Abstract: A device for reducing the vibrations generated on the structure of a helicopter. The helicopter includes a structure with a tail boom and a fin. The structure has a longitudinal vertical mid-plane. The helicopter also has a main lift and propulsion rotor which generate an aerodynamic flow passing through the rotor and induce vibrations on the structure. A damping device for reducing the vibrations has a longitudinal chamber which is equipped with at least one central restriction, which has two elastically urged mobile lateral walls and which is full of a fluid representing an oscillating mass. The damping device is mounted in the tail boom close to the fin so that the direction of travel of the oscillating mass is at least substantially orthogonal to the longitudinal vertical mid-plane.

Abstract: A tail rotor arrangement for rotary wing aircraft, comprising a tunnel of axis X--X transverse with respect to the aircraft and in which is disposed a multi-blade rotor coaxial with respect to the tunnel and generating a transverse air flow. The arrangement comprises a plurality of fixed blades disposed inside of the tunnel downstream of the rotor with respect to the air flow and arranged in at least substantially radial manner with respect to the tunnel in order to be able to recover, in the form of an axial thrust, the energy of rotation of the air flow at the outlet of the rotor. The tail rotor arrangement provides an increase in thrust of the rotors, particularly paired rotors.