ECAM CAB PRESS Page & the ATA 21 Warning Matrix

This article completes the indication picture: the CAB PRESS page fields, plus the whole ATA 21 warning matrix — the warnings, their levels (L1/L2/L3), and the flight-phase inhibition. The BLEED + COND pages are ata-21-19.

1. CAB PRESS page — eight fields

2. LDG ELEV AUTO/MAN & landing elevation

The LDG ELEV indication is always white. AUTO: appears in green when the LDG ELEV selector is in AUTO. Becomes amber if the landing elevation is not transmitted by the FMGES. MAN: appears in green when the LDG ELEV selector is not in AUTO. Neither appear when the MODE SEL pb-sw is in MAN and the VALVE SEL selector is in BOTH, or when the LDG ELEV selector is faulty. Landing elevation selected either automatically by the FMGES or manually by the pilot appears in green. — FCOM DSC-21-20-40

3. Cabin V/S & ΔP

V/S FT/MIN (cabin vertical speed). The analog and digital presentation appear in green when V/S is in the normal range. The digital indication pulses, when the V/S is more than 1 800 ft/min in either climb or descent. ΔP PSI. The analog and digital presentations appear in green when ΔP is the normal range. They appear in amber when ΔP ≤ -0.2 PSI or ≥ 8.85 PSI. The digital presentation pulses if ΔP > 1.5 PSI (resets at 1 PSI) during flight phase 7. — FCOM DSC-21-20-40

[!note]- A pulsing 1800 ft/min cabin V/S is a warning, not a visual emphasis

Normal cruise cabin V/S is ≤ 1000 ft/min (climb); descent is ≤ ~1800 ft/min. > 1800 ft/min = an abnormal pressurisation profile or an emergency descent → the digit pulses. Check the aircraft V/S + the CPC state (if descending hard, it is expected).

[!warning]- The ΔP amber thresholds (−0.2 / +8.85 PSI) are close to but distinct from the safety-valve triggers

The ECAM ΔP field goes amber at −0.2 PSI (visual) — the safety valve admits air at −0.261 PSI (mechanical), so the crew sees the ECAM caution ~0.06 PSI before the valve acts. Likewise +8.85 PSI (ECAM) vs +8.847 PSI (the valve relief) — the FCOM digital layer vs the AMM physical layer. The flight-phase-7 (final approach) pulse above 1.5 PSI warns that the cabin still has too much pressure near landing.

4. CAB ALT — the 9550 ft red

CAB ALT FT (cabin altitude). The analog and digital presentations appear in green, in normal range. They appear in red if the cabin altitude goes above 9 550 ft. — FCOM DSC-21-20-40

[!warning]- Cabin altitude > 9550 ft is red — the only red ATA 21 field

Most ATA 21 warnings are amber (caution). Cabin altitude > 9550 ft is red (warning) — the highest level. It triggers together: the red ECAM field, the E/WD EXCESS CAB ALT red warning, the red MASTER WARN + continuous repetitive chime (level 3), and ATA 35 automatically dropping the passenger masks + signs (ata-21-17). Crew action: don masks + emergency descent (ata-21-24).

The other fields: outflow-valve position (0–100°, RVT feedback; in manual mode from the CPC #1 backup potentiometer); the safety-valve symbol (open/closed from the position switch; open + amber = CAB PR SAFETY VALVE OPEN, ata-21-13); and pack flow + cabin temperature (as the COND page).

5. CRUISE page — cabin V/S

CAB V/S FT/MN. In AUTO PRESS mode: Absolute value of cabin vertical speed is normally green. It pulses green above 1 800 ft/min or below – 1 800 ft/min. ▲: displayed green when the cabin vertical speed is between 25 and 1 800 ft/min ... ▼: displayed green when the cabin vertical speed is between -1 800 and -25 ft/min ... nothing is displayed when the cabin vertical speed is between -25 and +25 ft/min. — FCOM DSC-21-20-40

[!note]- The CRUISE page shows cabin V/S as an absolute value + an arrow, not a signed number

The CAB PRESS page shows the signed digit directly; the CRUISE page (the default cruise display) shows the absolute value + an up/down arrow (AUTO mode), simplifying for at-a-glance reading. The ±25 ft/min dead band (no arrow) means the cabin is near stable.

6. The ATA 21 warning matrix

7. Warning levels L1 / L2 / L3

   L1 — Memo:    no sound, no MASTER light; E/WD green memo. ATA 21 has none.
   L2 — Caution: single chime + amber MASTER CAUT; E/WD amber + procedure. Most ATA 21 warnings.
   L3 — Warning: continuous repetitive chime (CRC) + red MASTER WARN; E/WD red.
                 ATA 21: EXCESS CAB ALT, SMOKE/FUMES, AVNCS SMOKE, CARGO SMOKE.

[!warning]- ATA 21's four L3 warnings all involve a direct threat to life

EXCESS CAB ALT (hypoxia), SMOKE/FUMES (asphyxiation), AVNCS SMOKE (loss of aircraft capability), CARGO SMOKE (fire spread). Most other ATA 21 warnings (PACK FAULT/OVHT, HOT AIR FAULT, zone-controller failure) are L2 cautions — serious but not immediately lethal. A continuous repetitive chime + a red MASTER WARN → act at once, no delay.

8. Flight-phase inhibition

Some ATA 21 warnings are inhibited in critical flight phases to avoid distraction:

L3 warnings are never inhibited — EXCESS CAB ALT / SMOKE always sound.

[!note]- PACK FAULT does not warn above 80 kt on the takeoff roll — continuing would distract

Above 80 kt + lift-off + initial climb is inside the decision window, where the pilot must focus on aircraft control. Even if a pack fails then, it is not immediately lethal (the cabin still has air + an L2 caution) → it can wait until the climb is stable. L3 warnings (EXCESS CAB ALT / SMOKE) are not inhibited — immediately lethal warnings must sound. A pack failure on the takeoff roll → after lift-off + initial climb → past the inhibition window → the ECAM shows it → the pilot handles it. The ECAM's "silence" in critical phases is intentional.

Self-test

[!note]- Q1. What do the ΔP amber thresholds (−0.2 / +8.85 PSI) mean, and their relation to the safety valve?

−0.2 PSI amber = negative-pressure caution (cabin 0.2 PSI below ambient) — close to but distinct from the safety valve's −0.261 PSI admit. +8.85 PSI amber = overpressure caution — almost identical to the valve's +8.847 PSI relief. The relation: the ECAM field threshold (visual) vs the safety-valve trigger (mechanical) — the same philosophy as the compressor-outlet three thresholds. An amber ΔP → near the mechanical protection → the safety valve may be about to act.

[!note]- Q2. Why is cabin altitude > 9550 ft red, and what triggers together?

Red = L3 warning (a direct threat to life). Most ATA 21 warnings are amber L2; > 9550 ft is direct hypoxia → L3 red. Five things trigger: the red ECAM field, the red E/WD EXCESS CAB ALT, the red MASTER WARN, the continuous repetitive chime, and ATA 35 dropping the masks + signs (no crew action). ATA 21's four L3 warnings all relate to life: EXCESS CAB ALT / SMOKE-FUMES / AVNCS SMOKE / CARGO SMOKE. Crew: hear the CRC + see the red MASTER WARN → act at once (masks + emergency descent).

[!note]- Q3. Is a pulsing 1800 ft/min cabin V/S a warning or normal?

An abnormal-state warning (not a visual emphasis). Normal cruise cabin V/S is ≤ 1000 ft/min (climb), descent ≤ ~1800 ft/min; > 1800 ft/min = an abnormal pressurisation profile or an emergency descent. Shown as a pulsing digit (CAB PRESS) / a pulsing absolute value + arrow (CRUISE). Check the aircraft V/S + the CPC state (if in an emergency descent, it is expected).

[!note]- Q4. What are the four LDG ELEV "AUTO/MAN" states, and what does AUTO amber mean?

AUTO green = the selector in AUTO + FMGES OK (normal automatic); AUTO amber = in AUTO but the FMGES does not transmit the elevation (FMGES failure); MAN green = the selector pulled out + set by hand (semi-automatic); neither shown = MODE SEL MAN + VALVE SEL BOTH, or the selector faulty. For AUTO amber: pull the selector past the mechanical stop and set the field elevation (−2000…14,000 ft) → semi-automatic → the display changes to MAN green.

[!note]- Q5. What sounds/lights distinguish L1/L2/L3, which ATA 21 warnings are L3, and why flight-phase inhibition?

L1 Memo: no sound, no MASTER light, green E/WD memo (ATA 21 has none). L2 Caution: single chime + amber MASTER CAUT (most ATA 21 warnings). L3 Warning: continuous repetitive chime + red MASTER WARN. The four L3: EXCESS CAB ALT / SMOKE-FUMES / AVNCS SMOKE / CARGO SMOKE (all life-threatening). Flight-phase inhibition: in critical phases (takeoff roll above 80 kt / touchdown / landing roll) the pilot must focus — L2 cautions would distract; L3 are never inhibited. A pack failure on the takeoff roll → not lethal → shown after the climb is stable.

Key takeaways

Common misconceptions

Scope — what this article covers and defers

References

A330 specifics per FCOM DSC-21-20-40 (the CAB PRESS page fields — the four-state LDG ELEV AUTO/MAN, the landing elevation, the cabin V/S with its 1800 ft/min pulse, the ΔP with its −0.2/+8.85 PSI amber and its flight-phase-7 1.5 PSI pulse, the cabin altitude with its 9550 ft red, the outflow-valve position, the safety-valve symbol, and the pack flow + cabin temperature; and the CRUISE-page cabin V/S in AUTO/MAN PRESS modes) plus AMM 21-31-00 §7.D for the failure indications. The ATA 21 warning matrix and its L1/L2/L3 levels, the flight-phase-inhibition rationale, the "four L3 = life-threatening" grouping, and the ECAM-vs-mechanical-threshold comparison are integrative syntheses drawing each warning from its stage-A/B/C/D chapter. All engineering detail is from the A330 knowledge base; no cross-type comparison is made, and no fleet tail numbers appear.

Independent study material, not an Airbus publication and not endorsed by the manufacturer. Always defer to the current operator FCOM, FCTM, and QRH for operational use.