System and method for vibratory motion reduction for a pylon assembly

1. A pedestal assembly for receiving a pylon assembly of a tiltrotor aircraft having a helicopter mode and an airplane mode, the tiltrotor aircraft having an airframe including a fuselage and a wing, the pedestal assembly comprising:

an inboard pedestal supported by the airframe and positioned above the wing or adjacent to the wing, the inboard pedestal includes an inboard bearing assembly;

an outboard pedestal supported by the airframe and positioned above the wing or adjacent to the wing, the outboard pedestal includes an outboard bearing assembly;

the inboard and outboard bearing assemblies are operable to receive the pylon assembly therein such that the pylon assembly is rotatably mounted between the inboard and outboard pedestals along a rotational axis to selectively operate the tiltrotor aircraft between the helicopter mode and the airplane mode;

the inboard bearing assembly comprising an inner member having an opening therein that receives the pylon assembly, an outer member moveably attached to the inner member, a tuning mass attached to the inner member and the outer member such that the vibratory motion of the pylon assembly accelerates the tuning mass, and the inner member comprises a first bearing assembly or the outer member comprises a second bearing assembly;

the outboard pedestal or a portion of the outboard pedestal has a stiffness represented by a spring constant; and

the tuning mass comprises a first chamber disposed around a first portion of the pylon assembly adjacent to a first side of the inner member, a second chamber disposed around a second portion of the pylon assembly adjacent to a second side of the inner member, a tuning port connecting the first chamber to the second chamber, and a tuning fluid disposed within the first chamber and the second chamber, wherein the tuning mass and stiffness of the outboard pedestal or the portion of the outboard pedestal reduce the vibratory motion of the pylon assembly.

2. The pedestal assembly of claim 1 , wherein the tuning mass comprises a mechanical system, a hydraulic system or combination thereof.

3. The pedestal assembly of claim 1 , further comprising a flexible member attached between the inner member and the outer member.

4. The pedestal assembly of claim 3 , wherein the flexible member comprises an elastomer layer, a journal bearing or a plurality of resilient elements.

5. The pedestal assembly of claim 1 , wherein:

the vibratory motion of the pylon assembly causes the inner member to compress at least a portion of the first chamber while simultaneously decompressing at least a portion of the second chamber, or compress at least the portion of the second chamber while simultaneously decompressing at least the portion of the first chamber.

6. The pedestal assembly of claim 1 , wherein the tuning port extends internally through the inner member or the outer member and is not external to the inner member or the outer member.

7. The pedestal assembly of claim 1 , wherein the tuning port is disposed within a housing or external to the housing.

8. The pedestal assembly of claim 1 , wherein:

the first chamber is further disposed adjacent to a first side of the outer member; and

the second chamber is further disposed adjacent to a second side of the outer member.

9. The pedestal assembly of claim 1 , further comprising a housing having an opening extending therein that does to not interfere with the vibratory motion of the pylon assembly, wherein the housing is attached to the outer member, encloses the tuning mass and partially encloses the inner member.

10. The pedestal assembly of claim 1 , wherein the outer member comprises a housing having an opening extending therein that does to not interfere with the vibratory motion of the pylon assembly, and the housing encloses the tuning mass and partially encloses the inner member.

11. A method of reducing a vibratory motion of a pylon assembly of a tiltrotor aircraft having a helicopter mode and an airplane mode, the tiltrotor aircraft having an airframe including a fuselage and a wing, the method comprising:

providing an inboard pedestal supported by the airframe and positioned above the wing or adjacent to the wing, wherein the inboard pedestal includes an inboard bearing assembly comprising an inner member having an opening therein that receives the pylon assembly, an outer member moveably attached to the inner member, and the inner member comprises a first bearing assembly or the outer member comprises a second bearing assembly;

providing an outboard pedestal supported by the airframe and positioned above the wing or adjacent to the wing, wherein the outboard pedestal includes an outboard bearing assembly, and the outboard pedestal or a portion of the outboard pedestal has a stiffness represented by a spring constant;

providing the pylon assembly operably mounted in the inboard and outboard bearing assemblies such that the pylon assembly is rotatably mounted between the inboard and outboard pedestals along a rotational axis to selectively operate the tiltrotor aircraft between the helicopter mode and the airplane mode;

providing a tuning mass attached to the inner member and the outer member of the inboard bearing assembly, wherein the tuning mass comprises a first chamber disposed around a first portion of the pylon assembly adjacent to a first side of the inner member, a second chamber disposed around a second portion of the pylon assembly adjacent to a second side of the inner member, a tuning port connecting the first chamber to the second chamber, and a tuning fluid disposed within the first chamber and the second chamber; and

reducing the vibratory motion the pylon assembly using the tuning mass and the stiffness of the outboard pedestal or the portion of the outboard pedestal.

12. The method of claim 11 , further comprising configuring the tuning mass and the stiffness of the outboard pedestal or the portion of the outboard pedestal to reduce the vibratory motion of the pylon assembly.

13. The method of claim 11 , further comprising:

determining the spring constant; and

adjusting the tuning mass to reduce the vibratory motion the pylon assembly based on the spring constant.