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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 lift and drag of each wing. 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 rudde
Adverse yaw moment is basically countered by aircraft yaw stability and also by the use of differential aileron movement. [39] The Frise-type aileron also forms a slot, so air flows smoothly over the lowered aileron, making it more effective at high angles of attack. Frise-type ailerons may also be designed to function differentially.
The rudder may also be called upon to counter-act the adverse yaw produced by the roll-control surfaces. If rudder is continuously applied in level flight the aircraft will yaw initially in the direction of the applied rudder – the primary effect of rudder. After a few seconds the aircraft will tend to bank in the direction of yaw.
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.
The pilot then holds this attitude while applying aileron input, by carefully moving the stick to either the right or the left. As the aircraft begins to roll, the pilot will need to apply the rudder in the direction of the bank, to counter adverse yaw (the tendency of the nose to yaw away from the bank).
Propeller walk (also known as propeller effect, wheeling effect, paddle wheel effect, asymmetric thrust, asymmetric blade effect, transverse thrust, prop walk) is the term for a propeller's tendency to rotate about a vertical axis (also known as yaw motion). The rotation is in addition to the forward or backward acceleration.
With a symmetrical rocket or missile, the directional stability in yaw is the same as the pitch stability; it resembles the short period pitch oscillation, with yaw plane equivalents to the pitch plane stability derivatives. For this reason, pitch and yaw directional stability are collectively known as the "weathercock" stability of the missile.
The yaw motion is induced through the use of ailerons alone due to aileron drag, wherein the lifting wing (aileron down) is doing more work than the descending wing (aileron up) and therefore creates more drag, forcing the lifting wing back, yawing the aircraft toward it. This yawing effect produced by rolling motion is known as adverse yaw.