Abstract: A device for locking and unlocking a rotor to a stator, at least parallel to the rotation axis of the rotor, includes an annular rotor flange transverse to the axis, an annular stator bearing surface transverse to the axis and at least partly axially facing the annular flange, and a mobile annular bearing surface transverse to the axis and at least partially axially facing the annular flange on the opposite side of the stator annular bearing surface. The mobile annular bearing surface is formed on a thrust ring coupled radially to a stator portion and able to move axially relative thereto. An annular inflatable airbag in the stator portion axially between a stator back and the thrust ring is provided with pneumatic fluid inlet/outlet arrangements.