15.20 - Fire Protection Systems Flashcards
What are the three parts of the fire triangle?
Heat, fuel and oxygen
What are the two types of continuous loop detectors?
Resistance type (- with temp) Capacitance type (+ with temp)
What happens to resistance in the resistance type loop detector as the temperature increases?
It decreases
What happens to capacitance with an increase in temperature in a capacitance loop detector?
It increases
How does heat affect a bi-metallic strip?
The strip heats up and makes contact in the switch which completes the circuit
What are the two main continuous loop detector systems?
Fenwall and Kidde
What are the two types of gas (pneumatic)fire detectors?
Lindberg system and the systron-donner system
How does a pneumatic fire detection system work?
The gas inside is stable at low temperatures. It is released at higher temperatures and closes a pressure switch at a predetermined value.
What gasses are used in the Systron-donner type fire detection system?
Hydrogen and helium
Will you get a false alarm with a pneumatic fire detection system?
No, it will provide a loop fault message
How often should the detectors be clipped in when installed?
Every 6-inches
What could excessive bending do to a detector installation?
It could work-harden the capillary, causing it to break
What are the main causes of false fire workings?
Ingress of moisture
Faulty installation
Lack of cleanliness
When inspecting a fire detection system, what checks/tests are done?
Acceptance checks (when checked after transit) and Functional tests.
How is the function check completed on a resistance type fire protection system?
The centre electrode is grounded
How is the function check completed on a capacitance type fire protection system?
Additional capacitance is introduced into the circuit
Is any work on dressings dents, gouges, kinks permitted on fire wire?
No. No dressing is permitted. It should be replaced
What type of brush should be used on fire detection systems?
Camel hair brush
Why is normal compressed air not used for drying, newly cleaned fire wire?
It can contain moisture or oil, so nitrogen or dry bottled air cans are used.
What is the type of fire detection system you would find on a Boeing or Airbus?
Systron Donner system.
How many serviceable loops need to signal a fire?
Both loops. It will decrease to one loop if one of the loops is detected as unserviceable.
Why are halogenated hydrocarbon compounds banned for use?
They destroy the ozone layer in the atmosphere.
How does HFC-125 suppress a fire?
It absorbs heat energy faster than the heat can be generated.
The most modern fire extinguisher bottles do not have a pressure gauge, how would you know how much is in there?
By removing it from the aircraft and weighing it.
What gas is charged in an aircraft fire extinguisher bottle?
Nitrogen gas at 600psi at 15 degrees C
What is a fire extinguisher cartridge also known as?
A squib
What is special about the APU fire protection system on the ground?
It is automatic and will release the agent
What are the 3 types of engine bottle discharge indicators?
Mechanical indicators (protruding indicators on the cap)
Pressure gauges
Busting Disc
What is the purpose of a compensating resistor in a thermocouple temperature sensing system?
It corrects for varying ambient temperatures at the cold junction
Can thermocouple leads be installed either way round?
No, they are designed for a specific installation and may not be altered
How are dissimilar metals in a thermocouple connected?
By welding of the two metals
What is a fire detection system that has a single wire surrounded by ceramic beads?
Fenwall system
How is the fire extinguishing agent distributed in the engine?
Spray nozzles and perforated tubing
What is a spot detector?
A bi-metallic strip that when heated, closes the contact & produces a warning
