SEALED HUB AND SHAFT FAIRING FOR ROTARY WING AIRCRAFT
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.
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.