US Patent 7758310 Translational thrust system for a rotary wing aircraft

A translational thrust system for a high speed rotary-wing aircraft includes a propeller system driven by a propeller gearbox, a hydraulic system, and a mechanical-hydraulic control system. The mechanical-hydraulic control system utilizes a hydraulic fluid which travels to and from a propeller dome via an oil transfer/position feedback tube which translates with a propeller pitch change piston. Translation of the oil transfer/position feedback tube and the propeller pitch change piston pitches the blades between high (coarse) and low (fine) pitch positions.