Patent ID: 8210818
Filing Date: 2012-07-03
Classification: B64C

Abstract:
1. 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( 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.