Abnormal I: The Leak Family

Article 06 explained how the loops detect; this one is about the day they fire. Six leak-family alerts plus the wrap-up procedure they all funnel into — AIR ABNORM BLEED CONFIG with the crossbleed closed. One doctrine governs everything here, and it is worth stating before the first alert: by the time you read a leak alert, the system has already isolated. Your actions confirm and complete; they do not rescue. The pushbutton-OFF you perform converts a latched automatic closure into a deliberate crew configuration — and there is never, anywhere in this family, an attempt to switch anything back on. Leaks are physical; physics does not reset (article 09 shows the contrast).

The family tree:

1. AIR L(R) WING LEAK — the family's standard portrait

Trigger, per FCOM PRO-ABN-AIR:

The AIR L(R) WING LEAK alert triggers when both wing bleed leak detection loops detect a temperature above 124 °C.

("Both loops" carries article 06's full AND semantics — two votes, or one vote plus a dead loop.) The procedure's action line is a single item — ENG BLEED (AFFECTED SIDE) OFF — and its most instructive content is the light logic beneath it:

When the ENG BLEED pb-sw is ON, the FAULT light remains on. When the ENG BLEED pb-sw is OFF, the FAULT light goes off when the overheat disappears.

The FAULT light answers to the hot spot, not to your finger. Press OFF and the light may well stay on for a while — it extinguishes when the leak site cools, which makes it the physical confirmation that isolation worked. Run the logic backwards and it becomes a monitoring tool: bleed OFF, minutes pass, light still burning → something is still feeding the leak → your eyes go to the crossbleed and APU symbols. (The eutectic salt refreezing is the mechanism — article 06.)

For a left wing leak the procedure adds: APU BLEED — OFF. The geography lesson again — the APU's delivery corridor is the left half, so a left-wing fire sits on its supply route; the automatics have already closed the APU valve (article 06's matrix) and your selection makes it configuration. A right-wing leak has no such line: closing the crossbleed walls it off. The procedure then refers to AIR ABNORM BLEED CONFIG (X BLEED Closed) — section 4.

2. Pylon and APU variants — same skeleton, different jackets

AIR ENG 1(2) BLEED LEAK (the pylon alert). Trigger, per FCOM PRO-ABN-AIR:

The AIR ENG 1(2) BLEED LEAK alert triggers when the pylon bleed leak detection loop detects a temperature above 204 °C and engine 1(2) is running.

Two differences from the wing version, both traceable to article 06: a single loop suffices (pylons have only one), and the engine running condition — a stopped engine's pylon can only be residually or externally hot, which is not a leak. Actions mirror the wing: affected side's ENG BLEED OFF, same two-state light logic, engine 1 case adds APU BLEED OFF (pylon 1 is on the APU corridor), and the same referral to X BLEED Closed. Inoperative-systems accounting: the affected engine bleed, plus APU BLEED when it is the number-1 side.

AIR APU BLEED LEAK — a one-alert, two-act play. Trigger:

This alert triggers when both APU bleed leak detection loops detect a temperature above 124 °C.

Act one is routine: APU BLEED — OFF (the valve has already auto-closed — remember from article 06 that the APU loop enjoys no engine-start exemption; its own supply line burning is the one case where the start loses). Same hot-spot light logic. Act two is the conditional that makes this alert famous:

If the APU line leak is fed by an engine bleed:

…the sub-legend APU LEAK FED BY ENG appears, and the action is ENG 1 BLEED — OFF. The deduction chain was built in article 06: valve closed yet the duct is hot → the flow is arriving backwards through a failed-open APU check valve → the feeder is the left half's supplier → cut engine 1. ECAM has done the detective work; the sub-legend is the verdict, your hand executes the sentence. The system-level sequence and the STATUS entry (INOP SYS: APU LEAK) follow the AMM's account of the leak shutdown cascade. Dispatch treats the culprit check valve with notable severity — removal-and-blank or a before-every-flight check (article 11).

3. AIR BLEED LEAK and the two DET FAULTs — the special constables

AIR BLEED LEAK — the alert that exists because of a courtesy. Trigger, per FCOM PRO-ABN-AIR:

This alert triggers when a leak is detected in a bleed duct and the X-BLEED selector is set to OPEN.

Recall the exemption threaded through article 06's matrix: the crossbleed's automatic closure defers to a manually selected open valve — the automation respects your selector (article 04's "manual prevails"). But with the valve locked open, the leak is drinking from both halves of the network. So a dedicated alert exists whose entire action list is one line — X BLEED: CLOSE — the system saying: the valve I am not allowed to close, you now must. Politeness, with a supervisor attached. One inhibition window: Alert inhibited during the first 15 s of the flight phase 5 — the takeoff-roll thermal transient is not allowed to interrupt a takeoff decision.

The two DET FAULT alerts — nerves gone blind, per FCOM PRO-ABN-AIR: This alert triggers when both APU bleed leak detection loops are inoperative. and This alert triggers when both wing bleed leak detection loops are inoperative in one wing. In-flight action for both: crew awareness, nothing more — the detector is broken, nothing is leaking. The asymmetry arrives on the ground, and it is stark: some operators' MELs make a wing-loop DET FAULT a no-dispatch item while offering the APU loop several conditional paths. The logic (developed in article 11): a blind wing loop leaves the anti-ice ducting with no monitoring at all and no way to render it cold, whereas the APU duct can be made cold — don't use APU bleed, deal with the check valve — and a cold pipe needs no nerves. Note also from article 06: a single loop failure produces no alert at all, just a maintenance-level status entry; DET FAULT means the pair is gone.

4. The wrap-up: AIR ABNORM BLEED CONFIG (X BLEED CLOSED)

Every leak alert refers here. Trigger, per FCOM PRO-ABN-AIR:

This alert triggers when at least one engine bleed fails, is OFF, or is not supplied.

The spine: if a bleed is abnormally selected off, confirm ENG 1(2) BLEED OFF; if the bleed is not recovered, X BLEED — CLOSE. And the five-condition test that decides CLOSED (the mirror of article 09's OPEN test):

CLOSE, if: ‐ LEAK, or ‐ ENG FIRE (detected, or FIRE pushbutton pressed), or ‐ Engine start valve failed open, or ‐ Overpressure with the bleed valve failed open, or ‐ Overtemperature with the bleed valve failed open.

Five conditions, one common property: the sickness is contagious through the crossbleed. A leak drinks the other side's air; a fire inhales it; a failed-open start valve dumps it into a dead engine; runaway pressure or temperature exports itself into the healthy half. The whole crossbleed decision, compressed: contagious — close the door; not contagious — open it and share (the OPEN half lives in article 09). Note the connective grammar for later: CLOSE's conditions are joined by or — any one suffices; OPEN's five are joined by and — all must be clear. Borrowing air is audited more strictly than refusing it.

The overtemperature-with-valve-stuck-open case brings extra lines — PACK (AFFECTED SIDE) OFF, WING A.ICE OFF, AVOID ICING CONDITIONS, and under severe ice accretion a speed floor of VLS +10 / G DOT with MANEUVER WITH CARE (the STATUS page repeats it with the note that the speed must not drop below G DOT clean or VLS +10 kt in other configurations, plus an approach block: FLAP LVR 3 for landing, APPR SPD VLS +10 KT, LDG DIST PROC APPLY). Uncloseable hot air is still flooding toward the users, so the users get bricked up.

And the procedure's most exam-dense sentence:

Note: APU BLEED pb-sw must not be used for wing anti-ice purpose, or after ENG 1 FIRE.

Two prohibitions, two articles' worth of reasoning in one line. First half: APU air carries no 200 °C guarantee (article 04 — unregulated by design), so de-icing performance cannot be assured — the same reason APU-bleed takeoffs and anti-ice don't mix (article 07). Second half is pure geography: after an engine-1 fire the left half of the network is treated as a suspected fire zone, and the APU's delivery path runs straight through it — pumping air toward a fire feeds it.

The inoperative-systems bill for the closed-crossbleed configuration: WING A. ICE, the affected ENG BLEED, the affected PACK, and forward-cargo temperature control where fitted.

5. Discipline: how the hands and mouth work

The FCTM's overhead-panel protocol was written for exactly these procedures. Per FCTM AOP-30-30:

To perform any action requested by a procedure, the PM should indicate the related panel and control and announce in sequence: ‐ The name of the system ‐ The name of the control, or system reset ‐ The action.

The FCTM's own worked example is, fittingly, from this chapter: "AIR, XBLEED, CLOSE". Two companion habits from the same section: the amber FAULT light usually marks the correct control (the tier-4 design of article 05 — the light points your hand), and after the selection the PM checks the SD page to confirm the action took effect — for the leak family, crossbleed symbol closed, both affected valves closed, and in due course the FAULT light dying with the hot spot.

One further sensory channel belongs in this article: smoke and odours travel the bleed system. The FCTM smoke guidance notes that after an engine or APU failure, fumes can enter through the bleed system and recirculate until purged, and its odour table pins two entries on this chapter — a chemical smell against contaminated bleed ducts, and the notorious dirty socks against engine or APU oil leaks. A cabin call about odd smells is sometimes the first leak-family indication of all.

6. A worked scenario

Cruise, FL380. ECAM: AIR L WING LEAK.

1. Already done by the system (article 06's matrix): ENG 1 bleed and HP valves closed; crossbleed auto-closed (selector was in AUTO); APU valve closed had it been open; ENG BLEED 1 FAULT burning amber; BLEED page self-displayed with the LEAK legend on the left wing.
2. Crew: ECAM — ENG 1 BLEED pushbutton OFF ("AIR, ENG 1 BLEED, OFF"); APU BLEED OFF if in use; into ABNORM BLEED CONFIG — LEAK is the first of the five CLOSE conditions, the valve is already shut, and nobody selects OPEN.
3. Confirm: BLEED page — crossbleed closed, left pair closed; over the next minutes the FAULT light should extinguish as the bay cools. If it does not, ask the only question that matters: who is still feeding the left wing?
4. Live with it (STATUS): left bleed inoperative; wing anti-ice unavailable — with a leak, the crossbleed stays CLOSED, so there is no legal way to feed both wings — AVOID ICING; PACK 1 starved, PACK 2 carries the cabin.
5. On the ground (article 11): WING LEAK is a no-dispatch item. The aeroplane stays.

Self-test

[!note]- Q1. State the three main leak triggers with their numbers and loop counts.

Wing: both loops above 124 °C (AND logic, dead-loop vote transfer applies). Pylon: the single pylon loop above 204 °C with the engine running. APU: both APU loops above 124 °C.

[!note]- Q2. Where does "left-side events also switch off the APU bleed" appear in this family, and why never for right-side events?

In the L WING LEAK procedure and the ENG 1 BLEED LEAK (pylon 1) procedure. The APU delivery corridor is the left half of the network; right-side leaks are fully walled off by the closed crossbleed.

[!note]- Q3. Reconstruct the FED BY ENG chain and its one crew action.

APU loops alarm with the APU valve closed → heat must be arriving backwards from the crossbleed duct → the APU check valve has failed open → the feeder is the left half's supplier → ENG 1 BLEED OFF.

[!note]- Q4. Why does AIR BLEED LEAK exist at all, and why is it inhibited for 15 s at the start of takeoff?

Because the crossbleed's automatic leak-closure defers to a manually selected OPEN — the alert is the safety net that tells the crew to close by hand the valve the automation respects. The 15 s inhibition stops the takeoff-thrust thermal transient from generating a distraction during the takeoff decision.

[!note]- Q5. FAULT light two-state logic: what does the light actually track, and how do you use it after isolating?

The hot spot. Pushbutton ON: light stays on regardless. Pushbutton OFF: light extinguishes only when the overheat disappears. After isolation it becomes the confirmation channel — a light that will not die means something is still feeding the leak; check crossbleed and APU symbols.

[!note]- Q6. Recite the five CLOSE conditions and the one property they share, and contrast the connective with OPEN's.

Leak; engine fire (detected or pushbutton); start valve failed open; overpressure with the bleed valve failed open; overtemperature with the bleed valve failed open — each exports its sickness through an open crossbleed. CLOSE is an OR-list (one suffices); OPEN is an AND-list (all five must be absent).

[!note]- Q7. Both halves of the APU BLEED anti-ice note — mechanisms?

Not for wing anti-ice: APU air is unregulated and carries no 200 °C guarantee, so de-icing effectiveness is unassured. Not after ENG 1 FIRE: the left network is a suspected fire zone and the APU's delivery path crosses it — supplying air would feed the fire.

Key takeaways

References

Alert triggers, action lines, FAULT-light two-state logic, the FED BY ENG conditional, the 15 s phase-5 inhibition, DET FAULT definitions, the ABNORM BLEED CONFIG (X BLEED CLOSED) trigger with its five conditions, the overtemperature add-ons with the VLS +10 / G DOT speed floor and approach block, the APU BLEED note and the INOP SYS listings per FCOM PRO-ABN-AIR. The automatic-closure matrix, loop logic, eutectic-salt self-reset and the no-reopen latch per AMM 36-22-00 and FCOM DSC-36-10-60 (developed in article 06); the APU-side shutdown cascade and STATUS entry per AMM 36-12-00. Overhead-panel announce-and-confirm protocol with the "AIR, XBLEED, CLOSE" example per FCTM AOP-30-30; smoke/odour propagation through the bleed system and the odour table per FCTM smoke guidance. The family-tree table and the worked scenario are integrative syntheses of the referenced material. Dispatch consequences reflect some operators' MEL practice (article 11).

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.