ch-26; fire protection

7/27/2019 ch-26; fire protection

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Section 26-00 : FIRE PROTECTION - GENERAL

----------------------------------------------------------------------------! GLOSSARY OF ABBREVIATIONS !

----------------------------------------------------------------------------! ABBREVIATION ! SIGNIFICATION !----------------------------------------------------------------------------! BAT ! Battery !! BITE ! Built in Test Equipment !! CAP ! Crew Alerting Panel !! CLA ! Condition Lever Angle !! DISCH ! Discharge !! ENG ! Engine !! FUEL SOV ! Fuel Shut Off Valve !! LP ! Low Pressure !! PLA ! Power Lever Angle !----------------------------------------------------------------------------

1. GeneralA. DefinitionThe fire protection system is designed to reduce the consequences of aneventual fire on board the aircraft, by detecting the fire or smokes at thevery beginning and by locating and neutralizing them as soon as possible.

B. FunctionsThe purpose of the various protection systems is to :- detect and extinguish the fire in each engine nacelle (only area in whichan engine fire may break out)- detect smoke from a fire in cargo compartments- extinguish the fire in the areas which are occupied or may be visitedin flight.- Detect and extinguish automatically the fire in lavatory dust bin.

(Ref. Fig. 001 )(Ref. Fig. 002 )

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(Ref. Fig. 003 )

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(Ref. Fig. 004 )

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C. DescriptionThe main means of protection against the fire are :- the detection systems (Ref. Chapter 26-10)- the extinguishing systems (Ref. Chapter 26-20).

(1) Engine fire detectionThe fire detection is achieved by thermosensing loops which trigger thewarning by means of an electronic control unit in case of temperaturerise in the monitored area.


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NOTE : The engine fire detection system is comprised of two independentloops connected in parallel according to an AND logic, so as toavoid untimely FIRE warnings.

(2) Smoke detection into cargo compartment and lavatoriesThe smoke detection is achieved by smoke detectors which triggerthe warning for a certain amount of smoke, via their integral electronicsystems.

(3) ExtinguishingExtinguishing methods are different according to the area in which thefire breaks out.For each method, one or two fixed fire extinguisher bottles or portablefire extinguishers are used and operated manually.

(a) Fixed fire extinguisher bottlesThey are designed to extinguish any fire breaking out in the enginenacelle and lavatory dust bin.The extinguishing system is supplied :- For each engine nacelle by two fire extinguisher bottles, thepercussion of which is controlled from the flight compartment.- for the dust bin, a fire extinguisher bottle, the percussionof which is automatic. This bottle is located above the dust bin.

(b) Portable fire extinguishersThe flight compartment and cabin extinguishers are of small capacity,manually controlled and enable crew intervention in the area in whichthere has been a fire break out.

D. Testing DevicesThe detection and extinguishing systems may be checked using the corresponding test switches located on the overhead panel.

2. Control and Indicating

A. Engine Fire ControlPanel

(Ref. Fig. 005 )(Ref. Fig. 006 )

B. Smoke Detection Indicating Panel and Test Control(Ref. Fig. 007 )(Ref. Fig. 008 )

3. Electrical Power SupplyCircuit breaker panel (Ref. Chapter 24).

Engine Fire Sensing Elements and Associated Panels - Location

Smoke Detection Location

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Smoke Detection and Fire Extinguishing - Location

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Smoke Detection and Fire Extinguishing - Location


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ENG Fire Handle - Panel - Sheet 1/2

ENG Fire Handle - Panel - Sheet 2/2

Smoke Detection Indicating Panel and Test Control

Indicating Panel of Rear Smoke Detection (70VU)

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Section 26-10 : DETECTION

1. General

A. Engine Fire Detection(1) Location of fire sensing elements and associated panels. (Ref. 26-00).

(2) Operating principle of the engine fire detection.The engine fire detection is achieved by thermosensing loops installedin engine nacelles. When the sensing element warning threshold isreached, the corresponding electronic control unit activates theassociated warning lights.

(3) Engine fire detection electrical power supply.The whole engine fire detection system is supplied from DC Emergencybusbar.

Each detection may be tested individually using the corresponding testswitch.NOTE : The system is identical for each engine.(Ref. Fig. 001 ) .

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B. Smoke Detection in Forward, Aft Cargo Compartments Electronics Rackand Toilets

(1) Location of the smoke detectors and associated panels (Ref. 26-00).(2) Operating principle :The cargo compartment smoke detection is achieved by smoke detectorsinstalled on ceiling panels and by smoke detectors installed onelectronics rack and toilets air extraction ducts.When the warning threshold is reached, the electronic assemblyintegral to each smoke detector activates the appropriate warning light.Each detection loop may be tested individually using a rotative selector.- In forward cargo compartment a pneumatic system provided with two fansinstalled in line, serves to direct the ambiant air towards thedetector (151WA).- In the aft cargo compartment, a similar system is installed serving tosimultaneously monitor the cargo compartment and the lavatories.


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- Air extraction system (aft and fwd cargo compartments) is controlledand monitored by an electronic unit installed in the electronics rack(90VU).

C. Smoke Detection in LavatoriesThe ambient lavatory air is sucked through a smoke detector (184WA) byfans (170 and 172WA) mounted in series.The detector is the photoelectric type :The air extracted from the lavatories is evacuated from the cargo compartment by "VENTURI" effect to the non-pressurized zone of the tail cone, the"VENTURI" inlet is located in the ceiling panel.

D. Smoke Detection in Aft Cargo CompartmentThe ambient cargo compartment airis sucked through a smoke detector (150WA)by fans (170 and 172WA) mounted in series.The detector is of the photoelectric type :The air extracted from the cargo compartment is evacuated by "VENTURI"effect to a non-pressurized zone of the tail cone, the "VENTURI" inletis located in the ceiling panel.

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B. Smoke Detection in Forward, Aft Cargo Compartments, Electronics Rackand Toilets

(1) Location of the smoke detectors and associated panels (Ref. 26-00).(2) Operating principle :The cargo compartment smoke detection is achieved by ambient smokedetectors installed on ceiling panels and by smoke detectors installedon electronics rack and toilets air extraction ducts.When the warning threshold is reached, the electronic assembly integralto each smoke detector activates the appropriate warning lights.Each detection loop may be tested individually using a rotative selector.- In forward cargo compartment a pneumatic system provided with two fansinstalled in line, serves to direct the ambiant air towards the

detector.- In the aft cargo compartment, a similar system is installed serving tosimultaneously monitor the cargo compartment and the lavatories.- Air extraction system (aft and fwd cargo compartments) is controlledand monitored by an electronic unit installed in the electronics rack(90VU).

C. Smoke Detection in Lavatories and Aft Cargo CompartmentThe ambient lavatory air is conducted towards smoke detector (184WA) byfans (170 and 172WA) mounted in series.The detector is of the photoelectric type :The air extracted from the lavatories is evacuated into the cargo compartment where it is sucked by "VENTURI" effect through aft cargo compartmentsmoke detector (150WA), which is an photoelectric type detector, to the

non-pressurized zone of the tail cone.

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(Ref. Fig. 002 ) .(Ref. Fig. 003 ) .

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(Ref. Fig. 004 ) .

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(Ref. Fig. 005 ) .

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Operating Principle of the Engine Fire Detection

Operating Principle of the Cargo Compartment Smoke Detection

Operating Principle of the Electronics Rack Smoke Detection

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Operating Principle of the Smoke Detection in Cargo Compartment and Electronics Rack

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Operating Principle of the Smoke Detection in Cargo Compartment and Electronics Rack

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Section 26-12 : ENGINE FIRE DETECTION

1. GeneralThe engine fire detection system is comprised of two continuous loopsinstalled in parallel and connected to an electronic control unit accordingto an AND logic.A self-monitoring device for the loops enables a loop malfunction to beindicated to the crew members.The detection system is the GRAVINER TRIPLE FD (Fault Free Fire Detection)electrical system with resistance-capacitance variation.For one engine, each loop is comprised of :

- 3 sensing elements connected in series and installed in the enginenacelle- a fire detection control unit installed in the electronics rack 90VU,shelves 93VU (ENG1) and 94VU (ENG2)- a control and indicating assembly located in the flight compartmentoverhead panel (25VU).(Ref. Fig. 001 )(Ref. Fig. 002 )(Ref. Fig. 003 )

2. Description


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A. Sensing ElementThe fire sensing element is a flexible coaxial cable the electricalcharacteristics of which vary with temperature. The cable consists in anouter stainless steel sheath of 1.8 mm (4.6 in.) OD containing a glass basematerial, sensitive to temperature, and a center wire.At each end of the sensing element a sealed connector brazed on the elementenables connection to the electrical harness for aircraft circuit junction.Grooved foolproofing devices at electrical harness-to-element junctionsprevent any cross connection between the loops.(Ref. Fig. 004 )

B. Fire Detection Control UnitThe fire detection control unit processes the warning signals proceedingfrom the sensing element according to an AND logic and triggers thecorresponding indications in the flight compartment (FIRE circuit).Besides, one FAULT circuit per loop, independent of the FIRE circuit,indicates to the crew members any sensing element faulty operation (shortcircuit, contamination of an electrical connector).The face comprises :- two push-to-test lights : LOOP A and LOOP B- a switch with 3 positions, 1, 2 and 3 with automatic return to neutral

(position 2).

C. Control and Indicating AssemblyThe control and indicating assembly is located on the overhead panel andcomprises for each engine :- two LOOP A and LOOP B mechanically latched pushbutton switches withamber FAULT legends and white OFF legends- a selector switch for loop testing- a fire handle with integral ENG1(2) FIRE PULL red warning light.On the CAP :- two ENG1(2) FIRE red warning lights- one LOOP amber warning light(Ref. Fig. 005 )

3. Operation

A. Sensing ElementOperation of the sensing element is based on the variation in resistanceand capacitance of the element. (see Description, paragraph 2).When the sensing element temperature increases, the resistance reduceswhereas the capacitance increases.This capacitance variation is a property of the sensing element innermaterial; it controls the validity of the signal transmitted to the controlunit, since the system operating point is basically determined by thevariation in resistance according to the temperature.As a result, any variation in resistance of the sensing element notaccompanied by a variation in capacitance will activate a FAULT signalindicating a faulty operation of the corresponding loop.The simultaneous variation of both variation/capacitance characteristics is

used for spurious warning rejection.Each loop end is connected to the aircraft network by means of a fireproofwire electrical harness.

B. Fire Detection Control UnitThe control unit is housed in a rectangular aluminum container withremovable lid. Designed to operate with 28VDC, the electrical assemblyconsists of three anti-vibration mounted printed circuit boardsinterconnected by flexible printed wiring (Flexi) with external connectionsmade via a fixed connector on top of the case.


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Two similar circuits are employed for the two separate loops of sensingelements which are designated loop A and loop B. The stabilizer, inverter,thick film circuit and its associated discrete components (with theexception of the regulating transistor which is housed in the removablelid) for loop A are housed on one board. A similar board is used for loopB. The third board houses the relays and their associated discretecomponents for both loops. The lid houses the regulating transistors (to

ensure good heat dissipation), BITE switch and BITE lamps.For the various functions of the control unit :- Indices A and B correspond to loops A and Brespectively.Block 1 : suppression of transients and RF interference to protect semiconductor devices.Block 2 : voltage regulation : the input voltage fed to both the logiccircuits and the static inverter are regulated at 12VDC.Block 3 : static inverter : generation of a 45VAC/400Hz voltage feedingpart of the logic circuits.Block 4 : Fire sensing circuits.The function of the fire sensing circuit is to monitor thecondition of the elements and signal a fire condition. The

element has the ability to store energy when hot. The energy stored being proportional to the element.Fault sensing circuits.Under fault conditions the element is unable to store charge. Tomonitor for fault conditions the voltage across the element ismeasured directly and is proportional to the resistance of thefault.Block 5 : If a fire condition occurs, followed by a fault condition,the fire condition will continue to be indicated. If a fault condition occurs followed by a fire condition then the fire condition will override the fault condition.Block 6 : When a failure is detected the amplifier/comparator output issupplied to the fire warning logic circuits.Block 7 : When the logic circuit output changes to high level, transistorsare activated, which causes the aircraft failure warning circuitto be grounded.Block 8 : A fire warning output causes the BITE lamps to come on and theaircraft failure warning circuit to be triggered.Block 9 : Master fire logicThe relay contacts of two cards are series connected to give amaster fire warning only when loop A and loop B both signal afire warning(Ref. Fig. 006 )

4. Operation of the System and Use of the Controls and Indications

A. FAULT Signal on One LoopThis warning is due to a short circuit or a rapid drop in resistance of onesensing element without increase in capacitance.In case of breaking in one point of the sensing element, fire detection isstill possible; there is no FAULT signal following one single break.However the break will be indicated to the crew at the first pre-flighttest following the fault.In case of double break of one sensing element, each end of the elementconnected to the aircraft electrical harness is still capable of firedetection. In that case too, the fault will be indicated during the preflight test.With the two LOOP A and LOOP B pushbutton switches pressed in flight


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compartment overhead panel, a FAULT signal results in :- illumination of FAULT legend on LOOP A or B pushbutton switch accordingto the faulty loop- illumination of amber LOOP light on the CAP, and master CAUTION lighton Captain main instrument panel.In that case disconnect the faulty loop by selecting OFF on the LOOPpushbutton switch concerned.

In this configuration, the LOOP caution light on the CAP remains on ,alerting the flight crew that one loop is deactivated.Fire detection is provided by the remaining loop.

B. Fire Warning- Each loop of the control unit continuously monitors the appropriateelements for fault condition by directly sampling the average value ofthe rectified voltage across them and comparing with a reference voltage.If this value decreases below the reference voltage the fault warning isgiven.- Fault inhibit circuit.When a fire warning occurs on either loop the fault indication for thatloop is inhibited. If a fault condition occurs on the loop prior to thesystem resetting, the fire indication will remain, even if the element

temperature falls below the system reset level.C. Loop TestWith the two LOOP A and LOOP B pushbutton switches pressed in, and :

(1) TEST switch in FAULT

position :triggering of LOOP A and B FAULT signals.Consequences : - FAULT amber legends on LOOP A and LOOP B pushbuttonswitches come on- LOOP caution light on CAP comes on together with masterCAUTION light on Captain main instrument panel- the single chime sounds

(2) TEST switch in FIRE position :triggering of LOOP A and B FIRE signals.Consequences : - ENG1(2) FIRE PULL light on fire handle comes on- ENG1(2) FIRE warning light on CAP comes on together withmaster WARNING light on Captain main instrument panel- the repetitive chime sounds- FUEL SOV warning light on condition lever comes on.

D. Maintenance Test (Bite System)NOTE : Built-in test equipment indications are not relevant unless theflight compartment test confirms a fault condition exists.To assist in the rapid isolation of faults, the control unit incorporates a3 position BITE switch and 2 BITE lamps for use during ground checking.This switch is biased to position 2.When a loop is diagnosed as faulty the BITE switch allows rapididentification of the fault to either the control unit or sensing element

assemblies.When a fault is reported, the BITE lamp should be observed. If it is noton it should be checked for serviceability by using the "press to test"facility incorporated in the lamp holder.Provided the lamp is serviceable, not on and the loop reportedunserviceable, the BITE switch should be placed in position 3. If the BITElamp remains off a faulty control unit is indicated. If the BITE lamp comeson, an open circuit in the sensing element assemblies is indicated.If the BITE lamp is on and the loop reported unserviceable, the BITE switch


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should be placed in position 1. If the BITE lamp remains on a faultycontrol unit is indicated. If the BITE lamp is off a short circuit in thesensing element assemblies is indicated.When the BITE switch is in position 1 the sensing element assemblies aredisconnected from the monitoring circuits. In position 3 the sensingelement assemblies are disconnected from the monitoring circuits andeffectively replaced by a capacitor and resistor in series for each

Text continues: see text below

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loop of the control unit to monitor.

Engine Fire Sensing Elements - Location

Engine Fire Sensing Elements - Connecting Principle

Fire Detection Control Units - Location

Typical Rail Mounted Element Assembly

Control and Indicating Circuit - Schematic

Fire Detection Control Unit - Block Diagram

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Section 26-15 : SMOKE DETECTION

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1. General

The smoke detection system is comprised of four smoke detectors :- one detector on toilets air extraction duct (1),- one detector in aft compartment (2),- one detector in the forward compartment,- one detector in electronics rack air extraction system.Smoke detectors in forward, in aft compartments and in toilets are of thephotoelectric cell type.Smoke detector on electrics rack air extraction ducts is of the ionizationtype.The air extraction through the smoke detectors in aft cargo and toilets, is


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performed by means two fans.

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1. GeneralThe smoke detection system is comprised of four smoke detectors :

- one detector in toilets and aft passenger compartment air extractionsystem (1),- one detector in aft cargo compartment (2),- one detector in forward cargo compartment and forward passenger compartmentair extraction system (3)- one detector in electronics rack air extraction system.Smoke detector in forward, smoke detector in aft cargo compartments and intoilets are of the photoelectric cell type.Smoke detector on electronics rack air extraction duct is of the ionizationtype.Forward cargo compartment smoke detector and toilets smoke detector are eachequipped with two air extraction fans.The smoke detector in aft cargo compartment is connected to a venturi

plug located on pressure bulkhead.A smoke detector restrictor has been installed at lavatory partitionfeed-thru in order to balance the flow between the lavatory system and thecargo compartment system.

A. "Containers carrier" configuration : the aft and forward shutoff manualvalves (4) and (5) must be in "OPEN" position.

B. "Passengers" configuration : the aft and forward shutoff manual valves (4)and (5) must be in "CLOSED" position.

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(Ref. Fig. 001 )

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(Ref. Fig. 002 )

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2. Description of Smoke DetectorsA. Photoelectric cell smoke detectorsThe smoke detector casing comprises :- 1 photoelectric cell,- 1 projecteur lamp (light source),- 1 testing lamp,

- 1 port,- 1 sens- 1 amplifier.(Ref. Fig. 003 )

B. Ionization Smoke DetectorThe smoke detector casing comprises :- 1 measuring chamber with a perforated housing enabling passage of theair inside the cell,- 1 High Impedance Resistor,


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- 1 electronic circuit,- 1 automatic temperature compensation circuit associated with a thermometric sensor enabling test to be performed.(Ref. Fig. 004 )

3. Operating Principle of Smoke Detection System- Smoke Detection in Cargo Compartments and Electronics Rack.Each detector is supplied separately with 28VDC. Ambient air flowsthrough the detectors. If smoke is detected, an output signal istransmitted to the CCAS which triggers the following warnings :. aural warning (repetitive chime),. warning corresponding to detection on crew alerting panel. warning lights on panel 3VU and 5VU. warning corresponding to detection on panel 70VU.The CCAS selector switch 137WW (101VU) in smoke position serves totest the detection circuitry through relay 151WW.(Ref. Fig. 005 )(Ref. Fig. 006 )

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- Air extraction from forward cargo compartment towards smoke detector

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1. ERREUR!! MANQUE TITRE

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(1) DescriptionForward cargo compartment ambient air goes through smoke detector151WA via two fans operating alternatively and installed on detectionduct.

(2) Operation of fans in "CARGO" configuration :The "SMK DET" switch 201WA located on panel 101VU, is in "CARGO CONFIG"position.The fans are operating.Air from the forward cargo compartment circulates in the smoke detectorsealed casing. The fan control unit, supplied by circuit breakers 156WAand 158WA, controls alternate operation of the air extraction fans155WA and 157WA.This alternate operation is controlled by a "flip-flop" relay whichoperates the fan not in service previously, after each systemenergization. This function is automatic when there is intensityvariation.If the fan in service fails, FAULT light 162WA comes on on panel 34VU

as also the following warnings :- CAUTION- AIRThe single chime sounds.By pressing and releasing concerned pushbutton switch (34VU),the crew forces operation of the other fan (ALTN light on).

(3) Fans operating in "PASSENGERS" configuration : The fans of forwardcargo

compartment are inhibited when the "SMK DET" switch 201WA is placed


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in the "PAX CONFIG" located on panel 101VU. The detection is carriedout by convection.When the fans of forward cargo compartment are inhibited, no warning istriggered.

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- Circulation of toilets and AFT cargo compartment air ambient towards smokedetectors

(1) Description. toilets air ambient circulates through smoke detector 184WA.. AFT cargo compartment air ambient circulates through smoke detector150WA.To operate this circulation, two fans (170WA and 172WA) installed inseries on extraction duct, operate in alternation.Air ambient is drawn by venturi effect towards the AFT non pressurizedcompartment.

(2) Operation of fansAir from the lavatory circulates in the smoke detector sealed casing

184WA. Air from the aft cargo compartment circulates in the smokedetector sealed casing 150WA.The fan control unit supplied by circuit breakers 154WA and 166WAcontrols alternate operation of the air extraction fans 170WA and172WA.This alternate operation is controlled by a "flip-flop" relay whichoperates the fan not in service previously, after each systemenergization. This function is automatic when there is intensityvariation.If the fan in service fails, FAULT light 164WA comes on on panel 34VUas also the following warnings :- CAUTION- AIRThe single chime sounds.

By pressing and releasing concerned pushbutton switch (34VU),the crew forces operation of the other fan (ALTN light on).

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(Ref. Fig. 007 )

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(Ref. Fig. 008 )

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4. Operating Principle of Detectors

A. Operating Principle of Photoelectric Cell Smoke DetectorA projector consisting of a lamp and a lens sends a cylindrical light beamthrough a sensing chamber. A photoresistive cell is fitted on the chamberalong an axis perpendicular to the light beam. When the air is free ofsmoke, no light reaches the photoresistive cell.As soon as smoke penetrates into the sensing chamber, it influences thelight beam which deflects and diffuses it. Thus a conical refraction is


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produced and photoresistive cell is reached by light.As long as there is smoke in the sensing chamber, smoke diffracts the lightand photoresistive cell kept the warning light on.(Ref. Fig. 003 )

B. Operating Principle of the Ionization Smoke DetectorIn the measuring chamber, an electrical field is created between electrodesE1 et E2 by means of a power supply.The air between the electrodes is ionized by means of a radio-activesource.The ions (negatively or positively charged gas molecules) move toward thecorresponding electrode with a speed relative to molecule width andelectrical field intensity.When particles in suspension, resulting of fire, penetrate in the measuringchamber, the ions which associate with the particles become heavy (to 1000times heavier). Their displacement speed is reduced which decrease theionization current and then increase the electrical resistor of themeasuring chamber. The voltage between the measuring chamber terminalsbecomes upper to the voltage of high impedance resistor. The electroniccircuit measures this unbalance by means threshold circuit. When the presetthreshold is reached, the circuit generates a warning signal.

(Ref. Fig. 004 )

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Aft Cargo Compartment and Toilets Smoke Detection Installation Diagram

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Photoelectric Cell Smoke Detector.

Operating Principle of the Detection Cell.

Forward and Aft Cargo Compartment Smoke Detection Power Supply - Schematic

Electronics Rack Smoke Detection Power Supply - Schematic.

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Air Extraction Fan Power Supply - Schematic

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Section 26-15 : SMOKE DETECTION

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1. GeneralThe smoke detection system is comprised of four smoke detectors :- one detector on toilets air extraction duct (1),- one detector in aft compartment (2),- one detector in the forward compartment,- one detector in electronics rack air extraction system.

Smoke detectors in forward, in aft compartments and in toilets are of thephotoelectric cell type.Smoke detector on electrics rack air extraction ducts is of the ionizationtype.The air extraction through the smoke detectors in aft cargo and toilets, isperformed by means two fans.

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1. GeneralThe smoke detection system is comprised of four smoke detectors :- one detector in toilets and aft passenger compartment air extractionsystem (1),

- one detector in aft cargo compartment (2),- one detector in forward cargo compartment and forward passenger compartmentair extraction system (3)- one detector in electronics rack air extraction system.Smoke detector in forward, smoke detector in aft cargo compartments and intoilets are of the photoelectric cell type.Smoke detector on electronics rack air extraction duct is of the ionizationtype.Forward cargo compartment smoke detector and toilets smoke detector are eachequipped with two air extraction fans.The smoke detector in aft cargo compartment is connected to a venturiplug located on pressure bulkhead.A smoke detector restrictor has been installed at lavatory partitionfeed-thru in order to balance the flow between the lavatory system and thecargo compartment system.

A. "Containers carrier" configuration : the aft and forward shutoff manualvalves (4) and (5) must be in "OPEN" position.

B. "Passengers" configuration : the aft and forward shutoff manual valves (4)and (5) must be in "CLOSED" position.

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(Ref. Fig. 001 )

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(Ref. Fig. 002 )

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2. Description of Smoke Detectors

A. Photoelectric cell smoke detectorsThe smoke detector casing comprises :- 1 photoelectric cell,- 1 projecteur lamp (light source),- 1 testing lamp,- 1 port,- 1 sens- 1 amplifier.(Ref. Fig. 003 )

B. Ionization Smoke DetectorThe smoke detector casing comprises :- 1 measuring chamber with a perforated housing enabling passage of theair inside the cell,- 1 High Impedance Resistor,- 1 electronic circuit,- 1 automatic temperature compensation circuit associated with a thermometric sensor enabling test to be performed.(Ref. Fig. 004 )

3. Operating Principle of Smoke Detection System- Smoke Detection in Cargo Compartments and Electronics Rack.Each detector is supplied separately with 28VDC. Ambient air flowsthrough the detectors. If smoke is detected, an output signal istransmitted to the CCAS which triggers the following warnings :

. aural warning (repetitive chime),

. warning corresponding to detection on crew alerting panel

. warning lights on panel 3VU and 5VU

. warning corresponding to detection on panel 70VU.The CCAS selector switch 137WW (101VU) in smoke position serves to

test the detection circuitry through relay 151WW.(Ref. Fig. 005 )(Ref. Fig. 006 )

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- Air extraction from forward cargo compartment towards smoke detector

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1. ERREUR!! MANQUE TITRE

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(1) DescriptionForward cargo compartment ambient air goes through smoke detector


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151WA via two fans operating alternatively and installed on detectionduct.

(2) Operation of fans in "CARGO" configuration :The "SMK DET" switch 201WA located on panel 101VU, is in "CARGO CONFIG"position.The fans are operating.Air from the forward cargo compartment circulates in the smoke detectorsealed casing. The fan control unit, supplied by circuit breakers 156WAand 158WA, controls alternate operation of the air extraction fans155WA and 157WA.This alternate operation is controlled by a "flip-flop" relay whichoperates the fan not in service previously, after each systemenergization. This function is automatic when there is intensityvariation.If the fan in service fails, FAULT light 162WA comes on on panel 34VUas also the following warnings :- CAUTION- AIRThe single chime sounds.By pressing and releasing concerned pushbutton switch (34VU),

the crew forces operation of the other fan (ALTN light on).(3) Fans operating in "PASSENGERS" configuration : The fans of forward

cargocompartment are inhibited when the "SMK DET" switch 201WA is placedin the "PAX CONFIG" located on panel 101VU. The detection is carriedout by convection.When the fans of forward cargo compartment are inhibited, no warning istriggered.

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- Circulation of toilets and AFT cargo compartment air ambient towards smokedetectors

(1) Description. toilets air ambient circulates through smoke detector 184WA.. AFT cargo compartment air ambient circulates through smoke detector150WA.To operate this circulation, two fans (170WA and 172WA) installed inseries on extraction duct, operate in alternation.Air ambient is drawn by venturi effect towards the AFT non pressurizedcompartment.

(2) Operation of fansAir from the lavatory circulates in the smoke detector sealed casing184WA. Air from the aft cargo compartment circulates in the smokedetector sealed casing 150WA.The fan control unit supplied by circuit breakers 154WA and 166WAcontrols alternate operation of the air extraction fans 170WA and172WA.This alternate operation is controlled by a "flip-flop" relay whichoperates the fan not in service previously, after each systemenergization. This function is automatic when there is intensityvariation.If the fan in service fails, FAULT light 164WA comes on on panel 34VUas also the following warnings :- CAUTION


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- AIRThe single chime sounds.By pressing and releasing concerned pushbutton switch (34VU),the crew forces operation of the other fan (ALTN light on).

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(Ref. Fig. 007 )

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(Ref. Fig. 008 )

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4. Operating Principle of Detectors

A. Operating Principle of Photoelectric Cell Smoke DetectorA projector consisting of a lamp and a lens sends a cylindrical light beam

through a sensing chamber. A photoresistive cell is fitted on the chamberalong an axis perpendicular to the light beam. When the air is free ofsmoke, no light reaches the photoresistive cell.As soon as smoke penetrates into the sensing chamber, it influences thelight beam which deflects and diffuses it. Thus a conical refraction isproduced and photoresistive cell is reached by light.As long as there is smoke in the sensing chamber, smoke diffracts the lightand photoresistive cell kept the warning light on.(Ref. Fig. 003 )

B. Operating Principle of the Ionization Smoke DetectorIn the measuring chamber, an electrical field is created between electrodesE1 et E2 by means of a power supply.The air between the electrodes is ionized by means of a radio-activesource.The ions (negatively or positively charged gas molecules) move toward thecorresponding electrode with a speed relative to molecule width andelectrical field intensity.When particles in suspension, resulting of fire, penetrate in the measuringchamber, the ions which associate with the particles become heavy (to 1000times heavier). Their displacement speed is reduced which decrease theionization current and then increase the electrical resistor of themeasuring chamber. The voltage between the measuring chamber terminalsbecomes upper to the voltage of high impedance resistor. The electroniccircuit measures this unbalance by means threshold circuit. When the presetthreshold is reached, the circuit generates a warning signal.(Ref. Fig. 004 )

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Photoelectric Cell Smoke Detector.

Operating Principle of the Detection Cell.

Forward and Aft Cargo Compartment Smoke Detection Power Supply - Schematic

Electronics Rack Smoke Detection Power Supply - Schematic.

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Section 26-16 : NACELLE OVERHEAT DETECTION1. GeneralNacelle overheat is detected by a sensor overheat which sent an informationto the Engine Overheat Detection Control Unit. This sensor is located inright nacelle below exhaust nozzle and before the exhaust duct lips.

2. OperatingWhen the right nacelle temperature reaches 170 5, NAC OVHT light locatedon Crew Alerting Panel (CAP) comes on.(Ref. Fig. 001 )

Operating Principle of Nacelle Overheat Detection

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Section 26-20 : EXTINGUISHING


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1. General

A. Engine Fire ExtinguishingTwo fixed fire extinguisher bottles are installed in the wing-to-fuselagejunction fillet, on either side of the fuselage, and are used to extinguishfires in the engine zones.Two percussion panels located on the overhead panel enable control of the

fire extinguishing agent discharge on the engine concerned.(Ref. Fig. 001 )

B. Portable Fire ExtinguishersOne portable fire extinguisher located in the flight compartment and otherslocated in passenger compartment are used to extinguish any fire breakingout in the occupied zones.

C. Extinguishing System Electrical Power SupplyThe engine fire extinguisher bottle percussion system is supplied with28VDC from hot main bat busbar and emergency busbar.

Engine Fire Extinguishing Bottles and Associated Panels - Location

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Section 26-21 : ENGINE FIRE EXTINGUISHING

1. GeneralA fire extinguishing system is installed on each engine.The extinguishing agent CF3 Br, is stored into two sealed bottles.The extinguishing procedure is initiated manually from the flight compartmentoverhead panel as soon as ENG1 (ENG2) FIRE warning is triggered.

The engine fire extinguisher bottles are Walter Kidde bottles.Each bottle has two discharge heads.Two two-way check valves enable the extinguishing agent to be directed towardthe engine concerned.(Ref. Fig. 001 )

2. Description

A. Fire Extinguisher Bottle and Associated ComponentsThe two bottles are spherical and of the quick-discharge type.Each bottle has a volume of 3670 cm3 (223,7 inch3) and can contain2.95 kg (6.5 lbs) of monobromotrifluoromethane (CF3 Br) pressurized bynitrogen at 41 bars (600 psi) at a temperature of 21C.Each bottle has two discharge heads enabling the fire extinguishingagent to be routed toward one or the other engine.

Each discharge head is blanked by a beryllium bronze diaphragm.Sealing is provided by a gasket.The diaphragm is broken by the percussion of a pyrotechnic cartridgeelectrically fired by two resistances (0.04 to 0.2 ohms) (in case offailure of one resistance, the percussion can still be obtained with theremaining operational resistance).A pressure relief valve is located at the lower point of the bottle,between the two discharge heads. The valve is comprised of a diaphragmwhich breaks when the pressure inside the bottle reaches between 95.6 bars(1400 psig) and 123 bars (1800 psig), thus enabling a complete discharge of


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the extinguishant into the compartment.The valve can also be used for bottle filling.A pressure switch is installed on each bottle to enable checking of thebottle inner pressure. It causes illumination of DISCH warning lights (oneper bottle each time the pressure inside the bottle drops below 15 bars(225 psig).A pressure gage displays the pressure inside the bottle.

(Ref. Fig. 002 )(Ref. Fig. 003 )

B. Fire Extinguishing Lines and Associated Components

(1) Fire extinguishing lineThe fire extinguishing lines are rigid light alloy diameter lines routedalong the aft wing spar, from the fillets to the engine.In the nacelle (fire zone and area adjacent to the fire zone) theselines are in stainless steel and distribute the fire extinguishing agentdirectly into the fire zone.Two cross-feed lines routed inside the wing-to-fuselage junction fillet,above the fuselage, enable the extinguishant to be directed toward theengine concerned by means of two two-way valves.On the lower points of the lines are installed four water drains :

- two water drains at the two-way valves- two water drains directly on the lines. The left water drain supportis slightly shifted. This is a mechanical foolproofing preventingany fire extinguishing line inversion.(Ref. Fig. 004 )

(2) Two-way check valvesThe purpose of the two-way check valves is to direct the extinguishanttoward the engine concerned and to prevent the extinguishant released bythe second percussion from filling the bottle emptied by the firstpercussion. The two-way check valve has a light alloy valve which isoperated and opens according to the pressure the extinguishant exerts onit.A water drain is located at the two-way check valve lower point.

The water drain has an aluminium valve which in absence of pressure isspring loaded open.With the pressure due to the extinguishing agent, the valve closes thewater drain.

(3) Water drainTwo water drains are installed at the lower points of the cross-feedlines. Their operation is the same as that of the two-way check valvewater drains.(Ref. Fig. 005 )

C. Controls and IndicationsThere is a control and indicating panel corresponding to each engine.The panels are located on the overhead panel.Each panel is comprised of :

- 2 pushbutton switches : AGENT 1 and AGENT 2- each pushbutton switch has two legends :. 1 SQUIB white legend. 1 DISCH amber legend. 1 SQUIB TEST switch enabling electrical continuity of the percussionresistances to be checked.(Ref. Fig. 006 )

3. Utilization and Operation

A. Fire Extinguishing Procedure


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In case of engine fire detection (Ref. 26-12) the following procedure mustbe applied :- place the power lever in Idle position- place the condition lever in OFF position(FUEL SOV red light on condition lever goes off).- pull fire handle. This has for effect to :. close the LP fuel shut off valve

. close the air bleed valve

. close pressure regulating and shut off valve

. close de-icing shut off valve

. de-energize the AC and DC generators

. enable percussion of the fire extinguisher bottles (the correspondingSQUIB legend comes on).- squib the first bottle, by pressing AGENT 1 pushbutton switch (dischargeof the bottle is indicated by the illumination of amber DISCH legend).If the FIRE warning does not disappear within the 30 following seconds, thesecond bottle must be squibbed.

B. Test of the Percussion Cartridges- press SQUIB TEST pushbutton switch :The two SQUIB legends of AGENT 1 and AGENT 2 pushbutton switches come on.

NOTE : Although only one resistance is sufficient to squib the bottle, thetest result is positive if both resistances are in correctcondition.The intensity of the test current is limited to 1A because of the testtransistor.The intensity of the percussion current is higher than 3A.

C. Check of the Fire Extinguisher Bottle Pressure and Weight :- the pressure gage pointer must be in the green range,- During fire extinguisher bottle removal, check that its weightcorresponds to the weight noted on the placard.(Ref. Fig. 007 )

Engine Fire Extinguishing System

Engine Fire Extinguisher Bottle

Percussion Cartridge and Pressure Switch

Fire Extinguishing Lines and Associated Components

Two-way Check Valves and Water Drains

Engine Fire Extinguishing Controls and Indications

Engine 1 (2) Fire Protection System - Electrical Circuit

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Section 26-24 : PORTABLE FIRE EXTINGUISHER


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1. GeneralPortable fire extinguishers installation consists of :- 1 halon extinguisher in the cockpit,- 1 Water extinguisher and 1 Halon extinguisher in the cabin.(Ref. Fig. 001 )

2. Description

The portable fire extinguishers are installed by means of quick fasteners.The extinguishers are :- Halon type with a manometer indicating the pressure of the nitrogencartridge.Certain Halon type extinguisher are equipped with a flexible duct.Each bottle contains Halon 1211 (CF2 CL Br) pressurized with nitrogen.- Water type without manometer.A placard on each extinguisher gives the instructions for use, manufacturingdate, expiration date and weight of the bottle.

3. UtilizationThe portable fire extinguisher is operated by removing the safety pin andpressing the handle, which has for effect to open the valve and spray theextinguishing agent.Spraying may be interrupted by pulling up the handle and installing thesafety pin until the next use.For the Halon extinguishers, the pressure gage indicates the quantity ofagent left into the bottle.If the pointer is in the red range, the bottle must be changed.NOTE : Whenever possible, inform the appropriate service when an extinguisherhas been used, so that an inspection can be carried out.

4. Aft Cargo Compartment Fire Extinguishing SystemThis fire extinguishing system, located on the ceiling of the aft cargocompartment includes two diffusers.This system serves to diffuse the extinguishing in the entire cargocompartment when loaded to the maximum.The aft cargo compartment fire extinguishing procedure consists in connectingportable fire extinguisher discharge orifice to system orifice located above

cabin attendant seat and to discharge extinguisher agent.If cargo loading permits, direct fire extinguishing may be carried out.

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Section 26-25 : LAVATORY FIRE EXTINGUISHING

1. GeneralIn case of fire in the lavatory dustbin, a halon fire extinguisher isinstalled above the bin.

The fire extinguisher is activated automatically when a heat source inthe region of 170F (77C) is detected. The extinguishing agent isdischarged into the dustbin via two tubes equipped with a valve at the end.(Ref. Fig. 001 )

Documents

ch-26; fire protection