When the destination field elevation is set on the pressurisation control system:
the outflow valves are driven to the full open position automatically to equalise cabin and outside air pressure.
the outflow valves are driven to the full closed position to prevent contaminants entering the cabin through the outflow valves.
the barometric controller adjusts cabin pressure to approximately 0.1psi above ambient pressure (at destination).
the barometric controller adjusts cabin pressure to approximately 0.1psi below ambient pressure (at destination).