Adverse yaw

Adverse yaw is the natural and undesirable tendency for an aircraft to yaw in the opposite direction of a roll. It is caused by the difference in profile drag between the upward and downward deflected ailerons, the difference in lift and thus induced drag between left and right wings, as well as an opposite rotation of each wing's lift vector about the pitch axis due to the rolling trajectory of the aircraft. The effect can be greatly minimized with ailerons or other mechanisms deliberately designed to create more drag when deflected upward than downward 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.