3 Axis Autopilot and Trim

[Auburntsts]

Originally Posted by rocketman1988

How often do you ride in the back?...

Me— never. But I’ve had plenty of pax in the back in all kinds of conditions and no one has ever mentioned it. My kids, in particular, would have let it be known without question and they were asked about it. Maybe my 10 is just lucky. All I’m saying is you can’t paint every 10’s performance with the same absolute brush—there’s just too many variables.

[rocketman1988]

Sorry, the ride in the back comment was supposed to be funny…most of us never ride in the back…

I find that the yaw damper does make a difference in turbulence; not so much when it’s smooth. I am glad I installed it…

[dmattmul]

Yaw damper + 1 (Good for passengers and back seat guests I’m sure)

Stuff hanging off the rudder, why bother?

[Everwild]

Originally Posted by dmattmul

Yaw damper + 1 (Good for passengers and back seat guests I’m sure)

Stuff hanging off the rudder, why bother?

Yeah, I'm leaning toward trying something like @Paddy implemented. It's the Aerosport spring bias system + a servo motor so the autopilot can manage trim when needed. Nothing hanging out in the breeze.

https://vansairforce.net/community/s...=191685&page=3

Sorta keeping it simple. Sorta not

[rocketman1988]

Be aware that if you intend on using a servo to activate the spring bias system, you will need to find the neutral point by changing the springs…trial and error. The aerosport capstan allows for basically infinite centering adjustment. Using a servo will create a finite range of motion (unless you use a capstan servo). It will work out fine but you will need to find the correct springs to bring the loaded rudder center into the range of the servo motion…

[Everwild]

Originally Posted by rocketman1988

Be aware that if you intend on using a servo to activate the spring bias system, you will need to find the neutral point by changing the springs…trial and error. The aerosport capstan allows for basically infinite centering adjustment. Using a servo will create a finite range of motion (unless you use a capstan servo). It will work out fine but you will need to find the correct springs to bring the loaded rudder center into the range of the servo motion…

Good point. It seems there is some flexibility in adjusting the length of the cables that attach the springs to the rudder pedal arms to find a good neutral starting point?

A small motor to drive the capstan is an interesting idea. Wonder if anyone has tried it?

Garmin mentioned the main limitation is you want to keep the draw under 1 amp or less or the yaw servo could be damaged controlling the trim servo/motor.

How much effort is needed to turn the knob on the Aerosport capstan? Anyone have a guess?

[Everwild]

Another quick question for folks who have used the Aerosport trim system. Does the Aerosport rudder trim have enough authority to center the ball on climb? Or is it mainly used for centering the ball in cruise ?

Not that I would mind using right rudder on climb but with a considerable investment in a 3 axis autopilot, you would want the system to have enough authority to trim yaw in climb as well.

This might be a good counter argument for a rudder mounted trim tab instead?

[rocketman1988]

Originally Posted by Everwild

Good point. It seems there is some flexibility in adjusting the length of the cables that attach the springs to the rudder pedal arms to find a good neutral starting point?

A small motor to drive the capstan is an interesting idea. Wonder if anyone has tried it?

Garmin mentioned the main limitation is you want to keep the draw under 1 amp or less or the yaw servo could be damaged controlling the trim servo/motor.

How much effort is needed to turn the knob on the Aerosport capstan? Anyone have a guess?

My system uses a linear actuator to move a bell crank which the springs attach to. There is about 2" of throw at the end of the bell crank. I needed to play with changing K, the spring constant, to get the loaded rudder neutral to correspond with the center of the actuator range of movement. It works well but definitely took some trial and error to refine.

I also think that a stepper motor/capstan system may be a better way to go...

That said, now that the rudder trim system is centered and working, I really do not move the rudder trim much at all during flight...certainly less than I would have thought. Not sure the effort to build the system was really worth it.

[MauleDriver]

Originally Posted by dmattmul

Although not much time in the 10 have about 200 hours in the 14 and they fly very similar. I have a yaw damper and that's pretty much it on the rudder. For the 7 minutes during the take-off to level flight phase I use right rudder (Really not much after I leave the runway) and it provides some exercise (which I need for my right leg) and after that zip for hours at a time. Even high bank angles don't need much rudder. (I'm a sailplane pilot so maybe I got use to using the rudder) Building a 10 and would not think of spending a minute adding anything more. The trim mods I've seen on the 10 and 14 rudder seem excessive for the time it's needed. In the end we are experimental builders and it's everyone's right to build what they want.

I now have 1300 hours or so in the ‘10, no rudder trim or yaw damper.

Dampers weren’t available when I built. Never missed it even in turbulence but of course, no back seat experience. Like so many mods; if you did it, you like it, if you didn’t do it you’re fine as-is.

I saw a relatively simple DIY spring trim system in a ‘10 I copied a lot of stuff from. I built it then never finished setting it up because I didn’t need it. Some right rudder during climb then feet on floor. But I too come from sailplanes, then a Maule so I miss using the rudder a lot. Just doesn’t need much and is very well behaved in stock condition.

Now if I can just figure out who put a dent in my rudder 10’ off the ground!!?? I know it wasn’t that deer I hit the other night…

[travisimperial]

I am really unfamiliar with GA avionics and what the plan is 5 years from now.. for now I'm working on the empennage, just finished Horizontal Stab and building the elevators now... Is this something that I need to decide now so that I can install whatever is required for an autopilot?

I do not plan to do rudder trim or yaw damp.. I was planning to do that spring system behind the pedals.