joem423

Hi All,

I'm setting up a wing and think I have a problem. I have the servo, bellcranks, and airleron all attatched in the wing, but the up movement is about 5mm more than the down movement. I'm using the circular servo horn with ball links. The Airleron horn is also centered right on the hinge point. The setup is sound, smooth and with no restrictions or servo noise. I just can't figure out why there is a difference between the up and down movement. It is a flat bottom airfoil. Is this normal or will this effect my left and right turns? Is there a way to fix this?

Thanks in advance,
Joe

Hughes500E

My Feedback: (16)

Hi Joe,
Check your plans, the config you have described is slight differential. This is obtained by having the clevis' forward of the center point on the servo horn or bell cranks etc. Your plans may call for 1/2 up 3/8 down. You may have to increase this condition.
Enjoy

waynem

My Feedback: (58)

should fly fine like it is. Sometimes planes are set up this way, I would not do anything to but fly it this way. Wayne

saramos

This sounds like the ailerons are set up with differential. This means the travel in one direction (up) is greater than the other (down). The primary purpose of ailerons is to cause the plane to roll. The problem is that control surfaces have secondary control effects. With ailerons, the secondary effect is to cause the plane to yaw. Differential is often designed into the aileron controls to minimize unwanted yaw. When used to prevent unwanted yaw, differential is set up so that there is more travel on the up aileron than there is on the down aileron.
Check your plans and linkages. If all is right, then I would think the differential is by design.

Scott

Propwash in Pa

Great answers from a knowledgable group. I have a high performance glider that, by design, has quite a bit more down in the aileron travel so turns are made by more upward force on the outer wing, thus less loss of altitude. Seems to work.

aeajr

My Feedback: (2)

Normally the up aileon gets more movement than the down as the down aileron tends to create more drag and can introduce more adverse yaw.

The typical way to set up aileron dif on a sail plane is more up than down.

joem423

Hi All,

Wow, thanks for all the great responses. Yes, the Airlerons are setup exactly as the plans describe. No deviation from the linkages whatsoever. It must be by design. If the down movemet produces yaw, then that must be why. When I remember back, I have an F4 Phantom where the Airlerons only travel in the up direction, designed to do so by the computer radios of today.

Thanks a bunch,
Joe

aeajr

My Feedback: (2)

Yes,

Essentially the down aileron, while creating lift on that side also creates drag that wants to pull the nose toward the down aileron. If you are banking left and the plane wants to yaw right, this is called adverse yaw.

Using the rudder as part of a coordinated turn can help overcome this as well. That is one of the reasons we like to use aileron/rudder mix on sailplanes.

Some planes see more impact from this than others. I guess your F4 must have gotten a lot of adverse yaw from the down aileron.

As you said, it looks like the designers planned for this in the way they set up your linkages. Very clever. I guess they did not plan for a computer radio.

Not as important on power planes where the momentary drag can be overcome by the motor and is small compared to the power of the motor. But for sailplanes, where your total energy reserve is your momentum and gravity, this drag costs you valuable energy that might be significant compared to your total energy reserve.

Interesting trivia.

FLYBOY

My Feedback: (11)

This is exactly opposite of how it should be stated. As some others said, more up aileron than down is good on gliders.

As for your plane joe, don't worry about it. You don't have a problem. Probably don't have the bellcranks exactly 90 degrees, so you get more one way, or as someone else stated, if your horn is not right on the hinge line, that can cause it too.

no big deal, you won't notice it in the air.