What is the primary function of the horizontal stabilizer?

The primary function of the horizontal stabilizer is to control pitch, which is the up-and-down movement of the aircraft's nose. The horizontal stabilizer, located at the tail of the aircraft, provides stability around the lateral axis. By modifying the airflow over the stabilizer, the aircraft can maintain its attitude, preventing it from pitching excessively up or down.

When the elevators, which are control surfaces attached to the horizontal stabilizer, are moved by the pilot, they change the angle of the stabilizer relative to the airflow and influence the lift force acting on it. This dynamic allows the pilot to efficiently manage the aircraft's pitch during different phases of flight, especially during takeoff, landing, and maneuvers.

The other functions listed pertain to different components of the aircraft: roll is managed by ailerons, yaw is controlled by the vertical stabilizer and rudder, and thrust is generated by the engines. Therefore, controlling pitch is the primary function of the horizontal stabilizer, making it essential for maintaining stable flight.