Normally the reservoir pressurization system supplies bleed air pressure from either the engines,
APU or external ground air cart to pressurize the system 'A' and system 'B' hydraulic reservoirs. The
reservoir pressurization system can also be manually pressurized for ground maintenance by
connection of an external ground air source to an air charging valve located in the right main landing
gear wheel well. The air charging valve permits manual depressurization and pressurization of the
reservoirs for ground maintenance.