Airfoil for rotor blade with reduced pitching moment

Abstract

A rotor blade for a rotary wing aircraft includes a root region extending from a rotor head to about 15% to 20% of a blade radius, a main region extending from a radial extent of the root region to about 80% to 95% of the blade radius, a tip region extending from a radial extent of the main region to a blade tip, and a trailing edge. A portion of one of the root region, the main region and the tip region has an airfoil profile section including a trailing edge reflex camber relative to a base airfoil shape of a remainder of the one of the root region, the main region, and the tip region to reduce pitching moment of the rotor blade while maintaining a positive aerodynamic characteristic of the base airfoil shape. The reflex camber extends 20% of a blade chord from the trailing edge.

1 . A rotor blade for a rotary wing aircraft comprising:
 a root region extending from a rotor head to about 15% to 20% of a blade radius;   a main region extending from a radial extent of the root region to about 80% to 95% of the blade radius;   a tip region extending from a radial extent of the main region to a blade tip; and   a trailing edge extending from at least the main region toward the tip region, wherein a portion of one of the root region, the main region and the tip region has an airfoil profile section including a trailing edge reflex camber relative to a base airfoil shape of a remainder of the one of the root region, the main region, and the tip region to reduce pitching moment of the rotor blade while maintaining a positive aerodynamic characteristic of the base airfoil shape, the reflex camber extending 20% of a blade chord from the trailing edge.   
     
     
         2 . The rotor blade according to  claim 1 , wherein the tip section is defined by an outboard 20% of the rotor blade span. 
     
     
         3 . The rotor blade according to  claim 2 , wherein the airfoil profile section is disposed at least partially at an outermost 5% to 7% of the rotor blade span. 
     
     
         4 . The rotor blade according to  claim 1 , wherein the airfoil profile section is at least partially disposed at the root region. 
     
     
         5 . The rotor blade according to  claim 1 , wherein the rotor blade is a main rotor blade of a helicopter. 
     
     
         6 . The rotor blade according to  claim 1 , wherein the reflex camber extends from the trailing edge upward by a distance of about 6% of the blade chord. 
     
     
         7 . The rotor blade according to  claim 1 , wherein at least a portion of one of the root region, the main region and the tip region including an airfoil profile section defined by a scaled set of coordinates in which a set of x/c coordinates defined as a ratio of an x coordinate to a blade chord length, and y/c coordinates defined as a ratio of a y coordinate to the blade chord length, listed in Table I are scaled by a selected factor. 
     
     
         8 . The rotor blade according to  claim 7 , wherein the tip section is defined by an outboard 20% of the rotor blade span. 
     
     
         9 . The rotor blade according to  claim 7 , wherein the airfoil profile section is at least partially disposed at the root region. 
     
     
         10 . The rotor blade according to  claim 7 , wherein the rotor blade is a main rotor blade of a helicopter.