21-20 Pressurisation

Question 1

What is the maximum positive differential pressure of the aircraft?

Answer 1

9.0psi

Question 2

What is the maximum negative differential pressure of the aircraft?

Answer 2

-1.0psi

Question 3

What is the safety relief valve setting?

Answer 3

8.6psi

Question 4

Cabin altitude warning at?

Answer 4

9550ft

Question 5

Maximum normal cabin altitude?

Answer 5

8000ft

Question 6

What does CPC stand for? How many are there?

Answer 6

Cabin Pressure Controller (x2)

Question 7

When does a transfer of CPC take place?

Answer 7

70 seconds after landing or when one fails

Question 8

What information does the CPC use from the FMGC?

Answer 8

Landing elevation and landing QNH

Question 9

What information does the CPC use from the ADIRS?

Answer 9

Pressure altitude

Question 10

In automatic pressure control mode, how many phases of flight are there? What are they?

Answer 10

6

GROUND (GN): Outflow valve fully open
TAKEOFF (TO): Pre-pressurises to difference of +0.1 psi
CLIMB (CL): Uses aircraft climb rate
CRUISE (CR): Maximum 8000ft cabin altitude
DESCENT (DE): Maximum cabin rate of -750ft/m, and pressurises aircraft to landing field pressure + 0.1psi
ABORT (AB): No climb after takeoff? Cabin pressure set back to +0.1psi

FCOM 21-20-30

Question 11

For how long must you leave the cabin pressure MODE SEL in MAN before returning it to AUTO to force a transfer to the other system?

Answer 11

At least 10 seconds

FCOM 21-20-40

Question 12

Describe components of the pressurisation system

Answer 12

2 CPCs- controlling pressurisation schedule sending/receiving signals to the other components

1 outflow valve- to release air from the cabin to maintain a certain cabin pressure

2 safety valves- protect against under or over pressure

Cockpit control panel- to control the system in manual mode

Question 13

When do the CPCs change over?

Answer 13

70s after touchdown

Question 14

How many pressurisation modes are there?

Answer 14

4
Pre pressurisation
Pressurisation
Depressurisation
Ground mode

Question 15

What happens in pre pressurisation mode?

Answer 15

During Take off roll, outflow valves motors towards closed so that the pressure in the cabin increases to 0.1psi to avoid cabin surge at rotation

Question 16

How does pressurisation function during climb, cruise and descent?

Answer 16

CLB: activates at lift off and pressurised on schedule based on rate of climb
Cruise: maintained at cabin altitude at level off or LDG elevation whatever is higher
DES: calculates a descent schedule based on landing elevation so that landing cabin altitude is 0.1psi above ambient

Question 17

Max cabin rate of descent?

Answer 17

750fpm

Question 18

When do depressurisation and ground modes activate?

Answer 18

Depressurisation starts at touchdown, releasing any cabin over pressure
Ground mode 5s after touchdown, outflow valves motors to full open to release all pressure

Question 19

Max cabin altitude in auto mode?

Answer 19

8000ft

Question 20

What does pressurisation system use as reference for LDG elev?

Answer 20

QNH from perf APPR page and airport elevation from FMGC

Question 21

How does manual pressurisation work?

Answer 21

Use man mode button on overhead panel. Power switches to 3rd motor for outflow valve.
Control using dedicated part of CPC1 which is still available if CPC1+2 fail.

Cabin alt controlled using toggle switch which adjusts the outflow valve

Question 22

What QRH procedures are there for pressurisation?

Answer 22

Cabin overpressure

Switching off the packs and opening the blower and extract to vent pressure

Question 23

QRH advisories for pressurisation?

Answer 23

Cabin Vertical Speed >1800fpm
Switch CPCs

Cabin Altitude >8800ft
Revert to manual pressurisation

Cabin differential pressure
Adjust landing elev or go manual

Question 24

Max differential pressure before safety valves open?

Answer 24

8.6psi