Cross beam rotor

Abstract

A helicopter rotor having opposed blades interconnected by a common flexible spar which passes across the rotor axis is connected to the drive shaft by clamped hub plates. A spanwise extending torque tube having a pitch horn at its inner end forms a rigid connection with the spar and blade at its outboard end. A centering bearing assembly is positioned at the inner end of the torque tube and spar to react control loads, centralize the torque tube about the spar, and provide pitch, flap, and lead-lag decoupling.

.Iadd.We claim: .Iaddend. 
     
       1. A helicopter cross beam rotor having a pair of opposed blades supported by a common flexible spar for rotation about an axis of rotation, each blade shaped at its inner end to envelope the spar in spaced relation, the inner end of the blade having a pitch horn to receive control inputs, said blade inner end centered about said spar by a bearing assembly including first and second bearing surfaces to produce relative sliding motion between the spar and blade inner end upon blade pitch angle changes, blade lead-lag, and blade flapwise bending, wherein said first bearing surface is spherical and said second bearing surface is flat.Iadd., and wherein said second bearing surface is located closer to the spar than said first bearing surface. .Iaddend. 
     
     
       2. A helicopter rotor according to claim 1 wherein said first bearing surface accommodates motion produced by blade pitch change and flapwise bending, and said second bearing surface accommodates motion produced by blade lead-lag. .[.3. A helicopter rotor according to claim 1 wherein said second bearing surface is located closer to the spar than said first 
     
     
        bearing surface..]. 4. A helicopter rotor according to claim 1 wherein the blade inner end is a rigid, hollow torque tube and enveloping the spar in spaced relation and having an inner end connected to said pitch horn and 
     
     
        an outer end connected to the remainder of the blade. 5. A helicopter rotor according to claim 1 wherein said bearing assembly comprises dual ball halves and mating sockets located on opposite sides of said spar wherein said sockets are each fixedly attached to the blade inner end, the ball and socket mating surfaces forming said first bearing surfaces, and wherein the inner portions of the ball halves form a flat surface to contact the opposite sides of the spar and forms the second bearing surfaces.