Cap 14 Fire And Smoke Detection

Answer 1

The level of fire and smoke detection depends on the accessibiilty of the comportment

Question 2

Two types of smoke detectors

Answer 2

~optical smoke&raquo_space;when there is smoke the light source is reflected to the sensor ,triggering smoke detection signal

~ionising smoke detector»small quantity of radioactive material held in the ionising chamber,the material emits alpha particles which ionise the air in the chamber,this allows a small current to flow between two plates in the detector,smoke absorb alpa particles ,so the ionising stops and so the current flow stops,triggering the smoke signal

Question 3

Fire detection and protection

Answer 3

Is provided in bleed air systems

Over heat protection are also provided in the wheels bay

Question 4

Fire detection is provided in two key areas

Answer 4

~engine bays

~cargo compartment

Question 5

Engine bay fire zones

Answer 5

~zone 1&raquo_space;main engine accessories,most sensitive to fire .requires fire detection and extinguisher systems

~zone 2»the compressor are
~zone 3»combustion and turbine section

Each zone is separated by a fireproof bulkhead

Alternatively there may be just COOL ZONE comprising the compressor and the fan, and HOT ZONE comprising the combustor and the turbine section

Question 6

Apu fire

Answer 6

Its automatically shut down if it detects fire,also stop if the vibration or heat is excessive

Question 7

Fire detection

Answer 7

~continuous loop engine detection system(know as fire wire):
Comprises a nickel core surrounded by a coating of eutectic salt.
If temperature rises the resistance of the slat goes down,flow current increases through the nickel core.if the units detects a drop ion resistance and if also the if the capacitance changes it triggers the signal of fire
Loop A and loop B both need to detect fire or overheat before warning is triggered,if one is faulty the faulty can be turned off to restore fire detection capability

~gas (helium) filled detectors:
Most used is the systron donner
Comprises two gas filled loops and a responder unit incorporating two pressure switches
Core contains helium gas pressurised to 7psi
If loop breaks ,pressure will drop ,causing a fault warning.
If fire is present on an intact loops ,pressure rises and triggers the fire alarm

~bi metallic overheat sesnor:
provides spot rather than area protection,when it heats up it stretches making the two contractor to close,if it cools it contracts making the contacts to separate

Question 8

Fire warning

Answer 8

Will indicate:
~fire master caution
~fire warining bell
~associated eng fire
~illuminates extinguisher operating handle
~displays warning on EICAS or ECAM

Question 9

Engine fire suppression system on Boeing 737

Answer 9

~pulling the fire handle»

~closes wing spar shut off valve,isolating engine bay from fuel system
~closes the bleed air PRSOV
~shuts off hydraulic pump
~isolate hyd supply
~isolates electrical genrator
~arms the extinguisher
~closes the apu shit off valve

Question 10

Engine fire suppression

Answer 10

~2 fire extinguisher bottle per eng

Question 11

Cargo compartment extinguishers

Answer 11

`extinguishing agent HALON pressurised by NITROGEN

Question 12

Toilet comportment fire extinguishers

Answer 12

~protected by automated extinguishers
~fires into waste bin and under sink area when heat is detected.
Freon or BCF extinguishant