US Patent 8079823 Fan blades

A fan blade comprises an airfoil having an upper surface with region that has a generally elliptical curvature. In some examples, the lower surface has a convex region and a concave region. The curvature of the concave region corresponds with the generally elliptical curvature of the upper surface; while the curvature of the convex region is defined by a substantially constant radius. Some examples also include a trailing edge flap region, which may itself include a first flap portion and a second flap portion. When mounted to a rotating hub member fan, blades with elliptical curvatures may provide air movement at significant efficiencies.