DOC AIRBUS | AMM A320FENGINE FIRE AND OVERHEAT DETECTION - DESCRIPTION AND OPERATION
** ON A/C NOT FOR ALL
** ON A/C NOT FOR ALL
** ON A/C NOT FOR ALL
** ON A/C NOT FOR ALL
** ON A/C NOT FOR ALL
1. General
The cause of the fire can be an overheat or a leak of flammable fluid. An engine fire is a risk for aircraft safety.
Thermo-sensitive elements detect fire or overheat conditions. They send the fire warnings through the Fire Detection Unit (FDU) when the temperature is more than permitted in the monitored area of the engine.
The ENG/APU FIRE panel (1WD) includes the controls, indications and a test function for each engine.
In the section related to the engine fire detection of this panel, two functions are available:
** ON A/C NOT FOR ALL The cause of the fire can be an overheat or a leak of flammable fluid. An engine fire is a risk for aircraft safety.
Thermo-sensitive elements detect fire or overheat conditions. They send the fire warnings through the Fire Detection Unit (FDU) when the temperature is more than permitted in the monitored area of the engine.
The ENG/APU FIRE panel (1WD) includes the controls, indications and a test function for each engine.
In the section related to the engine fire detection of this panel, two functions are available:
- A FIRE warning that comes on red on the ENG 1(2) FIRE pushbutton switch after a positive fire detection
- A manual system test function.
- Two fire detection loops installed in parallel in the fire zones and connected to the FDU. Each fire detection loop has three detectors connected in parallel.
- One FDU for each engine, which processes signals from the detectors
- An ENG/APU FIRE panel on the overhead panel (20VU) with:
. One ENG FIRE pushbutton switch for each engine
. One TEST pushbutton switch for each engine, and - The related warnings and indications.
NOTE: For the Auxiliary Power Unit (APU), refer to ATA chapter 26-13-00.
2. Component Location
Pylon Fire Detectors - Component Location ** ON A/C NOT FOR ALL
Pylon Fire Detectors - Component Location ** ON A/C NOT FOR ALL
Pylon Fire Detectors - Component Location ** ON A/C NOT FOR ALL Pylon Fire Detectors - Component Location ** ON A/C NOT FOR ALL A. Fire Detection Units (FDUs)
The FDUs are installed in zone 127.
The FDUs are installed in zone 127.
B. ENG/APU FIRE Panel
The ENG/APU FIRE panel (1WD) is on the cockpit overhead panel (20VU).
The ENG/APU FIRE panel (1WD) is on the cockpit overhead panel (20VU).
C. Fire Detection Loops
On each engine, there are two continuous loops for the fire detection system. Each fire detection loop has three fire detectors connected in parallel.
They are installed in pairs (loop A/loop B):
On each engine, there are two continuous loops for the fire detection system. Each fire detection loop has three fire detectors connected in parallel.
They are installed in pairs (loop A/loop B):
- At the pylon forward mount
- On the engine gearbox
- On the engine case N-flange.
| FIN | FUNCTIONAL DESIGNATION | PANEL | ZONE | ACCESS DOOR | ATA REF |
|---|---|---|---|---|---|
| ** ON A/C NOT FOR ALL | |||||
| 1WD | ENG/APU FIRE PNL | 210 | 26-12-12 | ||
| 2WD1 | FDU-ENG1 | 126 | 26-12-34 | ||
| 2WD2 | FDU-ENG2 | 126 | 26-12-34 | ||
| 3WD1 | DET-FIRE, ENG 1 PYLON LOOP A | 415 | 26-12-16 | ||
| 3WD2 | DET-FIRE, ENG 2 PYLON LOOP A | 425 | 26-12-16 | ||
| 4WD1 | DET-FIRE, ENG 1 PYLON LOOP B | 415 | 26-12-16 | ||
| 4WD2 | DET-FIRE, ENG 2 PYLON LOOP B | 425 | 26-12-16 | ||
| 4001WD1 | DET-FIRE, CORE VENT LOOP A | 450 | 26-12-17 | ||
| 4001WD2 | DET-FIRE, CORE VENT LOOP B | 460 | 26-12-17 | ||
| 4002WD1 | DET-FIRE, CORE AGB LOOP A | 450 | 26-12-00 | ||
| 4002WD2 | DET-FIRE, CORE AGB LOOP B | 450 | 26-12-00 | ||
| 31WD1 | HARNESS-FIRE DET, ENG 1 PYLON LOOP A STUD A | 415 | 26-12-63 | ||
| 31WD2 | HARNESS-FIRE DET, ENG 2 PYLON LOOP A STUD A | 425 | 26-12-63 | ||
| 32WD1 | HARNESS-FIRE DET, ENG 1 PYLON LOOP A STUD C | 415 | 26-12-63 | ||
| 32WD2 | HARNESS-FIRE DET, ENG 2 PYLON LOOP A STUD C | 425 | 26-12-63 | ||
| 41WD1 | HARNESS-FIRE DET, ENG 1 PYLON LOOP B STUD A | 415 | 26-12-63 | ||
| 41WD2 | HARNESS-FIRE DET, ENG 2 PYLON LOOP B STUD A | 425 | 26-12-63 | ||
| 42WD1 | HARNESS-FIRE DET, ENG 1 PYLON LOOP B STUD C | 415 | 26-12-63 | ||
| 42WD2 | HARNESS-FIRE DET, ENG 2 PYLON LOOP B STUD C | 425 | 26-12-63 | ||
3. System Description
The fire detection system is of the electro-pneumatic type. On each engine, there are two continuous loops for the fire detection.
The loops are connected in parallel to an FDU. The connection is made through an AND logic to prevent unwanted FIRE warnings.
If there is a failure of one loop, the AND logic becomes an OR logic. The aircraft can be released in this configuration.
The FDU monitors the fire detection loops. The monitoring device shows the loss of a fire detection loop to the crew members (Flight Warning System(FWS)).
For one engine:
** ON A/C NOT FOR ALL The fire detection system is of the electro-pneumatic type. On each engine, there are two continuous loops for the fire detection.
The loops are connected in parallel to an FDU. The connection is made through an AND logic to prevent unwanted FIRE warnings.
If there is a failure of one loop, the AND logic becomes an OR logic. The aircraft can be released in this configuration.
The FDU monitors the fire detection loops. The monitoring device shows the loss of a fire detection loop to the crew members (Flight Warning System(FWS)).
For one engine:
- Each loop has three fire detectors connected in parallel. The detectors are installed in the nacelle and pylon fire zones.
- Each loop is connected to a different channel of the FDU.
- Each loop is connected through the related channel to four of the eight lamps in a red warning light which is the same for the two loops. This warning light is part of the ENG 1(2) FIRE pushbutton switch on the ENG/APU FIRE panel (overhead panel).
A test of the fire detection system is possible with the TEST pushbutton switch on the ENG/APU FIRE panel.
4. Power Supply
The engine fire and overheat detection system gets the electrical power from the DC system of the aircraft.
The power is supplied to the fire detector assemblies through harnesses, from the pylon junction box to the responder studs of the fire detector.
High-temperature harnesses (SiO2 cables) are used for pylon floor detection and for part of the Accessory Gearbox (AGB) and turbine detection. These cables are semi-rigid with silicon dioxide (SiO2) material for its dielectric properties. They are resistant to temperatures of more than 1093°C (2000°F) for three hours and strong vibrations.
The engine fire and overheat detection system gets the electrical power from the DC system of the aircraft.
The power is supplied to the fire detector assemblies through harnesses, from the pylon junction box to the responder studs of the fire detector.
High-temperature harnesses (SiO2 cables) are used for pylon floor detection and for part of the Accessory Gearbox (AGB) and turbine detection. These cables are semi-rigid with silicon dioxide (SiO2) material for its dielectric properties. They are resistant to temperatures of more than 1093°C (2000°F) for three hours and strong vibrations.
A. Circuit Breakers
The system is supplied through these circuit breakers:
The system is supplied through these circuit breakers:
| ------------------------------------------------------------------------------- |
| FIN PANEL/LOCATION DESIGNATION BUS ATA REF. |
| ------------------------------------------------------------------------------- |
| 7WD1 49VU A06 ENGINE/1/FIRE DET/LOOP A 401PP 26-12-00 |
| 8WD1 121VU Q38 ENGINE/ENG1/FIRE DET/LOOP B 202PP 26-12-00 |
| 7WD2 121VU Q39 ENGINE/ENG2/FIRE DET/LOOP A 202PP 26-12-00 |
| 8WD2 49VU A07 ENGINE/2/FIRE DET/LOOP B 401PP 26-12-00 |
| ------------------------------------------------------------------------------- |
5. Interface
The engine fire-detection system has an interface with the systems that follow:
** ON A/C NOT FOR ALL The engine fire-detection system has an interface with the systems that follow:
- Electrical power: DC ancillary equipment (Ref. 24-68-00)
- Centralized Fault Display Interface Unit (CFDIU) (Ref. AMM D/O 31-32-00-00)
- Flight Warning Computer (FWC) (Ref. AMM D/O 31-52-00-00)
- Landing Gear Control and Interface Unit (LGCIU) (Ref. AMM D/O 32-31-00-00)
- Annunciator light test and dimming (Ref. AMM D/O 33-14-00-00)
- Functional interfaces (Ref. AMM D/O 73-25-00-00).
6. Component Description
The components of the fire detection system for one engine are:
The components of the fire detection system for one engine are:
- An ENG/APU FIRE panel on the overhead panel with:
. One ENG FIRE pushbutton switch
. One TEST pushbutton switch. - Two fire detection loops installed in parallel in the fire zones and connected to an FDU.
Each fire detection loop has three detectors connected in parallel. - One FDU for each engine, which processes signals from the detectors.
A. ENG/APU FIRE Panel FIN: 1-WD
(1) ENG 1(2) FIRE pushbutton switch
To push the ENG 1(2) FIRE pushbutton switch, the safety guard must be open.
Each pushbutton switch has three primary functions:
To push the ENG 1(2) FIRE pushbutton switch, the safety guard must be open.
Each pushbutton switch has three primary functions:
- Show the FIRE warning from the FDU
- Operate the microswitches related to the extinguishing procedure
- Discharge the fire extinguishing bottles 1 and 2.
NOTE: For the last two functions, refer to ATA chapter 26-21-00.
(2) TEST pushbutton switch
The TEST pushbutton switch (one for each engine) does a check of the condition of:
The TEST pushbutton switch (one for each engine) does a check of the condition of:
- The fire detectors (loops A and B), FDU, indications, warnings and related wiring (loop test)
- The percussion cartridge filaments of the fire extinguisher bottles and the related wiring (squib test).
B. Fire Detectors
Each fire and overheat detector has a sensing element and responder assembly.
Each fire and overheat detector has a sensing element and responder assembly.
(1) Sensing element
A sensing element is a tube with an outer diameter of 0.063 in. (1.6 mm).
It has a hydrogen-charged titanium core with a spiral wound around it. This spiral is made of an inert material which has a special property: it can release and absorb a gas.
The space between the sensing-element outer-tube wall and the core is filled with helium.
The initial pressure of the helium is related to the pre-set temperature limit selected for each sensing element.
The sensing element reacts according to the ideal gas law.
One end of the sensing element is hermetically soldered and the other one is connected to a 1 in. (25.4 mm) diameter stainless steel body referred to as the responder.
A sensing element is a tube with an outer diameter of 0.063 in. (1.6 mm).
It has a hydrogen-charged titanium core with a spiral wound around it. This spiral is made of an inert material which has a special property: it can release and absorb a gas.
The space between the sensing-element outer-tube wall and the core is filled with helium.
The initial pressure of the helium is related to the pre-set temperature limit selected for each sensing element.
The sensing element reacts according to the ideal gas law.
One end of the sensing element is hermetically soldered and the other one is connected to a 1 in. (25.4 mm) diameter stainless steel body referred to as the responder.
(2) Responder assembly
The responder has a chamber connected to two pressure switches: an ALARM switch and a MONITOR switch. The free end of the responder is connected to the aircraft electrical circuit.
The detector has two sensing functions. It senses an overall "average" temperature and a highly-localized "discrete" temperature caused by an impinging flame or hot gases. As a result, the ALARM switch closes. It is not possible to adjust the "average" and "discrete" temperatures.
The averaging and discrete functions are reversible.
When the sensor tube is cooled, the average gas pressure decreases and the core material absorbs the discrete hydrogen gas.
If there is a leak on the detector, the gas pressure decreases, which causes the MONITOR switch to open and sends a detector fault signal.
Then, the system does not operate during the test.
The responder has a chamber connected to two pressure switches: an ALARM switch and a MONITOR switch. The free end of the responder is connected to the aircraft electrical circuit.
The detector has two sensing functions. It senses an overall "average" temperature and a highly-localized "discrete" temperature caused by an impinging flame or hot gases. As a result, the ALARM switch closes. It is not possible to adjust the "average" and "discrete" temperatures.
The averaging and discrete functions are reversible.
When the sensor tube is cooled, the average gas pressure decreases and the core material absorbs the discrete hydrogen gas.
If there is a leak on the detector, the gas pressure decreases, which causes the MONITOR switch to open and sends a detector fault signal.
Then, the system does not operate during the test.
(3) Location
The fire detection loop has three fire detectors connected in parallel. They are installed at the engine-to-pylon forward mount, on the engine gearbox and on the engine case N-flange.
The fire detection loop has three fire detectors connected in parallel. They are installed at the engine-to-pylon forward mount, on the engine gearbox and on the engine case N-flange.
(4) Installation
The fire detectors are installed in pairs on preformed stainless-steel supports on the engine.
The sensing elements are installed with quick-release clamps with Teflon bushings, and are resistant in continuous-high temperature operation.
The fire detectors are installed in pairs on preformed stainless-steel supports on the engine.
The sensing elements are installed with quick-release clamps with Teflon bushings, and are resistant in continuous-high temperature operation.
C. Fire Detection Unit (FDU)
The FDU sends the signals received from the fire detection loops.
There are three functional modules:
The FDU sends the signals received from the fire detection loops.
There are three functional modules:
- Two channels that operate independently (one for each detection loop)
- One monitoring circuit (for maintenance only).
(1) The channels
Each channel has its own power supply.
The two channels normally operate together, with an AND logic, for the fire detection. But if one loop does not operate, the other loop can operate independently.
Each channel has its own power supply.
The two channels normally operate together, with an AND logic, for the fire detection. But if one loop does not operate, the other loop can operate independently.
(a) Input signals
Each channel receives and analyzes continuously the signal from the related detection loop. Three comparators are used for this analysis:
Each channel receives and analyzes continuously the signal from the related detection loop. Three comparators are used for this analysis:
- The FIRE comparator
- The CONTAMINATION comparator
- The INTEGRITY comparator.
(b) Output signals
The output signals are generated through discrete signals and/or the ARINC 429 bus. The fire warning signals (aural and/or visual) thus generated are transmitted to the cockpit.
The output signals are generated through discrete signals and/or the ARINC 429 bus. The fire warning signals (aural and/or visual) thus generated are transmitted to the cockpit.
(2) Monitoring circuit
The monitoring circuit continuously analyses and monitors the fire detection system.
If there is a failure of the system, the monitoring circuit:
The monitoring circuit continuously analyses and monitors the fire detection system.
If there is a failure of the system, the monitoring circuit:
- Memorizes the fault in a non-volatile memory
- Isolates the faulty channel
- Sends the applicable discrete signals (LOOP A(B) INOP ENG 1 (2) to FWC 1(2))
- Transmits continuously a system status message to the CFDIU 1(2) through the ARINC 429 bus.
7. Operation/Control and Indicating
A. Fire Detection Unit (FDU)
(1) Operation of the channels
The two channels A and B of the FDU are the same but each channel has its own fire detection loop.
The input section of each channel has a bridge circuit with:
The two channels A and B of the FDU are the same but each channel has its own fire detection loop.
The input section of each channel has a bridge circuit with:
- A reference voltage
- A variable loop voltage with the three fire detectors in parallel.
The reference voltage is sent to the three comparators (FIRE, INTEGRITY and CONTAMINATION) and forms the threshold values. A resistor, upstream of each comparator, adjusts this reference voltage which becomes the comparator threshold value.
The resistance value of each fire detector is different to make identification of the failure zone possible if a failure of the loops (A or B) occurs.
The resistance of the loop changes when a change of state occurs in the monitored areas of the engine. This generates a variable loop voltage at the three comparators.
The comparator outputs are sent on the FIRE and FAULT logic gates. The logic gates generate the alarm outputs.
(a) Normal conditions
In normal conditions (no failure, no fire, no test), the variable voltage of the loop is:
In normal conditions (no failure, no fire, no test), the variable voltage of the loop is:
- More than threshold 1 of the integrity comparator
- Less than threshold 2 of the fire and contamination thresholds.
(b) FAULT circuit
1 INTEGRITY fault
A failure of the fire detector (responder/sensing element) causes the equivalent resistance of the three other fire detectors to increase.
A detector can be unserviceable because of:
A failure of the fire detector (responder/sensing element) causes the equivalent resistance of the three other fire detectors to increase.
A detector can be unserviceable because of:
- The opening of a MONITOR switch installed in series with an integral resistance,or
- The loss of the electrical signal. The loop voltage decreases below threshold 1 of the INTEGRITY comparator: this generates a LOOP A(B) INOP signal.
This failure description is also applicable when there is an accidental grounding of the responder.
2 CONTAMINATION fault
If there is contamination of the responder or of the connectors of the FDU:
If there is contamination of the responder or of the connectors of the FDU:
- The equivalent resistance decreases.
- The loop voltage is more than threshold 2 and less than threshold 3.
- The CONTAMINATION comparator supplies the logic gates and generates a FAULT signal.
(c) FIRE circuit
The detection of a fire by one of the responders causes the related ALARM switch to close.
This generates a voltage that is more than the threshold of the INTEGRITY and CONTAMINATION comparators. The FIRE comparator supplies the logic gates and transmits a FIRE signal.
The detection of a fire by one of the responders causes the related ALARM switch to close.
This generates a voltage that is more than the threshold of the INTEGRITY and CONTAMINATION comparators. The FIRE comparator supplies the logic gates and transmits a FIRE signal.
(2) Controller circuit
The controller circuit operating-software:
The controller circuit operating-software:
- Monitors the two detection loops
- Isolates the defective detector and loop circuit and memorizes the failures in a non-volatile memory
- Does a check of the fire test circuit when it is activated
- Does the self-test at the first power-up of the FDU
- Does the built-in test and transmits the test results on the ARINC 429 bus
- Transmits the failure signals to the CFDIU through the ARINC 429 bus
- Continuously transmits current and/or previous system status on the ARINC 429 bus
- Supplies a serial bus interface and transmits commands and data.
(3) Indicating
(a) FAULT warnings
FAULT warnings are generated through discrete signals.
FAULT warnings are generated through discrete signals.
1 There is an INOP signal if one of the conditions that follow occurs:
- Electrical failure (loss of power, connector not connected)
- Failure in a detector
- Failure in a detection circuit
- Detection of a single fire-detection loop for more than 16 seconds while the other loop is in normal condition.
2 The FAULT warning signals thus generated are transmitted to the cockpit, at the locations that follow:
- MASTER CAUT light
- Upper ECAM DU: ENG 1 (2) LOOP A (B) FAULT or ENG 1 (2) DET FAULT.
NOTE: The failure message is also transmitted continuously in plain language through the ARINC 429 bus to the CFDIU.
(b) FIRE warnings
FIRE warnings are generated through discrete signals.
FIRE warnings are generated through discrete signals.
1 There is a FIRE warning signal if one of the conditions that follow occurs:
- FIRE A and FIRE B
- FIRE A and FAULT B
- FAULT A and FIRE B
- FAULT A and FAULT B in less than five seconds.
2 The FIRE warning signals thus generated are transmitted to the cockpit, at the locations that follow:
- ENG/APU FIRE panel (1WD): ENG/FIRE pushbutton switch
- ENG panel (115VU): ENG/FIRE/FAULT annunciator
- MASTER WARN light
- Upper ECAM DU: ENG 1 (2) FIRE and fire extinguishing procedure
- Lower ECAM DU: engine page.
8. BITE Test
A. Operational Test
Through the operational test, the pilot can monitor and start the fire protection system. This test is part of the daily check-list and is available each time it is necessary.
The operational test can be done on the ground or in flight.
From the ENG/APU FIRE panel, a TEST pushbutton switch (one for each engine) does a check of the condition of:
When you push the TEST pushbutton switch and the fire warning indications come on, the fire detection system is operational.
For engine 1(2):
If the failure is detected during the test sequence, a FAULT message comes into view on the lower ECAM DU (for example ENG 1 (2) LOOP A(B) FAULT).
Through the operational test, the pilot can monitor and start the fire protection system. This test is part of the daily check-list and is available each time it is necessary.
The operational test can be done on the ground or in flight.
From the ENG/APU FIRE panel, a TEST pushbutton switch (one for each engine) does a check of the condition of:
- The fire detectors (loops A and B), Fire Detection Unit (FDU), indications, warnings and related wiring (loop test)
- The percussion cartridge filaments of the fire extinguisher bottles and the related wiring (squib test).
When you push the TEST pushbutton switch and the fire warning indications come on, the fire detection system is operational.
For engine 1(2):
- On the ENG/APU FIRE panel (1WD):
. The ENG 1 FIRE legend comes on.
. The SQUIB and DISCH legends come on. - On the ENG panel (115VU):
. The FIRE legend comes on. - On panels 130VU and 131VU:
. The MASTER WARN lights flash. - On the upper ECAM DU:
. The red ENG 1 FIRE indication comes into view. - On the lower ECAM DU:
. The ENGINE page comes into view. - The Continuous Repetitive Chime (CRC) sounds.
If the failure is detected during the test sequence, a FAULT message comes into view on the lower ECAM DU (for example ENG 1 (2) LOOP A(B) FAULT).
NOTE: The TEST pushbutton switch must be held while you do the test.
B. Built-In Test Equipment (BITE)
(1) Description
The function of the BITE is:
The FDU is a type-2 system. The FDU BITE functions are as follows:
The BITE test of the FDU is done at power-up or when the maintenance-test discrete signal is sent from the Multipurpose Control and Display Unit (MCDU) through the CFDIU. In the two conditions, the BITE test is done with the aircraft on the ground only.
After the operator gets access from the MCDU, the CFDIU shows the
"FIRE PROT: FDU 1 (2)" menu and shows the data on the MCDU.
The primary functions are:
BITE test duration:
During a system test, all the detectors are isolated from the FDU. The detector conditions are simulated by the BITE to do a test of all the failures in the FDU and its connections.
The BITE can tell if the failure is in the detector or in the circuit.
The function of the BITE is:
- To monitor the condition of the FDU and the related inputs
- To analyze and confirm the faults
- To store them in the Non-Volatile Memory (NVM).
The FDU is a type-2 system. The FDU BITE functions are as follows:
- Acquisition of discrete input signals
- Link with the Centralized Fault Display System (CFDS) (through an ARINC 429 bus)
- Memorization of failure in an NVM
- Test.
The BITE test of the FDU is done at power-up or when the maintenance-test discrete signal is sent from the Multipurpose Control and Display Unit (MCDU) through the CFDIU. In the two conditions, the BITE test is done with the aircraft on the ground only.
After the operator gets access from the MCDU, the CFDIU shows the
"FIRE PROT: FDU 1 (2)" menu and shows the data on the MCDU.
The primary functions are:
- LAST LEG/GND REPORT
- PREVIOUS LEGS REPORT
- LRU IDENTIFICATION
- TROUBLE SHOOTING DATA
- CLASS 3 FAULTS
- TEST.
BITE test duration:
- At power-up: 60 seconds
- At the maintenance test: 60 seconds.
During a system test, all the detectors are isolated from the FDU. The detector conditions are simulated by the BITE to do a test of all the failures in the FDU and its connections.
The BITE can tell if the failure is in the detector or in the circuit.
(2) The BITE uses the test combinations that follow:
- Loop A NORMAL and Loop B NORMAL
- Loop A FIRE and Loop B FIRE
- Loop A INTEGRITY FAULT and Loop B FIRE
- Loop A NORMAL and Loop B NORMAL
- Loop A FIRE and Loop B INTEGRITY FAULT
- Loop A FIRE for less than 17 seconds while Loop B is NORMAL
- Loop A FIRE for more than 17 seconds while Loop B is NORMAL
- Loop B FIRE for less than 17 seconds while Loop A is NORMAL
- Loop B FIRE for more than 17 seconds while Loop A is NORMAL
- Loop A NORMAL and Loop B NORMAL
- Loop A CONTAMINATION FAULT and then Loop B CONTAMINATION FAULT in five seconds.