The Evolution of the Hydraulic Pump as Applied to Aircraft

Abstract Having passed through a period of manual control of auxiliary power functions on earlier aircraft, and later the hand-pump and low-pressure vane- and gear-pump stages, continued demands for higher pressure eventually led to the present-day types of piston pumps which supply necessary power to hydraulic systems of control. The author outlines the basic requirements for well-designed oil-hydraulic equipment including pumps, and then in detail describes the gear pump and the axial-piston pump in both the constant- and variable-delivery designs. Considerations in selecting pumping equipment and the design of the hydraulic circuit are stated.