The invention relates to an aircraft filter device comprising a hydraulic block adapted to receive removably a filter (2) comprising a vessel (3) receiving a cartridge (4), wherein the vessel is fitted internally with a pin (6) of elastically deformable material comprising firstly a key (8) that extends towards the opening of the vessel and that includes a curved end (9) that projects beyond an edge of the vessel, and secondly a finger (10) that extends towards the bottom of the vessel, and that is oriented towards the center thereof, so that when a cartridge is put into place in the vessel, the finger is pushed back by the cartridge and forces the key to retract so that its curved end no longer projects radially from the vessel, the cartridge being fitted with an external obstacle (14) that co-operates with one end of the finger in order to prevent the cartridge being withdrawn from the vessel.