Airfoil, also spelled Aerofoil, shaped surface, such as an airplane wing, tail, or propeller blade, that produces lift and drag when moved through the air.
The fact that the helicopter obtains its lifting power by means of a rotating airfoil (the rotor) greatly complicates the factors affecting its flight, for not only does the rotor turn but it also moves up and down in a flapping motion and is affected by the horizontal or vertical movement of the helicopter itself.
The chord line of a rotor, like the chord line of a wing, is an imaginary line drawn from the leading edge to the trailing edge of the airfoil.
The Fw 190, the P-47, and the F6F had distinctively bulky fuselages widened to accommodate their twin-row radial engines, while the slimmer P-51, designed in 1940 by J.H. ("Dutch") Kindleberger under a British contract, was fitted with in-line engines and incorporated the latest drag-reduction and airfoil data provided by NACA.
One advantage of atmospheric flight is that traditional methods of flight control (e.g., airfoil wings for aerodynamic lift, rudder and elevator flaps for directional and vertical control) are readily available from the technologies of manned aircraft.
Earlier, the formula ρv0K was quoted for the strength of the Magnus force per unit length of a rotating cylinder, and the same formula can be applied to the inclined plate in Figure 18B or to any airfoil that has shed a starting vortex and around which, consequently, there is circulation.
A special airfoil "wing" located at the rear produces a large downward force (between 4,000 and 8,000 pounds) that helps to maintain traction and stability.
In flight they resemble a tapered air mattress, with openings at the parachute's front that allow the air to "ram" into the cell structure and inflate the parachute into its airfoil shape.
Several years after their historic effort, Frederick W. Lanchester, a British engineer, proposed a circulation theory of lift of an airfoil of infinite span and a vortex theory of the lift of a wing of finite span.
Thus, total lift is related to the shape of the airfoil, the angle of attack, and the speed with which the wing passes through the air.
The rudder is an appendage that has a cross section much like an airfoil and that develops lift when it is turned to produce a nonzero angle of attack relative to the water.
