Air Distribution And Recirculation

ATA21

The passenger cabin is divided into the FWD and AFT distribution zones which are supplied with temperature controlled and conditioned air.The conditioned air provided by the air conditioning packs 10HM (11HM) is supplied through a mixing unit installed under the cabin floor (in front of frame 36). Cabin air which has entered the underfloor area, is drawn through recirculation filters 4012HM (4013HM) by recirculation fans 14HG (15HG). The recirculation fans blow the air through check valves 4020HM (4021HM) to the mixing unit. The mixing unit mixes the conditioned air from the conditioning packs with the cabin recirculation air.

  • Final : khí quay vòng được hút đi qua 2 filter , qua 2 Cabin FAN và 1 check valve trước khi vào mixer unit.
  • 4 nhánh ống phía trên cao là 4 nhánh cấp khí điều hòa đi khắp cabin : Aft Zone LH , Aft Zone RH , Fwd Zone LH , Fwd Zone RH.
  • Một đường dẫn khí của emergency ram air inlet thông qua 1 check valve vào đường recirculation , cung cấp khí cho mixer unit trường hợp cả 2 Pack đều fail.
  • Lưu ý : cả Emergency ram air inlet và LP Ground Connector đều chung 1 đường ống vào mixer unit
  • Đó là lý do tại sao khi bật PACK , khí từ Pack sẽ tác động đến Check Valve của LP connector và Emergency ram air , dẫn đến hỏng Check valve.
  • Mixer Flap Actuator :
    • Normal Operation : When the PACK 1 and PACK 2 pushbutton switches or only the PACK 1 pushbutton switch is(are) ‘on’ the mixerflap actuator 20HB is in the closed position. Thus air is supplied from the pack 1 mixer chamber to the cockpit.When the PACK 1 pushbutton switch is released (the OFF legend is on) the mixerflap actuator opens and the air is supplied from the pack 2 mixer chamber to the cockpit.
    • Operation with Failures : If the mixerflap actuator 20HB has a failure, the ACSC 2 (57HH) monitors the failure and keeps it in the nonvolatile memory.
    • The mixer flap actuator 20HB operates a flap in the cockpit supply port of the mixer.A thermally protected 28 V DC motor drives the back-up flap through a reduction gearbox. Microswitches inside the mixer flap actuator 20HB prevent override of the flap at each end of its travel. A manual override lever and position indicator (on top of the actuator) make it possible to operate the flap manually.
  • the temperature sensor 24HK (for cockpit) is installed in the mixer unit.
  • the temperature sensor 25HK (for cabin) is installed in the mixer unit.
  • There are two mixer temperature sensors 24HK (25HK), one installed on each side of the mixer. The cockpit mixer temperature sensor is connected to the ACSC 1 and the cabin mixer temperature sensor is connected to the ACSC 2.
  • There are three duct-temperature sensors 15HK (16HK, 17HK), one installed in the main supply ducts to the cockpit, fwd cabin and aft cabin zones. Each sensor consists of a ventilated metal body into which are potted two thermistors. One thermistor supplies the lane 1, the other supplies the second lane of a ACSC. Each gives control indication and overheat detection. Also incorporated is a 6-pin electrical connector.
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