Rigid hydraulic control shaft and a control system for varying the pitch of a propeller

A rigid hydraulic control shaft for conveying a fluid from a hydraulic valve to a hydraulic chamber of a propeller comprises a main segment. The main segment has a hollow rigid outer tube and a solid rigid inner bar. The inner bar has an outer periphery and at least one longitudinal groove disposed along the outer periphery. The outer periphery is configured to move in rotation and translation with an inner periphery of the outer tube. The main segment is configured to move in rotation and in translation with a piston disposed adjacent to the hydraulic chamber.