A320 Pressurization MAN Mode: The Procedure Most Pilots Get Wrong

What is the A320 CAB PR SYS 1+2 FAULT procedure?

𝗖𝗔𝗕 𝗣𝗥 𝗦𝗬𝗦 𝟭+𝟮 𝗙𝗔𝗨𝗟𝗧 indicates that both Cabin Pressure Controllers have failed. The crew must select 𝗠𝗢𝗗𝗘 𝗦𝗘𝗟 𝗠𝗔𝗡, which cuts power to the AUTO motors and enables the MAN motor to control the outflow valve. The cabin must then be flown manually using the 𝗠𝗔𝗡 𝗩/𝗦 𝗖𝗧𝗟 selector. In descent, the procedural anchor is: below airfield pressure altitude + 𝟮,𝟱𝟬𝟬 𝗳𝘁, adjust 𝝙𝗣 = 𝟬. On final approach, 𝗠𝗔𝗡 𝗩/𝗦 𝗖𝗧𝗟... 𝗙𝗨𝗟𝗟 𝗨𝗣. Check that 𝝙𝗣 is zero before opening the doors. Depending on the underlying failure, the procedure may not prevent depressurization.

Source: [FCOM] §PRO-ABN-CAB_PR, p.12/14-13/14, Rev 25 NOV 24.

What does MAN V/S CTL FULL UP do on the A320?

Selecting 𝗠𝗔𝗡 𝗩/𝗦 𝗖𝗧𝗟 to 𝗙𝗨𝗟𝗟 𝗨𝗣 commands the outflow valve toward the open position. The selector is spring-loaded to neutral, so the position must be held during the input. UP increases cabin altitude (opens the valve); DN decreases cabin altitude (closes the valve). On final approach during a CAB PR SYS 1+2 FAULT procedure, holding 𝗙𝗨𝗟𝗟 𝗨𝗣 drives the valve toward fully open to ensure residual pressure bleeds off before touchdown — because in MAN mode, the automatic touchdown ground schedule is gone.

Source: [FCOM] §DSC-21-20-40, p.2/14 and p.4/14, Rev 25 FEB 25.

What are the four A320 RPCU activation conditions?

The Residual Pressure Control Unit automatically opens the outflow valve only when 𝗮𝗹𝗹 𝗳𝗼𝘂𝗿 of these conditions are met simultaneously:

The RPCU is the safety net for the version of the crew that did not execute the manual procedure in flight. It is not door-opening clearance.

Source: [FCOM] §DSC-21-20-20, p.2/2, Rev 22 MAR 16.

Can an A320 dispatch with both CPCs inoperative?

Yes, but with significant restrictions. Under 𝗠𝗘𝗟 𝟮𝟭-𝟯𝟭-𝟬𝟭𝗖, dispatch with both automatic CPCs inoperative is permitted under Category C, provided two conditions are met: the manual cabin pressure control system is operative, 𝗮𝗻𝗱 𝘁𝗵𝗲 𝗳𝗹𝗶𝗴𝗵𝘁 𝗶𝘀 𝗻𝗼𝘁 𝗽𝗿𝗲𝘀𝘀𝘂𝗿𝗶𝘇𝗲𝗱. The applicable procedure is FCOM PRO-NOR-SUP-MISC-E Flight Without Cabin Pressurization, which imposes altitude restrictions, oxygen requirements, and operational constraints. Most pilots assume both-CPC dispatch is prohibited. It is not — but it is also not a leg you brief casually.

Source: [MEL] §MI-21-31, 21-31-01C, p.2/4, Rev 18 NOV 20.

What is the A320 MEL Door Residual Differential Pressure Detection procedure?

𝗠𝗘𝗟 𝗠𝗢-𝟱𝟮-𝟭𝟬 𝟱𝟮-𝟭𝟬-𝟭𝟬𝗔 is the operational procedure that applies when the Door Residual Differential Pressure Detection equipment is itself inoperative under MEL dispatch. Before the cabin crew opens a cabin door: 𝗣𝗔𝗖𝗞 𝟭 𝗢𝗙𝗙, 𝗣𝗔𝗖𝗞 𝟮 𝗢𝗙𝗙; on the CAB PRESS SD page check 𝝙𝗣 = 𝟬.𝟬 𝗣𝗦𝗜 and outflow valve fully open; then open one cockpit sliding window. If the flight crew cannot open one cockpit sliding window, residual pressure remains and the cabin doors must not be opened.

Note: this is not the standard procedure after every CAB PR SYS 1+2 FAULT landing — that procedure only requires a 𝝙𝗣 zero check before opening doors. The full MEL sequence applies under specific MEL dispatch conditions.

Source: [MEL] §MI-52-10, 52-10-10A, p.8/8, Rev 25 FEB 25 + [MEL] §MO-52-10, p.12/14-13/14, Rev 25 FEB 25.

What does QRH OEB61 say about CAB PR EXCESS CAB ALT?

𝗤𝗥𝗛 𝗢𝗘𝗕𝟲𝟭 is unambiguous: apply the CAB PR EXCESS CAB ALT ECAM procedure even when the cabin altitude reads normal on the CAB PRESS SD page. The reason is architectural — the active CPC may be displaying an erroneous normal cabin altitude, while the standby CPC has detected the abnormal condition and triggered the alert. The standby CPC's cabin altitude is not displayed anywhere on the SD page. The warning is the only signal you get. Trust it, even when the SD page appears stable.

Source: [QRH] §OEBPROC-61, p.61.01A-61.02A, Rev 25 APR 24.

Why does the A320 outflow valve not open automatically in MAN mode?

Selecting 𝗠𝗢𝗗𝗘 𝗦𝗘𝗟 to 𝗠𝗔𝗡 cuts power to both AUTO motors that drive the outflow valve. The automatic ground schedule — cabin pressure released at 500 ft/min at touchdown, and the outflow valve fully open 55 seconds after landing — is an AUTO motor function. In MAN mode, only the MAN motor moves the valve, and only when commanded by 𝗠𝗔𝗡 𝗩/𝗦 𝗖𝗧𝗟. The crew must manually drive the valve toward open on final approach. The RPCU provides a ground backup if the manual procedure is incomplete, but only when all four activation conditions are met.

Source: [FCOM] §DSC-21-20-30, p.1/4 and p.3/4, Rev 25 NOV 24.

How long does it take to notice outflow valve changes on the A320 in MAN mode?

Two different facts apply. The procedural warning in CAB PR SYS 1+2 FAULT is explicit: in manual mode, it may take 𝟭𝟬 𝘀𝗲𝗰𝗼𝗻𝗱𝘀 before the crew notices a change in outflow valve position. The procedure tells the crew specifically to use cabin V/S to confirm valve operation. Separately, the system description notes that the visual ECAM indication of OFV position change can take up to 𝟱 𝘀𝗲𝗰𝗼𝗻𝗱𝘀.

The 10-second figure is the operational warning. The 5-second figure is a display latency note from the system description. Use cabin V/S to confirm operation. Apply short inputs. The cabin will catch up.

Source: [FCOM] §PRO-ABN-CAB_PR, p.12/14, Rev 25 NOV 24 + §DSC-21-20-30, p.3/4, Rev 25 NOV 24.

What is the A320 cabin door procedure after a pressurization failure?

The FCOM CAB PR SYS 1+2 FAULT procedure requires the crew to check that 𝝙𝗣 is zero before opening the doors. That is the standard post-fault door-opening check.

The fuller MEL procedure — 𝗠𝗘𝗟 𝗠𝗢-𝟱𝟮-𝟭𝟬 𝟱𝟮-𝟭𝟬-𝟭𝟬𝗔 (PACK 1 OFF, PACK 2 OFF, 𝝙𝗣 = 𝟬.𝟬 PSI, outflow valve fully open, sliding-window test) — applies specifically when the Door Residual Differential Pressure Detection equipment is itself inoperative under MEL dispatch. Do not conflate the two: the FCOM abnormal procedure is the standard answer; the MEL procedure applies only under specific MEL dispatch conditions.

Source: [FCOM] §PRO-ABN-CAB_PR, p.13/14, Rev 25 NOV 24 + [MEL] §MO-52-10, 52-10-10A, p.12/14-13/14, Rev 25 FEB 25.

What does MEL 21-31-01C say about A320 dispatch?

𝗠𝗘𝗟 𝟮𝟭-𝟯𝟭-𝟬𝟭𝗖 covers dispatch with both automatic CPCs inoperative. Dispatch is permitted under Category C, provided two conditions are met: the manual cabin pressure control system is operative, and the flight is not pressurized. The aircraft must be operated within the altitude restrictions in FCOM PRO-NOR-SUP-MISC-E Flight Without Cabin Pressurization.

Single-CPC failures (21-31-01A and 21-31-01B) have item-specific limits; 21-31-01A prohibits ETOPS operations. Each MEL item carries its own restrictions and must be read individually rather than generalized.

Source: [MEL] §MI-21-31, 21-31-01A/B/C, p.1/4-2/4, Rev 18 NOV 20.

How does the A320 Cabin Pressure Controller architecture work?

The A320 has two identical, independent digital Cabin Pressure Controllers (CPCs). Only one operates at a time. An automatic transfer occurs 70 seconds after each landing, or if the operating system fails. The standby CPC runs in parallel continuously — and it can detect abnormal cabin altitude and trigger an alert even when the active CPC's SD page reads normal. This is the architectural basis for QRH OEB61: the standby has not been wasting its career, and when it speaks up, it is the only honest voice in the room.

Source: [FCOM] §DSC-21-20-30, p.1/4, Rev 25 NOV 24 + §DSC-21-20-20, p.1/2, Rev 22 MAR 16.

How many motors does the A320 outflow valve have?

The outflow valve actuator contains the drives of two automatic motors and one manual motor. Either automatic motor operates the valve in automatic mode, and the manual motor operates it in manual mode. Selecting 𝗠𝗢𝗗𝗘 𝗦𝗘𝗟 to 𝗠𝗔𝗡 cuts power to the automatic motors and enables the manual motor, which is driven exclusively by the 𝗠𝗔𝗡 𝗩/𝗦 𝗖𝗧𝗟 selector. The change is binary and complete — one moment the AUTO system is flying the cabin, the next moment, you are.

Source: [FCOM] §DSC-21-20-20, Pressurization - Main Components, p.1/2, Rev 22 MAR 16.