A system for controlling aircraft gas, including: - a main shaft, which defines a main axis, which is freely rotary mounted about the main axis relative to a frame of the aircraft, and whose angular position about the main axis controls a propulsion of the aircraft, - a lever, which is integrally connected in rotation about the main axis to the main shaft and which can be manually actuated by a pilot, - friction connection means, which are functionally interposed without clearance between the main shaft and the frame and which are adapted to prevent by friction the driving of the main shaft in rotation about the main axis relative to the frame by applying a first resistance, this first resistance being provided to be surpassed by the pilot acting manually on the lever to drive the main shaft in rotation about the main axis, and - an automatic regulation device, which is capable of automatically controlling the driving of the main shaft in rotation about the main axis and which comprises: - a gear motor unit, fixedly carried by the frame and having an outlet which can be driven in displacement relative to the frame by a motor and a gear unit of the gear motor unit, - mechanical coupling means, which are adapted to transmit, without clearance and reversibly, the movement between the outlet of the gear motor unit and the main shaft via the friction connection means, so that, by actuation of the gear motor unit, to ensure a rotation of the main shaft about the main axis relative to the frame as long as a resistance to this rotation remains less than the first resistance, and - brake means which are distinct from the coupling means, these brake means being fixedly carried by the frame and being adapted to prevent the driving in displacement of the outlet of the gear motor unit relative to the frame by applying a second resistance which is greater than the first resistance. - a main shaft, which defines a main axis, which is freely rotary mounted about the main axis relative to a frame of the aircraft, and whose angular position about the main axis controls a propulsion of the aircraft, - a lever, which is integrally connected in rotation about the main axis to the main shaft and which can be manually actuated by a pilot, - friction connection means, which are functionally interposed without clearance between the main shaft and the frame and which are adapted to prevent by friction the driving of the main shaft in rotation about the main axis relative to the frame by applying a first resistance, this first resistance being provided to be surpassed by the pilot acting manually on the lever to drive the main shaft in rotation about the main axis, and - an automatic regulation device, which is capable of automatically controlling the driving of the main shaft in rotation about the main axis and which comprises: - a gear motor unit, fixedly carried by the frame and having an outlet which can be driven in displacement relative to the frame by a motor and a gear unit of the gear motor unit, - mechanical coupling means, which are adapted to transmit, without clearance and reversibly, the movement between the outlet of the gear motor unit and the main shaft via the friction connection means, so that, by actuation of the gear motor unit, to ensure a rotation of the main shaft about the main axis relative to the frame as long as a resistance to this rotation remains less than the first resistance, and - brake means which are distinct from the coupling means, these brake means being fixedly carried by the frame and being adapted to prevent the driving in displacement of the outlet of the gear motor unit relative to the frame by applying a second resistance which is greater than the first resistance. - a gear motor unit, fixedly carried by the frame and having an outlet which can be driven in displacement relative to the frame by a motor and a gear unit of the gear motor unit, - mechanical coupling means, which are adapted to transmit, without clearance and reversibly, the movement between the outlet of the gear motor unit and the main shaft via the friction connection means, so that, by actuation of the gear motor unit, to ensure a rotation of the main shaft about the main axis relative to the frame as long as a resistance to this rotation remains less than the first resistance, and - brake means which are distinct from the coupling means, these brake means being fixedly carried by the frame and being adapted to prevent the driving in displacement of the outlet of the gear motor unit relative to the frame by applying a second resistance which is greater than the first resistance.