Patent ID: 8622375

Claim:
A dual frequency damper for a rotorcraft, the dual frequency damper comprising: a first connection member; a second connection member; a vibration eliminator portion comprising: a primary housing coupled to the first connection member; a central member resiliently attached to the primary housing with an inboard elastomer member and an outboard elastomer member; a tuning passage located in the central member, the tuning passage configured to provide fluid communication between an inboard fluid chamber and an outboard fluid chamber; a tuning fluid disposed in the tuning passage, inboard fluid chamber, and the outboard fluid chamber; a fluid damper portion comprising: a piston rigidly coupled to the second connection member, the piston dividing an interior of the first housing into a first fluid chamber and a second fluid chamber; a fluid passage in the piston, the fluid passage being configured to provide fluid communication between a first fluid chamber and a second fluid chamber; and a fluid disposed in the fluid passage, the first fluid chamber, and the second fluid chamber; wherein the piston is resiliently coupled to the central member of the vibration eliminator portion.