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3-axis autopilot?

JackinMichigan

JackinMichigan

Well Known Member
My father and I will be installing Garmin G3X systems in our RV-10, and it's our understanding that they have built-in 3-axis autopilot capability. However, the servo install kits we bought from Aerotronics have provisions for the roll and pitch servos, but not yaw (rudder). We've been told by a few people that yaw servos are almost unheard of in single engine aircraft.

BTW - This is different from rudder trim. We plan on buying Aerosport's bolt-on trim system for that.

My father wants to Rube Goldberg in a rudder autopilot servo anyway, and I'm hesitant. How necessary, or even desirable, is a rudder autopilot servo on an RV-10? Will it improve anything, or is it a waste of time and money? I'm guessing if it was worth the effort more people would do it.
 
I have a servo activated trim tab inset into my rudder, and it does everything I could want such a device to do.

PA010009.jpg
 
+1 what Mike said. I appreciate having rudder trim every time we make a long flight. I considered installing a yaw damper, but decided against it. After 3 years of flying I have never missed it.

Jim Berry
RV-10
 
RV's don't have a rudder bellcrank to attach a servo to, so you'd have to design something to make it work.
 
I don't have much time in RV's in general, and none in -10's but my understanding is that they have little enough adverse yaw that a yaw damper (rudder autopilot axis) is not required.
 
It's E-AB so you can do it, but IMO it's a waste of time and money. Of course, I feel the same way for rudder trim as well (I'm fixed wedge guy).

Bottom line, I think for the RV-10 AP yaw control adds little value.
 
Rudder wedge ...

I put on a simple 4 1/2" section of rudder wedge to correct my yaw, and it flies "feet flat on the floor" now. I certainly have no reason to make it adjustable.
 
I love my Aerosport Products rudder trim. Super easy to install and uses the entire rudder. A really good side effect is the rudder doesn't get banged around in the wind before you install the rudder gust lock. I don't install one if the winds are 10 and under. The Aerosport version uses springs so the rudder wants to stay centered in the wind.
 
Not only did I install the Aerosport rudder trim, I added some light springs to the rudder pedal the run to the firewall. I did this prior to Aerosport coming out with the spring biased rudder trim system. I also have a 2" wedge on the rudder. The combination of the two springs not only keeps tension on the cables in the tunnel, it also helps hold the rudder while you exit the plane to install the gust lock.
IMG_2642.jpg

I installed the Aerosport rudder trim adjustment on the panel to the right of the passenger warning placard. The control now comes engraved.
IMG_0074.JPG
 
Last edited:
JackinMichigan said:
My father and I will be installing Garmin G3X systems in our RV-10, and it's our understanding that they have built-in 3-axis autopilot capability. However, the servo install kits we bought from Aerotronics have provisions for the roll and pitch servos, but not yaw (rudder). We've been told by a few people that yaw servos are almost unheard of in single engine aircraft.

BTW - This is different from rudder trim. We plan on buying Aerosport's bolt-on trim system for that.

My father wants to Rube Goldberg in a rudder autopilot servo anyway, and I'm hesitant. How necessary, or even desirable, is a rudder autopilot servo on an RV-10? Will it improve anything, or is it a waste of time and money? I'm guessing if it was worth the effort more people would do it.
Click to expand...

You get essentially three axis by the co-ordinated use of the pitch and roll servos. Mostly the roll servo. Kinda like the way that a lot of CFIs are teaching their students today to not use the rudder controls to make a turn. :p (Unfortunately, that's not a joke). Same principle for three axis using only two servos.
 
I may be one of the few people who have installed the yaw damper on an RV-10. The owner insisted. While I did notice a small difference in flight, it was more of a slight stability improvement in rough air, but I only flew with it for a few hours. After installing it and seeing it's very limited usefulness, I fully understand the lack of a rudder servo on all of the other common experimental auto pilots. Don't waste your time or money, at least on the RV-10.
 
I installed the Aerosport spring system and love it. I rarely have to adjust it in cruise, but it's simple to do. It's such a minor issue in RV-10s.
 
Yaw changes with power changes. . .

I'm curious about yaw changes with power and airspeed changes in the -10. Currently I am flying a C-180A and that 'ball' moves with every change in power and airspeed. I'm getting from posts here that yaw change is very minor in the -10. True?
BTW Mike S, I like your rudder trim. I think I saw some drawings for the installation in the Forum, but I can't find them now. Where should I look?
 
The ball hardly moves at all, even in a turn. The yaw damper is not necessary. I have installed and flown one, and it did help a little in the bumps, but the -10 is plenty stable without it.
 
yaw

Yaw dampeners are used to control dutch rolls, not a problem with RVs. On large transport transonic aircraft they are a no go item if inop.
 
don't need rudder trim

To be honest I don't even need rudder trim. Its true that you will need a bit of rudder during climb especially with full power but given the climb performance and the time to put a bit of weight on the right pedal is no issue for me.
In cruise I can put my feet flat on the floor.

my 2c
Michael
 
The rudder trim discussion is interesting (I don't have it and don't need it), but it is confusing the question posed by the OP - whether or not to install an autopilot servo on the rudder. I believe the answer to this is a very clear no. No adverse yaw at cruise speeds = no useful function for a rudder servo.
 
The discussion of trim is out of place here; that's not what the OP was asking. I was considering the TruTrak Yaw Dampener for my Sorcerer AP but the servo installation is essentially a steering bar attached to the rudder cables in the aft fuselage using a cable clamp system (unless someone has re-engineered it in the past couple of years). Too much complexity for my liking. I've flown a couple of light singles (a Maule leaps to mind) that could do with a yaw system but my -6A is fine without it; I often fly cruise with feet flat on the floor (return spring system in that aircraft) so I expect the anecdotal evidence is true - little to no adverse yaw in normal flight.
 
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