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Things That Affect the Lift of an Airplane Wing

Lift is the cumulative amount of force produced by a wing to overcome the weight of the airplane and make it fly. Birds had if figured out long before humans, but mankind has always wondered about the factors that influence this invisible, seemingly magical power. One hundred years after the Wright Brothers, however, what is now known about lift is probably still not the whole truth. Even in the early 21st century, scientists disagree, and there are several alternative theories about the active principles and forces involved in aerodynamics. The basic factors that affect the lift of a wing, however, are well established.

Gravity and Mass
- For every winged aircraft except a space shuttle floating outside the atmosphere, gravity is always a factor opposing lift. The lift force of a wing is in a constant tug of war with the force of gravity. Gravity figures into the lift calculation according to the mass of the aircraft. The greater the plane's weight, the more lift required to overcome the gravitational grip. A two-seat trainer made of lightweight composite materials does not have the lift-generation requirements of an all-metallic passenger jet.
Airfoil
- The aerodynamic shape of the wing, called the "airfoil," affects how much lift the wing produces and how efficiently it does so depending on its size and weight. An airfoil's contour changes the way air flows over the wing as the aircraft moves forward.
  
  Air passing over the curved upper portion of the wing moves faster than the air passing its straight underside. Known as the "Bernoulli Effect," this creates a zone of lower air pressure above the wing, which generates the upward force of lift. The design and shape of the airfoil also enlists the aid of Newton's Third Law of Motion, which states that every action has an equal and opposing reaction: As oncoming air follows the curved shape of the airfoil and flows sharply down behind it, an equal opposing force is produced that pushes the airfoil up.
Velocity and Angle of Attack
- A static wing has no lift. The wing has to be propelled forward through the air by the power of the airplane, either through its propeller or jet engine. Lift increases with velocity. An aircraft's stall speed occurs when velocity slows to the point that the angle of attack of the wings must be increased to prevent loss of altitude as the lift forces diminish. Increasing the angle of attack of the wing causes the smooth airflow over the top of the wing to separate from the wing and leads to a dramatic loss of lift. When a wing stalls, the airplane falls --- unless the pilot takes quick corrective action to recover.
Air Density
- Denser air produces greater lift and thinner air decreases lift. Air gets thinner as temperature increases and when barometric pressure drops. Therefore, a wing produces less lift on hot, clear days than on a colder, cloudy day. The density of the air also thins as altitude increases. This is one reason every aircraft has a maximum altitude above which it cannot fly. At a certain height, the density of the air no longer provides sufficient lift.

Aviation