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    G150-Environmental Control System

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    Helene Anester
    The document describes the environmental control system (ECS) of an aircraft. The ECS provides conditioned air for ventilation, cabin pressurization, and temperature control using bleed air from the engines. It includes a pre-cooler, air cycle machine, and mixing system to control air temperature. The pressurization system automatically controls cabin pressure through outflow valves. Controls and indicators are provided for pilots to select air sources, temperature settings, and switch to manual operation if needed.

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    G150-Environmental Control System

    Uploaded by

    Helene Anester
    20 views12 pages
    The document describes the environmental control system (ECS) of an aircraft. The ECS provides conditioned air for ventilation, cabin pressurization, and temperature control using bleed air from the engines. It includes a pre-cooler, air cycle machine, and mixing system to control air temperature. The pressurization system automatically controls cabin pressure through outflow valves. Controls and indicators are provided for pilots to select air sources, temperature settings, and switch to manual operation if needed.

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    Original Title

    G150-ENVIRONMENTAL_CONTROL_SYSTEM

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    The document describes the environmental control system (ECS) of an aircraft. The ECS provides conditioned air for ventilation, cabin pressurization, and temperature control using bleed air from the engines. It includes a pre-cooler, air cycle machine, and mixing system to control air temperature. The pressurization system automatically controls cabin pressure through outflow valves. Controls and indicators are provided for pilots to select air sources, temperature settings, and switch to manual operation if needed.

    Copyright:

    © All Rights Reserved
    Download as PDF, TXT or read online from Scribd
    Download as pdf or txt
    20 views12 pages

    G150-Environmental Control System

    Uploaded by

    Helene Anester
    The document describes the environmental control system (ECS) of an aircraft. The ECS provides conditioned air for ventilation, cabin pressurization, and temperature control using bleed air from the engines. It includes a pre-cooler, air cycle machine, and mixing system to control air temperature. The pressurization system automatically controls cabin pressure through outflow valves. Controls and indicators are provided for pilots to select air sources, temperature settings, and switch to manual operation if needed.

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    © All Rights Reserved
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    of 12

    Section VII

    Systems

    ENVIRONMENTAL CONTROL SYSTEM (ECS)


    DESCRIPTION
    The environmental control system (ECS) provides conditioned air for
    ventilation, cabin pressurization and temperature control. The system
    utilizes engine bleed air supplied from the high and low pressure ports
    of each engine.

    The LP and HP lines of each engine are connected to a bleed


    switching valve (BSV) which automatically transfers the source
    selection to HP if LP pressure is lower than 21.5 psi.

    The two common lines from both BSV's are interconnected to a main
    line that supplies air to the environmental control unit (ECU).

    A pre-cooler and an ozone converter are installed on the main line. The
    pre-cooler is equipped with a pneumatic bypass line that prevents the
    pre-cooler discharge temperature from dropping below 149°C (300°F).
    Heat sink for the pre-cooler is provided by ram air discharged from the
    air cycle machine (ACM) heat exchangers. Ram air for heat sink is
    supplied through a scoop located in the dorsal fin.

    Further downstream the bleed air is supplied to the ACM which has a
    low pressure water separator.

    If the air conditioning system fails, LP bleed air is supplied from the
    right engine for pressurization by placing the ECS selector in EMERG
    position. A ram air ventilation system is also incorporated as a backup
    system for operation at low altitudes. Ram air enters the ventilation
    system through a flush NACA scoop located in the aft fuselage.

    Mixing cold air provides temperature control for both cockpit and cabin.
    Single temperature control system is provided for both cabin and
    cockpit. The conditioned air is supplied to both cabin and cockpit
    through the air distribution system.

    10 Sep 2006 VII-21-1


    Section VII
    Systems
    AIR CONDITIONING SYSTEM
    Air conditioning may be utilized on ground or in flight. Cockpit and
    cabin temperature is normally preset for automatic control (CABIN
    MAN pushbutton - off) then selecting desired temperature position on
    TEMP CONTR knob. A secondary, manual system, for temperature
    control is also provided by pressing CABIN MAN pushbutton - ON. Use
    of air conditioning system, on ground, requires operation of APU, or
    either engine, at low thrust setting.

    PRESSURIZATION SYSTEM
    Cabin pressurization is obtained by controlling conditioned air outflow
    from the cabin.

    Normal operation of the pressurization system is automatic and only


    requires selection of the landing field elevation, which can be made
    before take-off. Cabin altitude rate of change is normally set to nominal
    values of 600 fpm (ascent) and 360 fpm (descent). The system
    controls cabin pressure by metering the outflow of air from the cabin
    through the outflow valve. Digital controller directly drives the valves
    which respond to signals by modulating the airflow.

    The system prevents exceeding cabin altitude of 13,500 ft in case of


    failure. The CPCS (cabin pressure control system) status is checked
    by pressing MODE SEL pushbutton to off (light out) and observing that
    FAULT light comes on momentarily.

    Manual control of the system is possible at pilot discretion or after


    failure of the digital controller or electrical failure. In this case, cabin
    pressure is regulated through manual control unit, controlling the
    outflow valve which allows selection of raising or lowering cabin
    altitude at a selected rate. Cabin altitude is held then by an isobaric
    hold function.

    (Continued)

    VII-21-2 10 Sep 2006


    Section VII
    Systems
    Cabin pressure differential is limited to a maximum of 8.95 psi by an
    automatically operated relief valve. Negative pressure in the cabin is
    relieved automatically by air flowing through the ram air scoop, passing
    through a check valve. The cabin door seal is pressurized from the
    hydraulic tank pressurization line. Seal pressure is regulated to 30 psi.
    If the seal is deflated, DOOR SEAL PRESS LOW message is on.

    SYSTEM AUTOMATIC OPERATION


    Ground mode: As electrical power is supplied, the system performs
    self-test, indicated by momentary illumination of FAULT light. If the
    CPCS determines that power lever is set at less than 70% N1 position
    and landing gear weight on wheels switch is pressed, it commands the
    outflow valves to fully open position. It is possible at this time to set the
    pressurization parameters: landing field elevation altitude (FIELD
    ELEV knob is used for manual setting).

    Take-off mode: As power lever is advanced to 70% N1 position or


    higher, the CPCS sets the current cabin altitude as its reference.
    Cabin altitude starts decreasing at the nominal rate, till it is about 250 ft
    below the reference. This assures smooth transition of cabin
    environment into pressurized flight. If take-off is aborted, cabin returns
    to ground mode at the nominal rate.

    Flight mode: The CPCS senses flight when the landing gear weight on
    wheels switch is released.

    The cabin altitude is then adjusted at a rate proportional to the aircraft


    rate of climb, preprogrammed into the CPCS logic. It also considers
    the selected landing field elevation. As the aircraft leaves the ground,
    cabin altitude automatically climbs or descends until it intersects on
    automatic cabin altitude schedule. Cabin rate of change never exceeds
    its rate limit and is less than this limit when the aircraft climbs or
    descends at less than maximum rate.
    (Continued)

    10 Sep 2006 VII-21-3


    Section VII
    Systems
    Once the aircraft has been in steady state flight for one minute, present
    cabin altitude is locked at this value to provide a steady state cabin
    altitude. If aircraft changes altitude, cabin pressure changes till a new
    cruise condition is established. To prevent unwanted cabin altitude
    variations during rough-air flight, aircraft altitude signal is buffered to
    permit rapid aircraft altitude excursions of ± 500 fpm before releasing
    established cruise condition. Upon an aircraft descent of 500 fpm or
    more, descent mode detector is triggered, which commands the cabin
    to proceed to the selected landing field elevation.

    Cabin differential pressure (∆P) is continuously monitored not to


    exceed 8.95 psi. During flight, cabin altitude changes to either the
    scheduled altitude or the selected landing altitude, as appropriate.

    Landing mode: During descent, cabin altitude decreases. If selected


    landing field elevation is higher than actual field elevation, the cabin
    depressurizes before reaching the ground. If selected landing field
    elevation is lower than actual field elevation, the aircraft lands with
    pressurized cabin. In this case, upon touchdown, the cabin will start to
    climb at 500 fpm for one minute before switching to ground mode
    (outflow valve fully open).

    VII-21-4 10 Sep 2006


    Section VII
    Systems

    Figure 7-21-1. Cabin Pressure Control System -


    Schematic

    10 Sep 2006 VII-21-5


    Section VII
    Systems

    Figure 7-21-2. Engines and APU Bleed Air System -


    Schematic

    VII-21-6 10 Sep 2006


    Section VII
    Systems

    Figure 7-21-3. Temperature Control System - Schematic

    10 Sep 2006 VII-21-7


    Section VII
    Systems

    Figure 7-21-4. Cabin Air Distribution System - Schematic

    VII-21-8 10 Sep 2006


    Section VII
    Systems
    ECS CONTROLS AND INDICATORS (Figure 7-21-5)
    ECS selector - Controls air source shutoff valves according to following
    positions:

    RAM - Closes both engine bleed and APU air supplies and
    opens outflow valves, simultaneously dumping cabin
    pressure through outflow valve. Used only as required
    at altitudes below 13,000 ft. Temperature control is not
    available in RAM position.
    APU - Selects bleed air from APU only.
    L ENG - Selects bleed air from left engine only.
    BOTH ENGINES - Selects bleed air from both engines.
    R ENG - Selects bleed air from right engine only.
    EMERG - Connects R engine, low-pressure bleed air port,
    directly to the mixing plenum in the cabin. Provides
    emergency air pressure source, to prevent cabin
    decompression, if airconditioning system fails. Cabin
    temperature is controlled by right engine thrust.

    TEMP CONTR knob - Used for cabin temperature control.

    DEFOG switch - Controls windshield defog air temperature.

    AIR COND switch - Controls cockpit air temperature.

    APU AIRFLOW pushbutton - Pressed to increase APU conditioned air


    flow. HI FLOW light comes on.

    CABIN TEMP pushbutton - Allows selection of automatic or manual


    control of cabin temperature, overrides automatic
    system operation. MAN light comes on.

    FIELD ELEV knob- Used for manual setting of the required landing
    field elevation in 50 feet increments (msl).
    (Continued)

    10 Sep 2006 VII-21-9


    Section VII
    Systems
    MODE SEL pushbutton - Used when reverting to manual
    pressurization controls. MAN light comes on.

    DUMP pushbutton - Used to dump cabin pressure in emergency; cabin


    altitude is limited to 13,000 ft ± 1500 ft. (Cabin rate
    may reach 10,000 fpm).

    DITCH pushbutton - Closes outflow valve for ditching.

    CABIN ALT knob - Used for manual control of cabin altitude, overriding
    automatic operation. INCR position causes the outflow
    valves to open, raising the cabin altitude; DECR
    position closes the valves and lowers cabin altitude.

    EICAS Displays
    On primary page:
    Cabin Altitude
    Cabin Altitude Manual Mode Annunciation
    Cabin Differential Press
    Cabin Rate
    Cabin Rate Arrow
    On secondary page:
    Landing field elevation

    (Continued)

    VII-21-10 10 Sep 2006


    Section VII
    Systems
    Warning Messages
    BLEED PRESS/TEMP HI - Excessive pressure or temperature
    downstream of either bleed switching valve
    CABIN DOOR UNLOCK - Cabin door is unlocked
    DUCT TEMP HI - Excessive duct-air temperature downstream of
    mixing plenum
    L ENG/APU BLEED LEAK - Leak or rupture in bleed air ducting
    from left engine or APU. APU automatically shuts
    down
    R ENG BLEED LEAK - Leak or rupture in bleed air ducting from
    right engine
    CAB ALT 15000 - Cabin altitude above 15,000 ft. Cabin pressure
    controller malfunction
    CAB ALT HI - Cabin altitude above 10,000 ft. Cabin pressure
    controller auto mode malfunction
    Caution Messages
    CAB AUTO PRESS FAIL - Automatic cabin pressurization failure
    CAB AUTO TEMP FAIL - Cabin automatic temperature control
    malfunction
    DOOR SEAL PRESS LOW - Cabin door seal is not inflated
    NOSE TEMP HI - Nose compartment blowers malfunction
    Status Messages
    CAB PRESS IN TEST - Cabin pressure control system test is in
    progress
    CAB PRESS MONITOR - Malfunction in cabin pressure control
    monitoring
    ECS BLEED OFF - ECS selector in RAM position or APU position
    and APU not running
    Advisory Messages
    CAB PRESS TEST OK - Successful cabin pressure control system
    test
    CABIN DOOR UNLOCK - Cabin door checked locked and Cabin
    Door Reset pushbutton has been pressed after CABIN
    DOOR UNLOCK caution message

    10 Sep 2006 VII-21-11


    Section VII
    Systems

    Figure 7-21-5. ECS Controls and Indicators

    VII-21-12 10 Sep 2006

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