Auto pilot problem

At 35 hours or about now and I finally had the time to connect up and test the ADI II. It is working OK but........

The background is that there is still a slight tendency to roll left at cruise and at this stage I am fiddling around with a fixed rudder trim, taped onto the LH side of the rudder close to the trailing edge. So at cruise you need slight right rudder pressure an neutral aileron to make it fly nicely straight and level.

Hit the the "Track" button on the ADI II and the AC immediately goes right wing low with half a ball out to the right but seems to keep the track well.

Spoke to another RV10 owner with a different auto pilot and he has the same problem. Me thinks it might go away when I have fixed the left roll tendency but will welcome advise.

Yep

Mine does the same thing, Jan. The -10's don't have any offset in the vertical fin, so a trim tab is needed. The low wing is normal with a ball off-center...try centering the ball with rudder pressure and the wings will be level. The low wing is compensating for the airplane's turning tendency.

Best,

Sounds like what you really need is rudder trim.

In fact the Boeing cruise trim procedure is to engage the autopilot in Heading Hold mode, gradually trim the rudder until the WINGS are level, then disengage the autopilot and use aileron trim to eliminate the control pressure required to hold wings level, then re-engage autopilot.

Seems counter-intuitive to use rudder trim to level the wings, but when the autopilot is holding a heading, as Pierre states, it will do whatever is required to hold that heading, and in the case of the ball not being centered, it will slightly lower a wing to hold the heading.

Trim Tab

Absolutely on target. Had same issues on my build and I corrected it with a very small trim tab. Required a very, very small adjustment.
Randy Means
N595RV
2010 completion

On my RV-6A

I built it with no intention of installing an autopilot. I taped on the commercially available rudder wedge and it turned out the stock size was right for our plane. Later I learned how demanding an RV can be on long cross country trips especially under IFR. I talked to Jim Younkin and bought a Pictorial Pilot and Altrak and love them but in level cruise flight the ball was about half out of the center. I race the airplane and I do not want to give up speed by letting the ailerons over control the rudder for proper track. I tried the spring loaded rudder trim system and didn't like it, then I installed a removable ground adjustable metal tab of my own design to replace the wedge. Now the ball is centered in level flight, the speeds are good and all is well in the pilot's mind. I do not actually have any test data to prove it is faster than it was with the wedge.

Bob Axsom

So Bob are you saying that a fixed tab is better than the wedge?