Rotor systems and methods

1. An aircraft rotor system comprising:

a hub having a hub axis about which the hub is configured to rotate; and

a plurality of rotor blades configured to extend from the hub and rotate about the hub axis, at least one of the rotor blades rotatable about a respective pitch change axis;

wherein the hub is configured to be rotated about the hub axis only by the plurality of rotor blades.

2. The system according to claim 1 , further comprising a pitch control mechanism operably associated with the hub and the at least one of the rotor blades rotatable about a pitch change axis; the pitch control mechanism configured to rotate the at least one of the rotor blades rotatable about the respective pitch change axis to control the pitch thereof.

3. The system according to claim 2 , wherein the hub comprises a rotatable housing and a non-rotatable housing.

4. The system according to claim 3 , wherein the at least one of the rotor blades rotatable about a respective pitch change axis comprises a rotor blade assembly rotatably coupled to the rotatable housing.

5. The system according to claim 4 , wherein the rotor blade assembly includes a rotor blade and a pitch horn associated therewith.

6. The system according to claim 5 , wherein the pitch control mechanism comprises an actuator assembly disposed on the non-rotatable housing of the hub and a spider assembly translatable along at least a portion of the hub axis by the actuator assembly.

7. The system according to claim 6 , wherein the actuator assembly comprises at least one of the following: a linear actuator, a bell crank mechanism, and a geared system.

8. The system according to claim 6 , wherein the actuator assembly receives input from a pilot on an aircraft including the aircraft rotor system, a user remote from an aircraft including the aircraft rotor system, and/or a flight control computer.

9. The system according to claim 6 , wherein the spider assembly is rotated about the hub axis by the pitch horn.

10. An aircraft rotor system comprising:

a hub having a hub axis about which the hub is configured to rotate;

an externally driven rim configured to rotate about the hub axis, the externally driven rim configured to be rotated by a driving member; and

a plurality of rotor blades operably coupled to the externally driven rim and the hub, at least one of the rotor blades rotatable about a respective pitch change axis;

wherein the externally driven rim is configured to rotate the plurality of rotor blades and the hub about the hub axis.

11. The system according to claim 10 , further comprising a pitch control mechanism operably associated with the hub and the at least one of the rotor blades rotatable about the pitch change axis; the pitch control mechanism configured to rotate the at least one of the rotor blades rotatable about the respective pitch change axis to control the pitch thereof.

12. The system according to claim 10 , wherein the at least one of the rotor blades rotatable about the respective pitch change axis comprises a rotor blade assembly including a rod disposed between the hub and the externally driven rim, the rod being associated with a rotor blade and configured to permit rotation of the rotor blade about the respective pitch change axis.

13. The system according to claim 12 , wherein the rod is configured to rotate the hub about the hub axis.

14. The system according to claim 12 , wherein the rod passes through a channel disposed in the rotor blade.

15. The system of claim 10 , wherein the driving member is disposed adjacent to the externally driven rim.

16. The system of claim 15 , wherein the driving member is configured to provide mechanical energy from a power source.

17. The system of claim 16 , wherein the power source is mechanical, hydraulic, and/or electric.

18. The system of claim 10 , wherein the driving member and the externally driven rim do not require engagement therebetween.

19. The system of claim 10 , wherein the driving member comprises a plurality of driving members disposed adjacent to the externally driven rim.

20. A method of operating an aircraft rotor system comprising:

providing a rotor assembly, comprising:

a hub having a hub axis about which the hub is configured to rotate;

an externally driven rim configured to rotate about the hub axis, the externally driven rim configured to be rotated by a driving member;

a plurality of rotor blades configured to extend from the hub and rotate about the hub axis, each of the rotor blades rotatably coupled to the hub and the externally driven rim such that rotation of the externally driven rim rotates the plurality of rotor blades and the hub about the hub axis, at least one of the rotor blades rotatable about a respective pitch change axis;

a pitch control mechanism operably associated with the hub and the at least one of the rotor blades rotatable about the respective pitch change axis;

providing a driving member disposed adjacent to the externally driven rim;

rotating the driving member to impart rotation to the externally driven rim, the plurality of rotor blades, and the hub about the hub axis; and

actuating the pitch control mechanism to rotate the at least one of the rotor blades rotatable about the respective pitch change axis to control the pitch thereof.