B1.1 Boeing 737-600 - 700 - 800 - 900 (CFM 56) 21 Air Conditioning Rev. 01 [PDF]

Zitiervorschau

Boeing 737-600/700/800/900 (CFM 56) subcat. B1.1

ATA 21 AIR CONDITIONING

TRAINING MANUAL

Boeing 737-600/700/800/900 (CFM 56) subcat. B1.1 21 AIR CONDITIONING (ATA21) LEVEL 3

ISSUE 1, Rev. 1: 2015.07.10

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Boeing 737-600/700/800/900 (CFM 56) subcat. B1.1

ATA 21 AIR CONDITIONING

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Boeing 737-600/700/800/900 (CFM 56) subcat. B1.1

ATA 21 AIR CONDITIONING

TABLE OF CONTENTS ATA 21 AIR CONDITIONING ................................................................. 7 ABBREVIATIONS AND ACRONYMS ....................................................... 7 21-00 GENERAL ................................................................................... 8 AIR CONDITIONING SYSTEM DESCRIPTION .......................................... 8 OVERHEAD PANEL DESCRIPTION ..................................................... 11 PNEUMATIC CONTROL PANEL ........................................................... 11 COOLING............................................................................................... 13 PACK VALVE DESCRIPTION ................................................................ 13 FCSOV — FUNCTIONAL DESCRIPTION.............................................. 15 PACK PROTECTION ............................................................................. 17 PACK VALVE ......................................................................................... 19 HEAT EXCHANGER AND PLENUM / DIFF. ASSEMBLY ...................... 21 RAM AIR DUCTS ................................................................................... 23 RAM AIR INLET ..................................................................................... 25 RAM AIR INLET CONTROLLER ............................................................ 27 RAM AIR FUNCTION ............................................................................. 29 RAM AIR MODULATION........................................................................ 31 AIR CYCLE MACHINE ........................................................................... 33 COMPRESSOR / TURBINE OVERHEAT SW ........................................ 35 WATER SEPARATOR ........................................................................... 37 2° C ANTI ICE CONTROL SYSTEM ...................................................... 39 2° CONTROLLER BITE.......................................................................... 41 2° C ANTI ICE CONTROL SYSTEM FUNCTIONAL ............................... 43 21-60 TEMPERATURE CONTROL........................................................... 45 TEMPERATURE SENSORS .................................................................. 48 TEMPERATURE CONTROL OPERATION ............................................ 50 AUTOMATIC CONTROL ........................................................................ 52 CABIN TEMPERATURE CONTROLLER ............................................... 54 AIR CONDITIONING ACCESSORY UNIT.............................................. 56 CABIN TEMPERATURE SENSOR......................................................... 58 CABIN TEMPERATURE SENSOR FAN................................................. 60 MIXING VALVE ...................................................................................... 62 AIR MIX VALVE POSITION INDICATOR ............................................... 64 CABIN TEMPERATURE MODULE PRINTED CIRCUIT ASSEMBLY ..... 66 TEMPERATURE INDICATING ............................................................... 68 21-20 DISTRIBUTION............................................................................... 70 OVERHEAD DISTRIBUTION DUCT ...................................................... 72 GALLEY VENTILATION ......................................................................... 74 ISSUE 1, Rev. 1: 2015.07.10

MAIN DISTRIBUTION MANIFOLD ......................................................... 76 RECIRCULATION FAN FUNCTIONAL DESCRIPTION ......................... 78 FLIGHT COMPARTMENT COND. AIR DISTRIBUTION ........................ 80 PASS. CABIN COND. AIR DISTRIBUTION ........................................... 82 DOOR AREA HEATER .......................................................................... 84 DOOR AREA HEATING — FUNCTIONAL DESCRIPTION .................... 86 EQUIPMENT COOLING SYSTEM ......................................................... 88 COMPONENT LOCATION ..................................................................... 90 SUPPLY AND EXHAUST FANS ............................................................ 92 AIR FILTER............................................................................................ 94 LOW FLOW SENSOR............................................................................ 96 SUPPLY FAN FUNCTION...................................................................... 98 EXHAUST FAN FUNCTION ................................................................. 100 OVERBOARD EXHAUST VALVE ........................................................ 102 OVERBOARD EXHAUST VALVE FUNCTIONAL ................................. 104 21-50 COOLING ................................................................................. 106 COOLING — FUNCTIONAL DESCRIPTION ....................................... 106 PNEUMATIC CONTROL PANEL ......................................................... 108 TEMPERATURE CONTROL PANEL ................................................... 108 RAM AIR SYSTEM-FUNCTIONAL ....................................................... 110 HEAT EXCHANGER AND WATER EXTRACTOR DESCRIPTION ...... 112 WATER EXTRACTOR DUCT .............................................................. 114 PRIMARY WATER EXTRACTOR ........................................................ 116 PACK TEMPERATURE CONTROL VALVES....................................... 118 TEMPERATURE CONTROL VALVES SCHEMATIC DESCRIPTION .. 120 MIX MANIFOLD TEMPERATURE SENSOR ........................................ 122 21 - 60 TEMPERATURE CONTROL .................................................. 124 TRIM AIR PRESSURE REGULATING VALVE..................................... 124 TRIM AIR MODULATING VALVE ........................................................ 126 THERMAL SENSING UNITS ............................................................... 128 AIR CONDITIONING ACCESSORY UNIT ........................................... 130 PACK/ZONE TEMPERATURE CONTROLLER.................................... 132 TEMPERATURE CONTROL ................................................................ 134 PACK / ZONE TEMPERATURE CONTROL ........................................ 136 UNBALANCED COOLEST MODE ....................................................... 138 UNBALANCED AVERAGE MODE ....................................................... 140 21-20 DISTRIBUTION ............................................................................. 142 CONDITIONED AIR DISTRIBUTION ................................................... 142 MIX MANIFOLD ................................................................................... 144 RIGHT RECIRCULATION FAN ............................................................ 146

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Boeing 737-600/700/800/900 (CFM 56) subcat. B1.1

ATA 21 AIR CONDITIONING

LEFT RECIRCULATION FAN .............................................................. 146 21 - 30 PRESSURIZATION CONTROL .................................................. 148 PRESSURIZATION — GENERAL DESCRIPTION .............................. 150 PRESSURE CONTROL MODULE ....................................................... 152 CABIN PRESSURE CONTROLLER (CPC) .......................................... 154 CABIN PRESSURE CONTROLLER BITE ............................................ 156 EXISTING FAULTS .............................................................................. 158 FAULT HISTORY ................................................................................. 160 SYSTEM TEST .................................................................................... 162 DISPLAY TEST .................................................................................... 164 AFT OUTFLOW VALVE ASSEMBLY ................................................... 166 POSITIVE PRESSURE RELIEF VALVE .............................................. 166 SAFETY RELIEF VALVE OPERATION ................................................ 168 NEGATIVE PRESSURE RELIEF VALVE ............................................. 170 CARGO COMPARTMENT BLOWOUT PANEL .................................... 172 AUTO MODE FLIGHT PROFILE .......................................................... 174 AUTO MODE FUNCTIONAL DESCRIPTION ....................................... 176 AUTO FAIL........................................................................................... 178 OFF SCHEDULED DESCENT ............................................................. 180 MANUAL MODE FUNCTIONAL DESCRIPTION .................................. 182 MANUAL MODE CONTROL ................................................................ 184 CABIN PRESSURE INDICATION AND ALTITUDE WARNING SYSTEM186 CABIN ALTITUDE WARNING .............................................................. 188

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Boeing 737-600/700/800/900 (CFM 56) subcat. B1.1

ATA 21 AIR CONDITIONING

TABLE OF FIGURES AIR CONDITIONING SYSTEM SCHEMATIC ........................................... 10 OVERHEAD CONTROL PANEL .............................................................. 12 PACK VALVE ........................................................................................... 14 PACK FLOW CONTROL .......................................................................... 16 PACK PROTECTION ............................................................................... 18 PACK VALVE SCHEMATIC ..................................................................... 20 HEAT EXCHANGER ................................................................................ 22 RAM AIR DUCTS ..................................................................................... 24 RAM AIR MOD. PANEL ........................................................................... 26 RAM AIR CONTROL TEMPERATURE SENSOR .................................... 28 RAM AIR SYSTEM SCHEMATIC ............................................................. 30 RAM AIR MODULATING SYSTEM SCHEMATIC .................................... 32 AIR CYCLE MACHINE ............................................................................. 34 COMPRESSOR DISCHARGE/ TURBINE INLET OVERHEAT SWITCH .. 36 WATER SEPARATOR ............................................................................. 38 2° C ANTI ICE VALVE AND SENSOR ..................................................... 40 2° C ANTI-ICE CONTROLLER ................................................................. 42 2° C ANTI ICE CONTROL ........................................................................ 44 TEMPERATURE CONTROL SYSTEM SCHEMATIC ............................... 47 TEMPERATURE CONTROL SENSORS .................................................. 49 TEMPERATURE CONTROL MANUAL MODE ........................................ 51 TEMPERATURE CONTROL AUTO ......................................................... 53 CABIN TEMPERATURE CONTROLLER ................................................. 55 AIR CONDITIONING ACCESSORY UNIT ................................................ 57 PASSENGER AND CONTROL CABIN SENSORS .................................. 59 PASSENGER AND CONTROL CABIN SENSOR FAN ............................ 61 MIXING VALVE ........................................................................................ 63 MIX VALVE POSITION INDICATOR ........................................................ 65 CABIN TEMPERATURE MODULE .......................................................... 67 TEMPERATURE INDICATING SYSTEM .................................................. 69 DISTRIBUTION GENERAL ...................................................................... 71 PASSENGER CABIN OVERHEAD DISTRIBUTION ................................ 73 GALLEY VENTILATION ........................................................................... 75 MAIN DISTRIBUTION MANIFOLD ........................................................... 77 RECIRCULATION SYSTEM SCHEMATIC ............................................... 79 FLIGHT COMPARTMENT AIRFLOW....................................................... 81 PASSENGER CABIN AIRFLOW .............................................................. 83 ISSUE 1, Rev. 1: 2015.07.10

DOOR AREA HEATER .............................................................................85 DOOR AREA HEATING SYSTEM SCHEMATIC ......................................87 EQUIPMENT COOLING GENERAL ..........................................................89 EQUIPMENT COOLING COMPONENTS ..................................................91 SUPPLY AND EXHAUST FAN GENERAL ...............................................93 LOW FLOW SENSOR ...............................................................................95 LOW FLOW DETECTOR ..........................................................................97 SUPPLY FAN FUNCTIONAL SCHEMATIC ..............................................99 EXHAUST FANS FUNCTIONAL SCHEMATIC ....................................... 101 OVERBOARD EXHAUST VALVE ........................................................... 103 EXHAUST VALVE FUNCTIONAL SCHEMATIC ..................................... 105 AIR CONDITIONING SYSTEM SCHEMATIC .......................................... 107 OVERHEAD CONTROL PANEL ............................................................. 109 RAM AIR SYSTEM ELECTRICAL SCHEMATIC .................................... 111 CONDENSER AND REHEATER ............................................................. 113 WATER EXTRACTOR DUCT .................................................................. 115 PRIMARY WATER EXTRACTOR ........................................................... 117 TEMPERATURE CONTROL VALVES .................................................... 119 TEMPERATURE CONTROL VALVE SCHEMATIC ................................ 121 MIX MANIFOLD SENSOR....................................................................... 123 TRIM AIR PRESSURE REGULATOR ..................................................... 125 TRIM AIR MODULATING VALVE ........................................................... 127 DUCT TEMPERATURE SENSORS ........................................................ 129 AIR CONDITIONING ACCESSORY UNIT ............................................... 131 PACK / ZONE CONTROLLER ................................................................ 133 TEMPERATURE CONTROL BALANCED MODE ................................... 135 PACK / ZONE TEMPERATURE CONTROL ........................................... 137 TEMPERATURE CONTROL UNBALANCED COOLEST MODE ............ 139 TEMPERATURE CONTROL UNBALANCED AVERAGE MODE ........... 141 DISTRIBUTION SYSTEM GENERAL...................................................... 143 MIX MANIFOLD ...................................................................................... 145 RIGHT RECIRCULATION FAN CIRCUIT ................................................ 147 PRESSURIZATION CONTROL ............................................................... 149 PRESSURE CONTROL INTERFACE ..................................................... 151 PRESSURE CONTROL MODULE .......................................................... 153 CABIN PRESSURE CONTROLLER ....................................................... 155 CPC-BITE (MAIN MENU) ........................................................................ 157 CPC-BITE (EXISTING FAULTS) ............................................................. 159 CPC-BITE (FAULT HISTORY) ................................................................ 161 CPC-BITE (GROUND TESTS) SYSTEM TEST ....................................... 163

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Boeing 737-600/700/800/900 (CFM 56) subcat. B1.1

ATA 21 AIR CONDITIONING

CPC-BITE (GROUND TESTS) DISPLAY TEST ..................................... 165 AFT OUTFLOW VALVE ......................................................................... 167 PRESSURE RELIEF VALVE SCHEMATIC ............................................ 169 NEGATIVE PRESSURE RELIEF VALVE ............................................... 171 BLOWOUT PANELS .............................................................................. 173 AUTO MODE FLIGHT PROFILE ............................................................ 175 AUTO MODE FUNCTIONAL SCHEMATIC ............................................ 177 AUTO FAIL SCHEMATIC ....................................................................... 179 OFF SCHEDULE DESCENT CIRCUIT ................................................... 181 PRESSURE CONTROL MANUAL MODE .............................................. 183 MANUAL MODE ELECTRICAL SCHEMATIC ....................................... 185 CABIN PRESSURE AND ALTITUDE WARNING SYSTEM ................... 187 CABIN ALTITUDE WARNING CIRCUIT ................................................ 188 P1-3 PANEL BEFORE AND AFTER MODIFICATION ........................... 189

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Boeing 737-600/700/800/900 (CFM 56) subcat. B1.1 ATA 21

ATA 21 AIR CONDITIONING AIR CONDITIONING

ABBREVIATIONS AND ACRONYMS A/C ACAU ºC clng CTC EE °F

air conditioning air conditioning accessory unit Celsius cooling cabin temperature controller electronic equipment Fahrenheit

Air Conditioning Sub—systems Distribution  Heating  Cooling  Temperature control  Humidity / air contaminant control  Pressurization.

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Boeing 737-600/700/800/900 (CFM 56) subcat. B1.1

ATA 21 AIR CONDITIONING MIXING VALVE COLD AIR

21-00 GENERAL AIR CONDITIONING SYSTEM DESCRIPTION

The cold air disk regulates the amount of air through the cooling pack.The valve is controlled by auto and manual mode. When the pack valve is closed, the mix valve drive to full cold.

GENERAL The air conditioning system provides a conditioned air environment for the passengers and crew, assuring comfort and safety. The air conditioning packs receive hot air (212°C) from the pneumatic system. The packs control the temperature, rate of flow, and distribute it throughout the passenger and control compartments. AIR CONDITIONING PACK The flow control valves (pack valves) provide pack ON / OFF control, and one of three different flow schedules in response to the pack switch and APU bleed switch selection on the P5 panel. MIXING VALVE HOT AIR An air mix valve, downstream of the pack valve, regulates cabin temperature by allowing a controlled amount of hot air to by-pass the air cycle system. The valve is a dual housing assembly with two disk plates mounted on a common shaft 90° opposed. As one disk moves from open toward closed, the other moves from closed toward open. One part of the air is routed to the hot air plate of the mixing valve, bypasses the cooling pack, directed through the mixing chamber. The remainder is directed through the PRIMARY HEAT EXCHANGER,

AIR CYCLE MACHINE, (COMPRESSOR) The air cycle machine is a cooling unit consisting of a compressor and turbine on a common shaft. The air enters the compressor, where the pressure and temperature of the air is increased. The air cycle machine (ACM) decreases air temperature, by expansion through a turbine. Foil air bearings support the shaft. The air bearings let the ACM rotate at high speed with little friction. An air-bearing boost-air line connects at the center of the ACM. The upstream supply of air comes from a port on the upstream side of the flow control and shutoff valve. When the airplane is in flight, demand from the air cycle machine decreases and ram air pressure increases. The increase in ram air pressure opens the check valve and lets more air go through the heat exchanger without the increase of fan operation. WATER SEPARATOR As the air cools, its moisture content condenses. The water separator collects this atomized moisture and removes it from the air cycle system. This water is sprayed into the ram air inlet duct, upstream of the pack heat exchanger, through a water spray nozzle. The water separator 2°C control system bypasses hot air around the air cycle machine, if needed, to prevent water freezing in the separator.

The primary heat exchanger is an air - to - air type. The ram air system employs outside air as a cooling medium across the heat exchanger. The amount of outside air permitted to flow through the heat exchangers is determined by ram air inlet panels. During periods of low ram air supply, such as airplane on ground, ascent, or descent, an air-cycle-machine operated fan induces outside air flow across the heat exchangers. In cruise, inlet panels modulate open to control the amount of air flow through the heat exchangers. The amount of opening is automatically controlled to maintain a temperature of 110°C (230°F) at the compressor discharge. ISSUE 1, Rev. 1: 2015.07.10

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Boeing 737-600/700/800/900 (CFM 56) subcat. B1.1

ATA 21 AIR CONDITIONING

PACK PROTECTION Protection of the pack is provided by four thermal switches.  90° C (Supply Duct) mixing valve drives to FULL COLD.  100°C (Turbine Inlet) pack valve closes.  120°C (Distribution Manifold) pack valve closes.  200°C (Compressor Outlet) pack valve closes. If the Pack Valve is closed, the Mixing Valve drives to FULL COLD. AIR CONDITIONING DISTRIBUTION Cold air leaving the water separator then travels to the mixing chamber. The cold air is then mixed with the remainder of the warm air as required to obtain the conditioned air temperature called for by the temperature control system. This conditioned air distribution system routes temperature controlled air to the passenger and control cabins.

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Boeing 737-600/700/800/900 (CFM 56) subcat. B1.1

ATA 21 AIR CONDITIONING

AIR CONDITIONING SYSTEM SCHEMATIC

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Boeing 737-600/700/800/900 (CFM 56) subcat. B1.1

ATA 21 AIR CONDITIONING

OVERHEAD PANEL DESCRIPTION TEMPERATURE CONTROL PANEL PNEUMATIC CONTROL PANEL AIR TEMPERATURE SOURCE SELECTOR RECIRCULATION FAN SWITCH AUTO Fan is running exempt when both Packs are operating with either Pack Switch in HIGH.

 SUPPLY DUCT Selects Main Distribution Supply Duct Sensor for Temperature Indicator.  PASS CABIN Selects Passenger Cabin Sensor for Temperature Indicator.

PACK SWITCH

TEMPERATURE INDICATOR

AUTO With both packs operating in AUTO, each Pack regulates to normal Flow Rate. With one Pack operating, regulates to high Flow Rate when:  in Flight and Flaps Up (if Engine Bleed is used)  in Flight, regardless of Flaps (if APU Bleed is used).  HIGH Pack regulates to High Flow. If APU Bleed Air is used on Ground, the Pack regulates to APU High Flow which exceeds the High Flow Rate by approx. 20%.

 Indicates Temperature at location selected with Air Temperature Source Selector (SUPPLY DUCT or PASS CABIN) MIXING VALVE INDICATOR  Indicates Position of Air Mix Valves DUCT OVERHEAT LIGHT (AMBER)  Indicates Cockpit / Passenger Cabin Duct Overheat 90° C. Air Mix Valve drives to Full Cold.

PACK TRIP OFF LIGHT TEMPERATURE SELECTOR Indicates Pack Trip off. Pack Valve automatically closes and Air Mixing Valve drive to Full Cold. Trip caused by Compressor Discharge 200° C, or Turbine Inlet 100° C, or Supply Duct Temperature 120° C. MASTER CAUTION Light and AIR COND Annunciator will illuminate.

 AUTO Air Mix Valve controlled by the Temperature Controller.  MANUAL Air Mix Valve controlled manually.

TRIP RESET SWITCH

RAM DOOR FULL OPEN LIGHT (BLUE)

PRESSED If the Fault condition has been corrected, Resets BLEED TRIP OFF, PACK TRIP OFF and DUCT OVERHEAT. Light remain illuminated until reset.

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 Indicates respective Ram Door in Full Open Range

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Boeing 737-600/700/800/900 (CFM 56) subcat. B1.1

ATA 21 AIR CONDITIONING

OVERHEAD CONTROL PANEL

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Boeing 737-600/700/800/900 (CFM 56) subcat. B1.1

ATA 21 AIR CONDITIONING COOLING

PACK VALVE DESCRIPTION The pack valve is a pneumatically actuated, electrically controlled disk valve. It provides air conditioning pack ON or OFF capability in response to the pack switch on the overhead panel, or to any of three overheat switches in the system. During normal operating, it modulates to meter pack airflow to one of three flow schedules:  OFF The pack valve is closed.  AUTO With both packs operating in AUTO, each pack regulates to normal flow rate approximately 55 lbs/min. This is the normal in-flight schedule. It provides optimum airplane performance, but requires a recirculation fan to meet desired cabin ventilation rate. As cabin altitude increases, the pack valve is biased to supply a lower airflow rate. With one Pack operating, regulates to high Flow Rate when:  in Flight and Flaps Up (if Engine Bleed is used)  in Flight, regardless of Flaps (if APU Bleed is used).  HIGH Pack regulates - 80 lbs/min. This rate can be selected manually when additional cooling and or ventilation is desired. As cabin altitude increases, the pack valve is biased to supply a lower airflow rate. If APU bleed air is used on ground, the pack regulates to APU high flow approximately - 100 lbs/min. The pack valve controls the mass flow so, that a nearly constant volumetric flow (cfm) is supplied to the air conditioning pack.

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The pack valve is controled by three solenoids A, B, C.  Solenoid C is the OPEN/CLOSED solenoid. When it is electrically energized to the open position (or manually operated by pulling out on the manual control rod), the ballvalve actuating rod is retracted and latched.  Solenoid B regulates the LOW/HIGH flow mode. The solenoid is energized to the low flow mode.  Solenoid A is energized:  when the pack switch is at "HIGH",  the APU bleed switch is at the "ON" position and  the airplane is on the "GROUND". PACK VALVE CLOSED LIMIT SWITCH The closed position of the pack valve controls the following subsystems:  Mixing Valve drives to full cold.  Recirculation Fan may / may not activated. Note:

An unsatisfactory operation of the pack valve will affect the pressurization system. The AUTO FAIL circuit will be trigger (high cabin rate).

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Boeing 737-600/700/800/900 (CFM 56) subcat. B1.1

ATA 21 AIR CONDITIONING

PACK VALVE

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Boeing 737-600/700/800/900 (CFM 56) subcat. B1.1

ATA 21 AIR CONDITIONING

FCSOV — FUNCTIONAL DESCRIPTION PACK SWITCH OFF When the pack switch is in the OFF position, 28v dc (battery bus) energizes the close coil of solenoid C. With the close coil energized, the flow control and shutoff valve can not receive pressurized air to operate the actuator and open the valve. PACK SWITCH AUTO When the pack switch is in the AUTO position, 28v dc energizes the open coil of solenoid C. Solenoid C opens and lets air pressure go to the actuator to open the valve. This also opens the closed switch in the valve. Solenoid B energizes through the deenergized contact of the left low flow relay and the pack switch. The pack will operate in normal flow mode-cabin pressure will bias the flow rate of the auto flow servo to control the flow rate automatically. The right low flow mode relay energizes when all of these conditions are true:  Airplane in the air  Flaps are up  Left pack valve is closed. This will cause the right flow control and shutoff valve to operate in high flow mode. The operation is the same for the left flow control and shutoff valve if the right valve closes in flight with the flaps up. PACK SWITCH HIGH When the switch is in the HIGH position, the pack will operate in high flow mode. This will deenergize solenoid B. The deenergized solenoid B will let air flow to the APU / high flow servo. The valve actuator opens the valve plate which increases the airflow. The pack operates in the APU high flow mode when all of these conditions are true:  The pack switch is in the HIGH position  The APU bleed switch is in the ON position  The APU is operating above 95%  The airplane is on the ground. When these conditions are true, then solenoid A will energize to permit a flow rate greater than high flow mode. ISSUE 1, Rev. 1: 2015.07.10

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Boeing 737-600/700/800/900 (CFM 56) subcat. B1.1

ATA 21 AIR CONDITIONING

PACK FLOW CONTROL

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Boeing 737-600/700/800/900 (CFM 56) subcat. B1.1

ATA 21 AIR CONDITIONING

PACK PROTECTION PACK RESET The pack protection circuit stops operation of the pack to prevent damage to the air cycle machine and discomfort to the airplane passengers. NORMAL OPERATION The pack flow control and shutoff valve receives 28v dc, from the battery bus. The valve open solenoid receives 28v dc through the pack switch in the AUTO or HIGH position, and a de-energized pack overheat relay. This will electrically enable the flow control and shutoff valve (pack valve) to move to the open position. PACK TRIP

The overheat relay latches in the overheat position. When the condition that caused the pack trip off is corrected, push the TRIP RESET switch on the P5-10 panel to deenergize the overheat relay. TRAINING INFORMATION POINT If the PACK TRIP OFF light comes on and the pack can be reset, the heat exchangers may be obstructed or dirty. If the PACK TRIP OFF light comes on and the pack can not be reset, do a test of the compressor discharge and turbine inlet overheat switches. If a DUCT OVHT light comes on before a PACK TRIP OFF light, it can be a fault with the low limit (35F) sensor or the air mix valve.

 Pack protection is a function of these three switches:  Compressor discharge overheat switch  Turbine inlet overheat switch  Pack discharge duct overheat switch. The switches are normally open. When an overheat condition occurs, the overheat switch closes. This energizes the pack overheat relay. When the pack overheat relay energizes, power goes to the close solenoid of the flow control and shutoff valve. INDICATION  These are the indications when pack trip occurs:  PACK TRIP OFF amber light comes on  MASTER CAUTION and AIR COND annunciator lights come on.

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Boeing 737-600/700/800/900 (CFM 56) subcat. B1.1

ATA 21 AIR CONDITIONING

PACK PROTECTION

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Boeing 737-600/700/800/900 (CFM 56) subcat. B1.1

ATA 21 AIR CONDITIONING PACK VALVE

OPERATION Valve shutoff operation is accomplished by energizing solenoid "C" to seat the solenoid ball on the inlet pressure port, closing off the actuator air supply and venting the actuator. The actuator spring will move the disk to the closed position. When solenoid "C" is energized to seat the ball on the vent port and open the actuator supply pressure port, the valve actuator is supplied with air pressure for airflow control operation. The pressure is supplied from an upstream pressure port and is regulated to a desired value by the pilot regulator. Air then passes through the control orifice and increases pressure in the actuator chamber, moving the disk toward the open position. When the airflow increases to the desired valve, the selected flow servo bleeds off air through its ball valve at a rate that maintains the actuator pressure for the desired flow. The high flow servo is selected when solenoid "B" is deenergized, low flow is selected when solenoid "B" is energized. As cabin altitude increases, a bellows expands and biases the servo spring balance to produce a lower airflow rate. For APU operating on the ground, solenoid "A" is energized to allow inlet pressure to act on high flow servo. As the piston moves, control balance is biased to control at a higher airflow rate for maximum cooling. Electrical power, through the pack valve closed limit switch and valve close relay, will drive the mix valve full cold when the pack valve closes. Solenoid "C" is provided with a manual control to allow manual operation during ground maintenance.

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Boeing 737-600/700/800/900 (CFM 56) subcat. B1.1

ATA 21 AIR CONDITIONING

PACK VALVE SCHEMATIC

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Boeing 737-600/700/800/900 (CFM 56) subcat. B1.1

ATA 21 AIR CONDITIONING

HEAT EXCHANGER AND PLENUM / DIFF. ASSEMBLY FUNCTIONAL DESCRIPTION The heat exchanger (HX) removes heat from bleed/pack air. The plenum / diffuser assembly permits air to flow through the heat exchangers. Each pack system has a primary and a secondary heat exchanger. The heat exchanger has a large surface area that transfers heat from a heat source to a heat sink (ram air). LOCATION The primary heat exchanger is in the aft, outboard section of the air condition¬ing compartment. The secondary heat exchanger is forward of the primary heat exchanger. PHYSICAL DESCRIPTION The heat exchangers are an air-to-air, plate-fin, cross-flow type heat exchanger. Two isolated airstreams flow through thin walled channels. The channel walls are made up of plates and fins that increase surface area. The primary plenum/diffuser has an outer duct and an inner duct. The outer duct is the plenum and the inner duct is the diffuser. The inner duct has a fan bypass check valve. The fan bypass check valve is a hinged door assembly in the lower aft section of the diffuser. The primary pack assembly has these parts:  Primary heat exchanger  Primary plenum/diffuser  Fan bypass check valve. The secondary assembly has these parts:  Secondary heat exchanger  Secondary plenum/diffuser  Compressor discharge duct assembly  Air cycle machine.

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Air from the FCSOV flows through the primary heat exchanger. A cross flow of ram air removes heat before the air enters the ACM compressor inlet. When the airplane is on the ground, the ACM impeller fan makes a low pressure zone. This pulls air through the heat exchangers and up through the plenum to the impeller fan. Then the impeller fan sends the air through the diffuser and out the ram air exhaust. The air pressure in the diffuser keeps the check valve closed. When the airplane is in flight, ram air pressure opens the fan bypass check valve. The secondary heat exchanger takes air from the ACM compressor. The heat exchanger removes heat before the air goes to the ACM turbine section. TRAINING INFORMATION POINT You remove and install the primary or secondary pack assembly as a single unit. You attach the assemblies at attach points on the top surface. The outboard flange of the heat exchanger attaches the outboard structure of the air conditioning compartment. The heat exchanger efficiency decreases as dirt and contamination collect on the cooling surfaces. A RAM DOOR FULL OPEN light that stays on in flight can be an indication of a dirty heat exchanger The primary and secondary exhaust plenums have access panels for inspection and clean out.

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Boeing 737-600/700/800/900 (CFM 56) subcat. B1.1

ATA 21 AIR CONDITIONING

HEAT EXCHANGER

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Boeing 737-600/700/800/900 (CFM 56) subcat. B1.1

ATA 21 AIR CONDITIONING

RAM AIR DUCTS These are the two sets of ram air ducts for each pack system:  Ram air inlet  Ram air exhaust. The ram air inlet ducts let cooling air flow from the ram air inlet to the heat exchangers. The ram air exhaust ducts let air flow from the heat exchangers discharge overboard. LOCATION The ram air inlet ducts are outboard of the air conditioning compartment. They extend forward to the ram air inlet in the wing-to-body fairing. The ram air exhaust ducts are aft of the air conditioning compartments. You get access to the exhaust ducts from the air conditioning compartment. An inspection door is in the aft inlet duct at the aft end. TRAINING INFORMATION POINT There is a heat exchanger inlet inspection/clean-out panel in the inlet ducts. This permits access to the primary and secondary heat exchanger inlets. The access panel is in the lower area of the duct, adjacent and outboard of the heat exchangers. You get access to the ram air inlet duct through the fairing panels. They are outboard of the air conditioning doors. A special tool lets you clean the heat exchangers when they are dirty. You can repair the ducts if they have cracks or leaks.

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Boeing 737-600/700/800/900 (CFM 56) subcat. B1.1

ATA 21 AIR CONDITIONING

RAM AIR DUCTS

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Boeing 737-600/700/800/900 (CFM 56) subcat. B1.1

ATA 21 AIR CONDITIONING

RAM AIR INLET The ram air inlet modulation panel controls air flow into the ram air system for heat exchanger cooling. LOCATION The ram air inlet modulation panel is in the wing-to-body fairing forward of the air conditioning compartments. The modulation panel is in the inlet of the ram air inlet duct. PHYSICAL DESCRIPTION The ram air inlet modulation panel is made up of two panel sections. The two panels are hinged. The forward panel has a hinge at the forward end that connects to the airplane structure. The aft panel has rollers in tracks at the aft end. On the aft panel, clevis fittings on the mid section, and the upper surface, connect link arms to the shaft assembly. There is a ram air inlet modulation panel for the left and right ram air system. FUNCTIONAL DESCRIPTION The ram air inlet modulation panel and shaft assembly adjusts the quantity of air that goes into the ram air system. The ram air inlet controller and actuator supply the command and movement functions. The ram air inlet actuator moves the modulation panel. Linear movement of the actuator arm transmits movement through a link arm to the modulation panel shaft. The shaft turns link arms that lift or lower the two panels. The aft panel has rollers that let it move forward or aft as the two panels move up or down. The modulation panel and the ram air inlet deflector door are mechanically connected.

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Boeing 737-600/700/800/900 (CFM 56) subcat. B1.1

ATA 21 AIR CONDITIONING

RAM AIR MOD. PANEL

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Boeing 737-600/700/800/900 (CFM 56) subcat. B1.1

ATA 21 AIR CONDITIONING

RAM AIR INLET CONTROLLER The ram air control temperature sensor supplies temperature data to the ram air controller. LOCATION The ram air sensor is in the air conditioning compartment. It is in the duct that connects the compressor section of the ACM to the secondary heat exchanger. The ram air inlet controller is in the air conditioning compartment next to the water separator. PHYSICAL DESCRIPTION The ram air sensor has a stainless steel probe housing. The probe housing attaches to the electrical connector and is hermetically sealed. The housing has external threads and hexagonal flats for a boss mount. FUNCTIONAL DESCRIPTION The ram air sensor is a thermistor bead element. The resistance of the temperature sensing element changes as the air temperature changes. The ram air temperature controller uses the resistance of the temperature sensor in a con¬trol bridge. When the temperature is above or below 230F (110C), the control¬ler continues to change the position of the ram air inlet modulation panel. The controller does not send control signals when the temperature is approximately 230F (110C)

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Boeing 737-600/700/800/900 (CFM 56) subcat. B1.1

ATA 21 AIR CONDITIONING

RAM AIR CONTROL TEMPERATURE SENSOR

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Boeing 737-600/700/800/900 (CFM 56) subcat. B1.1

ATA 21 AIR CONDITIONING

RAM AIR FUNCTION FLIGHT (FLAPS NOT UP) The ram air system controls the airflow through the primary and secondary heat exchangers. These are the ram air control components:  Ram air inlet controller  Ram air inlet actuator  Ram air control temperature sensor  Ram air inlet deflector door  Ram air inlet modulation panel  Ram air ducts. These are the three modes of control for the ram air system:  Ground  Flight (flaps not up)  Flight cruise (flaps up). The air conditioning accessory unit (ACAU) relays control power to the ram air controller and the ram air actuator. There are separate control circuits for the left and right ram air systems. The left system is described. The right system operates the same. GROUND MODE When the airplane is on the ground, the AIR/GND sensing system supplies a discrete (ground) to energize the left air ground relay and the left ram mod control relay. A contact in the left ram mod control relay supplies 115v ac power through the energized air ground relay to the ram air actuator. The left ram air actuator has internal limit switches that connect power to the motor. The limit switch S1 per-mits power to the motor until the actuator is in the fully retracted position. This opens the modulation panel and extends the deflector door. When the actuator is in the fully retracted position, S1 opens to remove power to the motor. The deflector door is in the extended position when the actuator shaft is between limit switch positions S1 and S2. The limit switch, S3 (top contact), in the ram air actuator supplies a ground dis-crete to the air conditioning/bleed air controls panel. This causes the left RAM DOOR FULL OPEN light to come on.

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When K24 relay is de-energized, 115v ac power is supplied to the left ram air actuator. Power to the motor extend coils is through the S2 switch at takeoff. The deflector door moves out of the airstream when the actuator is at the S2 switch position. The left RAM DOOR FULL OPEN light will be on. FLIGHT (FLAPS UP) In flight, when the flaps are at the full up position, K23 relay de-energizes and 115v ac is supplied to the left ram air controller. The ram air controller reads temperature signals from the ram air control tem-perature sensor. The sensor sends signals from the air cycle machine (ACM) compressor outlet. The controller uses the air (temperature) sensor signal in a bridge circuit. The bridge circuit reads the ACM compressor temperature as an error signal, too hot or too cold. The nominal (balanced) control temperature is 230F/110C. The output sends a retract (too hot) signal through S3 or a (too cold) signal to extend the actuator through S4. The switch positions S3 and S4 in the actuator are the control limits for cruise mode. If the pack is shut down in flight, the ram air modulation panels fairs (closes) to decrease drag. TRAINING INFORMATION POINT If the DOOR FULL OPEN LIGHT is on during flight cruise mode, it may be one of these three possible problems:  The ram air system may have a blockage  The heat exchangers are dirty  Electrical failure

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Boeing 737-600/700/800/900 (CFM 56) subcat. B1.1

ATA 21 AIR CONDITIONING

RAM AIR SYSTEM SCHEMATIC

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Boeing 737-600/700/800/900 (CFM 56) subcat. B1.1

ATA 21 AIR CONDITIONING

RAM AIR MODULATION GROUND OPERATION When the airplane is on the ground, the air/ground sensing relays provide a ground for the circuit to the retract side of the actuator. If the modulating panel and exhaust louvers are not full open, they drive full open and the actuator position switches move to the positions shown. At the same time, switch 3 in the actuator completes a circuit for the RAM DOOR FULL OPEN light (blue). FLIGHT OPERATION When the airplane leaves the ground, the air/ground relay becomes deenergized but the ram modulating control relay remains energized due to flaps position. This completes a circuit to the extend side of the actuator through switch 2, and the actuator moves to position 2. At actuator position 2, the inlet modulating panel move to a slightly closed position. At this position the deflector door would have moved to the retracted position. After take-off, when the flaps are retracted, a circuit is completed to the ram air modulation controller. This circuit continues to extend the actuator. At position 3, the switch opens and extinguishes the RAM DOOR FULL OPEN light. From this point on, as long the flaps are up, the ram air controller will modulate the actuator between position 3 and position 4. The position of the actuator depends on the air temperature at the air cycle machine compressor discharge. The 110° C temperature sensor located on the air cycle machine compressor discharge duct signal the ram air controller to position the inlet modulation panel to maintain as close to 110°C as possible. In cruise, the actuator will modulate between position 3 and 4. Position 4 is with the inlet modulating panels nearly closed. During approach and landing, the ram air control system reverse the sequences noted for on the ground and take-off conditions.

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Boeing 737-600/700/800/900 (CFM 56) subcat. B1.1

ATA 21 AIR CONDITIONING

RAM AIR MODULATING SYSTEM SCHEMATIC

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Boeing 737-600/700/800/900 (CFM 56) subcat. B1.1

ATA 21 AIR CONDITIONING

AIR CYCLE MACHINE TRAINING INFORMATION POINT The air cycle machine (ACM) decreases air temperature, by expansion through a turbine. LOCATION The air cycle machine is in the air conditioning compartment. There is an ACM for each of the left and right pack systems.

You can cause damage to the air bearings if the shaft turns in the wrong direction. It is not necessary to do servicing of air cycle machines that have air bearings. The ACM is part of the secondary pack assembly. It has two clevis brackets for attachment to the structure in the air conditioning compartment.

PHYSICAL DESCRIPTION The air cycle machine is a high-speed rotating assembly. It has three sections connected by a common shaft:  Turbine  Compressor  Fan. Foil air bearings support the shaft. The air bearings permit the ACM to rotate at high speed with little friction. FUNCTIONAL DESCRIPTION The ACM makes air cool by rapid expansion. Rapid expansion of the air drives the turbine and compressor. Work is removed by the compressor and fan. Air from the pneumatic system goes into the compressor. The compressor increases the pressure and the temperature of the air. This increases the temperature differential in the secondary heat exchanger to improve heat transfer. The air then goes into the turbine section of the ACM. The fan impeller moves air through the ram air system when the airplane is on the ground. It pulls air in from the ram air inlet through the heat exchangers. It pushes air out through the ram air exhaust. This permits cooling airflow through the heat exchangers when the airplane is on the ground.

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Boeing 737-600/700/800/900 (CFM 56) subcat. B1.1

ATA 21 AIR CONDITIONING

AIR CYCLE MACHINE

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Boeing 737-600/700/800/900 (CFM 56) subcat. B1.1

ATA 21 AIR CONDITIONING

COMPRESSOR / TURBINE OVERHEAT SW The compressor discharge overheat switch and the turbine inlet overheat switch monitor the pack for an overheat condition. LOCATION There is a compressor discharge overheat switch and a turbine inlet overheat switch in each of the air conditioning compartments. The compressor discharge overheat switch is in the duct between the air cycle machine compressor section and the secondary heat exchanger. The turbine inlet overheat switch is in the duct from the secondary heat exchanger to the turbine section of the air cycle machine. PHYSICAL DESCRIPTION The overheat switches have these parts:  Electrical connector  Switch housing  Probe. The overheat switches look similar. The compressor discharge overheat switch closes at 390F/199°C and the turbine inlet overheat switch closes at 210F/99°C. The electrical connection is through a hermetically sealed connector. The housing has external threads and hexagonal wrench flats for a boss mount.

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Boeing 737-600/700/800/900 (CFM 56) subcat. B1.1

ATA 21 AIR CONDITIONING

COMPRESSOR DISCHARGE/ TURBINE INLET OVERHEAT SWITCH

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Boeing 737-600/700/800/900 (CFM 56) subcat. B1.1

ATA 21 AIR CONDITIONING

WATER SEPARATOR Cold air leaving the air cycle machine passes through a muff to the water separator. Moisture in the air at this reduced temperature begins to condense. The condensate is so finely atomized, however, that it follows along in the air stream. The water separator is used to separate, collect and remove the excess moisture from the air before it enters the distribution system. FEATURES The water separator is a cylindrical chamber consisting of an inlet and outlet shell assembly which houses a polyester coalescer, a conical-shaped metal coalescer support, a bypass valve assembly, and a valve support guide. A coupling joins the inlet and outlet shell assemblies and secures the coalescer support. The outlet shell assembly contains a collection chamber, a baffle, a water spray extractor boss, and an overboard water drain. A boss is provided for the installation of the 2°C sensor. A bag condition indicator is also included which consists of a spring loaded piston and disk enclosed in a housing and a color coded cap. OPERATION The coalescer bag and its support are conically shaped with the small diameter at the upstream end. The support fits inside the bag and has louvers shaped to impart a whirling motion to air as it passes through. Air enters the separator around the outside of the bag, passes through the bag, then through the louvers. As the damp air passes through the bag, the bag is wetted and larger droplets of water are formed. These droplets along with the air are caused to whirl by the louvers of the support. As the air and moisture pass through the separator the centrifugal force keeps the heavier moisture close to the inside of the support unit it reaches the collection chamber. A cylindrical baffle approximately the diameter of the outlet

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duct extends inside the separator at the downstream end. The water and air whirling in a greater diameter than the baffle find it necessary to make a double reverse turn in order to leave the separator. The turning does not appreciably affect airflow but the water being much heavier cannot make the turn and remains in the collection chamber. An overboard drain mates to an outlet in the equipment bay door. The bypass valve allows air to pass through the water separator to the distribution system without first passing through the coalescer bag. The valve opens as a result of increased pressure differential should the coalescer bag become clogged or frozen. The water separator also has a bag condition indicator. As the bag becomes clogged, the pressure applied to the bag condition indicator piston is increased, forcing the disk on the piston shaft toward the red colored window section of the indicator cap. When the disk is positioned within the red colored portion of the cap, its indicates a dirty bag and the bag should be replaced. WATER SPRAY INJECTOR The water spray injector adds water into the ram air system. This increases the efficiency of the heat exchangers. The air from the turbine section of the ACM supplies airflow through the water spray nozzle. Water from the water separator flows perpendicular to the airflow at a venturi. This causes suction of water into the airstream. When the water and air mix, the force breaks the water into microscopic droplets (atomize). The atomized mixture flows into the ram air duct upstream of the heat exchanger. The mixture increases the heat exchanger's ability to remove heat.

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Boeing 737-600/700/800/900 (CFM 56) subcat. B1.1

ATA 21 AIR CONDITIONING

WATER SEPARATOR

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Boeing 737-600/700/800/900 (CFM 56) subcat. B1.1

ATA 21 AIR CONDITIONING

2° C ANTI ICE CONTROL SYSTEM A minimum temperature control system 2°C (35°F) prevents freezing of condensed moisture. FEATURES When cooling requirements are high, the temperature of the air at it leaves the air cycle machine may drops below the freezing point of water. The water separator 2°C control system regulates air temperature into the separator to keep moisture from freezing on the water separator coalescer bag. The water separator 2°C control system consists of a  2°C control sensor,  2°C controller,  2°C control valve. The sensor is located on the right forward side of the water separator, the control is mounted to the outboard side of the equipment bay near the forward end of the bay, and the valve is located forward of the air cycle machine in the air cycle machine by-pass duct.

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Boeing 737-600/700/800/900 (CFM 56) subcat. B1.1

ATA 21 AIR CONDITIONING

2° C ANTI ICE VALVE AND SENSOR

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Boeing 737-600/700/800/900 (CFM 56) subcat. B1.1

ATA 21 AIR CONDITIONING

2° CONTROLLER BITE The control unit has Built In Test Equipment (BITE). Instructions for testing are on the side of the control box. The unit has a green light for "GO", a red light for "NO GO", and a rotating-type test switch. A placard on the cover gives test instructions. You must put the switch in the FLIGHT position after you do the test. The switch is spring-loaded to the FLIGHT position. You enable the BITE test when you move the selector switch to any of the other positions. The positions of the switch are for the followings tests: POSITION TEST  1 Amplifier Controller Position 1 is a test of the dc power supplies. This test makes sure the basic fault detection circuit of the BITE function operates.  2 Valve Opens Position 2 test the open drive (heat) command for the low limit valve. You can monitor the low limit valve as it moves to the open position.  3 Dead Band in Controller (1.1°-2.2°C) Position 3 test the deadband. The controller makes sure that the valve will not move when the deadband is simulated.  4 2° Valve Closes Position 4 test the close drive (cold) command for the low limit valve. You can monitor the low limit valve as it moves to the close position.  5 Temperature Sensor for Open and Short Circuits Position 5 is a test of the sensor. This test makes sure the sensor does not have an open or short.

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Boeing 737-600/700/800/900 (CFM 56) subcat. B1.1

ATA 21 AIR CONDITIONING

2° C ANTI-ICE CONTROLLER

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Boeing 737-600/700/800/900 (CFM 56) subcat. B1.1

ATA 21 AIR CONDITIONING

2° C ANTI ICE CONTROL SYSTEM FUNCTIONAL Keeping water separator temperature above freezing is accomplished by taking hot air from upstream of the air cycle machine compressor and routing it back into the system at the muff at the air cycle machine turbine discharge. The water separator 2°C control system regulates the quantity of air being by-passed. The low limit controller selector has six positions. The FLIGHT position is for normal control. The other positions are for the BITE test. The FLIGHT position enables the control and modulation circuits to operate the valve to control the air temperature to 35F (1.7°C). The Low Limit controller uses 115v ac, single phase power for operation. It reads the temperature sensor resistance as part of a bridge circuit. The controller balances the bridge circuit by the adjustment of the water separator air temperature. The controller sends an open signal to the valve when the air temperature is less than 34F (1.1 °C). It sends a close signal to the valve if the air temperature is more than 36F (2.2 °C). The controller does not send a signal when the air temperature is in the deadband range, 34F (1.1 °C) to 36F (2.2°C).

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Boeing 737-600/700/800/900 (CFM 56) subcat. B1.1

ATA 21 AIR CONDITIONING

2° C ANTI ICE CONTROL

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Boeing 737-600/700/800/900 (CFM 56) subcat. B1.1

ATA 21 AIR CONDITIONING

21-60 TEMPERATURE CONTROL TEMPERATURE CONTROLLER The electronic control system automatically controls pack output temperature in response to the temperature selector and sensed cabin temperature. Controlling the cabin temperature is accomplished by controlling the proportion of hot and cold air coming from each pack. When the air conditioning packs are operating, all temperature control and overheat protection circuits are activated. An air mix valve, downstream of the pack valve, regulates cabin temperature by allowing a controlled amount of hot air to by-pass the air cycle system. This air is recombined in proper proportions with cold air at the mix chamber. The position of the mix valve depends on signal from the temperature control system. The pack switch must be in the AUTO or HIGH position to have electrical power to the temperature selector and temperature control system.

The purpose of the dual channel regulator is to control output of both packs in response to the control cabin and passenger cabin selectors. It drives the mix valves toward hot or cold to maintain an actual cabin temperature (sensed) equal to desired (selected). The regulator receives the following signals: LEFT PACK

RIGHT PACK

control cabin temp, selector control pass, cabin temp, selector pass, cabin temp. sensor duct anticipator cabin temp. sensor duct anticipator sensor 60°C duct limit sensor sensor 60°C duct limit sensor CABIN TEMPERATURE SENSOR

TEMPERATURE SELECTOR The control and passenger cabin temperature selectors are identical unit mounted on the forward overhead panel. The face dial is divided into an AUTOMATIC and MANUAL range. The left temperature selector controls the control cabin temperature. The right temperature selector controls the temperature of the passenger cabin. The temperature selector has two modes:  MANUAL In the manual position, the selector provides direct control of the mix valve. In MANUAL, turning the knob clockwise to COOL causes one of the cams to close a switch connected to the mix valve actuator motor, and operate the valve to increase the proportion of cold air passing through the valve. Turning the knob counterclockwise to WARM causes the cam to close a switch connected to the mix valve actuator and operate the valve to increase the proportion of warm air passing through the valve.  AUTO In the automatic position, the temperature selector provides the selected input signal to the temperature regulator for cabin temperature control.

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The control and passenger cabin temperature sensor measured the actual cabin temperature. This temperature is delivery to the temperature controller. An in-line fan downstream of the sensor draws air from the cabin across the sensor. DUCT ANTICIPATOR SENSOR The duct anticipator sensor in the main distribution manifold prevent delivery of excessively hot or cold air to the cabin. It also assists to prevent overshooting and hunting of the temperature control system when a new temperature is selected.

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Boeing 737-600/700/800/900 (CFM 56) subcat. B1.1

ATA 21 AIR CONDITIONING

60°C DUCT LIMIT SENSOR The 60°C duct limit sensor is only used in the auto mode. If 60°C is sensed in the limit circuit, the controller drives the mixing valve toward cold. OVERHEAT PROTECTION CIRCUITS Overheat protection circuits protect the pack against duct overheat. Each pack has the following circuits:  90°C SUPPLY DUCT mixing valve drives to FULL COOL.  120°C SUPPLY DUCT pack valve closes. AIR CONDITIONING ACCESSORY UNIT The air conditioning accessory unit include the pack valve closed relay, 90°C duct overheat relay and pack trip relay.

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Boeing 737-600/700/800/900 (CFM 56) subcat. B1.1

ATA 21 AIR CONDITIONING

TEMPERATURE CONTROL SYSTEM SCHEMATIC

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Boeing 737-600/700/800/900 (CFM 56) subcat. B1.1

ATA 21 AIR CONDITIONING

TEMPERATURE SENSORS The passenger compartment duct temperature anticipator sensor is in the passenger overhead distribution duct.

DUCT LIMIT SENSOR The duct temperature limit sensor supplies a signal to the cabin temperature controller (CTC) when the DUCT temperature is 140F (60C).

PHYSICAL DESCRIPTION The duct temperature anticipator sensor has a probe body and an electrical connector end. The sensor is hermetically sealed with two elements.

LOCATION The flight compartment duct temperature limit sensor is in the flight compart-ment distribution supply duct. The supply duct is in the EE compartment. The passenger compartment duct temperature limit sensor is in the passenger overhead distribution duct. PHYSICAL DESCRIPTION The duct sensor has a probe body and an electrical connector end. The sensor is hermetically sealed in a metal housing.

FUNCTIONAL DESCRIPTION The duct temperature anticipator sensor is a variable-resistance type. As tem-perature increases, the resistance of the sensor decreases. The duct temperature anticipator sensor is part of a bridge circuit in the CTC. It reads the rate of change in the duct air temperature. The CTC uses this data to adjust the air mix valve position. DUCT OVERHEAT SWITCH The duct overheat switch 190F (88°C) turns on the DUCT OVERHEAT light and causes the air mix valve to close the hot side of the valve.

FUNCTIONAL DESCRIPTION The duct temperature limit sensor is a variable-resistance type. As temperature increases, the resistance of the sensor decreases. The duct limit sensor is part of a bridge circuit in the CTC. The CTC sends a close signal to the air mix valve when the air temperature in the duct is 140F (60°C) or more.

LOCATION The flight compartment duct overheat switch is in the flight compartment dis-tribution supply duct. The supply duct is in the EE compartment. The passenger compartment duct overheat switch is in the passenger overhead distribution duct.

DUCT ANTICIPATOR SENSOR PHYSICAL DESCRIPTION The duct temperature anticipator sensor supplies the cabin temperature controller (CTC) with rate of temperature change (increase or decrease). LOCATION

The duct overheat switch has a probe body, electrical connector, and flange. A bimetal element that is normally open is in the duct overheat switch.

The flight compartment duct temperature anticipator sensor is in the flight compartment distribution supply duct. The supply duct is in the EE compartment. ISSUE 1, Rev. 1: 2015.07.10

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Boeing 737-600/700/800/900 (CFM 56) subcat. B1.1

ATA 21 AIR CONDITIONING

TEMPERATURE CONTROL SENSORS

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Boeing 737-600/700/800/900 (CFM 56) subcat. B1.1

ATA 21 AIR CONDITIONING

TEMPERATURE CONTROL OPERATION Operation Cabin temperature may be adjusted either by a manual or automatic control system. Both systems utilize 115 volt ac current to adjust the mix valve so that air of the desired temperature is directed into the airplane distribution system. Circuit breakers are provided for temperature control system circuit protection. The PACK VALVE circuit breaker and the OVERHEAT circuit breaker provide protection during both manual and automatic control operation, the MANUAL TEMP CONT circuit breaker protects during manual operation, and the LEFT and RIGHT AUTO TEMP CONT circuit breakers protect during automatic control operation. When air conditioning switches are turned ON the pack valves open and air from the pneumatic system is ducted through the mix valves to the air cycle system and the mixing chamber. The mix valves adjust to allow the proper proportion of cold air from the air cycle system and hot air from the pneumatic system to enter the distribution system for a selected cabin temperature. Manual control requires monitoring of the passenger cabin and supply duct temperature indicator while adjusting the mix valve position to obtain and hold the desired cabin temperature. With the air conditioning switches ON, 115 volt ac current is provided to three switches in the cabin temperature selector.

A 90°C duct overheat thermal switch gives system protection to prevent adjust-ment of the mix valve such that air entering the cabin becomes too hot. At ap-proximately 90°C the thermal switch closes, energizing the cabin duct overheat relay. The energized relay completes a circuit to move the mix valve to the full cold position. The thermal switch, when closed, also completes a circuit to illu-minate the DUCT OVERHEAT light. After correcting the overheat condition the system may be returned to normal. Another thermal switch protects against duct overheat should control power be lost. At approximately 120°C this switch closes to energize the pack overheat relay and complete a circuit to close the pack valve and illuminate the PACK TRIP OFF light. Return to normal after a trip off requires pushing the PACK RESET switch after the condition has been corrected.

MANUAL CONTROL When the pack switch is in the AUTO or HIGH position, 115v ac goes to the temperature selector. The selector is spring-loaded to the OFF position. When you hold the selector to the WARM or COOL position, 115v ac goes through the ACAU to the air mix valve. If the selector knob is in the MANUAL OFF position all three switches are open. Moving the knob to COOL closes one of the switches and the circuit is completed to move the mix valve such that more air is passed through from the air cycle system and less from the pneumatic system. Moving the knob to WARM closes a different switch moving the valve in the opposite direction. Only one of the switches in the selector can be closed at a particular time.

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Boeing 737-600/700/800/900 (CFM 56) subcat. B1.1

ATA 21 AIR CONDITIONING

TEMPERATURE CONTROL MANUAL MODE

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Boeing 737-600/700/800/900 (CFM 56) subcat. B1.1

ATA 21 AIR CONDITIONING

AUTOMATIC CONTROL TRAINING INFORMATION POINT When the selector knob is moved to AUTO the third switch closes and a circuit is completed to the temperature regulator. Setting the knob pointer for a particular cabin temperature adjusts a potentiometer fixed to the knob shaft. This potentiometer serves as a reference resistance in the regulator temperature control bridge. The cabin temperature sensor provides the resistance in the other leg of the bridge. If cabin temperature is already the same as that asked for by the selector, the controller will prevent any current passing on to the mix valve. At a cabin temperature other than that selected the temperature sensor will provide a resistance either higher or lower in the other leg of the control bridge. As a result the controller will move the mix valve either toward hot or cold, as required, to bring cabin temperature to the required air temperature to slow down changes requested by the controller and prevent duct overheat. The controller moves the mix valve so that cabin temperature changes without sudden blasts of cold or hot air and without raising duct temperature above limits. The same system overheat protection described under manual control is in effect during automatic control.

Caution: DO NOT USE AN OHMMETER FOR A CONTINUITY CHECK OF THE TEMPERATURE SENSORS DURING THE TEST. THE OHMMETER CAN DAMAGE THE THERMISTOR ELEMENTS OF THE TEMPERATURE SENSORS BEYOND REPAIR.

SENSOR DESCRIPTION The duct limit sensor and duct anticipator are variable-resistance type. As temperature increases, the resistance of the sensor decreases. The duct limit sensor is part of a bridge circuit in the CTC. The CTC sends a close signal to the air mix valve when the air temperature in the duct is at or above 130F (60°C). The duct anticipator is part of a bridge circuit in the CTC. It reads the rate of change in the duct air temperature. The CTC uses this data to adjust the air mix valve position. The duct overheat switch is a bimetal element. The contacts in the switch are normally open. As temperature increases to the activation temperature, the switch contacts close to complete a circuit. The duct overheat switch causes the air mix valve to close when the air temperature is above 190F (90°C). The closed switch causes the DUCT OVHT light, on the P5-17 panel, to come on.

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ATA 21 AIR CONDITIONING

TEMPERATURE CONTROL AUTO

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ATA 21 AIR CONDITIONING

CABIN TEMPERATURE CONTROLLER Control and passenger cabin automatic temperature regulation is obtained from a single unit located in the electronic compartment. This unit contains all parts of each regulation system which are not required to be mounted remotely. Separate identical networks are enclosed for each cabin. The regulator receives signal from the temperature selectors, cabin temperature sensors, and duct temperature sensors. It drives the mix valves toward hot or cold to maintain an actual cabin temperature (sensed) equal to desired (selected). BITE A built-in test circuit in the temperature controller provides a quick electrical check of temperature control system components. A rotary test switch, two sets of "GO", "NO GO" lights and a test instruction decal are provided on the face of the controller. When the temperature control system is not being tested the switch must be returned to START position. The following components can be tested:  Control box  Cabin sensor  Anticipator sensor  60°C duct limit sensor  Temperature selector

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ATA 21 AIR CONDITIONING

CABIN TEMPERATURE CONTROLLER

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ATA 21 AIR CONDITIONING

AIR CONDITIONING ACCESSORY UNIT The air conditioning accessory unit (ACAU) is the interface of the airplane1 s operational logic and the air systems. LOCATION The ACAU is in the EE compartment on the E4-1 rack. INTERFACES The air conditioning accessory unit has an interface with these systems:  Flight controls (flaps not up switch)  Landing gear (air/ground)  Engine starting  Air conditioning  Pneumatic/bleed air  Flight management computer (FMC).  The ACAU receives signals from these airplane components:  Engine start valves  Flap control unit  Air/Gnd relays  Pack flow control and shutoff valve  Ram air actuator/controller  Pack overheat switch  Air mix valves  Cabin temperature controller  Engine bleed switch  Duct overheat switch  Pneumatic system valves  P5-10 panel  P5-17panel  Pressurization outflow valve  Recirculation fan  Overboard exhaust valve  Pneumatic system ovht / overpress. switch  FMC.

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The ACAU outputs signals to these components:  P5-10 panel  P5-17panel  Bleed air regulator  Eng start valve  Pack flow control and shutoff valve  Ram air inlet controller  Ram air inlet actuator  Cabin temperature controller  Air mix valves  Outflow valve  Recirculation fan  EE cooling fans  FMC. TRAINING INFORMATION POINT You must do an adjustment/test after you remove the ACAU (AMM Part 2, 21-51).

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ATA 21 AIR CONDITIONING

AIR CONDITIONING ACCESSORY UNIT

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ATA 21 AIR CONDITIONING

CABIN TEMPERATURE SENSOR The control cabin temperature sensor is located behind a screened opening in the ceiling, approximately 4 inches left of center, at station 259. An in-line fan downstream of the sensor draws air from the control cabin across the sensor. The control cabin sensor fan is activated by switching the pack switch to "AUTO" or "HIGH". The passenger cabin temperature sensor is installed inside a duct located below the stowage compartment. An in-line fan downstream of the sensor draws air from the cabin across the sensor. TRAINING INFORMATION POINT There is a filter located behind a screened opening. If this filter is clogged, the temperature sensor regulates a lower cabin temperature. The lower temperature depends on the clog status of the filter.

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ATA 21 AIR CONDITIONING

PASSENGER AND CONTROL CABIN SENSORS

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ATA 21 AIR CONDITIONING

CABIN TEMPERATURE SENSOR FAN The flight compartment temperature sensor fan comes on when 115v ac is available and the left pack switch is in AUTO or HIGH. The passenger compartment temperature sensor fan comes on when 115v ac is available.

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ATA 21 AIR CONDITIONING

PASSENGER AND CONTROL CABIN SENSOR FAN

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Boeing 737-600/700/800/900 (CFM 56) subcat. B1.1

ATA 21 AIR CONDITIONING MIXING VALVE

The mix valve controls pack output temperature by directing airflow through the cooling pack or around the cooling pack to the mix chamber. The hot and cold air mixed proportionally to satisfy cabin temperature requirements. The mix valve consists of two butterfly valves operated by the same actuator through a common shaft. The 115 volt ac actuator mounts on a flange of the hot valve to drive the common shaft. When the hot valve butterfly is full open the cold valve is full closed and vice versa. As the hot valve moves toward close, the cold valve moves proportionally toward open. A position potentiometer is connected to the opposite end of the shaft from the actuator to permit monitoring the valve position from the control cabin. A visual indicator is also located at the actuator between the potentiometer and the cold valve body. Limit switches in the actuator housing interrupt current to the actuator monitor at either extremity of travel. The mix valve is located in the air conditioning equipment bay inboard of the heat exchangers. If the pack valve is closed, the mixing valve drives to the "FULL COOL" position.

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ATA 21 AIR CONDITIONING

MIXING VALVE

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ATA 21 AIR CONDITIONING

AIR MIX VALVE POSITION INDICATOR The air mix valve position indicator shows the amount of opening of the hot and cold valve ports. LOCATION The position indicator is in the cabin temperature controls (P5—17) module.-There is one indicator for each of these systems:  CONT CABIN (left air conditioning system)  PASS CABIN (right air conditioning system) PHYSICAL DESCRIPTION The position indicator has these parts:  Electrical connection  Cylindrical housing  Dial display  Needle indicator. The dial display has a graduated scale that scans a 110 degree area. The scale has no units. FUNCTIONAL DESCRIPTION The air mix valve position indicator receives 28v dc, when bus 2 has power. It shows air mix valve position if the pack system is on or off. The indicator needle moves as a function of current from the mix valve position transmitter. The transmitter sends a current in proportion to the mix valve position. The current makes a magnetic field that moves the needle. The needle is at the COLD position when the air mix valve opens the cold valve port. It moves to the HOT position as the hot valve port opens. The needle shows in the center when both valves are open equally. TRAINING INFORMATION POINT The COLD and HOT labels are part of the panel, not the indicator. A ring clamp on the outside diameter holds the air mix valve position indicator in position. ISSUE 1, Rev. 1: 2015.07.10

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ATA 21 AIR CONDITIONING

MIX VALVE POSITION INDICATOR

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ATA 21 AIR CONDITIONING

CABIN TEMPERATURE MODULE PRINTED CIRCUIT ASSEMBLY The cabin temperature module printed circuit assembly makes sure the power is stable for the indicators in the cabin temperature module. LOCATION The cabin temperature module printed circuit assembly is in the cabin temperature module. You remove the cabin temperature module to get access to the printed circuit assembly. PHYSICAL DESCRIPTION The printed circuit assembly is a circuit card. There are electrical contacts on the printed circuit assembly that attaches to the temperature control module connector. FUNCTIONAL DESCRIPTION The printed circuit assembly receives 28v dc. The circuit makes sure the voltage and current for the air mix valve position indicator and transmitter are stable.

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ATA 21 AIR CONDITIONING

CABIN TEMPERATURE MODULE

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ATA 21 AIR CONDITIONING

TEMPERATURE INDICATING The temperature indicating system permits monitoring passenger cabin temperatures and passenger supply air temperature from the control cabin. FEATURES The temperature indicating system includes a temperature indicator, an AIR TEMP selector, and two temperature bulbs. When power is supplied to the 28 volt dc bus 1 and the TEMPERATURE INDICATION circuit breaker is closed, the selected temperature will be indicated. TEMPERATURE BULBS Each temperature bulb contains an element whose resistance varies with changing temperature. A bulb is installed in the supply duct and with the passenger cabin temperature sensor below the stowage compartment in the forward cabin. An in-line fan downstream of the bulb draws air from the cabin across the bulb. OPERATION Passenger cabin air supply and passenger cabin temperatures may be monitored by the temperature indicator on the forward overhead panel. The temperature is indicated according to the position of the AIR TEMP selector. The AIR TEMP selector switch permits switching between supply duct and passenger cabin temperature indication.

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ATA 21 AIR CONDITIONING

TEMPERATURE INDICATING SYSTEM

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ATA 21 AIR CONDITIONING

21-20 DISTRIBUTION VENTILATION The A/C distribution system supplies conditioned air to the passenger and flight compartments. The main air distribution system gets air from these sources:  Air conditioning packs  Ground conditioned air  Recirculation system. The main distribution manifold collects and mixes air from any combination of the sources.

The ventilation system uses differential pressure to pull air out of the airplane. The air moves through overboard vents from the cabin galley and the lavatory areas. EQUIPMENT COOLING SYSTEM The equipment cooling system removes heat from the equipment in the main equipment center and the flight compartment.

FLIGHT COMPARTMENT DISTRIBUTION The flight compartment gets conditioned air from the left pack and the main distribution manifold. A duct on the left side of the airplane transmits the air. The flight compartment has supply ducts and outlets to control the airflow at each station. PASSENGER COMPARTMENT DISTRIBUTION The passenger conditioned air distribution gets air from the main distribution manifold. The air goes through riser ducts and up sidewalls to an overhead distribution duct. Outlets along the sidewalls and the center of the ceiling divide the air for symmetrical supply. RECIRCULATION SYSTEM The recirculation system uses a fan to move air from the passenger compartment to the main distribution manifold. This system reduces the amount of air that the packs need to supply.

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ATA 21 AIR CONDITIONING

DISTRIBUTION GENERAL

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ATA 21 AIR CONDITIONING

OVERHEAD DISTRIBUTION DUCT The overhead distribution duct divides the supply of conditioned air to outlets along the center and sidewalls of the passenger cabin for a symmetrical balance of airflow. LOCATION The overhead distribution duct is in the center ceiling area of the passenger compartment. PHYSICAL DESCRIPTION The overhead distribution duct is a cylindrical composite tube. There are outlets along its length that attach to riser ducts and flexible sidewall ducts. The fittings, in the area where the sidewall riser ducts attach, permit the attachment of temperature sensors. TRAINING INFORMATION POINT You get access to the overhead distribution duct through the ceiling panels in the passenger cabin. Mounting screws attach the diffuser outlet assembly to the overhead distribution duct. Duct brackets attach the overhead distribution duct to the ceiling supports. Flexible ducts connect the overhead distribution duct to the sidewall outlets and the sidewall riser ducts.

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ATA 21 AIR CONDITIONING

PASSENGER CABIN OVERHEAD DISTRIBUTION

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ATA 21 AIR CONDITIONING

GALLEY VENTILATION The galley ventilation muffler decreases noise levels as air flows out of the galleys. GENERAL The ventilation system uses differential pressure, cabin—to—ambient, to remove air by suction. The system uses these components to take air out of the galley:  Galley vent inlet  Flexible ducts  Galley ventilation muffler  Exhaust nozzle. The flexible ducts connect the vent inlet opening in the galley ceiling to an exhaust nozzle in the airplane skin. The galley ventilation muffler reduces the noise of air being released from the pressurized cabin. LOCATION The galley ventilation muffler is in the ceiling area above the galley. TRAINING INFORMATION POINT Air velocity through the galley ventilation muffler will increase if the muffler shell has contamination or cracks. This may cause noise levels to increase.

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ATA 21 AIR CONDITIONING

GALLEY VENTILATION

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ATA 21 AIR CONDITIONING

MAIN DISTRIBUTION MANIFOLD The distribution manifold receives conditioned air from both packs, filtered recirculated air from the recirculation fan, or an external conditioned air source routes it through two risers to the passenger cabin overhead distribution system. The control cabin air is supplied from the left pack output duct upstream of the mixing and distribution manifold. Sensors in this duct provide overheat protection, indication, and control reference for the left pack. GROUND SERVICE CONNECTION A ground service connection is provided to allow use of a ground service cart for conditioned air to the cabin when airplane air conditioning is off. A check valve in the duct prevents loss of air when airplane air conditioning is on. The connection is a short duct section which is fastened to the pressure skin and the duct and check valve assembly at its upper flange and has two slotted holes in its lower flange to match fasteners on the ground service cart. An access door must be opened to make the connection. A swing check valve in the duct and check valve assembly opens with pressure from the ground service cart and closes when air is being supplied from the airplane air conditioning system. RECIRCULATION FAN A recirculation system is installed to provide ventilation while minimizing bleed air requirements. An electrically blower draws cabin air through filters and discharges into the mixing and distribution manifold. The system recirculates approximately 23,5 m3/min (830 cubic feed /min). The recirculation fan is energized if:  Recirculation fan switch in AUTO and  one or both pack valves "CLOSED",  or both packs operating in LOW FLOW mode (55 lbs/min).

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ATA 21 AIR CONDITIONING

MAIN DISTRIBUTION MANIFOLD

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ATA 21 AIR CONDITIONING

RECIRCULATION FAN FUNCTIONAL DESCRIPTION Power for the recirculation fan is 115v ac from main bus 2. The control power comes from DC bus 2. The circuit breakers are on the P6 panel. The R331 relay enables power to the fan when control authority is in the correct sequence. Control authority of the fan has two levels. The highest level of authority are these switches:  RECIRC FAN switch (P5 panel)  Recirculation fan overheat switches (in the fan field coils). To enable the second level of authority, the RECIRC FAN switch is in the AUTO position and the fan temperature is normal. The second level of authority is the relay logic in the air conditioning accessory unit (ACAU). This logic looks at pack flow conditions. If one (L or R) of the pack valve closed relay is energized, the recirculation fan operates to increase cabin ventilation. If both (L and R) of the pack valves have their normal relays energized, the recirculation fan operates. TRAINING INFORMATION POINT The recirculation fan switch bypass relay is normally energized when there is battery bus power. This relay removes power from the bypass circuit for the recirculation fan. The air conditioning overboard exhaust valve reconfig cont circuit breaker is for unpressurized dispatch. If the circuit breaker is open, the bypass circuit enables the recirculation fan to operate if the smoke control relay energizes.

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ATA 21 AIR CONDITIONING

RECIRCULATION SYSTEM SCHEMATIC

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ATA 21 AIR CONDITIONING

FLIGHT COMPARTMENT COND. AIR DISTRIBUTION LOCATION The left air conditioning pack supplies the conditioned air for the flight compart-ment. The air flows through ducts that go forward along the left side of the air-plane. The flight compartment distribution uses different ducts than the passen¬ger compartment distribution. The flight compartment receives conditioned air from the right pack if the left pack is not operational. The flight compartment distribution lets the flight crew select a different air tem-perature than the other areas of the airplane. The air quality is better because it comes from the left pack and is not mixed with recirculated air.

The windshield outlets are forward of the captain' s and first officer's glareshield. They supply airflow up and along the windshield plane. The windshield and foot air outlet valves are forward of the rudder pedals. The foot air outlets are inside the captain's and first officer's rudder pedal housings. To get access to the valves you must remove the respective display unit (captain's or first officer's) PHYSICAL DESCRIPTION

FLIGHT COMPARTMENT DISTRIBUTION The flight compartment has these captain's and first officer's diffusers and outlets:  Overhead outlets and gasper  Underseat diffusers  Foot air diffusers (2)  Windshield air diffusers (2)  Individual panel gaspers (2)  Sidewall outlets (shoulder warmers). You can adjust the overhead outlets airflow direction with a moveable baffle. Airflow cannot be shut off. The air distribution supply ducts in the flight compartment include metering ori-fices and mufflers. The metering orifices control flow. The mufflers decrease air noise.

There are two segmented disks inside the windshield and foot air outlet valve housing. The disk position controls airflow from the valve. The segmented disk connects to the air outlet valve control cable to change the disk position. OPERATION The captain's and first officer's windshield and foot air outlet valves have manual control. The controls are on the lower portion of the P1 and P3 panels. The controls are WINDSHIELD AIR and FOOT AIR. They attach to push-pull control cables. The control cables turn the segmented disks inside the valves. You pull the knob to open the valve.

WINDSHIELD AIR/FOOT OUTLET VALVE The windshield and foot air outlet valves control airflow to the captain's and first officer's windshield outlets and foot outlets.

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ATA 21 AIR CONDITIONING

FLIGHT COMPARTMENT AIRFLOW

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ATA 21 AIR CONDITIONING

PASS. CABIN COND. AIR DISTRIBUTION CARGO COMPARTMENTS The passenger cabin conditioned air distribution system divides the flow of conditioned air to the passenger cabin. The passenger cabin conditioned air distribution system uses these components:  Sidewall riser ducts  Overhead distribution ducts  Flexible hoses  Diffuser outlets. Conditioned air from the main distribution manifold flows through sidewall riser ducts. The ducts follow the airplane contour along the right and left fuselage. The riser ducts supply the overhead distribution duct. This duct goes longitudi¬nally along the top center of the passenger cabin. Conditioned air flows through the overhead distribution duct to the center and sidewall diffusers. It supplies the main passenger areas, the galleys, and the lavatories. The passenger cabin exhaust air flows through floor grilles.

The cargo compartments receive heat from equipment cooling exhaust and passenger compartment air. Warm equipment cooling exhaust air flows under the forward cargo compartment floor and along the sidewalls. The air mixes with passenger compartment air in the main distribution manifold. The aft cargo compartment air comes from the passenger compartment through the foot level grilles. The air goes into the sidewall area around and under the aft cargo compartment through the outflow valve. The warm air on all sides of the cargo compartments is an insulator. It prevents the transfer of heat through the skin by conduction. SUPPLEMENTAL HEATING In the passenger compartment, door area heaters supply more heat around the two main entry doors.

HEATING SYSTEM The heating system supplies warm air to areas to prevent freezing or to in¬crease temperature for comfort. These are the parts of the heating system:  Forward cargo compartment heating  Aft cargo compartment heating  Supplemental heating.

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ATA 21 AIR CONDITIONING

PASSENGER CABIN AIRFLOW

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ATA 21 AIR CONDITIONING

DOOR AREA HEATER The door area heaters supply added heat to prevent cold zones around the doors. LOCATION The forward door area heater is on the left outboard side of the nose wheel well. Remove the aft left access panel from inside the nose wheel well to get access to the heater. The aft door area heater is in the center ceiling area in the aft passenger compartment. The overwing escape door heaters are behind the lining, close out panel, and the door trim. The overwing emergency escape hatch door heaters are surface electric heater. PHYSICAL DESCRIPTION The door area heaters are electrical heat elements in a cylindrical housing. There is an electrical connector on the housing. Flexible hoses connect conditioned air distribution supply ducts to the door area heaters. A flexible hose connects the outlet side of the heater to a fitting at the base of the door. The forward door heater uses conditioned air from the flight compartment distribution supply. The aft door heater uses conditioned air from the aft passenger compartment distribution supply ducts.

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ATA 21 AIR CONDITIONING

DOOR AREA HEATER

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ATA 21 AIR CONDITIONING

DOOR AREA HEATING — FUNCTIONAL DESCRIPTION The air conditioning system controls operation of the door area heaters. The logic for the door area heaters comes from the air/ground system and air conditioning pack valve operation. FUNCTIONAL DESCRIPTION The door area heater power relay (R560) controls power to the heaters. When the airplane is in the air and one of the pack flow control and shutoff valves is open, the relay energizes. When the relay energizes, 115v ac power from main bus 1 goes to the heaters. The door area heaters use phase-to-phase power. Power goes through two heat elements per unit. Each heat element uses 325 watts. There are internal temperature control components that keep the temperature to a limit. The overheat switch opens at a temperature of 230°F (110°C) and closes at 200°F (93°C). The thermal fuse opens at a temperature of 300°F (148°C). The overwing exit doors are heated with heaters behind the lining, door trim, and close out panels.

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ATA 21 AIR CONDITIONING

DOOR AREA HEATING SYSTEM SCHEMATIC

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ATA 21 AIR CONDITIONING

EQUIPMENT COOLING SYSTEM EQUIPMENT COOLING SUPPLY SWITCH The equipment cooling system uses these two systems to remove heat from equipment:  Supply system (pushes air)  Exhaust system (pulls air). The supply system and the exhaust system use fans to move air. Each system has a primary fan and an alternate fan. The equipment that is not cooled by the equipment cooling system stays cool by convection. The supply and exhaust fans move air through ducts and manifolds. The ducts and manifolds connect to shrouds around the electronic and electrical equipment. Low flow sensors monitor the ducts for cooling flow conditions.

NORMAL  The normal cooling supply fan is activated. ALTERNATE  The alternate cooling supply fan is activated. EQUIPMENT COOLING SUPPLY OFF LIGHT Indicates no airflow from the selected cooling supply fan

SUPPLY The supply fans push air to these components:  P1, P2, P3 (display units)  P9 panel (FMC control display units)  Equipment racks in the EE compartment. EXHAUST The exhaust fans pull air from these components:  P1, P2, P3 (display units)  P9 (FMC control display units)  P6 (circuit breaker panel)  P5 (control and indication)  P8 (center aisle stand)  Equipment racks in the EE compartment. The overboard exhaust valve lets exhaust air go overboard when the airplane is on the ground. The exhaust air supplements heating in the forward cargo compartment in flight.

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ATA 21 AIR CONDITIONING

EQUIPMENT COOLING GENERAL

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ATA 21 AIR CONDITIONING

COMPONENT LOCATION The equipment cooling system is divided into two parts:  Supply  Exhaust SUPPLY The right sidewall section of the EE compartment contains these components:  Normal and alternate supply fans  Check valves  Air filter. The supply duct extends forward along the right sidewall. It divides to supply the equipment racks in the EE compartment and the panels in the flight compartment. The supply low flow sensor is in the duct forward of the nose wheel well. You get access through the forward equipment compartment access door. EXHAUST The aft lower section of the EE compartment contains these components:  Normal and alternate exhaust fans  Check valves  Overboard exhaust valve. The overboard exhaust valve is under the floor structure at the center aft area of the EE compartment. The exhaust low flow sensor is forward of the nose wheel well. You get access through the forward equipment compartment access door.

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ATA 21 AIR CONDITIONING

EQUIPMENT COOLING COMPONENTS

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ATA 21 AIR CONDITIONING

SUPPLY AND EXHAUST FANS The supply and exhaust fans move air around electrical equipment to remove heat. GENERAL DESCRIPTION There are two sets of fans (normal and alternate) for the supply and the exhaust systems. One fan per system operates at a time. LOCATION The supply fans and check valves are in the EE compartment. They are behind the right bulkhead access panel of the forward cargo compartment. The exhaust fans and check valves are in the aft lower section of the EE compartment. You get access to the exhaust fans through the raised access panel aft of the equipment access door. PHYSICAL DESCRIPTION The normal and alternate cooling fans are single stage vaneaxial fans integrating the motor into the fan. The rotating impeller pushes air over the motor hou¬sing and through de-swirl vanes before exiting the fan. Three miniature ther¬mostats (204°C) serve as thermal protective devices for the fan. TRAINING INFORMATION POINT The supply and exhaust fans install with v-band clamps. Arrows show the proper flow direction. The supply and exhaust fans are interchangeable. CHECK VALVES A two section swing check valve, spring loaded closed, is located down stream of each fan to prevent back flow of air through the fan that is not operating.

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ATA 21 AIR CONDITIONING

SUPPLY AND EXHAUST FAN GENERAL

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Boeing 737-600/700/800/900 (CFM 56) subcat. B1.1

ATA 21 AIR CONDITIONING AIR FILTER INTERFACES

The equipment cooling air filter removes small particles of dirt from the air before it enters the EE cooling system. This prevents contamination of the electrical and the electronic equipment. The air filter is upstream of the supply fans. The air filter is a cartridge type filter inside the air filter housing. TRAINING INFORMATION POINT

The low flow sensors supply an alarm signal to these components for indication:  Flight recorder/mach airspeed module  The equipment cooling panel  The ADIRS (crew call).

A clogged air filter will cause low flow through the equipment cooling supply system. The air filter will require replacement on a regular maintenance schedule. Release the quick release tabs on the air filter housing cover to get access to the filters. LOW FLOW SENSORS The low flow sensors monitor air flow for the equipment cooling system. When airflow cooling quality through the equipment is not sufficient, the sensor supplies an indication. LOCATION The low flow sensors are in the forward equipment compartment. They are in the supply and exhaust ducts of the equipment cooling system. Access to the sensors is through the forward equipment compartment access door. FUNCTIONAL DESCRIPTION The low flow sensors are a hot wire anemometer type. The low flow sensor monitors the airflow and temperature of the equipment cooling air. The sensor sends an alarm signal when the equipment cooling airflow is not within limits. The low flow sensors have an internal BIT. At power-up, the low flow sensors and alarm circuits do a test for correct operation. If the sensor(s) fail the BIT test, the alarm circuit causes the MASTER CAUTION light and the related EQUIP COOLING OFF light to come on.

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ATA 21 AIR CONDITIONING

LOW FLOW SENSOR

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ATA 21 AIR CONDITIONING

LOW FLOW SENSOR INTERFACES The low flow sensors monitor air flow for the equipment cooling system. When airflow cooling quality through the equipment is not sufficient, the sensor supplies an indication. LOCATION The low flow sensors are in the forward equipment compartment. They are in the supply and exhaust ducts of the equipment cooling system. You access the sensors through the lower nose access door. FUNCTIONAL DESCRIPTION The low flow sensors are a hot wire anemometer type. The low flow sensor monitors the airflow and temperature of the equipment cooling air. The sensor sends an alarm signal when the equipment cooling airflow is not within limits. The low flow sensors have an internal BIT. At power-up, the low flow sensors and alarm circuits do a test for correct operation. If the sensor(s) fail the BIT test, the alarm circuit causes the MASTER CAUTION light and the related EQUIP COOLING OFF light to come on.

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The low flow sensors supply an alarm signal to these components for indication:  Flight recorder/mach airspeed module  The equipment cooling panel  The ADIRS (crew call). The alarm signal causes these indications to occur:  MASTER CAUTION Light comes on  The related EQUIP COOLING OFF light comes on  ADIRS (crew call) alert occurs if the airplane is on the ground. The supply system control interrupt relay causes an inhibit of the alarm signal. This occurs when the equipment cooling system is in the smoke clearance mode. The exhaust system does not have an inhibit for smoke clearance. TRAINING INFORMATION POINT The equipment cooling system uses cabin air for cooling. The cabin air can contain contaminates such as tar, nicotine, dust, and other unwanted particles. A regular schedule of cleaning this equipment is necessary for proper operation of the cooling system and sensors.

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ATA 21 AIR CONDITIONING

LOW FLOW DETECTOR

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ATA 21 AIR CONDITIONING

SUPPLY FAN FUNCTION The supply fan pushes air to the equipment in the EE compartment and flight compartment. There are two supply fans, normal and alternate. One supply fan is set to operate when you apply system power. NORMAL SUPPLY FAN OPERATION The normal supply fan operates when these conditions are true:  The thermal switches in the normal supply fan are closed (no overheat condition)  The supply system control interrupt relay is in the normal (deenergized) position  The EQUIP COOLING SUPPLY switch is in the NORMAL position. The normal supply fan control relay energizes to enable 115v ac threephase power to the fan. ALTERNATE SUPPLY FAN OPERATION The alternate supply fan operates when the EQUIP COOLING SUPPLY switch is in the ALTERNATE position and the same logic conditions as the normal fan. FAN FAILURE/LOW FLOW If a fan fails to operate, the supply low flow detector low alarm signal activates. The supply low flow detector supplies the discrete signal for the system OFF light and MASTER CAUTION light to come on. SMOKE/ INTERRUPT When the smoke control relay energizes, it supplies 28v dc power to energize the supply system control interrupt relay (R645). This relay energizes immediately and prevents power to the normal and alternate fans. The supply low flow detector receives an inhibit signal. This prevents the low flow signal to cause the OFF light and MASTER CAUTION light to come on. The supply system control interrupt relay de-energizes after a 5-minute time delay. ISSUE 1, Rev. 1: 2015.07.10

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ATA 21 AIR CONDITIONING

SUPPLY FAN FUNCTIONAL SCHEMATIC

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ATA 21 AIR CONDITIONING

EXHAUST FAN FUNCTION The exhaust fans pull air from equipment in the EE compartment and flight compartment. There are two exhaust fans, normal and alternate. One exhaust fan is set to operate when you apply system power. NORMAL EXHAUST FAN OPERATION The normal exhaust fan operates when these conditions are present:  Thermal switches in the normal exhaust fan are closed (no overheat condition)  Exhaust equipment cooling switch is in the NORMAL position  The normal exhaust fan control relay R29 energizes to supply 115v ac 3-phase power to the fan. ALTERNATE EXHAUST FAN OPERATION The alternate exhaust fan operates when the exhaust equipment cooling switch is in the ALTERNATE position and the same logic conditions as the normal fan. FAN FAILURE/LOW FLOW If a fan does not operate, the exhaust low flow detector low alarm signal operates. The system OFF light and the MASTER CAUTION lights come on.

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ATA 21 AIR CONDITIONING

EXHAUST FANS FUNCTIONAL SCHEMATIC

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ATA 21 AIR CONDITIONING

OVERBOARD EXHAUST VALVE TRAINING INFORMATION POINT The overboard exhaust valve has two functions. It controls the quantity of equipment cooling exhaust air that flows overboard and it operates in a smoke clearance mode.

Access to the overboard exhaust valve requires removal of the crew oxygen bottle. For more information see chapter 35, part II of AMM. Obey all precautions when working around oxyg0en systems.

LOCATION The overboard exhaust valve is in the aft center section of the EE compartment, below the floor. PHYSICAL DESCRIPTION The 4 inch diameter overboard exhaust valve has these physical features:  Valve body  Electromechanical rotary actuator (electric motor, gear reduction train)  Position indicator (NORMAL/SMOKE).  Valve disk  Damper housing (silicone oil filled). It attaches to the overboard exhaust duct by v-band clamps. FUNCTIONAL DESCRIPTION The overboard exhaust valve is a pneumatically controlled pressure regulated air shutoff valve. A 28v dc actuator overrides the valve pneumatic control for smoke clearance in the EE cooling system. A spring force on the valve disk fully opens the valve. When the airplane pressurizes, airflow through the valve increases. The valve stays fully open until the airflow rate through it is more than 30 lbs/min (14 kg/min). It is fully closed when differential pressure is more than 1 psid. In the smoke clearance position the valve disc is able to move freely from fully open to approximately 70 degrees open. The actual position is a function of airflow conditions. The silicone-oil damper limits the rate of valve disk movement.

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ATA 21 AIR CONDITIONING

OVERBOARD EXHAUST VALVE

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ATA 21 AIR CONDITIONING

OVERBOARD EXHAUST VALVE FUNCTIONAL HIGH FLOW MODE When the airplane is in flight, the normal position for the overboard exhaust valve (OEV) is closed. The overboard exhaust valve has an electromechanical rotary actuator to open the valve for smoke removal. The actuator moves the valve disk to the smoke removal mode position when the smoke mode condition is set. When the airplane is on the ground, ground sense relay R592 is energized and smoke control relay R648 is deenergized. Power goes through R648 and R650 to energize the valve actuator to the NORMAL position. When the valve actuator is in the NORMAL position, the valve position is a function of airflow (the valve is open until the airplane pressurizes). When the airplane is in the air, ground sense relay R592 is deenergized. In pressurized flight, the normal position for the overboard exhaust valve is closed. Switch position has an effect on valve position. A 28v dc electromechanical rotary actuator opens the valve in flight for more airflow or for smoke removal. The overboard exhaust valve has three modes of operation. These are the three modes of operation:  Normal  High flow  Smoke removal. NORMAL MODE These are the switch positions for the normal mode of operation:  Left and right pack switch - AUTO/OFF  or MT 737-900: BASIC  Right recirculation fan switch - AUTO. When the switches are in the normal position, relay R650 is deenergized. Power then goes through R648 and R650 to energize the valve actuator to the NORMAL position.

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The high flow mode increases cabin airflow. This occurs when the valve is open. These are the switch positions for the high flow mode of operation:  Left or right pack switch - HIGH  Right recirculation fan switch - AUTO. When the switches are in the high flow position, relay R650 is energized and power goes to time delay relay R649. Relay K1 controls relay R649. The cabin pressurization system gives an open/closed enable signal to K1. With an open enable signal, R649 is deenergized and power energizes the actuator to the SMOKE (open) position. SMOKE REMOVAL MODE The smoke removal mode opens the valve to remove smoke from the EE compartments and flight compartment. These are the switch positions for the smoke removal mode:  Left or right pack switch - HIGH  Right recirculation fan switch - OFF. When the switches are in the smoke removal position, smoke control relay R648 energizes. Power then goes through R648 to energize the valve actuator to the SMOKE (open) position. OPEN/CLOSE ENABLE SIGNAL The cabin pressurization system supplies an open/close enable signal. The open enable signal lets the high flow mode energize the actuator to the SMOKE (open) position. The close enable signal keeps the actuator in the NORMAL position. The open enable signal is set when the outflow valve is more than 8.5 degrees open. The open enable signal stays true until the outflow valve is less than 2 degrees open. The closed enable signal is set when the outflow valve is less than 2.0 degrees open. The closed enable signal energizes relay K1. Relay R649 then energizes. R649 remains energized until five minutes after relay K1 relaxes. The five-minute time delay lets the cabin pressure become stable.

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ATA 21 AIR CONDITIONING

EXHAUST VALVE FUNCTIONAL SCHEMATIC

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ATA 21 AIR CONDITIONING

21-50 COOLING COOLING — FUNCTIONAL DESCRIPTION The temperature control system is configured in such a way that under normal operation, the airplane is divided into three zones. These zones are the,  control cabin zone,  forward passenger cabin zone, and aft passenger cabin zone. Controlling the temperature in the cabins is accomplished by controlling the temperature of the air entering the cabins. Air conditioning operation begins when the pack switches are positioned to AUTO or HIGH. This commands the respective pack valve to open allowing bleed air into the pack. PACK VALVE During normal operating, it modulates to meter pack airflow to one of three flow schedules:  OFF The pack valve is closed.  AUTO With both packs operating in AUTO, each pack regulates to normal flow rate approximately 75 lbs/min. With one Pack operating, regulates to high Flow Rate when:  in Flight and Flaps Up (if Engine Bleed is used)  in Flight, regardless of Flaps (if APU Bleed is used).  HIGH Pack regulates - 105 lbs/min. If APU bleed air is used on ground, the pack regulates to APU high flow approximately - 131 lbs/min. PACK FLOW Downstream of the pack valve, the bleed air is diverted to a trim air system, pack temperature control valve, standby pack temperature control valve, and the primary heat exchanger. The bleed air enters the primary heat exchanger where thermal energy is extracted from the bleed air by the cooler ram air passing around the primary heat exchanger. The air leaves the primary heat exchanger and enters the compressor side of the air cycle machine. In the com¬pressor, the pressure and temperature of the air is increased. For system protection, the compressor is limited to 200°C by the ISSUE 1, Rev. 1: 2015.07.10

compressor overheat switch.The air then enters the secondary heat exchanger. Again, thermal energy is extracted by ram air passing around the heat exchanger. However, the heat transfer is augmented by water evaporating on the surface of the secondary heat exchanger. The water is sprayed on to the secondary heat exchanger by a water spray nozzle located in the ram air duct. Upon leaving the secondary heat exchanger, the air enters a high pressure water separator system. The first item the air enters is the water extractor duct. The water extractor duct removes any condensate on the inner walls of the duct leaving the secondary heat exchanger. The extracted water is ducted the collection manifold installed on the bottom of the condenser. After leaving the water extractor duct, the air enters the hot side of the reheater on its way to the condenser. This air transfers some of its heat to the dehumidified air returning from the water ex¬tractors. Next, the air enters the condenser where it is cooled by the discharge air leaving the air cycle machine turbine. The cooling of the air causes the moisture in the air to condense. The moisture is removed by passing through the water extractors. The static swirl vanes located in the core of the water extractors removes the water by centrifugal motion. The water is collected in sumps on the water extractors. The water from the sumps is ducted to a collection manifold located on the bottom of the high pressure water separator system. This water is ducted from the manifold to the water spray nozzle located in the ram air duct. A port on the manifold is provided for overflow provisions caused by a clogged nozzle. The dehumidified air then enters the reheater for the second time. This will heat the air before entering the air cycle machine turbine. Across either path of the condenser, icing may occur restricting the airflow. This will cause a change in differential pressure sensed by the standby pack temperature control valve. In this situation, the standby pack temperature control valve will allow hot bleed air to enter the condenser to deice either path. When the differential pressure returns to normal, the standby pack temperature control valve will close.The air expands in the turbine decreasing its temperature and pressure.This expansion through the turbine powers the compressor. The compressor and turbine are connected by a common shaft. For system protection, the air entering the turbine is limited to 100°C by the turbine inlet overheat switch. The air leaving the turbine is extremely cold and is warmed by bleed air from the pack temperature control valve. The air then passes through the condenser for the second time cooling the air from the reheater. Next the air enters the mix manifold by way of the conditioned air check valve. For system protection, the discharge temperature is limited to120°C by the pack discharge overheat switch.

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ATA 21 AIR CONDITIONING

AIR CONDITIONING SYSTEM SCHEMATIC

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ATA 21 AIR CONDITIONING

PNEUMATIC CONTROL PANEL

TRIP RESET SWITCH  PRESSED:lf the Fault Condition has been corrected, resets BLEED TRIP OFF, PACK and ZONE TEMP Lights. Lights remain illuminated until reset.

RECIRCULATION FAN SWITCH  AUTO (in Flight)  Left Fan is running except when both Packs are operating and either Pack is in high Flow.  Right Fan is running except when both Packs are working in high Flow.  AUTO (on Ground)  Left Fan is running except when both Packs are operating in high Flow.  Right Fan will continue to run when both Packs are operating in high Flow. PACK SWITCH  AUTO  With both packs operating in AUTO, each Pack regulates to normal Flow Rate.  With one Pack operating, regulates to high Flow Rate when:    

in Flight and Flaps Up (if Engine Bleed is used) in Flight, regardless of Flaps (if APU Bleed is used). HIGH Pack regulates to High Flow. If APU Bleed Air is used on Ground, the Pack regulates to APU High Flow which exceeds the High Flow Rate by approx. 20%.

PACK LIGHT  Indicates Pack Trip Off or Failure of both Primary and Standby Pack Con-trols. Pack Trip caused by Compressor Discharge, or Turbine Inlet, or Pack Discharge Temperature exceeding Limit. Pack Valve closes automatically. MASTER CAUTION Light and AIR COND annunciator will illuminate.  During MASTER CAUTION Light Recall, indicates Failure of either Primary or Standby Pack Control. Will extinguish when Master Caution is reset. ISSUE 1, Rev. 1: 2015.07.10

TEMPERATURE CONTROL PANEL TEMPERATURE INDICATOR  Indicates Temperature at location selected with Air Temperature Source Selector. AIR TEMPERATURE SOURCE SELECTOR  SUPPLY DUCT  Selects appropriate Zone Supply Duct Temperature.  PASS CAB  Selects FWD or AFT Passenger Cabin Temperature.  PACK  Selects Water Extractor Discharge Temperature.  Trim Air Switch  ON  Trim Air Pressure Regulation and Shut Off Valve open.  OFF  Trim Air Pressure Regulation and Shut Off Valve closed. ZONE TEMP LIGHT  CONT CAB Light indicates a Duct Temperature Overheat, or Failure of the Cockpit Primary and Back Up Temperature Control.  FWD CAB/AFT CAB Light indicates a Duct Temperature Overheat.  During MASTER CAUTION LIGHT recall, the illumination of the CONT CAB LIGHT indicates failure of the Cockpit Primary or Back Up Temperature Control. Illumination of either FWD or AFT CAB Light indicates Failure of the associated Zone Temperature Control. Pack/Zone Controller Bite Test is required.  Will extinguish when MASTER CAUTION is reset. TEMPERATURE SELECTOR  AUTO. Provides automatic Temperature Control for associated Zone. Rotating the Control towards C (cool) or W (warm) sets the desired Temperature from 18° Cto30° C.  OFF - Closes the associated Trim Air Modulating Valve.

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ATA 21 AIR CONDITIONING

OVERHEAD CONTROL PANEL

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ATA 21 AIR CONDITIONING

RAM AIR SYSTEM-FUNCTIONAL FLIGHT (FLAPS NOT UP) The ram air system controls the airflow through the primary and secondary heat exchangers. These are the ram air control components:  Ram air inlet controller  Ram air inlet actuator  Ram air control temperature sensor  Ram air inlet deflector door  Ram air inlet modulation panel  Ram air ducts. These are the three modes of control for the ram air system:  Ground  Flight (flaps not up)  Flight cruise (flaps up). The air conditioning accessory unit (ACAU) relays control power to the ram air controller and the ram air actuator. There are separate control circuits for the left and right ram air systems. The left system is described. The right system operates the same. GROUND MODE When the airplane is on the ground, the AIR/GND sensing system supplies a discrete (ground) to energize the K10 pack air ground relay, and the K5 ram mod control relay. The K16 ram air actuator disable relay is energized. This removes the left pack zone controller from the ram air inlet actuator. 115v ac power goes through these relay contacts to supply a retract signal to the left ram air actuator:  Ram BITE enable (K15 - NORMAL)  Ram mod control (K5 - OPEN)  Pack air/ground (K10 - GROUND)  Ram air actuator disable (K16 — MODULATE). When the actuator is in the fully retracted position, the S1 switch opens to remove power to the motor. The deflector door is in the extended position when the actuator shaft is between the S1 and S2 switch positions. The S3 switch in the ram air actuator connects a ground to the air conditioning / bleed air controls panel. This causes the left RAM DOOR FULL OPEN light to come on. ISSUE 1, Rev. 1: 2015.07.10

At takeoff, the AIR/GND sensing system opens to de-energize the K10 relay. The K5 relay stays energized with a ground from the flaps switch when the flaps are not up. Power to the motor extend coils is through the internal S2 switch at takeoff. The deflector door moves out of the airstream when the actuator shaft is at the S2 switch position. FLIGHT (FLAPS UP) In flight, when the flaps are at a full up position, the K5 relay de-energizes. This de-energizes the K16 relay and gives the pack/zone controller control of the ram air inlet actuator. The ram air control circuits in the pack/zone controller supply command signals to the actuator. The pack/zone controller gets temperature signals from the ram air sensor. The ram air sensor sends temperature signals from the air cycle machine (ACM) compressor outlet. The controller uses the air (temperature) sensor signal in a bridge circuit. The bridge circuit reads the ACM compressor temperature as an error signal, too hot or too cold. The nominal (balanced) control temperature is 230F/110C. The pack/zone controller opens or closes the ram air inlet modulation panels to keep this balance. The normal position for the ram air inlet modulation panel in flight with the flaps up is faired (closed). This is to decrease drag. Training Information Point If the DOOR FULL OPEN LIGHT is on during flight cruise mode, it may be one of these three possible problems:  The ram air system may have a blockage  The heat exchangers are dirty  Electrical failure.

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ATA 21 AIR CONDITIONING

RAM AIR SYSTEM ELECTRICAL SCHEMATIC

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ATA 21 AIR CONDITIONING

HEAT EXCHANGER AND WATER EXTRACTOR DESCRIPTION CONDENSER The condenser decreases the temperature of the air in the air conditioning pack to below dew point. This causes the water vapor in the airstream to go into a liquid form. The condenser is a a plate-fin, single-pass, crossflow, air-to-air heat exchanger. It is made of aluminum. The condenser uses turbine discharge air to cool pack air after it makes the first pass through the reheater. The air cools enough to condense moisture. Part of the cold air bypasses around the condenser core and warm air comes through de-icing passages in the face of the core to prevent icing at the cold air face of the core. A free passage between the two condenser cores is an icing fail-safe. Delta pressure sense line bosses connect sense lines to the pneumatic servo-actuator of the standby temperature control valve. Icing in the condenser creates a differential pressure large enough to open the standby temperature control valve. Warm air from the standby temperature control valve into the turbine discharge stream warms the condenser and melts ice. You must remove the left air conditioning pack high pressure water separator to get access to the center fuel tank access panel. REHEATER The reheater increases the temperature of the air in the air conditioning pack before it enters the turbine of the air cycle machine. This increases the efficiency of the turbine. The primary purpose of the reheater is to increase the turbine efficency of the air cycle machine. Bleed air leaving the water extractor duct enters the reheater on the first of two passes through the unit. This air warms the air coming from the water extractors (second pass) before entering the turbine. The air exiting the reheater (first pass) then enters the condenser. The reheater is a a plate-fin, single-pass, crossflow, air-to-air heat exchanger. It is made of aluminum.

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ATA 21 AIR CONDITIONING

CONDENSER AND REHEATER

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ATA 21 AIR CONDITIONING

WATER EXTRACTOR DUCT The water extractors are coaxial split—can type gravity fluid separators. Water in the airstream falls into the sump of the water extractor duct. The sump collects the water, and pressure in the extractor forces the water out of the sump into the drain boss. A line connects the drain boss to the water spray nozzle. The water spray nozzle injects the water into the ram air duct. This cools the ram air stream by evaporation. WATER SPRAY NOZZLE The water in the water extractor sumps is ducted to a collection manifold located on the underside of the high pressure water separator. The water extractors are located forward and aft of the condensor in the equipment bay. During some operating conditions, water condensation occurs in the secondary heat exchanger. This moisture is removed by the water extractor duct. The water collected by the water extractors and water extractor duct is ducted from the collection manifold to a water spray nozzle located in the ram air duct. In the event of a clogged nozzle, a port on the collection manifold will discharge the overflow.

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ATA 21 AIR CONDITIONING

WATER EXTRACTOR DUCT

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ATA 21 AIR CONDITIONING

PRIMARY WATER EXTRACTOR The water extractors are inertial-type centrifugal flow fluid separators. The inlet of the water extractor has a swirl chamber to create a vortex airflow. The water fraction of the airstream is centrifugally shed into the outer shell of the extractor. A sump collects the water, and pressure in the extractor forces the water out of the sump into the drain nipples. Lines connect the drain nipples to the water spray nozzle. The water spray nozzle injects the water into the ram air duct. This cools the ram air stream by evaporation. PACK TEMPERATURE SENSOR The pack temperature sensors measure the temperature in the air conditioning pack. They give feedback to the pack/zone temperature controllers. The pack temperature sensor is on the pack high pressure water separator assembly. FUNCTIONAL DESCRIPTION The pack temperature sensors are thermistor devices. Their resistance changes with temperature. The temperature sensor resistance is the feedback to the pack/zone controller. The pack/zone controller uses the feedback to con¬trol the discharge temperature of the air conditioning system. Each pack temperature sensor has two sense elements. One element to give feedback to each of the two pack/zone temperature controllers. One element gives pack temperature feedback to the auto (normal) channel of its related pack/zone temperature controller. The other element gives pack temperature feedback to the standby channel of the opposite pack/zone temperature con¬troller. PACK TEMPERATURE BULB The pack temperature bulb also consist of a temperature sensitive resistance element. The bulb provides temperature information to the control cabin on the P5 overhead panel. The pack temperature bulb is located in the aft water extractor discharge duct upstream of the reheater. ISSUE 1, Rev. 1: 2015.07.10

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ATA 21 AIR CONDITIONING

PRIMARY WATER EXTRACTOR

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ATA 21 AIR CONDITIONING

PACK TEMPERATURE CONTROL VALVES STANDBY TEMPERATURE CONTROL VALVE (STCV) TEMPERATURE CONTROL VALVE The temperature control valve is used to control pack outlet temperature during normal system operation. The valve provides a parallel path to the turbine outlet around the air cycle machine.

The standby temperature control valve does these things:  Gives backup control for the discharge temperature of the air conditioning pack (normal temperature control system failure)  Increases the temperature of pack discharge air to prevent ice formation in the condenser.

DESCRIPTION FUNCTIONAL DESCRIPTION The temperature control valve consists of an actuator and a valve. A capacitor is used to provide additional starting torque. The valve may be manually opened or closed by rotating the manual override knob. The pack/zone controller modulates the temperature control valve to provide the required pack outlet temperature. OPERATION When the pack outlet temperature is too high, the pack/zone controller will modulate the temperature control valve towards the closed position. Closing the temperature control valve will cause more air to go through the air cycle machine and increase its speed. A higher speed will cause the air from the turbine to be colder. If the temperature control valve opens, air will bypass the air cycle machine and the output temperature will be warmer. If the pack valve is closed, the temperature control valve closes also.

The valve is a peumatically actuated butterfly—type modulating and shutoff valve. It is spring—loaded to the closed position. Control pressure to the actuator opens and modulates the valve. The control pressure source is the upstream side of the valve. These valve devices regu¬late pressure to the valve actuator:  The electromagnetic control valve assembly  The delta pressure servo control assembly. A signal from the pack zone controller's standby pack control channel drives the electromagnetic control device. Pneumatic lines sense condenser differential pressure and drive the delta pressure servo control device. Ice formation in the condenser increases the pressure differential. If the electromagnetic and the delta pressure controls operate at the same time, the device that gives the greatest valve open pressure will prevail.

TRAINING INFORMATION POINT TRAINING INFORMATION POINT There is a position indicator on the temperature control valve. The valve is nor-mally in the closed position when the pack is off. You can manually close the valve with the manual override knob if the electric motor fails. Turn the knob in the direction shown on the knob placard.

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There is a position indicator on the standby temperature control valve. The valve is normally in the closed position when the pack is off.

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ATA 21 AIR CONDITIONING

TEMPERATURE CONTROL VALVES

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TEMPERATURE CONTROL VALVES SCHEMATIC DESCRIPTION TEMPERATURE CONTROL VALVE The 115v ac, 400 Hz, single-phase temperature control valve receives its signals from the controller. The electric motor drives an output shaft through a slip clutch. The valve disk, a visual position indicator, and a cam are connected to the output shaft. The cam contacts a set of limit switches to provide feedback signals to the controller. A manual override drives the output shaft through the slip clutch. STANDBY TEMPERATURE CONTROL VALVE The standby temperature control valve is electrically and pneumatically controlled and pneumatically operated.  TORQUE MOTOR Electrical control of the valve is part of the standby mode of operation. In this mode, a flapper in the torque motor is electrically positioned to regulate pressure in the pneumatic actuator. The servos actuate a poppet valve to control the actuation pressure being ported from the reference pressure reg-ulator to the pneumatic actuator to open the disk. The flow of hot air into the condenser will increase and the condenser will deice. As the condenser deices, the differential pressure decreases and the disk closes.  HIGH/LOW PRESSURE DELTA P SERVO If ice begins to form across either path through the condensor, an increase in differential pressure is sensed by the respective delta P servo. The increased differential pressure actuates a delta P poppet valve allowing pressure in the pneumatic actuator to increase. This will cause the valve to open. The flow of hot air into the condensor will increase and the condensor will deice. As the condensor deices, the differential pressure decreases and the valve closes.

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ATA 21 AIR CONDITIONING

TEMPERATURE CONTROL VALVE SCHEMATIC

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ATA 21 AIR CONDITIONING

MIX MANIFOLD TEMPERATURE SENSOR The mix manifold temperature sensors measure the temperature in the mix manifold of the air conditioning system. They give feedback to the pack/zone temperature controllers. LOCATION There are two mix manifold temperature sensors. They are similar in design and operation. They are on the upper aft wall of the mix manifold. Access is through the center aft bulkhead panel in the forward cargo compartment. PHYSICAL DESCRIPTION The mix manifold temperature sensors have these parts:  Sense element  Case with mounting boss  Electrical connector. FUNCTIONAL DESCRIPTION The mix manifold temperature sensors are thermistor devices. Their resistance changes with temperature. The temperature sensor resistance is the feedback to the pack/zone controller. The pack/zone controller uses the feedback to prevent freezing temperatures in the air conditioning distribution system. Freezing temperatures in the distribution ducts can cause moisture in the duct joints to freeze. The ice formation and expansion in the ducts can cause damage. CONDITIONED AIR CHECK VALVE The conditioned air check valve permits one-way airflow from the pack to the main distribution manifold. The packs supply pressurized air through the check valve to the distribution system. The check valve prevents airflow from the pressurized distribution system to the unpressurized air conditioning compartment. This is for single pack operation or a pack system duct leak.

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MIX MANIFOLD SENSOR

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21 - 60 TEMPERATURE CONTROL TRIM AIR PRESSURE REGULATING VALVE The trim air pressure regulating and shut off valve is an electrically controlled, pneumatically actuated, pressure regulating valve. The primary components of the valve are a pneumatic actuator assembly, a servo regulator, a nonlatching solenoid assembly, a manual override position indicator, a relief valve, and the valve body assembly. The valve is spring loaded to a closed position. The solenoid valve is energized open when the TRIM AIR switch on the P5 overhead panel is positioned to the ON. Bleed air is ported to the open side of the pneumatic actuator to overcome the actuator spring force. The servo regulator senses the differential pressure between the bleed air and the cabin to regulate the trim air to (+) 4.0 psi above the cabin pressure. The trim air pressure regulating valve is located in the right equipment bay. MAINTENANCE PRACTICES The trim air system can be disabled by closing the manual override on the trim air pressure regulating valve. This removes valve actuation pressure through the solenoid assembly, and manually closes the valve assembly.

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ATA 21 AIR CONDITIONING

TRIM AIR PRESSURE REGULATOR

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ATA 21 AIR CONDITIONING

TRIM AIR MODULATING VALVE The trim air modulating valves port hot bleed air into the control cabin and passenger cabin zone ducts to meet zone temperature requirements. The trim air modulating valves are controlled by the pack/zone temperature controllers.  The forward passenger cabin and control cabin modulating valves receive positioning signals from the right controller. The left controller serves as backup to position the control cabin trim air modulating valve.  The aft passenger cabin zone modulating valve receives its signals from the left controller. The modulating valve operates on 115 volts ac, single-phase power. An elec-tromechanical actuator drives an output shaft through a slip clutch. A butterfly, visual position indicator, and a cam are connected to the output shaft. The cam contacts a set of limit switches to provide feedback to the pack/zone temperature controllers. A manual override drives the output shaft through the slip clutch. The passenger compartment valves are located fwd in the right equipment bay. The control cabin valve is located forward in the left air conditioning bay.

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ATA 21 AIR CONDITIONING

TRIM AIR MODULATING VALVE

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ATA 21 AIR CONDITIONING

THERMAL SENSING UNITS

passenger service units. Both assemblies are on the right side of the airplane.

Thermal sensing units in the temperature control system consist of zone temperature sensors, zone duct overheat switches, zone/duct temperature bulbs, and duct temperature sensors.  Duct and cabin zone temperature sensors are used to provide information to the pack/zone temperature controllers.  Zone duct overheat switches are used to protect ducts against thermal damage.  Zone/duct temperature bulbs provide temperature information to the tempe-rature gage on the P5 overhead panel. The zone duct temperature bulbs are also used to monitor supply duct temperatures of the flight deck and passenger cabins.

DUCT TEMPERATURE BULBS The zone/duct temperature bulbs provide temperature information to the tem-perature gage on the P5 overhead panel. Zone/duct temperature bulbs are used:  in the forward and aft passenger cabin.  in the distribution risers duct.  in the control cabin distribution duct. Zone/duct temperature bulbs consist of a temperature sensitive resistance element within a tube. As the temperature changes, the resistance changes accordingly to cause movement of an indicator pointer.

DUCT TEMPERATURE SENSORS LOCATION The duct temperature sensors provide information to the pack/zone temperature controllers.  The forward passenger cabin and control cabin zone duct temperature sensors provide information to the right pack/zone temperature controller.  The aft passenger cabin zone duct temperature sensor provides information to the left pack/zone temperature controller. The temperature sensors also utilize variable resistance type elements. As temperature increases, their resistance decreases and vice versa. DUCT OVERHEAT SWITCH The zone duct overheat switch consists of a bimetal element enclosed in a steel probe. The zone duct overheat switch contacts are normally open but a predetermined temperature will close the switch. A zone duct overheat switch is used in each supply duct to the passenger cabins and control cabin zone. The zone duct overheat switch activates at 90°C. If the switch is activated, airplane control logic will instruct the appropriate trim air modulating valve to close. The zone temperature sensor fans provide a constant air flow across the zone temperature sensors and the bulbs. The control cabin (flight deck) zone temperature sensor assembly is located to the left side of the P5 overhead panel. The passenger compartment zone temperature sensor assemblies are mounted in the bullnose area below the ISSUE 1, Rev. 1: 2015.07.10

Each passenger cabin zone has a zone duct overheat switch, a zone/duct tem-perature bulb, and a duct temperature sensor installed in the overhead riser. The switch, bulb, and sensor are installed on the right side of the centerline at the point where the riser joins the overhead distribution duct. ZONE TEMPERATURE SENSORS The zone temperature sensors provide compartment temperature information to the pack/zone temperature controllers. The temperature sensors also utilize variable resistance type elements. As temperature increases, their resistance decreases and vice versa.  The control cabin zone temperature sensor assembly is located to the left side of the P5 overhead panel.  The passenger compartment zone temperature sensor assemblies are mounted in the bullnose area below the passenger service units.  FWD zone temperature sensor installed at body station 416  AFT zone temperature sensor installed at body station 272G+13 Both assemblies are on the right side of the airplane. The zone temperature sensor fans provide a constant air flow across the zone temperature sensors and the bulbs.

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ATA 21 AIR CONDITIONING

DUCT TEMPERATURE SENSORS

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ATA 21 AIR CONDITIONING

AIR CONDITIONING ACCESSORY UNIT The air conditioning accessory unit (ACAU) is the interface for the airplane operational logic and the air systems. INTERFACES The air conditioning accessory unit has an interface with these systems:  Flight controls (flaps not up switch)  Landing gear (air/ground)  Engine starting  Air conditioning  Pneumatic/bleed air  Flight management computer (FMC). The ACAU receives signals from these airplane components:  Engine start valves  Flap control unit  Air/Gnd relays  Pack flow control and shutoff valve  Ram air actuator  Pack overheat switch  Temperature control valves  Trim air valves  Engine bleed switch  Duct overheat switch  Pneumatic system valves  P5 panels  Pressurization outflow valve  Recirculation fan  Overboard exhaust valve  Pneumatic system overheat/overpressure switch  FMC

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The ACAU sends signals to these components:  P5 panels  Bleed air regulator  Engine start valve  Pack flow control and shutoff valve  Ram air inlet controller  Trim air valves  Cabin temperature controller  Temperature control valves  Outflow valve  Recirculation fan  EE cooling fans  FMC. OVERHEAT PROTECTION CIRCUITS Three thermal switches, two temperature sensors, and a temperature bulb are used in the cooling system.  The pack discharge overheat switch activates at 120°C. The pack discharge overheat switch is located forward of the conditioned air check valve.  The turbine inlet overheat switch activates at 100°C. The turbine overheat switch is located in the reheater discharge duct.  The compressor discharge overheat switch activates at 200°C. The compressor discharge overheat switch is located in the discharge duct on the right side of the air cycle machine. When one of these switches activates, a signal is sent to airplane control logic which will result in the closure of the appropriate  pack valve;  pack temperature control valve and illumination of corresponding amber PACK light on the P5 overhead panel.

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ATA 21 AIR CONDITIONING

AIR CONDITIONING ACCESSORY UNIT

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ATA 21 AIR CONDITIONING

PACK/ZONE TEMPERATURE CONTROLLER

Note:

The pack/zone temperature controllers do these things:  Control their related air conditioning pack  Give automatic standby control to the opposite air conditioning pack  Control two zone trim air control channels  Control their related air conditioning pack ram air actuators  Give maintenance crews automatic built-in test equipment (BITE) that isolates faults to the line replaceable unit (LRU) level. GENERAL DESCRIPTION

Drive signals from the pack/zone controllers to the temperature control valves must pass through protective circuits in the air conditioning accessory units (ACAUs). The pack/zone controller BITE tests do not do a test of the ACAU protection circuitry. Failure in the ACAU circuitry may cause false valve failure bite indications.

TRAINING INFORMATION POINT The pack/zone temperature controllers are electro - static discharge sensitive (ESDS) devices. Use ESDS safe handling techniques.

Two identical and interchangeable pack/zone temperature controllers control the cooling pack discharge temperature and forms a three zone temperature control system. Their pin interface with the rack identifies them to the airplane systems. Each pack/zone temperature controller has these control channels:  Auto pack temperature control channel  Standby pack temperature control channel  Primary zone temperature control channel  Backup zone temperature control channel  Ram air actuator control channel. Front face BITE on the pack/zone controllers isolates system faults to the LRU level. Warning: BEFORE YOU DO A BITE TEST, MAKE SURE THE RAM AIR INLET AREA IS CLEAR. DURING THE BITE TEST SEQUENCE, THE RAM AIR INLET DEFLECTOR DOOR AND MODULATING PANELS OPERATE. THIS CAN CAUSE INJURY TO PERSONS AND/OR DAMAGE TO EQUIPMENT. A BITE test instruction placard is on the top of each controller face. A lamp test switch verifies controller power and operation of the green and red GO/NO GO lights. Four BITE TEST switches sequence the BITE checks and clear (reset) the controller memory registers.

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ATA 21 AIR CONDITIONING

PACK / ZONE CONTROLLER

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ATA 21 AIR CONDITIONING

TEMPERATURE CONTROL Air conditioning begins when one or both of the pack switches on the P5 overhead panel is positioned to AUTO or HIGH. This commands the respective pack valve(s) to open allowing bleed air to enter the pack. The flow rate at which bleed air enters the air conditioning system is determined by the settings on the P5 overhead panel. Downstream of the pack valve, the bleed air is diverted to a cooling pack system and a trim air system. The trim air system con¬sists of a trim air pressure regulating and shut off valve, three trim air modulating valves, two trim air check valves, and various thermal sensing units. These components in conjunction with the pack/zone temperature controllers provide a three zone temperature control system. The temperature control sy¬stem has a selectable range of 18°C to 30°C. The primary control for the trim air system is an ON/OFF switch on the P5 overhead panel. The ON/OFF switch is the only control for the trim air pressure regulating and shut off valve. This valve allows bleed air into the trim air system.

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ATA 21 AIR CONDITIONING

TEMPERATURE CONTROL BALANCED MODE

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ATA 21 AIR CONDITIONING

PACK / ZONE TEMPERATURE CONTROL STBY PACK OPERATION BALANCED MODE: When the trim air switch on the P5 overhead panel is positioned to "ON", the trim air pressure regulating valve allows bleed air to enter the trim air system. The air entering the system is regulated to + (4.0) psi above cabin pressure. The air then flows to the trim air modulating valves. The cooling packs, satisfy the zone requiring the most cooling. The trim air modulating valves are positioned to satisfy the other zones temperature demands. The trim air modulating valves receive positioning signals from the pack/zone temperature controllers. The positioning signals are generated from input signals received from the temperature selectors, zone temperature sen¬sors, and duct temperature sensors. The signals from the individual zone temperature selectors are sent to the pack/zone temperature controller and compared with input signals from the respective zone temperature sensors. This generates the error or temperature demand signal for each zone. The temperature demand signal for each zone is then compared to the duct temperature sensor signal for the respective zone. This produces a zone duct loop error which is used to position the trim air modulating valve to satisfy the temperature demanded at each zone inlet.

If the left pack automatic temperature control fails, an activate standby pack command signal is generated. This connects the left standby temperature con¬trol valve to the right pack/zone controller and activates the standby control. The standby pack control regulates the output of the pack using the standby temperature control valve. The standby temperature control valve performs the same function as the primary pack temperature control valve. If all zone and auto pack temperature controls have failed, the analog standby pack temperature controls will satisfy the average demand of the two passen¬ger cabin zone temperatures. The flight compartment temperature demand is not used by the analog standby temperature control.

ANTI ICE PROTECTION Ice protection is provided for the mix manifold by a 2°C, temperature limit to the output of the pack. The mix manifold temperature input to the pack/zone controller is from two sensors mounted on the mix manifold. The controller compares the two inputs and uses the coldest signal. The mix manifold temperature and the PACK DEMAND are then compared with a 2°C limit and the controller uses the warmest signal to position the temperature control valve. In the "UNBALANCED AVERAGE MODE", the left pack/zone controller will use the flight compartment duct temperature for the anti-ice temperature limit instead of the mix manifold temperature.

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ATA 21 AIR CONDITIONING

PACK / ZONE TEMPERATURE CONTROL

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ATA 21 AIR CONDITIONING

UNBALANCED COOLEST MODE This mode will be activated:  If there is a failure of the primary and backup flight compt. zone controls  If >90°C Duct Overheat in the control cabin occurs. In the unbalanced coolest mode, the left air conditioning pack satisfies the flight compartment temperature requirements and the right air conditioning pack will satisfy the colder demand of the two passenger cabin zones.

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ATA 21 AIR CONDITIONING

TEMPERATURE CONTROL UNBALANCED COOLEST MODE

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ATA 21 AIR CONDITIONING

UNBALANCED AVERAGE MODE This mode will be activated:  If there is a failure in the fwd or aft passenger cabin control circuit.  If >90°C Duct Overheat in the passenger cabin occurs. The logic will close the affected trim air modulating valve. The control cabin trim air valve, and the still operating passenger cabin trim air valve, controls the temperature. The left pack receives its demand signal from the control cabin temperature selector. The right pack temperature control will produce an average temperature based upon the passenger cabin temperature demands. Trim Air Switch to "OFF":  The logic will close all 3 trim air modulating valves. If a passenger cabin trim air system has failed an average zones mode command will be invoked. In this mode of operation, the left air conditioning pack will satisfy the flight compartment temperature requirements and the right air conditioning pack will satisfy the average of the two passenger cabin zones. In both modes of operation, the left pack/zone controller will use the flight compartment duct temperature for the anti-ice temperature limit instead of the mix manifold temperature.

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ATA 21 AIR CONDITIONING

TEMPERATURE CONTROL UNBALANCED AVERAGE MODE

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ATA 21 AIR CONDITIONING

21-20 DISTRIBUTION CONDITIONED AIR DISTRIBUTION A system of ducts distributes the conditioned air from the packs to outlets in the flight and passenger compartments. SUBSYSTEM FEATURES The conditioned air distribution system begins at the mix manifold which is located in the air conditioning distribution bay aft of the forward cargo compartment. The flight compartment air distribution system consists of a duct originating from the left pack input into the mix manifold. The duct goes forward under the floor of the passenger compartment on the left side of the airplane. In the lower nose compartment, the duct branches into several risers and goes vertically into the flight compartment ceiling, floor, and foot level outlets. The passenger compartment distribution system receives conditioned air from the mix manifold through four risers in the sidewalls. The risers discharge into an overhead distribution duct running the full length of the passenger compartment. Air discharges through outlets in the bottom of the duct, through flexible hoses to over window outlets between the passenger service units (PSU's) and the sidewall panels, and around the aft entry light assembly. During normal operation, two electrical recirculation fans draw air from the passenger compartment and the equipment cooling system through filters. The recirculation air is delivered to the mix manifold through check valves. The re-circulation fans and check valves are identical and interchangeable. Care must be taken to avoid reverse installation of the components. The recirculation rate is approximately 47 m3 per minute. No recirculated air goes into the flight compartment. The air in the airplane is changed every three minutes)

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ATA 21 AIR CONDITIONING

DISTRIBUTION SYSTEM GENERAL

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ATA 21 AIR CONDITIONING MIX MANIFOLD

The mix manifold receives conditioned air from both packs, the recirculation fans, or from an external conditioned air source. The mix manifold routes the air to the distribution system. LOCATION The mix manifold is located in the air conditioning distribution bay aft of the forward cargo compartment. A-removable bulkhead separates the cargo compartment from the air conditioning distribution bay. FEATURES Ducts from the left and right packs enter the bottom of the mix manifold. Four risers carry air from the top of the mix manifold, to the passenger compartment. Temperature sensors on the top forward side of the manifold send signals to the pack/zone controllers. Air from the recirculation fans enter the mix manifold on the left and right sides. A duct on the bottom rear of the mix manifold connects with the external conditioned air fitting. The external conditioned air fitting is accessible on the bottom of the fuselage, forward of the air conditioning doors. Air for the flight compartment does not enter the mix manifold but goes from the left pack duct to the flight compartment.

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ATA 21 AIR CONDITIONING

MIX MANIFOLD

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ATA 21 AIR CONDITIONING

RIGHT RECIRCULATION FAN

LEFT RECIRCULATION FAN

The purpose of the right recirculation fan is to recirculate the conditioned air from the collector shroud. This will reduce the requirement for bleed air taken from the engines for air conditioning to the passenger cabin.

The purpose of the recirculation fan is to recirculate the conditioned air from the distribution bay. Recirculation of conditioned air reduces the requirement for bleed air taken from the engines for air conditioning.

PHYSICAL DESCRIPTION

PHYSICAL DESCRIPTION

Approximately 23,5m3 per minute of passenger cabin air is recirculated by a 115 volt ac, 3 phase fan. The fan draws air from the "U" shaped collector shroud moulded into the ceiling of the forward cargo compartment.

Approximately 23,5m3 per minute of passenger cabin air is recirculated into the mix manifold by a 115 volt ac,3 phase fan. LOCATION

OPERATION When the recirculation fan switch is in "AUTO", the fan operates in the following conditions:  AUTO (in Flight)  Right Fan is running except when both Packs are working in high Flow.  AUTO (on Ground)  Right Fan will continue to run when both Packs are operating in high Flow. The shroud collects air from the passenger compartment exhaust grilles in the carpet risers and the equipment cooling exhaust. In flight, the shroud is main-tained at a low pressure by an open forward outflow valve or by the right recirculation fan inlet. When the right recirculation fan is operating, the forward outflow valve closes automatically. Recirculated air is drawn through filters and is discharged into the mix manifold. The air mixes with conditioned air for distribution into the passenger compartment. The conditioned air is supplied from the packs or the external conditioned air cart. Three thermal switches protect the fan motor against overheating: 177°C . The thermal switches reset automatically after cooling.

The left recirculation fan, check valve, and filter assembly are located to the left of the mix manifold in the air conditioning distribution bay. The area is a pressurized space aft of the forward cargo compartment. OPERATION When the recirculation fan switch is in "AUTO", the fan operates in the following conditions:  AUTO (in Flight)  Left Fan is running except when both Packs are operating and either Pack is in high Flow.  AUTO (on Ground)  Left Fan is running except when both Packs are operating in high Flow. Recirculated air is drawn from the space in the air conditioning distribution bay. The air is drawn through filters and is discharged into the mix manifold. It mixes with air from the packs or external conditioned air for distribution into the pas-senger compartment. Three thermal switches protect the fan motor against overheating: 177°C. The thermal switches reset automatically after cooling.

MAINTENANCE PRACTICES

MAINTENANCE PRACTICES

A removable panel in the forward section of the fan inlet duct allows access to the filters. The aft right panel of the forward cargo compartment must be removed to expose the duct.

Access to the filters is by removal of the aft left panel of the forward cargo compartment.

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ATA 21 AIR CONDITIONING

RIGHT RECIRCULATION FAN CIRCUIT

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ATA 21 AIR CONDITIONING

21 - 30 PRESSURIZATION CONTROL The airplane operates at altitudes where the oxygen density is not sufficient to sustain life. The pressurization control system keeps the airplane cabin interior at a safe pressure altitude. This protects the passengers and crew from the effects of hypoxia (oxygen starvation). GENERAL DESCRIPTION The pressurization control system has three sub - systems:  Cabin pressure control system The system controls the position of the outflow valve to control cabin pressure. The air conditioning packs force air into the airplane pressure vessel (cabin). The pressurization system controls the rate at which the air flows out of the cabin. This maintains a safe cabin pressure. The pressurization control systems are designed for a nominal operating pressure of 7.8-8.35 psid with a maximum operating pressure of 8.45 psid. It has these components:  Cabin pressure control panel (P5-6)  Digital cabin pressure controllers (2)  An outflow valve.  Cabin pressure relief system  The cabin pressure relief system is a fail safe system. It protects the airplane structure from overpressure and negative pressure if the automatic system fails. The relief system has these components:  Positive pressure relief valves (2) The protect the fuselage structure from overpressure. They are set to open and release pressure at 8.95 psid.  Negative pressure relief valve. The valve opens when pressure outside of the airplane is 1.0 psi more than the pressure inside of the airplane (-0.1 psid).  Cabin pressure indication and warning system. The cabin pressure indication and warning system gives you data about the pressurization system status. This system has these components:  Cabin altitude panel (P5-16)  Aural warning box panel (P9)  Cabin altitude warning switch. ISSUE 1, Rev. 1: 2015.07.10

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ATA 21 AIR CONDITIONING

PRESSURIZATION CONTROL

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ATA 21 AIR CONDITIONING

PRESSURIZATION — GENERAL DESCRIPTION ELECTRIC POWER AUTOMATIC PRESSURIZATION CONTROL In the automatic mode of operation, the system uses a redundant system of digital pressure controllers to schedule cabin pressurization through all phases of flight. The active pressure controller keeps cabin altitude at a safe comfortable pressure altitude (8,000 ft ISA maximum). The pressure controllers are line replaceable units and incorporate standard front face bite. MANUAL PRESSURIZATION CONTROL In the manual mode of operation, the flight crew has direct control of the outflow valve from the P5 panel. GENERAL DESCRIPTION There are two digital cabin pressure controllers (CPCs). Each CPC has its own systems interface and valve motor system. This gives the AUTO mode of control a dual redundant architecture. Only one CPC controls the outflow valve at any time. The other CPC is a backup. The active controller changes with every flight or with an autofail event. The manual control mode overrides and bypasses the two CPCs. The manual control system has its own valve motor system. This gives the pressurization control system a triple redundant architecture. The cabin pressure control system has these components:  A cabin pressure control panel  Digital cabin pressure controllers (2)  An aft outflow valve assembly with three drive motors  Wiring, connectors and power sources.

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The system gets triple redundant 28v dc power from these sources:  Battery bus, DC bus 1 and DC bus 2. DATA INPUT INTERFACE The flight crew makes these inputs to the cabin pressure control panel:  Pressurization mode  Flight altitude  Landing altitude. A sensor on each CPCs senses pressure in the cabin. Each CPC gets air data from both the air data inertial reference units. Each CPC gets engine speed data from both the stall management and yaw damper computers (SMYDCs). Each CPC gets air/ground logic from the proximity switch electronics unit. Each CPC uses position feedback from valves that effect the pressurization system:  Left pack valve  Right pack valve  Overboard exhaust valve. OUTFLOW VALVE INTERFACE The outflow valve has three motors:  Two AUTO mode motors with control electronics boxes  One MANUAL mode motor with no electronics box The CPCs use data buses to interface with the drive electronic boxes on the valve. The electronics boxes drive the automatic mode motors. Altitude switches on each drive electronic box will override CPC signals and close the outflow valve if cabin altitude pressure is 14,500 feet. This function will not effect manual mode operation of the outflow valve. In manual mode, the pilot uses the control module toggle switch to operate the outflow valve. The manual valve motor has no control electronics box, and no pressure switch. The outflow valve gives position feedback to:  The two CPCs  The P5 overhead panel.

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ATA 21 AIR CONDITIONING

PRESSURE CONTROL INTERFACE

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ATA 21 AIR CONDITIONING

PRESSURE CONTROL MODULE The cabin pressure control module and cabin altitude panel let the crew monitor and control the pressurization system. The control panel has these parts:  Cabin pressure control module  System status lights  Pressure indication panel. LOCATION The cabin pressure control module is on the P5-6 panel. The system status lights are above the module. The cabin altitude panel (P5—16) is next to the module. CABIN PRESSURE CONTROL MODULE The cabin pressure control module has these controls:  Mode selector  Landing altitude (LAND ALT) selector with display  Flight altitude (FLT ALT) selector with display  Aft outflow valve position indicator  Manual control toggle switch. The mode selector has three positions. They set these system modes of operation:  AUTO for automatic operation  ALT for alternate automatic operation  MAN for manual control. Two selectors are used to set the flight altitude and the landing field altitude into the system controller. The flight altitude selection is made in 500 foot increments. The flight altitude range begins at —1000 ft. and extends to 42,000 ft. The landing field altitude ranges from —1000 ft. to 14,000 ft. in increments of 50 ft. The liquid crystal displays show the settings, A three position toggle switch controls the aft outflow valve when in the manual mode. It has three positions:  CLOSE NEUTRAL OPEN.

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It is spring loaded to the neutral position. An aft outflow valve position indicator shows the valve position in all modes of operation. These are the four system status lights above the control module.  AUTO FAIL  OFF SCHED DESCENT  ALTN  MAN. These four lights give these indications:  Operational mode  Deviation from flight plan  System failure. CABIN ALTITUDE PANEL These indicators and control switch are left of the pressure control panel:  Cabin altitude and differential pressure indicator  Cabin rate of change indicator  Cabin altitude warning horn cutout switch. The cabin altitude and differential pressure indicator is connected to the alternate static system. The rate of change indicator senses pressure changes from a port on the back of the indicator. Placards on the pressurization control panels are used during manual operation modes. They provide a reference for:  Takeoff and landing pressure differential maximums  Flight altitude to cabin altitude conversions. TRAINING INFORMATION POINT The cabin pressure control module has integrated circuit electronics. It is an electro—static discharge sensitive (ESDS) device. Use proper care when you handle it.

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ATA 21 AIR CONDITIONING

PRESSURE CONTROL MODULE

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ATA 21 AIR CONDITIONING

CABIN PRESSURE CONTROLLER (CPC) The cabin pressure controllers (CPCs) have these functions:  Control cabin pressure when the system is in the AUTO or ALTN mode of operation  Perform system BITE (start up, continuous, and initiated tests). LOCATION The two pressure controllers are in the EE compartment. The No. 1 CPC is on the E2-2 rack. The No. 2 CPC is on the E4-1 rack. PHYSICAL DESCRIPTION Each controller has a pressure sensor on its face. Each controller has a standard BITE module on its face. Refer to the adjustment/test section of the maintenance manual or to the BITE manual for the cabin pressure controller BITE instructions. ARINC 429 interrogation ports are behind the BITE instruction plates. They allow interface during system operation for real time onboard troubleshooting. GENERAL DESCRIPTION There are two cabin pressure controllers. The two controllers are identical and interchangeable. The controllers use digital circuitry. The controllers are part of a dual redundant system. They are active when the system operates in the AUTO or ALTN modes. Only one controller operates the outflow valve at any given time. The other controller acts as a backup. The controllers have pin selectable control functions. This optimizes the system for specific mission profiles. TRAINING INFORMATION POINT The cabin pressure controllers are electro static discharge sensitive (ESDS) devices. Use ESDS safe practices when you handle the units.

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ATA 21 AIR CONDITIONING

CABIN PRESSURE CONTROLLER

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ATA 21 AIR CONDITIONING

CABIN PRESSURE CONTROLLER BITE A BITE module is on the front face of each cabin pressure controller. The BITE does checks of these hardware and software:  All system components  System interfaces  Overall system performance. These selections are available when you push the MENU button and then the UP and DOWN arrows:  EXISTING FAULTS  FAULT HISTORY  GROUND TESTS  SYSTEM STATUS  SYSTEM TEST AND CLEAR. EXISTING FAULTS EXISTING FAULTS shows faults that are present. From the main menu EXISTING FAULTS, there are faults and fault details. FAULT HISTORY FAULT HISTORY shows previous faults. From the main menu FAULT HISTORY, there are faults and fault details. GROUND TESTS GROUND TEST has these two submenus:  DISPLAY TEST  SYSTEM TEST The DISPLAY TEST does a test of the LED display. The SYSTEM TEST does a test of the cabin pressurization system.

PRESENT STATUS shows the current inputs to the cabin pressure controllers. SYSTEM CONFIG shows the system configuration. SYSTEM TEST AND CLEAR The SYSTEM TEST AND CLEAR main menu selection prepares the controller for a system test and clears the FAULT HISTORY. TRAINING INFORMATION POINT When you push the ON/OFF button, the controller makes sure that the airplane is in the ground mode. If the airplane is not in the ground mode, A/P NOT IN GND shows for two seconds. Then BITE ABORTED shows for two seconds. There are these two types of faults:  Existing faults (EXIST FAULTS). If there is an existing fault, the cabin pressure controller shows FAULT on the front panel display. If there are only existing faults, the display shows nn EXIST FAULTS for two seconds. Then the display shows EXISTING FAULTS.  Previous faults (PREV FAULTS) If there are only previous faults, the display shows nn PREV FAULTS for two seconds. Then the display shows FAULT HISTORY. If there are existing and previous faults, the display shows nn EXIST FAULTS and nn PREV FAULTS for two seconds each. Then the display shows EXIST-ING FAULTS. EXISTING FAULTS and FAULT HISTORY show faults. Each fault has fault details. For more information on faults and fault details go to the Fault Isolation Manual.

SYSTEM STATUS SYSTEM STATUS has these two submenus:  PRESENT STATUS  SYSTEM CONFIGURATION (SYSTEM CONFIG). ISSUE 1, Rev. 1: 2015.07.10

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ATA 21 AIR CONDITIONING

CPC-BITE (MAIN MENU)

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ATA 21 AIR CONDITIONING

EXISTING FAULTS EXISTING FAULTS shows faults that are present. From the main menu EXISTING FAULTS there are faults and fault details. Faults are maintenance messages of the primary problem. For more information of a fault, there are fault details. From the EXISTING FAULTS menu, you push the YES button. If there are no faults, the display shows NO FAULTS. To go back to the main menu, you push the MENU button. If there is a fault or faults, the first fault shows on the display. To see the next fault you push the NO or down arrow button. If there are no more faults, the display shows BOTTOM OF LIST for 2 seconds. To see the fault details for one of the faults, push the YES button. Then the display shows the fault details for that fault. If you push the NO or down arrow button, the display shows the next fault detail for the same fault. If there are no more fault details, the display shows BOTTOM OF LIST for 2 seconds.

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ATA 21 AIR CONDITIONING

CPC-BITE (EXISTING FAULTS)

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ATA 21 AIR CONDITIONING

FAULT HISTORY FAULT HISTORY shows previous faults that are still in the memory and have not been cleared. From the FAULT HISTORY menu, push the YES button. If there are no faults, the display shows NO FAULT HISTORY. To go back to the main menu, push the MENU button. If there are faults, the display shows FLIGHT 00. To show the next flight leg, push the NO or down arrow button. Then the display shows the next flight leg. If there are no more flight legs in memory, the display shows BOTTOM OF LIST for 2 seconds. The controller can have up to 10 flight legs in memory. Each flight leg can have faults and fault details. To show a fault for a flight leg, push the YES button. The display shows the fault. If you push the NO or down arrow button, the display shows the next fault. If there are no more faults, the display shows BOTTOM OF LIST for 2 seconds. To show fault details for each fault, push the YES button. If you want to see more fault details you push the NO or down arrow button. If there are no more fault details, the display shows BOTTOM OF LIST for 2 seconds.

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ATA 21 AIR CONDITIONING

CPC-BITE (FAULT HISTORY)

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ATA 21 AIR CONDITIONING SYSTEM TEST

SYSTEM TEST does a test of the cabin pressurization system. From the GROUND TEST menu, push the YES button. The display shows DISPLAY TEST. If you push the NO or down arrow button, the display shows SYSTEM TEST. When you push the YES button, the controller does a check to find if the system is in auto mode. If the system is not in auto mode, the display shows SYS IN MANUAL for two seconds. Then the display shows SELECT AUTO. If you push the YES button when the system is in auto mode, the controller does a check to find if the other controller is in BITE. If the other controller is in BITE, the display shows these things:  BOTH SYS IN IBIT for two seconds  IBIT ABORTED for two seconds  SYSTEM TEST. For each of these questions, it is necessary to push the YES or NO button. If you push the YES button after each question, the display shows the next ques¬tion. If you push the YES button after the last question, the display shows TESTING. Each of the 8 lower digits come on for 12 seconds, one digit at a time. This takes approximately 100 seconds. If there is no fault while in test, the display shows SYSTEM OK. Then the dis¬play shows, SYSTEM TEST AND CLEAR?. If you push the YES button, all faults clear from fault history. If you push the NO button, the display shows SYSTEM TEST. If there is a fault during TESTING, the display shows nn EXIST FAULTS for 2 seconds. Then the display shows EXISTING FAULTS menu. If you push the menu button at any time during the system test, the display shows SYSTEM TEST. TRAINING INFORMATION POINT The acronym DADC refers to air data inertial reference unit. The acronym SMC refers to the stall management yaw dampener computer.

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ATA 21 AIR CONDITIONING

CPC-BITE (GROUND TESTS) SYSTEM TEST

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ATA 21 AIR CONDITIONING DISPLAY TEST

DISPLAY TEST does a test of all 16 digits of the LED display. From the GROUND TEST menu, push the YES button. The display shows DISPLAY TEST. If you push the YES button, the test starts. Then four digits at a time turn on for 2.5 seconds. After the test is complete, the display shows DISPLAY TEST

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ATA 21 AIR CONDITIONING

CPC-BITE (GROUND TESTS) DISPLAY TEST

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ATA 21 AIR CONDITIONING

AFT OUTFLOW VALVE ASSEMBLY POSITIVE PRESSURE RELIEF VALVE The aft outflow valve controls the air flow out of the airplane fuselage. LOCATION

The positive pressure relief valves prevent over pressure damage to airplane structure.

The valve is on the lower right fuselage below the aft service door.

LOCATION

PHYSICAL DESCRIPTION

There are two positive pressure relief valves. They are on the lower, aft airplane fuselage. One valve is on each side of the aft outflow valve. You remove the outflow valve to access the positive pressure relief valves.

The outflow valve has these parts:  Valve frame body  Two Valve gates  Actuator assembly and linkage  Position transducer  Two automatic mode motors and one manual mode motor  Two electronic actuator boxes. GENERAL DESCRIPTION The valve is a thrust recovery, double gate type valve. The valve has two 28v dc motors and one 48v dc motor. Only one motor drives the valve at a time. All three motors use the same actuator mechanism. Each electronic drive box on the valve has a fail safe aneroid switch. The switch causes the valve to go fully closed if the cabin pressure altitude reaches 14,500ft. This function overrides normal automatic control only, it will not over¬ride manual operations of the valve. A position transducer on the valve assembly provides a signal to the P5 valve position indicator during all modes of operation. The valve position transducer also sends signals to the two cabin pressure controllers. This gives the controllers valve position feedback for automatic and alternate modes of operation. TRAINING INFORMATION POINT The valve mounting lug fittings let you remove and install the assembly from outside the airplane.

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GENERAL DESCRIPTION The positive pressure relief valves are fail safe devices that bleed fuselage pressure overboard if the aft outflow valve fails closed. The valves are mechan¬ical devices. They operate independently. They do not interface with other airplane pressurization systems and require no crew action. The valves are pneumatically actuated by cabin-to-ambient pressure differen¬tial. When the differential pressure is too high, the valve opens. The open valve lets air out of the airplane. This relieves the cabin pressure. When cabin-to-ambient pressures are safe, the valve closes. The valves have filters. The fil¬ters clean the air used in the valve's internal servo and actuating mechanisms. The valves attach to pedestals with gaskets and a flange clamps. TRAINING INFORMATION POINT Make sure you install the valve and gasket correctly during installation. Incor¬rect installation can block sense ports for the valve servo mechanism. Keep the servo mechanisms dry. Moisture in the mechanism can freeze and prevent valve operation. You must remove the aft outflow valve to access the positive pressure relief valves. Do not reach through the outflow valve or put tools into it. Injury to per-sons or damage to equipment may result.

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ATA 21 AIR CONDITIONING

AFT OUTFLOW VALVE

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ATA 21 AIR CONDITIONING

SAFETY RELIEF VALVE OPERATION Two safety relief valves acting independently of each other and all other systems prevent the cabin-to-ambient pressure differential from exceeding 8.95 psid. Each valve consists of a  poppet valve,  control chamber, and a  spring-loaded diaphragm operated sensor control for controlling the valve opening. The control chamber is vented to the cabin, but has a restrictor in the vent for limiting cabin air inflow. A filter is also installed to prevent contamination in the control chamber. Another passage vents to ambient through the diaphragm operated sensor control poppet. The sensor control is separated by a diaphragm. One side of the diaphragm senses cabin pressure while the other side senses ambient pressure. A differential pressure of 8.95 psi will cause the poppet to unseat opening a vent from the control chamber to ambient. This venting of the control chamber reduces the pressure within the chamber. The valve gate, with control chamber pressure on one side will cause the gate to unseat at approximately 8.95 psi differential pressure as a result of cabin pressure on the other side of the valve gate. The diaphragm operated sensor con-trol ensures that cabin-to-ambient differential pressure does not exceed 8.95 psi.

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ATA 21 AIR CONDITIONING

PRESSURE RELIEF VALVE SCHEMATIC

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ATA 21 AIR CONDITIONING

NEGATIVE PRESSURE RELIEF VALVE The negative pressure relief valve prevents negative differential pressure (vacuum pressure) damage to the airplane structure. This can prevent structure damage during a rapid descent. LOCATION The negative pressure relief valve is on the lower aft fuselage, on the left side, near the aft service door. You access the valve from the aft cargo compartment. GENERAL DESCRIPTION The negative pressure relief valve is a mechanical device and operates independently. It does not interface with other airplane pressurization systems and requires no crew action. The negative pressure relief valve is a flapper type valve. The valve hinges on its top edge and opens inward. A spring on its hinge pin holds the valve closed. Negative differential cabin-to-ambient pressure opens the valve. The valve opens when pressure outside of the airplane is 1.0 psi more than the pressure inside of the airplane (-1.0 psid). A stand pipe can be attached to the relief valve assembly. The stand pipe keeps water out of the airplane during ditching. Water enters the valve until the weight of the water column in the stand pipe closes the valve.

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ATA 21 AIR CONDITIONING

NEGATIVE PRESSURE RELIEF VALVE

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ATA 21 AIR CONDITIONING

CARGO COMPARTMENT BLOWOUT PANEL GENERAL DESCRIPTION The cargo compartment blowout panels prevent damage to the airplane struc¬ture during sudden decompression. LOCATION The cargo compartment blowout panels are in these places:  Cargo compartment ceilings  Cargo compartment bulkheads. GENERAL DESCRIPTION The cargo compartment blowout panels are held in place by frames. During rapid decompression, the differential pressures push the panels out of their frames. This lets pressures in the upper and lower fuselage lobes equalize quickly. This prevents damage to flight critical structure. The blowout panels on the cargo compartment bulkheads have grates. The grates do not let baggage hit the blowout panels.

The cargo compartments are tightly sealed by a fire resistant liner. The liner isolates the cargo compartments from the airplane air conditioning system. This is necessary for fire protection (class D requirements). The pressure equalization valves isolate the cargo compartments from active air conditioning, but let cargo compartment pressures change. The cargo compartment pressure equalization valve is a swing check valve assembly. Each assembly has two valves:  One valve lets air into the cargo compartment during airplane pressurization  One valve lets air out of the cargo compartment during airplane depressurization.

CARGO COMPARTMENT PRESSURE EQUALIZATION VALVES The cargo compartment pressure equalization valves let the pressures in the cargo compartments change. LOCATION The cargo compartment pressure equalization valves are on the bulkheads in the cargo compartments.

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ATA 21 AIR CONDITIONING

BLOWOUT PANELS

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Boeing 737-600/700/800/900 (CFM 56) subcat. B1.1

ATA 21 AIR CONDITIONING  Pressurize the cabin to an optimal pressure altitude  Limit the rate of cabin pressure change to a comfortable rate 600 slfpm.

AUTO MODE FLIGHT PROFILE The automatic (AUTO) mode of the pressurization control system controls airplane pressure for all phases of flight:  Unpressurized ground operations  Takeoff pressurization  Takeoff and climb  Cruise  Descent and landing. CONTROL MODULE SELECTIONS To use the AUTO mode, make these selections on the control module;  AUTO mode select  •FLT ALT set  LAND ALT set. UNPRESSURIZED GROUND OPERATIONS During ground operations the outflow valve is wide open and the airplane is unpressurized. TAKEOFF PRESSURIZATION When the airplane is in the takeoff phase, the system pressurizes the airplane to approximately 0.1 psid below field elevation. This occurs when either of these conditions exist:  Both engine N1 s more than 60 % for 1.5 seconds  Both engine N2s more than 89 % for 1.5 seconds. This makes a positive airflow at the outflow valve. The positive outflow prevents the uncomfortable "pressure bump" (momentary pressure increase) airplane rotation can cause at takeoff. The close proximity of the outflow valve to the runway at rotation causes a ram air effect. This causes momentary "pressure bump" in an unpressurized airplane. TAKEOFF AND CLIMB During takeoff and climb, the system controls the cabin pressurization to do these things: ISSUE 1, Rev. 1: 2015.07.10

CRUISE When the airplane is within 0.25 psid of the FLT ALT selection (capture cruise altitude), the system transfers to the cruise phase. The controller maintains an isobaric schedule (constant pressure differential). This reduces the wear on mechanical components and reduces pressure cycl¬ing of the fuselage structure. Cabin pressure altitude shall not exceed 8,000 feet mean sea level (this prevents oxygen starvation). Cabinto-ambient pres¬sure differentials shall be minimal (this minimizes pressure cycling of fuselage structure). The controller determines the optimal cabin pressure altitude based on the FLT ALT setting and conditions as listed below:  The air conditioning system can supply sea-level pressure in the cabin at any altitude below 18.500 ft.  Between 18.500 ft and 28.000 ft, the cabin can be pressurized as much as 7.45 psi greater than ambient pressure.  Between 28.000 ft and 37.000 ft, the cabin can be pressurized as much as 7.8 psi greater than ambient pressure.  Above 37.000 ft the cabin can be pressurized as much as 8.35 psi greater than ambient pressure.  8.45 psid is the maximum pressure differential the AUTO mode will allow. DESCENT AND LANDING When the airplane descends to 0.25 psid of the FLT ALT selection, the system is in the descent phase. When the airplane starts its descent, the system con¬trols the cabin pressurization to do these things:  Pressurize the cabin for positive landing pressure  Limit the rate of cabin pressure change to a comfortable rate (350 slfpm). The cabin pressurizes to approximately 0.15 psid for landing. This makes a positive airflow at the outflow valve. The positive outflow prevents the pressure bump airplane flare can cause during landing. On the ground, the system depressurizes the airplane when either of these conditions exist:  Both engine N1 less than 50 % for 1.5 seconds  Both engine N2 less than 84 % for 1.5 seconds.

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ATA 21 AIR CONDITIONING

AUTO MODE FLIGHT PROFILE

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ATA 21 AIR CONDITIONING

AUTO MODE FUNCTIONAL DESCRIPTION The automatic (AUTO) mode of the pressurization control system keeps the airplane pressurized for all phases of the flight. The AUTO mode circuitry has these parts:  Redundant 28v dc power sources  Cabin pressure control module (P5-6)  Two digital cabin pressure control (CPCs) units  Two AUTO mode dc motors with drive electronics boxes on the aft outflow valve assembly  Circuit wiring and connectors. When the control module mode selector is in the AUTO position, it sets the pressurization control system to automatic operation. The automatic control system has a dual redundant architecture. The two CPCs are identical and interchangeable. Rack pin connections identify the con¬trollers as CPC No. 1 and CPC No. 2 to the system. Only one CPC controls the outflow valve at any time. The other CPC is a back-up. At system power-up, the No.1 CPC becomes the active controller. The system switches active control from one CPC to the other with each flight. This keeps wear equal on the mechanical drive components of the two systems.

The air conditioning pack valves and the overboard exhaust valves give position feedback to the CPC. This biases the CPC response algorithms. Both controllers run continuous BITE tests. If the active CPC system becomes inoperative, the other CPC system automatically takes control (ALTN mode).

The CPCs use data from these systems to determine flight phase:  Both air data inertial reference units (ADIRUs)  Both stall management and yaw damper computers (SMYDCs)  The proximity switch electronics unit (PSEU). The CPC determines a target cabin pressure in response to:  P5-6 control module inputs  Flight phase. The CPC compares the target pressure to the pressure at it's sense port. If a difference exists the CPC sends an open or close command to its drive electronics box on the aft outflow valve assembly. The drive electronics box operates its valve motor. The motor moves the outflow valve through a mechanical drive train. In this way, the active controller modulates the aft outflow valve to control cabin pressure and rate of pressure change. Outflow valve position feedback to the CPC verifies proper valve operation (closed loop feedback).

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ATA 21 AIR CONDITIONING

AUTO MODE FUNCTIONAL SCHEMATIC

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Boeing 737-600/700/800/900 (CFM 56) subcat. B1.1

ATA 21 AIR CONDITIONING AUTO FAIL DUAL CHANNEL FAILURE

The AUTO FAIL light gives the flight crew indication that the active CPC system is inoperative. The automatic pressurization control system has a dual redundant architecture. One digital cabin pressure controller (CPC) is active and maintains pressurization control. The other CPC is a backup. If the active CPC channel fails, the system transfers pressurization control to the backup (alternate) CPC channel. The two CPCs automatically run start—up and continuous BITE tests. These tests check both systems to the LRU level. When the active CPC BITE detects a fault or failure, it transfers active control to the backup CPC. These things cause the auto fail function:  Power loss  Cabin altitude rate of change is too high (>2,000 slfpm)  Cabin altitude is too high (>15,800 ft)  Wiring failures  Outflow valve component failures  CPC failures.  Cabin differential pressure is too high (>8.75psi).

These are the indications when both CPC systems fail:  The AUTO FAIL and master caution lights come on  The FLT ALT and LAND ALT displays show five dashes (- - - - -). If both CPCs fail, the ALT light does not come on. This indicates that the system cannot transfer control to an operative automatic channel. If both automatic channels fail, you must use the MANUAL mode of pressurization control. The auto fail function does not transfer pressurization control to the manual system. You must select MANUAL on the pressurization mode selector. When you select MANUAL these things happen:  Pressurization control transfers to the MANUAL system  The two CPC systems are disabled  The P5-6 AUTO FAIL Light goes out  The P5-6 MANUAL Light comes on.

SINGLE CHANNEL FAILURE The system automatically transfers pressurization control to the backup chan¬nel if the active channel fails. If the system is in the AUTO mode when an auto fail event occurs, these lights come on:  The AUTO FAIL light  The Master Caution and AIR COND annunciator lights  The ALTN light. The ALTN light gives indication that the backup system is active. The AUTO FAIL light goes off when you select the ALTN position on the mode selector. If the system is in the ALTN mode when an auto fail event occurs, the AUTO FAIL and Master Caution Lights come on. These lights, and the ALTN light will go off when you select the AUTO mode on the control module.

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Boeing 737-600/700/800/900 (CFM 56) subcat. B1.1

ATA 21 AIR CONDITIONING

AUTO FAIL SCHEMATIC

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ATA 21 AIR CONDITIONING

OFF SCHEDULED DESCENT If it is necessary to land immediately after takeoff, the pressurization control system automatically programs the pressurization system for landing. The OFF SCHED DESCENT indication is part of this feature. The light tells you that the system will control cabin pressure for a return to the take-off field. The off schedule descent feature only works in the AUTO and ALTN modes. It is not a feature of the MANUAL mode. An off schedule descent begins when the airplane starts to descend off schedule (before it reaches cruise altitude). FUNCTIONAL DESCRIPTION If the airplane begins a descent before it reaches the FLT ALT selected on the control module, these things happen:  The OFF SCHED DESCENT Light comes on  MASTER CAUTION and AIR COND annunciator lights come ON  The pressurization control system automatically schedules the cabin pressure for return to take-off field. The OFF SCHED DESCENT Light will go out if these conditions occur:  The airplane begins to climb again  The FLT ALT is reset to the current altitude  The pilot selects manual (MAN) mode  The airplane lands. If the airplane aborts its mission, and diverts to an field other than the takeoff field, the flight crew must reset the pressure controller:  Select FLT ALT to 200 feet less than airplane altitude (flight cruise altitude capture)  Set the landing altitude in the LND ALT window on the selector panel to the landing field elevation. The pressure control system cancels the off schedule descent feature for the flight when the airplane reaches the FLT ALT set on the P5-6 control module.

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Boeing 737-600/700/800/900 (CFM 56) subcat. B1.1

ATA 21 AIR CONDITIONING

OFF SCHEDULE DESCENT CIRCUIT

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ATA 21 AIR CONDITIONING

MANUAL MODE FUNCTIONAL DESCRIPTION The manual control mode gives the flight crew direct control of the outflow valve. GENERAL DESCRIPTION The MANUAL mode has these parts:  28v dc bat bus power source  Cabin pressure control module (P5-6)  MANUAL mode DC motor on the aft outflow valve assembly  Circuit wiring and connectors. When the control module mode selector is in the MANUAL position, it configures the pressurization control system for manual operation. These things happen:  The automatic control systems are disarmed  The control module outflow valve switch arms  The MANUAL system indication light comes on. The aft outflow valve switch is a three position toggle switch. These are the three positions  CLOSE  Neutral  OPEN. The switch is spring loaded to the neutral position. Signals from the control module outflow valve switch go directly to the manual motor on the aft outflow valve assembly. When the switch is in the CLOSE position, the motor closes the valve. When the switch is in the OPEN position, the motor opens the valve. The position transducer on the aft outflow valve assembly gives valve position feedback to the control module outflow valve position indicator. You can use the instruments on the P5-16 cabin altitude panel for reference during manual operation of the pressurization system:  The pressure limitation placard  The cabin/flight altitude conversion placard  The cabin altitude and differential pressure indicator  The cabin rate of climb indicator.

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Boeing 737-600/700/800/900 (CFM 56) subcat. B1.1

ATA 21 AIR CONDITIONING

PRESSURE CONTROL MANUAL MODE

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ATA 21 AIR CONDITIONING

MANUAL MODE CONTROL The pressurization outflow valve can operate in the manual mode. To do this, put the pressurization mode selector to the MANUAL position. The valve can then be opened or closed by the outflow valve switch. The pressurization mode selector and the outflow valve switch are on the cabin pressure control panel on the P5 overhead panel. FUNCTIONAL DESCRIPTION When the pressurization mode selector is in the MANUAL position, these things happen:  The green MANUAL light comes on  CPC 1 and CPC 2 stop automatic and alternate modes of valve operation. When the outflow valve switch is in the open or close position, these things happen:  The manual motor booster changes 28v dc to 48v dc for valve motor operation  Power from the booster goes to the valve manual motor.  The direction of valve operation for the open/close functions is controlled by change of the power supply and return by the switch positions. TRAINING INFORMATION POINT You can do a check of the valve operation with the manual mode of valve operation.

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Boeing 737-600/700/800/900 (CFM 56) subcat. B1.1

ATA 21 AIR CONDITIONING

MANUAL MODE ELECTRICAL SCHEMATIC

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Boeing 737-600/700/800/900 (CFM 56) subcat. B1.1

ATA 21 AIR CONDITIONING

CABIN PRESSURE INDICATION AND ALTITUDE WARNING SYSTEM The cabin pressure indication and altitude warning system does these things:  Shows cabin pressure altitude  Shows cabin-to-ambient differential pressure  Shows cabin rate of climb  Gives the crew an aural signal (with cutout) wher cabin pressure altitude is 10,000 feet or higher. LOCATION These components are on the cabin altitude panel (P5-17):  Pressure indicators  Warning circuits  Cutout switch. The pressure switch is on the ceiling of the lower nose compartment. The warning horn is in the aural warning box on the control stand. PRESSURE INDICATION The cabin altimeter/differential pressure indicator shows these things:  Cabin pressure altitude (short needle and inner scale)  Cabin-to-ambient differential pressure (long needle and outer scale). The cabin rate of climb indicator shows the rate of change in cabin pressure altitude. WARNING SYSTEM The aural signal is an intermittent beep. The cabin altitude warning switch is an aneroid type switch. When the cabin altitude reaches 10,000 ft above mean sea level the pressure warning switch closes. This energizes the warning circuit and causes the intermittent warning horn to sound. The cutout push-button switch allows the crew to deactivate the warning alarm until the next high cabin altitude event.

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Boeing 737-600/700/800/900 (CFM 56) subcat. B1.1

ATA 21 AIR CONDITIONING

CABIN PRESSURE AND ALTITUDE WARNING SYSTEM

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Boeing 737-600/700/800/900 (CFM 56) subcat. B1.1

ATA 21 AIR CONDITIONING

CABIN ALTITUDE WARNING The cabin altitude warning system warns the flight crew before cabin pressure altitude becomes unsafe. OPERATION The cabin altitude pressure switch is a normally open contact aneroid type switch. The switch will close if the cabin pressure altitude is 10,000 feet or higher. When the switch closes, these things happen:  The switch grounds the horn circuit, which energizes the system  The aural warning module makes an intermittent beep alarm.

When you press the HORN CUTOUT switch on the P-5 panel, these things happen:  The K1 relay energizes through the closed pressure switch  When K1 energizes the aural warning circuit OPENS and removes the ground signal to the aural warning module  The horn circuit loses power and the horn goes off  K1 latches itself through the pressure switch. When the cabin altitude descends below 10,000 feet, the pressure warning switch opens, and these things happen:  K1 de-energizes  The warning circuit is reset for the next event.

CABIN ALTITUDE WARNING CIRCUIT

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Boeing 737-600/700/800/900 (CFM 56) subcat. B1.1

ATA 21 AIR CONDITIONING

Service Bulletin (SB 737-21-1165)

Cabin Altitude Warning System and Takeoff Configuration Warning System Lights (SB 737-31A1332)

This service bulletin gives instructions to make changes to the Cabin Altitude Warning System. These changes will install a second 10,000 foot cabin altitude pressure switch and new Aural Warning Module (AWM) M315. If the changes in this service bulletin are not done, the cabin altitude warning may not function if there is a failure of the 10,000 foot altitude pressure switch. Boeing received a report from an operator that they had experienced a cabin depressurization. The flight crew were not aware of the cabin depressurization and that the oxygen masks had been deployed until they were informed by a member of the cabin crew. An investigation found that the flight crew did not get an aural warning because of the failure of the cabin altitude 10,000 foot pressure switch. The installation of the second 10,000 foot pressure switch and a new digital AWM M315 with two fully independent channels and separate power supplies will reduce the possibility of the flight crew being not aware of a depressurization event.

Following the “Helios accident” where the crew did not correctly identify the cabin altitude warning horn, new red "CABIN ALTITUDE" and "TAKEOFF CONFIG" warning lights were fitted to the P1-3 & P3-1 panels to supplement the existing aural warning system.

P1-3 PANEL BEFORE AND AFTER MODIFICATION

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