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B737 NG Air Systems
 

B737 NG Air Systems

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B737NG Overview of the pneumatic systems

B737NG Overview of the pneumatic systems

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    B737 NG Air Systems B737 NG Air Systems Presentation Transcript

    • •B 737 NG Ground School.See the aircraft study guide at www.theorycentre.comThe information contained here is for training purposes only. It is of a general nature it isunamended and does not relate to any individual aircraft. The FCOM must be consulted forup to date information on any particular aircraft.B 737 NG Ground School.
    • PNEUMATIC SYSTEMS
    • IntroductionAir for the bleed air system can be supplied by the engines, APU, or an external aircart/source. The APU or external cart supplies air to the bleed air duct prior toengine start. After engine start, air for the bleed air system is normally supplied bythe engines.The following systems rely on the bleed air system for operation:• Air conditioning/pressurization• Wing and engine thermal anti-icing• Engine starting• Hydraulic reservoirs pressurization• Water tank pressurizationSwitches on the air conditioning panel operate the APU and engine bleed air supplysystem.NOTE; There are number of different options and some panels vary by aircraft. Thispresentation is generic and not aircraft specific
    • Engine Bleed System Supply
    • Engine Bleed System SupplyEngine bleed air is obtained from the 5th or 9th stages of the compressorsection.When 5th stage low pressure bleed air is insufficient for the bleed air systemrequirements, the high stage valve modulates open to maintain adequate bleedair pressure. During takeoff, climb, and most cruise conditions, low pressurebleed air from the 5th stage is adequate and the high stage valve remainsclosed.
    • Engine Bleed Air ValvesThe engine bleed air valve acts as a pressure regulator and shutoff valve. Withthe engine bleed air switch ON, the valve is DC activated and pressureoperated.The valve maintains proper system operating pressure and reduces bleed airoutflow in response to high bleed air temperature.
    • Engine Bleed Air Switches
    • Bleed Trip SensorsBleed trip sensors illuminate the respective BLEED TRIP OFF light when engine bleedair temperature or pressure exceeds a predetermined limit. The respective enginebleed air valve closes automatically.
    • Bleed Trip SensorsBleed trip sensors illuminate the respective BLEED TRIP OFF light when engine bleedair temperature or pressure exceeds a predetermined limit. The respective enginebleed air valve closes automatically.Unregulated Air temperature254 C or Pressure 220 PSIbefore the engine bleedvalve which is a PRSOV.If the upstream pressure ortemperature exceed theselimits the PRSOV would notbe able to regulate eitherpressure or temperature. Inthis case it will close.
    • Engines bleed air Pre-CoolerThe bleed air pre-cooler system controls thetemperature of the engine bleed air before itgoes into the pneumatic manifold. EngineFan air is used to cool the bleed air.A pre-cooler control valve controls theamount of fan air that flows through the pre-cooler.
    • Engines bleed air Pre-CoolerThe bleed air pre-cooler system controls thetemperature of the engine bleed air before itgoes into the pneumatic manifold. EngineFan air is used to cool the bleed air.A pre-cooler control valve controls theamount of fan air that flows through the pre-cooler.• Valve begins to open whenbleed air temperature is 199°C
    • Engines bleed air Pre-CoolerThe bleed air pre-cooler system controls thetemperature of the engine bleed air before itgoes into the pneumatic manifold. EngineFan air is used to cool the bleed air.A pre-cooler control valve controls theamount of fan air that flows through the pre-cooler.• Valve begins to open whenbleed air temperature is 199°C•Full open at 227°C
    • Engines bleed air Pre-CoolerThe bleed air pre-cooler system controls thetemperature of the engine bleed air before itgoes into the pneumatic manifold. EngineFan air is used to cool the bleed air.A pre-cooler control valve controls theamount of fan air that flows through the pre-cooler.• Valve begins to open whenbleed air temperature is 199°C•Full open at 227°C•OR with WAI ON
    • Engines bleed air Pre-CoolerThe bleed air pre-cooler system controls thetemperature of the engine bleed air before itgoes into the pneumatic manifold. EngineFan air is used to cool the bleed air.A pre-cooler control valve controls theamount of fan air that flows through the pre-cooler.• Valve begins to open whenbleed air temperature is 199°C•Full open at 227°C•OR with WAI ON•The engine bleed valve willreduce flow to assist the Pre-cooler. If air temperatureupstream of the bleed valve is toohigh (254 C) the bleed valve willclose.
    • TRIP RESET SwitchPush (if fault condition iscorrected) –• resets BLEED TRIP OFF,PACK TRIP OFF and ZONETEMP lights• related engine bleed valveopens, or related pack valveopens, or related air mixvalve opens• lights remain illuminateduntil reset.
    • TRIP RESET SwitchPush (if fault condition iscorrected) –• resets BLEED TRIP OFF,PACK TRIP OFF and ZONETEMP lights• related engine bleed valveopens, or related pack valveopens, or related air mixvalve opens• lights remain illuminateduntil reset.TRIP RESET push-button switch. A holding circuit connects through the air conditioning panelTo get control of the engine bleed system after a bleed trip off, these conditions must occur:* The overpressure or over temperature condition must no longer exist.* You must push the air conditioning panel TRIP RESET pushbutton switch .
    • The pneumatic manifold hastwo pressure transmitters.One transmitter is on the rightside of the manifold and theother is on the left side. Theymeasure the manifoldpressures.Pressure indication is on theair conditioning panel.
    • DUCT PRESSURE TRANSMITTERLeft manifold DC bus 1Right manifold DC bus 2PRESSURE GAUGEAC power fromTransfer bus 2
    • Isolation ValveThe isolation valve isolates the left and right sides of the bleed air duct during normaloperations. The isolation valve is AC operated. Transfer bus 1.With the isolation valve switch in AUTO, both engine bleed air switches ON, and both airconditioning pack switches AUTO or HIGH, the isolation valve is closed.The isolation valve opens if either engine bleed air switch or air conditioning pack switch ispositioned OFF. Isolation valve position is not affected by the APU bleed air switch.
    • With the isolation valve inauto if any of the 4 cornerswitches are off theisolation valve will openThe APU bleed air switch doesnot affect the isolation valve
    • External Air ConnectionAn external air cart/source provides an alternate air source for engine start orair conditioning. External air connects to the right side of the bleed air duct..
    • APU Bleed Air ValveThe APU bleed air valve permits APU bleed air to flow to the bleed air duct. TheAPU bleed air valve is DC controlled via the APU ECU and pressure operated. Ifthe APU is not running the APU bleed valve will close.The APU check valve prevents engine bleed air flow into the APU load compressor.With both the APU and engine bleed air valves open, with the engines operating atidle thrust, there is a possibility of APU bleed air back pressuring the 9th stagemodulating and shutoff valve. This would cause the 9th stage valve to close.
    • DUAL BLEED LightThe DUAL BLEED lightilluminates whenever the APUbleed air valve is open and theposition of the engine bleed airswitches and isolation valvewould permit possible backpressure of the APU.Therefore, thrust must belimited to idle with the DUALBLEED light illuminated.
    • ENGINE 25th or 9thstage air.ENGINE 15th or 9thstage air.ENGINE ANTI-ICEENGINE STARTWING ANTI-ICE WING ANTI-ICEL PACK ValveWater tank Press APU Check valveAPU SUPPLYR PACK ValveGround AirISOLATION VALVENitrogen Gas Generation Duct Pressure transmittersHydraulic Reservoir PressENGINE STARTENGINE ANTI-ICE
    • How are the engine bleed air valves operated?a) AC activated and pneumatically operated.b) DC activated and pneumatically operated.c) AC motor operated.d) DC motor operated.
    • How are the engine bleed air valves operated?a) AC activated and pneumatically operated.b) DC activated and pneumatically operated.c) AC motor operated.d) DC motor operated.
    • What is the position of the isolation valve when the switch is in AUTO?a) Valve is always open.b) Valve is always closed.c) Valve opens automatically when any bleed air switch or pack switch is OFF.d) Valve modulates automatically depending on pneumatic system loads.
    • What is the position of the isolation valve when the switch is in AUTO?a) Valve is always open.b) Valve is always closed.c) Valve opens automatically when any bleed air switch or pack switch is OFF.d) Valve modulates automatically depending on pneumatic system loads.
    • With the isolation valve inauto if any of the 4 cornerswitches are off theisolation valve will openThe APU bleed air switch doesnot affect the isolation valve
    • How many pneumatic duct pressure sensors are there?
    • How many pneumatic duct pressure sensors are there?2. One left duct andone right duct.
    • What is the power source for the pneumatic duct pressure gage?
    • What is the power source for the pneumatic duct pressure gage?AC Transfer bus 2..
    • What is indicated by the bleed trip off light?
    • What is indicated by the bleed trip off light?BLEED TRIP OFF LightIlluminated (amber) – excessive engine bleed airtemperature (254 C)or pressure. (220 PSI in press regulator)• related engine bleed air valve closes automatically• requires reset.
    • Wing-Body OverheatA wing-body overheat condition is caused by ableed air duct leak. It is sensed by overheatsensors. The wing and body overheat detectionsystem uses sensing elements adjacent to thepneumatic ducts. It monitors the pneumaticdistribution system ducts for overheat conditions.When the system detects an overheat condition,the WING-BODY OVERHEAT lights illuminate.
    • Wing-Body OverheatThe Left Wing –Body Overheat light has sensors inthe;Left engine pylon.Left wing leading edge.Left hand air-conditioning bay .The Keel beam.Along the APU bleed duct.Note; The keel beam is the strong structuralmember which crosses the centre of the mainwheel well to provide structural strength. It isbetween the main wheels when retracted.
    • Wing-Body OverheatThe Right Wing –Body Overheat light has sensorsin the;Right engine pylon.Right wing leading edge.Right hand air-conditioning bay .
    • Wing–Body Overheat (OVHT) TEST SwitchPush –• tests wing–body overheat detector circuits• illuminates both WING–BODY OVERHEAT lights.Wing–Body Overheat Test SP 2Wing–body OVHT TEST switch .......................PushHold for a minimum of 5 seconds.Both WING–BODY OVERHEAT lights – illuminatedMASTER CAUTION – illuminatedAIR COND system annunciator – illuminatedWing–body OVHT TEST switch ................. ReleaseBoth WING–BODY OVERHEAT lights – extinguishedMASTER CAUTION lights – extinguishedAIR COND system annunciator – extinguished
    • AIR-CONDITIONING SYSTEMThe air conditioning system provides temperature controlled air by processing bleedair from the engines, APU, or a ground air source in air conditioning packs.Conditioned air from the left pack, upstream of the mix manifold, flows directly to theflight deck. Excess air from the left pack, air from the right pack, and air from therecirculation system is combined in the mix manifold. The mixed air is thendistributed through the left and right sidewall risers to the passenger cabin.Conditioned air for the cabin comes from either the airplane air conditioning systemor a preconditioned ground source. Air from the preconditioned ground source entersthe air conditioning system through the mix manifold.
    • Air Conditioning PackThe flow of bleed air from the main bleed air duct through each air conditioning pack iscontrolled by the respective pack valve. Normally the left pack uses bleed air fromengine No. 1 and the right pack uses bleed air from engine No. 2. A single pack in highflow is capable of maintaining pressurization and acceptable temperatures throughoutthe airplane up to the maximum certified ceiling.The APU is capable of supplying bleed air for two packs on the ground, or one pack inflight. Most external air carts are capable of supplying adequate bleed air for two packoperation. Do not operate more than one pack from one engine.AIR CYCLE COOLING.The Air-conditioning pack uses the principle of energy conversion and surface heatexchangers for its cooling operation. The heart of the system is the Air Cycle Machine(ACM) The ACM is a 3 wheel unit which decreases air temperature, by expansionthrough a turbine. The ACM is a high-speed rotating assembly. It has three sectionsconnected by a common shaft. The Turbine section rapidly expands the air causing alarge drop in temperature. This process is made more efficient by loading the turbinewith a compressor and an impeller fan. The compressor causes a pressure rise andthe impeller fan moves air through the ram air system when the aircraft is stationaryor at low speed.
    • Simplified Air Cycle cooling systemRam Air intakePack Flow Control ValveRam Air ExhaustRam Air impeller fanACMTemperature control valveACM CompressorACM TurbineCold Air Out
    • Air Conditioning Controls and IndicatorsOption 1Option 2
    • Air Conditioning/Bleed Air Controls PanelThe air conditioning/bleed air controls panel givescontrol and indications of the cooling system.Controls and indications of the cooling system:* RAM DOOR FULL OPEN lights (Blue)* L/R PACK switches* PACK lights (Amber)* TRIP RESET button.
    • 737 NG Air Conditioning PackRAM AIR SYSTEM
    • RAM AIR INTAKERAM AIR EXHAUST
    • RAM AIR INTAKE with Deflector door open.Deflector dooropen on theground closed inflightForward Ram Airmodulating door
    • Pack Switch controls flow into the pack.
    • Airflow ControlWith both air conditioning pack switches in AUTOand both packs operating, the packs provide“normal air flow”. However, with one pack notoperating, the other pack automatically switches to“high air flow” in order to maintain the necessaryventilation rate. This automatic switching isinhibited when the airplane is on the ground, orinflight with the flaps extended, to insure adequateengine power for single engine operation.Automatic switching to “high air flow” occurs if bothengine bleed air switches are OFF and the APUbleed air switch is ON, regardless of flap position,air/ground status or number of packs operating.With the air conditioning pack switch in HIGH, thepack provides “high air flow”. Additionally, an “APUhigh air flow” rate is available when the airplane ison the ground, the APU bleed air switch is ON andeither or both pack switches are positioned toHIGH. This mode is designed to provide themaximum airflow when the APU is the only sourceof bleed air.
    • Ram Air modulating panels regulate the flow of ram air typically fully open on the ground.The Deflector door diverts any slush or snow thrown up by the nose wheels.
    • Ram Air SystemThe ram air system provides cooling air for the heat exchangers. Operation of the systemis automatically controlled by the packs through operation of ram air inlet doors. On theground, or during slow flight with the flaps not fully retracted, the ram air inlet doors moveto the full open position for maximum cooling. In normal cruise, the doors modulatebetween open and closed. A RAM DOOR FULL OPEN light illuminates whenever a ramdoor is fully open.Deflector doors are installed forward of the ram air inlet doors to prevent slush ingestionprior to lift off and after touchdown. Deflector doors extend when activated electrically bythe air–ground safety sensor.
    • Cooling CycleThe flow through the cooling cycle starts with bleed air passing through the primary heatexchanger for cooling. The air then flows to the air cycle machine compressor. The air thenpasses through the secondary heat exchanger where the heat from compression isremoved. The air then passes through 2 more heat exchangers which lower its temperatureenough to produce condensation. This is followed by a water separator which removesmoisture. The moisture is ejected into the ram air duct and overboard. The air then passesthrough the re-heater this raises the temperature of the now dry air and removes heat fromthe air before the condenser. After the re-heater the air enters the turbine of the ACM whereit rapidly expands while driving the compressor and ram air fan. This produces very cold air.The processed cold air is then combined with hot air. The conditioned air flows into the mixmanifold and distribution system.Overheat protection is provided by temperature sensors located in the cooling cycle. Anoverheat condition causes the pack valve to close and the PACK TRIP OFF light toilluminate.
    • Air Mix ValvesThe two air mix valves for each pack control hot and cold air according to the setting of theCONT CABIN or PASS CABIN temperature selector. Air that flows through the cold air mixvalve is processed through a cooling cycle and then combined with hot air flowing from thehot air mix valve.In the automatic temperature mode, the air mix valves are operated by the automatictemperature controller. The automatic temperature controller uses inputs from therespective temperature selector and cabin temperature sensor. The automatic temperaturecontroller is bypassed when the temperature selector is positioned to OFF.Anytime the pack valve closes, the air mix valves are driven to the full cold positionautomatically. This aids start up of the cooling cycle and prevents nuisance hot air tripswhen the pack is first turned on.
    • Zone Temperature ControlThere are three zones: flight deck, forward cabin and aft cabin. Desired zone temperatureis set by adjusting the individual Temperature Selectors. The selector range isapproximately 18°C (65°F) to 30°C (85°F).The packs produce an air temperature that satisfies the zone which requires the mostcooling. Zone temperature is controlled by introducing the proper amount of trim air to thezone supply ducts. The quantity of trim air is regulated by individual trim air modulatingvalves.During single pack operation with the TRIM AIR selected ON, zone temperature iscontrolled the same as during two pack operation. During single pack operation with theTRIM AIR selected OFF, the pack attempts to produce an air temperature to satisfy theaverage temperature demands of all three zones.If air in a zone supply duct overheats, the associated amber ZONE TEMP lightilluminates, and the associated trim air modulating valve closes. The trim air modulatingvalve may be reopened after the duct has cooled by pushing the TRIP RESET Switch.
    • Temperature ControlZone Temperature sensors
    • Temperature ControlMaster Trim Air ValveZone Trim Air Valves
    • Pack/Zone Temperature ControllersThere are two pack/zone temperature controllers. They monitor system parametersand control the air conditioning temperatures for the three air conditioning zones.The pack/zone temperature controllers are part of a redundant, fault tolerantcontrol system. The system reconfigures to give optimum performance when thereare faults. The controllers process inputs from:* Zone temperature selectors* Zone cabin temperature sensors* Zone duct temperature sensors* Pack temperature sensors* Mix manifold sensors.The controllers modulate these valves in response to temperature controlrequirements:* Pack temperature control valves (normal and standby)* Zone trim air modulating valves.
    • Zone Temperature Control ModesThe left electronic controller controls the aft cabin zone and provides backup controlfor the flight deck. The right controller controls the forward cabin zone and providesprimary control for the flight deck.Failure of the primary flight deck temperature control will cause an automatic switch tothe back up control and will illuminate the CONT CAB amber ZONE TEMP light uponMaster Caution Recall. Failure of both the primary and standby controls will illuminatethe lights automatically.Failure of the forward or aft cabin temperature control will cause the associated trimair modulating valve to close. The Temperature Selectors operate normally, but theTemperature Selector settings of the two passenger cabin zones will be averaged.The amber ZONE TEMP light will illuminate upon Master Caution Recall to indicatefailure of the associated zone control.
    • Unbalanced Pack Temperature Control ModeAny failure affecting the supply of trim air will cause the temperature control systemto control both packs independently. If flight deck trim air is lost, the left pack willprovide conditioned air to the flight deck at the selected temperature and the rightpack will satisfy the demand of the passenger zone which requires the most cooling.If a passenger cabin zone trim air, or all trim air is lost, the forward and aft zonetemperature demands will be averaged for control of the right pack. If any individualzone is switched OFF, the Temperature Selector setting will be ignored by thetemperature control system.
    • Standby Pack Average TemperatureIf all zone controls and primary pack controls fail, the standby pack controls commandthe packs to produce air temperatures which will satisfy the average temperaturedemand of the two cabin zones. The trim air modulating valves will close. The flightdeck zone Temperature Selector will have no effect on the standby pack controls.Fixed Cabin TemperatureIf all Temperature Selectors are positioned OFF, the pack controls will cause the leftpack to maintain a fixed temperature of 24°C (75°F) and the right pack to maintain18°C (65°F) as measured at the pack temperature sensor.
    • Air ConditioningDistributionConditioned air is collected inthe mix manifold. Thetemperature of the air isdirectly related to the settingof the Temperature Selectors.Overheat detection isprovided by temperaturesensors located downstreamof the packs and the mixmanifold. An overheatcondition causes theappropriate trim airmodulating valve to close andthe ZONE TEMP light toilluminate.
    • Flight DeckSince the flight deck requires only a fraction of the air supply provided by the left pack,most of the left pack output is routed to the mix manifold. Conditioned air for the flightdeck branches into several risers which end at the floor, ceiling and foot level outlets.Air diffusers on the floor under each seat deliver continuous air flow as long as themanifold is pressurized.Overhead diffusers are located on the flight deck ceiling, above and aft of the No. 3windows. Each of these outlets can be opened or closed as desired by turning aslotted adjusting screw.There is also a dual purpose valve behind the rudder pedal of each pilot. These valvesprovide air for warming the pilots feet and for defogging the inside of the No. 1windshields. Each valve is controlled by knobs located on the Captains and FirstOfficers panels.Foot heat andDe-fogcontrols
    • Passenger CabinThe passenger cabin airsupply distribution systemconsists of the mix manifold,sidewall risers, and anoverhead distribution duct.Sidewall risers go up the rightand left wall of the passengercabin to supply air to theoverhead distribution duct.The overhead distributionduct routes conditioned air tothe passenger cabin. Itextends from the forward tothe aft end of the ceilingalong the airplane centerlineand also supplies the sidewalldiffusers.
    • MIX MANIFOLDLeft and Right riser ductsOverhead Distribution ducts
    • MIX MANIFOLDLeft and Right riser ductsRecirculation FanThe recirculation fan system reduces the air conditioning system pack load and theengine bleed air demand. Air from the passenger cabin and electrical equipment bayis drawn to the forward cargo bay where it is filtered and recirculated to the mixmanifold. The fan is driven by an AC motor. The fan operates with the recirculationfan switch in AUTO except with both packs on and one or both in HIGH.Recirculation Fans
    • Temperature SensorsRecirculation fans.
    • Conditioned Air Source ConnectionA ground air conditioning source may be connected tothe mix manifold to distribute preconditioned airthroughout the airplane.Ground conditioned airconnection
    • Equipment CoolingThe equipment cooling system cools electronic equipment in the flight deck and theE & E bay.The equipment cooling system consists of a supply duct and an exhaust duct. Eachduct has a normal fan and an alternate fan. The supply duct supplies cool air to theflight deck displays and electronic equipment in the E & E bay. The exhaust ductcollects and discards warm air from the flight deck displays, the overhead and aftelectronic panels, circuit breaker panels in the flight deck, and electronic equipmentin the E & E bay.Loss of airflow due to failure of an equipment cooling fan results in illumination of therelated equipment cooling OFF light. Selecting the alternate fan should restoreairflow and extinguish the OFF light within approximately 5 seconds.If an over temperature occurs on the ground, alerting is provided through the groundcrew call horn in the nose wheel well, which will sound continually.
    • FLOW SENSORNo flow from selectedfan NORM or ALTNOFF light illuminated
    • Normal exhaust fan failure low airflow detected. OFF light illuminates
    • Selecting the Alternate Exhaust fan re-establishes airflow andthe OFF light should extinguish within about 5 seconds.
    • The overboard exhaust valve lets exhaust air go overboard when the airplane is on theground. In flight the exhaust air adds to the heat in the forward cargo compartment.A check valve isolates the exhaust air from the cargo compartment when the airplane isin the air and the overboard exhaust valve is open..
    • SMOKE OVERRIDE MODEWhen the aircrew carry out the forward cargo fire checklist they turn off therecirculation fans and select high flow for the packs. This puts the equipmentcooling system into smoke override mode. The overboard exhaust valve opens anda check valve prevents air from the forward cargo area from being vented.
    • Cabin PressurisationCabin pressurization is controlled during all phases of airplane operation by the cabinpressure control system. The cabin pressure control system includes two identicalautomatic controllers available by selecting AUTO or ALTN and a manual (MAN) pilot–controlled mode.The system uses bleed air supplied to and distributed by the air conditioning system.Pressurization and ventilation are controlled by modulating the outflow valve and theoverboard exhaust valve. The overboard exhaust valve is open on the ground andcloses when cabin differential pressure reaches 1 PSI except during smoke overridemode.
    • AUTO FAIL LightIlluminated (amber) – automaticpressurization system failure detected:• indicates a single controller failure whenALTN light is also illuminated• indicates a dual controller failure whenilluminated alone.
    • OFF Schedule (SCHED) DESCENT LightIlluminated (amber) – airplane descendedbefore reaching the planned cruise altitudeset in the FLT ALT indicator.
    • Alternate (ALTN) LightIlluminated (green) – pressurization systemoperating in the alternate automatic mode:• Illumination of both ALTN and AUTO FAILlights indicates a single controller failure andautomatic transfer to ALTN mode• pressurization mode selector in ALTNposition.
    • MANUAL LightIlluminated (green) – pressurization systemoperating in the manual mode.Manual mode must be selected to illuminatethis light.
    • Flight Altitude SelectorRotate – set planned cruise altitude.(-1,000ft. to 42,000 ft. in 500 ft. increments).
    • Landing Altitude SelectorRotate – select planned landing fieldaltitude. (-1,000 ft. to 14,000 ft. in 50 ft.increments).
    • Outflow VALVE Position Indicator• indicates position of outflow valve• operates in all modes.
    • Cabin Altitude Panel
    • CABIN Altimeter (ALT)/Differential Pressure(DIFF PRESS)IndicatorInner Scale – indicates cabin altitude in feet.Outer Scale – indicates differential pressurebetween cabin and ambient in psi.
    • CABIN Rate of CLIMB IndicatorIndicates cabin rate of climb or descent in feetper minute.
    • Altitude (ALT) HORN CUTOUT SwitchPush –• cuts out intermittent cabin altitude warninghorn• altitude warning horn sounds when cabinreaches 10,000 feet altitude.
    • High Altitude Landing Switch (OPTION)ON (white) – reprograms initiation of cabinaltitude warning annunciation from 10,000 to14,000 feet.Off – (ON not visible)• reprograms cabin pressurization from highaltitude to normal operation• extinguishes INOP lightHigh Altitude Landing INOP LightIlluminated (amber) – indicates high altitudelanding system fault.
    • Pressure Relief ValvesTwo pressure relief valves provide safety pressure relief by limiting the differentialpressure to a maximum of 9.1 psi. A negative relief valve prevents externalatmospheric pressure from exceeding internal cabin pressure.Outflow valve Openon the ground untilT/O thrust set.Right rear door
    • Cabin Pressure ControllerCabin altitude is normally rate–controlled by the cabin pressure controller up to a cabinaltitude of 8,000 feet at the airplane maximum certified ceiling of 41,000 feet.The cabin pressure controller controls cabin pressure in the following modes:• AUTO – Automatic pressurization control; the normal mode of operation. Uses DCmotor. (28 V DC BUS 1)• ALTN – Automatic pressurization control; the alternate mode ofoperation. Uses DC motor. (28 V DC BUS 2)• MAN – Manual control of the system using DC motor. (28 V DC Battery BUS)The air data inertial reference units (ADIRUs) provides ambient static pressure,barometric corrected altitude, non corrected altitude and calibrated airspeed to bothautomatic controllers. The ADIRUs receive barometric corrections from the Captain’sand First Officer’s BARO reference selectors.The automatic controllers also receive thrust lever position from both stall managementcomputers and signals from the air/ground sensors.
    • Pressurization OutflowCabin air outflow is controlled by the outflow valve and the overboard exhaust valve. Asmall amount is also exhausted through toilet and galley vents, miscellaneous fixedvents, and by seal leakage.Outflow ValveThe outflow valve is the overboard exhaust exit for the majority of the air circulatedthrough the passenger cabin. Passenger cabin air is drawn through foot level grills,down around the aft cargo compartment, where it provides heating, and is dischargedoverboard through the outflow valve.
    • Auto Mode OperationThe AUTO system consists of two identical controllers, with one controller alternately sequencedas the primary operational controller for each new flight. The other automatic controller isimmediately available as a backup.In the AUTO or ALTN mode, the pressurization control panel is used to pre-set two altitudes intothe auto controllers:• FLT ALT (flight or cruise altitude).• LAND ALT (landing or destination airport altitude).Takeoff airport altitude (actually cabin altitude) is fed into the auto controllers at all times when onthe ground.The air/ground safety sensor signals whether the airplane is on the ground or in the air. On theground and at lower power settings, the cabin is depressurized by driving the outflow valve to thefull open position.The cabin begins to pressurize on the ground at higher power settings. The controller modulatesthe outflow valve toward close, slightly pressurizing the cabin. (Approximately 0.1 psi 200 feetbelow field elevation) (Ground phase cabin rate is maximum of 350 FPM) This groundpressurization of the cabin makes the transition to pressurized flight more gradual for thepassengers and crew, and also gives the system better response to ground effect pressurechanges during takeoff.
    • In the air, the auto controller maintains a proportional pressure differential between airplane andcabin altitude. By increasing the altitude at a rate proportional to the airplane climb rate, cabinaltitude change is held to the minimum rate required. ( Maximum cabin climb rate 600 to 750Sea Level Feet Per Minute (SLFPM) (different aircraft variations) )An amber OFF SCHED DESCENT light illuminates if the airplane begins to descend withouthaving reached the preset cruise altitude; for example, a flight aborted in climb and returning tothe takeoff airport. The controller programs the cabin to land at the takeoff field elevation withoutfurther pilot inputs. If the FLT ALT indicator is changed, the automatic abort capability to theoriginal takeoff field elevation is lost.The cruise mode is activated when the airplane outside pressure is within 0.25 psi of theselected FLT ALT. (Approximately 1,500 feet) During cruise the controller maintains the lowestpossible cabin altitude based on the differential pressure limits.In certain circumstances the selected LAND ALT may exceed the target cabin altitudedetermined by the differential pressure limits. In these cases, the controller will maintain a cabinaltitude slightly below the selected LAND ALT. Deviations from flight altitude can cause thepressure differential to vary as the controller modulates the outflow valve to maintain a constantcabin altitude.The descent mode is activated when the airplane descends 0.25 psi below the selected FLTALT. (approximately 1,500 feet) (The maximum cabin rate in descent is 350 SLFPM) The cabinbegins a proportional descent to slightly below the selected LAND ALT. The controller programsthe cabin to land slightly pressurized (0.15 psi Approximately 250 feet below field elevation) sothat rapid changes in altitude during approach result in minimum cabin pressure changes.While taxiing in, the controller drives the outflow valve slowly to the full open positiondepressurizing the cabin.
    • An amber AUTO FAIL light illuminates if any of thefollowing conditions occurs:• Loss of DC power• Controller fault• Outflow valve control fault• Excessive differential pressure (> 8.75 psi)*• Excessive rate of cabin pressure change (±2000sea level feet/minute)*• High cabin altitude (above 15,800 feet).**If controller is not responding properlyWith illumination of the AUTO FAIL light, thepressure control automatically transfers to the otherauto controller (ALTN mode).Moving the pressurization mode selector to theALTN position extinguishes the AUTO FAIL light,however the ALTN light remains illuminated toindicate single channel operation.
    • High Altitude Landing (OPTION)The High Altitude Landing System is engaged by selecting the high altitude landingswitch ON. This switch is located on the Cabin Altitude Panel. When the high altitudelanding system is engaged and the actual landing altitude is set, the controller brings thecabin altitude to the landing airport elevation when the descent mode is activated. Upondeparture from a high altitude airport, the system returns to normal operation as thecabin altitude descends through 8,500 feet.
    • Manual Mode OperationA green MANUAL Light illuminates with the pressurization mode selector in the MANposition.Manual control of the cabin altitude is used if both the AUTO and ALTN modes areinoperative. In the MAN mode, the outflow valve position switch is used to modulatethe outflow valve by monitoring the cabin altitude panel and valve position on theoutflow valve position indicator. A separate DC motor, powered by the DC standbysystem, (Battery Bus) drives the outflow valve at a slower rate than the automaticmodes. Outflow valve full range of motion takes up to 20 seconds.
    • CABIN ALTITUDE/TAKEOFF CONFIG WARNING LIGHTS.Aircraft modification and installed positionmay vary.
    • Cabin Altitude Warning LightIlluminated (red) –• illuminates when cabin altitude exceeds 10,000 feet• activation is simultaneous with aural warning intermittent horn for CABINALTITUDE alert• extinguishes when cabin altitude descends below 10,000 feet.Note: Operation of the High Altitude Landing Switch changes the altitude at whichthe cabin altitude warning light illuminates and extinguish.Takeoff Configuration Warning LightIlluminated (red) –• activates on the ground as the throttles are advanced if the airplane is notconfigured correctly for takeoff• activation is simultaneous with aural warning intermittent horn for TAKEOFFCONFIGURATION alert.Note: The intermittent warning horn is the same for both Cabin Alt and T/O Config.Not all aircraft are fitted with the lights to differentiate. Takeoff Config happens onthe ground at application of T/O power. Cabin Alt happens at 10,000 feet!
    • Altitude (ALT) HORN CUTOUT SwitchPush –• cuts out intermittent cabin altitude warninghorn• altitude warning horn sounds when cabinreaches 10,000 feet altitude.Note: Cutout switch also cancels thecabin Altitude warning light if installed.
    • LIMITATIONS PressurizationThe maximum cabin differential pressure (relief valves) is 9.1 psi.Non–AFM Operational InformationNote: The following items are not AFM limitations, but are provided for flight crewinformation.With engine bleed air switches ON, do not operate the air conditioning packs inHIGH for takeoff, approach or landing.Note: The fire protection Non-Normal procedures takes precedence over thestatement regarding no air conditioning pack in HIGH during takeoff, approach, orlanding. The CARGO FIRE and SMOKE/ FUMES REMOVAL checklists require theOperating PACK switch(es) HIGH. Switch(es) need to be placed in HIGH in order toincrease ventilation for smoke removal.
    • Recirculation fans.How are the recirculation fans powered?
    • Recirculation fans.How are the recirculation fans powered?
    • Recirculation fans.What is the purpose of the Recirculation fans?
    • MIX MANIFOLDLeft and Right riser ductsRecirculation FanThe recirculation fan system reduces the air conditioning system pack load and theengine bleed air demand. Air from the passenger cabin and electrical equipment bayis drawn to the forward cargo bay where it is filtered and recirculated to the mixmanifold. The fan is driven by an AC motor. The fan operates with the recirculationfan switch in AUTO except with both packs on and one or both in HIGH.Recirculation Fans
    • The APU can power which PACKS;On the ground?In Flight?
    • The APU can power which PACKS;On the ground?In Flight?The APU is capable of supplying bleed air for two packs on the ground, or onepack in flight. Most external air carts are capable of supplying adequate bleed airfor two pack operation. Do not operate more than one pack from one engine.
    • Failure of the forward cabin temperature control would have what effect?a) The cabin temperature standby controller will control pack temperature.b) The pack must be selected to OFF.c) The Trim air modulating valve for the forward cabin will close and the temperatureselector settings for the 2 passenger cabin zones will be averaged.d) Pushing the pack trip reset switch will change the pack control to manual allowingmanual temperature control.
    • Failure of the forward cabin temperature control would have what effect?a) The cabin temperature standby controller will control pack temperature.b) The pack must be selected to OFF.c) The Trim air modulating valve for the forward cabin will close and thetemperature selector settings for the 2 passenger cabin zones will be averaged.d) Pushing the pack trip reset switch will change the pack control to manual allowingmanual temperature control.Failure of the forward or aft cabin temperature control will cause the associated trim airmodulating valve to close. The Temperature Selectors operate normally, but theTemperature Selector settings of the two passenger cabin zones will be averaged. Theamber ZONE TEMP light will illuminate upon Master Caution Recall to indicate failure ofthe associated zone control.
    • The ZONE TEMP light illuminates for the control cabin:a) Indicates that a duct overheat has occurred and the left pack valve has closed.b) Indicates that the control cabin primary and secondary controllers have failed.c) Indicates that the left pack out let temperature is too high.d) Indicates that the control cabin temperature is warmer than commanded.
    • The ZONE TEMP light illuminates for the control cabin:a) Indicates that a duct overheat has occurred and the left pack valve has closed.b) Indicates that the control cabin primary and secondary controllers have failed. *c) Indicates that the left pack out let temperature is too high.d) Indicates that the control cabin temperature is warmer than commanded.Failure of the primary flight deck temperature control will cause an automatic switch to the backup control and will illuminate the CONT CAB amber ZONE TEMP light upon Master CautionRecall. Failure of both the primary and standby controls will illuminate the lights automatically.
    • What is the primary source of air for the cockpit?a) The right pack.b) The left packc) The mix manifold.d) The recirculation system.
    • What is the primary source of air for the cockpit?a) The right pack.b) The left packc) The mix manifold.d) The recirculation system.
    • The ZONE TEMP light for the FWD CAB illuminates:a) The associated trim air valve is closed.b) The associated zone temperature controller has failed.c) Both the primary and secondary zone temperature controllers have failed.d) Both packs should be selected to a lower temperature to reduce duct temperature.
    • The ZONE TEMP light for the FWD CAB illuminates:a) The associated trim air valve is closed.b) The associated zone temperature controller has failed.c) Both the primary and secondary zone temperature controllers have failed.d) Both packs should be selected to a lower temperature to reduce duct temperature.Overheat detection is provided by temperature sensors located downstream of the packsand the mix manifold. An overheat condition causes the appropriate trim air modulatingvalve to close and the ZONE TEMP light to illuminate.
    • How do you reset a duct overheat condition?
    • TRIP RESET SwitchPush (if fault condition is corrected) –• resets BLEED TRIP OFF, PACK TRIP OFF andZONE TEMP lights• related engine bleed valve opens, or related packvalve opens, or related air mix valve opens• lights remain illuminated until reset.
    • Which positions does the pressurisation mode selector have?a) ON and OFF.b) AUTO, ALTN, MAN.c) AUTO, ALTN, MAN, OFF.d) AUTO, MAN, STBY.
    • Which positions does the pressurisation mode selector have?a) ON and OFF.b) AUTO, ALTN, MAN.c) AUTO, ALTN, MAN, OFF.d) AUTO, MAN, STBY.
    • Just prior to takeoff the cabin altitude will be:a) The same as the airfield elevation.b) 200 feet below the airfield elevation.c) 300 feet below the airfield elevation.d) 300 feet above airfield elevation.
    • Just prior to takeoff the cabin altitude will be:a) The same as the airfield elevation.b) 200 feet below the airfield elevation.c) 300 feet below the airfield elevation.d) 300 feet above airfield elevation.The cabin begins to pressurize on the ground at higher power settings. The controllermodulates the outflow valve toward close, slightly pressurizing the cabin. (Approximately0.1 psi 200 feet below field elevation) (Ground phase cabin rate is maximum of 350 FPM)This ground pressurization of the cabin makes the transition to pressurized flight moregradual for the passengers and crew, and also gives the system better response to groundeffect pressure changes during takeoff.
    • What is indicated if the pressurisation system is operating in the manual mode?
    • What is indicated if the pressurisation system is operating in the manual mode?
    • Manual Mode OperationA green MANUAL Light illuminates with the pressurization mode selector in the MANposition.Manual control of the cabin altitude is used if both the AUTO and ALTN modes areinoperative. In the MAN mode, the outflow valve position switch is used to modulatethe outflow valve by monitoring the cabin altitude panel and valve position on theoutflow valve position indicator. A separate DC motor, powered by the DC standbysystem, (Battery Bus) drives the outflow valve at a slower rate than the automaticmodes. Outflow valve full range of motion takes up to 20 seconds.
    • How many outflow valves are utilised by the pressurisation system?
    • How many outflow valves are utilised by the pressurisation system?One in the RIGHT rear Fuselage.
    • At what pressure do the pressurisation relief valves open?
    • At what pressure do the pressurisation relief valves open?9.1 PSI
    • At what pressure do the pressurisation relief valves open?9.1 PSIThe maximum cabin differential pressure is?
    • At what pressure do the pressurisation relief valves open?9.1 PSIThe maximum cabin differential pressure is?
    • •The END of AUTO FLIGHT Part 1The END of AIR SYSTEMS.Now take the test at www.theorycentre.comFor more information info@theorycentre.com