Abstract: A bearingless hub structure for a rotary-wing aircraft is provided, the structure including a hub body adapted to be securely connected to a rotor mast, a plurality of flexible beam members provided integrally with the hub body to extend radially outwardly, a pitch housing encircling each of the flexible beam members, and having a radially outward end portion which is rigid with a radially inward end portion of a rotor blade, a spherical bearing positioned adjacent to a radially inward end portion of the flexible beam member for supporting the pitch housing, a lead-lag damper positioned between the flexible beam member and the pitch housing, and the flexible beam members each having a flexible plate portion which is of a low bending rigidity in a flapping direction, a flexible portion provided radially outwardly of the flexible plate portion having a low bending rigidity in the lead-lag direction, and a twist-flex portion provided radially outwardly of the flexible portion.

Abstract: A bearingless hub structure for rotary-wing aircrafts comprising a hub body ecured to a rotor shaft, a plurality of radially extending flexbeams integrally formed with the hub body, and pitch housings enclosing each of the flexbeams in spaced relationship, the pitch housing having a radially outer end portion rigidly secured to an inboard end of a rotor blade and a radially inner end portion supported by a spherical bearing in the vicinity of a root end of said flexbeam.The flexbeam consists of a flexible element of low lead-lag stiffness and a torsion element of low torsional stiffness located radially outside the flexible element. The flexible element consists of two beam-like members having radially inner ends spaced in the lead-lag direction and extending radially outward with narrowing the distance between them, the beam-like member having radially outer end connected to a radially inner end of the torsion element.