Skid (aerodynamics)

In a straight flight, the tail of the airplane aligns the fuselage into the relative wind. However, in the beginning of a turn, when the ailerons are being applied in order to bank the airplane, the ailerons also cause an adverse yaw of the airplane. For example, if the airplane is rolling clockwise (from the pilot point of view), the airplane yaws to the left. It assumes a crab-like attitude relative to the wind. This is called a slip. The air is flowing crosswise over the fuselage. In order to correct this adverse slip, the pilot must apply rudder (right rudder in this example). If the pilot applies too much rudder, the airplane will then slip to the other side. This is called a skid.