A device for improving performance of an aircraft with a propeller includes a constant torque blade setting device that slaves, automatically and independently, blade setting angles, respectively associated with blades of the propeller, to a constant reference control moment predetermined, for a desired propeller thrust value. The blade setting angles are intended to be applied on each blade such that torsion aerodynamic moments applied on blades stay roughly equal to the reference control moment regardless of the angular position of blades in the propeller plane. A corresponding method for improving performance of an aircraft includes the use of the constant torque blade setting device to slave blade setting angles to a constant reference control moment.