The invention relates to an architecture for a hydraulic system for operating the landing gear of an aircraft including at least one pressure source and at least one hydraulic return, the system having a hydraulic circuit comprising a first hydraulic line that, when pressurized, causes the landing gear to be lowered, and a second hydraulic line that, when pressurized, causes the landing gear to be raised, said lines being selectively pressurized by means of a hydraulic distribution member comprising at least an isolation valve and a selector for putting one of the lines into communication with pressure and the other line into communication with return. According to the invention, the architecture includes passive bypass means for bypassing the selector, said means being disposed between the second line and an admission line that extends between the isolation valve and the selector, and forced return connection means for forcing the isolation valve to isolate the pressure circuit of the aircraft and connect the admission line to return.