11.8 Fire Protection Flashcards
What are the 2 fire protection systems?
- Fire detection
- fire extinguishing systems
What do all the fire and overheat detection systems have? [3]
- Sensor
- a control unit
- panels for warnings
What can be used to detect fire, if the fire source is unknown or in large areas?
Smoke detector
Where are temperature sensitive detectors found for overheat detection? [4]
- Engine
- apu
- wheel well
- hot air ducts
What is a simple method of sensors?
Spot sensor
What is a spot sensor made out of?
Bi-metallic
Where might a spot sensor be found?
Pneumatic duct leak detection
What 2 types of continuous loop fire detection are used?
- Semi-conductor
- pneumatic pressure loops
What other names are given to semi-conductor loop detectors? [4]
- Kidde
- graviner
- Edison
- Fenwal
What does the semi conductor do when the temperature increases?
Decreases electrical resistance
What is another name for the pneumatic pressure loop detector?
- Systron
- donner loop
How does the pneumatic pressure loop detector work?
Sealed tube containing gas.
Pressure increases at high temperatures, operating a pressure switch when the warning level is reached
Where are smoke detectors found? [3]
- Cargo compartment
- toilets
- avionic compartments
What are the 2 types of smoke detection?
- Optical
- ionisation type
What functions does the control unit have? [3]
- Receives an electrical signal from sensors to identify normal and alarm conditions,
- Control test functions,
- identify fault conditions and activate necessary functions
How does the control unit identify normal and alarm conditions?
By measuring the input resistance
What may appear in the cockpit in the event of a fire? [3]
- Aural warning
- red master warning lights
- message on ECAM and EICAS
How many loops are there in essential fire warning systems?
2
What does dual loop system mean?
2 sensor and detection circuits, fire warning only triggered if both detect fire. Prevents false alarm if one has a failure
What would happen in the event of one loop failure in a dual loop system?
Faulty loop would deactivate, the other loop would take full responsibility
What must be done before each engine or apu start?
Operational test of the fire detection system
What can be used to find a fault with a fire loop?
The central maintenance computer system
What 2 features do apu’s have that engines don’t in regards to fire detection?
- Ground warning in the nose and main wheel well (red light and warning sounds)
- Automatic shut down (some a/c type automatic extinguisher)
When are wheel well detection systems required?
When there is no individual brake temperature indication or warning systems
Which wheels are monitored in wheel well detection systems?
Main landing gear wheel wells
How many loops does wheel well detection system have?
Single
What sensors can be used for pneumatic leak detection?
Spot sensors
When will the control unit trigger a crew alarm?
When the temperature is too high
What classes of cargo smoke detection is there? [5]
- Class A = baggage compartment; no detection, no extinguishing
- Class B = cargo compartment that is accessible; detection, no extinguishing
- Class C = cargo compartment NOT accessible; detection, extinguishing
- Class D = same as Class C
- Class E = cargo compartment on freighter; detection, no extinguishing
What components does the cargo smoke detection system have? [3]
- Several smoke detectors
- Control unit
- Fire control panel
In larger compartments, what smoke detectors are used?
Where air is guided to the detector where low air pressure sucks In air.
What type of smoke detectors are used on smaller cargo compartments?
Ones where smoke must directly enter the detector
How many smoke detectors are used
2 side by side, both of which must detect smoke for a warning
How many smoke detectors are found in the toilets?
1
Where and how many smoke detectors are found in the avionic compartment?
- Equipment cooling duct outlet
- 1
How many internal wires are found in Fenwal, graviner and Edison type loops? And where is earth connected to?
- One
- outer tube connected to the earth
How many internal wires are found in kidde loops? And where is earth connected?
- 2
- earth connected to the lower wire
If there is a fire, what figure must resistance have to drop below to trigger an alarm?
500 ohms
What is done to prevent an open loop and risk fire not being detected?
The end of the loop is connected to the beginning
If a break was to occur in the loop, would a fire still be detected?
Yes, because it is connected to the loop
What can be done to confirm the integrity of the continuous loop system?
Actuating a test switch
What does the fire test confirm?
Continuity of sensing elements and integrity of alarm indicator circuits
What can cause a short circuit to the semi conductor loop circuit?
Rubbing between the loop and structure
If one loop detects a fire, How long will you have to wait for an alarm to be triggered or the pilot gets a fault message?
15 seconds
What is the minimum and maximum bend radius?
Maximum = 3.2 mm Minimum = 25.4mm
What is included in a gas pressure loop? [2]
- Two pressure switches
- a resistor
What do each of the pressure switches do? [2]
- 1st = monitor or integrity switch
- 2nd = alarm switch
What happens to the monitor switch if there is a drop in pressure?
Opens and sends a fault indication to the flight deck
How does an optical smoke detector work?
Smoke comes through the detector,
The smoke reflects a light that is inside towards a photo resistor,
Decrease in resistance and sets the alarm
How can an optical smoke detector be tested?
An additional lamp is installed and shines on the photo resistor
How do ionisation type smoke detectors work?
Analyses the composition of the air because of the different mass of the molecules
Which is heavier, smoke or air molecules?
Smoke
How many chambers does an ionisation type some detector have? And what are they called?
- 2
- Reference chamber and measuring chamber
How do ionisation type smoke detectors use a radioactive material to detect smoke?
The radioactive material electrically charges the air molecules that flow through the chamber.
What type of air causes a high current flow and low resistance?
Light air molecules (because they move fast)
What type of air has a low current and high resistance?
Heavy smoke molecules (because they move slow)
What is required for fire? [3]
- Oxygen
- heat
- fuel source
What can be done to extinguish a fire?
Remove 1 of the 3 factors of the fire triangle
Where are fire extinguishers found? [4]
- Engine
- apu
- the toilets
- cargo compartments
What are the classes of fire? [5]
- A = normal flammable material (paper, wood)
- B = flammable liquids
- C = flammable gases
- D = flammable metals
- F = cooking oils and fats
What 4 types of fire extinguishers are there?
- Water
- halon
- carbon dioxide
- dry chemical powder
What are the two types of halon fire extinguishers?
- 1301 (BTM)
- 1211 (BCF)
What is the boiling temperature of halon 1301 (BTM)?
-60 degrees
What type of extinguisher is used as a portable bottle?
Halon 1211 (bcf)
How far can you attack a fire from with a portable halon 1211? And why?
- 4 meters
- it leaves the bottle as a liquid
What must you check on portable fire extinguisher bottles periodically? [2]
- Next date for an overhaul
- Check it hasn’t been used
How can you check that a portable fire extinguisher hasn’t been used? [2]
- Pressure gauge indication must be in the green
- Safety pin correctly installed
What are the main components of a fire extinguishing system? [3]
- Extinguisher bottle
- discharge head with cartridge
- piping with a spray nozzle
What Guarantees discharge of the bottle?
Nitrogen pressure at 600 psi
What are the weights are fire bottles for various locations? [3]
- Cargo compartment = 20kg
- Engine = 10 kg
- APU = 5kg
How is the bottle opened?
By a discharge head and an electrically controlled cartridge
What determines the amount of discharge heads?
The number of compartments that the bottle must supply
What group and how much of explosive powder is there in a discharge head?
400milligrams and class C
What is the wire called that is heated up by electrical current leading to the discharge cartridge?
The squib
What is the maximum service life of a cartridge?
6 years
What 1 component do all bottles have?
Pressure switch controlling a light on the flight deck when the pressure drops below 50%
What does the bottle have to prevent an overpressure? [2]
Overpressure relief function:
- Same compartment = frangible disk breaks and discharges
- Different compartment = red frangible disk on side of fuselage breaks and released overboard
On the side of the fuselage, what can indicate discharge of the bottle?
Yellow frangible disk broken
What must be switched off in the event of an engine fire? [3]
- Fuel supply
- hydraulic supply
- electric supply
What is the firing circuit connected to?
Hot battery bus powered by batteries
What is done when you operate a squid test?
A small current flows through the squib, small enough that it doesn’t fire the cartridge
To conform to regulations, what must engine fire extinguishing systems have?
2 shot installation
How long must you wait before firing the second bottle?
30 seconds
How many “shots” do you have for apu fire extinguishing ?
1
What can be found on a cargo compartment fire extinguisher bottle 2 on large aircraft?
Flow limiter to guarantee constant halon for 180 minutes
Where is the fire extinguisher located in the toilets?
In the waste container
How does a toilet fire extinguisher work?
Fusible end cap melts when a temperature of 80 degrees is reached discharging halon
How do you identify a discharged toilet extinguisher bottle?
Pressure gauge indication below green
