ATA 21 AIR CONDITIONING FOR AIRBUS 320.pdf

Airbus A318/A319/A320/A321 (CFM56) and (IAE V2500) ATA 21
Continuation training AIR CONDITIONING&PRESSURIZATION
TRAINING MANUAL
Airbus A318/A319/A320/A321 (CFM56) and
Airbus A319/A320/A321 (IAE V2500)
Continuation training
21. AIR CONDITIONING & PRESSURIZATION
(ATA21)
ISSUE 1, 17 Sep 2015 FOR TRAINING PURPOSES ONLY Page: 1

THIS PAGE IS INTENTIONALLY LEFT BLANK

TABLE OF CONTENTS
COOLING PACK SCHEMATIC .................................................................... 12
ABNORMAL PACK OPERATIONS .............................................................. 16
COCKPIT AND CABIN TEMPERATURE CONTROL................................... 18
AIR CONDITIONING ENHANCED................................................................ 24
PACK SYSTEM DESCRIPTION / OPERATION ........................................... 24
AIR CONDITIONING ENHANCED................................................................ 26
PACK SYSTEM DESCRIPTION / OPERATION ........................................... 26
EMERGENCY RAM AIR INLET.................................................................... 29
GENERAL VENTILATION - SYSTEM DESIGN PHILOSOPHY .................... 31
AVIONICS EQUIPMENT VENTILATION...................................................... 33
PRESSURIZATION CONTROL .................................................................... 40
MAIN COMPONENTS AND SUBSYSTEMS................................................. 42
OUTFLOW VALVE ....................................................................................... 48

TABLE OF FIGURES
AIR CONDITIONING SYSTEM LAYOUT ....................................................... 7
AIR COND PANEL .........................................................................................8
AIR CONDITIONING - GENERAL .................................................................. 9
FLOW CONTROL......................................................................................... 11
COOLING PACK SCHEMATIC .................................................................... 13
CRUISE AND CABIN PRESS SYSTEM DISPLAY....................................... 14
AIR CONDITIONING AND VENTILATION PANEL ...................................... 15
PACK COOLING DIAGRAM ........................................................................ 17
COCKPIT AND CABIN TEMPERATURE CONTROL COMPONENT
FUNCTION ................................................................................................... 19
ZONE CONTROLLER FAILURE CONSEQUENCES................................... 20
ZONE CONTROLLER FAILURE CONSEQUENCES................................... 21
PACK CONTROLLER FAILURE CONSEQUENCES................................... 22
IN THE BACK-UP MODE, THE FCV FLOW IS CONTROLLED BY A
DOWNSTREAM PRESSURE REGULATOR................................................ 24
ENHANCED AIR COOLING SYSTEM.......................................................... 25
EMERGENCY RAM AIR INLET OPERATION.............................................. 30
GENERAL VENTILATION – SYSTEM DESIGN PHILOSOPHY................... 32
AVIONICS VENTILATION SYSTEM PRESENTATION................................ 34
VENTILATION PANEL ................................................................................. 35
AVIONICS SMOKE....................................................................................... 36
SKIN AIR INLET VALVE DEACTIVATION................................................... 37
SKIN AIR OUTLET VALVE DEACTIVATION SWITCH................................ 38
CABIN PRESSURIZATION SYSTEM - SCHEMATIC................................... 44
CABIN PRESSURE PANEL......................................................................... 45
ECAM SYSTEM DISPLAY ........................................................................... 46
ECAM DISPLAYS ........................................................................................ 47
SAFETY VALVE........................................................................................... 50

INTRODUCTION
Purpose
The air conditioning system maintains the air in the pressurized fuselage
compartments at the correct levels of :
− pressure, temperature and freshness.
Under normal conditions, the pneumatic system supplies air to the air
condtioning system from:
− the main engine compressors,
− the APU compressor,
− a high pressure ground air supply unit.
The hot compressed air is cooled, conditioned and delivered to the following
fuselage compartments:
− Flight Compartment
− Passenger Compartment
− Avionics Compartment
− Cargo Compartment
The air is then discharged overboard through the outflow valve 10HL.
Conditioned air can also be supplied to the distribution system through a low
pressure ground connection. A ram−air inlet supplies emergency air to the
fuselage should the air generation system malfunction during flight.
Air Conditioning Sub systems
The air conditioning system includes the following sub systems :
− Lavatory / galley ventilation system
− Avionics Equipment Ventilation
− Pressurization Control
− Aft / FWD Cargo Heating ( option )

AIR CONDITIONING SYSTEM LAYOUT

General Description
Warm pre-conditioned bleed air enters the cooling pack via the variable Flow
Control Valve (FCV). The two independent packs provide regulated
temperature air through non return valves to the mixing unit. The packs
incorporates a three-wheel "Bootstrap" air cycle machine with air to air heat
exchangers. Both packs outlet temperatures are normally controlled to the
coldest temperature demand of the three zones. Each pack has its own
controller for monitoring and control. The mixing Unit mixes regulated
temperature air from the packs with part of the cabin air supplied by
recirculation fans. The mixing unit may also provide conditioned air from a
low pressure ground connection or fresh outside air from the emergency
Ram Air Inlet. The emergency Ram Air Inlet provides outside fresh air
ventilation of the aircraft in emergency conditions (loss of both packs or
smoke removal). Hot air tapped upstream of the packs supplies the trim air
valves through a hot air Pressure Regulating Valve. This valve regulates the
downstream pressure above the cabin pressure. A trim Air Valve associated
with each zone optimize the temperature by adding hot air if required, to the
cold air coming from the mixing unit. The conditioned air is distributed to
three main zones:
- cockpit
- forward cabin
- aft cabin
Normally the mixing unit allows the cockpit to be supplied from pack 1 and
fwd and aft cabins from pack 2. Air may be exhausted out through the:
- Lavatory/Galley ventilation system.
- Avionic Equipment ventilation System.
- Outflow valve which is controlled by the pressurization system.
The lavatory and galley ventilation system uses air from the cabin zones. A
fan extracts this air through the outflow valve. The system also ventilates the
cabin zone temperature sensors.
AIR COND PANEL

AIR CONDITIONING - GENERAL

Flow Control
The pack Flow Control Valve (FCV) have two functions:
- Pneumatically regulates the air flow automatic or manually selected.
- Provides an automatic or manually selectable shut-off of airflow. In
case of cabin depressurization, the FCV stays open.
The pack FCV is electrically controlled to closed:
- During engine start.(reopens 30 sec after first engine start).
- If engine fire pushbutton released out.
- If ditching pushbutton set to ON.
- If pack pushbutton set to OFF. Pneumatically controlled to closed if:
- Pack overheat (230-260°C)
Lack of air pressure. The airflow depends on:
- Selected, (man or auto)
- Cabin pressure.
- Compressor discharge temperature.
Normal Flow Control
The primary computer sets the optimized flow demand reference computed
and sent by the zone controller. If "LO" is selected and heating or cooling
demand cannot be met, the zone controller automatically provides a normal
flow and if necessary increases the engine power. During APU bleed air
operation the zone controller automatically provides "HI" mode operation. If
one pack FCV is closed the other pack controller will select its related pack to
"HI" mode. The pack airflow can manually be selected to:
- "LO" (80%) if number of passengers is below 81.
- "NORM" (100%) during normal operation.
- "HI" (120%) for abnormal hot ambient condition or to clear smoke.

FLOW CONTROL

COOLING PACK SCHEMATIC
Air Cycle Machine
The Ajr Cycle Machine (ACM) consist of a rotating shaft on which a turbine, a
compressor and a fan are mounted. The shaft rotates on two self-acting foil-
air bearings and a double self-acting air- thrust bearing which takes the axial
thrust loads.
Air Inlet / Outlet Flaps
The bypass valve, the RAM AIR inlet and outlet valves are simultaneously
controlled by the pack controller. The Ram Air Inlet and Ram Air Outlet flaps
are electrically controlled and actuated and are provided to modulate the air
flow through the exchangers. Limit switches provide signals for closed and
70% open position. To increase cooling, the RAM AIR flaps simultaneously
open more and the BYPASS Valve closes more. To increase heating, the
RAM AIR flaps close more and the BYPASS Valve opens more.
Bypass Valve
The Bypass Valve (BPV) is electrically controlled and actuated by a stepper
motor to modulate the pack discharge temperature by adding hot air. It gets
signal from the pack primary and secondary computer to modulate the hot air
flow to control water extractor outlet temperature. Potentiometers send
signals to the primary computer for indication and to the secondary computer
for BITE and indication. Limit switches signal fully open or closed position to
the secondary computer. In case of no electrical power the Bypass valve is
1% open under pressure.
Anti-Ice Valve
Icing of the pack condenser is prevented with the anti-ice valve. During
normal operation its energized. There are two pairs of pressure sense lines.
One on the high pressure side of the condensed inlet/outlet, the other on the
low pressure side of the condenser inlet/outlet. If an excessive pressure drop
is detected, the anti-ice valve is opened pneumatically. This results in a surge
of hot air to the turbine outlet, which clears the ice blockage. In case of
complete pack controller failure, the solenoid is de-energized and the anti-ice
valve is controlled by the pack pneumatic sensor to control the pack outlet
temperature to 15°C.
Water Extractor
The Water Extractor contains swirl vanes which centrifuge the water droplets
in the air to the inner surface of the water extractor body.

COOLING PACK SCHEMATIC

CRUISE AND CABIN PRESS SYSTEM DISPLAY

AIR CONDITIONING AND VENTILATION PANEL

ABNORMAL PACK OPERATIONS
Single Air Condition Pack Mode
The aircraft can fly with one air conditioning pack inoperative provided:
− FL310 is not exceeded,
− the zone controller primary channel is operative,
− the PACK FLOW Selector is set to HI (A320) or set ECON FLOW P/B
Switch to OFF (A321)
− the affected PACK 1 or 2 pushbutton switch is in the OFF position
and the flow
− control valve is checked closed on the ECAM system.
Heat Exchanger Cooling Mode
One air conditioning pack can also be operated on heat exchanger cooling
only provided:
− the corresponding pack controller is fully operational
− the TAT indication is available,
− the affected pack is not operated until the aircraft is airborne,and the
TAT is less than 12° C,and affected PACK OUTLET TEMP indication
is available,and the remaining pack is operating normally.

PACK COOLING DIAGRAM

COCKPIT AND CABIN TEMPERATURE CONTROL
Mixer Unit
The mixer unit mixes air from packs and recirculated air from the cabin prior
to distribution to each zone. The mixer unit, installed under the cabin floor,
uses cabin air which has entered to underfloor area and has been drawn
through recircuiation filters by recirculation fans. This air is mixed with
conditioned air from the packs. The quantity of cabin air mixed with
conditioned air varies from 37% to 51%.
Mixer Unit Sensors
There are two mixer unit temperature sensors, one on either side of the mixer
unit. They indicate the actual temperature of the mixer unit to the zone
controller. Each mixer unit temperature sensor consists of two thermistors.
One connected to the primary computer and the other to the secondary
computer.
Mixer Unit Flap
The mixer unit flap ensures sufficient flight deck air supply if pack 1 is
selected off. An electrically operated mixer unit flap is installed to ensure that
sufficient fresh air is delivered to the cockpit in case of pack 1 failure.
Trim Air Pressure Regulating Valve (PRV)
The trim air Pressure Regulating Valve is pneumatically operated and
electrically controlled by two solenoids. One solenoid controls the ON/OFF
functions and the second solenoid controls the safety function. The trim air
Pressure Regulating Valve regulates the pressure of the air supplied to the
trim air valves, 4 PSI above the cabin pressure. When any duct temperature
goes above 80°C (176°F), the safety function solenoid S1 is energized and
reduces downstream pressure of the valve, from 4 PSI to 2 PSI above the
cabin pressure. It will be deenergized as soon as the temperature returns
below 70°C (158°F). The ON/OFF function solenoid S2 is deenergized when
the HOT AIR pushbutton is set to OFF or when any duct temperature is
above 88°C (190°F) or above 80°C (176°F) four times in one flight leg.
This closes the
valve.
Trim Air Pressure Switch
The trim air pressure switch signals overpressure, due to a malfunction of the
trim air Pressure Regulating Valve, to the secondary computer of the zone
controller for ECAM display and the Centralized Fault Display System
(CFDS). If pressure in the system goes to 6.5 PSI above the cabin pressure,
the zone controller activates the ECAM system. This signal stays until the
pressure falls below 5 PSI.
Trim Air Valves (TAV)
The Trim Air Valves allow the zone temperature to be adjusted by modulating
the hot air flow added to air from the mixer unit. The TAVs close when the
trim Air Pressure Regulating Valve closes. The butterfly of the Trim Air
Valves is controlled by a stepper motor.
Duct Temperature Sensors
Each duct temperature sensor detects duct temperature for the
corresponding zone temperature control, indication and overheat detection to
the zone controller. Each duct temperature sensor consists of two
thermistors, one connected to the primary computer and the other to the
secondary computer. Each thermistor provides control, indication and
overheat detection (88°C (190°F) or 4 x 80°C (176°F)).

COCKPIT AND CABIN TEMPERATURE CONTROL COMPONENT FUNCTION

ZONE CONTROLLER FAILURE CONSEQUENCES

PACK CONTROLLER FAILURE CONSEQUENCES

AIR CONDITIONING ENHANCED
Enhanced Cooling
The enhanced Air Conditioning system is designed with several changes.
On the new Air Conditioning System, several components are replaced:
- New Air Conditioning System Controllers (ACSCs)
- Flow control valve (FCV)
- Ram air inlet actuator (RAIA)
- Anti-ice valve (AIV)
- Air conditioning panel 30 VU
Pack Temperature
Sensor
Some other are
deleted:
Pack Outlet Pneumatic Sensor (POPS)
Compressor Pneumatic OverHeat sensor
(CPNOH) Pack flow sensor
Pneumatic sensing pipe lines
On the enhanced aircraft the new pack system includes two new ACSCs,
an electrically controlled AIV, an improved FCV with integrated pressure
sensors and an improved RAIA with speed and direction sensors.
On the air conditioning panel the pack flow selector is replaced by a
HI FLOW push button which enables NORM or HI flow.
PACK SYSTEM DESCRIPTION / OPERATION
Flow Control Valve
The FCV is an electro-pneumatic butterfly valve with the following
main functions:
control of the mass flow of bleed air entering the pack.
isolation of the pack from the bleed air supply (crew selection, engine
fire, ditching, or engine start).
Air cycle machine overheat and low pressure start up protection
(controlled by the ACSC). ACSC1 controls the FCV for pack 1, while
ACSC2 controls the FCV for pack 2. Under normal conditions, each
ACSC uses a closed loop electronic control circuit to regulate the
butterfly position and resulting pack inlet flow. The FCV has two modes of
operation:
- main: electrical control (100% to 144%)
- back-up: pneumatic control (140% to 174%)
In the main operating mode, the FCV position is modulated to respond
to:
changing flow demands
control priorities (take-off, landing, pack start, etc.)
failures and pack overheat conditions.
In the back-up mode, the FCV flow is controlled by a downstream
pressure regulator

ENHANCED AIR COOLING SYSTEM

AIR CONDITIONING ENHANCED PACK SYSTEM DESCRIPTION / OPERATION
Enhanced Cooling
The enhanced Air Conditioning system is designed with several changes. On
the new Air Conditioning System, several components are replaced:
- New Air Conditioning System Controllers (ACSCs)
- Flow control valve (FCV)
- Ram air inlet actuator (RAIA)
- Anti-ice valve (AIV)
- Air conditioning panel 30 VU
Pack Temperature Sensor
Some other are deleted:
Pack Outlet Pneumatic Sensor (POPS)
Compressor Pneumatic OverHeat sensor (CPNOH)
Pack flow sensor
Pneumatic sensing pipe lines
On the enhanced aircraft the new pack system includes two new ACSCs, an
electrically controlled AIV, an improved FCV with integrated pressure sensors
and an improved RAIA with speed and direction sensors. On the air
conditioning panel the pack flow selector is replaced by a HI FLOW push
button which enables NORM or HI flow.
Flow Control Valve
The FCV is an electro-pneumatic butterfly valve with the following main
functions:
control of the mass flow of bleed air entering the pack.
isolation of the pack from the bleed air supply (crew selection, engine fire,
ditching, or engine start).
Air cycle machine overheat and low pressure start up protection (controlled
by the ACSC). ACSC1 controls the FCV for pack 1, while ACSC2 controls
the FCV for pack 2. Under normal conditions, each ACSC uses a closed loop
electronic control circuit to regulate the butterfly position and resulting pack
inlet flow. The FCV has two modes of operation:
- main: electrical control (100% to 144%)
- back-up: pneumatic control (140% to 174%)
In the main operating mode, the FCV position is modulated to respond to:
changing flow demands
control priorities (take-off, landing, pack start, etc.)
failures and pack overheat conditions.
In the back-up mode, the FCV flow is controlled by a downstream
pressure regulator.

Anti Ice Valve
The AIV is operated by an electro-mechanical actuator. The valve is
controlled by the ACSC. The AIV main function is to remove ice build-up from
components downstream of the turbine outlet (condenser tubing, temperature
sensors, check valves, mixing unit). The ACSC uses the Pack Discharge
Pressure Sensor (PDPS) to compare the pack discharge pressure to the
turbine outlet pressure. If the difference between these two pressures
exceeds a predetermined limit, then icing is assumed. As a result, the ACSC
will command the AIV to open, hot air flows directly into the turbine outlet and
pack discharge. This hot air will melt the ice, causing the pack discharge
pressure to return to a normal value. Once the pressures are within a certain
limit, the AIV will fully close. The AIV is identical and interchangeable with the
system Trim Air Valves (TAV).
Pressure Sensors
Each pack has 3 pressure sensors. These sensors are used for the following
purposes:
flow control, actual flow calculation
icing detection
The PDPS detect an increase in the ACM turbine outlet pressure relative to
the aircraft cabin. This indicates icing conditions exist.
Ram Air Inlet Actuator
The Ram Air Inlet Actuator (RAIA) is monitored and controlled by the ACSCs.
Air Conditioning System Controller (ACSC)
The ACSC is a 2 lane, fully redundant computer system with independent
central, processing units and duplicated hardware interfaces. One lane is
active while the other lane is passive ("hot-standby"). If the active lane is not
able to control the system, the passive lane will become active and take over
system control. The active lane switches at each aircraft landing, assuming
the passive lane has no faults which are more severe than those in the active
lane. The ACSCs perform the following functions:
- temperature control
- zone control
- mixer-pack control
- flow control (pack FCV)
- demand calculation
- pack flow
- pack temperature
- overheat monitoring/ control (pack and ducts)
- ACS component monitoring and fault detection
- ACS failure storage
- data exchange (ACSC1, ACSC2, A/C systems)
ACSC1 and ACSC2 have different functions. Functional differences between
the two controllers are determined by pin programming after installation in the
aircraft. In general, the functions allocated to each controller are as follows:
ACSC1:
control of F/D zones, trim system and trim air pressure relief valve, wing and
nacelle anti ice logic.
ACSC2:
control of cabin zones and trim system, CFDS interface and fault storage,
wing anti ice fault analysis, mixer flap drive and monitoring.
The ACSCs 1 and 2 interface with:
- the engine FADEC system for pack shut down during engine start
- the APU ECB for increased or decreased bleed air flow according to
pack demand.
Cockpit and Cabin Description /Operation

EMERGENCY RAM AIR INLET
General
The aircraft is equipped with one emergency ram inlet flap located at the
lower left-hand side of the fuselage, sharing the same duct with the low
pressure ground connector.
Emergency Ram Air Inlet Flap Operation
In case of failure of both packs, an emergency ram air inlet flap can be
opened for aircraft ventilation or smoke removal. In case of smoke removal or
loss of both packs, the RAM AIR pushbutton must be set to ON. When the
RAM AIR switch (4HZ) is set to ON, and if DITCHING is not selected, the
RAM AIR INLET FLAP (7HZ) opens. The flap installed between LP GND
CONNECTION and RAM AIR INLET, closes one side of the duct when air is
supplied from the other side. The emergency ram air inlet check valve
(4022HM) prevents backflow from the mixer unit. For passenger safety the
aircraft must descent to less than 10'000 ft. When the cabin to ambient
pressure is less than 1 PSI, the active pressure controller half opens the
outflow valve, provided the pressurization system is in automatic mode.

EMERGENCY RAM AIR INLET OPERATION

GENERAL VENTILATION - SYSTEM DESIGN PHILOSOPHY
Avionics
The avionics ventilation system ensures a proper ventilation of the electrical
equipment. Air is taken from different sources depending on the aircraft
configuration and ambient conditions.
Ventilation air is blown to the equipments by a blower fan and extracted by
an extraction fan.
LAV & Galleys
The lavatory and galleys ventilation system is used to remove unpleasant
odors before they enter the cabin. Ventilation air is supplied from cabin
distribution ducts and discharged overboard by an extraction fan.
Cargo (Option)
The FWD & AFT cargo compartments are ventilated by cabin ambient air
coming from the cabin zones through openings in the cabin floor behind the
sidewall panels. The FWD & AFT cargo compartments are ventilated by
means of an extraction fan or by differential pressure. Note that the
ventilation system is optional and independent for each compartment.
Controllers
The avionics equipment ventilation computer (A.E.V.C) ensures control and
monitoring of the avionics ventilation system.
The cargo ventilation controller controls and monitors the isolation valves and
the extraction fan of the cargo ventilation system.

GENERAL VENTILATION – SYSTEM DESIGN PHILOSOPHY

AVIONICS EQUIPMENT VENTILATION
Avionics Ventilation System Presentation
Avionics Equipment Ventilation Computer (AEVC) (10HQ)
The ventilation system is controlled and monitored by the avionics Equipment
Ventilation Computer. It continuously monitors system components. It
receives landing gear position, thrust lever position skin temperature and flow
information. It determines air supply route for avionics equipment cooling by
controlling valves and fans.
Skin Air Inlet Valve (15HQ)
The SKIN AIR INLET VALVE admits outside air into the ventilation circuit.
The SKIN AIR INLET valve is electrically controlled by the AEVC.
Blower Fan (20HQ)
The blower fan blows filtered fresh air to the avionics equipment. The fan
runs continuously.
Extract Fan (18HQ)
The extract fan extracts hot air from the avionics equipment. The extract fan
runs continuously.
Skin Air Outlet (Extract) Valve (22HQ)
The SKIN AIR OUTLET valve allows hot air evacuation outside the aircraft.
The valve is electrically controlled by the AEVC. On ground it is fully open.
During flight it is fully closed. If, at take-off thrust setting, the valve does not
close, the ground crew can manually close it. During flight and under certain
conditions, it can partially open.
Skin Exchanger Isolation Valve (24HQ)
The SKIN EXCHANGER ISOLATION valve connects or isolates the skin heat
exchanger depending on skin temperature. The SKIN EXCHANGER
ISOLATION valve is electrically controlled by the AEVC.
Skin Heat Exchanger
The air passing the SKIN HEAT EXCHANGER is cooled by contact with
aircraft skin. The SKIN HEAT EXCHANGER is used to cool air from the
avionics equipment when the SKIN EXCHANGER ISOLATION valve is-open.
Skin Exchanger Outlet Bypass Valve (23HQ)
The SKIN EXCHANGER OUTLET BYPASS valve is electrically controlled by
the AEVC. It allows avionics bay air to go into the system.
Air Conditioning Inlet Valve (21HQ)
The AIR CONDITIONING INLET valve is opened when the air conditioning
system is used as source of cold air. The valve is electrically controlled by
the AEVC. In failure cases, it allows cockpit supply air to go into the system
to insure cooling.
Skin Exchanger Inlet Bypass Valve (16HQ)
The SKIN EXCHANGER INLET BYPASS valve admits hot air under the
cargo compartment floor. The valve is electrically controlled by the AEVC. It
allows the ventilation air above the required quantity to be discharged to the
underfloor area.

AVIONICS VENTILATION SYSTEM PRESENTATION

VENTILATION PANEL

Aural warning sounds, MASTER CAUT, GEN 1 SMOKE (on the EMER ELEC
PWR panel), BLOWER and EXTRACT FAULT lights come on in case of
avionics smoke detection. VENT, INLET and EXTRACT words are displayed
amber on the ECAM page. Note that if smoke detection is confirmed, both
BLOWER and EXTRACT pushbuttons must be set to OVRD position.
AVIONICS SMOKE

Skin Air Inlet Valve
Single flap valve, 28 VDC controlled and operated. Can be manually
overridden. Before the valve is secured in a position, it must first be
electrically isolated with a toggle switch located on the valve.
SKIN AIR INLET VALVE DEACTIVATION

Skin Air Outlet Valve (Extract Valve)
Single flap valve with a smaller flap built into it. 28 VDC controlled and
operated. Can be manually overridden. Before the valve is secured in a
position, it must first be electrically isolated with a toggle switch located on
the valve. Internal flap opening is performed by turning handle in the closing
way well after the extract valve is closed, i.e. the main flap is flush with the
aircraft skin.
SKIN AIR OUTLET VALVE DEACTIVATION SWITCH

PRESSURIZATION CONTROL
General
In normal operation, pressurization control is fully automatic. The system
consists of:
- 2 Cabin Pressure Controllers (CPC).
- 1 outflow valve including 3 motors (2 for automatic operation, 1 for
manual operation).
- 1 Control panel.
- 2 Safety valves.
The outflow valve is powered by one of the three independent electrical
motors. Normally, one of the two cabin pressure controllers operates the
outflow valve, via its associated auto motor. A ditching switch on the control
panel, allows the outflow valve and all valves below the flotation line, to be
closed in case of ditching. The system can be used fully or semi
automatically or manually.
Automatic Operation
In fully automatic operation:
No action on the cabin pressure system is required. Cabin pressure is
achieved from external schedules when appropriate FMGS inputs are
available, in semi automatic operation:
Crew action only required to select the LDG FIELD ELEV.
Cabin press is achieved from internal schedules only.
There are 4 functions:
- Ground: Full opening of the outflow valves on ground.
- Prepressurization: During take off, pressure is increased, to avoid
cabin pressure surge during rotation.
- Pressurization "in flight": Cabin altitude and rate are adjusted to
ensure optimum passenger comfort.
- Depressurization: Following touch down, the residual cabin
overpressure is released progressively before the outflow valves are
fully opened in ground function.
Manual Operation
In manual mode, the pilot may control the cabin altitude, via the manual
motor of the outflow valves, by operating controls on the pressurization
control panel.
The Residual Pressure Control Unit ( RPCU )
Controls the residual pressure in the cabin and takes over the control of the
outflow valve automatically by providing power directly to the manual motor of
the outflow valve to open fully the valve.

FIGURE 1: SYSTEM INTRODUCTION

MAIN COMPONENTS AND SUBSYSTEMS
Cabin Pressure Controllers
Two identical, independent, automatic digital controllers are used for system
control. They receive signals from ADIRS, FMGC, EIU, LGCIU, zone
controller. In automatic pressure control mode one controller is active, the
other one is in standby. They also generate signals for ECAM. In manual
pressure control mode, the controller installed in No.1 position includes a
back up section with its own electrical power supply. This section contains a
pressure sensor in order to generate the excess cabin attitude and pressure
outputs for indications on ECAM. The controllers communicate via a cross
channel link.
Outflow Valve
The outflow valve is located on the right hand side of the fuselage, behind the
aft cargo compartment. The outflow valve assembly consists of a flush skin-
mounted rectangular frame, carrying inward and outward opening flaps linked
to the actuator. The actuator contains the drives of two auto motors and the
drive of the manual motor. The valve is operated by either of the two electric
motors when in automatic mode, or by the third electric motor when in
manual mode. In automatic mode, the valve position signal is transmitted to
the ECAM via the operating controller. In manual mode, the valve position
signal is transmitted via the back up section of controller No 1. When RAM
AIR P/B is set to ON and cabin AP is below 1 PSI, the outflow valve is driven
to 50° open position provided it is not under manual control.

Safety Valves
Two independent pneumatic safety valves avoid excessive positive (8.6 PSI)
or negative (-0.25 PSI) differential pressure. They are installed on the rear
pressure bulkhead, above the flotation line.
Automatic Pressure Control Mode
Pressure control is achieved by two identical, independent, automatic
systems (controller and its associated motors). Either system controls the
single outhow valve. Only one controller operates at a time. An automatic
transfer occurs:
- 180 sec. after each landing.
- In case of failure of the operating system.
The controller normally uses landing field elevation and ONH from FMGC
and pressure altitude from ADIRS. If FMGC data ere not available, the
controller uses captain barometer reference from ADIRS and landing
elevation from LDG ELEV selector. Pressurization is assumed through 6
modes:
1. Ground (GN)
Before take off and 55 sec after landing, the outflow valve is controlled fully
open to ensure there is no residual ∆P in the aircraft. At touchdown, to
release the remaining ∆P, a depressurized sequence controls the cabin V/S
at + 500 ft/min.
2. Take off (TO)
To avoid a pressure surge at rotation, the controller prepressurizes the
aircraft with a rate of - 500 ft/min until ∆P reaches 0.1 PSI. At lift off, the
controller initiates the climb phase.
3. Climb (CL)
Cabin altitude varies according to a fixed preprogrammed law taking into
account the actual rate of climb of the aircraft.
4. Cruise (CR)
Cabin altitude is the highest of the value reached at level off or the landing
field elevation.
5. Descent (DE)
Pressure rate is optimized so that cabin pressure reaches landing field
pressure just prior to landing. Maximum descent rate is limited to 750 ft/min.
6.
Abort (AB)
The abort mode is used to prevent the cabin altitude climbing if the aircraft
does not climb after take off. The cabin pressure is kept to the value before
take off.
Manual Pressure Control Mode
In the event of the failure of both automatic systems, the pressurization may
be manually controlled by selecting, on the CABIN PRESS control panel:
- MODE SEL P/B to MAN, and
- MAN V/S CTL switch to UP or DN.
Then, the power supplies to the auto motors are cut off, and the manual
motor is activated to control the outflow valve.
Ditching
A DITCHING P/B, on the CABIN PRESS control panel, enables the outflow
valve to be closed and sends a closure signal to:
the emergency ram air inlet, the avionics ventilation extract valve and the
pack flow control valves.

CABIN PRESSURIZATION SYSTEM - SCHEMATIC

CABIN PRESSURE PANEL

ECAM SYSTEM DISPLAY

ECAM DISPLAYS

OUTFLOW VALVE
General
The outflow valve 10HL is of the dual−gate type, designed to produce thrust
recovery. The valve is installed below the aircraft floation line, on the right−
hand side of the fuselage behind the aft cargo compartment.
The outflow valve has:
− two outflow valve electronic boxes,
− two automatic motors,
− a manual motor,
− a feedback module,
− an outflow valve body,
− a gearbox.
Only one motor is active at any one time. During this time the other motors
are locked.
Outflow Valve Electronic Boxes
The outflow−valve electronic boxes contains the electronic circuits which are
devided into the following sections:
− the data input section (RS422 receiver),
− the microcontroller and memory section,
− the motor drive section,
− the valve position feedback section (RVT position),
− the BITE circuits,
− the data output section (RS422 transmitter),
− the power supply module.
The box communicates with the CPC 11HL respectively 12HL via the RS422
bus.
A pressure switch is installed in each box. It operates independently from the
automatic operation. It closes the outflow valve if the pressure in the
fuselage is less than the atmospheric pressure at an altitude of 15000 ft.
(4571.91 m).
Automatic Motors
The automatic motors are DC brushless type with electromechanical
brake. They are used in automatic operation.
− Motor 1 - CPC 1
− Motor 2 - CPC 2
Manual Motor
The manual motor is a DC brush type.
− It is used in manual operation only when the toggle switch is used.
Feedback Module
The feedback module is a Rotary Variable Transformer (RVT). It sends
position data to the cabin pressure controllers 11HL and 12HL through the
outflow valve electronic boxes. Potentiometer sends position data to the
manual backup circuit of the cabin pressure controller 11HL.

SAFETY VALVE

ATA 21 AIR CONDITIONING FOR AIRBUS 320.pdf

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