Читать книгу Flight Theory and Aerodynamics - Joseph R. Badick - Страница 91

There are four main variables in the geometry of an airfoil:

1 Shape of the mean camber line

2 Thickness

3 Location of maximum thickness

4 Leading edge radius

In a cambered airfoil (nonsymmetrical), the mean camber line and chord line are different. If the mean camber line coincides with the chord line, the airfoil is said to be symmetrical. Figure 3.15 shows the difference between a cambered and symmetrical airfoil, note the position of the chord line. In symmetrical airfoils, the upper and lower surfaces have the same shape and are equidistant from the chord line. Symmetrical airfoils are common in rotary‐wing blades and in some aerobatic aircraft. Figure 3.16 shows examples of early airfoil design to more modern, supersonic designs.

Figure 3.15 Cambered versus symmetrical airfoil.

Source: U.S. Department of Transportation Federal Aviation Administration (2019).

Figure 3.16 Examples of airfoil design.

Source: U.S. Department of Transportation Federal Aviation Administration (2008a).