M15.20 Fire Protection Systems

Question 1

What is the primary purpose of a fire protection system in multi-engine aircraft?

Answer 1

To protect against fire in the designated ‘fire zone’

Question 2

What areas of an aircraft are designated as fire zones?

Answer 2

‘Fire zone’ is an area requiring fire detection and/or extinguishing equipment

Question 3

Which aircraft components are required to have fire protection systems?

Answer 3

• Engine
• Auxiliary Power Units (APUs)

Question 4

What are the two major types of turbine failure?

Answer 4

• Thermodynamic
• Mechanical

Question 5

What causes thermodynamic turbine failure?

Answer 5

An upset in the proportion of air used to cool combustion temperatures

Question 6

What can result from a thermodynamic turbine failure?

Answer 6

Turbine blades can melt, causing a sudden loss of thrust

Question 7

What are common causes of thermodynamic failures?

Answer 7

• Ice
• Excess air bleed or leakage
• Faulty controls

Question 8

What can mechanical turbine failures cause?

Answer 8

Fractured or thrown blades can puncture the tail cone, causing overheating or fires

Question 9

What components are included in a complete fire protection system?

Answer 9

• Fire detection systems
• Fire extinguishing systems

Question 10

What types of detectors are used to monitor fires in aircraft?

Answer 10

• Overheat detectors
• Rate of temperature rise detectors
• Flame detectors

Question 11

What features must a fire detector system include?

Answer 11

• 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

Question 12

What are the two common types of fire detection systems on aircraft?

Answer 12

• Spot detectors
• Continuous loop systems

Question 13

How does a thermal switch system operate?

Answer 13

Uses heat-sensitive units that complete electrical circuits at a set temperature

Question 14

What is the principle of operation for a thermocouple fire warning system?

Answer 14

Depends on the rate of temperature rise

Question 15

What happens when the temperature rises rapidly in a thermocouple system?

Answer 15

It produces voltage due to the temperature difference between junctions

Question 16

What are optical fire detection systems designed to detect?

Answer 16

Specific radiation emissions from hydrocarbon flames

Question 17

What types of optical sensors are used in fire detection?

Answer 17

• Infrared (IR)
• Ultraviolet

Question 18

How do pneumatic thermal fire detection systems operate?

Answer 18

Based on gas laws; pressure increases in a heated tube

Question 19

What are the two functions of pneumatic detectors?

Answer 19

• Average temperature sensing
• Discrete temperature sensing

Question 20

What is the function of the titanium wire in the pneumatic continuous system?

Answer 20

Releases hydrogen gas when exposed to heat, increasing pressure to trigger alarm

Question 21

What are the two widely used types of continuous loop systems?

Answer 21

• Fenwal systems
• Kidde systems

Question 22

How does the Fenwal continuous loop system detect fire?

Answer 22

Resistance of eutectic salt drops sharply during overheat, causing current flow

Question 23

How does the Kidde continuous loop system function?

Answer 23

Monitors electrical resistance in the thermistor core material as temperature changes

Question 24

What is the purpose of dual loop systems in fire detection?

Answer 24

Provides better reliability against false fire warnings

Question 25

What happens if one loop in a dual loop system is defective?

Answer 25

The system can switch to single loop operation to continue fire detection

Question 26

What does the fire detection control unit typically contain?

Answer 26

Electronic resistance monitoring and alarm output circuits

Question 27

What are the designated fire zones in the powerplant installation?

Answer 27

* Engine power section * Engine accessory section * Complete powerplant compartment

Question 28

What is the purpose of control modules in sophisticated systems?

Answer 28

Control modules contain removable control cards having circuitry for individual hazard areas and/or unique functions.

Question 29

What functions does the detection system circuitry control in advanced applications?

Answer 29

It controls all the aircraft fire protection functions, including fire detection and extinguishing for engines, APU, cargo bays, and bleed air systems.

Question 30

List the designated fire zones in a powerplant installation.

Answer 30

* 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

Question 31

What is required for engine fire extinguishing systems in transport category certified aircraft?

Answer 31

They are required to have two discharges that produce a sufficient concentration of extinguishing agent.

Question 32

What is a common system used for APUs and fuel-burning heaters?

Answer 32

An individual single-shot system.

Question 33

What is the main purpose of fixed fire extinguisher systems in engine fire protection?

Answer 33

To dilute the atmosphere with an inert agent that does not support combustion.

Question 34

Describe High Rate of Discharge (HRD) systems.

Answer 34

HRD systems use open-end tubes to deliver a quantity of extinguishing agent in one to two seconds.

Question 35

What is the most common extinguishing agent used in aircraft fire protection systems?

Answer 35

Halon 1301.

Question 36

What are the characteristics of Halon 1301?

Answer 36

* Effective capability * Relatively low toxicity * Non-corrosive * Requires no clean-up when discharged

Question 37

What materials are HRD fire extinguisher containers typically made from?

Answer 37

They are normally manufactured from stainless steel, with alternatives like titanium available.

Question 38

What is the typical design shape of most aircraft fire extinguisher containers?

Answer 38

Spherical design.

Question 39

What are discharge valves used for in fire extinguisher systems?

Answer 39

They are installed on the containers to release the extinguishing agent.

Question 40

What is the function of a thermal discharge indicator?

Answer 40

It ejects a red disc to show when container contents have been dumped overboard due to excessive heat.

Question 41

What does a yellow disc discharge indicator indicate?

Answer 41

It shows that the fire extinguishing system was activated by the flight crew.

Question 42

Where are fire switches typically located in aircraft?

Answer 42

On the centre overhead panel or centre console in the flight deck.

Question 43

What happens when a fire switch is activated?

Answer 43

* The engine stops as the fuel control valve closes * The fire extinguishing system is armed

Question 44

What type of warning systems are installed in the flight deck for fire detection?

Answer 44

Visible and audible warning systems.

Question 45

How many fire detection loops does each engine have in the B777 aircraft?

Answer 45

Two fire detection loops.

Question 46

What does the fire detection card monitor?

Answer 46

It monitors the loops for fires, overheat conditions, and faults.

Question 47

What indications occur in the flight deck if an engine fire is detected?

Answer 47

* 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