The rudder in an aeroplane is one of the main components of flight stability systems. Mounted vertically on a plane’s tail section, the rudder helps to keep the plane straight. The rudder helps the pilot to turn the aeroplane by creating a lifting force in a specific direction.

Read on to know the meaning of rudder and its importance for aeroplane manoeuvring. 

The original meaning of rudder refers to its usage in single-engine aircraft to control the drag and subsequent changes in its direction. Modern pilots use a centred ball to determine the stability of the aircraft. In modern aircraft, the rudder is most often used to align the aircraft during take-off and landing.

Rudders ensure flight stability by providing yaw to the plane or the ability to twist along an axis. For example, propeller-driven planes use rudders to counteract the plane’s tendency to turn left or right. Such tendencies arise when the engine puts more power into turning the propellers, thereby moving against the wind.   

Rudders in airlines can counter asymmetric drag posed by a hinged surface in the aircraft wing. These hinged surfaces can control the aircraft’s rolling along the vertical axis. Rudders thus act as potential stabilisers keeping the aircraft’s nose in the forward direction.

The primary function of a rudder in an aircraft is to counteract the effects of crosswinds. Pilots use a second direction-changing device called ailerons to counter asymmetric drags. With ailerons, pilots can control an aircraft's yaw and roll. On the other hand, a rudder is used to correct the adverse yaw effect created during the roll. 

Rudders help aeroplanes control their twist along the vertical and horizontal axis when it is changing directions. However, using rudders at extremely low speeds can cause unexpected spins and result in losing control.

The definition of rudders explains them as essential axis shifters that can counter the effects of the drag caused by the high angle of attacks. Although not directly involved in the flight’s normal course, rudders can help the aircraft maintain minimum control speeds by negating the yawing effect. Pilots can rotate rudders in either direction to control yaws. 

Originally used in boats and ships, rudders also control the dissymmetry of lift in helicopters. Pilots can change the angles of attack on either blade to balance the movement of the rotor disc. Rudders in helicopters and aircraft help maintain the forward direction. Any attempts to turn them mid-air will create enough drag to cause banking, which rudders can control. 

Big aeroplanes use hydraulics to control their vertical movements in rudders. Once the engine powers up the system, rudders return to a neutral position waiting to be managed by the pilot. 

Typically, planes suffer from a particular drag called the P-factor, an asymmetric blade and disc effect that changes the angle of attack every time the propeller wheels turn upwards. As a result, the plane tends to lean on one side with a change in its centre of thrust, causing a misbalance known as the yawing effect.

Multi-engine aircraft can cancel out their P-factors using propellers rotating in opposite directions. However, any disturbance in one engine will increase the thawing effects. The situation worsens when pilots use maximum engine power and the plane ascends faster. Rudder in aircraft can counterbalance such effects even when both engines fail, thereby maintaining balance.