Patent ID: 8210818

Claim:
A blade for an antitorque tail rotor of a helicopter, comprising: a leading edge and a trailing edge opposite each other and elongated along a longitudinal axis of the blade; said trailing edge, in use, interacting with the air current after said leading edge, an intermediate portion of the blade extending between a further section, radially inner with respect to the reference section and the reference section it self, the chord of the blade assuming a constant value d0 at the intermediate portion, a first and a second surface opposite each other and extending between said leading edge and said trailing edge; said first and second surface, when sectioned in a longitudinal plane of the blade parallel to said trailing edge and crosswise with respect to the rotation axis of the blade, respectively having a first and a second contour joined at said end; said first and second contour respectively comprising a first and second portion extending along said intermediate portion, and a third and fourth portion extending along said end portion; said third and fourth portion being asymmetrical with respect to a centerline of said blade equidistant from said first and second portion, and an end portion extending between a reference section and a radially outer end of said blade with respect to a rotation axis of said blade( 6 ); said rotation axis(A) being outside the blade and crosswise with respect to said longitudinal axis; the length of the chord at said end portion decreasing from said reference section to said end and said leading and trailing edges being joined at said end; wherein the length (d) of said chord equals a length d0 at said reference section, and decreases, from said reference section to said end, according to the equation d=d0(1-krn), where r is the distance from said reference section, and k and n are constant coefficients; n ranging between 2 and 11 and k being equal to ratio 1/R, where R is the radial distance between said end and said reference section.