Normal Operations

Articles 01–06 built the instrument; this article is the sheet music. Almost every bleed item in the SOPs turns out to be a timing problem — wait ten seconds for valves to settle, twenty seconds before takeoff thrust, wait for a memo before shutting down, one minute after de-icing for the engines but five for the APU. Each pause exists because some physical quantity is still in transit. The day's timeline first, then each stop on it, then the three special starts and three special environments.

 Cold aircraft → APU start → [APU AVAIL] → APU BLEED ON (check for a ground cart first!) → X-BLEED AUTO
   → engine start (APU air; variants: air-start unit / crossbleed / battery)
   → after start: APU BLEED OFF (exhaust!)   [single-engine taxi-out: X-BLEED OPEN]
   → before takeoff: packs / APU bleed per performance (20 s rule; anti-ice forbids APU bleed)
   → after takeoff: APU BLEED + MASTER OFF (if used)
   → cruise: SD round including the BLEED page
   → after landing: [OAT > 30 °C: keep slats CONF 1]   [single-engine taxi-in: X-BLEED OPEN]
   → parking: APU BLEED ON → wait for the memo → shut down immediately
   → securing: APU BLEED OFF

1. Ground and start

Switching APU bleed on — two looks before the push. The SOP action is simple (APU AVAIL → APU BLEED ON), but its explanatory note is the soul of the item. Per FCOM PRO-NOR-SOP-04:

Do not use APU BLEED, if the ground personnel confirms that a LP or HP ground air unit is connected to the aircraft. To determine if a HP ground air unit is connected, the flight crew should also check on the BLEED SD page, if there is pressure in the bleed air system.

This is article 04's limitation (APU bleed and an HP cart must never feed together) turned into technique: ask the ground crew, then interrogate the BLEED page — pressure showing with no source of your own selected means a cart is pushing. Then confirm the X-BLEED selector in AUTO. And a winter footnote that saves a maintenance write-up — per FCOM PRO-NOR-SOP-04:

Note: In cold weather conditions (below approximately 10 °C), the flight crew may observe a bleed pressure up to 12 PSI with possible fluctuations on the APU SD page and BLEED SD page.

During a normal start the bleed system is a supporting actor with one line on the checklist — Bleed pressure indication is green (FCOM PRO-NOR-SOP-08). The engine's own bleed valve sits closed throughout, courtesy of the "starting sequence" entry in the closure inventory of article 02, and cannot open until the start valve is confirmed closed (the pushbutton's fifth AND condition, article 05).

After start: APU BLEED OFF, and the reason is your nose. Per FCOM PRO-NOR-SOP-09: This action enables to avoid ingestion of engine exhaust gases. With both engines turning, the APU inlet sits in their exhaust wash; keep supplying the packs from the APU and you are pumping that wash into the cabin. The green-operations chapter concedes the fuel saving of keeping it on but repeats the smell warning — per FCTM PR-NP-SP-20, the use of APU bleed can lead to exhaust gases ingestion into the air conditioning system.

Single-engine taxi-out uses the crossbleed's legitimate-use number one: X-BLEED selector OPEN, because — per FCOM PRO-NOR-SOP-09 — Open the cross bleed valve in order to supply both packs with engine 1.

Starting the second engine during taxi — the ten-second rule. APU bleed available → APU BLEED ON, then wait. Per FCOM PRO-NOR-SOP-10:

Wait 10 s before the ENG 2 start, in order to ensure that the bleed system valves are no longer in transit. This prevents ENG 1 stall.

Pressing APU BLEED reconfigures the whole network at once — crossbleed opening, both PRVs closing (article 04). For a few seconds every valve is mid-travel and the manifold pressure is churning; add a starter's huge extraction on top and the disturbance can push engine 1's compressor toward its surge line (the FCTM lists bleed-system malfunction among engine-stall causes — article 09). Ten seconds lets the network find its feet. If APU bleed is not available, the crossbleed start of section 3 applies; either way the tail of the item restores X-BLEED AUTO and APU BLEED OFF.

2. Takeoff, cruise, arrival

Before takeoff: packs, APU bleed, and two twenty-second rules. Per FCOM PRO-NOR-SOP-11:

Consider setting the packs to OFF, or the APU bleed pb-sw to ON. This will improve performance, when using TOGA thrust. If a takeoff is performed with the packs OFF : The packs must be set to OFF at least 20 s before applying takeoff thrust.

Use of the APU bleed is not permitted, if wing anti-ice is to be used. Set the APU bleed pb-sw to ON at least 20 s before applying takeoff thrust. This will prevent the ENG THRUST LOSS alert from triggering due to incorrect valve position.

Both twenties are the same physics: FADEC computes its thrust datum from the declared bleed configuration, and configuration changes take seconds of valve travel to become true. Advance the levers early and FADEC's assumptions disagree with the plumbing — hence the nuisance alert. Set the configuration, let it settle, then push. The anti-ice prohibition is article 03's philosophy at the runway threshold: APU air arrives without the engine-bleed 200 °C guarantee, so de-icing performance cannot be assured.

The FCTM adds the interruption case every crew should pre-brief. Per FCTM PR-NP-SOP-110:

In the event of an APU auto-shutdown during takeoff, engine thrust is frozen until the thrust is manually-reduced. The packs revert to engine bleed that causes an increase of EGT, in order to maintain N1/EPR.

And the asymmetric-bleed case: with one pack unserviceable and the takeoff flown pack-on-one-side, the N1 takeoff value is limited to the value corresponding to the bleed ON configuration and takeoff performance must be computed accordingly. The LINE-UP checklist then nails the whole configuration verbally — the PACKS response is "ON", "ON supplied by APU" or "OFF" (FCTM PR-NP-CL).

After takeoff, if the APU supplied the air: APU BLEED OFF, APU MASTER SW OFF (FCOM PRO-NOR-SOP-13). Forget the first and the 25 000 ft envelope closes the valve for you (article 04); nothing closes the MASTER for you.

Cruise is one glance per round: the periodic SD review includes BLEED : BLEED parameters (FCOM PRO-NOR-SOP-15) — pressure green in the forties, temperature green near 200, valves in-line, crossbleed matching configuration, no LEAK legends (article 05).

After landing, hot day — the chapter's best-loved nuisance-alert vaccine, per FCOM PRO-NOR-SOP-21:

On ground, hot weather conditions may cause overheating to be detected around the bleed ducts in the wings, resulting in AIR L(R) WING LEAK alert. Such warnings may be avoided during transit by keeping the slats in CONF 1, when the OAT is above 30 °C.

The mechanism is article 06's closing lesson: 124 °C elements cannot tell sunshine from leaks; slats out turns the leading-edge oven into a ventilated porch.

Parking — the most precisely choreographed bleed moment of the day. Per FCOM PRO-NOR-SOP-22:

The use of the APU bleed prevents a spurious AIR ENG 1(2) BLEED NOT CLSD alert. If the APU is used: ‐ Set the APU BLEED pb-sw to ON and wait for the display of the APU BLEED memo to ensure downstream pressure for the closure of the engine bleed valve. ‐ Shut down the engines immediately after the display of the APU BLEED memo to prevent engine exhaust fumes from entering the air conditioning.

Both halves are mechanism. The PRV is pneumatically operated (article 02) — closing it takes muscle from manifold pressure. Kill the engines first and, in the seconds before APU air arrives, the valve is commanded closed with nothing to close it: the BMC sees "told to close, didn't" and files BLEED NOT CLSD (article 09). The green APU BLEED memo is the signal that APU pressure is established downstream — the baton is firmly in the next runner's hand. But from that moment the APU is supplying the cabin while two engines still idle in its inlet wash — so immediately means immediately. Wait for the memo; then don't wait at all. Securing closes the account: APU BLEED OFF (FCOM PRO-NOR-SOP-23).

3. Three special starts

The supplementary chapter opens by naming when manual/special starts should even be on your mind — after an aborted start (engine stall, EGT over-limit, low start air pressure) or when expecting one: Degraded bleed performance, due to hot conditions, or at a high-altitude airfields and Marginal performance of the external pneumatic power group (FCOM PRO-NOR-SUP-ENG). Two of the three reasons are bleed-side reasons.

Air-start-unit start (no APU bleed available). Sequence essence: PACK 1 and 2 OFF — per FCOM PRO-NOR-SUP-ENG, Packs are selected off to prevent any possible contamination of the packs by the air start unit. — APU BLEED OFF, both ENG BLEED OFF, X-BLEED OPEN (the cart feeds left of the valve, article 01). Capacity planning: Two ground air start units may be used in parallel, if the pressure/flow relation is expected to be marginal. The alert that follows the first start is expected — the AIR ABNORM BLEED CONFIG caution can be disregarded in this configuration. And the go/no-go number to watch on the BLEED page:

The minimum recommended starter air supply pressure is 25 PSI when the start valve is open.

Below 25 with the start valve open, stop cranking — you will cook a starter, not light an engine. (Engine 2 may be started first for operational reasons — check brake accumulator pressure beforehand.) After both are running: X-BLEED AUTO, bleeds ON, packs ON.

Crossbleed start (one engine feeding the other's starter). The CAUTION comes first — per FCOM PRO-NOR-SUP-ENG:

CAUTION Do not perform the crossbleed engine start procedure during pushback. Simultaneous use of engine bleed supply and external pneumatic power supply is prohibited.

The supplying engine must be run up, which is no environment for a tug crew under the tail. Configuration: APU BLEED OFF (The BLEED valve of the supplying engine reopens and the cross bleed valve closes. — resetting the stage), supplying engine's BLEED ON, receiving engine's BLEED OFF — per the procedure, The bleed valves of receiving engine are closed to avoid reverse flow leakage., which is article 02's "the PRV does not stop reverse flow" made operational — then X-BLEED OPEN (again, disregard the expected ABNORM BLEED CONFIG caution). Confirm the area behind clear, then the number pair:

Adjust thrust of supplying engine to obtain an engine bleed pressure of 30 PSI.

If the thrust required to obtain the appropriate engine bleed pressure exceeds 40 % N1, pay particular attention to the surrounding area.

Then a normal start on the receiving engine; afterwards supplying engine to idle, X-BLEED AUTO, receiving bleed ON, packs ON.

Battery-only start (air cart, no APU generator, no ground power). One sentence of electrics decides the whole sequencing. Per FCOM PRO-NOR-SUP-ENG:

Engine 1 must be started first as: ‐ The X BLEED valve does not open automatically on batteries ‐ The parking brake is pressurized by engine 1.

Article 04's bus split cashes out here: on batteries the automatic motor's normal bus is dead, the crossbleed cannot self-open, so the cart's air — trapped left of the valve — can only reach engine 1. Start the left engine first; the right one follows conventionally.

4. Three special environments

De-icing. Before spraying: both ENG BLEED OFF, APU BLEED OFF (plus the ditching-selector trick to seal the outflow paths). Two expected-alert notes keep the flight deck calm: with both engines running, setting both bleed pushbuttons OFF triggers AIR ENG 1+2 BLEED FAULT — If this occurs, disregard this alert. (FCOM PRO-NOR-SUP-ADVWXR) — and a CAUTION requires confirming the low or high-pressure ground connectors do not supply any external air. After spraying, the restoration is deliberately staggered: engines' bleeds ON at least 1 minute after completion; APU BLEED as required at least 5 minutes after. The asymmetry is inlet geography — per FCOM PRO-NOR-SUP-ADVWXR:

There is a risk of deicing fluid ingestion by the APU air intake, resulting in specific odors, or smoke warnings. Therefore: ‐ Keep the APU running with the APU bleed off for 5 min after spraying completion before setting the APU bleed to on (if required), ‐ Consider takeoff with APU bleed off.

Volcanic ash and sand. The bleed valve is managed as the cabin's intake damper. Taxi: both ENG BLEED OFF — Keep engine bleed valves closed for taxiing, especially in volcanic ash. (same disregard-the-1+2-alert note). After takeoff, clear of the cloud: ALL ENG BLEED ON. Before landing back into it: both OFF again, packs considered OFF in order to avoid contamination of the air conditioning system. Securing in an ash-contaminated port borrows the ditching pushbutton to close every outside valve overnight. Even the adverse-weather walkaround has a line for this chapter: DRAINS, BLEEDS, PROBES — CHECK FREE OF FROST, ICE AND SNOW.

High-altitude airfields. The plains trick of buying performance with packs off is banned where the cabin needs the air most — per FCOM PRO-NOR-SUP-MISC-A:

TAKEOFF WITH BOTH PACKS OFF : DO NOT PERFORM

Takeoff with both packs off may trigger the CAB PR EXCESS CAB ALT.

Field elevation is already thousands of feet; remove the inflow and the cabin altitude alert is one climb away. The sanctioned alternative keeps both goals: If required for takeoff performance, takeoff must be performed with: ‐ Both packs running supplied by APU bleed (or one pack, per the APU limitations) — engines devoted to thrust, APU devoted to the cabin.

Self-test

[!note]- Q1. Before pressing APU BLEED at the gate, what two checks — and what screen evidence betrays a connected HP cart?

Ask ground crew whether an LP/HP air unit is connected, and check the BLEED page: pressure indicated in the ducts with none of your own sources selected means a cart is supplying. APU bleed and an HP cart must never supply together.

[!note]- Q2. What are the ten seconds after APU BLEED ON actually waiting for, and whose stall do they prevent?

For the network's valves (crossbleed opening, both PRVs closing) to finish travelling so manifold pressure is stable before the starter's extraction lands on top. It protects engine 1 — the running engine — from a compressor stall.

[!note]- Q3. Two different actions each demand "at least 20 s before takeoff thrust". What is the shared mechanism, and when is APU bleed for takeoff forbidden?

Packs OFF, or APU bleed ON. FADEC's thrust datum assumes the declared bleed configuration; valves need seconds to make it true, otherwise nuisance alerts (ENG THRUST LOSS) or wrong assumptions follow. APU bleed is not permitted if wing anti-ice is to be used.

[!note]- Q4. At parking, why wait for the APU BLEED memo before shutdown — and why shut down immediately once it shows?

The engine bleed valve closes pneumatically and needs downstream pressure to do it; shutting down before APU air is established leaves the valve commanded-but-unable, triggering a spurious BLEED NOT CLSD. Once the memo confirms APU pressure, every extra second pumps engine exhaust from the idling engines into the conditioning — so stop them at once.

[!note]- Q5. Crossbleed start: recite the three defining numbers/settings and the pushback prohibition's reason.

Receiving engine's BLEED OFF (its PRV cannot block reverse flow), supplying engine's thrust adjusted for 30 PSI bleed pressure, and heightened caution behind the aircraft if that takes more than 40 % N1 — which is exactly why the procedure is banned during pushback, with ground crew under the jet wake. Engine bleed plus an external cart simultaneously is prohibited outright.

[!note]- Q6. On batteries only, why must engine 1 be started first?

The crossbleed valve's automatic motor is unpowered on batteries, so the valve cannot self-open — the air cart's supply, entering left of the valve, reaches only engine 1. (The parking brake is also pressurised by engine 1's system.)

[!note]- Q7. De-icing complete: one minute for engine bleeds, five for APU bleed. Why the asymmetry?

The APU intake sits low, in the spray environment; ingested fluid produces odours or even smoke warnings. Five minutes lets the mist settle — and if in doubt, take off with APU bleed off.

Key takeaways

References

APU bleed selection with the ground-cart interlock and cold-weather note per FCOM PRO-NOR-SOP-04; start-phase bleed indication per PRO-NOR-SOP-08; after-start APU bleed OFF and single-engine-taxi crossbleed use per PRO-NOR-SOP-09; delayed second-engine start with the 10 s rationale per PRO-NOR-SOP-10; packs/APU-bleed takeoff options, both 20 s clauses and the anti-ice prohibition per PRO-NOR-SOP-11; after-takeoff APU shutdown per PRO-NOR-SOP-13; cruise SD review per PRO-NOR-SOP-15; hot-weather slats note per PRO-NOR-SOP-21; parking APU-bleed memo sequence per PRO-NOR-SOP-22 and securing per PRO-NOR-SOP-23. Special starts (manual-start indications, air-start-unit procedure with pack-contamination note, parallel carts and the 25 PSI floor; crossbleed start CAUTION, reverse-flow rationale, 30 PSI / 40 % N1; battery start with the crossbleed-valve electrics) per FCOM PRO-NOR-SUP-ENG. De-icing bleed sequence with expected-alert notes and the 1-min/5-min staggered restoration per PRO-NOR-SUP-ADVWXR; volcanic-ash bleed management and walkaround line per the same chapter; high-altitude-airfield pack policy per PRO-NOR-SUP-MISC-A. APU-bleed performance takeoff, auto-shutdown thrust freeze and asymmetric-bleed N1 limitation per FCTM PR-NP-SOP-110; LINE-UP callouts per FCTM PR-NP-CL; green-operations exhaust note per FCTM PR-NP-SP-20. The timeline framing is an integrative synthesis of the referenced procedures.

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.