21 AIR CONDITIONING

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SINGLE AISLE 
 TECHNICAL TRAINING MANUAL 
 MAINTENANCE COURSE - T1 (V2500-A5/ME) 
 AIR CONDITIONING 
This document must be used for training purposes only
Under no circumstances should this document be used as a reference
It will not be updated.
All rights reserved
No part of this manual may be reproduced in any form,
by photostat, microfilm, retrieval system, or any other means,
without the prior written permission of AIRBUS S.A.S.
AIR CONDITIONING
GENERAL
Air Conditioning Level 2 (2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
ZONE TEMPERATURE CONTROL (Classic)
System Presentation (1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Pack Presentation (1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
System Warnings (3) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Flow Control & Pack Components D/O (2) . . . . . . . . . . . . . . . . . . . . 30
Pack Sensors Description/Operation (3) . . . . . . . . . . . . . . . . . . . . . . 34
Cockpit & Cabin Components D/O (3) . . . . . . . . . . . . . . . . . . . . . . . 38
Zone Temperature Controller Interfaces (3) . . . . . . . . . . . . . . . . . . . . 40
Emergency Ram Air Inlet D/O (3) . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
ZONE TEMPERATURE CONTROL (Enhanced)
System Presentation (1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
Pack Presentation (1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
System Warnings (3) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
Flow Control & Pack Components D/O (2) . . . . . . . . . . . . . . . . . . . . 54
Pack Sensors Description/Operation (3) . . . . . . . . . . . . . . . . . . . . . . 58
Cockpit & Cabin Components D/O (3) . . . . . . . . . . . . . . . . . . . . . . . 60
Zone Temperature Controller Interfaces (3) . . . . . . . . . . . . . . . . . . . . 64
# Emergency Ram Air Inlet D/O (3) . . . . . . . . . . . . . . . . . . . . . . . . . 68
PRESSURIZATION
System Description/Operation (3) . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
System Warnings (3) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
System Control Interfaces (3) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
System Monitoring Interfaces (3) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78
Functional Test of MAN Motor of Outflow Valve (3) . . . . . . . . . . . . 80
GENERAL VENTILATION
System Design Presentation (1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90
AVIONICS VENTILATION
System Warnings (3) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92
System Description and Operation (3) . . . . . . . . . . . . . . . . . . . . . . . . 94
System Interfaces (3) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102
FORWARD CARGO COMPT VENTILATION/HEATING
(option)
System Controls Presentation (3) . . . . . . . . . . . . . . . . . . . . . . . . . . . 110
System Warnings (3) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112
AFT CARGO COMPT VENTILATION/HEATING (option)
System Controls Presentation (3) . . . . . . . . . . . . . . . . . . . . . . . . . . . 114
System Warnings (3) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116
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AIR CONDITIONING LEVEL 2 (2)
SYSTEM OVERVIEW
The air conditioning system main function is to keep the air in the
pressurized fuselage compartments at the correct pressure and
temperature. In details, this system provides the following functions:
- cabin temperature control,
- pressurization control,
- avionics ventilation,
- cargo compartment ventilation & heating (optional).
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SYSTEM OVERVIEW
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AIR CONDITIONING LEVEL 2 (2)
SYSTEM OVERVIEW (continued)
CABIN TEMPERATURE CONTROL
The Single Aisle family is equipped with two air conditioning packs
located in the wing root area forward of the landing gear bay. The
packs supply dry air to the cabin for air conditioning, ventilation and
pressurization. The main component of each pack assembly is the air
cycle machine.
Hot air from the pneumatic system is supplied to the pack through the
pack Flow Control Valve (FCV). The FCV adjusts the flow rate
through the pack and is the pack shut-off valve. During normal
operation, the Zone Controller (ZC) calculates the flow mass demand
and transmits the data to the Pack Controller (PC) which set the flow
control valve in the necessary reference position.
The pack temperature control system controls the pack outlet
temperature and sets its maximum and minimum limits. The system
includes two PCs. Each PC controls one pack. During normal
operation, the ZC sends the required pack outlet temperature to both
PCs. To control the pack outlet temperature, the PC modulates the
BYPASS VALVE and the RAM-AIR INLET doors.
On the Enhanced aircraft, the ZC and PCs are replaced by the Air
Conditioning System Controllers (ACSC). All of the functions of the
ZC and PCs are incorporated in the ACSC.
The packs supply the mixer unit. Three separate aircraft zones are
supplied from the mixer unit:
- cockpit,
- forward cabin,
- aft cabin.
Two cabin recirculation fans are installed to reduce the bleed air
demand and therefore save fuel. These fans establish a recirculation
flow of air from the cabin zones to the mixer unit. In normal operation,
there are no ECAM indications associated with the cabin fans.
The ZC controls and monitors the temperature regulation system for
the cabin zones. On the overhead AIR COND panel, the flight crew
selects the desired individual compartment temperature.
The hot air system for cabin temperature control has a trim air pressure
regulating valve and trim air valves controlled by the ZC.
For the zones, which require warmer temperature, the ZC signals the
TRIM VALVES to open. Hot air mixes with the pack discharge air
and the temperature increases.
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SYSTEM OVERVIEW - CABIN TEMPERATURE CONTROL
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AIR CONDITIONING LEVEL 2 (2)
SYSTEM OVERVIEW (continued)
PRESSURIZATION CONTROL
The pressurization system on the Single Aisle family normally operates
automatically to adjust the cabin altitude and rate of climb to ensure
maximum passenger comfort and safety. The pressurized areas are:
- the cockpit,
- the avionics bay,
- the cabin,
- the cargo compartments.
The concept of the system is simple. Air is supplied from the air
conditioning packs to the pressurized areas. An outflow valve is used
to regulate the amount of air allowed to escape from the pressurized
areas.
Automatic control of the outflow valve is provided by two Cabin
Pressure Controllers (CPCs). Each CPC controls one electric motor
on the outflow valve assembly. The CPCs interface with other aircraft
computers to optimize the pressurization / depressurization schedule.
There are two automatic pressurization systems. Each CPCand its
electric motor make up one system. Only one system operates at a
time with the other system acting as backup in case of a failure. The
system in command will alternate each flight.
A third motor is installed for manual operation of the outflow valve
in case both automatic systems fail.
To protect the fuselage against excessive cabin differential pressure,
safety valves are installed on the rear pressure bulkhead. The safety
valves also protect against negative differential pressure.
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SYSTEM OVERVIEW - PRESSURIZATION CONTROL
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AIR CONDITIONING LEVEL 2 (2)
SYSTEM OVERVIEW (continued)
AVIONICS VENTILATION
The avionics ventilation system supplements the air conditioning
system to supply cooling air to the avionics equipment. This equipment
includes the avionics compartment, the flight deck instruments and
the circuit breaker panels.
A blower fan and an extraction fan circulate the air through the
avionics equipment.
NOTE: Note: These fans operate continuously as long as the aircraft
electrical system is supplied.
The Avionics Equipment Ventilation Computer (AEVC) controls the
fans and the configuration of the skin valves in the avionics ventilation
system based on flight / ground logic and fuselage skin temperature.
There are 3 configurations for the skin air inlet and outlet valves:
- open circuit: both valves open (on ground only),
- closed circuit: both valves closed (flight or low temperature on
ground). The air is cooled in the SKIN HEAT EXCHANGER. The
skin heat exchanger is a chamber which allows the air to contact the
fuselage skin in flight,
- intermediate circuit: inlet closed, outlet partially open (smoke
removal in flight or low ventilation airflow condition).
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SYSTEM OVERVIEW - AVIONICS VENTILATION
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AIR CONDITIONING LEVEL 2 (2)
SYSTEM OVERVIEW (continued)
CARGO VENTILATION AND HEATING
As an option on the Airbus single aisle family, the forward and aft
cargo compartments can have a ventilation system. In addition, a
heating system may be installed in either or both compartments. Note
that the heating system will only be installed along with a ventilation
system.
The operation for both compartments is similar so we will only look
at the forward cargo compartment. Air from the main cabin is drawn
down into the cargo compartment by the extract fan or by differential
pressure in flight. After circulating through the compartment, the air
is discharged overboard.
The operation of the two isolation valves and the extract fan is
controlled automatically by the cargo Ventilation Controller (VC).
One VC is able to control either or both compartments.
For the heating of the cargo compartment, the pilots select the desired
compartment temp and hot bleed air is mixed with the air coming
from the main cabin to increase the temperature if necessary. The
supply of hot air is controlled by the Cargo Heating Controller. Each
heated compartment has a dedicated Cargo Heating Controller. Note
that there is NO direct air conditioning supply to the cargo
compartments. The pilots cannot add "cold" air to the compartments.
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SYSTEM OVERVIEW - CARGO VENTILATION AND HEATING
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AIR CONDITIONING LEVEL 2 (2)
MEL/DEACTIVATION
Per the Minimum Equipment List (MEL), the following deactivation
procedures may be performed to dispatch the aircraft with air conditioning
and ventilation problems.
PACK FLOW CONTROL VALVE
The aircraft may be dispatched per MEL with the pack Flow Control
Valve (FCV) failed. With the valve secured in the CLOSED position,
single pack operations are limited to 31,500 / 35,400 / 37,000 ft.
(depending on aircraft/engine combination).
Deactivation procedure:
- NO pneumatic supply to the air conditioning system,
- remove access panel on belly fairing,
- set pack pushbutton switch OFF,
- deactivate the FCV by removing the special screw (this allows the
valve to continually vent, spring tension closes the valve),
- With the valve in the CLOSED position, use the special screw to
secure the valve CLOSED.
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MEL/DEACTIVATION - PACK FLOW CONTROL VALVE
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AIR CONDITIONING LEVEL 2 (2)
MEL/DEACTIVATION (continued)
AVIONICS VENTILATION SKIN AIR OUTLET VALVE
In case of failure, the Skin Air Outlet Valve may be deactivated in
the PARTIAL-OPEN position for dispatch per the MEL. The
PARTIAL-OPEN position is when the main flap of the valve is closed
and the auxiliary flap is OPEN. This will allow for smoke removal in
case of avionics smoke in flight. The valve is equipped with a handle
which is used to crank the valve open or closed. When the outlet valve
is deactivated PARTIAL-OPEN, the Skin Exchanger Isolation Valve
is deactivated OPEN.
The Skin Exchanger Isolation Valve is located in the avionics
compartment. The valve is equipped with a manual lever/position
indicator which may be used to put the valve in the OPEN position.
Procedure:
- push latch to release the handle from the valve,
- pull the handle to engage the splines,
- set the Deactivation switch to OFF,
- turn the handle clockwise until the main flap is closed and the
auxiliary flap is OPEN,
- stow and latch the handle,
- move the Skin Exchanger Isolation Valve to the OPEN position and
remove the connector to deactivate,
- perform AEVC BITE.
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MEL/DEACTIVATION - AVIONICS VENTILATION SKIN AIR OUTLET VALVE
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AIR CONDITIONING LEVEL 2 (2)
MEL/DEACTIVATION (continued)
AVIONICS VENTILATION SKIN AIR INLET VALVE
In case of failure, the Skin Air Inlet Valve may be deactivated in the
CLOSED position for dispatch per the MEL. The valve is equipped
with a handle which is used to crank the valve open or closed. When
the inlet valve is deactivated CLOSED, the Conditioned Air Inlet
valve is deactivated OPEN. This allows supplemental cooling from
the cockpit air conditioning supply for the avionics equipment when
the normal supply is affected.
The conditioned air inletvalve is located in the avionics compartment.
The valve is equipped with a manual lever/position indicator which
may be used to put the valve in the OPEN position.
Deactivation procedure:
- push latch to release the handle from the valve,
- pull the handle to engage the splines,
- set the Deactivation switch to OFF,
- turn the handle counter-clockwise until the flap is closed,
- stow and latch the handle,
- move the Conditioned Air Inlet Valve to the OPEN position and
remove the connector to deactivate,
- perform AEVC BITE.
AVIONICS VENTILATION CONDITIONED AIR INLET
VALVE
In addition to the Skin Air Inlet Valve deactivation, other ventilation
system deactivation tasks also include deactivation of the Conditioned
Air Inlet Valve in the OPEN position. These affected components are:
- the blower fan,
- the extract fan,
- the ventilation filter.
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MEL/DEACTIVATION - AVIONICS VENTILATION SKIN AIR INLET VALVE & AVIONICS VENTILATION CONDITIONED AIR INLET
VALVE
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AIR CONDITIONING LEVEL 2 (2)
MAINTENANCE TIPS
When the aircraft is on the ground with the electrical systems powered,
the avionics ventilation system is normally in the OPEN configuration.
In this configuration, the ventilation BLOWER fan pulls air in from the
open Skin Air Inlet Valve on the LH side of the fuselage. The air is
circulated through the ventilation system and then the EXTRACTION
fan discharges the air overboard through the open Skin Air Outlet Valve.
If maintenance is being performed on the aircraft in heavy rain conditions
with the ventilation system in the OPEN configuration, the blower fan
may draw water into the ventilation system and subsequently, into the
aircraft computers. To prevent water ingestion, the ventilation system
should be put in the CLOSED configuration by selecting the EXTRACT
pushbutton to OverRriDe (OVRD) on the VENTILATION panel. For
additional cooling in the CLOSED configuration, select the packs ON.
If the Skin Air INLET or OUTLET valve fails on the ground and no
replacement part is available, either valve may be manually operated to
the OPEN position. This will allow cooling for the avionics equipment
if the aircraft is powered for maintenance operations. Before flight, the
failed valve must be deactivated in the proper configuration.
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MAINTENANCE TIPS
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SYSTEM PRESENTATION (1)
BASIC PRINCIPLE
Hot air coming from the air bleed system is flow regulated before entering
the packs in order to be temperature regulated. Hot air pressure is
maintained above the cabin pressure allowing the hot airflow to join the
pack air supply when necessary. A part of cabin air is recirculated to
decrease air supply demand.
NOTE: Note: The lavatories and galleys are ventilated with air coming
from zones and main distribution ducts.
PACK UNITS
The airflow from the air bleed system is regulated by two pack Flow
Control Valves (FCVs). Then two independent packs supply regulated
temperature air to the mixer unit. Both packs supply air at the same
temperature.
MIXER UNIT
The mixer unit mixes temperature-regulated air from the packs with part
of the cabin air supplied by recirculated fans. The mixer unit may also
receive conditioned air from a LP ground connection or fresh outside air
from the emergency ram air inlet. The emergency ram air inlet supplies
outside fresh air for ventilation of the A/C in emergency conditions when
there is loss of both packs or smoke removal.
TRIM AIR PRV
Hot air tapped upstream of the packs supplies the trim air valves through
a trim air Pressure Regulating Valve (PRV). This valve regulates the
downstream pressure above the cabin pressure.
HOT TRIM AIR
A trim air valve associated with each zone optimizes the temperature by
adding hot air, if necessary, to the cold air coming from the mixer unit.
AIR DISTRIBUTION
The conditioned air is distributed to three main zones:
- cockpit,
- FWD cabin,
- aft cabin.
Normally the mixer unit lets the cockpit be supplied from pack 1 and
FWD and aft cabins from pack 2.
LAV AND GALY VENTILATION
The LAVatory and GALleY ventilation system uses air from the cabin
zones. A fan extracts this air through the outflow valve.
NOTE: Note: The LAV and GALY extract air is also used to ventilate
the cabin zone temperature sensors.
TEMPERATURE REGULATION
The pack outlet temperature regulation is automatic and controlled by
the related Pack Controller (PC) which in turn is controlled by the Zone
Controller (ZC). This optimizes the temperature regulation. Each zone
and PC has one primary channel and one electrically independent
secondary channel respectively called primary and secondary computers.
The secondary computer acts as a back-up in case of failure of the primary
computer.
PC
Each PC gives:
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- a basic temperature regulation of its associated pack in accordance with
the demand from the ZC,
- flow control and monitoring of its associated pack in accordance with
the flow control demand from the ZC.
ZC
The ZC generates signals to the PC for basic temperature regulation and
flow control optimization. It optimizes the temperature regulation by
means of trim air valves to obtain the selected ambient temperature in
the related zone. The lowest zone temperature demand is used by the ZC
for basic temperature regulation to achieve the required outlet temperature
of both packs.
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BASIC PRINCIPLE ... ZC
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PACK PRESENTATION (1)
PACK FCV
Each pack Flow Control Valve (FCV) is pneumatically operated and
electrically controlled. The flow regulation is achieved by a torque motor
under Pack Controller (PC) control. In case of pack compressor overheat
to 230°C (446°F), the pack FCV starts to close pneumatically.
NOTE: Note: Part of the hot air, downstream of the pack FCV is sent
to the trim air Pressure Regulating Valve (PRV). Each pack
FCV is automatically closed during either a same side engine
start sequence or an opposite side engine start sequence
provided the crossbleed valve is detected open. It reopens 30
seconds after the end of any engine start sequence.
EXCHANGERS-COMPRESSOR
Bleed air is ducted to the primary heat exchanger, then to the compressor.
The air is cooled in the main heat exchanger. Then it passes through the
reheater, the condenser and the water extractor in order to remove water
particlesfrom the turbine air.
TURBINE
The air expands in the turbine section which results in a very low turbine
discharge air temperature. The turbine drives the compressor and the
cooling air fan.
A.ICE VALVE
The PC controls the Anti-ICE (A.ICE) valve to pneumatically open in
order to stop ice formation across the pack condenser. In case of complete
PC failure, the A.ICE valve is signalled to pneumatically control the pack
outlet temperature to 15°C (59°F).
RAM AIR INLET FLAP AND BYP VALVE
The BYPass valve and the ram air inlet flap are simultaneously controlled
by the PC. The BYP valve is electrically controlled to modulate the pack
discharge temperature by adding hot air. The ram air inlet flap modulates
the airflow through the exchangers. To increase cooling, the ram air inlet
flap opens more and the BYP valve closes more and to increase heating,
the ram air inlet flap closes more and the BYP valve opens more. During
take-off and landing, the ram air inlet flap is fully closed to prevent
ingestion of foreign objects.
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PACK FCV ... RAM AIR INLET FLAP AND BYP VALVE
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PACK PRESENTATION (1) May 10, 2006
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SYSTEM WARNINGS (3)
PACK 1 (2) OVHT
In case of PACK 1 (2) OVerHeaT, the MASTER CAUTion comes on
and the aural warning sounds. The PACK FAULT light on the control
panel comes on. It goes off when the overheat disappears. The failure is
shown amber on the EWD associated to indications on the ECAM BLEED
page. The pack Flow Control Valve (FCV) should start to close
pneumatically when the temperature is above 230°C and should be fully
closed above 260°C. It will reopen when the overheat disappears. The
FAULT light comes on if:
- the compressor outlet temperature is four times above 230°C or once
above 260°C,
- the pack outlet temperature is above 95°C.
In this case, the valve must be closed by setting its control to OFF.
PACK 1 (2) FAULT
In case of PACK 1 (2) FAULT, the MASTER CAUTion comes on, the
aural warning sounds and the PACK FAULT light on the control panel
comes on. The failure is shown amber on the EWD associated to
indications on the ECAM BLEED page. When the pack valve position
disagrees with its command signal, or when the pack compressor outlet
temperature exceeds 230°C four times during one flight, the FAULT
light on the pack control P/B comes on.
PACK 1 (2) OFF
In case of PACK 1 (2) OFF, the MASTER CAUTion and the aural
warning sounds come on. The failure is shown amber on the EWD
associated to indications on the ECAM BLEED page.
NOTE: Note: This warning comes on when one pack is selected OFF
with no failure.
PACK 1 (2) REGUL FAULT
In case of a PACK 1 (2) REGULation FAULT, the corresponding message
appears amber on the EWD associated to indications on the ECAM
BLEED page. In case of pack controller primary computer failure, the
pack flow remains at the previous setting. When primary and secondary
computers fail, the pack outlet temperature is pneumatically controlled
by the anti-ice valve to 15°C.
PACK 1 + 2 FAULT
In case of a PACK 1+2 FAULT, the MASTER CAUTion comes on, the
aural warning sounds and the PACK FAULT light on the control panel
comes on. The failure is shown amber on the EWD associated to
indications on the ECAM BLEED page.
NOTE: Note: Pack 2 is already OFF due to a previous failure.
CKPT, FWD CABIN OR AFT CABIN DUCT OVHT
In case of CocKPiT, ForWarD CABin or AFT CABin DUCT OVerHeaT,
the MASTER CAUTion comes on, the aural warning sounds and the
HOT AIR fault light comes on, on the control panel. The failure is shown
amber on the EWD associated to indications on the ECAM COND page.
Any zone duct temperature higher than 88°C causes the hot air Pressure
Regulating Valve (PRV) and trim air valves to close electrically. The
FAULT light on the HOT AIR P/B goes off when it is set to OFF and
the temperature is back below 70°C.
NOTE: Note: The cargo ventilation and heating systems are optional
and independent for each compartment.
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HOT AIR FAULT
In case of HOT AIR FAULT, the MASTER CAUTion comes on, the
aural warning sounds and the HOT AIR fault light comes on, on the
control panel. The failure is shown amber on the EWD associated to
indications on the ECAM COND page. The warning occurs when the
HOT AIR PRV position disagrees with the selected position (e.g. reset
by HOT AIR P/B before cool down of duct temperature below 70°C).
TRIM AIR SYSTEM FAULT (TRIM AIR VALVE FAULT)
In case of a TRIM AIR SYStem FAULT, the corresponding message
appears amber on the EWD. This message is activated when a trim air
valve motor is stuck. In this case, the trim air system is completely lost,
and each pack is controlled separately, pack 1 for the cockpit and pack
2 for the cabin to maintain 24°C.
ZONE REGUL FAULT
In case of ZONE REGULation FAULT (loss of Zone Controller (ZC)),
the corresponding message appears on the EWD associated to indications
on the ECAM COND page. In case of primary computer failure, the
message on the COND page is in ALTN MODE and zone temperatures
are controlled to 24°C. In case of primary and secondary computer failure,
the HOT AIR and trim air valves close and packs deliver a fixed
temperature PACK REGulated which is 20°C for pack 1 and 10°C for
pack 2.
NOTE: Note: The cargo ventilation and heating systems are optional
and independent for each compartment.
L+R CAB FAN FAULT
In case of a L+R CABin FAN FAULT the MASTER CAUTion comes
on, the aural warning sounds and the failure is shown amber on the EWD
associated to indications on the ECAM COND page. This failure does
not downgrade the temperature regulation.
LAV+GALLEY FAN FAULT
In case of LAVatory+GALLEY FAN FAULT, the corresponding message
appears amber on the EWD. Cabin zone temperature sensors are normally
ventilated by the lavatory and galley fan. Therefore cabin zone
temperature regulation is lost when a fan failure occurs. Cabin duct
temperature is fixed at 15°C. Cockpit temperature regulation is normal
(cockpit temperature sensor is ventilated by avionics ventilation system).
NOTE: Note: The cargo ventilation and heating systems are optional
and independent for each compartment.
TRIM AIR SYS FAULT (TRIM AIR SYSTEM
OVERPRESSURE)
In case of a TRIM AIR SYStem FAULT, the corresponding message
appears amber on the EWD. This message will be activated if the
downstream pressure of the HOT AIR PRV is greater than 6.5 psi above
the cabin pressure. It disappears as soon as it drops below 5 psi above
the cabin pressure.
NOTE: Note: The cargo ventilation and heating systems are optional
and independent for each compartment.
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PACK 1 (2) OVHT ... TRIM AIR SYS FAULT (TRIM AIR SYSTEM OVERPRESSURE)
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FLOW CONTROL & PACK COMPONENTS D/O (2)
OZONE FILTER (OPTION)
An ozone filter is installed upstream of each Flow Control Valve (FCV).
It is used for catalyticremoval of ozone from the hot bleed air supplied
to the pack.
DELTA P SENSOR AND FCV
A Differential Pressure (DELTA P) sensor connected to the FCV senses
a differential pressure equivalent to the airflow through the valve inlet.
This differential pressure is transformed into an electrical signal and sent
to the Pack Controller (PC) for actual flow calculation. According to the
actual flow calculation and the flow demand, the PC generates an FCV
drive signal in order to control the FCV Torque Motor (TM). The valve
butterfly is thus electro-pneumatically operated.
The FCV has a shut-off solenoid, which is energized in case of:
- engine start,
- opposite engine start, if the Crossbleed (X BLEED) valve is detected
open, the FCV reopens 30 seconds after the end of the engine start
sequence,
- ENG FIRE P/B released out,
- DITCHING P/B pressed in,
- applicable PACK P/B set to OFF.
The FCV also automatically closes in case of:
- low bleed pressure: valve spring-loaded closed,
- compressor overheat: muscle pressure venting by means of the
compressor pneumatic overheat sensor.
BY-PASS VALVE
The BYPass valve regulates the pack discharge temperature by adding
hot bleed air to the air cycle machine outlet for quick pack response. The
BYP valve is electrically operated by a stepper motor controlled by the
PC according to the water extractor temperature.
RAM AIR INLET FLAP
The ram air inlet flap modulates the airflow through the exchangers to
control the temperature of the pack outlet. The PC controls an electric
actuator that actuates the ram air inlet flap, according to the water
extractor temperature in order to obtain optimum pack cooling airflow.
The ram air inlet flap closes during take-off and landing to avoid ingestion
of foreign material.
A.ICE VALVE
The Anti-ICE (A.ICE) valve removes any excessive ice formation across
the condenser or maintains the pack outlet temperature at a fixed value,
if the PC is unable to control the BYP valve. The A.ICE valve is
pneumatically operated and electrically controlled by a solenoid:
- solenoid energized: the A.ICE valve pneumatically operates as an
anti-ice function,
- solenoid de-energized: the A.ICE valve pneumatically operates as a
temperature control valve. It maintains a pack outlet temperature of 15°C
(59°F).
An additional 3/2 way valve solenoid connected in parallel to the solenoid
of A.ICE in order to resolve the back-up problem.
In normal mode:
- the solenoid is energized,
- the pipe assembly is open.
In back-up mode:
- the solenoid is de-energized,
- the pipe assembly is closed.
The anti-ice function is done by two DELTA P relays for high and low
pressure condenser flows. When the DELTA P increases due to restricted
airflow caused by ice build-up, the related relays control the A.ICE valve
to an open position. The pack outlet pneumatic sensor is used only to
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modulate the A.ICE valve to control the pack discharge temperature at
a fixed value if there is PC failure.
AIR CYCLE MACHINE
The air cycle machine, which has a turbine, a compressor and a fan, cools
the air. The main component of the air cycle machine is a rotating shaft.
A turbine, a compressor and a fan are mounted along the shaft.
EXCHANGERS - REHEATER - CONDENSER
The air passes through two heat exchangers and a reheater before it enters
the condenser, which causes the air temperature to drop well below dew
point. The cooling agent for the primary heat exchanger and the main
heat exchanger is outside ram air. The reheater is used to raise the
temperature of the air before it reaches the turbine inlet to vaporize any
remaining water droplets for turbine protection.
WATER EXTRACTOR
The water extractor collects water droplets and drains them inside the
water extractor body in order to spray the collected water into the ram
airflow of the exchangers, to increase the cooling efficiency.
CHECK VALVE
The pack downstream check valve stops leakage of air from the
distribution system when the FCV is closed. The check valve is fitted to
the pressure bulkhead.
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OZONE FILTER (OPTION) ... CHECK VALVE
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PACK SENSORS DESCRIPTION/OPERATION (3)
PACK INLET PRESSURE SENSOR
The pack inlet pressure sensor signals a pack inlet pressure drop to the
primary computer of the Pack Controller (PC). It is used to determine
the appropriate BYPass valve position. When the pack inlet pressure is
low, the BYP valve is controlled to a more open position in order to
decrease the Differential Pressure (DELTA P) of the air conditioning
pack. At the same time, the ram air inlet flap is controlled to a more open
position to compensate for the decreased efficiency of the
turbine/compressor cycle. Also, when engines are idle, if the cooling
demand cannot be satisfied, the engine idle setting can be changed by a
thrust demand. The Zone Controller (ZC) sends this thrust demand to the
Engine Interface Units (EIUs) depending on the bleed air pressure detected
by the sensor.
DELTA P SENSOR
A DELTA P sensor measures a differential pressure at the Flow Control
Valve (FCV) inlet. This DELTA P, which is equivalent to the airflow,
is converted into an electrical signal and sent to the secondary computer
of the PC. It is used for ECAM display and FCV control.
COMPRESSOR DISCHARGE TEMPERATURE SENSOR
The compressor temperature sensor signals the compressor outlet
temperature to the primary computer of the PC for pack temperature
control and overheat detection. Pack temperature controls:
- up to 180°C (385°F): normal operation,
- 180°C to 220°C (428°F): the RAM air inlet flap opens more in order
to increase the RAM airflow.
The pack FAULT light comes on if there is a pack overheat of 260°C
(500°F), or if 230°C (446°F) is detected four times during one flight.
COMPRESSOR PNEUMATIC OVERHEAT SENSOR
If there is overheat, the compressor pneumatic overheat sensor causes
venting of the FCV muscle pressure to close the valve. If there is
compressor outlet overheat, the FCV starts to close at 230°C (446°F) in
order to avoid reaching 260°C (500°F).
NOTE: 260°C is the temperature threshold for warning activation.
COMPRESSOR OVERHEAT SENSOR
The compressor overheat sensor signals the compressor outlet temperature
to the secondary computer of the PC for overheat detection and indication
on the ECAM display. The pack FAULT light comes on if there is pack
overheat of 260°C (500°F), or if 230°C (446°F) is detected four times
during one flight.
WATER EXTRACTOR TEMPERATURE SENSOR
The water extractor temperature sensor signals the water extractor
temperature for the pack outlet temperature control. The water extractor
temperature sensor has two thermistors, one connected to the primary
computer, the other to the secondary computer. They are used to modulate
the pack outlet temperature.
PACK OUTLET PNEUMATIC SENSOR
The pack outlet pneumatic sensor adjusts the Anti ICE (A.ICE) valve
muscle pressure to maintain the pack outlet temperature at a fixed value
when the control of the BYP valve is lost. The pack outlet pneumatic
sensor pneumatically controls the A.ICE valve to maintain the pack outlet
temperatureat approximately 15°C (59°F).
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PACK OUTLET TEMPERATURE SENSOR
The pack outlet temperature sensor signals the pack outlet temperature
to the secondary computer of the PC for ECAM display. The pack outlet
temperature sensor also gives pack overheat warning indications if the
pack outlet temperature exceeds 95°C (203°F).
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PACK INLET PRESSURE SENSOR ... PACK OUTLET TEMPERATURE SENSOR
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COCKPIT & CABIN COMPONENTS D/O (3)
MIXER UNIT
The mixer unit mixes air from packs and re-circulated air from the cabin
prior to distribution to each zone. The mixer unit, installed under the
cabin floor, uses cabin air, which has entered the underfloor area and has
been drawn through recirculation 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 TEMPERATURE 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 (ZC). Each mixer unit temperature sensor has two
thermistors, one connected to the primary computer and the other to the
secondary computer.
MIXER UNIT FLAP
The mixer unit flap supplies sufficient air to the flight deck if pack 1 P/B
is selected off. An electrically operated mixer unit flap is installed to
make sure that sufficient fresh air is delivered to the cockpit in case of
pack 1 failure.
TRIM AIR PRV
The trim air Pressure Regulating Valve (PRV) is pneumatically operated
and electrically controlled by a solenoid. The solenoid controls the
ON/OFF function. A limit switch indicates the CLOSED/NOT CLOSED
position to the ZC and the ECAM system. The trim air PRV regulates
the pressure of the air supplied to the trim air valves to 4 psi above the
cabin pressure. The ON/OFF function solenoid de-energizes when the
HOT AIR P/B is set to OFF or when any duct temperature is above 88°C
(190°F). This closes the valve.
HOT AIR PRESSURE SWITCH
Due to a malfunction of the trim air PRV, the hot air pressure switch
signals overpressure to the secondary computer of the ZC for ECAM
display and the Centralized Fault Display System (CFDS). If pressure in
the system exceeds 6.5 psi above the cabin pressure, the ZC activates the
ECAM system. This signal stays until the pressure falls below 5 psi.
TRIM AIR VALVES
The trim air valves allow the zone temperature to be adjusted by
modulating the hot airflow added to air from the mixer unit. The trim air
valves close when the trim air PRV closes. The butterfly of the trim air
valves is controlled by a stepper motor. The trim air valve position
determination is based on the step counting principle.
DUCT TEMPERATURE SENSORS
Each duct temperature sensor detects duct temperature for the
corresponding zone temperature control, indication and overheat detection
to the ZC. Each duct temperature sensor consists of two thermistors, one
connected to the primary computer and the other to the secondary
computer. Each thermistor gives control, indication and overheat detection
(starting at 80°C (176°F) with an amber ECAM duct temperature
indication).
ZONE TEMPERATURE SENSORS
Each zone sensor detects the related zone temperature for zone
temperature control and indication on the ECAM display. Each zone
temperature sensor has two thermistors, one connected to the primary
computer and the other to the secondary computer.
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MIXER UNIT ... ZONE TEMPERATURE SENSORS
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ZONE TEMPERATURE CONTROLLER INTERFACES (3)
GENERAL
The Primary and secondary channel of the Zone Controller (ZC) cross
talk via an internal bus. The primary and secondary channel of the Pack
Controller (PC) are cross talking via the RS232 connection.
SDAC
System data information is transmitted to the System Data Acquisition
Concentrator (SDAC) via ARINC buses for system monitoring. The
system data information is used for warning and display. These data are
temperature, valve position and other.
EIU
The ZC provides data to both Engine Interface Units (EIUs). Each EIU
provides one discrete to the ZC and one discrete to the corresponding
PC. EIU 1and 2 send to the PC: the take-off thrust is used for pack ram
air inlet closure. EIU 1 and 2 send to the ZC: the HP fuel valve position
is used for bleed demand circulation. The ZC sends to EIU 1 and 2:
- the engine power increase is used for bleed airflow increase,
- the bleed and the Anti ICE (A.ICE) status are used for thrust limit
calculation.
ADIRU 1
Air Data/Inertial Reference Unit (ADIRU) 1 sends data to the ZC for
zone and pack temperature control. The A/C altitude is used for zone
temperature compensation and pack water extractor outlet temperature
limitation.
ECB
The ZC sends data to the Electronic Control Box (ECB) and receives an
APU bleed valve open discrete. The ZC sends to the ECB: the increase
of APU flow is used for increased bleed airflow. The ECB sends to the
ZC: the APU bleed valve open is used for flow demand calculation.
DMU
The ZCs and PCs send system main status data to the Data Management
Unit (DMU) for maintenance monitoring purposes. The ZC sends to the
DMU: trim-air Pressure Regulating Valve (PRV) position. The PCs send
to the DMU: pack flow, water extractor and pack compressor discharge
temperatures, BYPass (BYP) valve and ram air inlet flap positions.
CFDIU
The ZC sends BITE data to the Centralized Fault Display Interface Unit
(CFDIU) for system monitoring. The BITE data is used for temperature
control system monitoring.
ZONE AND PACK CONTROLLERS
The PCs mainly receive temperature demand, flow demand and CFDIU
control signals from the ZC and send back maintenance data signals.
The ZC sends to the PCs:
- the temperature demand, the ZC status and the pack ARINC reception
status are used for pack temperature control,
- the flow demand is used for flow control,
- the BITE command for CFDIU.
The PCs send to the ZC: the pack control status, the zone ARINC
reception status and the BITE information are used for temperature control
system monitoring.
FAN PARAMETERS
The ZC receives discrete signals from recirculation and toilet fans for
monitoring. The recirculation, toilet and galley and aft cargo ventilation
fan operation is used for monitoring for transmission to the SDACs and
CFDIU.
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A.ICE AND PNEUMATIC PARAMETERS
A.ICE and pneumatic parameters are used to detect faults and to ascertainthe status of the bleed air system for transmission to the CFDIU and EIUs.
The valve positions, low and high pressure are used for A.ICE system
fault detection for the CFDIU and thrust limit calculation for the EIUs.
LGCIU 2
Landing Gear Control and Interface Unit (LGCIU) 2 sends a ground/flight
signal to both PCs for pack ram air inlet flap operation. The ground/flight
signal is used for pack ram air inlet flap closure during take-off and
landing phases.
BSCU
The Braking and Steering Control Unit (BSCU) sends a wheel signal to
both PCs for pack ram air inlet flap operation. The wheel speed is used
for pack ram air inlet flap closure during take-off and landing phases.
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EMERGENCY RAM AIR INLET D/O (3)
GENERAL
The A/C has one emergency ram air inlet flap located at the lower LH
side of the fuselage, sharing the same duct with the LP ground connection.
EMERGENCY RAM AIR INLET FLAP OPERATION
In case of failure of both packs, an emergency ram air inlet flap can be
opened for A/C ventilation or smoke removal. In case of smoke removal
or loss of both packs, the RAM AIR P/B must be set to ON. When set to
ON, and if DITCHING is not selected, the emergency ram air inlet flap
opens. The flap, installed between the LP GND connection and ram air
inlet, closes one side of the duct when air is supplied from the other side.
The check valve stays closed. The A/C must descend to less than 10000
ft. When the cabin ambient air differential pressure is less than 1 psi, the
pressure controller half opens the outflow valve. The air then goes through
the check valve to the mixing unit.
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GENERAL & EMERGENCY RAM AIR INLET FLAP OPERATION
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SYSTEM PRESENTATION (1)
BASIC PRINCIPLE
The flow of hot air from the air bleed system is regulated before it enters
the packs in order to be temperature regulated. Hot air pressure is
maintained above the cabin pressure, which lets the hot airflow join the
pack air supply when necessary. Part of the cabin air is recirculated to
decrease air supply demand.
NOTE: Note: The lavatories and galleys are ventilated to decrease air
supply demand.
PACK UNITS
The airflow from the air bleed system is regulated by two pack Flow
Control Valves (FCVs). Two independent packs then supply air with a
regulated temperature to the mixer unit. Both packs supply air at the same
temperature.
MIXER UNIT
The mixer unit mixes air with a regulated temperature from the packs
with part of the cabin air supplied by the recirculation fans. The mixer
unit can also receive conditioned air from an LP ground connection or
fresh outside air from the emergency ram air inlet. The emergency ram
air inlet supplies outside fresh air for ventilation of the A/C in emergency
conditions when there is loss of both packs or smoke removal.
TRIM AIR PRV
Hot air tapped upstream of the packs supplies the trim air valves through
a trim air Pressure Regulating Valve (PRV). This valve regulates the
downstream pressure 4 psi above the cabin pressure.
HOT TRIM AIR
A trim air valve associated with each zone optimizes the temperature by
adding hot air, if necessary, to the air from the mixer unit.
AIR DISTRIBUTION
The conditioned air is distributed to three main zones:
- cockpit,
- forward cabin,
- aft cabin.
Normally, the mixer unit lets the cockpit be supplied from pack 1 and
FWD and aft cabins from pack 2.
LAV AND GALY VENTILATION
The LAVatory and GALleY ventilation system uses air from the cabin
zones. A fan extracts this air through the outflow valve.
NOTE: Note: The LAV and GALY ventilation system is also used to
ventilate the cabin zone temperature sensors.
ACSC
The Air Conditioning System Controller (ACSC) does:
- temperature regulation in accordance with demand,
- flow control and monitoring in accordance with flow control demand.
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PACK PRESENTATION (1)
PACK FCV
Each pack Flow Control Valve (FCV) is pneumatically actuated and
electrically controlled. The flow regulation is done by a torque motor
under the control of the air conditioning system controller. If the pack
compressor outlet temperature is > 215°C (419°F), the FCV starts to
reduce the flow. A compressor outlet temperature > 260°C (500°F) results
in a pack overheat warning.
NOTE: Note: Part of the hot air, downstream of the pack FCV, is sent
to the trim air Pressure Regulating Valve (PRV).
Each pack FCV is automatically closed during either a same
side engine start sequence or an opposite side engine start
sequence, if the crossbleed valve is detected open. It reopens
30 seconds after the end of any engine start sequence.
EXCHANGERS - COMPRESSOR
Bleed air is ducted to the primary heat exchanger, then to the compressor.
The air is cooled in the main heat exchanger. It then goes through the
reheater, the condenser and the water extractor in order to remove water
particles from the air entering the turbine.
TURBINE
The air expands in the turbine section, which results in a very low turbine
discharge air temperature. The turbine drives the compressor and the
cooling air fan.
A.ICE VALVE
The air conditioning system controller controls the Anti-ICE (A.ICE)
valve to electrically open in order to stop ice formation across the pack
condenser. Once the pressures are within a certain limit, the A.ICE valve
closes again.
RAM AIR INLET FLAP AND BYP VALVE
The BYPass valve and the ram air inlet flap are simultaneously controlled
by the air conditioning system controller. The BYP valve is operated by
an electro-mechanical actuator to modulate the pack discharge temperature
by adding hot air. The ram air inlet flap modulates the airflow through
the exchangers. To increase cooling, the ram air inlet flap opens more
and the BYP valve closes more. To increase heating, the ram air inlet
flap closes more and the BYP valve opens more. During take-off and
landing, the ram air inlet flap is closed to prevent ingestion of foreign
objects.
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PACK FCV ... RAM AIR INLET FLAP AND BYP VALVE
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SYSTEM WARNINGS (3)PACK 1 (2) OVHT
In case of PACK 1 (2) OVerHeaT, the MASTER CAUTion comes on
and the aural warning sounds. The PACK FAULT light on the control
panel comes on. It goes off when the overheat disappears. The failure is
shown amber on the EWD associated to indications on the ECAM BLEED
page. The FAULT light comes on if:
- the compressor discharge temperature is 230°C for four times during
one flight,
- a compressor temperature of more than 260°C has occurred or,
- the pack outlet temperature is above 95°C.
On ground, the Air Conditioning System Controller (ACSC) will close
the Flow Control Valve (FCV) automatically. In flight the cockpit crew
needs to switch off the pack manually with the PACK P/BSW.
PACK 1 (2) FAULT
In case of PACK 1 (2) FAULT, the MASTER CAUTion comes on, the
aural warning sounds and the PACK FAULT light on the control panel
comes on. The failure is shown amber on the EWD associated to
indications on the ECAM BLEED page. When the pack valve position
disagrees with the selected position or the pack valve is closed, the
FAULT light on the pack control P/B comes on.
PACK 1 (2) OFF
In case of PACK 1 (2) OFF, the MASTER CAUTion and the aural
warning sounds come on. The failure is shown amber on the EWD
associated to indications on the ECAM BLEED page.
NOTE: Note: This warning comes on when one pack is selected OFF
with no failure.
PACK 1 (2) REGUL FAULT
In case of a PACK 1 (2) REGULation FAULT, the corresponding message
appears amber on the EWD associated to indications on the ECAM
BLEED page. The FAULT is displayed when there is a failure of the
bypass valve, or the RAM air inlet actuator, or the compressor discharge
temperature sensor, or the flow control valve.
PACK 1 + 2 FAULT
In case of a PACK 1+2 FAULT, the MASTER CAUTion comes on, the
aural warning sounds and the PACK FAULT light on the control panel
comes on. The failure is shown amber on the EWD associated to
indications on the ECAM BLEED page.
NOTE: Note: Pack 2 is already OFF due to a previous failure.
CKPT, FWD CABIN OR AFT CABIN DUCT OVHT
In case of CocKPiT, ForWarD CABin or AFT CABin DUCT OVerHeaT,
the MASTER CAUTion comes on, the aural warning sounds and the
HOT AIR fault light comes on, on the control panel. The failure is shown
amber on the EWD associated to indications on the ECAM COND page.
Any zone duct temperature higher than 88°C causes the hot air Pressure
Regulating Valve (PRV) and trim air valves to close electrically. The
FAULT light on the HOT AIR P/B goes off when it is set to OFF and
the temperature is back below 70°C.
NOTE: Note: The cargo ventilation and heating systems are optional
and independent for each compartment.
HOT AIR FAULT
In case of HOT AIR FAULT, the MASTER CAUTion comes on, the
aural warning sounds and the HOT AIR fault light comes on, on the
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control panel. The failure is shown amber on the EWD associated to
indications on the ECAM COND page. The warning occurs when the
HOT AIR PRV position disagrees with the selected position (e.g. reset
by HOT AIR P/B before cool down of duct temperature below 70°C).
TRIM AIR SYSTEM FAULT
In case of a TRIM AIR SYStem FAULT, the corresponding message
appears amber on the EWD. This message is activated when a trim air
valve motor is stuck or if the downstream pressure of the HOT AIR PRV
is greater than 6.5 psi above the cabin pressure. It disappears as soon as
it drops below 5 psi above the cabin pressure. In this case, the trim air
system is completely lost, and each pack is controlled separately, pack
1 for the cockpit and pack 2 for the cabin to maintain pre-selected
temperature.
L+R CAB FAN FAULT
In case of a L+R CABin FAN FAULT the MASTER CAUTion comes
on, the aural warning sounds and the failure is shown amber on the EWD
associated to indications on the ECAM COND page. This failure does
not downgrade the temperature regulation.
LAV+GALLEY FAN FAULT
In case of LAVatory+GALLEY FAN FAULT, the corresponding message
appears amber on the EWD. Cabin zone temperature sensors are normally
ventilated by the lavatory and galley fan. Therefore cabin zone
temperature regulation is lost when a fan failure occurs. Cabin duct
temperature is fixed at 15°C. Cockpit temperature regulation is normal
(cockpit temperature sensor is ventilated by avionics ventilation system).
CTL 1(2)-A(B) FAULT
In case of failure of the lane A or B of an ASCS, the corresponding
message appears amber on the EWD.
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FLOW CONTROL & PACK COMPONENTS D/O (2)
OZONE FILTER (OPTION)
An ozone filter is installed upstream of each Flow Control Valve (FCV).
It is used for catalytic removal of ozone from the hot bleed air supplied
to the pack.
PRESSURE SENSORS AND FCV
Each pack has 3 pressure sensors. These sensors are used for:
- flow control, and actual flow calculation,
- icing detection.
The pack discharge pressure sensor detects an increase in the air cycle
machine turbine outlet pressure relative to the aircraft cabin. This indicates
that icing conditions exist. 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 Air Conditioning System Controllers (ACSCs).
ACSC 1 controls the FCV for pack 1, while ACSC 2 controls the FCV
for pack 2. ACSC 1 only is responsible for the flow calculation and sends
flow demand signals for ASCS 2. In normal conditions, each air
conditioning system controller 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: electro-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 back-up mode, the FCV flow is controlled by a downstream pressure
regulator. The back-up mode is electrically activated because the solenoid
2 must be energizes by the related ACSC, only in that situation the
downstream pressure of the FCV is pneumatically regulated.
BY-PASS VALVE
The BYPass (BYP) valve regulates the pack discharge temperature by
adding hot bleed air to the air cycle machine for quick pack response.
According to the water extractor temperature the air conditioning system
controller controls a (the) stepper motor that electrically operates the
BYP valve.
RAM AIR INLET FLAP
The ram air inlet flap modulates the airflow through the exchangers to
control the temperature of the pack outlet. According to the water extractor
temperature the air conditioning system controller controls an electric
actuator, which actuates the ram air inlet flap in order to obtain optimum
pack cooling airflow. The ram air inlet flap closes during take-off and
landing. The ACSC monitors the actuator position in speed and direction
by a contactless hall sensor.
A.ICE VALVEAn electro-mechanical actuator operates the Anti-Ice (A.ICE) valve. The
air conditioning system controller controls the valve. The main function
of the A.ICE valve is to remove ice build-up at the condenser from
components downstream of the turbine outlet (condenser tubing,
temperature sensors, check valves, mixing unit). The air conditioning
system controller uses the pack discharge pressure sensor to compare the
pack discharge pressure to the turbine outlet pressure. If the difference
between these two pressures exceeds a pre-determined limit, then icing
is assumed. As a result, the air conditioning system controller commands
the A.ICE valve to open and hot air flows directly into the turbine outlet
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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 A.ICE valve will fully close. The A.ICE valve
is identical and interchangeable with the system trim air valves.
AIR CYCLE MACHINE
The air cycle machine, which has a turbine, a compressor and a fan, cools
the air. The main component of the air cycle machine is a rotating shaft.
A turbine, a compressor and a fan are mounted along the shaft.
EXCHANGERS-REHEATER-CONDENSER
The air goes through two heat exchangers and a reheater before it enters
the condenser, which causes the air temperature to drop well below dew
point. The cooling agent for the primary heat exchanger and the main
heat exchanger is outside ram air. The reheater is used to raise the
temperature of the air before it reaches the turbine inlet to vaporize any
remaining water droplets for turbine protection.
WATER EXTRACTOR
The water extractor collects water droplets and drains them inside the
water extractor body in order to spray the collected water into the ram
airflow of the exchangers, to increase the cooling efficiency.
CHECK VALVE
The pack downstream check valve stops leakage of air from the
distribution system when the FCV is closed. The check valve is fitted to
the pressure bulkhead.
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OZONE FILTER (OPTION) ... CHECK VALVE
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PACK SENSORS DESCRIPTION/OPERATION (3)
PACK INLET PRESSURE SENSOR
The pack inlet pressure sensor signals a pack inlet pressure drop to the
Air Conditioning System Controller (ACSC). It is used to determine the
appropriate BYPass valve position. When the pack inlet pressure is low,
the BYP valve is controlled to a more open position in order to decrease
the Differential Pressure (DELTA P) of the air conditioning pack. At the
same time, the ram air inlet flap is controlled to a more open position to
compensate for the decreased efficiency of the turbine/compressor cycle.
Also, when engines are idle, if the cooling demand cannot be satisfied,
the engine idle setting can be changed by a thrust demand.
DELTA P SENSOR
A DELTA P sensor measures a differential pressure at the Flow Control
Valve (FCV) inlet. This DELTA P, which is equivalent to the airflow,
is converted into an electrical signal and sent to the ACSC. It is used for
ECAM display and FCV control.
COMPRESSOR DISCHARGE TEMPERATURE SENSOR
The compressor discharge temperature sensor signals the compressor
outlet temperature to the ACSC for pack temperature control and overheat
detection.
Pack temperature control:
- up to 180°C (385°F): normal operation,
- 180°C to 220°C (428°F): the ram air inlet flap opens more in order to
increase the RAM airflow.
The pack FAULT light comes on in if there is pack overheat of 260°C
(500°F). If the A/C is on ground, automatic FCV closure occurs.
PACK DISCHARGE PRESSURE SENSOR
The pack discharge pressure sensor measures the pressure difference
between turbine outlet and cabin underfloor pressure. The pack discharge
pressure sensor is mounted on the bulkhead between the air conditioning
bay and the pressurized cabin. It is connected to the corresponding ACSC.
If the ACSC detects a certain pressure difference, it opens the Anti ICE
(A.ICE) valve for the de-icing of the turbine outlet, condenser and
downstream ducting.
PACK TEMPERATURE SENSOR
The pack temperature sensor signals the water extractor temperature for
the pack outlet temperature control. The pack temperature sensor has two
thermistors: one sensing element is connected to lane 1 and the other to
lane 2 of the related ACSC. They are used to modulate the pack outlet
temperature.
PACK DISCHARGE TEMPERATURE SENSOR
The pack discharge temperature sensor signals the pack outlet temperature
to the ACSC for ECAM display. The pack outlet temperature sensor also
gives pack overheat warning indications if the pack outlet temperature
exceeds 95°C (203°F).
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PACK INLET PRESSURE SENSOR ... PACK DISCHARGE TEMPERATURE SENSOR
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COCKPIT & CABIN COMPONENTS D/O (3)
MIXER UNIT
The mixer unit mixes air from packs and recirculated air from the cabin
before distribution to each zone. The mixer unit, installed under the cabin
floor, uses cabin air which has entered the underfloor area and has been
drawn through recirculation 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% (the cabin fans operate at a
constant speed, but the airflow from the Pack Flow Control Valve (FCV)
can vary.)
MIXER UNIT TEMPERATURE SENSORS
There are two mixer unit temperature sensors, one on either side of the
mixer unit. They give the actual temperature of the mixer unit to the Air
Conditioning System Controllers (ASCSs). The cockpit mixer unit
temperature sensor is connected to the ACSC 1 and the cabin mixer unit
to the ACSC 2. Each mixer unit temperature sensor has two thermistors,
one connected to lane 1 and the other to the second lane of the ACSC.
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 PRV
The trim air Pressure Regulating Valve (PRV) is pneumatically operated
and electrically controlled by a solenoid. The solenoid controls the
ON/OFF function. The trim air PRV regulates the pressure of the air
supplied to the trim air valves, 4 psi above the cabin pressure. The
ON/OFF function solenoid de-energizes when the HOT AIR P/B is set
to OFF or when the temperature of any duct is above 88°C (190°F). This
closes the valve.
HOT AIR PRESSURE SWITCH
Due to a malfunction of the trim air PRV, the hot air pressure switch
signals overpressure to ACSCs 1 and 2 for ECAM display and the
Centralized Fault Display System(CFDS) and monitoring. If pressure
in the system is 6.5 psi greater than the cabin pressure, ACSC 1 activates
the ECAM system. This signal stays until the pressure falls below 5 psi.
TRIM AIR VALVES
The trim air valves lets the zone temperature be adjusted by modulating
the hot airflow added to air from the mixer unit. The trim air valves close
when the trim air PRV closes. The butterfly of the trim air valves is
controlled by a stepper motor. The trim air valve position is determined
using the step-counting principle.
DUCT TEMPERATURE SENSORS
Each duct temperature sensor detects duct temperature for the related
zone temperature control, indication and overheat detection to the ACSC.
Each duct temperature sensor has two thermistors, one connected to lane
1 and the other to the second lane of the ACSC. Each thermistor does
control, indication and overheat detection 88°C (190°F).
ZONE TEMPERATURE SENSORS
Each zone sensor detects the related zone temperature for zone
temperature control and indication on ECAM display. Each zone
temperature sensor has two thermistors, one connected to ACSC 1 and
the other to ACSC 2.
AIR CONDITIONING SYSTEM CONTROLLERS
During normal or abnormal operation the cockpit and cabin system is
controlled by the two ACSCs. Cabin zones demanding a higher
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temperature than that which is available from the mixer unit receive
additional hot trim-air added by the trim air valve. The trim air valves
are operated by ACSC 1 for the cockpit and ACSC 2 for the FWD and
aft cabin zones.
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MIXER UNIT ... AIR CONDITIONING SYSTEM CONTROLLERS
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ZONE TEMPERATURE CONTROLLER INTERFACES (3)
GENERAL
The function of the Air Conditioning System Controller (ACSC) is to
communicate with other systems via hardware interfaces.
SDAC
System data information is transmitted to the System Data Acquisition
Concentrator (SDAC) via ARINC buses for system monitoring. The
system data information is used for warning and display. These data are
temperature, valve position and others.
EIU
The ACSC sends data to both Engine Interface Units (EIUs). Each EIU
sends one discrete to the ACSC. EIUs 1 and 2 send to the ACSC:
- the take-off thrust used for pack ram air inlet closure,
- the High Pressure (HP) fuel valve position used for bleed demand
circulation and for engine start sequence, so that the pack Flow Control
Valves (FCVs) are controlled to close during engine start.
The ACSC sends to EIUs 1 and 2:
- the engine power increase used for bleed airflow increase,
- the bleed and the anti-ice status used for thrust limit calculation.
ADIRU 1
Air Data/Inertial Reference Unit (ADIRU) 1 sends data to the ACSC for
zone and pack temperature control. The A/C altitude is used for zone
temperature compensation and pack water extractor outlet temperature
limitation.
ECB
The ACSC sends data to the Electronic Control Box (ECB) and receives
an APU bleed valve open discrete. The ACSC sends to the ECB the
increase of APU flow used for increased bleed airflow.
When the ECB sends a signal to the ACSC, the APU bleed valve open
discrete is used for flow demand calculation.
DMU
The ACSCs send system main status data to the Data Management Unit
(DMU) for maintenance monitoring purposesfunctions.
The ACSC sends to the DMU:
- the trim-air Pressure Regulating Valve (PRV) position,
- pack flow, water extractor and pack compressor discharge temperatures,
BYPass valve and ram air inlet flap positions.
CFDIU
ACSC 2 sends BITE data to the Centralized Fault Display Interface Unit
(CFDIU) for system monitoring. The BITE data is used for temperature
control system monitoring.
AIR CONDITIONING SYSTEM CONTROLLERS
The ACSCs mainly receive temperature demands, flow demands and
CFDIU control signals and send back maintenance data signals. The
ACSCs also receive a signal from the DITCHING P/B, to close both pack
FCVs if there is a ditching. ACSC 1 and 2 receive a signal from the engine
FIRE P/B, to close the related pack FCV, in case of engine fire. The
Cabin Intercommunication Data System (CIDS) Director 1 sends a data
signal for ACSC 1, and the CIDS Director 2 sends a signal for ACSC 2
for temperature regulation (+ or - 2.5°C) from the Flight Attendant Panel
(FAP).
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FAN PARAMETERS
The ACSCs receive discrete signals from recirculation and toilet fans for
monitoring. The lavatory and galley extraction and the cabin recirculation
fan operation are used for monitoring and transmission to the SDACs
and CFDIU.
ANTI-ICE AND PNEUMATIC PARAMETERS
Anti-ice and pneumatic parameters are used to detect faults and to make
sure that the status of the bleed air system is transmitted to the CFDIU
and EIUs. The valve positions, low and high pressure, are used for anti-ice
system fault detection for the CFDIU and thrust limit calculation for the
EIUs.
LGCIU 2
Landing Gear Control and Interface Unit (LGCIU) 1 and 2 send a
ground/flight signal to both ACSCs for pack air inlet flap operation. The
ground/flight signal is used for pack ram air inlet flap closure during
take-off and landing phases.
BSCU
The Braking/Steering Control Unit (BSCU) sends a wheel signal to both
ACSCs for pack ram air inlet flap operation. The wheel speed is used for
pack ram air inlet flap closure during take-off and landing phases.
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GENERAL ... BSCU
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# EMERGENCY RAM AIR INLET D/O (3)
GENERAL
The A/C has one emergency ram air inlet flap located at the lower LH
side of the fuselage, sharing the same duct with the LP ground connection.
EMERGENCY RAM AIR INLET FLAP OPERATION
In case of failure of both packs, an emergency ram air inlet flap can be
opened for A/C ventilation or smoke removal. In case of smoke removal
or loss of both packs, the RAM AIR P/B must be set to ON. When set to
ON, and if DITCHING is not selected, the emergency ram air inlet flap
opens. The flap, installed between the LP GND connection and ram air
inlet, closes one side of the duct when air is supplied from the other side.
The check valve stays closed. The A/C must descend to less than 10000
ft. When the cabin ambient air differential pressure is less than 1 psi, the
pressure controller half opens the outflow