PRESSURISATION: READ THE CABIN TREND
The automatic pressurisation system manages the cabin-pressure schedule as aircraft altitude changes. Cabin altitude expresses cabin pressure as an equivalent altitude; it is not expected to track aircraft altitude directly. Follow the cabin trend through climb and descent against the phase and destination setup. [69, PDF pp. 21–22]
The packs supply air, while the outflow valve and pressure controllers regulate its escape. Air conditioning and pressurisation therefore share a supply dependency but have different control objectives. A temperature selection does not command a cabin-altitude change. When a pressure indication is unexpected, inspect the pressure-control state and air supply together. [69, PDF pp. 21–22]
Read cabin altitude, cabin vertical speed and differential pressure as related indications. Their combination shows the present condition, the rate of change and the pressure difference being maintained. During climb and descent, check that the trend is consistent with the flight and that the automatic setup remains appropriate for the destination. [69, PDF pp. 17–18]
Cabin-pressure control panel, with LDG ELEV selector and AUTO/MAN mode selection. [69, PDF p. 28]
Cabin-pressure controllers, inputs and outflow-valve control. [69, PDF p. 22]
IN PRACTICE: Read pressurisation before changing anything
Before you begin: Normal automatic pressurisation preparation. The worked flight has normal-altitude airports; no high-altitude procedure is being introduced. Continue the trend-reading portion during the subsequent flight.
1. Check the automatic setup
Action. Review the CABIN PRESS controls and normal automatic selection. Check LDG ELEV AUTO, then call the ECAM PRESS page and confirm the automatic landing-elevation reference.
Check. The indication agrees with the intended automatic setup. A selector position has been confirmed on the receiving display. [69, PDF pp. 21-22] [23, PDF pp. 1014,1020]
2. Identify the three different measurements
Action. Read cabin altitude, cabin vertical speed and differential pressure on PRESS. Relate them to the current ground/flight state; a near-unpressurised ground condition should be interpreted against ambient pressure.
Check. Cabin altitude has not been confused with the aircraft’s indicated altitude, and cabin rate has not been confused with aircraft vertical speed. [69, PDF pp. 21-22]
3. Check the destination reference after initialization
Action. Once the destination is initialized, verify that the automatic landing-elevation information is consistent with the intended arrival. Revisit it after a relevant destination/arrival change.
Check. The controller’s landing reference belongs to the flight being prepared rather than an earlier destination. [69, PDF pp. 21-22] [23, PDF pp. 1082-1084]
4. Follow the trend during the flight
Action. During climb, cruise and descent, include PRESS in the system review. Compare cabin altitude, rate, differential pressure and valve indication as a group; use the applicable procedure for any abnormal state.
Check. Normal pressure control is monitored through a coherent trend. This reading exercise has not become an improvised manual-outflow-valve procedure. [69, PDF pp. 21-22] [23, PDF pp. 1074-1077] [23, PDF pp. 1085-1090]
Complete when: Automatic selection and landing-elevation reference are checked, and cabin altitude, cabin rate and differential pressure can be interpreted as distinct measurements.