Pressurisation Flashcards
What components make up the pressurisation system, and how does it function?
Two CPC
One RPCU
One outflow valve (actuator with 3 motors, 2 auto, 1 manual)
One cockpit control panel
Two Safety Valves
One CPC functions at a time, switch at the end of a complete press. cycle, 70 secs after landing.
Cabin Alt (press) is controlled by varying position of outflow valve to store/release pressure of air in cabin from ac sys.
One cycle has 4 modes:
Ground Function
Pre-pressurisation
Pressurisation
Depressurisation
What is Pre-pressursation mode?
Active during takeoff roll, to avoid pressure surge at rotation, controller pre-pressurises a/c at a rate of 400ft/min, until deltaP is 0.1PSI.
When does in-flight pressurisation mode become active, and how does it function during climb, cruise and descent?
CLB - activates at lift-off. Cabin alt varies according to a fixed pre-programmed law that takes into account a/c actual ROC.
CRUISE - CPC maintains cabin alt at level-off value, or at landing field elevation if higher. Cab alt target is limited to approx 8000ft.
DESCENT - CPC maintains a cain ROD such that cabin pressure = ldg field pressure + 0.1PSI shortly before ldg.
Max cabin ROD is 750ft/min
When do depressurisation and ground modes activate and what happens in automatic mode?
Depressurisation mode occurs at touch down which releases any cabin overpressure.
Ground mode occurs 55secs after landing, outflow valve motors fully open.
What is the maximum cabin altitude in automatic mode?
8000ft
What does the pressurisation sys use in automatic mode as a reference for LDG elevation.
Dest QNH from APPR page and A/D elevation from FMGC.
How is Manual pressurisation control achieved, and how does it work?
Achieved using the MAN override pb on overhead panel. This cuts power to two auto outflow valve motors and energises 3rd manual mode motor.
Manual control achieved through dedicated part of CPC1 which remains available even with dual CPC failure.
Cabin alt controlled using CABIN V/S toggle switch to adjust position of OUTFLOW valve. Pressurisation schedule on ECAM or in FCOM abnormal.
What Press sys proc are there in the QRH, and when should you action it?
Cabin Overpressure - Initiate as soon as becomes obvious we have lost control of press sys leading to overpressure as we have lost control of outflow valve.
Proc calls to switch PACKS OFF, BLOWER & EXTRACT to OVRD to vent cabin air overboard. Monitor cabin press and use PACKS ON/OFF to control.
What are the pressurisation sys advisories in QRH, and what are recommended crew actions?
CABIN VERTICAL SPEED >1800ft/min
CPC changeover recommended, MODE SEL: MAN, 10 secs then back to AUTO. If unsuccessful, MODE SEL: MAN, manual pressure control.
CABIN ALTITUDE >8800ft
CPC changeover recommended. As above.
DeltaP >/= 1.5PSI in phase 7
LDG ELEV: ADJUST. If unsuccessful, MODE SEL: MAN, manual pressure control.
