Sealed hub and shaft fairing for rotary wing aircraft

Abstract

An aircraft includes an airframe; an extending tail; a counter rotating, coaxial main rotor assembly including an upper rotor assembly and a lower rotor assembly; a translational thrust system positioned at the extending tail, the translational thrust system providing translational thrust to the airframe; an upper hub fairing positioned at the upper rotor assembly; a lower hub fairing positioned at the lower rotor assembly; and a shaft fairing disposed between the upper hub fairing and the lower hub fairing; wherein a geometry of at least one of the upper hub fairing and the lower hub fairing progressively blends from a circle to a series of curved elliptical surfaces in an inboard direction.

What is claimed is: 
     
         1 . An aircraft comprising:
 an airframe;   an extending tail;   a counter rotating, coaxial main rotor assembly including an upper rotor assembly and a lower rotor assembly;   a translational thrust system positioned at the extending tail, the translational thrust system providing translational thrust to the airframe;   an upper hub fairing positioned at the upper rotor assembly;   a lower hub fairing positioned at the lower rotor assembly; and   a shaft fairing disposed between the upper hub fairing and the lower hub fairing;   wherein a geometry of at least one of the upper hub fairing and the lower hub fairing progressively blends from a circle to a series of curved elliptical surfaces in an inboard direction.   
     
     
         2 . The aircraft of  claim 1 , wherein:
 the at least one of the upper hub fairing and the lower hub fairing includes a hub body and a plurality of hub shank regions, wherein portions of the hub body between the hub shank regions are locally thinner, while retaining a necessary thickness at the shank extension regions.   
     
     
         3 . The aircraft of  claim 1 , wherein:
 the upper rotor assembly and the lower rotor assembly include a plurality of rotor blades, and a vertical face seal is positioned about an outer mold line of at least one of the plurality of rotor blades.   
     
     
         4 . The aircraft of  claim 3 , wherein:
 a running surface of the vertical face seal is configured to seal a hub shank region of the hub fairing around a blade spanwise axis of the at least one of the plurality of rotors blade.   
     
     
         5 . The aircraft of  claim 3 , wherein:
 the vertical face seal is supported by the at least one of the upper hub fairing and the lower hub fairing.   
     
     
         6 . The aircraft of  claim 3 , wherein:
 the vertical face seal creates a constant running gap.   
     
     
         7 . The aircraft of  claim 1 , wherein the upper hub fairing is substantially sealed to the shaft fairing and the lower hub fairing is substantially sealed to the shaft fairing. 
     
     
         8 . The aircraft of  claim 1  wherein:
 the upper hub fairing is countered to match an upper surface of the shaft fairing. 
 
     
     
         9 . The aircraft of  claim 1  wherein:
 the lower hub fairing is countered to match a lower surface of the shaft fairing. 
 
     
     
         10 . The aircraft of  claim 1  wherein:
 the shaft fairing is generally airfoil shaped. 
 
     
     
         11 . The aircraft of  claim 1  wherein:
 the shaft fairing is shaped to minimize drag. 
 
     
     
         12 . The aircraft of  claim 1  wherein:
 the upper hub fairing, lower hub fairing and shaft fairing are disposed about an axis of rotation of the main rotor assembly. 
 
     
     
         13 . The aircraft of  claim 1  wherein:
 the main rotor assembly is a rigid rotor system.