Aft Cargo Compartment Ventilation

ATA21

Aft Cargo Compartment ventilation

  • Air source : The airflow comes from the cabin zones through the openings in the cabin floor behind the sidewall panels.
  • Air Suction : The suction from extraction fan 35HN causes air to flow into the ventilation system of the aft cargo compartment and it operates on ground and in flight.
  • The Main Components :
    • Cargo Ventilation Controler 10HN : Cargo ventilation controller 10HN controls and monitors the isolation valves 33HN, 34HN and extraction fan 35HN. The controller sends a signal to the ECAM and the CFDS through the air conditioning system controller (ACSC1), if there is a fault in the valves or in the fan.
    • Isolation Valve 33HN ( inlet )
    • Isolation Valve 34HN ( outlet) : Aft cargo-compartment isolation-valves 33HN and 34HN are electrically operated butterfly valves. Two microswitches signal the fully open/fully closed position of isolation valves 33HN and 34HN to cargo ventilation controller 10HN.
    • Extraction Fan : This fan runs continuously when the aircraft is on ground or in flight. Thermo switches are installed inside the motor stators of the extraction fan. If the temperature of the stators increases to 140 DEG.C (284 DEG.F), the thermo switches isolate the electrical supply to the fan.
  • Operation Control and Indicating
    • The cargo ventilation controller 10HN opens the isolation valves 33HN and 34HN. After the ventilation controller receives fully open signals from both valves, it starts the extraction fan 35HN. 
    • The controller will close the isolation valves, and stop the extraction fan when: 
      • the isolation valve switch 36HN is selected OFF
      • the smoke detection control unit 10WQ detects smoke in the AFT cargo compartment
    • Aft isolation valve switch 36HN is installed on panel 22VU in the cockpit overhead panel. It controls isolation valves 33HN, 34HN and extraction fan 35HN. Cargo ventilation controller 10HN will only start the fan if a fully open signal is received from both isolation valves.
    • With the isolation valve switch 36HN pushed-in, isolation valves 33HN and 34HN open fully and extraction fan 35HN starts. When the isolation valve switch is released-out, the OFF light comes on white, the isolation valves close and the extraction fan stops. The fault light comes on amber if either isolation valve is not fully open or fully closed
    • If the isolation valve is not in fully open or not fully closed condition, ventilation controller 10HN will also send a signal to the Flight Warning Computer (FWC). 
    • If there is an extraction fan fault, the ventilation controller gives a signal to the FWC through (ACSC1) 47HH which generates the appropriate failure message for the Centralized Fault Display System (CFDS) 

Ecam Message :

  • AIR AFT CRG VENT FAULT

With ECAM message : AIR AFT CRG VENT FAULT , refer to MEL : 21-28-03A : EXTRACTION FAN inop , must set OFF to AFT ISOL VALVE , it means turn off 2 isolation valves.

  • COND AFT CRG ISOL VALVE

MEL : 21-28-04A : 2 isolation valves may be inop at close position with condition :

+ FAULT LIGHT Of AFT ISOL VALVE P/B is ok

+ Both isolation valve are check closed


If AFT ISOL VALVE P/B is FAULT , It mean 2 isolation valves is not closed , so they must be secure in closed position.

MEL : 21-28-04B : deactive both isolation valves inclose position, notice that if only one valve inop , it always must secure both valves in closed position. See AMM for more detail

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