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Old May 05, 2012, 11:15 PM
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United States, CA, Livermore
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Question about aileron rudder mix function

This is my first time trying to use aileron and rudder mixed with my radio. I used the mix function on my Spektrum DX7s radio and the resulting control surface directions are as follows:

I move the aileron stick to the right and the right aileron moves up and the rudder moves slightly to the left. Are these the correct directions for mixing these two functions? My initial thought would be that the rudder would need to move right when giving right aileron but I wasn't sure.
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Old May 05, 2012, 11:28 PM
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United States, OH, Tipp City
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You want the rudder to move to the right in this case. You want the rudder to move towards the same direction as the bank you are inputting. Right bank, right rudder. Left bank, left rudder.

Two things can cause the results you are getting:

1. Your rudder servo is operating in the wrong direction to start with. What does it do when you move the rudder stick to the right? does the rudder move to the right? If not, then that servo needs to be reversed in the transmitter. Then your mix will work the way you intended it to.

If that is operating correctly, then:

2. You are using a negative percentage for your mix. If you crank the percentage up to a positive number, your mix will work the way you intended. (or vice versa. Sometimes, the negative/positive doesn't necessarily mean anything, you just need to roll the scroll button one direction or the other to get the desired results).

Hopefully that all makes sense...ask again if it is still confusing.
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Last edited by aero550; May 05, 2012 at 11:43 PM.
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Old May 06, 2012, 03:33 AM
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why do you want to do this?
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Old May 06, 2012, 09:58 AM
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United States, NM, Albuquerque
Joined May 2004
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Quote:
Originally Posted by Threshold View Post
why do you want to do this?
+1

IMO, mixes of this kind should be used to correct a control coupling issue like in KE flight. EG: if the plane rolls in or out of KE when rudder is applied a mix from rudder to ailerons can be used to correct this.

If you are thinking about using a mix to "help your model turn faster" by mixing in a "coordinated turn" then its probably a BAD idea...Doing this creates a crutch that will keep you from becoming a better pilot, Its an old rumor that this is hard and or takes years of practice to learn... typically spread by pilots that don't want you to be better than them.

Is there another reason you want to use this mix on your model?

PS. depending on which direction you set the mix up + or - will determine the direction of the rudder or slave channels movement.
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Old May 06, 2012, 10:21 AM
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I use rudder/ileron mix most of the time for relaxed flying of high wing scale models. I can switch it off or override it (give extra rudder throw) when needed or desired. Aileron/rudder mix counters "adverse yaw" where the down-going aileron makes drag on that wing which fights turning in the desired direction. It is good to practice manual coordination of rudder and ailerons for use in aerobatic maneuvers or general flying. Use of "differential ailerons", where ailerons go up a lot and down very little is another way to counter adverse yaw and make turns easier and smoother. Differential ailerons requires two aileron servos connected to two channels and programmed mixing. Aileron/rudder mix is a nice feature to have available if you want to use it . Comes in handy for landings and takeoffs as well as graceful turning with aileron-equpped planes. Ercoupes used coupled ailerons and rudder for easier and safer flying. Tricycle landing gears are a real "crutch". GPS is another crutch. Electric starters on cars and motorcycles were called "crutches"
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Old May 06, 2012, 11:46 AM
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United States, OH, Tipp City
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The OP's question was about whether his mix function was working or set up properly, not about whether he should be "allowed" to use it or not. That would be a debate for another thread.

I could see using this mix to get a nice scale model around the circuit in a safe, secure, easy manner. On the other hand, this mix would corrupt the handling of a full-on aerobat. It all depends on what you are trying to accomplish, and that is totally up to Riodiler.

That is why this hobby is great and cursed at the same time. We have the freedom to do it the way we want...but tend to have a lot of people telling us why we are doing it wrong.
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Old May 06, 2012, 11:51 AM
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Quote:
Originally Posted by aero550 View Post
That is why this hobby is great and cursed at the same time. We have the freedom to do it the way we want...but tend to have a lot of people telling us why we are doing it wrong.

Sooooooooo true
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Old May 06, 2012, 10:29 PM
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United States, VA, Fluvanna
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I've never noticed a need for mixing rudder in with ailerons. But I have considered mixing opposite aileron with rudder to prevent the inside wing from lowering during turns. For now I do it manually after the turn is complete. I'd like to be able to do it during the turn but I always give too much...
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Old May 07, 2012, 12:38 AM
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High wing models definitely need rudder input along with aileron deflection, either manually applied or using aileron/rudder mix. Low wing models i.e warbirds and sport models, generally turn well with aileron and elevator inputs, rudder inputs are optional. During landings, ailerons become ineffective at low airspeeds but rudder remains effective for keeping wings level.
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Old May 07, 2012, 01:32 AM
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My SE5a needed rudder input along with ailerons to turn correctly and I'm glad I have a computer radio to help me. Without it it seemed like the tail wanted to drop and fall out of the sky. I use whatever helps me have a good experience. I like having a gyro on the rudder of my H9/P-51. I use it for takeoffs, gear up and gyro goes off.
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Old May 08, 2012, 02:36 AM
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Well the OP was clearly confused about this asking about the direction of the rudder deflection so before going into long winded discussions about the idea I thought it wise to ask him why he wanted to do it? It seems it was just on a whim as he has not bothered to look at the thread again instead leaving us all to argue about the merits of the idea.
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Old May 08, 2012, 06:35 AM
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Rudder Aileron Mix

Quote:
Originally Posted by Threshold View Post
why do you want to do this?
I have a 3 channel easystar and feel more comfortable using the aileron control for rudder. On 4 Channel I use the Ailerons most of the time so i dont need to rewire my brain.
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Old May 09, 2012, 07:53 AM
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Yes but I was asking the OP. There are many reasons for coupling aileron to rudder. By finding out what he was after a better answer could be given even if it meant it was not a good idea for him in his case.
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