15.20 Flashcards
What is a fire zone?
A zone required by the manufacturer to have a fire detection/extinguishing system and resistance
What are the two types of turbine failures?
Thermodynamic
Mechanical
What does thermodynamics cause?
An upset to the amount of airflow used to cool down combustion so the turbines can operate at a decent temp
If the turbines get too hot what can happen?
They can melt and reduce thrust
What can the rapid build up of ice in inlet screens or inlet guide vanes result in?
Overheating of turbines or breaking them (be thrown outward)
What 2 things can a thermodynamic failure result in?
Severed tail cone
Penetration of the structure
What are thermodynamic failures caused by?
Ice
Excessive bleed air
Compressor stall caused by faulty controls
Excessive fuel
What can mechanical failures cause?
Puncture tailcone
Overheat conditions or fires
What can mechanical failures cause?
Puncture tailcone
Overheat conditions or fires
What can excessive fuel that runs through the exhaust pipe cause?
A fire
What does a complete fire system include?
Detection and extinguishment
What are the three types of fire detectors in an aircraft?
Overheat detectors
Rate of temperature rise
Flame detectors
What are the two common types of system for fire detection?
Spot detectors
Continuous loop
What uses individual sensors to monitor a fire zone?
Spot detector
What is different about continuous loop in regards to spot detector?
Continuous loop covers a wide range and is used on transport aircraft
What do continuous loop system fire extinguishers use to detect?
Several loop type sensors
What aircraft utilise thermoswitch or thermocouple?
Older aircraft
What does a thermal switch comprise of?
One or more lights and heat sensitive thermal switches that complete electrical circuits at a set temperature
What are thermal switches on parallel and series to.
Series with the lights
Parallel with eachother
What can you press to test the lights?
Warning lights
How is the bulb tested?
By pushing it in
What does a thermocouple rely on? And what does it not give?
Rare of temperature rise and does not give an indication when overheat condition occurs or a short circuit
3 circuits of thermocouple?
Detector
Alarm
Test
If both hot junctions are heated at the same time, what voltage occurs?
Zero
Are the thermocouples in series or parallel to each other?
Series
When are optical fire detection systems designed to alarm?
When they detector the presence of radiation
What are the two types of optical detectors
Ultraviolet
Infrared
Where are inferred used?
Helicopters and light aircraft
What are the two functions of the pneumatic detector?
Overall temperature
Localised Discreet temperature
How does a pneumatic detector work?
Gas pressure inside a tube increases and an internal switch is closed
What does the integrity switch do if pressure is lost meaning a leak is detected?
It opens triggering a faukt alarm
How is the averaging function activated?
By increase of pressure of helium gas inside the detector tube
How is discrete sensing accomplished?
Hydrogen filled core material in the sensor tube. It is then released at a pre set temp which increases the pressure and activates alarm switches
What is one word to describe the averaging and discrete detection functions?
Reversible meaning that when the sensor tube cools, the pressure is reduced and the hydrogen returns to its core
What does the titanium wire act as in pneumatic continuous systems?
The gas absorption material because it has a quantity of hydrogen. The tube is sealed at one end and connected to a responder at the other
How many electircal switches does the responder have?
2
How many electrical switches does the responder have?
2
What is the fire warning function provided by?
The titanium wire
What must be ensured in a dual loop system?
That both loops are activated before an alarm sounds
What must be ensured in a dual loop system?
That both loops are activated before an alarm sounds
What happens if one loop fails?
Integrity switch opens
What happens if one loop fails?
Integrity switch opens (initiative system maintenance and uses the serviceable loop)
Two types of continuous loop systems?
Fenwall kiddie
What is fenwall?
Uses inconnel tube with eutectic salts
How are Fenwall systems organised?
In series
Hat happens when the Fenwall system when the fire has been exitingushed or critics, temp lowered?
Gore back into standby ready to detect fire or overheating
What detects current flow in the Fenwall system?
The control unit which sends a signal to output relay
What is the kiddie continuous loop system? And where are they connected too?
Two wires are embedded in the inconnel tube (one to ground and other to fire detection control unit)
As temperature increases in kiddie, what happens to the resistance to the ground?
Decreases and fire control unit defects this and sends signal to flight deck
What does the sensing element consist of?
An infinite amount of thermistors in parallel along its length
What does the system respond to?
A sum of the thermistors resulting in an average
Where are sensing elements routed?
Through non hazardous hot spots with high normal temps so they don’t set off a false alarm
What is a general compartment temperature rise commonly caused by? (Overheat)
Leakage of hot bleed air or combustion gas into the engine
What is converted into signals for cockpit display?
The sensing element loop signals
What does it mean if the sensing element is unbroken during a system test?
A fire is simulated showing the continuity and the integrity of the alarm switch is good
What are dual loop systems?
Two complete fire detection systems
What is “AND” logic?
Both loops must signal to trigger a fire warning to prevent against false warning
What happens if one loop is defective?
The fire signalling loop indicates a fault and the flight deck get an indication and the selector switch disconnects that loop. Aircraft can still fly if they single loop is serviceable
What automatically performs the decision making and loop switching functionalities when a fault is detected?
Dual loop systems
What does automatic self interrogation do?
Eliminates fault indication (corrects itself)
Ensures detection of fire if one dual loop is used (fire detection but one working)
Tests the other loop if only one detects fire
What are the control units for basic types of fire systems housed in?
Hermetically sealed aluminium case
What about for more sophisticated systems control unit’s?
They have removable control cards for hazard areas and unique functions
In advanced systems, what controls the engines fire protection functions?
The detection system circuitry
What is an individual single shot system involved in?
Apu
Fuel burning heaters
Combustion areas
What are the fixed fire extinguishers used to do?
Dilute the air with an inert gas that does not support combustion
What do fire extinguishers use to discharge the agent?
Perforated tubing
Discharge nozzles
What types of extinguishers use open ended nozzles to dishcharge their gas?
High rate of discharge to deliver quantity in 1-2 seconds
Why Halon 1301?
Low toxicity
Non corrosive
No clean up
What are HRD bottles made out of?
Stainless steel
What shape of containers provide the lightest weight?
Spherical
Where are cylindrical cylinders used?
Where space is a factor
Where is the squib (cartridge) and frangible disc located?
In the outlet of the discharge valve assembly
What is the standard type of rupturing the squib?
Standard type using a slug driven by explosive energy to rupture a closed disc
How can you verify the fire extinguishers charge agent?
Use a vibration resistant helical bourbon tubeb
What does a combination gauge visually indicate?
Actual continued pressure and provides an electrical signal if pressure is lost (don’t need discharge indicators)
Where are two way check valves required?
In a two shot system to prevent the agent in the reserve bottle from backing up in to empty main one
What do discharge indicators provide?
Immediate visual detection of container discharge mounted on the skin
What does red mean?
Thermal discharge
What does yellow mean?
Fire bottle activated
When red or yellow discs show what must you do?
Replace the bottle
Where are fire switches located?
On the centre overhead panel or centre console
When a fire switch is activated what two things happen?
The engine stops because the fuel control valve closes. (It is Isolated)
Armed fire extinguishing system
How do you operate the two types of fire switches in the cockpit?
Pulled and turned
Push type
What does a fire detection card in the system card file monitor?
The loops for overheat, fires and faults
What happens technically if the fire detection system detects an overheat or fire condition?
Sends a signal to Aircraft Information Management System and then to the warning electronics unit
What does the fuel control switch do when there is an engine fire?
The warning light comes on
