Lecture Notes Fire Protection Systems

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UNIT 4 AUXILLARY SYSTEMS

SYLLABUS:

4. AUXILIARY SYSTEM 8

Basic Air cycle systems - Vapour Cycle systems, Evaporative vapour cycle systems -Evaporative air cycle systems - Fire protection systems, De-icing and anti icing systems.

Introduction: The majority o the modern aircra t, primarily the large transport type, aree!uipped "ith certain systems that are not necessary or the actual operation and light o theaircra t and convenience o the cre" and passengers and may #e re!uired #y Federal

Aviation $egulations %FA$s& 'ome o these systems are important or the sa e operation o the aircra t under a variety o conditions, and some are designed to provide or emergencies.

'ystems not essential to the actual operation o the aircra t are commonly called as Au(iliary systems. Among such systems are

). Fire *rotection system or Fire "arning and Fire E(tinguishing systems+. ce and $ain *rotection system

. (ygen system/. 0ater and "aste system1. Ca#in Air pressuri2ation system or ca#in air conditioning system3. *osition and 0arning system4. Au(iliary *o"er system

FIRE PROTECTION SYSTEM:

Fire protection system on aircra t usually consists o t"o separate operating systems"ith associated controls and indicators. ne system is or ire or over heat detection and theother is or ire suppression or e(tinguishing. n some cases the system can #e

interconnected so e(tinguishing ta5es place automatically "hen a ire is detected.To detect ires or overheat conditions detectors are placed in the various 2ones to #emonitored. Fires are detected in reciprocating engine aircra t using one or more o the

ollo"ing6). ver heat detectors+. $ate o temperature rise detectors

. Flame detectors/. #servation #y cre" mem#ers1. Car#on mono(ide detectors

Detection Met od!:The ollo"ing list o detection methods includes those most commonly used in tur#ine

aircra t ire protection systems. The complete aircra t ire protection system o most largetur#ine engine aircra t "ill incorporate several o these di erent detection methods.

). $ate o temperature rise detectors+. $adiation sensing detectors

. ver heat detectors/. Car#on mono(ide detectors1. 'mo5e detectors3. #servation #y cre" mem#ers4. Fi#re optic detectors7. Com#ustion 8i(ture detectors


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rapid release of the hydrogen gas from the wire when the temperature reaches the requiredlevel.

The sensor responds in accordance with the law of gases. If the volume of gas is heldconstant, its pressure will increase as temperature increases. The helium gas in the tube e ertsa pressure proportional to the average temperature along the entire length of the tube. This is

the averaging, or overheat, function of the sensor. If the average temperature e ceeds aspecified level, the helium gas pressure will be such that it closes the pneumatic switch in theresponder and signals an over heat condition. If there is a very high temperature as a firewould cause anywhere along the sensing element, the centre wire in the tube will release alarge quantity of hydrogen gas. This will increase the total gas pressure in the tube to a levelthat will close the pneumatic switch. This is called the discrete function of the sensor.

!hen the fire is e tinguished and the temperature begins to drop the specially processed titanium wire in the tube will reabsorb the hydrogen gas and reduce the pressure inthe tube. This will cause the pneumatic switch to open and the system will be bac" to normaland ready to provide another signal in case of re-ignition.

The responder contains two identical diaphragm switches. #ne of the switches isnormally open and closes only when gas pressure in the sensor tube increases owing to hightemperature or fire in the area where the sensor is installed. The other switch is held closed bythe normal helium pressure in the sensor tube. If the helium pressure should be lost, theswitch opens the test circuit.


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T"#e! o$ !%o&e detector!

'. C(r)on %ono*ide detector!+. P otoe,ectric S%o&e detector!-. i!u(, !%o&e detector!

4. Ioni/(tion !%o&e detector!


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Exting i!"ing F n#$ment$%!$ire e tinguishing includes that part of the fire protection system using fi ed or portablesystems used to e tinguish a fire %&T& '((). & fire classification includes three types of firerelevant to aircraft application*+ lass &* $ires involving ordinary combustible solid materials, such as wood, paper, rubber,and many plastics+ lass * $ires involving flammable liquids, oils, greases, paints, lacquers andflammable gases+ lass * $ires involving energized electrical equipment ach of these types of fire requiresits own suitable type of e tinguisher*+ !ater e tinguishers are used on lass & fires only. !ater must never be used on

lass fires and can be counterproductive on lass fires.+ #/ e tinguishers are specifically used to combat lass fires. & hand-held #/e tinguisher includes a megaphone-shaped nozzle that permits discharge of the

#/ close to the fire. e aware that e cessive use of #/ e tinguishers robs aclosed area of o ygen. In an aircraft, this could affect passengers.+ 0ry chemical fire e tinguishers can be used on lass &, , or fires. Use of such ane tinguisher on the flight dec" could lead to temporary severe visibility restrictions. Inaddition, because the agent is nonconductive, it may interfere with electrical contacts of surrounding equipment.+ 1alon has almost e clusively been in use in portable aircraft fire e tinguishers.

Engine $n# APU Exting i!"ing$irst step* The engine is shut down and combustible fluid entry % 2et fuel, hydraulic fluid, andengine oil) into the engine compartment is stopped. This is necessary for the enginee tinguisher to be effective. If the engine were not shut off, the fire would probably 2ust

relight after the e tinguishing agent dissipated. ecause of this practice, only multiengineaircraft utilize e tinguishing systems.3econd step* The e tinguishing agent flows from a pressure vessel through rigid pipes and issprayed in the engine-protected zones.Third step* If after some time %4( s) the fire warning still remains on, e tinguishingagent from a second pressure vessel %if still available for that engine)may be used for further fire e tinguishing.

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Lecture Notes Fire Protection Systems