How does an aircraft fly?

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How does an aircraft fly

People have always wondered what keeps an aircraft in the air.

The most amazing feeling while flying is to lookout of your window as the aircraft takes off or when it touches down while landing. However, most of us aren't aware how this man-made machine is able to defy gravity.

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Four primary forces that keep an aircraft in the sky

Thrust is a force that moves an aircraft in the direction of the motion. Air is pulled in and then pushed out in an opposite direction.

Drag is the force that acts opposite to the direction of the motion.

Weight is the force caused by gravity.

Lift is the force that holds an airplane in the air.

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Wings

Wings are the most important lift producing component of an aircraft. They vary in design depending upon the aircraft type and its purpose. Most airplanes are designed in a way that
the outer tips of the wings are higher than where the wings are attached to the fuselage.

The upward angle is called the dihedral and helps keep the airplane from rolling unexpectedly during the flight. Modern aircraft use winglets on the tip of the wings to reduce drag. When air flows past it, due to the difference in curvature of its upper and lower parts, lift is generated, which is responsible or balancing the weight of the plane allowing the body to fly.

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Bernoulli's Principle

During the 1700s, Daniel Bernoulli, a famous scientist, showed that a fluid that flows faster over a surface will create less pressure on the surfacethan the fluid that flows slowly. This concept later came to be known as 'Bernoulli's Principle'.

Air is a physical substance and has weight, it has molecules that are moving constantly and as a result creates pressure. Fast moving air has less pressure while slow moving air has more. The wings of an aircraft have been designed in a way to make the air move faster, over the top edge of the wing. Consequently, the air pressure decreases on the top edge compared to the bottom edge. The difference in pressure creates a force on the wing that lifts it up into the air which, in turn, lifts the aircraft.

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Flight Control

In order to turn an aircraft in an efficient and fully-coordinated manner, a pilot has special controls that can be used to fly the plane. There are levers and buttons to change the yaw, pitch and roll of the plane.

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Roll, Pitch, Yaw

Roll: Aircraft wings have ailerons (rectangular flaps at the back of the wings). To roll the plane to the right or left, the ailerons are raised on one wing and lowered on the other. The pilot controls the roll of the plane by raising one aileron or the other with a control wheel. Turning the control wheel clockwise raises the right aileron and lowers the left aileron, which rolls the aircraft to the right and vice-versa for turning left.

Pitch: In order to climb higher or descend lower, the pilot adjusts the elevators on the tail. Lowering the elevators causes an airplane's nose to drop, sending the plane into a downward path. Similarly, raising the elevators causes an airplane to climb higher into the sky. This process is called Pitch.

Yaw: It is the turning of a plane. Rudder works to control the yaw of the plane. When the rudder is turned to one side, the airplane moves accordingly. The airplane's nose is pointed in the same direction as the direction of the rudder. The rudder and the ailerons are used together to make a turn.