Dual mode rotor hub assembly

1. A rotor hub assembly for a rotary aircraft, comprising:

a swashplate;

an attachment device rotatably coupled to the swashplate and pivotally coupled to a rotor blade;

a first damper operably associated with the attachment device configured to dampen forces exert by the rotor blade during flight, the first damper comprising:

a fluidly sealed chamber having:

a first fluid reservoir;

a second fluid reservoir; and

a conduit in fluid communication with the first reservoir and the second reservoir

a valve in fluid communication with the conduit, the valve being configured to restrict fluid passage between the first fluid reservoir and the second fluid reservoir

an elastomeric seal configured to elastically resist rotational movement of the attachment device relative to the swashplate;

wherein a first spring rate is created by the elastic resistance from the elastomeric seal as the fluid is restricted from channeling through the conduit; and

wherein a second spring rate is created by the elastic resistance from the elastomeric seal and the fluid passing between the first fluid reservoir and the second reservoir; and

a second damper operably associated with the attachment device and configured to dampen forces from the rotor blade.

2. The rotor hub assembly of claim 1 , further comprising:

a centrifugal bearing operably associated with the rotor blade;

wherein the centrifugal bearing is configured to dampen centrifugal forces from the rotor blade.

3. The rotor hub assembly of claim 1 , the swashplate comprising:

an upper driver plate; and

a lower driver plate;

wherein the attachment device is position between the upper driver plate and the lower driver plate; and

wherein the attachment device rotatably attaches to upper driver plate and the lower driver plate.

4. The rotor hub assembly of claim 1 , the attachment device comprising:

a bearing system carried by the attachment device and configured to pivotally attach the rotor blade to the attachment device.

5. The rotor hub assembly of claim 4 , the bearing system comprising:

a shaft; and

a bearing configured to receive the shaft;

wherein the rotor blade couples to the shaft and pivots relative to the attachment device via the bearing.

6. The rotor hub assembly of claim 1 , the attachment device comprising:

a longitudinal body;

a first arm and a second arm, both arms being attached to and extending from the longitudinal body;

a bearing system carried by the first arm and the second arm; and

a shaft rotatably supported by the first arm and the second arm via the bearing system;

wherein the rotor blade couples to the shaft and pivots relative to the attachment device via the bearing system.

7. The rotor hub assembly of claim 6 , the swashplate comprising:

an upper driver plate; and

a lower driver plate;

wherein the longitudinal body rotatably attaches to the upper driver plate and the lower driver plate.

8. A method, comprising:

rotatably attaching an attachment device to a swashplate, the attachment device being configured to rotate relative to the swashplate;

pivotally attaching a rotor blade to the attachment device, the rotor blade being configured to pivot relative to the attachment device;

damping the rotational movement of the attachment device with a first damper and a second damper; and

switching the damping effects of the first damper and the second damper between a first spring rate and a second spring rate during flight.

9. The method of claim 8 , wherein switching the spring rate is achieved by controlling fluid passage between two fluid reservoirs disposed within the damper.

10. The method of claim 9 , wherein damping the rotational movement is achieved by elastomeric material disposed within the first damper and the second damper.