M15.20 Fire Protection Systems Flashcards
What is the primary purpose of a fire protection system in multi-engine aircraft?
To protect against fire in the designated ‘fire zone’
What areas of an aircraft are designated as fire zones?
‘Fire zone’ is an area requiring fire detection and/or extinguishing equipment
Which aircraft components are required to have fire protection systems?
- Engine
- Auxiliary Power Units (APUs)
What are the two major types of turbine failure?
- Thermodynamic
- Mechanical
What causes thermodynamic turbine failure?
An upset in the proportion of air used to cool combustion temperatures
What can result from a thermodynamic turbine failure?
Turbine blades can melt, causing a sudden loss of thrust
What are common causes of thermodynamic failures?
- Ice
- Excess air bleed or leakage
- Faulty controls
What can mechanical turbine failures cause?
Fractured or thrown blades can puncture the tail cone, causing overheating or fires
What components are included in a complete fire protection system?
- Fire detection systems
- Fire extinguishing systems
What types of detectors are used to monitor fires in aircraft?
- Overheat detectors
- Rate of temperature rise detectors
- Flame detectors
What features must a fire detector system include?
- No false warnings
- Rapid indication of fire
- Accurate location of fire
- Indication that fire is out
- Continuous indication during fire
- Electrical testing capability
- Resistance to damage
- Lightweight and easy to mount
- Operates directly from power system
- Minimum electrical current when not indicating fire
What are the two common types of fire detection systems on aircraft?
- Spot detectors
- Continuous loop systems
How does a thermal switch system operate?
Uses heat-sensitive units that complete electrical circuits at a set temperature
What is the principle of operation for a thermocouple fire warning system?
Depends on the rate of temperature rise
What happens when the temperature rises rapidly in a thermocouple system?
It produces voltage due to the temperature difference between junctions
What are optical fire detection systems designed to detect?
Specific radiation emissions from hydrocarbon flames
What types of optical sensors are used in fire detection?
- Infrared (IR)
- Ultraviolet
How do pneumatic thermal fire detection systems operate?
Based on gas laws; pressure increases in a heated tube
What are the two functions of pneumatic detectors?
- Average temperature sensing
- Discrete temperature sensing
What is the function of the titanium wire in the pneumatic continuous system?
Releases hydrogen gas when exposed to heat, increasing pressure to trigger alarm
What are the two widely used types of continuous loop systems?
- Fenwal systems
- Kidde systems
How does the Fenwal continuous loop system detect fire?
Resistance of eutectic salt drops sharply during overheat, causing current flow
How does the Kidde continuous loop system function?
Monitors electrical resistance in the thermistor core material as temperature changes
What is the purpose of dual loop systems in fire detection?
Provides better reliability against false fire warnings
What happens if one loop in a dual loop system is defective?
The system can switch to single loop operation to continue fire detection
What does the fire detection control unit typically contain?
Electronic resistance monitoring and alarm output circuits
What are the designated fire zones in the powerplant installation?
- Engine power section
- Engine accessory section
- Complete powerplant compartment
What is the purpose of control modules in sophisticated systems?
Control modules contain removable control cards having circuitry for individual hazard areas and/or unique functions.
What functions does the detection system circuitry control in advanced applications?
It controls all the aircraft fire protection functions, including fire detection and extinguishing for engines, APU, cargo bays, and bleed air systems.
List the designated fire zones in a powerplant installation.
- The engine power section
- The engine accessory section (except for reciprocating engines)
- Any APU compartment
- Any fuel-burning heater and other combustion equipment installation
- The compressor and accessory sections of turbine engines
- Combustor, turbine, and tailpipe sections of turbine engine installations
What is required for engine fire extinguishing systems in transport category certified aircraft?
They are required to have two discharges that produce a sufficient concentration of extinguishing agent.
What is a common system used for APUs and fuel-burning heaters?
An individual single-shot system.
What is the main purpose of fixed fire extinguisher systems in engine fire protection?
To dilute the atmosphere with an inert agent that does not support combustion.
Describe High Rate of Discharge (HRD) systems.
HRD systems use open-end tubes to deliver a quantity of extinguishing agent in one to two seconds.
What is the most common extinguishing agent used in aircraft fire protection systems?
Halon 1301.
What are the characteristics of Halon 1301?
- Effective capability
- Relatively low toxicity
- Non-corrosive
- Requires no clean-up when discharged
What materials are HRD fire extinguisher containers typically made from?
They are normally manufactured from stainless steel, with alternatives like titanium available.
What is the typical design shape of most aircraft fire extinguisher containers?
Spherical design.
What are discharge valves used for in fire extinguisher systems?
They are installed on the containers to release the extinguishing agent.
What is the function of a thermal discharge indicator?
It ejects a red disc to show when container contents have been dumped overboard due to excessive heat.
What does a yellow disc discharge indicator indicate?
It shows that the fire extinguishing system was activated by the flight crew.
Where are fire switches typically located in aircraft?
On the centre overhead panel or centre console in the flight deck.
What happens when a fire switch is activated?
- The engine stops as the fuel control valve closes
- The fire extinguishing system is armed
What type of warning systems are installed in the flight deck for fire detection?
Visible and audible warning systems.
How many fire detection loops does each engine have in the B777 aircraft?
Two fire detection loops.
What does the fire detection card monitor?
It monitors the loops for fires, overheat conditions, and faults.
What indications occur in the flight deck if an engine fire is detected?
- The master warning lights come on
- The fire warning aural operates
- An engine fire warning message shows
- The engine fire warning light comes on
- The fuel control switch fire warning light comes on
