What is the purpose of pressurizing a hydraulic reservoir?

The purpose of pressurizing a hydraulic reservoir is to ensure a consistent and positive feed of foam-free fluid to the hydraulic pump. By maintaining pressure in the reservoir, the hydraulic system can effectively manage the fluid flow and avoid the presence of air or foam, which can compromise the efficiency and performance of the hydraulic system. Foam can lead to cavitation in the pump, which reduces efficiency and could potentially cause damage. Therefore, pressurized conditions help maintain optimal fluid characteristics and support the reliability of the hydraulic system. This is crucial for system operation, enabling smooth actuation of hydraulic components and providing the necessary force for aircraft controls or landing gear operations.