Helicopter rotor assembly with magnetic particle damper

A helicopter rotor assembly comprising a rotating yoke member, a blade member connected to the yoke member, the blade member being movable relative to the yoke member; and a magnetic particle damper (20). The magnetic particle damper (20), used to dampen motion between the yoke member and the blade (22,24), comprises two conductors (26,30), each attached to one of the movable parts by connecting rods (27,31), with the gap (32) between opposed facing surfaces being filled with dry magnetic particles, and magnets (28,34) mounted respectively on both conductors. - The magnets attached to the conductors produces a magnetic flux, confined to a magnetic flux path defined by the relative magnetically permeable and non-permeable regions of the conductors, which flows across the gap and through the magnetic particles. The magnetic field causes the magnetic particles along the flux path to adhere to one another and to the opposed facing surfaces of the conductors and to produce a force opposing the relative movement of the conductors to one another.