Abstract: The bidirectional suspension comprises, in order to connect the transmission gearbox to the fuselage, two parallel connecting rods which are articulated to lateral supports on opposite sides of the base of this gearbox and on the same side of the latter as far as their articulations to two transverse levers, each articulated to the fuselage about an axis perpendicular to the connecting rods and substantially parallel to the axis of the rotor. Each of the two levers lie substantially in the extension of the other and are connected to each other via their adjacent ends. Means providing elastic linkages in the direction of the connecting rods and in the direction perpendicular to the latter connect the fuselage to the gearbox and may consist of a single elastic pad.