Mounted on the trailing edge of the vertical stabilizer, the rudder is a primary flight control surface that governs rotation about the aircraft's vertical axis, steering the nose side-to-side. By generating and managing yawing motion, it keeps the airplane coordinated, counters adverse yaw from aileron deflection or engine failure on multi-engine types, and holds the fuselage aligned with the runway during turbulent or asymmetric-thrust conditions.
Expert behind this article
Jim Goodrich
Jim Goodrich is a pilot, aviation expert and founder of Tsunami Air.
What does a rudder do on an airplane?
The rudder is used to keep the aircraft coordinated by countering adverse yaw created by aileron deflection, to overcome the tendency of the nose to yaw away from the intended direction of a roll, and to maintain straight flight when asymmetrical thrust or crosswinds disturb the tail. The rudder is a fundamental flight control surface attached by hinges to the trailing edge of the vertical stabilizer. By moving the right or left rudder pedal the pilot deflects this small movable section to the right or to the left, so the effective shape of the airfoil on the vertical tail is altered, angle of attack changes, and the amount of force generated by the tail surface varies. Because of this side force the aircraft yaws - rotates around its vertical axis - so the nose moves left or right, creating the yaw motion and side-to-side motion of the nose. The rudder is not used to turn the aircraft but only to manage the yawing motion.
The rudder's function is aligning the aircraft's orientation, guaranteeing a seamless, directed movement while avoiding a skidding or sliding motion. It is the restorative instrument that countervails unfavorable turn and sustains equilibrium and precise flight. The control surface produces a unified change of direction, assuring the nose remains toward the intended path.
Why do airplanes have a rudder?
Airplanes have a rudder because the vertical stabilizer helps the plane remain directionally stable. The rudder is mounted to that fin so the pilot can command rotation about the vertical axis, a motion called yaw. Without this surface the aircraft deflects, since yaw is vital for maintaining directional stability after disruptive gusts, propeller swirl, or differential thrust.
The rudder's duty is corrective: ailerons create an adverse yaw that tries to pull the nose opposite the intended turn, and rudder deflection counters that force so the flight stays coordinated. In multi-engine aeroplanes the same pedals balance any differential thrust, preventing the unwanted swing that appears when one engine produces more power than the other.
Pilots use the rudder deliberately to slip, the only occasion where you want the nose to point opposite the direction the airplane wants to travel. During a cross-wind landing the pilot holds the opposite rudder while lowering the upwind wing. The resulting slip aligns the fuselage with the runway centre-line while the flight path remains straight, letting the tyres touch without side-load.
The pedals in the cockpit pivot the rudder left or right, creating side force at the tail that yaws the nose. When the pilot centres the pedals, the restoring moment generated by the fixed vertical stabilizer damps the motion and returns the airplane to a stable heading. Fighter planes repeat the same geometry twice because they mount two vertical stabilizers and rudders, giving enough control power for the violent yaw rates demanded by multiple very strong engines and high-angle manoeuvres.
In normal cruise the rudder is the control most likely not used, yet it is always active, whether through the pilot's feet, an automatic yaw damper, or the self-correcting influence of the fin. It keeps the aircraft pointing where the pilot intends, preventing slips or skids, trimming drag, and preserving passenger comfort.
I deem a rudder as an important control surface for counteracting yaw. When the jet needs to swerve in the opposite direction, the rudder allows change of direction.
Jim GoodrichPilot, Airplane Broker and Founder of Tsunami Air
