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B757 air systems
B757 air systems
B757 air systems
B757 air systems
B757 air systems
B757 air systems
B757 air systems
B757 air systems
B757 air systems
B757 air systems
B757 air systems
B757 air systems
B757 air systems
B757 air systems
B757 air systems
B757 air systems
B757 air systems
B757 air systems
B757 air systems
B757 air systems
B757 air systems
B757 air systems
B757 air systems
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B757 air systems

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  • 1.   B757                Air Systems    DO NOT USE FOR FLIGHT 
  • 2. Boeing B757 - Systems Summary [Air Systems]2.20 Air Systems-Air Conditioning System DescriptionAir Conditioning IntroductionThe air conditioning system supplies conditioned bleed air and recirculated cabinair at a controlled temperature throughout the airplane.The system supplies conditioned air to the flight deck shoulder heaters.The system supplies ventilation for the cabin: • lavatories • galleys • individual passenger seat gaspers.Pack control, zone temperature control, cabin air recirculation, fault detection, andoverheat protection are all automatic.The airplane is divided into three temperature zones: the flight deck and two cabinzones.Air Conditioning PacksTwo identical air conditioning packs cool bleed air from the engines, APU, or highpressure air from a ground source. Bleed air is precooled before entering the pack.The packs are controlled by two identical pack controllers. Pack output isautomatically increased during high pack demand periods (to compensate for afailed pack or recirculation fan), or limited during high bleed air demand periods(such as with an engine inoperative).Air Conditioning Automatic ModeWith the pack selector in the AUTO position, pack output temperature isdetermined by the cabin temperature controller. Zone temperature is then satisfiedby the zone temperature controllers using trim air.Air Conditioning Standby ModeWith the pack selector in the standby mode, pack output temperature is determinedby the position of the pack selector: • N (normal) – constant, moderate temperature • C (cool) – full cold • W (warm) – full warm. Page 2
  • 3. Boeing B757 - Systems Summary [Air Systems]Ground Conditioned Air OperationWhen a ground source of conditioned air is available, it may be used to supplyconditioned air directly to the cabin distribution system, eliminating the need forpack operation.Pack Non–Normal OperationPack control, fault detection, and overheat protection are all automatic.The pack INOP light illuminates and the EICAS advisory message L or R PACKTEMP displays for all pack control system faults and overheats.When an automatic control system fault or a pack outlet overheat is detected, thepack continues to operate in an uncontrolled, degraded condition, requiring crewinteraction.The pack valve closes and the pack is shut down automatically when an internalpack overheat is detected. The PACK OFF light illuminates and the EICASadvisory message L or R PACK OFF displays in addition to the PACK TEMPindications.If the INOP light remains illuminated after selecting STBY, the fault is a packoverheat. After the pack has cooled, an attempt to restore pack operation may bemade by pushing the PACK RESET switch.Air DistributionConditioned air from the packs flows into a mix manifold where it mixes with airfrom two recirculation fans. Recirculation fans maintain overall cabin aircirculation while allowing a reduction of cabin air ventilation, permitting thepacks to be operated at a reduced flow. The mixed air is then ducted into the cabin.The flight deck receives 100% fresh conditioned air from the left pack only and ismaintained at a slightly higher pressure than the passenger cabin. This preventssmoke from entering the flight deck. When the left pack is inoperative, the flightdeck receives air from the mix manifold.The left recirculation fan draws air through the forward E/E system and returns itto the mix manifold. Air that moves from the cabin to the lower deck eitherexhausts overboard through the outflow valve or is drawn into the rightrecirculation fan and returns to the mix manifold.The right recirculation fan can be turned off for several minutes to provide a morerapid exchange of air. The left recirculation fan should not be turned off as thiscauses the overboard exhaust valve to latch open. Maintenance action is requiredto reset the OVBD EX VAL OPEN status message. Page 3
  • 4. Boeing B757 - Systems Summary [Air Systems]The recirculation fan INOP light illuminates and the EICAS advisory message Lor R RECIR FAN displays whenever a recirculation fan fails or the switch is off.A slight increase in fuel consumption occurs for each fan that is off.Temperature ControlThe airplane is divided into three temperature control compartments: • flight deck • forward cabin • aft cabin.The pack controllers regulate the pack output air temperature to satisfy thetemperature requirement of the compartment requiring the coolest air. Hot trim airfrom the bleed air system is added through trim air valves to control thetemperature in each of the other compartments. Each temperature controlcompartment has an associated temperature control.A compartment INOP light illuminates and the EICAS advisory message FLTDECK TEMP, FWD CABIN TEMP, or AFT CABIN TEMP displays to indicate: • zone temperature controller failure • zone selector is in the OFF position • trim air switch is OFFTemperature Control With Loss of Trim Air SystemDuring operation with the trim air system off, the packs attempt to maintain allcompartments at an average temperature. The trim air OFF light illuminates andthe EICAS advisory message TRIM AIR displays when a TRIM AIR switch is off.Shoulder and Foot HeatersFlight crew shoulder heat is provided by electric heaters in the ducts that supplyconditioned air to the side windows. Foot heat is provided by electric heatingelements only, with no airflow. The high setting for both shoulder and foot heat isavailable in flight only.Forward Equipment Cooling SystemForward equipment cooling supplies cooling air to the equipment in the forwardequipment racks and the flight deck avionics. The system has a supply fan thatdraws cooling air from the cabin and forces it through the equipment racks andavionics. The air is then exhausted into the air conditioning mix manifold by theleft recirculation fan. If the differential pressure is low, the overboard exhaustvalve automatically opens and most of the air is exhausted overboard. Page 4
  • 5. Boeing B757 - Systems Summary [Air Systems]An auxiliary fan automatically operates to provide cooling for essential avionicsand electrical equipment if the alternate supply fan has been selected but bothsupply fans are inoperative. However, non–essential avionics and electricalequipment are subject to imminent failure. The auxiliary fan can be powered bythe hydraulic driven generator.On the ground, the OVHT light illuminates, the EQPT OVHT message displaysand the ground crew call horn sounds if insufficient cooling airflow is detected.Equipment SmokeThe equipment cooling SMOKE light illuminates and the EICAS advisorymessage FWD EQPT SMOKE displays when smoke is detected in the equipmentcooling system.The following items, which may be observed in the flight deck, occurautomatically to help evacuate the smoke: • one or both recirculation fans turn off • one or both air conditioning packs switch to high flow • the overboard exhaust valve is latched open.When smoke is no longer detected, the recirculation fans and air conditioningpacks automatically return to normal operation.Cargo Heat SystemCargo compartment heating and ventilation is completely automatic. There are nocontrols or indicators in the cockpit. Page 5
  • 6. Boeing B757 - Systems Summary [Air Systems]Air Conditioning System Schematic COMPT TEMP INOP INOP INOP FLT DK FWD CAB AFT CAB AUTO AUTO AUTO C W C W C W OFF OFF OFF MIX MANIFOLD RECIRC TRIM AIR L FAN R ON ON ON OFF INOP INOP L PACK R PACK RESET RESET INOP INOP PACK PACK OFF OFF AUTO AUTO OFF N OFF N S S PACK AIR CT CT B B EXHAUST AIR Y Y W W MIX MANIFOLD AIR TRIM AIR PNEUMATIC PNEUMATIC SUPPLY SUPPLY Page 6
  • 7. Boeing B757 - Systems Summary [Air Systems]2.30 Air Systems-Pressurization System DescriptionPressurization IntroductionCabin pressurization is controlled by adjusting the discharge of conditioned cabinair through the outflow valve.Positive pressure relief valves and negative pressure relief doors protect thefuselage against excessive pressure differential.The pressurization system has automatic and manual operating modes.Pressurization System Automatic OperationThe pressurization system is in the automatic mode when the cabin altitude modeselector is set to AUTO 1 or AUTO 2. If the selected auto mode fails, control isautomatically switched to the other auto mode.In the automatic mode, the pressurization system uses ambient pressure data fromthe air data system in conjunction with the selected cabin auto rate, the takeoffaltitude and the indicated landing altitude to calculate the cabin pressurizationschedule.TakeoffFor takeoff, the system supplies a small positive pressurization to cause a smoothcabin altitude transition.ClimbDuring climb, cabin altitude increases on a schedule related to the takeoff fieldelevation, airplane altitude, and the selected auto climb rate limit.If the maximum cabin pressure differential is reached, cabin climb rate becomesa function of airplane climb rate, while maintaining the maximum differentialpressure.CruiseShortly after the airplane levels off, the system enters the cruise mode. The landingaltitude and the scheduled cabin altitude are compared and the higher of these twois selected for the cruise cabin altitude. If necessary, the cabin climbs to the cruisecabin altitude at one–half the auto rate or descends to the cruise cabin altitude atthe auto rate.The cruise cabin altitude does not change for minor altitude variations. Asignificant altitude change causes the system to re–enter the climb mode or toenter the descent mode. Page 7
  • 8. Boeing B757 - Systems Summary [Air Systems]Descent and LandingDuring descent, cabin altitude decreases to slightly below the selected landingaltitude. This ensures that the airplane lands pressurized. Landing altitudebarometric pressure correction comes from the captain’s altimeter.At touchdown, the outflow valve opens to depressurize the airplane.Non–Normal IndicationsIf the cabin altitude climbs above 10,000 feet, the CABIN ALT and CABINALTITUDE lights illuminate and the EICAS warning message CABINALTITUDE displays. The lights extinguish and the EICAS message blanks whenthe cabin altitude descends below 8,500 feet.The AUTO INOP light illuminates and the EICAS caution message CABINAUTO INOP displays when automatic pressurization control fails or when cabinaltitude MODE SELECT is MAN. Manual operation is required if the automaticsystem fails.Only the automatic mode is equipped with an aneroid switch that automaticallycloses the outflow valve when the cabin altitude exceeds 11,000 feet. The manualmode has no auto closure feature.To operate the pressurization system manually: • set the cabin altitude MODE SELECT to MAN • hold the cabin altitude MANUAL control to CLIMB to move the outflow valve toward open and cause the cabin altitude to climb • hold the cabin altitude MANUAL control to DESCEND to move the outflow valve toward closed and cause the cabin altitude to descend. Page 8
  • 9. Boeing B757 - Systems Summary [Air Systems]2.40 Air Systems-Bleed Air System DescriptionBleed Air IntroductionBleed air can be supplied by the engines, APU, or a ground air source.Bleed air is used for: • air conditioning • wing and engine anti–ice • pressurization • hydraulic reservoir • engine start pressurization.Engine Bleed Air SupplyEngine bleed air comes from either the high pressure (HP) or the low pressure(LP) engine compressor sections. LP air is used during high power settingoperations. HP air is used during descent and other low power setting operations.The engine bleed air valves are armed when the engine bleed air switches areselected ON. The valves are pressure actuated and remain closed until enginebleed air pressure is sufficient to cause forward flow. The valves may close whenthe APU is starting either engine. The valves may close when ground pneumaticair is connected or during periods of low engine bleed air demand, such as whenthe air conditioning packs are OFF. The engine bleed air OFF light illuminates andthe EICAS advisory message L or R ENG BLEED OFF displays when the enginebleed air valve is closed.The HI STAGE light illuminates and the EICAS advisory message L or R ENGHI STAGE displays when engine bleed air pressure is excessive and the highpressure bleed air valve automatically locks closed.The engine BLEED light illuminates and the EICAS Caution message L or RENG BLEED VAL displays if the engine bleed air temperature is excessive.APU Bleed Air SupplyAPU bleed air is used primarily during ground operations for air conditioningpack operation and engine starting. In flight, APU bleed air is available up toapproximately 17,000 feet.The check valve in the APU supply line prevents reverse flow of bleed air fromthe duct into the APU.The APU bleed air VALVE light illuminates and the EICAS advisory messageAPU BLEED VAL displays when the APU Bleed Valve position disagrees withthe commanded position. Page 9
  • 10. Boeing B757 - Systems Summary [Air Systems]Ground Pneumatic Air SupplyExternal connectors are provided to connect a ground source of high pressure airdirectly to the bleed air duct.Check valves prevent reverse flow of bleed air from the bleed air duct to theconnectors.Bleed Air Duct SystemThe duct pressure indicator displays the pressure in the left and right bleed airducts.The isolation valve separates the bleed air ducts into isolated segments. Theisolation valve is normally closed except for engine start or single bleed sourceoperation.The isolation VALVE light illuminates and the EICAS advisory message BLEEDISLN VAL displays when the isolation valve position disagrees with thecommanded position.The DUCT LEAK light illuminates and the EICAS caution message L or R BLDDUCT LEAK displays when a high temperature bleed air leak is detected. Page 10
  • 11. Boeing B757 - Systems Summary [Air Systems]Bleed Air System Schematic L PACK R PACK GROUND BLEED AIR GROUND PNEUMATIC PNEUMATIC 60 80 DUCT 40 PRESS PSI 20 0 DUCT DUCT LEAK LEAK BLEED ISOLATION BLEED HI STAGE HI STAGE VALVE L WING ANTI-ICE R WING ANTI-ICE HYDRAULIC HYDRAULIC RESERVOIRS RESERVOIRS L ENG APU R ENG V O A O F L F F V F E ENGINE ENGINE ANTI-ICE APU ANTI-ICE STARTER LP LP STARTER HP HP PANEL FLOW LINES FLOW LINES NOT ON PANEL Page 11
  • 12. Boeing B757 - Systems Summary [Air Systems] L PACK R PACK BLEED AIR GROUND GROUND PNEUMATIC PNEUMATIC 60 80 DUCT 40 PRESS PSI 20 0 DUCT DUCT LEAK LEAK BLEED ISOLATION BLEED HI STAGE HI STAGE VALVE L WING ANTI-ICE R WING ANTI-ICE HYDRAULIC HYDRAULIC RESERVOIRS RESERVOIRS L ENG APU R ENG V O A O F L F F V F E ENGINE APU ENGINE ANTI-ICE ANTI-ICESTARTER LP LP HP HP STARTER PANEL FLOW LINES FLOW LINES NOT ON PANEL Page 12
  • 13. Boeing B757 - Systems Summary [Air Systems]2.50 Air Systems-EICAS MessagesAir Systems EICAS MessagesThe following EICAS messages can be displayed. Message Level Light Aural Condition APU BLEED VAL Advisory VALVE APU bleed valve position disagrees with the commanded position. L BLD DUCT LEAK Caution DUCT Beeper A high temperature bleed R BLD DUCT LEAK LEAK air leak is detected. BLEED ISLN VAL Advisory VALVE Bleed isolation valve position disagrees with the commanded position. CABIN ALTITUDE Warning CABIN Siren Cabin altitude excessive. ALTITUDE, CABIN ALT CABIN AUTO INOP Caution AUTO Beeper Automatic pressurization INOP control has failed or the cabin altitude mode selector is in manual. AFT CABIN TEMP Advisory INOP A fault in the zone FWD CABIN TEMP temperature controller or trim air switch OFF. L ENG BLEED OFF Advisory OFF Engine bleed air valve is R ENG BLEED OFF closed for a system fault. L ENG BLEED VAL Caution BLEED Beeper Engine bleed air R ENG BLEED VAL temperature excessive. L ENG HI STAGE Advisory HI STAGE Engine bleed system R ENG HI STAGE pressure is excessive and the high pressure bleed air valve has automatically locked closed. EQPT OVHT Advisory OVHT Forward equipment cooling system inoperative. Page 13
  • 14. Boeing B757 - Systems Summary [Air Systems] Message Level Light Aural ConditionFWD EQPT SMOKE Advisory SMOKE Smoke detected in the forward equipment cooling ducts.FLT DECK TEMP Advisory INOP Duct overheat, fault in the zone temperature controller, or trim air switch off.L PACK OFF Advisory PACK OFF Pack valve is closed.R PACK OFFL PACK TEMP Advisory INOP Automatic control systemR PACK TEMP fault or overheat.L RECIR FAN Advisory INOP Fan is failed or notR RECIR FAN operating.TRIM AIR Advisory OFF Trim air switch off. Page 14
  • 15. 2.10 Air Systems-Controls andSummary [Air Systems] Boeing B757 - Systems IndicatorsAir Conditioning SystemAir Conditioning Control Panel COMPT TEMP 1 2 INOP INOP INOP FLT DK FWD CAB AFT CAB AUTO AUTO AUTO 3 C W C W C W OFF OFF OFF 4 RECIRC FAN TRIM AIR L R ON ON ON 10 5 OFF INOP INOP L PACK R PACK 11 6 RESET RESET 7 INOP INOP PACK PACK 8 OFF OFF AUTO AUTO OFF N OFF N S S 9 CT CT B B Y Y W W OVERHEAD PANEL 1 Compartment Temperature (COMPT TEMP) Indicators Displays actual temperature sensed in the compartment. 2 Compartment Temperature Inoperative (INOP) Lights Illuminated (amber) – • fault in the zone temperature controller • the Compartment Temperature Control is OFF • the trim air switch is OFF. Page 15
  • 16. Boeing B757 - Systems Summary [Air Systems] 3 Compartment Temperature ControlsAUTO – • provides automatic compartment temperature control • rotating the control toward C (cool) or W (warm) sets the desired temperature between 18 degrees C and 30 degrees C.OFF – • closes the compartment trim air valve • the compartment temperature INOP light illuminates. 4 TRIM AIR SwitchON – the trim air valve is commanded open.Off (ON not visible) – the trim air valve is commanded closed. 5 Trim Air OFF LightIlluminated (amber) – the TRIM AIR switch is off. 6 PACK RESET SwitchesPush – resets an overheated pack if the pack has cooled to a temperature below theoverheat level. 7 Pack Inoperative (INOP) LightsIlluminated (amber) – • the pack is overheated • fault in the automatic control system. 8 PACK OFF LightsIlluminated (amber) – the pack valve is closed. 9 PACK Control SelectorsOFF – closes the pack valve.AUTO – the pack is automatically controlled.STBY– • N (normal) – regulates the pack outlet temperature to a constant, moderate temperature • C (cool) – sets the pack to full cold operation • W (warm) – sets the pack to full warm operation. Page 16
  • 17. Boeing B757 - Systems Summary [Air Systems] 10 Recirculation Fan (RECIRC FAN) Switches • ON – the recirculation fan operates • Off (ON not visible) – the recirculation fan does not operate. 11 Recirculation Fan Inoperative (INOP) LightsIlluminated (amber) – • the recirculation fan is failed or not operating • the RECIRC FAN switch is off.Shoulder and Foot Heaters HEATERS FOOT HI LOW 1 OFF SHOULDER HI LOW 2 OFF LEFT AND RIGHT SIDEWALL 1 FOOT HEATERS Switch • HIGH – the under–floor electric heater operates on high setting (in flight only). • LOW – the under–floor electric heater operates on low setting. • OFF – the under–floor electric heater is not operating. 2 SHOULDER HEATERS Switch • HIGH – the electric heater adds heat at high setting to the conditioned air flowing at shoulder level (in flight only). • LOW – the electric heater adds heat at low setting to the conditioned air flowing at shoulder level. • OFF – the electric heater is not operating (no heat added to the conditioned air flowing at shoulder level.). Page 17
  • 18. Boeing B757 - Systems Summary [Air Systems]Equipment Cooling Panel EQUIP COOLING 1 SMOKE ALTN 2 OVHT 3 OVERHEAD PANEL 1 Equipment Cooling SMOKE LightIlluminated (amber) – smoke is detected in the forward equipment cooling ducts. 2 Alternate (ALTN) Equipment Cooling SwitchALTN – • activates the alternate supply fan • activates the auxiliary fan, if the alternate supply fan fails. 3 Equipment Cooling Overheat (OVHT) LightIlluminated (amber) – • insufficient airflow (on the ground) • the supply fan is inoperative • the alternate supply fan is inoperative. Page 18
  • 19. Boeing B757 - Systems Summary [Air Systems]Pressurization SystemCabin Altitude Controls 1 CABIN ALTITUDE CONTROL VALVE MANUAL AUTO RATE CLIMB OP 2 5 CL MIN MAX DESCEND LDG ALT AUTO INOP 6 3 00340 MODE SELECT AUTO 2 AUTO 1 MAN 4 7 OVERHEAD PANEL 1 Cabin Altitude MANUAL ControlSpring – loaded to center.Controls cabin outflow valve position with the Cabin Altitude Mode Selector inmanual (MAN) mode.CLIMB – moves outflow valve toward open.DESCEND – moves outflow valve toward closed. 2 Outflow VALVE Position IndicatorOP – Open.CL – Closed 3 Landing Altitude (LDG ALT) IndicatorFeet.Displays selected landing altitude. 4 Landing Altitude (LDG ALT) SelectorRotate – sets landing altitude indicator. Page 19
  • 20. Boeing B757 - Systems Summary [Air Systems] 5 Cabin Altitude AUTO RATE ControlRotate – • sets limit for cabin altitude rate of climb or descent during auto control • index mark establishes approximately 500 fpm climb and 300 fpm descent. 6 AUTO Inoperative (INOP) LightIlluminated (amber) – • AUTO 1 and AUTO 2 cabin altitude control functions are inoperative • MAN mode is selected. 7 Cabin Altitude MODE SELECTORAuto 1 – • activates Auto 1 cabin altitude control for automatic operation • outflow valve positioned automatically.Auto 2 – • activates Auto 2 cabin altitude control for automatic operation • outflow valve positioned automatically.MAN (Manual) – • outflow valve position is controlled by the cabin altitude MANUAL control • AUTO INOP light illuminates.Cabin Altitude Indicators CABIN 0 10 0 25 2 1 2 2 20 4 0 3 1 4 15 8 6 1 2 6 10 8 FT X FPM X DIFF PSI ALT 1000 RATE 1000 2 CABIN ALTITUDE 4 PRESS DIFF LIMIT: TO/LDG 5 .125 PSI OVERHEAD PANEL Page 20
  • 21. Boeing B757 - Systems Summary [Air Systems] 1 Cabin Differential Pressure IndicatorPounds per square inch (psi). 2 Cabin AltitudeFeet x 1,000. 3 Cabin Altitude RateFeet per minute (fpm x 1,000). 4 Cabin Altitude LightIlluminated (red) – • cabin altitude exceeds 10,000 feet • extinguishes when cabin altitude descends below 8,500 feet. 5 Pressure Differential (PRESS DIFF) Limit PlacardSpecifies differential pressure limitation for takeoff and landing.Cabin Altitude (CABIN ALT) Light CABIN ALT 1 CENTER FORWARD PANEL 1 Cabin Altitude LightIlluminated (red) – • cabin altitude exceeds 10,000 feet • extinguishes when cabin altitude descends below 8,500 feet. Page 21
  • 22. Boeing B757 - Systems Summary [Air Systems]Bleed Air SystemBleed Air Control Panel BLEED AIR 60 80 DUCT 1 40 PRESS PSI 20 0 DUCT DUCT LEAK LEAK 2 BLEED ISOLATION BLEED HI STAGE HI STAGE 3 VALVE L ENG APU R ENG V O A O 4 F L V F F F E 5 OVERHEAD PANEL 1 Duct Pressure (DUCT PRESS) IndicatorsPounds per square inch (psi). 2 ISOLATION SwitchOn (bar in view) – commands isolation valve to open.Off (bar not visible) – commands isolation valve to close. 3 Isolation VALVE LightIlluminated (amber) – isolation valve position disagrees with commandedposition. 4 Engine (ENG) Bleed Air SwitchesOn (bar in view) – the engine bleed air valve opens when engine bleed air isavailable.Off (bar not visible) – valve is manually commanded closed. Page 22 Copyright © The Boeing Company. See title page for details.2.10.8 D632N001-200
  • 23. Boeing B757 - Systems Summary [Air Systems] 5 Engine Bleed Air OFF LightsIlluminated (amber) – engine bleed air valve is closed: • automatically due to a system fault • the switch is OFF • the engine is not running. 6 DUCT LEAK LightsIlluminated (amber) – a high temperature bleed air leak is detected. 7 Engine BLEED LightsIlluminated (amber) – the engine bleed air temperature is excessive. 8 Engine High Stage (HI STAGE) LightsIlluminated (amber) – • the engine bleed system pressure is excessive • the engine high pressure bleed air valve is automatically locked closed. 9 APU Bleed Air SwitchOn (bar in view) – the APU bleed air valve is automatically controlledOff (bar not visible) – commands APU bleed air valve to close. 10 APU Bleed Air VALVE LightIlluminated (amber) – APU bleed air valve position disagrees with commandedposition. Page 23

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