Propeller pitch control system

A control system for controlling the pitch of a propeller, the propeller having blades designed to be driven in rotation by a propeller shaft, each blade being configured to pivot about a substantially radial axis of the blade, the system comprising:

• the propeller shaft;
• a blade swivel device comprising a rotary control element suitable for placing the blades in an angular position corresponding to a desired propeller pitch as a function of rotation of said rotary control element relative to the propeller shaft;
• a transmission presenting an outlet member that is coupled to rotate with the rotary control element of the blade swivel device;
• and
• a variable speed drive;
• wherein
• the variable speed drive has a drive rotor, a control rotor, and an outlet rotor;
• said drive, control, and outlet rotors are coupled to rotate respectively with a drive member that is the propeller shaft, with a control member, and with the outlet member of the transmission, and consequently the speeds of rotation of the drive, control, and outlet rotors are proportional respectively to the speeds of rotation of the drive, control, and transmission outlet members;
• and
• the variable speed drive is configured to drive the outlet rotor in rotation at a speed that is a predetermined function of the speeds of rotation of the drive and control rotors.