

The Science of Flying

How does an airplane fly? The answer lies in the laws of aerodynamics. It is the dynamics of four forces working in unison: thrust, drag, weight and lift. A balance of these forces is necessary for keeping an aircraft afloat. Thrust helps aircraft to move forward, while drag pulls it back. The lift is countered by weight exerted by the gravitational force. Ideally, an aircraft will maintain its flight path if thrust is equal to drag and weight is equal to lift. Any variation will have an adverse impact. If drag were more than the thrust, the obvious result would be slowing down of the aircraft. Similarly, if weight is more than the lift, the aircraft will come down.

In order to get airborne, the aircraft must overcome drag. Here comes the role of engines, which provide the necessary thrust to negotiate any resistance. The main enemy, so to say, of thrust is drag. Simply put, if an object moves in a fluid (in aerodynamics air is a fluid), it faces resistance. This resistance is due to the force called drag. This force is experienced by all of us in our daily lives. Stick you hand out of the window of a car and you would notice it being pushed back. How much is the force depends on a number of factors: one being the size of the hand, the bigger the hand more the resistance. This explains the forward movement of aircraft. But how does it get airborne? It happens when lift is generated. The concept of lift is easier said than explained.

In simple terms, lift is the upward force created by wings moving through the air. The force is created by the air flowing over the wings resulting in pressure differences due to variations in the speed.

There are many theories that throw light on the phenomenon of lift. The two most popular are: Longer Path or Bernoulli's explanation and Newtonian explanation. However, both have been found flawed. According to Bernoulli's explanation, when speed of fluid flow increases it results in decrease in pressure. It says that air moving about the wind moves faster than the air below it. It means that faster air will develop lower pressure on the top of the wing while slower air would result in higher pressure at the bottom. This pressure difference would result in lift.

The Newtonian explanation revolved around the third law of motion that for every action there is equal and opposite reaction. Air hitting the bottom of the wing gives it a momentum.

Wings help aircraft fly. Wings are not simple attachments to the aircraft; its shape, size and structure are the results of complicated designs and have a role to play.

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