servo, then designed and built a power supply and controller for it that works well. I plan to do something simple with a piece of piano hinge for the tab, but I seem to be over-thinking the physical installation. I'd appreciate seeing how you did it. Thanks.

This shows the servo installation on my Model 5. Much easier during construction.

IMGP2100.jpgIMGP2679.jpgIMG_2952.jpg

[airlina]

Here is my RC servo, cockpit adjustable rudder trim that was done a few years after my Series 5 was completed. Bruce N199CL

[Eric Page]

Thanks, guys!

I'm not a welder/fabricator, so your solution, Jim, is well beyond my capabilities. That said, I do like how you mounted the servo by cutting a rectangle in one of the ribs and using it as a mount. Very clever.

Bruce, your installation is much closer to what I had in mind. Does the inspection cover to the right of the pushrod fairing provide access to the servo? Do you have a picture of the servo mounting?

[kitfoxjim]

Here is my RC servo, cockpit adjustable rudder trim that was done a few years after my Series 5 was completed. Bruce N199CL

Looks great, I am surprised that more people haven't found a way to use this technology. Did you use an R/C servo tester for control or did you design your own?

Jim

[airlina]

Thanks, guys!

I'm not a welder/fabricator, so your solution, Jim, is well beyond my capabilities. That said, I do like how you mounted the servo by cutting a rectangle in one of the ribs and using it as a mount. Very clever.

Bruce, your installation is much closer to what I had in mind. Does the inspection cover to the right of the pushrod fairing provide access to the servo? Do you have a picture of the servo mounting?

Eric . here is the pic you requested , the servo is mounted in a bracket attached to the rudder rib below it. Bruce N199CL

[airlina]

Looks great, I am surprised that more people haven't found a way to use this technology. Did you use an R/C servo tester for control or did you design your own?

Jim

Jim, I did this mod back in 2007 or so and I found a guy online that made nice little 3 wire servo controllers that I installed in my center console . I just tried to find his website and its no longer there. The hardest part of the install was getting the wiring from all the way back to all the way front in a finished airplane. Bruce N199CL

[Eric Page]

Very helpful -- thanks again, guys.