Rotor blade for helicopter

Abstract

A rotor blade for a helicopter having: a main blade with a blade root attached to a rotor shaft of the helicopter; and a small blade attached to a blade tip part of the main blade, wherein a tip part of the small blade is rectangular form in its plane shape, and has a leading edge continuous with a leading edge of the main blade and a chord length shorter than a chord length of the main blade.

1 . A rotor blade for a helicopter comprising: 
 a main blade with a blade root attached to a rotor shaft of the helicopter; and    a small blade attached to a blade tip part of the main blade,    wherein a tip part of the small blade is rectangular form in its plane shape, and has a leading edge continuous with a leading edge of the main blade and a chord length shorter than a chord length of the main blade.    
   
   
       2 . The rotor blade for a helicopter as claimed in  claim 1 , wherein the chord length c 1  of the small blade is set so as to satisfy a following relational expression;  
       α≦c 1 ≦0.5C (α>0)  
     where C denotes the chord length of the main blade.  
   
   
       3 . The rotor blade for a helicopter as claimed in  claim 1 , wherein the chord length c 1  of the small blade is set so as to satisfy a following relational expression;  
       0.2C≦c 1 ≦0.5C  
     where C denotes the chord length of the main blade.  
   
   
       4 . The rotor blade for a helicopter as claimed in  claim 1 , wherein a blade tip of the small blade protrudes outward by a specific length relative to a tip part of the main blade, and the specific length b 1  is so set as to satisfy a following expression;  
       β≦b 1 ≦0.5C (β>0)  
     where C denotes the chord length of the main blade.  
   
   
       5 . The rotor blade for a helicopter as claimed in  claim 1 , wherein a blade tip of the small blade protrudes outward by a specific length relative to a tip part of the main blade, and the specific length b 1  is set so as to satisfy a following expression;  
       0.2C≦b 1 ≦0.4C  
     where C denotes the chord length of the main blade.  
   
   
       6 . The rotor blade for a helicopter as claimed in  claim 1 , wherein a blade tip vicinity part of the main blade is bent downward by a predetermined anhedral angle.  
   
   
       7 . The rotor blade for a helicopter as claimed in  claim 1 , wherein the small blade has a predetermined anhedral angle relative to the main blade.  
   
   
       8 . The rotor blade for a helicopter as claimed in  claim 1 , wherein the small blade has a predetermined angle of incidence relative to the main blade.  
   
   
       9 . The rotor blade for a helicopter as claimed in  claim 1 , wherein a blade tip vicinity part of the main blade and the small blade continuously joined to the blade tip vicinity part are swept back toward the outside of the blade tip.  
   
   
       10 . The rotor blade for a helicopter as claimed in  claim 2 , wherein a blade tip part of the small blade protrudes outward by a specific length relative to a tip part of the main blade, and the specific length b 1  is set so as to satisfy a following expression;  
       β≦b 1 ≦0.5C (β>0)  
     where C denotes the chord length of the main blade.  
   
   
       11 . The rotor blade for a helicopter as claimed in  claim 3 , wherein a blade tip of the small blade protrudes outward by a specific length relative to a tip part of the main blade, and the specific length b 1  is set so as to satisfy a following expression;  
       β≦b 1 ≦0.5C (β>0)  
     where C denotes the chord length of the main blade.  
   
   
       12 . The rotor blade for a helicopter as claimed in  claim 2 , wherein the blade tip of the small blade protrudes outward by a specific length relative to a tip part of the main blade, and the specific length b 1  is set so as to satisfy a following expression;  
       0.2C≦b 1 ≦0.4C  
     where C denotes the chord length of the main blade.  
   
   
       13 . The rotor blade for a helicopter as claimed in  claim 3 , wherein the blade tip of the small blade protrudes outward by a specific length relative to a tip part of the main blade, and the specific length b 1  is set so as to satisfy a following expression;  
       0.2C≦b 1 ≦0.4C  
     where C denotes the chord length of the main blade.  
   
   
       14 . The rotor blade for a helicopter as claimed in  claim 8 , wherein the angle of incidence is set to be in a range of −5 to +5 degrees.