Vibration control system

A rotary wing aircraft comprising:

• an airframe;
• a rotor mounted to the airframe;
• one or more engines operably connected to the rotor via a gearbox for driving rotation of the rotor;
• and
• one or more vibration control systems operably connected to the gearbox, each vibration control system including:
• four mass discs disposed at a central axis and rotatable thereabout, each mass disc including a mass secured thereto wherein rotation of the four mass discs creates a vibratory force output;
• and
• a power transfer assembly disposed between adjacent mass discs of the four mass discs and configured to transfer rotational energy between the adjacent mass discs including:
• a power transfer shaft rotatable about a power transfer shaft axis;
• and
• a power transfer disc connected to the power transfer shaft and in frictional contact with each of the adjacent mass discs at a contact point, wherein when the power transfer shaft is rotated about the power transfer shaft axis, a radial location of the contact point at each of the adjacent mass discs relative to the central axis is changed thereby altering the vibratory force output;
• wherein each mass disc of the four mass discs includes a concave recess wherein the contact point is disposed.

A method for controlling vibration of an airframe of a rotary wing aircraft comprising:

• disposing one or more vibration control systems in operable communication with a gearbox of the rotary wing aircraft, each vibration control system including:
• four mass discs disposed at a central axis and rotatable thereabout, each mass disc including a mass secured thereto;
• and
• a power transfer assembly disposed between adjacent mass discs of the four mass discs including:
• a power transfer shaft rotatable about a power transfer shaft axis;
• and
• a power transfer disc connected to the power transfer shaft and in frictional contact with each of the adjacent mass discs at a contact point;
• wherein each mass disc of the four mass discs includes a concave recess wherein the contact point is disposed;
• driving rotation of a first mass disc of the four mass discs about the central axis via an operable connection to the gearbox;
• transferring rotational energy from the first mass disc to a second mass disc of the four mass discs via the power transfer disc disposed between the mass discs to generate a vibratory force;
• and
• rotating the power transfer shaft about the power transfer shaft axis;
• and
• moving a first contact point at the first mass disc to a radial position different than a second contact point at the second mass disc, thereby changing a rotational speed of the second mass disc relative to a rotational speed of the first mass disc to alter the vibratory force.