What is the movable primary control surface mounted on the trailing edge of the vertical fin of an airplane that rotates the airplane about its vertical axis?

• A. Rudder
• B. Elevator
• C. Aileron
• D. Ruddervator

Answer: (A)

Yaw control is achieved with a movable surface on the trailing edge of the vertical stabilizer. This surface, the rudder, is moved left or right to push the tail and rotate the airplane around its vertical axis. Deflecting the rudder creates a yawing moment that changes the aircraft’s heading, which is essential for coordinating turns and keeping the nose pointed in the desired direction.

Elevators, located on the horizontal stabilizer, control pitch about the lateral axis by raising or lowering the nose. Ailerons, on the wings, control roll about the longitudinal axis. A ruddervator is a combined surface found on some tail designs (like V-tails) that blends rudder and elevator functions. The surface described in the question is the rudder.