Bearingless hub structure for rotary-wing aircrafts

A bearingless hub structure for rotary-wing aircraft comprising:

• a hub body secured to a rotor shaft;
• a plurality of radially extending flexbeams integrally formed with said hub body;
• pitch housings enclosing respective ones of said flexbeams in spaced relationship;
• each 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 in the vicinity of a root end of said flexbeam by spherical bearing means;
• each of said flexbeams including a first flexible portion having a low lead-lag stiffness and a second flexible portion located radially outside said first flexible portion and having a low torsional stiffness;
• said first flexible portion including a pair of beams which extend radially outward, said beams having radially inner ends spaced in the lead-lag direction, and the distance between said beams decreasing in the radially outward direction;
• said beams having radially outer ends connected to a radially inner end of said second flexible portion;
• and
• stopper means provided for cooperation with said first flexible portion for preventing said flexbeam from further deflection with respect to the pitch housing when a deflection in the lead-lag direction of the flexbeam reaches a predetermined value.