Which control surface primarily affects the aircraft's pitch?

The control surface that primarily affects an aircraft's pitch is the elevators. Elevators are located on the horizontal stabilizer at the tail of the aircraft and are responsible for controlling the aircraft's nose up or down movement. When the pilot pulls back on the control yoke or stick, the elevators deflect upward, which decreases the airflow over the tail and raises the nose of the aircraft, causing it to climb. Conversely, pushing forward on the control yoke or stick causes the elevators to deflect downward, increasing airflow over the tail, lowering the nose, and leading to a descent.

In contrast, ailerons are primarily used for controlling roll and lateral movement, and rudder is responsible for managing yaw and directional control. Flaps are used to increase lift and drag, especially during takeoff and landing, but do not directly control pitch. Therefore, the elevators are the critical control surface for pitch adjustments in flight.