Primary Flight Controls

Before knowing the primary flight controls one should know how an aircraft takes flight. What part does the wings play and what other surfaces do.

When it comes to the flying of an aircraft there is a difference between the engine and the wings. Most people think engine does most of the things and helps the aircraft to fly. The engine is one part of the aircraft. An aircraft’s engine is designed to make it move forward at high speed. While the wings of an aircraft moves it upward. The wings create an upward force called lift that overcomes the plane’s weight and hold it in the sky while the engine produces the force thrust and reducing the drag. Now the question arises, how do the wings provide the lift? Airplane’s wings have a curved upper surface and flat lower surface, making an airfoil (aerofoil) shape. When an aircraft moves forward the air that strike splits up. When air rushes over the curved surface of the wing it has to travel further at slightly higher speed than the air that passes underneath the surface. According to Bernoulli’s Law, pressure is inversely proportional to the speed, so the fast moving air is at low pressure than the slow moving air. In other words, the pressure at curved surface of the wing is low and the pressure is high underneath. This difference of pressure basically creates the lift for the aircraft. But according to Newton’s 3rd law of motion, if air gives an upward force, the plane must provide an equal and opposite force. The wings are technically designed to push the air downward so as to create an opposite force. The wings aren’t flat underneath but tilted so as to direct the air downward. Vertical and horizontal stabilizers are used to make the aircraft stable when it is lifted from the ground. 

An aircraft in flight is free to rotate in three dimensions: pitch, nose up or down about an axis running from wing to wing; yaw, nose left or right about an axis running up and down; and roll, rotation about an axis running from nose to tail. The axes are alternatively designated as lateral, vertical, and longitudinal.

STABILIZERS:

Vertical and horizontal stabilizers are installed to make the aircraft stable.

 
Vertical Stabilizer:
Vertical stabilizer keeps the airplane lined up with its direction of motion. Air presses
against both its surfaces with equal force when the airplane is moving straight ahead. But if the airplane pivots to the right or left, air pressure increases on one side of the stabilizer and decreases on the other. This imbalance in pressure pushes the tail back into line.

 

Horizontal Stabilizer:
The horizontal stabilizer helps keep the airplane aligned with its direction of motion. If the airplane tilts up or down, air pressure increases on one side of the stabilizer and decreases on the other, pushing it back to its original position. The stabilizer also holds the tail down, countering the tendency of the nose to tilt downward—a result of the airplane’s center of gravity being forward of the wing’s center of lift.

 

AILERON, ELEVATORS and RUDDER:
They are the primary controls of the aircraft.

Ailerons:
The movement of aileron is not symmetrical but opposite. When the pilot moves the aircraft left, aileron on the right wing is lowered and the opposite on the other aileron on the left wing. The pressure is increased on the lower side and the pressure is decreased on the other side making the aircraft tilt on the left side.

Elevators:
Unlike ailerons whose movement is not symmetrical, elevators movement is symmetrical. When the pilot pitches up the plane the elevators are moved up increasing the pressure at the tail. The tail is lowered and the nose of the plane is moved up thus pitching up the plane. 

Rudder:

The rudder is a fundamental control surface which is typically controlled by pedals rather than at the stick. It is the primary means of controlling yaw—the rotation of an airplane about its vertical axis. The rudder may also be called upon to counter-act the adverse yaw produced by the roll-control surfaces.