Cargo Ventilation — The Three Lower-Deck Compartments

Cargo Environmental Control gave the overview (ventilation + heating + the 21-40/21-45 effectivity). This deep-dive opens up lower-deck cargo ventilation itself: the three independent systems — bulk, forward, and aft — each with its own extract fan, isolation valves and ISOL pushbutton, all run by the one Ventilation Controller (VC, 280HN).

1. Three compartments — the FINs

Bulk: extract fan 282HN (three-phase, 140 °C cutout); isolation valves 283HN + 284HN; BULK ISOL pb 7HN.

Forward: extract fan 285HN (two-speed three-phase, 180 °C cutout, four vibration dampers); isolation valves 286HN + 287HN + 289HN; cold-air valve 298HN (from pack 2); COOLING selector 297HN (OFF/NORM/MAX passenger; 5–25 °C freighter); FWD ISOL pb 14HN.

Aft: extract fan 291HN (three-phase, 140 °C cutout); isolation valves 292HN + 293HN + 294HN; AFT ISOL pb 10HN.

Shared: the VC 280HN (dual-CPU), the OVHT COND FANS RESET pb 3HN, and (on a freighter variant) the main-deck shutoff valves 253–256HG (ata-21-10).

2. The airflow chain

   BULK:  floor-underfloor → isol 283HN → bulk → fan 282HN (140 °C) → isol 284HN → bilge → overboard
   FWD:   floor + bilge → isol 287HN/289HN ─┐
          pack-2 cold air → cold-air valve 298HN ─┤→ fwd cargo → fan 285HN (180 °C, 2-speed)
                                                  └→ isol 286HN → bilge → overboard
   AFT:   underfloor → isol 292HN/294HN → aft cargo → fan 291HN (140 °C) → isol 293HN → bilge → overboard

   all controlled by: VC 280HN (dual-CPU) + ISOL pbs (7/10/14HN) + SDCU/CIDS-SDF + LGCIU

3. The three extract fans

The extraction fan 282HN has a three-phase induction motor, and a fan wheel with high efficiency blades in a housing. ... Thermal switches are installed to stop the electrical power supply to the induction motor if the temperature increases to 140 DEG.C (284.00 DEG.F) or more. The extraction fan 285HN has a two-speed three-phase induction motor, and a fan wheel with high efficiency blades in a housing. ... if the temperature increases to 180 DEG.C (356.00 DEG.F) or more. The housing has four brackets with vibration dampers to attach the extraction fan to the aircraft structure. The extraction fan 291HN has a three-phase induction motor ... 140 DEG.C (284.00 DEG.F). — AMM 21-28-00 §6.C/D/E

[!warning]- The forward fan is the only two-speed one — and its 180 °C cutout is 40 °C above the others

The forward compartment is the only one with a pack-2 cold-air valve (298HN) and a cooling selector — it provides cooling as well as ventilation. The pack-2 cold-air flow adds to the ventilation flow → the total forward flow exceeds the bulk/aft → the fan works against a higher ΔP → a higher motor heat load → a two-speed design (low for normal, high for cooling) → a 180 °C cutout allowing a higher motor temperature. The bulk/aft 140 °C is the standard ventilation-fan threshold. Pilot meaning: a forward-ventilation failure differs from bulk/aft — it may also lose cooling, affecting perishable goods.

4. Forward only — cold-air valve + cooling selector

The COOLING mode selector 297HN is a rotary switch in a tubular metal body. ... It has an OFF, a NORM and a MAX position. The cold air valve 298HN has an electric motor, an electrically actuated clutch, a manual lever, an actuator and a butterfly valve. The electric motor drives the actuator to open and close the butterfly valve. The manual lever lets you see the position of the butterfly valve and you can change it manually. — AMM 21-28-00 §6.F

[!note]- The cold-air valve has an electrically actuated clutch — unlike the trim-air valves

Unlike the zone trim-air valves (stepper motor), the cold-air valve uses a plain motor + an electrically actuated clutch: clutch powered → the motor drives the valve; clutch de-energised → the motor disengages → the valve can be moved by hand (manual lever). The use case: in an emergency the crew or a mechanic can control forward cooling by hand — e.g. if the cooling selector (297HN) or the 298HN motor fails. The clutch + manual lever suit an "emergency-overridable" application.

On a freighter variant the selector instead offers a 5–25 °C temperature selection (plus OFF).

5. Isolation valves

The isolation valves 283HN and 284HN have an electric motor, a manual lever, an actuator and a butterfly valve. The electric motor drives the actuator to open and close the butterfly valve. — AMM 21-28-00 §6.C (2)

Each isolation valve is an electric-motor butterfly with a manual lever. They admit/discharge the ventilation flow and close (by ISOL pb or smoke) to isolate the compartment.

6. The three ISOL pushbuttons (7HN / 10HN / 14HN)

You can push the BULK ISOL VALVES pushbutton-switch 7HN (the OFF light comes on) to close the isolation valves 283HN and 284HN. Also the extraction fan 282HN stops. You can push the AFT ISOL VALVE P/BSW 10HN ... to close the isolation valves. You can push the FWD ISOL VALVES pushbutton-switch 14HN (the OFF light comes on) to close the isolation valves 286HN, 287HN and 289HN. Also the extraction fan 285HN stops. — AMM 21-28-00 §7.A/B/C

[!note]- All three ISOL pbs are on panel 212VU — one place

Panel 212VU (the pilot's overhead, right) carries all three ISOL pbs plus the bulk HOT AIR pb and bulk temperature selector (ata-21-05) — it is the A330's single concentration point for all cargo controls. Handling a cargo issue: look at panel 212VU and see every cargo control's state at a glance.

7. Smoke — automatic response

In case of smoke the isolation valves close automatically and the extraction fan stops. (bulk / aft) In case of smoke the isolation valves and the cold air valve close automatically and the extraction fan stops. (forward) — AMM 21-28-00 §5.G + §7

   SDCU (smoke-detection control unit) or CIDS-SDF detects smoke
        ▼ signal to VC 280HN (dual-CPU)
   ① close that compartment's isolation valves (bulk 2 / fwd 3 / aft 3)
   ② stop the extraction fan (282 / 285 / 291HN)
   ③ (forward only) also close the cold-air valve 298HN
   ④ trigger ECAM CARGO SMOKE
   ⑤ link to the ATA-26 fire procedure

[!warning]- On forward smoke the cold-air valve also closes — bulk/aft have no such step

The forward compartment has the pack-2 cold-air valve; if it stayed open in smoke → pack-2 cold air would keep entering the forward cargo → feeding oxygen to the fire. So forward smoke adds the extra step of closing the cold-air valve (extra oxygen starvation). All three: close the isolation valves + stop the fan. Forward only: also close the cold-air valve.

[!note]- The smoke auto-response is mechanically equivalent to a pilot pressing the ISOL pb

Smoke auto-response = the same valve-close + fan-stop as the ISOL pb. The only difference: smoke also triggers the ATA-26 fire procedure + ECAM CARGO SMOKE; a manual ISOL press only isolates without a warning.

8. Emergency power — the VC sheds the fan relays

The relay 26XE sends a signal to the ventilation controller 280HN if there is only emergency electrical power available. The ventilation controller stops the electrical power supply to the fan power relays. — AMM 21-28-00 §5.H

[!note]- On emergency power the VC stops all its fans — cargo ventilation too

This is the same action as in ata-21-15. All VC-controlled fans stop: the cabin recirculation fans, the galley/lavatory fans, the cargo extract fans (282/285/291HN), and the cargo-heating fans — to save power for the flight controls + displays. Effect: cargo unventilated (possible heat / odour / H₂ from e.g. lithium-battery cargo); the cabin still breathes on pack fresh air. Pilot meaning: dual-engine-out + RAT out → cargo ventilation stops + cabin ventilation degrades — a necessary trade-off.

9. OVHT COND FANS RESET pushbutton (3HN)

The OVHT COND FANS RESET pushbutton-switch 3HN has a built-in light with a FAULT legend. — AMM 21-28-00 §6.A

The one pushbutton that resets the thermal switches of both the cabin recirculation fans (after a 180 °C trip) and the cargo extract fans (after a 140 / 180 °C trip). The FAULT light on = a fan is in an overheat state; press RESET → if cooled, power is restored; if still over temperature, the FAULT light stays on.

10. Main-deck (freighter) ventilation ≠ lower-deck

[!note]- Main-deck ventilation is not an independent system — it is an extension of the cabin distribution/recirculation

Unlike the three independent lower-deck systems (bulk/forward/aft, each with its own fan + isolation valves — this article's subject), a freighter's main-deck cargo is ventilated as an extension of the cabin distribution + recirculation (ata-21-10) — no independent extract fan, served by the recirculation fans + pack-2 direct, with the main-deck shutoff valves 253–256HG and the five-action main-deck-smoke cascade. Pilot meaning: a lower-deck ventilation failure and a main-deck ventilation failure are two completely different systems.

Self-test

[!note]- Q1. Are the three lower-deck systems independent? Shared VC or separate controllers?

Three independent systems — bulk, forward, aft each have their own extract fan + isolation valves + ISOL pb — sharing the one VC 280HN (dual-CPU), the computer for four sub-systems (cargo ventilation + cargo heating + cabin distribution/recirculation + lav/galley). Independent ventilation → a fault/smoke in one does not affect the other two; the shared VC → fewer controllers + easier coordination.

[!note]- Q2. Why is the forward fan's cutout 180 °C vs 140 °C for bulk/aft?

The forward compartment is the only one with a pack-2 cold-air valve + a cooling selector. The added cold-air flow → a higher total forward flow → a higher fan ΔP → a higher motor heat load → a two-speed fan (low normal / high cooling) → a 180 °C cutout allowing a higher motor temperature. Bulk/aft 140 °C is the standard ventilation-fan threshold. A forward failure may also lose cooling (affecting perishables).

[!note]- Q3. Why does forward smoke also close the cold-air valve, when bulk/aft do not?

The forward compartment has the pack-2 cold-air valve; if it stayed open in smoke, pack-2 cold air would keep feeding oxygen to the fire. So forward adds closing the cold-air valve (extra starvation). All three: close isolation valves + stop the fan + ECAM CARGO SMOKE + the ATA-26 link. Forward only: + close the cold-air valve.

[!note]- Q4. What is the cold-air valve's electrically actuated clutch for?

A cutout between electrical and mechanical control: clutch powered → the motor drives the valve; clutch de-energised → the motor disengages → the valve can be moved by hand (manual lever). Use case: the crew/mechanic can control forward cooling by hand in an emergency — e.g. if the cooling selector or the motor fails. Versus the trim-air valves (stepper motor, no clutch), this plain-motor + clutch + manual-lever design suits an emergency-overridable application.

[!note]- Q5. Which fans does the VC stop on emergency power? All cargo ventilation?

On emergency power only, relay 26XE signals the VC → it stops all fan power relays. All VC-controlled fans stop: cabin recirculation, galley/lavatory, the cargo extract fans (282/285/291HN), and cargo heating — to prioritise the flight controls + displays. Effect: cargo unventilated (heat / odour / H₂ risk); the cabin still breathes on pack fresh air. A dual-engine-out + RAT case → cargo ventilation stops + cabin ventilation degrades — a necessary trade-off.

Key takeaways

Common misconceptions

Scope — what this deep-dive covers and defers

References

A330 specifics per AMM 21-28-00 §3/§5/§6/§7 (the three independent lower-deck systems — bulk with fan 282HN at 140 °C + valves 283/284HN + pb 7HN; forward with the two-speed fan 285HN at 180 °C with four vibration dampers + valves 286/287/289HN + the pack-2 cold-air valve 298HN with its electrically actuated clutch + the cooling selector 297HN (OFF/NORM/MAX passenger, 5–25 °C freighter) + pb 14HN; aft with fan 291HN at 140 °C + valves 292/293/294HN + pb 10HN — the electric-motor butterfly isolation valves, the smoke auto-response closing the isolation valves and stopping the fan (forward also the cold-air valve), the emergency-power fan-relay shedding via relay 26XE, and the OVHT COND FANS RESET pb 3HN). The forward-fan two-speed/180 °C reasoning, the forward-smoke oxygen-starvation logic, the clutch emergency-override use case, the panel 212VU concentration rationale, and the main-deck-vs-lower-deck distinction are integrative syntheses. All engineering detail is from the A330 knowledge base; 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.