The Airfoil & Theories of Lift
Have you noticed the curved shape of a bird's wing? An airplane's wing is curved also. A wing is designed for flight. It has a special shape called an airfoil. The airfoil shape provides a lifting force when air flows around it. Airfoil shapes can be found on wings, fans and propellers.
An airplane’s airfoil plays a very important role in lifting the aircraft. The airfoil is designed to increase the velocity of the airflow above its surface, thereby decreasing pressure above the airfoil. Simultaneously, the impact of the air on the lower surface of the airfoil increases the pressure below. This combination of pressure decrease above and increase below produces lift.
Airfoil Behavior and Influence on an Aircraft:
As a wing moves through air, the air is split and passes above and below the wing. The wing’s upper surface is shaped so the air rushing over the top speeds up and stretches out. This decreases the air pressure above the wing. The air flowing below the wing moves in a straighter line, so its speed and air pressure remains the same. Since high air pressure always moves toward low air pressure, the air below the wing pushes upward toward the air above the wing. The wing is in the middle, and the whole wing is “lifted.” The faster an airplane moves, the more lift there is. And when the force of lift is greater than the force of gravity, the airplane is able to fly.
The Four Forces of Flight
If you push a door closed, your push is a force. If you pull a drawer open, your pull is a force. A force actually has two parts. One part is the strength of the force. The other part is the direction of the force. Let's say you are pulling on a rope. Pull it to the right, then to the left. Pull it upwards and then pull it downwards. Where you pulled the rope is the direction of the force. A force has both magnitude and direction. In aeronautics, there are four important...
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