The invention provides a retractable aerodynamic system for a motor vehicle including a structure of the vehicle. The system includes at least one aerodynamic flap, a drive mechanism that can rotate the aerodynamic flap about a rotation axis, and at least one member for locking the aerodynamic flap in at least one indexed position with respect to the structure of the vehicle. The locking member is able to transmit forces experienced by the aerodynamic flap to the structure of the vehicle when the aerodynamic flap is locked in the indexed position.