This SAE Aerospace Information Report (AIR) presents an overview of the application and control of fixed and variable displacement pumps with the emphasis on the controls most commonly used on variable displacement pumps. It describes various options to control the operation of hydraulic pumps in terms of controlling the pump output pressure and/or flow and assisting in the selection of the pump. Purpose The information contained herein is intended to provide application information to assist system integrators in selecting the most appropriate pump controls for a given application. It can also be used as an introduction to pump designers.