How does an airplane fly-An airplane flies because its wings create lift
An airplane flies because its wings create lift, the upward force on the plane, as they interact with the flow of air around them.
The wings alter the direction of the flow of air as it passes. The exact shape of the surface of a wing is critical to its ability to generate lift. The speed of the airflow and the angle at which the wing meets the oncoming airstream also contribute to the amount of lift generated. (How does an airplane fly-An airplane flies because its wings create lift)
An airplane’s wings push down on the air flowing past them, and in reaction, the air pushes up on the wings. When an airplane is level or rising, the front edges of its wings ride higher than the rear edges. The angle the wings make with the horizontal is called the angle of attack. As the wings move through the air, this angle causes them to push air flowing under them downward. Air flowing over the top of the wing is also deflected downward as it follows the specially designed shape of the wing. A steeper angle of attack will cause the wings to push more air downward. The third law of motion formulated by English physicist Isaac Newton states that every action produces an equal and opposite reaction (see Mechanics: The Third Law). In this case, the wings pushing air downward is the action, and the air pushing the wings upward is the reaction. This causes lift, the upward force on the plane.
Lift is also often explained using Bernoulli’s principle, which states that, under certain circumstances, a faster moving fluid (such as air) will have a lower pressure than a slower moving fluid. The air on the top of an airplane wing moves faster and is at a lower pressure than the air underneath the wing, and the lift generated by the wing can be modeled using equations derived from Bernoulli’s principle. (How does an airplane fly-An airplane flies because its wings create lift)
Lift is one of the four primary forces acting upon an airplane. The others are weight, thrust, and drag. Weight is the force that offsets lift, because it acts in the opposite direction. The weight of the airplane must be overcome by the lift produced by the wings. If an airplane weighs 4.5 metric tons, then the lift produced by its wings must be greater than 4.5 metric tons in order for the airplane to leave the ground. Designing a wing that is powerful enough to lift an airplane off the ground, and yet efficient enough to fly at high speeds over extremely long distances, is one of the marvels of modern aircraft technology.
Thrust is the force that propels an airplane forward through the air. Thrust is provided by the airplane’s propulsion system; either a propeller or jet engine or combination of the two. (How does an airplane fly-An airplane flies because its wings create lift)
A fourth force acting on all airplanes is drag. Drag is created because any object moving through a fluid, such as an airplane through air, produces friction as it interacts with that fluid and because it must move the fluid out of its way to do its work. A high-lift wing surface, for example, may create a great deal of lift for an airplane, but because of its large size, it is also creating a significant amount of drag. That is why high-speed fighters and missiles have such thin wings-they need to minimize drag created by lift. Conversely, a crop duster, which flies at relatively slow speeds, may have a big, thick wing because high lift is more important than the amount of drag associated with it. Drag is also minimized by designing sleek, aerodynamic airplanes, with shapes that slip easily through the air. (How does an airplane fly-An airplane flies because its wings create lift)
Managing the balance between these four forces is the challenge of flight. When thrust is greater than drag, an airplane will accelerate. When lift is greater than weight, it will climb. Using various control surfaces and propulsion systems, a pilot can manipulate the balance of the four forces to change the direction or speed. A pilot can reduce thrust in order to slow down or descend. The pilot can lower the landing gear into the airstream and deploy the landing flaps on the wings to increase drag, which has the same effect as reducing thrust. The pilot can add thrust either to speed up or climb. Or, by retracting the landing gear and flaps, and thereby reducing drag, the pilot can accelerate or climb. (How does an airplane fly-An airplane flies because its wings create lift)