The system is normally operated and controlled by the cabin pressure controller, incorporating the controls required for selecting desired cabin altitude, rate of change, and barometric setting.

The manual pressurization control system is used to override the automatic system if a malfunction should occur. When using the manual control system, the automatic system will be deactivated and the actuator declutched.

The AUTO/MANUAL selector controls the clutch between the outflow valve actuator and the valves.
In AUTO position (up) the outflow valves are connected to actuator and control of the valve position is governed by the cabin pressure amplifier.

In MANUAL position (down) the clutch is opened and the valves are controlled by the cabin pressure manual control wheel.

The AUTO/MANUAL selector on this picture is in position AUTO and the OUTFLOW VALVE POSITION INDICATOR (2) is in position fully opened.

In manual mode the position of the outflow valve is controlled by the CABIN PRESSURE MANUAL CONTROL WHEEL (1). The wheel is cable connected to the drive shaft of the outflow valve actuator. The wheel is locked into position and must be pressed down before it can be rotated to desired position.





The AUTO/MANUAL selector on this picture is in position MANUAL and the OUTFLOW VALVE POSITION INDICATOR is in position fully opened.




The OUTFLOW VALVE POSITION INDICATOR indicates the relative valve position. The fully closed position forward and the fully open position aft.

Seen here is a position that is normal during cruise. The AUTO/MANUAL selector is auto.