Ventilation Faults & Cargo-Fire Interaction

This article covers the A330's ventilation faults (five conditions) and the cargo-fire interaction (the cargo smoke conditions). It is where ATA 21 links to ATA 26 fire — the pilot must know both the ATA 21 component control and the ATA 26 agent-discharge timing.

1. Two fault families

Ventilation faults (5) — all L2, the aircraft keeps flying with limits:

Cargo smoke — all L2, but red LAND ASAP: FWD CRG / AFT-BULK CRG (passenger), LD FWD / MD (freighter), plus the detector-fault variants.

[!important]- ATA 21 vs ATA 26 — the boundary

System	Owns	Role in smoke handling
ATA 21	ventilation + isolation valves + bleed	isolate: ISOL VALVE OFF, CAB FANS OFF, PACK off
ATA 26	fire detection + the agent	extinguish: AGENT DISCH + the smoke detectors

The cargo-fire chain: the ATA 26 detector triggers SMOKE + the isolation valves auto-close → the pilot judges → AGENT DISCH (the ATA 26 agent) → the ATA 21 isolation (CAB FANS OFF + PACK off). This article covers the pilot-visible ATA 21 parts; the ATA 26 agent detail (type / discharge time) is not opened here.

2. VENT BLOWING FAULT — avionics cooling capacity abnormal

This alert triggers when the cooling capacity of the avionics ventilation blown air is abnormal. — FCOM PRO-ABN-VENT

   PACK FLOW ... HI       (increase the airflow)
   CAB FANS ... ON
   COCKPIT/CABIN TEMP ... DECREASE   (lower the recirculated-air temperature)
   IF WARNING AFTER 5 MIN: MAX FLT TIME ... 5 HOURS

[!warning]- The 5-hour limit protects minor equipment, not the avionics

Intuition: BLOWING FAULT = poor avionics cooling → fear the avionics overheat → 5 HRS is an avionics limit. In fact the FCOM states "This limitation is not applicable to other equipment" — the major avionics (flight controls, navigation) are not subject to it. The 5 HRS limits minor equipment: IFE, cabin communication — lower temperature tolerance, at risk only after 5 h. Teaching line: BLOWING FAULT is not "the aircraft falls after 5 hours" — it is "the IFE may fail after 5 hours". The three crew actions (PACK FLOW HI + CAB FANS ON + lower the temperature) are a triple compensation: more total flow, faster recirculation past the underfloor (indirectly cooling the avionics), and a lower recirculation-air temperature.

3. VENT EXTRACT FAULT — extract flow low

This alert triggers when the avionics ventilation extract flow is low. — FCOM PRO-ABN-VENT

   (Note: setting EXTRACT to AUTO may reset the AEVC and clear it — only if triggered on the ground at engine start)
   EXTRACT ... OVRD   (air is blown through the partially-open overboard valve; the underfloor valve is closed)

[!note]- The EXTRACT OVRD physical action

AUTO: the underfloor valve open + the overboard valve closed (normal — the avionics flow goes via the underfloor back to recirculation). OVRD: the underfloor valve closed + the overboard valve partially open (the flow exits overboard, bypassing a blocked underfloor path). Cost: the flow no longer returns to recirculation, and on single-pack operation the cabin pressure may not hold. A ground engine-start trigger may reset via EXTRACT → AUTO; an in-flight trigger cannot reset — use OVRD.

4. VENT OVBD VALVE FAULT — overboard valve mis-positioned

This alert triggers when the overboard extract valve is open at engine start or not partially open after override. — FCOM PRO-ABN-VENT

   EXTRACT ... OVRD
   IF OVBD STILL FULL OPEN:
     MAX FL ... 100/MEA-MORA; CAB PR MODE SEL ... MAN; CAB PR VALVE SEL ... BOTH; MAN V/S CTL ... FULL UP
     Pressurization is inhibited to avoid damage to the ducts.

[!warning]- With the overboard valve full open, pressurisation is inhibited — to protect the ducts

Intuition: the overboard valve full open = cabin leaking = depressurised → restore pressurisation. In fact the FCOM inhibits pressurisation "to avoid damage to the ducts". Why: a full-open overboard valve + a pressurised cabin → a large high-speed flow through the valve → an excessive duct internal flow speed + pressure gradient → possible duct damage (the duct's design max ΔP does not cover the "wide open + high pressurisation" combination). So: make the cabin equal ambient (MAX FL 100 + manual pressurisation V/S FULL UP, fully open the outflow valves) → ΔP to 0 → protect the ducts. Teaching line: "save the aircraft, not the pressurisation" — with the overboard valve already open the cabin cannot hold pressure anyway; cooperate, do not fight it.

5. VENT PACK BAY VENT FAULT & VENT GND COOL FAULT

VENT PACK BAY VENT FAULT triggers on ground when low ΔP is detected across the turbofan, and at least one pack is operating. → ONE PACK ... OFF VENT GND COOL FAULT triggers when the Ground Refrigeration Unit (GRU), fan or ground cool valve is failed. → GND COOL ... OFF; IF SKIN VALVE STILL OPEN: MAX FL 100 + MAN PRESS + V/S FULL UP — FCOM PRO-ABN-VENT

The pack-bay turbofan (bleed-driven) cools the pack bay on the ground; low ΔP across it = not working → ONE PACK OFF changes the bleed flow to try to restart it (ground-only — in flight the ram air cools the pack bay).

[!tip]- GND COOL FAULT and OVBD VALVE FAULT share the "skin valve open" sub-procedure

Both use the identical sub-procedure — MAX FL 100 + manual pressurisation + V/S FULL UP. Both have a skin valve (a fuselage-skin vent); if it sticks open, the effect is the same (a large cabin leak + a duct-ram risk) → the same handling. Teaching line: one rule — any skin valve stuck open → MAX FL 100 + manual pressurisation + V/S FULL UP.

6. Cargo smoke (passenger)

   LAND ASAP
   FWD ISOL VALVE (if not automatically closed) ... OFF
   IF FWD CRG CLOSED (ground only): FWD AGENT ... DISCH; CAB FANS ... OFF
   ON GROUND BEFORE OPENING CARGO DOORS: PAX ... DISEMBARK

[!important]- Four STATUS notes the pilot must read

1. Expect the SMOKE warning to remain after agent discharge, even if the smoke source is extinguished. Gases from smoke source are not evacuated, and smoke detectors are also sensitive to the extinguishing agent.
2. Once the isolation valves are closed, the cargo is not ventilated. Therefore, the cargo temperature is unreliable.
3. On ground, if the SMOKE warning is displayed with the cargo compartment door open, do not initiate AGENT DISCHARGE. Request the ground crew to investigate and eliminate the smoke source.
4. On ground, the warning may be triggered due to a high humidity. — FCOM PRO-ABN-SMOKE

[!warning]- The warning does not clear after the agent discharges

Intuition: discharge the agent → extinguish → the SMOKE warning clears. In fact the warning persists — three reasons: the smoke gases are not evacuated (the isolation valves are closed, no ventilation); the detectors are sensitive to the agent gas itself; residual smoke molecules linger in the sealed compartment. The pilot's real-vs-agent judgement: a warning before the discharge = real smoke; after the discharge = possibly agent gas + real smoke mixed; the only reliable confirmation is the ground crew opening the door after landing — which is why it is a red LAND ASAP.

The aft/bulk cargo smoke procedure adds one step: evacuate the lower-deck crew rest + close its door (the rest area is near the aft/bulk cargo, smoke may seep in) — the only ATA 21 procedure mentioning the crew-rest compartment.

7. Main-deck smoke (freighter) & detector faults

   LAND ASAP; IF REQUIRED CREW OXY MASKS USE/100%/EMERG
   CAB FANS ... OFF; GALLEY & LAV FAN ... OFF; GALLEY ... OFF
   CKPT/CAB COM ... ESTABLISH; CAB TO CRG DOORS ... CLOSE

[!important]- Freighter MD SMOKE vs passenger CRG SMOKE

	Passenger CRG SMOKE	Freighter MD SMOKE
Location	lower deck (belly)	main deck (the main hold)
Size	smaller	huge
Isolation	ISOL VALVE OFF + AGENT DISCH	doors + ventilation: CAB FANS OFF + GALLEY/LAV FAN OFF + CAB-CRG DOOR CLOSE
Agent	FWD/AFT AGENT (auto)	no agent (the main hold usually has no fixed agent system — crew handling)
Occupants	passengers + crew	crew only (supernumeraries)

A freighter main-deck fire is handled more manually — the main hold is both the cargo and the crew workspace, so isolation relies on doors + ventilation + oxygen + communication rather than an agent.

[!note]- Detector faults vs real smoke — the livestock exception

Detector-fault conditions (SMOKE DET FAULT / MD DET FAULT / LD DET FAULT) are not real smoke. Common handling: IF NO LIVESTOCK → close the ISOL VALVE / GALLEY+LAV FAN OFF + FWD CRG COOLING OFF + enhanced manual watch (the automatic detection is lost). The livestock exception: with live animals aboard, do not close the ISOL VALVE (they need ventilation) — the pilot trades "tolerate the failed detector but keep ventilation" against "close it but lose the animals' air", per the cargo manifest. The A330's animal-friendly design — many ECAM procedures carry an "IF NO LIVESTOCK" branch.

8. Decision trees & combinations

   VENTILATION fault:
     BLOWING FAULT     → PACK FLOW HI + CAB FANS ON + cool + 5 HRS limit
     EXTRACT FAULT     → EXTRACT OVRD (ground: try AUTO reset)
     OVBD VALVE FAULT  → EXTRACT OVRD; if still full open → MAX FL 100 + MAN PRESS + V/S FULL UP
     PACK BAY FAULT    → ONE PACK OFF (ground only)
     GND COOL FAULT    → GND COOL OFF; if skin valve open → MAX FL 100 + MAN PRESS + V/S FULL UP

   CARGO smoke:
     FWD CRG (pax)     → LAND ASAP + FWD ISOL OFF + FWD AGENT DISCH + CAB FANS OFF + the 4 notes
     AFT/BULK CRG (pax)→ LAND ASAP + AFT/BULK ISOL OFF + AFT AGENT DISCH + CAB FANS OFF + evacuate the crew rest
     LD FWD (fr)       → LAND ASAP + LD FWD ISOL OFF + LD FWD AGENT DISCH
     MD (fr)           → LAND ASAP + CREW OXY + CAB FANS OFF + GALLEY+LAV FAN OFF + CAB-CRG DOORS CLOSE

Self-test

[!note]- Q1. After VENT BLOWING FAULT, MAX FLT TIME 5 HOURS — what does the 5 hours protect?

Minor equipment (IFE / cabin communication), not the main avionics. The FCOM states "This limitation is not applicable to other equipment" — the main avionics are not subject to it. 5 HRS is the temperature-tolerance boundary of the minor equipment. Meaning: BLOWING FAULT lets you keep flying, but not beyond 5 hours — a long sector must divert en route.

[!note]- Q2. VENT OVBD VALVE FAULT, with the overboard valve still full open, the FCOM inhibits pressurisation — why?

To protect the ducts. The full-open valve + a pressurised cabin → a large high-speed flow → an excessive duct flow speed + pressure gradient → possible duct damage. Handling: make the cabin equal ambient (MAX FL 100 + manual pressurisation V/S FULL UP) → ΔP to 0. "Save the aircraft, not the pressurisation" — with the valve already open the cabin cannot hold pressure anyway.

[!note]- Q3. The SMOKE warning persists after AGENT DISCH — how does the pilot judge?

The FCOM states the warning persists after the discharge — three reasons: the smoke gases are not evacuated (the valves are closed); the detectors are sensitive to the agent gas itself; residual molecules linger. Real-vs-agent: a warning before the discharge = real smoke; after = possibly agent + real mixed; the only reliable confirmation is the ground crew opening the door after landing — hence the red LAND ASAP.

[!note]- Q4. How does freighter MD SMOKE differ from passenger CRG SMOKE?

Passenger: ISOL VALVE isolation + AGENT DISCH. Freighter MD: isolation by doors + ventilation (CAB-CRG DOOR CLOSE + CAB FANS OFF + GALLEY/LAV FAN OFF), crew only (supernumeraries), CREW OXY, and usually no fixed agent (crew handling). The main hold is both cargo and the crew workspace, so it is more manual.

[!note]- Q5. SMOKE FWD CRG on the ground with the cargo door open — discharge the agent?

No. The FCOM: "do not initiate AGENT DISCHARGE" — with the door open the agent leaks out (ineffective + wasted + an agent-gas hazard to the ground crew). Instead request the ground crew to investigate and eliminate the source (it may be humidity / dry ice / agent residue / a real fire) — they judge and handle.

Key takeaways

Common misconceptions

Scope — what this article covers and defers

References

A330 specifics per FCOM PRO-ABN-VENT (the five ventilation faults — BLOWING FAULT with its 5-hour minor-equipment limit, EXTRACT FAULT with the OVRD / AEVC reset, OVBD VALVE FAULT with the duct-protection pressurisation inhibit, PACK BAY VENT FAULT with the ONE PACK OFF, and GND COOL FAULT with the shared skin-valve sub-procedure) and FCOM PRO-ABN-SMOKE (the cargo smoke conditions — FWD/AFT-BULK CRG passenger with the four STATUS notes and the agent-discharge persistence, LD FWD / MD freighter, and the detector-fault variants with the livestock exception). The ATA 21 / ATA 26 boundary, the 5-hour minor-equipment reading, the duct-protection rationale, and the freighter-vs-passenger comparison are integrative syntheses; the ATA 26 agent detail is deferred. All engineering detail is from the A330 knowledge base; the procedures are presented generically without operator-specific SOP or effectivity tail numbers, 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.