flyinrazrback

My Feedback: (69)

I have a question about dual receiver setup using a Futaba 9CAP and 2 149DP receivers. My question is the aileron setup. What is the best way to set it up? I want to use the left rx for the left, and right rx for the right. I plan on using channels 1+7 for the aileron differential function. So should I Y harness each side and run the left 2 ailerons to a Y harness, and then to Ch 1 on the left, and the right side connected to the right rx with a Y harness and them connected to Ch 7. Or should I not use a Y harness in either wing and run one servo from the left panel to ch 1 and the other to ch 7 on the left receiver, and do the same to the right side? just looking for simplicity and how everyone else sets theirs up.

dirtybird

My Feedback: (5)

I don't see why you need channel 7.
Left receiver channel 1 with y harness two left aileron servos.
Right receiver channel 1 with y harness to two right aileron servos.
Unless you plan on doing diff control or want to convert the ailerons to flaps. Then things get a little more complicated.

sfaust

My Feedback: (11)

I connect all the left aileron servos to a Y connector, or a matchbox, then into channel 1. I do the same for the right side, then into channel 7. For two servos on each aileron, a Y connector would be fine. If I were using three servos per aileron, I'd opt to go the matchbox route for more precise control over each servo. Running two separate channels is good since you have the ability to setup your ailerons more precisely, as well as introduce aileron differential. This becomes important if you are setting up an aerobatic airplane, and will be dynamically flight trimming your airplane.

Running the two servos to independent receivers is easy, but it does have some bad attributes to it. If you run one left aileron servo to channel 1 on receiver 1, and the other left aileron servo to channel 1 on the second receiver, what happens if one of the receivers fail, and/or goes into failsafe. You will end up with one servo trying to push, and the other trying to pull. You would loose control of that aileron, and setup a very high current drain in the power system. This has the potential of dropping the current level below the receivers operating range, thus shutting down the receiver. Would it happen, possibly, but in all honestly its probably remote. But, its not an issue if you run both servos to the same receiver.

sfaust

My Feedback: (11)

Oh yea, another thing to keep in mind regarding multiple servos on a single surface when using multiple channels, such as using two channels to operate your rudder servos. You need to make sure the mixes you use include trim adjustments, as well as the effects of any other mixes. Ie, if you don't setup your mix properly, you could add in some knife edge mixing, and that mixing would only affect one servo, and not all the servos. You would have one servo binding against the others. Same with using the rudder trim. If you trim the rudder channel, but the other channel that you are using for the rudder does not act on the trim changes, you will be trimming in binding on your servos. I bought a plane that didn't have the trim linked, and eventually a rudder servo failed and I almost lost the airplane. I stumbled across the programming problem while trying to diagnose why the rudder servo failed in the first place.

Just a FYI in case some are not away of the issue with using dual channels for a single surface. This seemed like an appropriate place to mention it.

hilleyja

My Feedback: (3)

That's exactly why you want to use channel 1 & 7 -- for differential control, i.e., airlon moves less on the down swing vs the upswing. If you want flaps (FLAPERON) you would normally use channel 1 & 6. With the Futaba 8AU and 9C there is virtually no complications, used the radio's available FLAPERON, DIFERENTAIL functions.

dirtybird

My Feedback: (5)

I have to admit I am not a hotshot aerobatic pilot but I don't understand why you would use differential ailerons on an airplane that has a symmetrical airfoil. What happens when you are upside down?

sfaust

My Feedback: (11)

A symmetrical vs a flat bottomed isn't really the issue, but more the adverse yaw created by the ailerons. Using aileron differential is a way to balance this, and negate the adverse yaw. Other ways involve the aileron design. Even on high performance airplanes (Extra, Cap, Giles, etc) with symmetrical airfoils, still suffer from adverse yaw. Most pilots use aileron differential to mix it out, and experiment with different settings until the tail remains straight and true on rolls in the vertical and horizontal planes.

Here are some links to help explain this.
http://www.aerospaceweb.org/question...cs/q0045.shtml
http://www.mountainflying.com/adverse.htm
http://www.av8n.com/how/htm/yaw.html...ry-adverse-yaw (by the way an excellent site)
http://www.faatest.com/books/FLT/Cha...fferential.htm

dirtybird

My Feedback: (5)

I admit I didn't read all of the references but the one I did read still leaves me with the question of what happens when you are upside down? If you have diffrential ailerons it seems it would not work.

Geistware

My Feedback: (16)

In running the servos directly from the receiver, he will be able to offset any binding electronically. THat is the benefit of what he wants to do.

dirtybird

My Feedback: (5)

How do you offset binding electronically?. If you have binding in your linkage it seems to me it will happen no matter how you drive it.. If you mean the limits maybe you should fix the mechanical problem.

sfaust

My Feedback: (11)

I agree with DirtyBird. If the two servos were connected to the same surface, and he used a separate channel for each servo, you could use the two channels to eliminate the binding. Thats what many do on the rudders. But, he is using two servos on Ch1, and two servos on Ch7. There is no way to electrically correct binding issues, as the control surfaces are independent, and the servos and linkages are bound electrically.

I can't explain why the aileron differential doesn't seem to matter whether its upright or inverted. But I can sure see the different when the aileron differential is setup properly on an aerobatic airplane, and when its not. When not setup properly, you can see quite plainly the tail yaw during rolls started upright, inverted, upline, downline, and 45's. When its finally dialed in properly, the yaw is cleaned up in all those areas.

Check this one, in section 8.8.3, and 8.8.4, regarding Steady Adverse Yaw/Twisted Lift. It seems to suggest that its the rolling motion coupled with the drag and lift components that sets the yaw. This might explain why it doesn't matter whether its inverted or upright. But, I really don't have the answer, I can only attest that setting up aileron differential does indeed fix the adverse yaw issue.

http://www.av8n.com/how/htm/yaw.html...ry-adverse-yaw

Crash90

My Feedback: (17)

I just did a dual Rx setup with the 9CAP. Left wing. 2 servos connected with a Y and ran to channel 6
Right wing, same thing but used channel 1

Enabled the flaperons.