#Airfoil terminology skin#
#Airfoil terminology full#

An intelligent discussion of the aerodynamic forces affecting rotor blade lift and drag requires a knowledge of blade section geometry. Rotary-wing airfoils operate under diverse conditions, because their speeds are a combination of blade rotation and forward movement of the helicopter. Recent design processes and new materials used to manufacture rotor systems have partially overcome the problems associated with use of nonsymmetrical airfoils. Rotor system components had to be designed that would withstand the twisting force. When center of pressure moves, a twisting force is exerted on the rotor blades. Nonsymmetrical airfoils were not used in earlier helicopters because the center of pressure location moved too much when angle of attack was changed. The advantages of the nonsymmetrical airfoil are increased lift-drag ratios and more desirable stall characteristics. Nonsymmetrical (cambered) airfoils may have a wide variety of upper and lower surface designs. Other benefits are lower cost and ease of construction as comparedto the nonsymmetrical airfoil. The symmetrical airfoil delivers acceptable performance under those alternating conditions. The helicopter blade (airfoil) must adapt to a wide range of airspeeds and angles of attack during each revolution of the rotor. However, the symmetrical airfoil produces less lift than a nonsymmetrical airfoil and also has relatively undesirable stall characteristics.

#Airfoil terminology full#

Travel remains relatively constant under varying angles of attack, affording the best lift-drag ratios for the full range of velocities from rotor blade root to tip. They are suited to rotary-wing applications because they have almost no center of pressure travel. Symmetrical airfoils have identical upper and lower surfaces. Usually the designer must compromise to obtain an airfoil section that has the best flight characteristics for the mission the aircraft will perform.Īirfoil sections are of two basic types, symmetrical and nonsymmetrical. Helicopter blades have airfoil sections designed for a specific set of flight characteristics. Its shape produces lift when it passes through the air. The rotor blade, or airfoil, is the structure that makes flight possible.

Some airfoils combine some of these functions.Ī helicopter flies for the same basic reason that any conventional aircraft flies, because aerodynamic forces necessary to keep it aloft are produced when air passes about the rotor blades. An airfoil may be no more than a flat plate (those darned engineers !) but usually it has a cross section carefully contoured in accordance with its intended application or function.Īirfoils are applied to aircraft, missles, or other aerial vehicles for:įor Control (A Flight Surface, such as a Rudder) Thus, high-lift wings have a large positive camber on the upper surface and a slightly negative camber on the lower surface.An Airfoil is a structure, piece, or body designed to obtain a useful reaction upon itself in its motion through the air. Camber is positive when departure from the chord line is outward and negative when it is inward. Upper camber refers to the upper surface, lower camber to the lower surface, and mean camber to the mean line of the section.

As stated, camber refers to the curvature of an airfoil surface above and below the chord line. The amount of lift produced by an airfoil increases with an increase in wing camber. High-lift wings and high-lift devices for wings have been developed by shaping the airfoils to produce the desired effect.

#Airfoil terminology skin#

The best wing is a compromise between these two extremes to hold both turbulence and skin friction to a minimum A wing with a low fineness ratio produces a large amount of turbulence. A wing with a high fineness ratio produces a large amount of skin friction.

If the wing has a high fineness ratio, it is a very thin wing. Turbulence and skin friction are controlled mainly by the fineness ratio, which is defined as the ratio of the chord of the airfoil to its maximum thickness. The shape of the airfoil determines the amount of turbulence or skin friction that it produces, consequently affecting the efficiency of the wing.