This Technical Note describes the dynamical simulation of a reservoir pressurizing system. The simulation is based on a MATLAB/Simulink program. The system consists mainly of restrictors, supply lines, a reservoir pressurization unit, a reservoir relief valve and a hydraulic reservoir. Each component is described by an independent model block. The different flow resistances are based on analytical functions or characteristic maps. Inside the supply lines heat transfer via the duct wall respectively the insulation takes place.