This systematic study of variations in the amount and position of maximum camber and thickness resulted in the wind-tunnel tests of hundreds of airfoil shapes. In the 1920′s, the National Advisory Committee for Aeronautics (NACA) began an exhaustive study of airfoil aerodynamics, examining in detail the effects of variations in camber and thickness distributions on the behavior of wings. They also proved able to provide good aerodynamic behavior over a wider range of angle of attack as well as better stall characteristics, but excessive thickness made for increased drag. The thicker airfoils allowed a stronger wing structure as well as a place to store fuel. Later aircraft used thicker airfoils with both upper and lower surfaces covered first with fabric and then with metal. Later researchers learned to create temporary increases in camber by using flaps.

They found that the location of maximum camber affected both the amount of lift generated at given angles of attack and the airfoil’s stall behavior and that too much camber can give high drag. In other words, an airfoil has 6 percent camber if the maximum distance between its chord and camber lines is 0.06 times its chord length.Įxperimenters in the late 1800′s tried wings built with airfoils with different amounts of camber and different positions of maximum. The amount of camber possessed by an airfoil is defined by the maximum distance between the chord and camber lines expressed as a percentage of the chord. A symmetrical airfoil is said to have zero camber. If the airfoil is symmetrical, in other words, if its upper surface is exactly the inverse of its lower surface, then the camber line is coincident with its chord line, a straight line from the leading edge to the trailing edge of the airfoil. The camber line, or mean line, of an airfoil is a curved line running halfway between its upper and lower surfaces. Usually the frame for such an airfoil was curved, or cambered.

Pitch must be evaluated along with the forces of lift and drag.Įarly airfoil shapes were thin, essentially cloth stretched over a wood frame, a type of airfoil sometimes seen today in the wings of ultralight or hang glider-type aircraft.

The amount of pitching movement, or tendency for the airfoil to rotate nose up or down, is also a function of the airfoil’s shape and the way lift is produced. An airplane designer tries to select an airfoil shape that will give the best possible lift-to-drag ratio at some desired optimum flight condition, such as cruise or climb, depending on the type of aircraft. The shape of the airfoil then determines the balance of lift and drag at various angles of attack. The shape of the upper and lower surfaces of the airfoil and the angle that it makes with the oncoming airflow, or angle of attack, determines the way the flow will accelerate and decelerate around the airfoil and, thus, determines its ability to provide lift.įlow around the airfoil also causes drag, and an airfoil should be designed to get as much lift as possible while at the same time minimizing drag. The higher-speed air on the top of the airfoil produces a lower pressure than the flow over the bottom, resulting in lift. Although airfoils come in many different shapes, all are designed to accomplish the same goal: forcing the air to move faster over the top of the wing than it does over the bottom. The shape revealed if a wing were to be sliced from its leading edge to its trailing edge is called the wing’s airfoil section. Significance: The shape of a wing’s airfoil section or sections determines the amount of lift, drag, and pitching movement the wing will produce over a range of angles of attack and also determines the wing’s stall behavior. Definition: A two-dimensional, front-to-back section or slice of a wing.

Camber airfoil