ilide.info-atr-ata-21-air-conditioning-pr_463bb18d1fba56252ef310f6211f917e.pdf

[ATA] | [SUBCHAPTER] | [SECTION] [TITLE] TRAINING HANDOUT T1+T2 42-400I500 and 72- 212A (600 variant) ATA 21 AIR CONDITIONING 2.3 (19/02/2015)...

[ATA] | [SUBCHAPTER] | [SECTION] [TITLE] TRAINING HANDOUT T1+T2 42-400I500 and 72- 212A (600 variant) ATA 21 AIR CONDITIONING 2.3 (19/02/2015) [REF] Copyright © [VERSION] ([DATE]) - ATR Training Centre - All right reserved For Training Only Page 1  ATA 21 AIR CONDITIONING | | Table of content Table of Content TRAINING HANDOUT T1+T2 42-400I500 and 72-212A (600 variant) ATA 21 AIR CONDITIONING........................................................................................................................................................................................................................................ 6 21.00 GENERAL.................................................................................................................................................................................................................................................. 6 Presentation................................................................................................................................................................................................................................................... 6 Cockpit Panels................................................................................................................................................................................................................................................ 8 Cockpit Displays........................................................................................................................................................................................................................................... 10 Interfaces..................................................................................................................................................................................................................................................... 14 21.10 COMPRESSION....................................................................................................................................................................................................................................... 15 General Presentation................................................................................................................................................................................................................................... 15 System Description...................................................................................................................................................................................................................................... 16 System Operation........................................................................................................................................................................................................................................ 19 Pack Valve.................................................................................................................................................................................................................................................... 21 Service Pressure and Regulating Valve........................................................................................................................................................................................................ 23 21.50 AIR COOLING SYSTEM............................................................................................................................................................................................................................ 24 System Description...................................................................................................................................................................................................................................... 24 System Operation........................................................................................................................................................................................................................................ 27 Dual Heat Exchanger.................................................................................................................................................................................................................................... 29 Air Cycle Machine......................................................................................................................................................................................................................................... 30 Pack Overheat Switch.................................................................................................................................................................................................................................. 31 Condenser.................................................................................................................................................................................................................................................... 32 Water Extractor............................................................................................................................................................................................................................................ 33 Water Spray Nozzle...................................................................................................................................................................................................................................... 34 Copyright © 2.3 (19/02/2015) - ATR Training Centre - All right reserved For Training Only Page 2 ATA 21 AIR CONDITIONING | | Table of content Turbine Inlet Temperature Control Valve.................................................................................................................................................................................................... 35 Additional De icing Pressure Switch............................................................................................................................................................................................................. 36 Ground Cooling Turbo Fan........................................................................................................................................................................................................................... 38 Turbo Fan Shut Off Valve............................................................................................................................................................................................................................. 39 21.60 TEMPERATURE CONTROL...................................................................................................................................................................................................................... 40 System Description...................................................................................................................................................................................................................................... 40 System Operation........................................................................................................................................................................................................................................ 43 Temperature Control Valve.......................................................................................................................................................................................................................... 47 Hot By pass Valve......................................................................................................................................................................................................................................... 49 Compartment Temperature Controller....................................................................................................................................................................................................... 50 Flight Compartment and Cabin Ambient Temperature Sensors................................................................................................................................................................. 51 Duct Temperature Sensors.......................................................................................................................................................................................................................... 52 Skin Temperature Sensors........................................................................................................................................................................................................................... 53 Duct Over Temperature Switch................................................................................................................................................................................................................... 54 Duct Temperature Limiter Sensor................................................................................................................................................................................................................ 55 Cabin Temperature Ventilation Fan............................................................................................................................................................................................................. 57 21.22 CABIN AND FLIGHT COMPARTMENT AIR DISTRIBUTION....................................................................................................................................................................... 58 System Description...................................................................................................................................................................................................................................... 58 System Operation........................................................................................................................................................................................................................................ 61 Mixing Chambers......................................................................................................................................................................................................................................... 63 Ground Cart Connection.............................................................................................................................................................................................................................. 64 Recirculation Fan.......................................................................................................................................................................................................................................... 65 Cabin Foot Lever Temperature Switch......................................................................................................................................................................................................... 66 Cabin Air Distribution Duct.......................................................................................................................................................................................................................... 67 21.26 INDIVIDUAL AIR DISTRIBUTION.............................................................................................................................................................................................................. 68 Copyright © 2.3 (19/02/2015) - ATR Training Centre - All right reserved For Training Only Page 3 ATA 21 AIR CONDITIONING | | Table of content System Description...................................................................................................................................................................................................................................... 68 Individual Air Distribution Duct.................................................................................................................................................................................................................... 69 21.23 ELECTRONICS RACKS AND CABIN AIR EXTRACTION............................................................................................................................................................................... 70 System Description...................................................................................................................................................................................................................................... 70 System Operation........................................................................................................................................................................................................................................ 73 Air Extraction Fan......................................................................................................................................................................................................................................... 79 Underfloor Ventilation Valve....................................................................................................................................................................................................................... 80 Extract Air Flow Lever.................................................................................................................................................................................................................................. 81 Ambiant Temperature Sensor...................................................................................................................................................................................................................... 82 21.24 BATTERIES VENTILATION........................................................................................................................................................................................................................ 83 System Description...................................................................................................................................................................................................................................... 83 21.27 LAVATORY VENTILATION........................................................................................................................................................................................................................ 84 System Description...................................................................................................................................................................................................................................... 84 Air Supply Duct and Outlet........................................................................................................................................................................................................................... 85 21.30 PRESSURIZATION CONTROL................................................................................................................................................................................................................... 86 System Description...................................................................................................................................................................................................................................... 86 System Operation........................................................................................................................................................................................................................................ 88 Jet Pump....................................................................................................................................................................................................................................................... 93 Electro Pneumatic Outflow Valve................................................................................................................................................................................................................ 94 Pneumatic Outflow Valve............................................................................................................................................................................................................................ 96 Filter and Check Valve.................................................................................................................................................................................................................................. 99 Manual Controler....................................................................................................................................................................................................................................... 100 21.CI CONTROLS AND INDICATORS................................................................................................................................................................................................................ 103 Front Cockpit.............................................................................................................................................................................................................................................. 103 Maintenance Panel.................................................................................................................................................................................................................................... 111 Copyright © 2.3 (19/02/2015) - ATR Training Centre - All right reserved For Training Only Page 4 ATA 21 AIR CONDITIONING | | Table of content 21.00 GENERAL.............................................................................................................................................................................................................................................. 113 Safety and Precautions.............................................................................................................................................................................................................................. 113 Maintenance Operations........................................................................................................................................................................................................................... 115 Copyright © 2.3 (19/02/2015) - ATR Training Centre - All right reserved For Training Only Page 5  ATA 21 AIR CONDITIONING | 21.00 GENERAL Presentation The air conditioning system is provided to keep the passenger and flight compartments to the required pressure, temperature, humidity and cleanliness for ATA the21 AIR CONDITIONING comfort of the passengers and crew, both on ground and in flight. This air also ventilates:  Components 21.00 GENERAL located in the avionics compartment,  The lavatory. Presentation The conditioning air is bled from: The aircraft air conditioning packs supplied with air from engine compressors (on ground or in flight), or by the ground cart. The temperature and pressure of the air is controlled and distributed to the pressurized compartment. It is then discharged overboard, the air flows continuously through the cabin. The air pressure variations are automatically kept within limits compatible with passenger comfort. MW21.00_.01.G1L1_01 Copyright © 2.3 (19/02/2015) - ATR Training Centre - All right reserved For Training Only Page 6  ATA 21 AIR CONDITIONING | 21.00 GENERAL Presentation The control and the monitoring of the air conditioning system is accomplished through various indications located in the flight compartment. MW21.00_.01.G1L1_02 Copyright © 2.3 (19/02/2015) - ATR Training Centre - All right reserved For Training Only Page 7  ATA 21 AIR CONDITIONING | 21.00 GENERAL Cockpit Panels  Air conditioning system indications are given on the Multi- Function Display (SD page).  If a failure occurs on the Air Conditioning System, the Cockpit Panels Engine and Warning Display (EWD) displays alert in Alert Window with corresponding procedure in Procedure Window.  The Multi-purpose Control and Display Unit (MCDU) provides the ground crew with diagnostic informations.  The Air Conditioning Control Panel is located on the overhead panel.  The Automatic Pressurization Control Panel enable setting of the automatic pressurization system parameters. MW21.00_.02.G2L1_01 Copyright © 2.3 (19/02/2015) - ATR Training Centre - All right reserved For Training Only Page 8  ATA 21 AIR CONDITIONING | 21.00 GENERAL Cockpit Panels  The Cabin Pressurization Manual Control Panel enable manual operation and setting of the pressurization system.  The Extract Air Flow Manual Control handle enable the inhibition of the extraction air flow in front part of the flight compartment in case of smoke in the forward cargo.  Maintenance panel is located on the left side.  Several tests and control device are provided, for maintenance purpose only.  All buttons on this panel are to be used on ground only.  For maintenance purposes only, a bite loaded magnetic indicator on the RH Maintenance Panel turns amber when a system failure has been recorded. MW21.00_.03.G3L1_01 Copyright © 2.3 (19/02/2015) - ATR Training Centre - All right reserved For Training Only Page 9  ATA 21 AIR CONDITIONING | 21.00 GENERAL Cockpit Displays The Air conditioning system indications are displayed in the flight compartment on SD cabin page of the Multi Function Display (MFD) Cockpit Displays Pack indication:  State 1 is displayed when the Pack valve is ON.  State 2 is displayed when the Pack valve is Stand-by.  State 3 is displayed when the Pack valve is Fault.  State 4 is displayed when the Pack valve is OFF. Temperature control indication:  State 1 is displayed when the Temperature control is automatic.  State 2 is displayed when a duct temperature overheat occur.  State 3 is displayed when the Temperature control is manual. MW21.00_.03.G3L1_02 Copyright © 2.3 (19/02/2015) - ATR Training Centre - All right reserved For Training Only Page 10  ATA 21 AIR CONDITIONING | 21.00 GENERAL Cockpit Displays Recirculation fan indication:  State 1 is displayed when the recirculation fan is ON.  State 2 is displayed when the recirculation fan is Fault.  State 3 is displayed when the recirculation fan is OFF. Distribution indication:  State 1 is displayed when both Pack and recirculation fans are operative.  State 2 is displayed when 1 Pack and 1 recirculation fan is inoperative.  State 3 is displayed when both Pack and recirculation fans are inoperative. High Flow indication:  State 1 is displayed when the High Flow is selected.  State 2 is displayed when the High Flow is not selected. Cabin temperature indication:  State 1 is displayed when the measurement of the sensor is valid.  State 2 is displayed when the measurement of the sensor is invalid. MW21.00_.03.G3L1_04 Copyright © 2.3 (19/02/2015) - ATR Training Centre - All right reserved For Training Only Page 11  ATA 21 AIR CONDITIONING | 21.00 GENERAL Cockpit Displays Extract fan indication:  State 1 is displayed when the extract fan is operative.  State 2 is displayed when the extract fan is fault.  State 3 is displayed when the extract fan is not operative. Overboard Valve indication:  State 1 is displayed when the overboard valve is in automatic mode.  State 2 is displayed when the overboard valve is failed. State 3 is displayed when the overboard valve is manual override. Delta P indication:  State 1 is displayed when the Delta P is nominal.  State 2 is displayed when the Delta P is in pre-alerting limits.  State 3 is displayed when the Delta P is in alerting limits.  State 4 is displayed when the Delta P is invalid. MW21.00_.03.G3L1_08 Copyright © 2.3 (19/02/2015) - ATR Training Centre - All right reserved For Training Only Page 12  ATA 21 AIR CONDITIONING | 21.00 GENERAL Cockpit Displays Cabin rate indication:  State 1 is displayed when the cabin rate is nominal.  State 2 is displayed when the cabin rate is invalid. Pressurization Control indication:  State 1 is displayed when the Pressurization control is automatic.  State 2 is displayed when the Pressurization control is fault.  State 3 is displayed when the Pressurization control is manual. Cabin Altitude indication:  State 1 is displayed when the CAB ALT is nominal.  State 2 is displayed when the CAB ALT is in pre-alerting limits.  State 3 is displayed when the CAB ALT is in alerting limits. State 4 is displayed when the CAB ALT is invalid. Cabin Altitude Target indication:  State 1 is displayed when the TARGET is nominal. State 2 is displayed when the TARGET is invalid. MW21.00_.03.G3L1_11 Copyright © 2.3 (19/02/2015) - ATR Training Centre - All right reserved For Training Only Page 13  ATA 21 AIR CONDITIONING | 21.00 GENERAL Interfaces  The system is composed of:  the Air conditioning  the Ventilation  the Pressurization  The electrical system provides power for the Air Conditioning system. Interfaces  The both engines provide air through the pneumatic system.  The pneumatic system distributes of the air pressure generated by both engines to the air conditioning system.  The ground cart unit can be used during ground operations.  Air Data Computers signals are used for the pressurization automatic control.  Smoke detection system is provided by four smoke detectors.  Cockpit flight instruments, lavatory and batteries are ventilated.  The air conditioning is divided in flight compartment system and cabin system.  Flight compartment, cabin and under-floor area are pressurized.  Electrical controls signals permits to ensure the system operating. MW21.00_.04.G4L1_02 Copyright © 2.3 (19/02/2015) - ATR Training Centre - All right reserved For Training Only Page 14  ATA 21 AIR CONDITIONING | 21.10 COMPRESSION General Presentation The air conditioning is divided into four parts:  The cooling system provides flow regulation and cooling air from the pneumatic system by means of an air conditioning pack. It supplies 21.10 COMPRESSION the pressurized zones of the aircraft with cool General Presentation and conditioned air.  The air bleed from engine compressors is pressure controlled by a pack valve, before entering the air conditioning unit.  It is then pre-cooled by an air heat exchanger and routed to the air conditioning pack.  The air cooling system consists of two identical air conditioning packs, each comprising airflow regulation, a refrigeration unit and a water separator.  Both independent packs are located on each side of landing gear fairing.  The temperature control system controls air temperature at the conditioning pack outlet and inside the pressurized compartments.  Temperature control is regulated independently for the flight deck and the passenger compartment (cabin). The conditioning air temperature is obtained by mixing air from:  A hot air source upstream of the conditioning pack (air bleed from engines).  A cold air source from the conditioning heat exchangers.  The conditioned air ventilates the cabin and the flight compartment then the air is evacuated and channeled to the outflow valves; part is then discharged overboard the rest recycled to the cabin and flight compartment through a recirculation fan. MW21.10_.01.G1L1_01 Copyright © 2.3 (19/02/2015) - ATR Training Centre - All right reserved For Training Only Page 15  ATA 21 AIR CONDITIONING | 21.10 COMPRESSION System Description  The air conditioning system is designed to maintain the air within the pressurized fuselage compartments at the required levels of pressure, temperature, flow rate and purity.  The pneumatic air for the air conditioning system is bled from either low or high bleed port of each engine.  It is ducted to two identical independent air cooling units (packs) installed respectively in the left and right landing gear fairings.  Each System engine feeds the pack on its respective side through a pressure regulating and shut-off valve (pack-valve) and through a service Description pressure regulator which transmits a pressure to the temperature control valve.  Hot air from the engine is admitted through the pack valves and is conditioned (cooled, dried, compressed) in the packs.  The pack valve is pneumatically operated and electrically controlled.  It has two functions:  Pack shut-off,  Pressure control and hence flow control.  A normal and a high flow are available.  The selection of high flow mode increases the pack entrance pressure resulting in conditioning performance improvement.  Without air pressure, and regardless of electrical command, the pack valve is spring-load closed. It will also close without electrical supply. MW21.10_.02.S1L1_01 Copyright © 2.3 (19/02/2015) - ATR Training Centre - All right reserved For Training Only Page 16  ATA 21 AIR CONDITIONING | 21.10 COMPRESSION System Description  The ducts connecting the engines to the respective air cooling pack are interconnected by a cross feed valve. It opens only on ground with one engine bleed valve open (the other one closed) provided no leak is detected.  In flight, the cross feed valve is closed.  During the hotel mode operation, the Right engine runs with the propeller brake locked (on ground only), the LP and/or HP stage provide air pressure to the air conditioning system and electrical power to the aircraft network.  Xfeed valve is open MW21.10_.02.S1L1_03 Copyright © 2.3 (19/02/2015) - ATR Training Centre - All right reserved For Training Only Page 17  ATA 21 AIR CONDITIONING | 21.10 COMPRESSION System Description  The control and monitoring of the compression system is accomplished through the Air Conditioning panel located on the overhead panel.  When a pack valve failure is detected, the CCAS is activated associated with a PACK VALVE FAULT light, a Fault legend on MFD/SD Cabin page and "AIR PACK" caution message (Pack 1 or 2) on the EWD.  If both pack valves are faulty, "AIR PACK 1+2" caution message will be displayed on the EWD. MW21.10_.02.S1L1_04 Copyright © 2.3 (19/02/2015) - ATR Training Centre - All right reserved For Training Only Page 18  ATA 21 AIR CONDITIONING | 21.10 COMPRESSION System Operation  Here is the simplified schematic of pack valve 2 operation. The pack valve is controlled to open when the bleed air shut off valve is open and the valve is selected "ON" or with X FEED valve System Operation open and provided no fault is detected.When all the conditions are met the signal is delayed by 6 s (not shown on the screen). Note: delay is only applicable to the pack valve 2.  When the time is elapsed the shut-off valve solenoid is energized and, as air pressure is available the pack valve opens and regulates at 22 PSI (normal flow). Note: the pack control relay provides information to the cabin pressure controller and to the cabin temperature sensor ventilation fan.  To increase the flow, the "flow" push button has to be selected on, this acts on the high pressure differential solenoid. Now the pack valve regulates at 30 PSI (high flow). The "flow" push button is common to both packs. Note: that a signal is sent to engine electronic control to decrease slightly the fuel to prevent ITT increasing. MW21.10_.03.S2L2_01 Copyright © 2.3 (19/02/2015) - ATR Training Centre - All right reserved For Training Only Page 19  ATA 21 AIR CONDITIONING | 21.10 COMPRESSION System Operation  In case of pack overheat (204°C). The pack valve will close automatically. Fault light illuminates because the pack valve selection (on) disagrees with the valve position (closed). In addition, on the RH maintenance panel the "bite loaded" magnetic indicator turns on to indicate the fault. Note: a pack overheat could be due to a dirty heat exchanger or a turbo fan failure MW21.10_.04.E1L1_01 Copyright © 2.3 (19/02/2015) - ATR Training Centre - All right reserved For Training Only Page 20  ATA 21 AIR CONDITIONING | 21.10 COMPRESSION Pack Valve  Pack valve is located on the forward landing gear fairing and regulates, or shuts off the flow of the engine bleed air to the pack. Pack Valve  The solenoid-controlled shut-off valve is a pneumatically-actuated, butterfly type, with a variable pressure regulator.  Two pack valves, one in each pack, pneumatically operated and electrically controlled, regulate the air flow and pressure. These valves also work as shut-off valves.  The valve consists of a:  High reference regulator (30 PSI),  Low reference regulator (22 PSI),  Shut-off solenoid valve assembly,  High differential solenoid valve assembly,  Actuator assy,  Flow section,  A position indicator switch assembly. MW21.10_.06.C1L3_01 Copyright © 2.3 (19/02/2015) - ATR Training Centre - All right reserved For Training Only Page 21  ATA 21 AIR CONDITIONING | 21.10 COMPRESSION Pack Valve Pack Valve Operation  With the shut-off solenoid de-energized the valve is closed.  With both the shut-off solenoid and the high pressure solenoid energized, the valve is open and the flow pressure is regulated at 30+/- 5 PSI.  With the high pressure solenoid de-energized, the valve is still open, but the flow pressure is regulated at 22 +/- 5 PSI. MW21.10_.06.C1L3_03 Copyright © 2.3 (19/02/2015) - ATR Training Centre - All right reserved For Training Only Page 22  ATA 21 AIR CONDITIONING | 21.10 COMPRESSION Service Pressure and Regulating Valve  The service pressure regulator located in the landing gear fairing is pneumatically activated poppet-type differential pressure regulator. Service Pressure and Regulating Valve  It provides a constant source of regulated supply air to the temperature control valve.  The valve consists of a:  Calibration adjustment screw,  Diaphragm cover,  Regulator housing,  Service pressure regulator,  Supply pressure connection,  Capped port,  Ambient vent. Operation:  Input pressure from the bleed air duct (upstream the pack valve) is applied to the service pressure regulator. The poppet modulates in response to the interaction of output pressure acting on the diaphragm, through the feedback orifice, and the calibration spring to deliver a regulated supply pressure of 16.4 PSI to the temperature control valve.  When the balance between the opening force and closing force is upset (change in supply pressure or change in output usage) the poppet valve will find a new position and return to the calibrated output. MW21.10_.07.C1L3_01 Copyright © 2.3 (19/02/2015) - ATR Training Centre - All right reserved For Training Only Page 23  ATA 21 AIR CONDITIONING | 21.50 AIR COOLING SYSTEM System Description  The Air Cooling system provides flow regulation and cooling air from the pneumatic system by means of an air 21.50 AIR COOLING SYSTEM conditioning pack in order to supply the System Description pressurized zones of the aircraft with cool air.  The Air Cooling system consists of two identical air cooling units (packs) that work independently.  The both packs are installed outside the pressurized zone in the right and left hand main landing gear pods.  A cooling turbo-fan provides cooling air on ground or in flight when the aircraft speeds is lower than 150Kts with landing gears down.  In other cases, cooling air is provides by ram-air.  The temperature of air supplying the pressurized zones of the aircraft with conditioned air is regulated by the temperature control system.  Each air conditioning packs comprise an air flow regulation, a refrigeration unit and a water separator.  These packs enable humidity to be controlled.  Air is supplied by the right engine for the passenger compartment and by the left engine for the flight compartment and 32% of the passenger compartment. MW21.50_.01.S1L1_01 Copyright © 2.3 (19/02/2015) - ATR Training Centre - All right reserved For Training Only Page 24  ATA 21 AIR CONDITIONING | 21.50 AIR COOLING SYSTEM System Description The cooling air generation assembly consists of:  A cooling inlet (ram air).  A ground cooling turbo-fan energized by the bleed air, enable the circulation of air in the heat exchangers.  Two check valves are installed in the cooling air duct to avoid reverse flow.  An Air Cycle Machine (ACM) comprising a compressor and a turbine.  A Condenser enable to condense moisture contains in the air.  A Water Spray Nozzle sprays extracted water in front of heat exchangers.  A Turbine temperature Inlet Control valve avoids turbine icing.  An additional de-icing pressure switch avoids ice accretion.  A pack over temperature switch detects a pack overheat. MW21.50_.01.S1L1_03 Copyright © 2.3 (19/02/2015) - ATR Training Centre - All right reserved For Training Only Page 25  ATA 21 AIR CONDITIONING | 21.50 AIR COOLING SYSTEM System Description  The control and monitoring of the cooling system is accomplished through the Air Conditioning panel located on the overhead panel.  When a pack overheat is detected, the CCAS is activated associated with a PACK VALVE FAULT light, a FAULT legend on MFD/SD Cabin page and "AIR PACK" caution message (Pack 1 or 2) on the EWD.  For maintenance purpose, MFC bite loaded magnetic indicator turns amber when a failure has been recorded by the MFC.  By selecting MISC1, pack overheat detection will be displayed. MW21.50_.01.S1L1_05 Copyright © 2.3 (19/02/2015) - ATR Training Centre - All right reserved For Training Only Page 26  ATA 21 AIR CONDITIONING | 21.50 AIR COOLING SYSTEM System Operation  Hot air from the bleed air system goes through the pack valve to the primary heat exchanger where it is cooled.  Depending on the aircraft configuration, cooling of the heat exchangers is provided either by the ram air inlet or by the Cooling Turbo Fan (Turbo fan is shown not running).  Cooled air is compressed by the compressor, routed to the secondary heat exchanger and ducted to the condenser. The water extractor extracts water Operation System from the air then, the water is sprayed in the cooling air stream and contributes to the efficiency of the heat exchangers.  Compressed air expands through the turbine where it gets cold. This cold air flow will be mixed with hot air from the temperature control valve and the hot bypass valve and then routed to the mixing chamber.  Note: the hot bypass valve which is slaved to the temperature control valve opens for a given opening of the temperature control valve.  Should the turbine inlet temperature reaches a preset value, the turbine inlet temperature control valve (T.I.C. valve) opens allowing hot air from the compressor outlet to mix with the "cold" air from the water extractor preventing reduction of air flow to the compartment due to ice formation.  When an icing condition is detected by the additional pressure switch between the compressor outlet duct and the water separator outlet duct, the switch controls the temperature control valve to full open to prevent icing of the air cycle machine.  Note: During this operation, the compartment temperature control is inhibited as long as the icing condition is present. MW21.50_.02.S2L2_01 Copyright © 2.3 (19/02/2015) - ATR Training Centre - All right reserved For Training Only Page 27  ATA 21 AIR CONDITIONING | 21.50 AIR COOLING SYSTEM System Operation  In case of pack overheat detected downstream of the compressor the "bite loaded" magnetic announciator located on the RH maintenance panel turns on (not shown).  The pack overheat will cause the pack valve to close and the fault light to illuminate. As a side effect the temperature control valve, the hot bypass valve and the turbo-fan shut-off valve are controlled to close and the turbo-fan stops (if running). MW21.50_.02.S2L2_02 Copyright © 2.3 (19/02/2015) - ATR Training Centre - All right reserved For Training Only Page 28  ATA 21 AIR CONDITIONING | 21.50 AIR COOLING SYSTEM Dual Heat Exchanger  The dual heat exchanger is located in the forward landing gear fairing. Dual Heat Exchanger  The dual heat exchanger is an air-to-air plate-fin unit. In reality, it is two heat exchangers contained in a single housing.  There is a primary and a secondary section. Each section consists of a rectangular plate- fin core with an inlet and outlet pans welded on opposite ends.  Bleed air from the pack valve enters the primary heat exchanger at the "T" duct. The other leg of the "T" duct provides the source of hot bleed air for the temperature control valve.  After passing through the primary heat exchanger, air flows through the compressor section of the cooling turbine.  It then returns to enter the secondary heat exchanger as shown at the top of the unit.  After passing through the secondary heat exchanger, the air is routed to the condenser to begin the water removal process. MW21.50_.05.C1L3_01 Copyright © 2.3 (19/02/2015) - ATR Training Centre - All right reserved For Training Only Page 29  ATA 21 AIR CONDITIONING | 21.50 AIR COOLING SYSTEM Air Cycle Machine  The air cycle machine is located in the forward landing gear fairing.  The air cycle machine consists of:  A compressor section, Air Cycle Machine  A turbine section.The rotating group consists of a centrifugal compressor impeller and a radial in-flow turbine wheel mounted on a common shaft (bootstrap).  The shaft is supported on air bearings which have been designed to operate without scheduled maintenance.  Air is ducted from the primary section of the dual heat exchanger to the compressor section of the air cycle machine, where flow temperature and pressure increase.   The compression heat is partially removed in the secondary section of the dual heat exchanger. Air is then ducted to the cooling turbine where it expands and gets cold. MW21.50_.06.C1L3_01 Copyright © 2.3 (19/02/2015) - ATR Training Centre - All right reserved For Training Only Page 30  ATA 21 AIR CONDITIONING | 21.50 AIR COOLING SYSTEM Pack Overheat Switch  The overheat switch is installed downstream the air cycle machine compressor, before the second heat exchanger. Pack Overheat Switch  The pack overheat switch protects the air cycle machine in the event of a cooling-air circuit restriction or leakage and from excessive bleed air temperature.  It consists of a vapor-filled sensing probe, stainless steel diaphragm, belleville reference spring washer, and a double pole/single throw. A temperature of approximately 204°C will produce a force sufficient to overcome the diaphragm spring washer and actuate the switch.  When the fluid vapor within the probe is subjected to the hot compressor discharge air, it expands and applies a force to the diaphragm. When air temperature across the probe has decreased to the reset value of approximately 182°C, the switch returns to a normaly closed position. MW21.50_.07.C1L3_01 Copyright © 2.3 (19/02/2015) - ATR Training Centre - All right reserved For Training Only Page 31  ATA 21 AIR CONDITIONING | 21.50 AIR COOLING SYSTEM Condenser  The condenser is located in the forward landing gear fairing, after the Air Cycle Machine. Condenser  The condenser is a plate-fin, single-pass crossflow, air to air heat exchanger. The ducts, pans, flanges and other parts are aluminium alloy.  The hot side of the core includes hollow tubes through which hot air flows to prevent ice buildup on the cold air face (anti-icing).  The hoses provide the air inlets and connection for the turbine anti-ice return. Both bleed air and conditioned air make a single pass through the condenser core. MW21.50_.08.C1L3_01 Copyright © 2.3 (19/02/2015) - ATR Training Centre - All right reserved For Training Only Page 32  ATA 21 AIR CONDITIONING | 21.50 AIR COOLING SYSTEM Water Extractor  The water extractor is located in the forward landing gear fairing, between the secondary heat exchanger and the turbine inlet. Water Extractor  The water extractor removes the water from the moisture produced by the condenser.  The water extractor is an in-line, integral duct type device that incorporates four helix blades, brazed to the central hub and to the duct inner valve, and a downstream water collector.  The extracted moisture is collected downstream in a collector which consists a formed- perforated collector ring, an outer muff, a water drain pipe, and a scavenge air port. These components are brazed together to form a sub- assembly which is welded onto the duct/helix sub-assembly.  The water extracted is sprayed through a spray nozzle on the dual heat exchangers air inlet. MW21.50_.09.C1L3_01 Copyright © 2.3 (19/02/2015) - ATR Training Centre - All right reserved For Training Only Page 33  ATA 21 AIR CONDITIONING | 21.50 AIR COOLING SYSTEM Water Spray Nozzle  The water spray nozzle is located at the air inlet of the heat exchangers.  The water spray nozzle is an orificed fitting that provides a means to attach the line from the water extractor to the ram air plenum.  The nozzle provides a restriction and atomizes the water while spraying it in the cooling airstream before it passes through the dual heat exchangers. The evaporative cooling effect contributes to the efficiency of the heat exchangers. WaterSpray TheNozzle nozzle must be installed with the arrow properly positioned. MW21.50_.10.C1L3_01 Copyright © 2.3 (19/02/2015) - ATR Training Centre - All right reserved For Training Only Page 34  ATA 21 AIR CONDITIONING | 21.50 AIR COOLING SYSTEM Turbine Inlet Temperature Control Valve  This valve is installed near the air cycle machine.  The enclosure of the valve is made from aluminium alloy in two parts which are attached by four bolts.  Air flow from the water extractor passes over the thermal sensing element before to reach cooling turbine. Cold air causes the sensor/actuator to contract and open the poppet valve which adds some hot air (tapped from the compressor outlet duct) to the air flow Turbinefrom Inlet the water extractor. Temperature Control Valve  The thermal element and poppet valve are enclosed in the valve body. The action controls turbine inlet temperature to a minimum of 24°C and reduces the possibility of turbine icing. MW21.50_.11.C1L3_01 Copyright © 2.3 (19/02/2015) - ATR Training Centre - All right reserved For Training Only Page 35  ATA 21 AIR CONDITIONING | 21.50 AIR COOLING SYSTEM Additional De icing Pressure Switch  This pressure switch is installed in the forward landing gear fairing. It is a differential pressure switch connected to compressor outlet duct and water separator Additional De icing Pressure Switch outlet duct.  The purpose of the additional de-icing pressure switch is to detect condenser icing by monitoring the differential pressure across the condenser bleed air path.  Two pressure inputs are provided to the switch. One is tapped from the duct between the secondary heat exchanger outlet and the condenser inlet. The other is tapped from the turbine air inlet.  The signal from this switch will change the position of the temperature control valve in case of ice accretion. When the differential pressure between the two inputs increases to 9 PSI. MW21.50_.12.C1L3_01 Copyright © 2.3 (19/02/2015) - ATR Training Centre - All right reserved For Training Only Page 36  ATA 21 AIR CONDITIONING | 21.50 AIR COOLING SYSTEM Additional De icing Pressure Switch System Operation:  The switch closes when a differential pressure of 9 PSI is detected by the pressure switch due to ice accretion in the condenser, or in the water extractor.  The switch closes and after a 1 second time delay, a steady current is applied to the temperature control valve torque motor overriding the normal temperature