What is the primary purpose of the rudder on an aircraft?

The primary purpose of the rudder on an aircraft is to control yaw, which refers to the rotation of the aircraft around its vertical axis. The rudder is located on the vertical stabilizer at the tail of the aircraft and works by altering the airflow around the tail when it is moved to the left or right. This action allows the pilot to make coordinated turns, maintain a straight flight path, and counteract any yawing motion that may arise from factors such as engine thrust or external wind.

Controlling yaw is essential for maintaining the aircraft's stability and ensuring safe, smooth maneuvers. While other flight control surfaces and systems are responsible for changing altitude (such as the elevator, which controls pitch) or increasing speed (via engine thrust or changes in drag), the rudder's specific function is linked solely to managing yaw. Thus, it is crucial for effective aircraft handling and navigation.