Abstract: The suspension device is interposed between the rotor and the fuselage of the helicopter for filtering the vibration exciting forces and moments coming from the rotor. In this helicopter, a speed reducer (1) is provided in a housing mounted on the fuselage (22) by rigid oblique bars (28). According to the invention, there are disposed around the housing of the speed reducer, in a number equal to the number of rigid oblique bars (28), monodirectional antiresonant means (20,21,23,23a,23b,25) connecting the upper ends of the rigid oblique bars (28) to the speed reducer (1).

Abstract: In this elastic strut incorporating a hydromechanical resonator having a weight/spring system of the type providing a hydraulic amplification of the displacement of the beating weight (7), the weight mounted between two opposed return springs constitutes a double-sided hollow piston slidably mounted on two coaxial opposed cylinders (6) in a closed chamber filled with a liquid (10) in an inner tubular element (1) disposed in an outer tubular element (2) with which it defines, at each end, a chamber (18, 26) filled with liquid onto which opens one of the cylinders (6), the elements (1, 2) constituting the body of the strut being coaxially movable relative to each other and fixed together at each of their ends in a sealed and elastic manner by bearings composed of an elastomer material.

Abstract: The device comprises four identical assemblies evenly spaced apart about the vertical axis of a speed reducer (1), offset 90.degree. from each other and each comprising an isotropic flexible beam (4) carrying a beating weight (14) and connected by its ends to the fuselage, this beam being perpendicular to the vertical axis, and rigid triangulation means (9, 10) connecting the speed reducer (1) to the beam (4) so as transmit its forces and its moments to the beam in a plane parallel to an offset from said vertical axis of the speed reducer (1).