I have a Thunder Tiger Stick .40 with a TT .46 Pro on it. It has been modified a bit with duel Aerilon servos, larger rudder and moved the elevator and rudder servo to the back.

In the past I have not used my rudder much but have been trying to use it more but with this plane the affect the rudder makes it difficult to use.

When applying rudder on level flight the plane gains altitude as if I am adding up elevator at the same time. Is is supposed to do this? What is the correct response of the plane when rudder is added at level flight. I do have a computer radio so I can do some mixing if needed. I thought about adding some down elevator when the rudder is used but will this have affects that are not desired? Thanks for your help

Some elevator (and aileron) coupling is typical when using rudder. Most people either mix it out with a programmable mix on their radio, or live with it and manually correct. If you added to the rudder, it probably made this coupling worse. Try putting a programmable mix on a switch, fly with it and tweak it to your liking, then if it works well at all speeds, make it permanent by setting always on. During testing, take the plane up, then flip the mix on and see if you're got it right. Turn it off, land, tweak & repeat. The reason I say this is up elevator & rudder is also an input for snaps & spins, so don't go overboard with it. Also try to set it up for mid throttle, you likely find that the mix isn't enough when going fast, and too much when going slow, or visa versa.

To me, the question is: Why are you applying rudder during straight and level flight? This basically makes the plane try to fly sideways. Learning to use your rudder is a good thing, but use it the way it should be used (IE to control the yaw axis of your airplane, not to turn with).

Remember, one of the reasons that the Wright Bros. were so successful was that they had wing warping (Ailerons) where everyone else was trying (with minimal success) to turn with rudder.

mgmoore7,

You said that your plane climbs when you use the rudder, but you didn't say that it banks. It doesn't sound like simple yaw-roll coupling to me. Is the rudder hinge line vertical? If it isn't, then rudder deflection can give a direct pitch effect, which would be worse since you enlarged the rudder. If your rudder hinge line isn't vertical, it might be a good idea to modify it so that it is. If it is already vertical, then I don't have any other ideas. Good luck.

banktoturn

It is typical of high wing planes like the Ultra Stick to climb, or pitch toward the top of the plane, with rudder especially during knife edge. You probably also get a pro-direction roll. Moving your CG rearward will help some, but you will need mixing to get rid of all of it.

As for using rudder in level flight, have you never done a flat turn?

My point was simply that the rudder is not used for turning. It is used to control the yaw axis. With all of the aerodynamic forces that come into play, to move your rudder and expect your plane to simply do a flat turn without any other movement (IE pitching or rolling) is practically unthinkable. And to try to couple other surfaces into the equation IMHO is just plane silly. You would be much better off learning to fly the plane correctly. What do I mean by that? Let's look at a similar type of question.

"Every time I bank my plane with the ailerons, the nose pitches slightly down. Should I couple up elevator into my ailerons to keep the plane flying level?"

Well, by doing that, the plane would not nose down as much, but the amount will vary depending on the weather conditions, speed, etc. And if you DO make this adjustment, what is going to happen when you try to do a roll? Do you say, "When I do a roll, the plane has a tendency to snap because of the elevator coupling. Should I uncouple the elevators for doing rolls?"

Flying an airplane means just that. FLYING it. Making it go in the direction you want it to go. If you couple your elevator to the rudder for flat turns, and then you do a knife-edge, the coupling might work against you. If you couple your rudder to your ailerons for coordinated turns, the rudder will work against you if you try to do a side-slip on landing.

The bottom line is simple. Learn to fly your plane so you can make it do what YOU want it to do WHEN you want it to do it. Do the "coupling" with your fingers instead of your transmitter. Too many people want to use the brain in their transmitters instead of the one in their head. Believe me, the one in your head it a billion times better. But you have to use it.

The reason that I noticed this is that I am trying to learn the hand coordination to use all four inputs at the same time. In the past, I have limited my imputs to just the ailerons, elevator and throttle. I started doing some level flight figure eights to just get used to using my rudder and elevator combined without input of the ailerons at all. That is when I noticed the pitching to the top

When the rudder is applied, it yaws the plane in the direction desired, pitches toward the top of the plane then it will bank the plane and then up elevator is added to complete the turn and then the opposite to level the wings. Of course when trying to practice using the rudder in this fashion it gets really difficult for me at this point to try to deal with the pitching to the top of the plane.

Maybe I am approaching learning to use the rudder incorrectly??

banktoturn, the rudder hinge line is vertical.

Thanks for your help.

I don't think it is a bad thing to practice turning with the rudder. If the aileron servo goes and you have no left hand coordination, you're in a tight spot. It's happened to me before and I was able to land the plane with rudder and elevator. I was at a fly-in with my combat ship. I'm still flying the plane today. I've seen others crash when the same thing happens.

I have a Sweet Stick 40 with the TT 46. The plane does have quite a bit of roll coupling. It also has a tendency to pitch up also. If you have a large surface and a lot of deflection, the drag will increase greatly up high as you apply rudder which may cause the plane to pitch up. Also as the plane banks with positive rudder, it will pitch up.

I can't do a single roll circle with my stick due to the roll coupling. At times you have to input near full rudder and you run out of aileron. My Ultrasport could do it. I also have to feed in almost full opposite aileron to hold knife edge with the stick. My Ultrasport held knife edge with very little aileron or elevator correction.

Take a look at a Cap's rudder and compare it to where your's is at. The high rudder will make it hard if you have a big surface and a lot of throw. Play with the rudder, it is the only way to learn how to use it. I've seen people practicing for pattern contests and I watch the slow rolls. Half of the people don't use rudder and the slow rolls aren't very pretty.

If your stick is like mine, you'll be able to hover, do slow rolls, multiple point rolls, snaps........just no single roll circles. It's a fairly fun cheap plane. I've had mine for 5 years.

My $.02

My .02,I agree with ED_ Moorman,I coordinate rudder with aileron on most all turns.
Have a goodun,John.

Practicing turns with your rudder IS a good idea. You never know when it could come in handy. But it is not the way a rudder should be used. By all means, continue to practice it, but don't expect your airplane to turn without doing some other weird things as well.

Now, if you want to learn to USE your rudder in a more appropriate fashion, I would suggest three maneuvers: 1 a stall turn. 2 a Knife Edge. 3 a Slow Roll. And 4 Side slipping a landing.

Side slipping is probably the toughest of the four, but it's the one that will be the most beneficial to your skills. Mastering this technique really comes in handy when you have to do cross-wind landings.

AQ500 & mgmoore7,

AQ500 makes a really interesting observation about the rudder increasing drag above the centerline. This seems like a feasible explanation for the rudder/pitch coupling. One thing that may reduce this is to make your rudder more symmetrical with respect to the centerline, by increasing its area below the center line. You may be able to extend it a bit lower, but you will probably have to make the rudder narrower at the top and wider at the bottom, like a lot of patter plane rudders. This should balance the drag out, and might mitigate the problem. Interesting experiment anyway.

banktoturn

Is the leading edge of your rudder vertical? Carl Goldberg had a neat trick incorporated into several of his rudder and elevator kits. He would sweep the rudder back. It not only causes yaw when deflected, it would also cause a pitch moment as well. I don't know, this might go back to the single channel days. I had a twin once. I had a swept rudder on it. That dang rudder nearly killed that airplane several times. Sticks in the corners, and still climbing and slowing! Not good! The pitch moment caused by a swept rudder is definitely noticeable.

Good aerobatic models do turn -with rudder - -it is a flat skidding turn tho - Any good one will do large skidding circles -with little input other than , typically some elevator -
Finishing a rolling circle - there is typically some rudder skidding added to get the circle to finish on target -
The judges may not see it - but it's in there .
Practice your rudder turns - get used to flying with all inputs -mixed in all the ways you can think of - -try extremely hard rudder turns -then find out how much aileron and elevator input is needed to hold it.
All good practice techniques.