Copyright D.P. Browne 2011

Pneumatics : Pressurization

There are several pressurized zones in t he aircraft.  These are :

The aircraft pressurization is a simple system. It lets the cabin air conditioning cool air from the packs build up a pressure in the cabin, which is maintained by controlling how much cabin air escapes from the two cabin vents.

Air in from the PACKS

Air out from the Cabin Vents

Cabin Pressure Controller

Vent Extract Motors

There are two systems to control the cabin pressure Only one is operative at any one time with the other being a back up in case of failure. The back up switch over is automatic.

The vent extracts are driven by 3 motors. One motor is active at any one time. One motor is controlled from the Cabin Pressure Controller 1 (CPC1) , the other is from CPC 2 and a third is manually controlled from the cockpit in case both CPCs fail.

The two vents are called Forward and Aft, and their position along wit the status of the CPCs are cabin pressure values are shown on the Pressure System Display.

In addition to the two vents, there is a safety vent in case the cabin is over pressurized.

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