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PIPERAIRCRAFT
PA-42-720(Advanced Trainer)
MAINTENANCEMANUAL

CHAPTER 26
LIST OF EFFECTIVE PAGES
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PIPERAIRCRAFT
PA-42-720(AdvancedTrainer)
MAINTENANCEMANUAL

CHAPTER26-FIRE PROTECTION
TABLEOFCONTENTS
PAGE

SUBJECT CHAPTER
26-10-00
1General 1Detection

1

Descriptionand Operation
26-20-00
1

Extinguishing
1

DescriptionandOperation Removalof Fire ExtinguisherBottle 2 Installationof Fire Extinguisher 3
3

ServicingFire Extinguisher Bottle ReplacingFireExtinguisherSquib Assembly 3
4Testing Extinguishing System 5Portable Fire Extinguisher

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CONTENTS

PIPERAIRCRAFT PA-42-720(AdvancedTrainer) MAINTENANCEMANUAL 
Fire Protection 
A. General 

A fire detection and extinguishingsystemis providedfor eachengine;bothare completely independentfrom the other. Duringan enginecompartmentfire,thermaldetectorsinstalledin the enginecompartmentactuateandcompletean electrical circuitthat illuminatesthe mastercaution warninglight,soundsa warning horn,and illuminatesthe appropriateenginefire warning lighton the
annunciatordisplay. Eachsystemhasa switch locatedon the lowerleftsideof the instrumentpanel
which electricallydischargesthefire extinguishingagentthroughtubesintoappropriateengine
compartmentareas.
B. Detection
1. DescriptionandOperation
Eachenginefire detectionsystemconsistsof threefire detectingthermalunitsand interconnecting harness.Twoof theseunitsare locatedon eachsideof the frontfire seal inthe hot section. One is locatedat the bottom of the rear fire sealin the accessorysection.The thermalunitsactuateat a temperatureof 450°F. Whenevercontactsin one of the thermalunitsis actuated(dueto a fire condition),the circuitis completedandcausesa mastercautionlightto blink,a horn to blow,and
the enginefire warning lightto illuminate on the annunciator display. The hornand flashinglight can be deactivated by pressingthe mastercautionlight.
harnesses series,and it completesa circuit fromannunciatordisplaytogroundwhichcheckscontinuityof systemand operation of leftandrightenginefirewarninglightsonannunciator.
Whentestswitchispressed,it connects interconnecting of each enginesystemin
EngineFireDetectors
Figure1

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PIPERAIRCRAFT
PA-42-720 (Advanced Trainer)
MAINTENANCE MANUAL

A. Extinguishing
1. Description and Operation
Eachengine fire extinguishing system consists of a spherical container (bottle) storing a fire
extinguishingagent(Halon 1301) chargedto 360 +25 -0 psig at 70°F with dry nitrogen. A pressure
gauge mounted on the side of the bottle indicates the internal (charged) pressure. Each bottle is
mountedon the right side of each rear fire seal in the accessory sectionof the engine nacelles. A
main discharge pipe extends from a valve on the bottom of the bottle forward through rear and
frontfire seals to the hot section of the engine. An additional tube extends from the main
dischargepipe, passes aft through the rear fire seal,and terminatesat the top of the engine
accessorysection.
An electrically operated cartridge (firing squib), screwed into the discharge valve at the base of the
bottle, provides a release for the extinguishingagent. When the switch in the cockpit is actuated,
the firing squib in the discharge valve is detonated and punctures the seal in the discharge valve
that allows the release of extinguishing agentthrough pipes. The container (bottle) also has a
combinationfill fitting and safety relief valve assembly. If ambient temperaturerises abnormally
(215°Fto 226°F), a fusible check valve within the fill fitting melts, relievingcontents of container
(bottle) and avoiding possible bursting of container.
EngineFire Control System Figure 2

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PIPER AIRCRAFT
PA-42-720(AdvancedTrainer)
MAINTENANCEMANUAL

A. Extinguishing (continued)
2. Removal of Fire Extinguisher
Bottle
(a)
Ensure aircraft masterswitchis off and fire extinguisher circuitbreakeris disengaged.

(b)
Removeupper and lower engine cowling.

WARNING: FROSTBITEOR LOW TEMPERATURE BURNSWILL RESULT IF HALON 1301 (BAROMOTRIFLUOROMETHANE
　
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