Low-noise blade for an open rotor

A blade for an open rotor, comprising:

• a pressure side and a suction side, the pressure side and the suction side intersecting at a leading edge and a trailing edge, wherein at each spanwise location, a chord of an airfoil section is defined as a straight line distance between the leading edge and the trailing edge and a meanline is defined midway between the pressure side and the suction side;
• wherein for at least 30% of a span of the blade, the meanline of the airfoil section is shaped such that a relative curvature parameter is greater than 1.75 in a first region, less than 0.75 in a second region, and greater than 1.2 in a third region, wherein the relative curvature parameter of a region is defined by Δζn/Δζtot/Δ(x/c)n wherein ζ corresponds to the inverse tangent of the slope of a meanline curve, Δζtot corresponds to a total change in meanline angle, subscript n indicates the region, and x/c is a chordwise location normalized by the chord;
• and
• wherein for between 30% and 90% spanwise location of the span of the blade, the airfoil section has a maximum thickness of about 2% to about 7% of the chord.