Patent ID: 6142738
Filing Date: 2000-11-07
Classification: B64C

Abstract:
A blade for a rotary wing aircraft, said blade comprising a main part of the blade having a chord C.sub.0 and a blade tip winglet having a chord C.sub.1, said blade tip winglet intended to reduce blade-vortex interaction noise during descending flight,wherein said winglet has, in plan view, an at least approximately trapezoidal shape, and wherein a mean value of said chord C.sub.1 of the winglet is between 25% and 40% of said chord C.sub.0 of the main part of the blade,wherein an expression defining a chord of said winglet based on a first coordinate (R-x)/C.sub.0, in which R represents a total span of said winglet, and x represents a variable length along said span R, and a second coordinate C.sub.1 /C.sub.0,has a lower limit at a point A at which (R-x)/C.sub.0 is equal to 1.00 and C.sub.1 /C.sub.0 is equal to 1.00; at a point B at which (R-x)/C.sub.0 is equal to 1.00 and C.sub.1 /C.sub.0 is equal to 0.35; and at a point C at which (R-x)/C.sub.0 is equal to 0.00 and C.sub.1 /C.sub.0 is equal to 0.15; andhas an upper limit at a point D at which (R-x)/C.sub.0 is equal to 0.60 and C.sub.1 /C.sub.0 is equal to 1.00; at a point E at which (R-x)/C.sub.0 is equal to 0.60 and C.sub.1 /C.sub.0 is equal to 0.40; and at a point F at which (R-x)/C.sub.0 is equal to 0.00 and C.sub.1 /C.sub.0 is equal to 0.40.