The Four Forces of Flight and Aircraft Control Surfaces

This set covers the fundamental forces of flight, the three axes of aircraft movement, and the primary and secondary control surfaces used to navigate an aircraft.

Lift

The force produced by wings (airfoil shape) that acts perpendicular to the relative wind, influenced by Bernoulli's principle and Newton's third law.

Bernoulli's principle

A principle stating that faster airflow over a curved upper surface results in lower pressure, contributing to the generation of lift.

Newton's third law (as applied to lift)

The principle that as a wing deflects air downward and backward, the aircraft is pushed upward and forward in an equal and opposite reaction.

Angle of Attack (AoA)

The angle between the wing and the oncoming air (relative wind).

Weight

The force of gravity acting on the total mass of the aircraft, acting straight down through the center of gravity (CG).

Thrust

The forward-acting force produced by the engine (propeller or jet exhaust) that is directly controlled by the pilot via the throttle.

Parasite drag

Resistance caused by the aircraft moving through the air, including friction, form, and interference drag; it increases with airspeed.

Induced drag

A by-product of lift that is highest at low speeds and high angles of attack (AoA).

Longitudinal axis

The axis running from the nose to the tail, around which the aircraft performs roll movements.

Lateral axis

The axis running from wingtip to wingtip, around which the aircraft performs pitch movements.

Vertical axis

The axis running from top to bottom through the aircraft, around which the aircraft performs yaw movements.

Ailerons

Primary flight controls located on the trailing edge of the wings that move in opposite directions to control roll around the longitudinal axis.

Elevator

A primary flight control on the trailing edge of the horizontal stabilizer used to control pitch around the lateral axis.

Rudder

A primary flight control on the trailing edge of the vertical stabilizer used to control yaw around the vertical axis.

Flaps

Secondary control surfaces on the trailing edge of the wing that increase both lift and drag for takeoff and landing.

Slats

Leading-edge devices that delay airflow separation to allow a higher angle of attack (AoA) without stalling.

Spoilers

Panels on the upper surface of the wing, also called speedbrakes, that disrupt airflow to reduce lift and increase drag.

Trim tabs

Small surfaces attached to primary controls that allow a pilot to relieve control pressure and maintain a desired attitude.

Adverse yaw

An aerodynamic effect during a turn where the wing producing more lift also produces more induced drag, pulling the nose in the opposite direction of the turn.

Elevons

A combination of ailerons and elevators used on delta-wing aircraft.

Ruddervators

A combined control surface used on V-tail aircraft that performs the functions of both the rudder and the elevator.