Vibration attenuator

A vibration attenuator for an aircraft having a rotor rotating about a mast axis, the attenuator comprising:

• an upper weight assembly comprising an arm and an upper weight, the center of gravity of the upper weight being a radial distance from the mast axis;
• a lower weight assembly comprising an arm and a lower weight, the center of gravity of the lower weight being the radial distance from the mast axis;
• and
• a first motor configured for selectively translating one weight assembly relative to the other weight assembly along the mast axis between a minimum-moment configuration, in which the centers of gravity of the weights revolve about the mast axis in the same plane, and a maximum-moment configuration, in which the centers of gravity of the weights revolve about the mast axis in different planes;
• wherein the upper and lower weight assemblies are configured for rotation together relative to the rotor at a selected angular rate about the mast axis, the weights being located on opposing sides of the mast axis.

An aircraft, comprising:

• at least one rotor rotatable about a mast axis;
• a vibration attenuator, comprising:
• upper and lower weight assemblies, each comprising a weight with a center of gravity being a radial distance from the mast axis, the weight assemblies being configured for rotation together relative to the rotor at a selected angular rate about the mast axis, the weights being located on opposing sides of the mast axis;
• and
• a first motor configured for selective translation of one of the weight assemblies relative to the other of the weight assemblies along the mast axis between a minimum-moment configuration, in which the centers of gravity of the weights revolve about the mast axis in the same plane, and a maximum-moment configuration, in which the centers of gravity of the weights revolve about the mast axis in different planes for producing a whirling moment about the mast axis.