Tiny Trainer aileron rolls left wierd

[nhk750]

I only started flying last September and I have 11 hours, 40 minutes of flight time and 4.5 hours of that on my TT scratch build. I keep a very accurate spreadsheet that I made. I feel that I'm becoming a solid pilot and rarely crash with solid good landings. I have six operational planes with one float plane too.

Anyway, I use the TT to practice aerobatics and try to refine stunts. The problem I'm having is the TT will aileron roll in one direction perfectly, but the other direction it will almost pull a 90 degree turn when exiting the complete roll and also dive at the same time. It might be me on the sticks, but my other planes dont do this, so? Otherwise the TT flys nice and level with no strange other issues. Possibly aileron differential of some sort?

 

[TexMechsRobot]

Could it just be the torque of the propeller?

 

[Konrad]

That is very possible it is diff. Look for warps (twists) in the wings. Have a close look at your linkages. Even after trimming they should be adjusted to look close to the same. Can you post a detailed photo of the linkages?

Are you aware of this chart. I use it all the time in my trimming.
http://www.wtp.net/DBEST/trimchrt.html

 

[RCMAN]

It could be P-factor, also on the 4 channel setups with a Y-harness on the ailerons, the servo arms dont exactly match up as your servos are reversed to each other on the wing in the neutral position. Make sense? In other words, one arm may be at a different position than the other, in the center position, and it will affect the geometry when rolling in each direction. With more channels you can center the servos better and have more control. At least I make sense to myself.

 

[Konrad]

It could be P-factor, also on the 4 channel setups with a Y-harness on the ailerons, the servo arms dont exactly match up as your servos are reversed to each other on the wing in the neutral position. Make sense? In other words, one arm may be at a different position than the other, in the center position, and it will affect the geometry when rolling in each direction. With more channels you can center the servos better and have more control. At least I make sense to myself.

Plus one!
This is a big issue with entry level servos.

 

[nhk750]

Yup, they dont line up in the center position, just like all the cheap servos I have when the are oposite each other. I have actually adjusted that with my 6 channel RX's and not using y cables on my other planes. Makes sense, I didnt think it mattered all that much, but I guess it does!

 

[Konrad]

Before going to the sub trim menu try rotating the star or cross wheel close to 180°. Often time the spines in arms are indexed out of position with the arms. This allows for some fine tuning of the mechanical geometry.

A detail photos would help. And as you are finding out, solid mechanics is just as important as placement of the center of gravity, for nice controlled flight.

 

[Hai-Lee]

Try doing your aileron rolls with the throttle cut in each direction and if they are similar then the problem is motor torque/P factor if the problem persists then it is your control surface setup.

Ensure that your control surfaces move equally and that your control horn placement is identical on each surface. one horn being a different distance from the hinge line can give weird roll responses.

Finally ensure that your control surfaces flex equally and that one is not "Softer" than the other. A "Soft" aileron will tend to flatten out under the pressure of the airflow and therefore become far less effective.

Just a few thoughts!

Have fun!

 

[nhk750]

Pictures

Here are some pictures of the servos out of alignment. It dawned on me, after reading the replies on this post, that I can just adjust the sub trim until the servos are facing the same direction, then loosen the rods and move the ailerons to the neutral position.

So far, this plane has the most hours on it than any other plane I own, and it is holding up great!

 

[PsyBorg]

Another thing to check.. ask me how I know... is the balance of the wing. I am not sure how much difference it will make in that size plane but on my Baby Baron just a touch more glue on one side then the other made a HUGE difference.

 

[nhk750]

Just took it for a test flight In the field next door and wow, what a difference! It rolls the same way now both directions and fly's way more predictably. It is hard to believe that the little difference between the angle of the servo arms can make a difference. Maybe Flight Test should update their videos with some of the tweaks like that to make planes fly better. Thanks everyone for getting my mind to wrap around this adjustment.

 

[hogtownjon]

Hi nhk750,

Just to learn from this also would like to clarify how you fixed it.

If i understand correctly, The angle of the arms of the servos with no trims was slightly different on each aileron. So instead of the y harness you split the channels in order to adjust subtrim for an individual servo? Havn't tried mixing for ailerons but do you set one servo on aileron and the other on aux and then mix aileron to aux at 100%?

Thanks!

 

[RCMAN]

Hi nhk750,

Just to learn from this also would like to clarify how you fixed it.

If i understand correctly, The angle of the arms of the servos with no trims was slightly different on each aileron. So instead of the y harness you split the channels in order to adjust subtrim for an individual servo? Havn't tried mixing for ailerons but do you set one servo on aileron and the other on aux and then mix aileron to aux at 100%?

Thanks!

He explained it. He left it 4 channel with a y cable and just used the sub trim on the tx until both arms are at the same angle, then adjust the control rods so the ailerons are nuetral again. I do this on my little 4 channel planes all the time.

 

[nhk750]

Rcman is right, when you trim it they will move in opposite directions, then just adjust ur rods.

 

[Hai-Lee]

When I build that very special plane and want the controls to be as exact as I can get I either use the Servo output disk or make a plywood servo arm flag, (screwed to the servo arm) and carefully mark and drill the holes I want in the output disk/flagged arm, of the servo to give me identical though mirrored servo output position for my pushrods.

It is a great and simple way to get balanced ailerons/elevons with proper differential for performance accuracy in roll.

Just what works for me!

Have fun!