The Rectangular Aerofoil

This is an aerofoil whose planform is a rectangle. An aerofoil whose shape is that of a cylinder erected on an aerofoil profile satisfies this requirement.

8.10.6 Cylindrical Rectangular Aerofoil

This is the simplest type, of span 2b and chord c, which is constant at all sections. All the sections are similar and similarly situated.

8.11 Aerodynamic Characteristics of Asymmetric Loading

The vortex distribution k(y) for symmetrical loading falls symmetrically about the mid-span section of an aerofoil, involving only the odd terms, and producing vortex drag and downwash variation which are also symmetrical about the centerline. In the general case, where the loading or lift distribution is not symmetrical about mid-span section, even terms appear in the distribution, and as a consequence of the asymmetry other characteristics of aerofoil appear.

When the lift distribution is not symmetrical about the centerline, one wing will have higher lift than the other. This will cause a rolling moment about the longitudinal axis passing through the mid-span of the wing.

Further, as the lift is not symmetric nor is the spanwise distribution of circulation, the downwash will vary across the span without being symmetrical about the centerline and so will be the vortex drag grading. Hence, more drag will be experienced on one wing (the one with more lift) than on the other and a net yawing moment will result about the vertical (normal) axis through the mid-span section. In addition to these there will be the overall lift and vortex drag force normal and parallel to the plane of the aerofoil in the plane of symmetry.