Fire Week 6

what is required for combustion

fuel, oxygen and heat

types of fire extinguishing agents

carbon dioxide

halon (halongenated hydrocarbons)

dry powder

carbon dioxide is used on what type of fires

Class B and C

carbon dioxide isnt effective on what type of fires

fires involving chemicals containing their own oxygen supply

magnesium and titanium

where is carbon dioxide agent used

on the ramp to fight fires on exterior or aircraft

how does carbon dioxide agent work

1.5x heavier than air

dilutes the air and reduces oxygen content so combustion cannot continue

what happens when carbon dioxide agent is discharged

liquid expands to gas > becomes finely divided white solid, dry ice snow

why is halon bad

ozone depleting and global warming chemical

aviation use is an exception

why is halon good

no residue

electrically nonconducting

low toxicity

what type of fires is halon used on

class A, B or C

what type of fires cannot use halon

class D

dry powder is used on what type of fire

class A, B or C

what is dry powder agent made of

ammonium phosphate

why dont we use dry powder

residue and big clean up

water is used on what type of fire

class A

cools material below its ignition temperature and soaks the material to prevent re-ignition

where must portable fire extinguishers be located

• Must be at least one handheld portable fire extinguisher for use in the pilot compartment located within easy access of the pilot when seated

• Must be at least one handheld fire extinguisher located in passenger compartment

servicing portable fire extinguishers

must be inspected every year for security, damage, gauge pressure and weight

may need to be hydrostatically tested

maintenance requirements are in the carrier’s individual operating specs

types of fixed fire extinguishing systems

conventional system

high rate of discharge (HRD)

conventional fire extinguishing system uses what type of agent

uses carbon dioxide

conventional fire extinguishing systems consists of

stainless steel cylinder wrapped in steel wire containing CO2 at 700-1000 psi

how to operate conventional fire extinguisher

remotely controlled valve to distribute agent

HRD uses what type of agent

halon

HRD is used where

engine fire and cargo

HRD consists of

stainless steel spherical container

lightweight

what is the temperature/pressure sensitive fusible safety plug on HRD

prevents container pressure from exceeding container test pressure when exposed to excessive temperatures

HRD containers have 2 parts

bonnet assembly or operating head, and fusible safety plug

how long does it take HRD to distribute agent

1-2 seconds

HRD bonnet system

contains discharge cartridge/squib that fires a projectile into a disk that holds back the agent

disk breaks > pressurized nitrogen in the container forces the agent out > strainer to prevent disk fragments from getting into the agent

how do we control the squib

switch in the flight deck

press switch > voltage sent to discharge cartridge and fires it > agent disperses

two shot system requirements

• Commuter aircraft must have a one-shot fire extinguishing system (at a minimum)

• All transport category aircraft under Std 525 must have a two-shot fire extinguishing system

why are two-way check valves required in two-shot system

prevents agents in the reserve container from backing up into the previous emptied main container

squib service life

life-limited

service life is calculated from the manufacturer’s date

average service life - 5000 hours or 5 years

safety precautions with working with squibs

static electricity or using multimeter can detonate cartrdige

test while it’s installed on the aircraft

test continuity

discharge indicator is used on what type of system

used for conventional or HRD system

what is the discharge indicator used for

provides immediate visual evidence of container discharge of fire extinguishing systems

types of discharge indicator

thermal

system

thermal discharge

red disk

ejects red disk when container contents are dumped overboard due to excessive heat

replace fire extinguisher before next flight

system discharge

yellow disk

ejects yellow disk if flight crew activates fire extinguisher system

replace fire extinguisher before next flight

what type of fire detection is used in cargo

smoke detectors

how is fire extinguishing system activated for cargo

by flight crew

types of system in cargo compartment

dump system

metered system

dump system

releases agent directly when cargo fire discharge switch is activated

metered system

metered bottles discharge slowly at a controlled rate through the filter regulator or restrictor

fire is extinguished for 180 minutes

lavatory extinguisher system requirement

must have smoke detector in lav with 20 or more passengers

lavatory smoke detector indication requirements

must provide warning light to cockpit

must provide warning light or audible warning at lav and flight attendant stations

lavatory fire extinguisher

must have built-in fire extinguisher that discharges automatically

how does lav fire extinguisher work

temperature in waste compartment reaches 170F > solder that seals the nozzles melt > halon discharged

fire protection in fuel tanks

nitrogen generating system

pumps nitrogen enriched air into the center fuel tank to keep oxygen level low