“adverse”- acting in the opposite direction, opposing.

A bane to pilots and aircraft designers, perhaps behind only drag, weight, and the desire for better climb rate, is adverse yaw. This tendency to initially yaw in the opposite (adverse) direction of the aileron input (and the intended turn direction) means that the vast majority of rudder inputs must be in coordination with the ailerons. Thus the term “coordinated flight”.

The down aileron increases the camber of that section of wing, while the up aileron on the inside of the turn serves to reduce the effective camber. Increasing the camber of the outside wing results in a higher CL (coefficient of lift) resulting in that wing raising, while the lowered coefficient of lift on the inside (raised aileron wing) means that wing will lower. This results in the bank angle needed for a turn.

The negative side of the increased coefficient of lift on the outside wing is more induced drag, which retards that wing, yawing the plane away from the bank.

The pilot can make a banked turn using ailerons only, but it will remain yawing (slipping) as long as there are deflected ailerons. The ball will be to the inside of the turn.

Aircraft manufacturers have helped offset adverse yaw by having differential aileron movement.

When the yoke or stick is moved to the left, the left aileron travels farther up than the right aileron travels down. This is shown in the document known as the Type Certificate Data Sheet, which has limitations and control rigging maximums and minimums for a specific model aircraft. [If you wonder which model of the Cessna 172 changed from a maximum of 40° of flaps to 30°, it will be found in the TCDS for the Cessna 172 (it was between the 172N and the 172P. Model 172O was probably not used, since O – “oh” is so similar to 0 -“zero”)].

The aileron deflections for the 182Q are:

Up: 20° (+/-2°)

Down: 15° (+/-2°)

Lest you think this is a Cessna only thing, the Diamond DA-40 TCDS shows aileron movement as:

Up: 20° (+/-2°)

Down: 13° (+2°, -0°)

The result is that your aileron input to start the turn gives more lift reduction on the inside wing than lift (and induced drag) enhancement on the outboard wing. Less rudder deflection is required than if the deflections were equal. 

Note that when you’re in the traffic pattern you need more rudder deflection to keep the ball in the middle. Induced drag is higher and the rudder is less effective at these lower airspeeds. 

Photos: the aileron deflected up (left bank) to its maximum is about 3″, while down (right bank) is only about 2.5″.