Aerodynamics: Flight Controls

Flight Controls
The three primary flight controls of an airplane are the ailerons, the elevator (or stabilator), and the rudder.

• Movement of any of these primary flight control surfaces changes the airflow and pressure distribution over and around the airfoil.  These changes affect the lift and drag produced and allow a pilot to control the aircraft about its three axes of rotation.

Ailerons are the surface attached to each wing that move up or down in the opposite direction of each other simultaneously. It allows the pilot to control roll about the longitudinal axis,

• Example: Moving the yoke (or stick) to the right causes the right aileron to deflect upward, resulting in decreased lift on the right wing. The left aileron moves in the opposite direction and increases lift on the left wing. This causes the aircraft to roll to the right.

The elevator is responsible for pitch attitude, about the lateral axis. It is at the tail of the airplane, located on the horizontal stabilizer.

• Example: Pulling back on the yoke deflects the trailing edge of the elevator up. This creates a downward aerodynamic force, causing the tail of the aircraft to move down and the nose to pitch up. 

The rudder controls movement about its vertical axis. When deflecting the rudder into the airflow a horizontal force is exerted in the opposite direction. This motion is called yaw. The effectiveness of the rudder increases with speed.

Secondary flight controls include: flaps, spoilers, and trim systems; they affect the angle of attack, pressure on the wings, and lift and drag.

The four aerodynamic forces are lift, weight, thrust, and drag. (lift = weight; thrust = drag)