Adverse yaw

The effect can be greatly minimized with ailerons deliberately designed to create drag when deflected upward and/or mechanisms which automatically apply some amount of coordinated rudder.

As the major causes of adverse yaw vary with lift, any fixed-ratio mechanism will fail to fully solve the problem across all flight conditions and thus any manually operated aircraft will require some amount of rudder input from the pilot in order to maintain coordinated flight.

[1] Adverse yaw is a secondary effect of the inclination of the lift vectors on the wing due to its rolling velocity and of the application of the ailerons.

[2]: 327  Some pilot training manuals focus mainly on the additional drag caused by the downward-deflected aileron[3][4] and make only brief[5] or indirect[6] mentions of roll effects.

Thus, for the left wing of a forward-moving aircraft, a positive roll causes the oncoming air to be deflected slightly upwards.

Equivalently, the left wing's effective angle of attack is decreased due to the positive roll.

[2]: 365 As intended, the rudder is the most powerful and efficient means of managing yaw but mechanically coupling it to the ailerons is impractical.

Most airplanes use this method of adverse yaw mitigation — particularly noticeable on one of the first well-known aircraft to ever use them, the de Havilland Tiger Moth training biplane of the 1930s — due to the simple implementation and safety benefits.

Unfortunately, as well as reducing adverse yaw, Frise ailerons will increase the overall drag of the aircraft much more than applying rudder correction.

Contrary to the illustration, the aileron leading edge is in fact rounded to prevent flow separation and flutter at negative deflections.