Left roll and right roll not the same.
 

When I do an aileron roll to the right, the roll is very axial but when I aileron roll to the left it is sort of a cork screw. Why is that and what is the fix?
Thanks.

My guess is that you have unequal aileron throw from side to side. What I do is break down the ailerons into 4 quadrants. Up and down, right and left. Then I go into the ATV for the aileron and the aileron 2 and adjust the ATV of both channels until I get exactly the same deflection in all 4 quadrants. After that I throw in about 4-5% differential.

Thanks for the reply speedracer. I will check the throws on each side and try to get them equal.

Mike

I will assume equal throws of right and left ailerons. It's pretty common to have a slightly different response right from left roll, if the model is driven by a single prop turning ccw when viewed from the front, has right thrust and downthrust. The fix is a small amount of differential (more up than down aileron) but learning when to push and pull elevator is a huge help.

Another issue that can happen is that the roll rate will differ right from left. The fix in this situation is a small increase in deflection on the slow side.

BTW- a contra rotating propeller(s) cures these issues. A contra does not cure motor torque tho, unless each prop is driven by its own motor which in turn rotates in opposite directions

Thanks Matt. I'm pretty careful to set up each wing servo so that the angle between the horn and pushrod is at 90 degrees. I assumed this would give equal throw to the ailerons. I will experiment adding a bit of differential and using some up/down elevator on the cork screw side to see what effect it has. Not all, but some of my planes has an axial roll one direction and somewhat corkscrew the other direction. I was curious as to why that was happening.

Mike

Mike, please do check the ailerons. What I have seen is that most guys setting up dual servo aileron setups will adjust ATVs at the same percentages with the same length servo arms and control horns expecting it to result in equal throws. Seldom does that work out. Most guys never realize the loss of performance. Taking the time to balance all the throws and adding the correct amount of differential will help. That being said getting an airplane to roll exactly the same both directions is probably not going to happen. I know for a fact that I roll better to the right then to the left. This is because right is my dominate roll direction even though I do a fair amount of pylon racing and my dominate turn direction is left. Once the airplane is set up well it becomes a matter of practice.

I think you are correct speedracer. I assumed with the ATV's the same, 90 degree control arm to servo orientation, the ailerons would mirror each other. Apparently that is not always true. I will do some differential adjustments and see if I can minimize the corkscrew side even though it isn't horrible. I just hoped the plane would roll either direction the same way. Probably a little more practice on my part would improve the situation considerably.

Mike

Your rudder could be trimmed to favor one side.
You might not notice it in normal flight. If you are
accustomed to flying with both thumbs, you will
find yourself correcting more on one side in low
speed turns.

Spiral slipstream could also be a factor if there
is not much fin/rudder area below the elevator
(such as elev/stab mounted on the bottom of
the fuselage). Right thrust if there is any, will
tend to negate the spiral slipstream.

Uneven lift (up on one side more than the down
on the other side) is the most likely cause.
Flat bottom wings will need more up aileron
on one side to equal the down aileron plus
wing camber on the other side. (Another
reason to use differential besides adverse yaw.)

Mostly this will make it corkscrew both directions,
but if one wing is twisted or the aileron linkage
is off center such as from trimming to compensate
for the off center rudder, the corkscrew will
be more pronounced on one side.

Finally, exhaust blowing over the wing on one
side can increase the lift of that wing more than
the other side. It is not much, but will add to any
other causes.

To piggyback on what Jennifer Curtis said, with all of the non-symmetrical forces present, maybe non-symmetrical aileron throw is a good thing.

Kurt

G'day Mike,

Are you a mode 2 flier? Sometimes it's very difficult to make a 'pure' aileron input without putting in a small elevator input as well, and it's different left and right. It's because of the way your thumb sweeps left and right. The elevator input can give you the cork screw roll that you are seeing.

Might not be the issue but something to think about if you can't find any other issues with your ailerons.

Dave H

Yes, I'm a mode 2 flier but not thumbs only. I prefer thumb and index finger on each stick. I have dialed in some differential and it has made a nice improvement to the rolling being more axial to the left than it was before. The plane rolled right just fine but the left roll had a bit of corkscrew to it. I've never used differential before and it seems to work pretty well. I have one other plane I going to dial some differential in to.

All of the comments were appreciated everyone.
Thanks
Indiomike