DOC AIRBUS | AMM A320FAIR INTAKE SYSTEM - DESCRIPTION AND OPERATION
** ON A/C NOT FOR ALL
** ON A/C NOT FOR ALL
** ON A/C NOT FOR ALL
1. General
The air intake system provides ambient air of sufficient quantity and quality to the APU. Its major components are:
** ON A/C NOT FOR ALL The air intake system provides ambient air of sufficient quantity and quality to the APU. Its major components are:
- diverter;
- air inlet (including actuator-driven flap);
- air duct.
- provide sufficient mass flow to the APU plenum chamber,
- minimization of pressure loss and flow distortion (thus also reducing the danger of APU surge),
- noise reduction,
- reduce the potential for foreign object ingestion;
- prevent exhaust gas (from APU and main engines) from re-entering the inlet,
- prevent the ingestion of fluids existing externally,
- prevent the accumulation of flammable fluids in the intake system.
2. Component Location
** ON A/C NOT FOR ALL 
Air Intake System - Component Location| ------------------------------------------------------------------------------- |
| FIN | FUNCTIONAL DESIGNATION | PANEL|ZONE|ACCESS | ATA |
| | | | | DOOR | REF. |
| ------------------------------------------------------------------------------- |
| DIVERTER - FIXED 311/ 314AR 49-16-41 |
| 312 |
| AIR INLET 313/ 314AR 49-16-42 |
| 314 |
| FLAP - AIR INLET 313/ 314AR 49-16-43 |
| 314 |
| NOSE - AIR INLET 313/ 314AR 49-16-44 |
| 314 |
| 4015KM ACTUATOR - AIR INLET FLAP 313/ 314AR 49-16-51 |
| 314 |
| AIR DUCT 315/ 315AL/ 49-16-45 |
| 316 316AR |
| DIFFUSER - AIR DUCT 315/ 315AL/ 49-16-45 |
| 316 316AR |
| ELBOW - AIR DUCT 315/ 315AL/ 49-16-45 |
| 316 316AR |
A. Fixed Diverter
The diverter which is installed just forward of the tailcone on the bottom the rear fuselage, serves two purposes:
The diverter which is installed just forward of the tailcone on the bottom the rear fuselage, serves two purposes:
(1) Its primary purpose is to improve the ram air recovery during in-flight APU operation. This is accomplished by positioning the inlet some 50mm into the airstream, thus the lowest energy portion of the aerodynamic boundary layer is prevented from entering the air inlet.
(2) Its secondary purpose is to divert any fluids (such as oil, hydraulic or de-icing fluid, fuel or water), which might be migrating aft along the fuselage during flight. They are thus prevented from entering the air inlet.
B. Air Inlet
The air inlet assembly is installed as a unit in a cutout in the bottom of the tailcone just forward of the APU compartment, positioned by 4 bolts. The interface to the air duct is attached to the APU compartment forward firewall. The inlet airstream area up to approximately 150mm (6in) forward of the interface to the APU compartment is covered with a CRES face sheet to serve as an extension of the APU compartment fireproof area. A fireproof gasket is used to join the air inlet assembly to the APU compartment firewall.
The air inlet consists of the following major components:
The air inlet consists of the following major components:
The air inlet assembly is installed as a unit in a cutout in the bottom of the tailcone just forward of the APU compartment, positioned by 4 bolts. The interface to the air duct is attached to the APU compartment forward firewall. The inlet airstream area up to approximately 150mm (6in) forward of the interface to the APU compartment is covered with a CRES face sheet to serve as an extension of the APU compartment fireproof area. A fireproof gasket is used to join the air inlet assembly to the APU compartment firewall.
The air inlet consists of the following major components:
The air inlet consists of the following major components:
(1) Air Inlet Body
This is essentially a U-shaped component, forming both side walls as well as the the rear portion of the upper wall. It is of a fiberglass fabric/aluminum core sandwich design. The upper wall is acoustically treated with feltmetal. Rails, which extend into the airstream, are incorporated along the side walls in order to prevent the ingression of fluids flowing along the tailcone outer surface.
This is essentially a U-shaped component, forming both side walls as well as the the rear portion of the upper wall. It is of a fiberglass fabric/aluminum core sandwich design. The upper wall is acoustically treated with feltmetal. Rails, which extend into the airstream, are incorporated along the side walls in order to prevent the ingression of fluids flowing along the tailcone outer surface.
(2) Air Inlet Flap
It is of a fiberglass fabric/Nomex core sandwich design without acoustic treatment. The flap is hinged at the forward end of the air inlet body and is operated by an attached actuator. It serves two purposes:
It is of a fiberglass fabric/Nomex core sandwich design without acoustic treatment. The flap is hinged at the forward end of the air inlet body and is operated by an attached actuator. It serves two purposes:
- to close the air inlet when the APU is not in operation.
- to form the forward portion of the upper wall when the APU is in operation.
(3) Air Inlet Nose
This item forms the lower wall of the air intake and is permanently installed in the air inlet body. It is of a CRES skin/aluminum core sandwich construction and is acoustically treated with feltmetal along the inlet airstream aft of the lip area.
This item forms the lower wall of the air intake and is permanently installed in the air inlet body. It is of a CRES skin/aluminum core sandwich construction and is acoustically treated with feltmetal along the inlet airstream aft of the lip area.
(4) Air Inlet Housing
This conventional aluminum structure attached to the air inlet body serves two functions:
This conventional aluminum structure attached to the air inlet body serves two functions:
- provide an attachment for the inlet flap actuator;
- serve as maintenance platform for work within the tailcone forward of the APU compartment.
(5) Air Inlet Actuator
This electrically operated linear actuator operates the air inlet flap. Its major components are:
This electrically operated linear actuator operates the air inlet flap. Its major components are:
- 28V DC motor with brake control (basic version),
- a limit switch at each end position,
- a flap position switch at each end position,
- thermal overload protection device.
(6) Air Inlet Body
This is essentially a U-shaped component, forming both side walls as well as the the rear portion of the upper wall. It is of a fiberglass fabric/aluminum core sandwich design. The upper wall is acoustically treated with feltmetal. Rails, which extend into the airstream, are incorporated along the side walls in order to prevent the ingression of fluids flowing along the tailcone outer surface.
This is essentially a U-shaped component, forming both side walls as well as the the rear portion of the upper wall. It is of a fiberglass fabric/aluminum core sandwich design. The upper wall is acoustically treated with feltmetal. Rails, which extend into the airstream, are incorporated along the side walls in order to prevent the ingression of fluids flowing along the tailcone outer surface.
(7) Air Inlet Flap
It is of an aluminium alloy machined part without acoustic treatment. The flap is hinged at the forward end of the air inlet body and is operated by an attached actuator. It serves two purposes:
It is of an aluminium alloy machined part without acoustic treatment. The flap is hinged at the forward end of the air inlet body and is operated by an attached actuator. It serves two purposes:
- to close the air inlet when the APU is not in operation.
- to form the forward portion of the upper wall when the APU is in operation.
(8) Air Inlet Nose
This item forms the lower wall of the air intake and is permanently installed in the air inlet body. It is of a CRES skin/aluminum shett metal construction and is acoustically treated with feltmetal along the inlet airstream aft of the lip area.
This item forms the lower wall of the air intake and is permanently installed in the air inlet body. It is of a CRES skin/aluminum shett metal construction and is acoustically treated with feltmetal along the inlet airstream aft of the lip area.
(9) Air Inlet Housing
This conventional aluminum structure attached to the air inlet body serves two functions:
This conventional aluminum structure attached to the air inlet body serves two functions:
- provide an attachment for the inlet flap actuator;
- serve as maintenance platform for work within the tailcone forward of the APU compartment.
(10) Air Inlet Actuator
This electrically operated linear actuator operates the air inlet flap. Its major components are:
This electrically operated linear actuator operates the air inlet flap. Its major components are:
- 28V DC motor with brake control (basic version),
- a limit switch at each end position,
- a flap position switch at each end position,
- thermal overload protection device.
C. Air Duct
The air duct forms the central portion of the air intake system, connecting the air inlet with the APU plenum chamber. It is located completely within the APU compartment and is installed on the access door 316AR. When subject door is opened, the air duct is dislocated from its normal installation position, thus permitting improved access to the APU.
The purpose is to duct the airflow to the APU and to reduce aerodynamic noise. In case of APU compartment fire, it retains its shape.
It consists of 2 major components, which are conventionally joined with brackets and fasteners:
The air duct forms the central portion of the air intake system, connecting the air inlet with the APU plenum chamber. It is located completely within the APU compartment and is installed on the access door 316AR. When subject door is opened, the air duct is dislocated from its normal installation position, thus permitting improved access to the APU.
The purpose is to duct the airflow to the APU and to reduce aerodynamic noise. In case of APU compartment fire, it retains its shape.
It consists of 2 major components, which are conventionally joined with brackets and fasteners:
(1) Diffuser
The purpose of the diffuser is, by means of expansion, to decelerate the airspeed and to decrease airflow turbulance. It also functions as a resonator-type muffler.
The 4 walls, joined with fasteners, are of a CRES face sheet/aluminum core double sandwich design. The aerodynamic surface is acoustically treated with feltmetal. A fireproof flexible seal minimizes air losses at the junction to the air inlet and provides for a flexible interface. Drainage provisions are incorporated into the lower wall.
The purpose of the diffuser is, by means of expansion, to decelerate the airspeed and to decrease airflow turbulance. It also functions as a resonator-type muffler.
The 4 walls, joined with fasteners, are of a CRES face sheet/aluminum core double sandwich design. The aerodynamic surface is acoustically treated with feltmetal. A fireproof flexible seal minimizes air losses at the junction to the air inlet and provides for a flexible interface. Drainage provisions are incorporated into the lower wall.
(2) Elbow
The purpose of the elbow is to redirect the airstream into the APU plenum chamber. In order to reduce aerodynamic losses, 2 guide vanes are incorporated. It also functions as a resonator-type muffler.
The design of the walls and their installation is identical to those of the diffusor. The guide vanes are on the entire external surface acoustically treated, their internal design is similar to that of the outer walls. They are assembled with the elbow side walls by means of bonded-in rails. A flexible fireproof seal at the elbow/APU junction minimizes air losses while providing a flexible interface. Drainage provisions are incorporated into the lower wall.
The purpose of the elbow is to redirect the airstream into the APU plenum chamber. In order to reduce aerodynamic losses, 2 guide vanes are incorporated. It also functions as a resonator-type muffler.
The design of the walls and their installation is identical to those of the diffusor. The guide vanes are on the entire external surface acoustically treated, their internal design is similar to that of the outer walls. They are assembled with the elbow side walls by means of bonded-in rails. A flexible fireproof seal at the elbow/APU junction minimizes air losses while providing a flexible interface. Drainage provisions are incorporated into the lower wall.
** ON A/C NOT FOR ALL
5. Interface
The air intake system has an interface with the control and monitoring system (Ref. AMM D/O 49-61-00-00).
** ON A/C NOT FOR ALL The air intake system has an interface with the control and monitoring system (Ref. AMM D/O 49-61-00-00).
6. Operation/Control and Indicating
The following components control the opening/closing of the air intake flap:
The following components control the opening/closing of the air intake flap:
- the MASTER SW pushbutton switch,
- the APU main relay 4KD (APU MAIN) and
- the ECB.
A. Opening of the Air Intake
(1) The following settings are required:
- busbar 301PP energized (carries 28V DC electrical power),
- circuit breaker 1KD (ECB SPLY) closed,
- circuit breaker 2KD (APU CTL) closed and
- MASTER SWITCH 14KD in the ON position.
(2) When you push the APU MASTER SWITCH in the ON position:
- the blue ON legend in the MASTER SW comes on,
- the APU main relay 4KD is energized,
- electrical power is supplied to the ECB,
- the ECB energizes the air intake flap actuator to open the flap.
- the air intake flap actuator moves the flap into the 'OPEN'-position within approximately 25s,
- when the air intake flap actuator reaches the end position 'retracted' (flap in 'OPEN'-position), a 'FLAP OPEN'-signal is transmitted back to the ECB,
- on the lower ECAM APU system page the FLAP OPEN indication comes on.
B. Closing of the Air Intake
(1) Normal APU Shutdown Procedure
(a) When you release the APU MASTER SW pushbutton switch in the off position:
- if the bleed air mode was used, a 60s cool-down cycle starts (counted from the bleed-air deactivation),
- if no bleed air mode was used, no cool-down cycle is started,
- when the APU speed has decreased to below 7%, the ECB sends a 'FLAP CLOSE'-command to the air intake flap actuator for 30s.
- the air intake flap actuator moves the flap into the 'CLOSED'-position within approximately 20s,
- when the air intake flap actuator reaches the end position 'extended' (flap in 'CLOSED'-position), a 'FLAP CLOSED'-signal is transmitted back to the ECB,
- the APU main relay 4KD is de-energized when the 30s have expired,
- electrical power is disconnected from the ECB.
(2) APU EMERGENCY STOP (Ground Signal)
(a) In case the ECB receives an 'APU EMERGENCY STOP'-command for a minimum of 150ms, the following sequence occurs:
- the ECB 59KD shuts down the APU immediately (no cool-down cycle),
- when the APU speed has decreased to below 7%, the ECB 59KD transmits a 'FLAP CLOSE'-command to the air intake flap actuator,
- the air intake flap actuator moves the flap into the 'CLOSE'-position within approximately 20s.
- when the air intake flap actuator reaches its end position 'extended' (flap in 'CLOSED'-position), a 'FLAP CLOSED'-signal is transmitted back to the ECB 59KD.
(b) After the MASTER SW has been set to the 'off'-position, the following sequence occurs:
- the APU main relay 4KD is de-energized,
- electrical power is disconnected from the ECB.
(3) Air Intake Flap Does Not Fully Open (Class 1 Fault)
(a) If the ECB 59KD Build-In Test Equipment (BITE) completes the Power Up Test (PUT) and does not receive a 'FLAP OPEN'-signal within 30 seconds of transmitting the 'OPEN FLAP'-command, the following procedure occurs:
- the ECB interrupts the APU start procedure,
(b) After the MASTER SW has been set to the 'off'-position, the following sequence occurs:
- the ECB transmits a 'FLAP CLOSE'-command to the air intake flap actuator,
- the air intake flap actuator moves the flap into the 'CLOSED'-position within approximately 20s,
- when the air intake flap actuator reaches its end position 'extended' (flap in 'CLOSED'-position), a 'FLAP CLOSED'-signal is transmitted back to the ECB 59KD.
- the APU main relay 4KD is de-energized when the 30s have expired,
- electrical power is disconnected from the ECB.
(4) Normal APU Shutdown Procedure
(a) When you release the APU MASTER SW pushbutton switch in the off position:
- if the bleed air mode was used, a 60s cool-down cycle starts (counted from the bleed-air deactivation),
- if no bleed air mode was used, no cool-down cycle is started,
- when the APU speed has decreased to below 7%, the ECB sends a 'FLAP CLOSE'-command to the air intake flap actuator for 30s.
- the air intake flap actuator moves the flap into the 'CLOSED'-position within approximately 20s,
- when the air intake flap actuator reaches the end position 'extended' (flap in 'CLOSED'-position), a 'FLAP CLOSED'-signal is transmitted back to the ECB,
- the APU main relay 4KD is de-energized when the 30s have expired,
- electrical power is disconnected from the ECB.
(5) APU EMERGENCY STOP (Ground Signal)
(a) In case the ECB receives an 'APU EMERGENCY STOP'-command for a minimum of 150ms, the following sequence occurs:
- the ECB 59KD shuts down the APU immediately (no cool-down cycle),
- when the APU speed has decreased to below 7%, the ECB 59KD transmits a 'FLAP CLOSE'-command to the air intake flap actuator,
- the air intake flap actuator moves the flap into the 'CLOSE'-position within approximately 20s.
- when the air intake flap actuator reaches its end position 'extended' (flap in 'CLOSED'-position), a 'FLAP CLOSED'-signal is transmitted back to the ECB 59KD.
(b) After the MASTER SW has been set to the 'off'-position, the following sequence occurs:
- the APU main relay 4KD is de-energized,
- electrical power is disconnected from the ECB.
(6) APU PROTECTIVE SHUTDOWN (not including Emergency S/D)
(a) In case a protective S/D occurs (not including Emergency S/D)
- the ECB (59KD) stops the APU immediately (no cool-down cycle),
- the ECB transmits a FLAP CLOSE command to the air intake flap actuator, 15 minutes after speed is below 7% if the APU MASTER SW is set to OFF position. If the protective S/D occurs between Flight Phase 1 and Flight Phase 4, the 15 minutes will not start counting until the aircraft is in the air (at Flight Phase).
- the air intake flap actuator moves the flap into the CLOSE position within approximately 20 s.
- when the air intake flap actuator gets its end position extended (flap in CLOSED position), a FLAP CLOSED signal is transmitted back to the ECB (59KD).
(b) After the M/S has been set to the OFF position and 30 s after activation of the FLAP CLOSED command, the following sequence occurs:
- the APU main relay 4KD is de-energized,
- electrical power is disconnected from the ECB.
(7) Air Intake Flap Does Not Fully Open (Class 1 Fault)
(a) If the ECB 59KD Build-In Test Equipment (BITE) completes the Power Up Test (PUT) and does not receive a 'FLAP OPEN'-signal within 30 seconds of transmitting the 'OPEN FLAP'-command, the following procedure occurs:
- the ECB interrupts the APU start procedure,
(b) After the MASTER SW has been set to the 'off'-position, the following sequence occurs:
- the ECB transmits a 'FLAP CLOSE'-command to the air intake flap actuator,
- the air intake flap actuator moves the flap into the 'CLOSED'-position within approximately 20s,
- when the air intake flap actuator reaches its end position 'extended' (flap in 'CLOSED'-position), a 'FLAP CLOSED'-signal is transmitted back to the ECB 59KD.
- the APU main relay 4KD is de-energized when the 30s have expired,
- electrical power is disconnected from the ECB.
C. Built-In Test Equipment (BITE) of the ECB 59KD
(1) The BITE of the ECB automatically monitors the APU and the APU system control and isolates any component malfunctions. The ECB will shut down the APU when:
- the air intake flap actuator does not supply a 'FLAP OPEN'-signal to the ECB. This will occur only when a signal has not been received for 0.5s and the APU speed is more than 7%,
- the air intake flap does not open within 30s of driver start by the ECB 59KD,
(2) When the APU is in operation and the BITE detects a malfunction, the following sequence occurs:
- the ECB will shut the APU immediately down (no cool-down cycle),
- the amber FAULT legend in the MASTER SW comes on and stays on,
- a caution
'APU AUTO SHUT DOWN
- MASTER SW ...................... OFF
is shown on the lower part of the ECAM upper display unit (Ref. AMM D/O 49-70-00-00).
(3) When the MASTER SW is set to the 'off'-position, the following sequence of operation occurs:
- the amber FAULT legend in the MASTER SW goes off,
- the ECB transmits a 'FLAP CLOSE'-command to the air intake flap actuator for 30 seconds,
- the air intake flap actuator operates to close the air intake flap within 20s.
- when the air intake flap actuator reaches its end position 'extended' (flap in 'CLOSED'-position), a 'FLAP CLOSED'-signal is transmitted back to the ECB.
- the APU MAIN relay 4KD de-energizes when the 30s have expired,
- electrical power is disconnected from the ECB.
D. Indications (Ref. 49-70-00)
(1) If the air intake flap does not move to the fully open position within 30s, a Class 1 Fault will occur. APU AUTO SHUT DOWN occurs and the subsequent indications are given:
(a) a continuous amber FAULT legend in the MASTER SW.
(b) Glareshield panel 131VU (130VU) MASTER CAUT annunciator lights:
- steady amber MASTER CAUT annunciator lights,
- single chime.
(c) On the ECAM upper display unit:
- an amber caution 'APU AUTO SHUT DOWN - MASTER SW OFF' shows on the lower part of the Engine/Warning page,
- INOP SYS - APU is shown on the ECAM status page,
- no APU AVAIL indication is given on the ECAM lower display unit.
(2) When an APU EMERGENCY SHUT DOWN occurs on the ground (because an APU EMERGENCY STOP ground signal has been received by the ECB 59KD), indications are given on:
(a) MASTER SW 14KD on panel 25VU:
- continuous amber FAULT legend in the switch.
(b) Glareshield panel 131VU (130VU) MASTER CAUT annunciator lights:
- steady amber MASTER CAUT attention getters,
- single chime.
(c) On the ECAM upper display unit:
- an amber caution, APU EMERG SHUTDOWN - MASTER SW OFF shows on lower part of warning page.
(3) When the air intake flap does not fully close within 30s, a message indication is given on:
ECAM Status Page (lower right corner):
ECAM Status Page (lower right corner):
- APU (indicates that a Class 2 Fault has occurred and is kept in the BITE Memory of the ECB 59KD).
E. ECB 59KD BITE Memory
The BITE system of the ECB 59KD records all the system faults in the BITE memory. Access to these is through the Centralized Fault Display System (CFDS) (Ref. AMM D/O 49-73-00-00).
The BITE system of the ECB 59KD records all the system faults in the BITE memory. Access to these is through the Centralized Fault Display System (CFDS) (Ref. AMM D/O 49-73-00-00).