How is "yaw" controlled in an aircraft?

Yaw is controlled primarily through the use of the rudder. The rudder is a vertical control surface located on the tail of the aircraft, and it is specifically designed to control the yaw motion, which is the left or right movement of the aircraft's nose. When the pilot applies pressure on the rudder pedals, the rudder deflects to one side, causing the aircraft to rotate around its vertical axis. This control is crucial for coordinating turns and maintaining directional stability during flight.

The other options pertain to different functions of aircraft control surfaces. Ailerons, for example, are used to control roll, which is the tilting motion of the aircraft’s wings. Changing flap positions affects lift and drag, but does not directly influence yaw. The elevator is responsible for controlling pitch, or the up and down movement of the aircraft's nose. Each control surface plays a distinct role in managing the aircraft's flight dynamics, and understanding their specific functions is essential for effective piloting.