Adverse yaw question

[bad3ip420]

Guys I need some help.

So Induced drag is a byproduct of lift. It increases as AoA increases(Cl increase)/speed decreases. The total reaction tilts backwards and increases the horizontal Cl which is the induced drag(manifest as vortices).

Now during turns, the wings produce more profile drag because of aileron deflection and the higher wing more induced drag. I've read that this is because the higher wing has more camber when the aileron is deflected downward. But isn't it the same case for the upward deflected aileron (lower wing)?

The upward deflected aileron also changes the orientation of it's chordline and it's camber(lower surface) also increases so there is also more induced drag due to high aoa/more negative lift. I've also read at another source that the higher wing has a higher aoa than lower wing (different relative wind positions?) causing it to have more induced drag and this is the one that makes more sense than that higher camber thing.

Sorry for the long post and I hope that you guys can shed some light on this.

Thank you!

[dixi188]

Hi bad3ip420,
The down going wing is not experiencing negative lift, just less positive lift, so less induced drag, (unless we are talking about full aileron deflection or aerobatic aircraft).
Hope this helps.

[bad3ip420]

Hi bad3ip420,
The down going wing is not experiencing negative lift, just less positive lift, so less induced drag, (unless we are talking about full aileron deflection or aerobatic aircraft).
Hope this helps.

Oh i see. So if it's still positive lift, what is exactly is the purpose of the upward deflecting aileron if it isn't to produce negative lift(chord line angled downwards)? And why does lower wing produce positive lift even if aileron is deflected upwards? Is it because of the AoI?

Thx

[dixi188]

Lets think straight and level.
Lift is equal both sides.

Now turn control a little to the left, lift (in the area of the aileron), on right wing increases, and on left wing decreases.
Turn a bit more and lift on right increases more and decreases more on left.
Keep turning the control and eventually the lift on the left wing may become zero and then negative, but will never be as negative as the right is positive, so the induced drag will be more on the right and hence the adverse yaw.

This is a simple explanation but should help.

[John Farley]

Chaps

You are straight and level and want to turn left. You put the left aileron up a little and the right aileron down. This slightly reduces the overall lift on the left wing and slightly increases that on the right. This imbalance makes the aircraft roll to the left. As soon as you get the bank angle you want you centralise the controls and the roll stops.

During the time the ailerons are not neutral the side with the down aileron has more drag unless the designer has used one of the tools at his disposal to keep the drag equal both sides when the ailerons are deflected.

[bad3ip420]

Oh! I think I understand now.

So the upward aileron is just disturbing the streamline airflow on the lower wing hence the less lift production and the downward aileron which increases the camber and the effective aoa hence the increase lift/drag?

[Chesty Morgan]

Not so much disturbing the airflow but reducing the camber of the wing, reducing alpha and, therefore, lift.

[John Farley]

Thank you Chesty!

Exactly

[bad3ip420]

Thank you everyone!

It was actually so simple. I can't believe I was giving too much meaning on it. :P

[wanabee777]

And then there is the B-52 which doesn't have ailerons.

[dixi188]

"And then there is the B-52 which doesn't have ailerons."

So we could move on to Roll Spoilers, Tailerons, Flaperons, Differential Slats,
Wing Warping, Ruddervaters?, etc.

[Sir George Cayley]

Some of the aeroplanes I've flown have turned better with a varying degree of boot full rudder leading the aileron input.

Secondary effects and all that.

SGC