Rotor hub for a helicopter

Claim 1

A rotor assembly for a helicopter comprising, a rotor mast having a lower conical section and an upper cylindrical section, said lower conical section being adaptable for attachment to a fuselage of a helicopter, bearing means on said cylindrical section of said rotor mast, a rotor hub having a lower cylindrical section, an upper conical section having an open end, and an annular flange, said cylindrical section being rotatably supported by said bearing means on said cylindrical section of said rotor mast, a flexible hub plate having a central flat plate section attached to said annular flange on said rotor hub and having a plurality of radially extending pitch axles, said central flat plate section having a width substantially greater than its thickness to provide a bending stiffness in the plane of rotation higher than the bending stiffness normal to the plane of rotation, a torque plate closing the open end of said upper conical section of said rotor hub whereby said rotor mast, rotor hub and torque plate form an air plenum, a plurality of rotor blades pivotally attached one each to each said pitch axle, a plurality of flexible ducts connected one each between each rotor blade and said air plenum, valving means within said air plenum for regulating flow of air through said flexible ducts to said rotor blades, and shaft means engaging said torque plate for rotating said rotor hub.