I have a question for all of you aerodynamically inclined out there. I was wondering exactly how adverse yaw is possible? I just can't make myself see how when the rudder is pushed in one direction the plane moves in the opposite.[sm=spinnyeyes.gif]

adverse yaw is caused by the use of ailerons, and the rudder is used to overcome this. adverse yaw is more noteable at slower speeds. let's say you want to turn left. in order to do so, you roll your aircraft to the left until you have established the desired bank of your wings. once you have done this, you typically ease off the airleron pressure so the aircraft doesn't keep rolling.

ok, now when you first apply the aileron to roll left, making the right aileron moving down, and the left one moving up, it changes the angle of attack on both wings. The right wing, with the dropped aileron, is now creating more lift because the aileron has increased the right wings effective camber (curvature of the wing). Doing so has increased the drag on that wing, particularly what's known as induced drag. the concept of induced drag is hard to explain thru text without a diagram. to put it short, when lift is increased, so is drag typically.

so, when making the left turn, the nose of the aircraft may yaw to the right initially when applying left stick. in order to overcome this, you can apply some left rudder to swing the back of the aircraft out to the right, wich yaws the nose to the left and prevents the adverse yaw from ever happening.

Hope this helped... anyone else feel free to add/correct anything i've said.

Another fix is differential ailerons where the aileron going up has more throw than the aileron going down equalling the drag. this only works on flat botton or semisymetrical wings. Symetrical wings don't have adverse yaw unless very close to stall.

First, lift, by definition, is opposite to weight. Weight is down so lift is always upwards. I realize the layman’s definition of lift is the force produced by a wing and its direction is out from the wing. This is incorrect by the scientific definitions and it results in confusion as to how drag is produced by lift.

If you put your hand out of a car window when you are driving and deflect leading edge upward, you feel a force pushing your hand backwards and upward. The exact upward component of the force is lift and the backward component is the drag due to the lift. If you tilt your hand at a greater angle, you get more lift, but more drag is also produced.

When the ailerons are deflected, both wing panels are producing a force. The panel with the down aileron is producing more force than the side with the up aileron so you get a roll. The components of the force from the side with the down aileron are also greater than the components on the panel with the up aileron. This means the drag on the down aileron is greater than the drag on the up aileron. The result is a yaw toward the down aileron which is opposite to the direction you want the plane to go, hence the requirement for a small amount of rudder correction at the roll in to a bank.

From this it is easy to see that long wings produce more adverse yaw than short wings, scale Cubs, for example. Large, cut-in or barn door ailerons out at the tip produce more adverse yaw than do strip ailerons. A high-speed plane will need less aileron deflection to produce a certain roll rate than a slow speed one so the high speed one will produce less adverse yaw.