An undercarriage (2) having anticrash and antiresonance skids (6) for a rotary wing aircraft (1), the undercarriage including in particular: two landing skids (6) that are elastically deformable in the event of a normal landing; front and rear transverse elements (7, 8) likewise elastically deformable in the event of a normal landing; assembly elements (9, 14) for assembling the transverse elements to a force take-up structure (5) of the aircraft (1); and a connection system (10) suitable for absorbing the energy of a crash landing by controlled plastic deformation and including at least one pair of buckling struts (11) arranged so as to deform in the plastic range by buckling, together with a fastener member (14) of the assembly elements for providing statically-redundant assembly between a structure (5) of the aircraft (1) and a respective one of the front and/or rear elements (7, 8).