Abstract: A blade for a rotary wing aircraft includes a blade tip winglet intended to reduce the blade-vortex interaction noise during descending flight. The winglet has, in plan view, an at least approximately trapezoidal shape, and the mean value of a chord C.sub.1 of the winglet is between 25% and 40% of a chord C.sub.0 of the main part of the blade. Compared with a conventional rectangular tip, and for the same aerodynamic thrust, the reduction in noise associated with use of the blade tip winglet can be as much as 40%.

Abstract: The present invention relates to a blade with a swept-back tip for a rotary wings of an aircraft, a blade being formed of successive elemental cross sections. The blade is divided into different regions, with the chord length L and the offset y'f of the center of pressure from the pitch-change axis and the relative thickness of each elemental section are optimized for high-speed flight. The first region has a linearly increasing chord length, the second region has the maximum and constant chord length, the third region has a linearly decreasing chord length and the fourth region has a decreasing chord length according to a parabolic function. The offset of the aerodynamic center is positive and increases in proportional to the distance in the first region, is at its maximum and constant in the second region, and decreases linearly and become negative in the third region.