A damper for an airplane landing gear leg comprises a main strut (11) and a rod piston (13) co-operating with the strut (11) to define a main chamber (15) and annular chamber (16) for hydraulic fluid, and presenting internally two adjacent chambers (19, 20) that are isolated from each other by a separator piston (21). The damper (10) further comprises a first secondary strut (26) telescopically slidable on the above-mentioned rod piston (13), and a second secondary strut (37) telescopically slidable on the other end of the first secondary strut (26). The two second annular chambers (31, 40) as defined in this way are respectively connected to associated control circuits thus enabling the total length of the damper to be shortened or lengthened respectively for the purpose of causing the landing gear to contract or to be extended.