Blade for aircraft rotary wings, with swept-back tip

Blade with a swept-back tip for aircraft rotary wings, intended to form part of a rotor whose hub (2) is linked to said blade (1), which is capable of being driven in rotation around the axis of said hub, said blade (1) including a leading edge (5) and a trailing edge (6) and being formed by successive elementary transverse sections (7), identified by the distance r separating each of them from the axis of rotation of said hub, and each exhibiting a defined chord profile and an aerodynamic center whose offset with respect to the pitch variation axis, orthogonal to each of said sections, determines the sweepback of said wing, wherein said blade (1) being subdivided, along its longitudinal extent, into four areas, namely a first area extending from the inner edge of the blade R0 to a first section R1 situated between 75% and 875 of the total length of the blade, measured from the axis of rotation of the hub, a second area extending from the first section R1 to a second section R2 situated between 87% and 93% of the total length of the blade, a third area extending from the second section R2 to a third section R3 situated between 93% and 97% of the total length of the blade and a fourth area extending from the third section R3 to the free outer edge R of the blade, the length of the chord L increases generally linearly in said first area, changes according to a cubic function in said second area, is constant in said third area, and changes according to a parabolic function in said fourth area so that the blade (1) exhibits a double progressive taper toward the inner and outer edges of the blade, the variation in the length of the chord being such that the leading edge (5) and the trailing edge (6) of the blade, along its longitudinal extent, exhibit no break, the leading edge including only convex and straight-line segments and the trailing edge only concave and straight-line segments, and the offset Y'f of the aerodynamic center with respect to the pitch variation axis varies linearly in said first area so that the aerodynamic center is offset toward the leading edge (5) in this area, changes according to a cubic function in said second area, varies linearly in said third area, and changes according to a parabolic function in said fourth area so that the blade (1) exhibits a rearward sweepback, the variation in the offset of the aerodynamic center being such that the leading edge (5) and the trailing edge (6) of the blade, along its longitudinal extent, exhibit no break.