Cargo Smoke and the LAND ASAP Decision

Cargo smoke is the most unusual fire in the chapter: invisible, unreachable, and you cannot confirm it is out even after discharging Halon — the warning simply stays on. Where the cockpit/cabin smoke of article 10 can at least be smelled and traced, cargo smoke gives you one light and one warning — a pure blind fire. So its handling is essentially one decision: discharge, then LAND ASAP, and race the 260-minute agent clock. This article develops that decision, especially the most treacherous reverse-intuition: discharging the AGENT and the warning staying on is normal — it does not mean the fire is not out; you simply cannot confirm extinguishment, so you assume the worst and land.

1. Invisible and unreachable — only a light confirms it

"The cargo compartments are designed to be air-tight and fireproof in order to contain a fire. The cargo ventilation is designed to prevent the cargo smoke from coming to the cockpit/cabin. Therefore, the flight crew should be aware that a cargo smoke is not perceptible from the cockpit/cabin. The flight crew can only confirm a SMOKE AFT(FWD) CRG SMOKE alert with the SMOKE light illuminated on the CARGO SMOKE panel."

[!warning]- "Cannot see it, cannot smell it" is a designed strength, not a flaw The hold is deliberately an air-tight, fire-resistant box with ventilation arranged to keep smoke out of the cabin — precisely to "keep the fire in the box, keep the smoke out of the cabin". The price is that the crew lose sensory confirmation and must trust the instruments (SMOKE light/warning). This is the opposite extreme to cockpit smoke (10, smellable and traceable). So cargo-smoke handling rests from the start on "I cannot see it — I trust the instruments and plan for the worst."

2. Discharge and LAND ASAP

The system has already isolated on detection (auto valve close + fan stop, article 06); the crew's action is discharge plus the diversion decision. Discharge is the two-bottle sequence of article 06 (knockdown bottle 1 ~60 s + metered bottle 2). The diversion is committed immediately — the same "time critical, divert first" philosophy as article 10: a cargo fire is invisible and Halon only suppresses, so the safe assumption is "the fire is still there, the agent is on a countdown", and LAND ASAP follows detection.

3. 260 minutes — the diversion ruler

Bottle 2's flow metering holds concentration for 260 minutes (≥ 5 % in flight / ≥ 3 % on landing, article 06). At the decision level this is the hard constraint on how far you can divert: metered agent lasts at most 260 minutes, after which the fire is no longer suppressed and may reignite. So from the moment of discharge, you have about 260 minutes to be on the ground — the diversion must complete in under 260 minutes, or the agent runs out en route.

[!warning]- The cargo-fire time ruler is agent-concentration duration — the agent is itself the countdown Not oxygen, not fuel — the extinguishing agent is the clock. This differs from an engine fire (confirmable extinguished, no countdown) and from an MDCC fire (oxygen countdown, 07). Line the three up: engine fire watches the light (out means done), passenger cargo fire watches the Halon (260 min), freighter MDCC fire watches the oxygen.

4. Warning stays on after discharge = normal — never read it as "not out"

The most treacherous point, and where cargo-fire handling is most easily mis-judged:

"The flight crew should also expect the SMOKE AFT(FWD) CRG SMOKE alert to remain after agent discharge, even if the smoke source is extinguished. Gases from the smoke source are not evacuated, and smoke detectors are sensitive to the extinguishing agent, as well. Once isolation valves are closed, the cargo is not ventilated. Thus, the cargo temperature is unreliable."

[!warning]- You discharged, the warning is still on — that is normal, not a failure Two reasons: the smoke gas cannot leave (the isolation valves are closed and the fan stopped to hold the Halon), so the existing smoke stays and the detector keeps seeing it; and the detector is sensitive to Halon itself — the very agent you released keeps it alarming. So a cargo fire has a hard truth: you can never confirm from the cockpit that the fire is out — the warning's state is no evidence either way (cleared could mean the detector burned out, uncleared is simply normal). The only rational response: assume the fire persists, fly the LAND ASAP within the 260-minute window, and neither panic-escalate because "the warning did not clear" nor relax the diversion because "it did clear". Temperature is likewise unreliable once isolated — do not use it to judge the fire. The warning is an "it triggered" switch, not a "fire out" gauge — do not expect it to tell you the result.

5. On the ground — do not open the door, and do not discharge with a door open

"Order the ground crew not to open the door of the affected cargo compartment, unless passengers have disembarked and fire services are present. If the SMOKE CRG SMOKE alert is displayed on ground, with the cargo compartment door open, do not initiate AGENT DISCHARGE. Request that the ground crew investigate and eliminate the smoke source. On ground, the alert may be triggered due to high level of humidity."

[!warning]- Two ground disciplines — do not feed it, do not waste the agent

• Do not rush to open the door: an open door lets fresh air in, which can feed a smouldering fire into open flame (re-oxygenation) — open only once passengers are off and fire services are present.
• Do not discharge the AGENT with a door open: Halon builds concentration in a sealed hold, so discharging with the door open is throwing agent out of an open window — it will not extinguish, wastes the one-shot resource, and may harm the crew at the door. On the ground with a door open, have the ground crew investigate manually — do not discharge (and on the ground the alert is quite likely a humidity nuisance, per the heated detectors of 06).

6. Operations — the decision chain and the three-fire comparison

  (hold) CRG SMOKE -> already automatic: isolation valve closed + extraction fan stopped
   1  confirm the compartment (from the SMOKE light — you cannot sense it)
   2  AGENT (compartment) DISCH   both bottles to that hold (knockdown + 260 min maintenance)
   3  LAND ASAP -- diversion under 260 min (nearest suitable airport)
   4  warning stays on? temperature odd? -> trust neither; fly the diversion assuming the fire persists
   5  landing: order ground crew not to open the door (unless disembarked + fire services); door open -> do not discharge
  freighter MDCC: depressurisation firefighting + two-stage LAND ASAP (article 07)

The chapter's three-fire decision summary:

Self-test

[!note]- Q1. Why is cargo smoke invisible and unreachable — flaw or strength? How is it confirmed? A designed strength: the hold is an air-tight, fire-resistant box that keeps smoke from the cabin. Confirmed only by the SMOKE light/warning.

[!note]- Q2. AGENT discharged, warning still on — not out, or normal? Why? The two reasons? Normal. The isolated hold does not vent the existing smoke, and the detector is sensitive to the Halon itself.

[!note]- Q3. How does 260 minutes set the diversion radius? How does the cargo-fire time ruler differ from engine and MDCC fires? Metered agent lasts ≤ 260 min, so divert in under 260 min. Engine fire has no countdown (confirmable out); MDCC is oxygen-limited; cargo is agent-limited.

[!note]- Q4. Why is cargo temperature unreliable once isolated? Can you use it to judge the fire? The hold is no longer ventilated after the valves close, so temperature is unreliable — do not use it to judge the fire.

[!note]- Q5. On the ground with a SMOKE alert and the door open, why not discharge the AGENT? Why not rush to open the door? Halon needs a sealed hold; discharging with the door open wastes it. Opening the door feeds fresh air to a smouldering fire — open only once disembarked and fire services are present.

Key takeaways

References

• FCTM PR-AEP-SMOKE (CARGO SMOKE) — air-tight/fire-resistant, not perceptible, confirmed only by the SMOKE light, warning stays after discharge (smoke not vented + detector sensitive to agent), temperature unreliable, ground door disciplines / humidity nuisance.
• FCTM PR-AEP-SMOKE (MDCC) — freighter depressurisation firefighting (article 07).
• FCOM DSC-26-50-10 — two bottles 60 s / 260 min, auto isolation (article 06).

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.