when executing a turn on a standard aircraft, will I need to use rudder with the ailerons? or is it ok to just use ailerons. Should I use a Y-harness?
Please answer this quesion regarding both single and twin-engine models..
Thanks for any help.

You can make a turn using only ailerons, but it would be a gradual turn with a fair amount of "slip"; it really depends on the plane as to how well it will turn using only ailerons; this goes for models as well as full-scale. A Cub, for instance will sideslip, and the tail will tend to drop to the inside of the turn (adverse yaw) if there is no coordination of rudder with the ailerons. A plane with greater dihedral will tend to turn better using no rudder than one with no or very little dihedral. It's always best to learn how to use the rudder, and to learn to coordinate it with ailerons in a turn. If you're going to fly a tail dragger, it's mandatory to know how to use the rudder in order to take off and land.

As for a Y-harness, sure, it's fine to link your aileron servos to one channel. If you have a computer radio and want to program in differential (put more "up" movement than "down" movement) to decrease adverse yaw, then you have to put the aileron servos on different channels. On my 9C, it's channels 1 and 7. The reasoning behind differential is this: the aileron moving down creates more drag than the one moving up, so it slows that wing's travel through the airstream, causing the plane to yaw to that side slightly. Since this side is the high side, and the plane will normally be turning to the low wing side, the plane is yawing opposite to the direction of the turn. Setting the ailerons so there is less "down" travel creates less drag on that wing, creating less adverse yaw.

On twins, they will tend to turn "better" to the left due to engine torque and P-factor, but the same generally goes for twins as singles as far as using rudder, just more of it in a right hand turn. Some guys will mix the throttle to the rudder, and when a turn is initiated and rudder is input, the "inside" engine will throttle back slightly to assist in the turn. As an interesting aside, in the P-38, which had counter-rotating engines, it did not have the tendency to turn tighter one way than the other, but at high power settings and in combat situations where high speed, tight turns were needed, the pilots developed the tactic of pulling back on the inside engine throttle to help them turn: the -38 could not otherwise turn as tightly as the Focke-Wulfs and Messerschmitts. The downside to using the throttle in tight turns was putting the plane into a usually unrecoverable flat spin if the pilot didn't watch himself.

Just in case you were asking, you can Y your aileron and rudder servos together, but it limits your plane to simple maneuvers, and will not allow you to coordinate your turns, although this is not a big concern for most RC planes.

Phoenix19:

As I see it, your definition of "standard aircraft" is a 4 channel RC model that has ailerons, rudder, elevator, and throttle.
An RC model that has ailerons generally has only 2 degrees or less dihedral angle. (Of course there are some exceptions).

"When EXECUTING a turn, will I need to use rudder with ailerons?" Everone has a different opinion of this - my opinion is NO, you do not NEED to use rudder with ailerons, but you can if you want. Don't let words like adverse yaw bother you; it is a transient effect and it is visible if you are in the cockpit, otherwise it is hardly perceptible from a modelers point of view (unless you're flying in competition).
"or is it ok to just use ailerons?" - my opinion YES, as does many other flyers.
"Should I use a Y-harness" You can if you are not planning to do much aerobatics or crosswind landings. If you do use a Y-harness, then you need to desensitize the rudder so that it deflects only about 1/3 when the aileron is fully deflected.

Others will tell you that you have to learn to use the rudder - I agree with that, but that was not your question.

The above holds true for both single and multi-engined airplanes.

feihu

It really depends on the design. Hot sport models will and usually do fly with just aileron and elevator input and look fine. As the speed lowers, like for landing or during very slow flight, some rudder added in with the left thumb will help smarten up the response and also help to avoid a tip stall.

Other models that use higher aspect ratio wings and/or have higher camber wings will benifit from coordinated use of rudder and aileron. Gliders are one good example and some other scale models gain a lot from some coordination as well.

But in all cases the amount of the mix changes with flight speed and intent. So learning to deal with it is part of the skills you will aquire. So stick with independent controls.

No -- not unless you have a computer radio -- best done through the dual rate switch (so you can enable-dissable the link) the & programmable throw percentages. You will need only a small amount of rudder input to coordinate turns & with a non-programmable Tx the Y will give you a 1:1 ratio of rudder/aileron. That can only be varied by the mechanical set-up of the rudder & aileron linkages -- aside from surviving the set-up flights, if you do that you will greatly reduce rudder effectiveness when you really need it. Additionally, the fixed linking of rudder & ailerons will prevent seperate use of either rudder or aileron that may be necessary in various flight evolutions.

All-in-all a bad idea.