Lesson 1.1 Flight Controls
1. The three primary flight controls of an airplane are the ailerons, the elevator (or stabilator), and the rudder.
2. Movement of any of these primary flight control surfaces changes the airflow and pressure distribution over and around the airfoil.
a. These changes affect the lift and drag produced and allow a pilot to control the aircraft about its three axes of rotation.
3. Ailerons are control surfaces attached to each wing that move in the opposite direction from one another to control roll about the longitudinal axis.
a. 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 the lift on the left wing. Thus, the increased lift on the left wing and and the decreased lift on the right wing cause the airplane to roll to the right.
4. The elevator is the primary control device for changing the pitch attitude of an airplane, changing the pitch about the lateral axis. It is usually located on the fixed horizontal stabilizer on the tail of the airplane.
i. EXAMPLE: Pulling back on the yoke or stick deflects the trailing edge of the elevator up. This position creates a downward aerodynamic force, causing the tail of the aircraft to move down and the nose to pitch up.
ii. A stabilator is a one-piece horizontal stabilizer and elevator that pivots from a central hinge point.
5. A canard is similar to the horizontal stabilizer but is located in front of the main wings. An elevator is attached to the trailing edge of the canard to control pitch.
a. The canard, however, actually creates lift and holds the nose up rather than the aft-tail design that prevents the nose from rotating downward.
6. The rudder controls movement of the aircraft about its vertical axis.
a. When deflecting the rudder into the airflow, a horizontal force is exerted in the opposite direction; this motion is called yaw.
b. Flight control effectiveness increases with speed because there is more airflow over the surface of the control device.
7. Secondary flight controls may consist of wing flaps, leading edge devices, spoilers, and trim systems.
8. Flaps are attached to the trailing edge of the wing and are used during approach and landing to increase wing lift. This allows an increase in the angle of descent without increasing airspeed.
i. The most common flap used on general aviation aircraft today is the slotted flap.
a. When the slotted flap is lowered, high-pressure air from the lower surface of the wing is ducted to the upper surface of the flap, delaying airflow separation.
b. Spoilers are high-drag devices deployed from the wings to reduce lift and increase drag. They are found on gliders and some high-speed aircraft.
9. Trim systems are used to relieve the pilot of the need to maintain constant pressure on the flight controls. They include trim tabs, antiservo tabs, and ground adjustable tabs.
10. Trim tabs are attached to the trailing edge of the elevator.
a. EXAMPLE: If the trim tab is set to the full nose-up position, the tab moves full down. This causes the tail of the airplane to pitch down and the nose to pitch up.