The Hydraulic Reservoir (HR) is a conventional self-pressurizing (bootstrap) separated type according to general requirements of MIL-R-8931 and/or SAE AS5586.

The system high pressure provides the necessary amount of pressurization of the fluid into the HR by a differential area piston.

The Hydraulic Reservoir contains the amount of fluid the system needs to supply the hydraulic pumps under all operational conditions and air vehicle attitudes and to compensate for the system leakage allowance. It also accommodates the thermal expansion of the fluid within the circuit.

The Reservoir is composed by a piston whose high-pressure portion is connected to the system supply pressure and low-pressure portion is connected to the pump suction and to the return port of the HPS.