Aircraft rotor with discrete flap hinge

1. An aircraft rotor assembly, comprising:

a lower hub plate, comprising a cylinder located centrally;

an upper hub plate, comprising a ring located centrally, the ring configured for coupling the upper hub plate to the cylinder of the lower hub plate;

the upper and the lower hub plates adapted to be mounted to a central rotor mast for rotation therewith;

a plurality of radial arms, each arm being connected to at least two flap bearings mounted between the hub plates and forming a discrete flap hinge, each flap hinge defining a flap axis and allowing rotation of the associated arm relative to the hub plates and about the corresponding flap axis; and

a plurality of blade grips, each grip being rotatably connected to one of the arms for rotation about a pitch axis and adapted for mounting of a blade to each blade grip, such that each blade is capable of rotation with the grip about the pitch axis and capable of rotation together with the corresponding arm relative to the hub plates and about the corresponding flap axis;

wherein the at least two flap bearings are rigidly mounted directly to the upper hub plate and the lower hub plate; and

wherein the at least two flap bearings rotate with the upper and lower hub plates.

2. The assembly of claim 1 , wherein each flap hinge comprises coaxial flap bearings.

3. The assembly of claim 1 , wherein each flap hinge comprises a hinge block for carrying the flap bearings, each arm being rotatably connected to one of the hinge blocks.

4. The assembly of claim 1 , wherein each flap hinge comprises a hinge block for carrying the flap bearings, each arm being rotatably connected to one of the hinge blocks; and

wherein each hinge block comprises coaxial flap bearings.

5. The assembly of claim 1 , wherein each flap hinge comprises a hinge block for carrying the flap bearings, each arm being rotatably connected to one of the hinge blocks; and

wherein each hinge block comprises two pairs of coaxial flap bearings, and each arm comprises a pair of inner ends, each inner end being installed between the bearings in one of the pairs of bearings.

6. The assembly of claim 1 , wherein each flap hinge comprises coplanar flap bearings.

7. The assembly of claim 1 , wherein each flap hinge comprises at least a pair of coplanar spherical bearings.

8. The assembly of claim 1 , further comprising:

flap stops configured to limit the amount of relative rotation between the arms and the hub plates.

9. The assembly of claim 1 , wherein a flap hinge offset percentage is between approximately 5% and approximately 12%.

10. An aircraft rotor having a plurality of blades, the rotor comprising:

a lower hub plate, comprising a cylinder located centrally;

an upper hub plate, comprising a ring located centrally, the ring configured for coupling the upper hub plate to the cylinder of the lower hub plate;

the upper and the lower hub plates adapted to be mounted to a central rotor mast for rotation therewith;

a plurality of hinge blocks rigidly mounted between the upper and lower hub plates in a radial array, each hinge block being associated with one of the blades and defining a flap axis for each blade;

a plurality of radial arms, each arm being rotatably connected to one of the hinge blocks for rotation about the corresponding flap axis; and

a plurality of blade grips, each grip being rotatably connected to one of the arms for rotation about a pitch axis and configured for mounting of a blade to each blade grip, such that each blade is capable of flap motion relative to the hub plates about the corresponding flap axis.

11. The rotor of claim 10 , wherein each flap hinge comprises coaxial flap bearings.

12. The rotor of claim 10 , wherein each hinge block comprises two pairs of coaxial flap bearings, and each arm comprises a pair of inner ends, each inner end being installed between the bearings in one of the pairs of bearings.

13. The rotor of claim 10 , further comprising:

flap stops configured to limit the amount of relative rotation between the arms and the hub plates.

14. The rotor of claim 10 , wherein a flap axis offset percentage is between approximately 5% and approximately 12%.

15. An aircraft rotor having a plurality of blades, the rotor comprising:

a lower hub plate, comprising a cylinder located centrally;

an upper hub plate, comprising a ring located centrally, the ring configured for coupling the upper hub plate to the cylinder of the lower hub plate;

the upper and the lower hub plates adapted to be mounted to a central rotor mast for rotation therewith;

a plurality of sets of coplanar flap bearings mounted between the upper and lower hub plates in a radial array, each set of flap bearings being associated with one of the blades and defining a flap axis for each blade;

a plurality of radial arms, each arm being rotatably connected to one of the sets of flap bearings for rotation about the corresponding flap axis; and

a plurality of blade grips, each grip being rotatably connected to one of the arms for rotation about a pitch axis and configured for mounting of a blade to each blade grip, such that each blade is capable of flap motion relative to the hub plates about the corresponding flap axis;

wherein the plurality of sets of coplanar flap bearings rotate with the upper and lower hub plates.

16. The rotor of claim 15 , wherein each set of flap bearings comprises at least a pair of coplanar spherical bearings.

17. The rotor of claim 15 , further comprising:

flap stops configured to limit the amount of relative rotation between the arms and the hub plates.

18. The rotor of claim 15 , wherein a flap axis offset percentage is between approximately 5% and approximately 12%.