Airbus A220 Air Conditioning, Pressurisation and Oxygen
The A220 air system feeds bleed air from the engines or the APU to two air conditioning packs, with trim air, recirculation and three temperature selectors, and controls cabin pressure with a cabin pressure control system (CPCS) that has two automatic modes and a manual mode. A crew oxygen bottle and a passenger oxygen system complete it.
The Airbus A220 conditions and pressurises its cabin with bleed air. Each engine supplies it through two valves, and the auxiliary power unit (APU) and two ground connections are the alternative sources. Two air conditioning packs condition the air, a trim air system and a recirculation fan complete the distribution, and a cabin pressure control system (CPCS) with two automatic modes and a manual mode controls the cabin altitude. The MMEL ties two integrated air system controllers (IASC) to functions from bleed and pack temperature sensing to cabin altitude limiting. The flight crew breathe from an oxygen bottle, and the passengers have an oxygen system that deploys automatically or from the flight deck.
The public documents used here, the Transport Canada (TCCA) MMEL and evaluation report, the Airbus Aircraft Characteristics and Rücker and Scholz's lecture, show the components, controls and dispatch rules, not the schematics of the flight crew operating manual. Dispatch conditions quoted are the MMEL's, and an operator's own MEL may be more restrictive (see technical log, MEL and deferred defects). The principles are in air conditioning packs, bleed air and pneumatic systems and pressurisation principles and control. The Boeing 787 does without engine bleed air for its cabin (see Boeing 787 air conditioning, pressurisation and oxygen and 787 no-bleed architecture).
Bleed air sources
Each engine's bleed air passes through a high pressure shutoff valve (HPV) and a pressure regulating shutoff valve (PRSOV). A crossbleed valve (CBV) joins the left and right sides, and the crew can select it MAN CLSD. On the ground, two connections on the left side of the fuselage, on both models, accept air from ground equipment:
| Connection | Air supplied | Fitting |
|---|---|---|
| Low pressure ground connection (LPGC) | Air conditioning, 0.7 to 1.0 psig maximum | 8 in |
| High pressure ground connection (HPGC) | Bleed air, 30 to 45 psig at 170 to 232 °C | 3 in |
The engines are started with air. With the HPGC valve inoperative closed, the MMEL therefore requires the APU and its bleed to be working: without ground air, the first engine start relies on the APU (see A220 APU and fire protection).
With one engine bleed inoperative, the aircraft can be dispatched with that bleed selected OFF, its HPV and PRSOV secured closed, its ducts checked and the crossbleed valve verified working. The flight is then limited to FL 310, both avionics bay smoke detectors must work, operations follow AFM Supplement 5 (flight with systems inoperative), FLAP 4 landings are prohibited in icing conditions and steep approaches are excluded. TCCA adds a rule for the steep approach option (glide path above 3.5° up to 4.1°): with single bleed operation, such an approach is not started, or a go-around is flown, if icing conditions are forecast or present at the destination.
For the packs, the APU bleed can even replace both engine bleeds. With both engine PRSOVs secured closed, the MMEL allows the APU bleed to supply both packs throughout the flight, at or below 23,000 ft, with the passenger load limited by the AFM's APU bleed air limitations, no flight in icing and a take-off OAT of 16 °C or more.
Ground de-icing has its own sequence in the Airbus procedure. Before fluid is applied, both packs, both engine bleeds and the APU bleed are set OFF. At least 1 minute after de-icing the L, R and APU bleeds return to AUTO, and at least 3 minutes after it the APU is started, or confirmed running, and the packs return to AUTO.
Bleed air leaks are watched by leak and overheat detection loops in the pack, wing anti-ice, APU and trim air zones, and the MMEL also mentions loops on the left side of the fuselage. An inoperative APU loop makes the APU inoperative, and a trim air loop the trim air system. With the left pack zone loop inoperative, the crossbleed valve is selected MAN CLSD and the APU bleed OFF, both except for engine start, the left PRSOV and left pack are considered inoperative, wing anti-ice is selected OFF and icing conditions are avoided; the right pack zone loop has the same MAN CLSD rule.
The integrated air system controllers are two units with three channels each, IASC 1A, 1B and 1C and IASC 2A, 2B and 2C. Deactivating channel 1B also makes 1C inoperative, and 2B likewise 2C. Losing channel 2B costs the redundancy of the right bleed and right pack temperature sensors, an extraction fan (EFAN) and the backup cabin altitude limiter; losing 1B costs the left-side equivalents and the primary altitude limiter.
Packs and temperature control
Each of the two packs has its own flow control valve (FCV); with its FCV secured closed, a pack delivers no air, so dispatch with one FCV inoperative, except for extended operations, treats that pack as inoperative. With one pack inoperative the MMEL limits the flight to FL 310 and excludes steep approaches, under AFM Supplement 5, as it does for one engine bleed. Neither case prohibits flight in icing conditions, although the bleed case prohibits FLAP 4 landings in them.
With a ram air regulating valve (RARV) secured open, its pack runs in a degraded mode, and operations with an OAT between ISA and ISA minus 30 °C inclusive, on the ground and in flight, are prohibited. With the emergency ram air valve (ERAV) inoperative and secured open, the right pack is considered inoperative, or the flight is made unpressurised with crew only and both packs considered inoperative; either way, extended overwater operations and take-offs and landings on runways near water are excluded.
The AIR control panel carries the RAM AIR, PACK FLOW and RECIRC AIR pushbuttons. Temperature is selected with three knobs, for the cockpit, the FWD CABIN and the AFT CABIN. The trim air system has one trim air pressure regulating valve (TAPRV) and one trim air shutoff valve (TASOV); with the TAPRV secured closed, the MMEL warns that duct temperatures may fluctuate rapidly, as seen on the AIR synoptic page, and that warmer air may be expected in the affected zones.
L PACK FAIL, R PACK OVHT and L BLEED FAIL are cautions, while PACK FAULT is only an advisory. The equipment bays are ventilated too: two avionics bay exhaust valves (AEV) serve the forward and the mid avionics bays.
Recirculation and cargo ventilation
A single recirculation fan (RFAN) returns cabin air to the distribution. If it fails, RECIRC AIR is selected OFF, its check valve is verified and both packs must work, since all the cabin air then comes from the packs.
The cargo compartments have cargo shutoff valves (CSOV), two forward and two aft. With both forward valves secured closed the FWD CARGO selector is set OFF, and with both aft ones closed the AFT CARGO air switch is set OFF. The FWD CARGO selector also offers VENT, LO HEAT and HI HEAT. After a FWD CARGO LO TEMP or FWD CARGO HEAT FAIL caution, the forward heating cannot be relied on: for dispatch the selector is set to OFF or VENT, and no live animals or temperature-sensitive cargo travel in the forward hold.
Dry ice gives off carbon dioxide, and the Airbus Aircraft Characteristics base their dry ice calculation on keeping CO2 in the cabin below 0.5 % with a single pack running. The aircraft must nevertheless be dispatched with two packs; losing one in flight does not require a diversion. Pack-off take-offs are avoided, and FWD CARGO VENT must not be OFF with dry ice in the forward hold.
Pressurisation control
The CPCS has two automatic modes, which give it redundancy, and a manual mode, selected with the AUTO PRESS pushbutton; the pushbutton has MAN and FAIL lights, and its MAN light shows manual control. The MMEL lists an automatic selection, a manual selection and an indication of the landing field elevation (LFE), and a cabin rate of climb indication. A primary and a backup cabin altitude limiter are lost with IASC channels 1B and 2B respectively. The MMEL also lists two large and two small pressure equalisation valves (PEV); on other types such valves let the cargo holds follow the cabin pressure (see pressurisation safety valves and warnings).
In a typical pressurised aircraft the controller sets the cabin altitude by positioning an outflow valve, which meters how fast air leaves the fuselage. What stands out is the cabin altitude. Rücker and Scholz give the A220-300 a usual cabin altitude below 6,000 ft, against 6,000 to 8,000 ft for the A320neo and the Boeing 737-800, and a 6,000 ft cabin even at FL410, its maximum cruise level; the maximum operating altitude in the type certificate is 41,000 ft. They attribute this to the large differential pressure that aluminium-lithium in the fuselage allows, and note that the A220-300 also has a humidifier.
Abnormal pressurisation
The MMEL places three pushbuttons on the PRESSURIZATION panel: EMER DEPRESS with an ON light, AUTO PRESS with its MAN and FAIL lights, and DITCHING with an ON light. The sources used here do not describe what EMER DEPRESS and DITCHING command. On other types a ditching control closes the valves and openings below the flotation line, and an emergency depressurisation or dump function lets the cabin climb on purpose, for example to clear smoke. Ditching is an approved operation in the A220's type certificate.
When the MMEL relies on manual pressurisation, after AUTO PRESS FAIL or with the LFE indication or manual LFE selection inoperative, it requires the autopilot to be working and limits operations to airports with an LFE of 8,000 ft or less. With AUTO PRESS FAIL, the minimum enroute altitude must also not exceed 10,000 ft. Emergency descent is covered in A220 flight deck and avionics.
Exam tip: manual pressurisation for dispatch means autopilot working and a landing field elevation of 8,000 ft or less. The 10,000 ft figure that comes with AUTO PRESS FAIL is a limit on the minimum enroute altitude, not on the LFE.
Crew oxygen
The flight crew oxygen system has a capacity of 77 ft³ (2,180 L) at a nominal working pressure of 1,850 psig (128 bar), on both models; the E190-E2's crew cylinder is of the same size and nominal pressure (see E-Jet fire protection and oxygen). It is serviced through access door 115CL, 3.11 m (10.20 ft) aft of the nose, 0.79 m (2.60 ft) left of the centreline and 1.96 m (6.44 ft) above the ground. There the Airbus figure shows the crew oxygen fill valve, a pressure gauge and an overboard discharge indicator, a disc in MMEL terms.
The oxygen pressure is shown in three places: the ground service panel indicator, the bottle pressure gauge and the EICAS oxygen pressure indication. Any one of them may be inoperative for dispatch if another works and is checked before each flight. An oxygen pressure switch triggers the CREW OXY LO PRESS caution. If the switch fails without the caution showing, the bottle control valve is verified open and the bottle pressure checked before each flight. The principles are in crew oxygen systems.
Passenger oxygen
The passenger oxygen system has an automatic deployment function and an alternate deployment from the flight deck, and the overhead PAX OXY pushbutton has a DPLY light. The sources used here do not say how the passenger oxygen is produced or for how long it lasts; the general arrangements are in passenger and portable oxygen.
| Failure (TCCA MMEL) | Dispatch conditions |
|---|---|
| Automatic deployment inoperative | Alternate deployment from the flight deck working; flight at or below FL 300 |
| Passenger cabin oxygen system inoperative | Pressurised flight at or below 10,000 ft; or at or below FL 250 with a minimum enroute altitude of 13,000 ft or less, both packs and pressurisation working, portable oxygen for all crew members and 10 % of the passengers for half an hour, and passengers briefed |
Exam tip: automatic mask deployment lost: FL 300. Whole passenger oxygen system lost: 10,000 ft pressurised, or FL 250 with a minimum enroute altitude of 13,000 ft or less.
Wing and engine cowl anti-ice, window heat and the wipers are covered in A220 ice and rain protection, and the A220's dimensions and limitations in A220 family and limitations.
Frequently asked questions
Where does the cabin air of the Airbus A220 come from?
From bleed air. Each engine supplies it through a high pressure shutoff valve (HPV) and a pressure regulating shutoff valve (PRSOV), the APU can supply it as well, and on the ground a high pressure connection takes 30 to 45 psig bleed air. Two air conditioning packs, each with its own flow control valve, condition the air. The Boeing 787, by contrast, does not use engine bleed air for its cabin.
What cabin altitude does the A220 keep?
Rücker and Scholz, comparing the A220-300 with the A320neo and the Boeing 737-800, give it a usual cabin altitude below 6,000 ft, against 6,000 to 8,000 ft, and a cabin altitude of 6,000 ft even at FL410, its maximum cruise level. They attribute this to the large differential pressure that aluminium-lithium in the fuselage allows. The A220-300 also has a humidifier, which the other two lack.
How is pressurisation controlled on the A220?
By a cabin pressure control system (CPCS) with two automatic modes and a manual mode, selected with the AUTO PRESS pushbutton, which has MAN and FAIL lights and sits on the PRESSURIZATION panel with EMER DEPRESS and DITCHING. The MMEL also lists a primary and a backup cabin altitude limiter. Dispatch with pressurisation in manual mode requires a working autopilot and a landing field elevation of 8,000 ft or less.
How much oxygen does the A220 crew oxygen system hold?
The Airbus Aircraft Characteristics give a capacity of 77 cubic feet (2,180 litres) at a nominal working pressure of 1,850 psig (128 bar), on both models. The system is serviced through access door 115CL on the left side, about 3.1 m aft of the nose, where a fill valve, a pressure gauge and an overboard discharge indicator are found. An oxygen pressure switch triggers the CREW OXY LO PRESS caution.
How do the A220 passenger oxygen masks deploy?
The passenger oxygen system has an automatic deployment function and an alternate deployment from the flight deck, and the overhead PAX OXY pushbutton has a DPLY light. With automatic deployment inoperative, the MMEL requires the alternate system to work and limits flight to FL 300. With the whole system inoperative, passengers may be carried only pressurised at or below 10,000 ft, or at or below FL 250 with a minimum enroute altitude not above 13,000 ft and further conditions.
Test yourself on Airbus A220 Air Conditioning, Pressurisation and Oxygen
The v1prep banks cover this topic in the A220 type-rating bank, with a worked explanation for every answer. EASA ATPL, PPL, IR and CPL, the FAA written tests and type ratings for the A320, 737, A220, 787, ATR 72 and E-Jet.
Start practising →Sources and further reading
- Transport Canada, Master Minimum Equipment List BD-500 (A220-100/-300), Issue 015
- Airbus, A220 Aircraft Characteristics Publication (ACP), BD500-3AB48-13800-00
- Transport Canada, Operational Evaluation Report BD-500 (A220-100 and A220-300), Revision 3
- EASA Type-Certificate Data Sheet EASA.IM.A.570, BD-500 (A220-100 and A220-300), Issue 25
- J. Rücker and D. Scholz, Highlights of the Airbus A220 from a Pilot's Perspective, HAW Hamburg, 2024
Library articles are written for study and exam preparation. They do not replace your aircraft's approved documentation, your operator's procedures or the regulations themselves.