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Questions and Answers
What is the primary characteristic of the thermocouple in fire warning systems?
What is the primary characteristic of the thermocouple in fire warning systems?
How does a pneumatic continuous-loop detector respond to temperature changes?
How does a pneumatic continuous-loop detector respond to temperature changes?
What is the purpose of the hot junction in a thermocouple system?
What is the purpose of the hot junction in a thermocouple system?
Which continuous-loop system is primarily designed for the wheel well and powerplant areas?
Which continuous-loop system is primarily designed for the wheel well and powerplant areas?
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Which of the following statements about the thermocouple fire warning system is false?
Which of the following statements about the thermocouple fire warning system is false?
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What mechanism does the pneumatic detector use to actuate the alarm circuit?
What mechanism does the pneumatic detector use to actuate the alarm circuit?
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What differentiates continuous-loop systems from spot-type temperature detectors?
What differentiates continuous-loop systems from spot-type temperature detectors?
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What is the function of the pressure diaphragm in the responder assembly?
What is the function of the pressure diaphragm in the responder assembly?
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At what temperature does the alarm switch in the responder assembly typically activate?
At what temperature does the alarm switch in the responder assembly typically activate?
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What occurs when the hydrogen-filled core material is exposed to temperatures at or above the preset limit?
What occurs when the hydrogen-filled core material is exposed to temperatures at or above the preset limit?
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What happens to the alarm switch when the sensor tube cools?
What happens to the alarm switch when the sensor tube cools?
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Which type of smoke detection system uses a photoelectric cell?
Which type of smoke detection system uses a photoelectric cell?
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What is the primary purpose of the smoke detection system?
What is the primary purpose of the smoke detection system?
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What warning system is in place to inform the flight crew of a non-operational condition?
What warning system is in place to inform the flight crew of a non-operational condition?
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Which of the following statements about the discrete function of the fire/overheat detector is true?
Which of the following statements about the discrete function of the fire/overheat detector is true?
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What type of smoke detector is primarily based on the phenomenon of light refraction?
What type of smoke detector is primarily based on the phenomenon of light refraction?
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What is the primary difference between the dump system and the metered system for cargo fire extinguishing?
What is the primary difference between the dump system and the metered system for cargo fire extinguishing?
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What triggers the discharge of Halon from the cargo compartment extinguishing system?
What triggers the discharge of Halon from the cargo compartment extinguishing system?
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Which component is responsible for sealing the pressurized extinguishing bottle?
Which component is responsible for sealing the pressurized extinguishing bottle?
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How long can the metered system keep a fire extinguished in the cargo compartment?
How long can the metered system keep a fire extinguished in the cargo compartment?
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What is the purpose of the pressure switch in the extinguishing system?
What is the purpose of the pressure switch in the extinguishing system?
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What is the primary function of optical sensors in flame detection systems?
What is the primary function of optical sensors in flame detection systems?
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What triggers the alarm LED in the lavatory's smoke detector?
What triggers the alarm LED in the lavatory's smoke detector?
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Which type of electromagnetic radiation is primarily focused on by infrared sensors?
Which type of electromagnetic radiation is primarily focused on by infrared sensors?
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What is a key characteristic of carbon monoxide that makes it dangerous?
What is a key characteristic of carbon monoxide that makes it dangerous?
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What commonality exists between electronic and chemical color-change carbon monoxide detectors?
What commonality exists between electronic and chemical color-change carbon monoxide detectors?
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How do flame detectors differentiate between actual flames and false alarm sources?
How do flame detectors differentiate between actual flames and false alarm sources?
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What happens to the thermoelectric voltages in the flame detection sensors?
What happens to the thermoelectric voltages in the flame detection sensors?
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What specific feature is built into every lavatory for fire safety?
What specific feature is built into every lavatory for fire safety?
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What problem does the carbon monoxide detection system primarily address?
What problem does the carbon monoxide detection system primarily address?
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What type of smoke detector is described for the lavatory?
What type of smoke detector is described for the lavatory?
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What happens to the color of a certain chemical in the presence of carbon monoxide?
What happens to the color of a certain chemical in the presence of carbon monoxide?
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Which of the following is a characteristic of Halon as a fire extinguishing agent?
Which of the following is a characteristic of Halon as a fire extinguishing agent?
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What is the primary mechanism by which carbon dioxide (CO2) extinguishes fires?
What is the primary mechanism by which carbon dioxide (CO2) extinguishes fires?
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In what compartments are fixed fire extinguishing systems installed in transport aircraft?
In what compartments are fixed fire extinguishing systems installed in transport aircraft?
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What alert occurs in the cockpit when smoke is detected in a cargo compartment?
What alert occurs in the cockpit when smoke is detected in a cargo compartment?
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Which statement about Halon is true?
Which statement about Halon is true?
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What is the function of the smoke detection system in cargo compartments?
What is the function of the smoke detection system in cargo compartments?
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Which type of Halon is classified as a total flooding agent?
Which type of Halon is classified as a total flooding agent?
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Why is carbon dioxide (CO2) commonly used in aircraft fire extinguishers?
Why is carbon dioxide (CO2) commonly used in aircraft fire extinguishers?
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Which of the following compartments does NOT typically have a fixed fire extinguishing system?
Which of the following compartments does NOT typically have a fixed fire extinguishing system?
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Which class of fire involves ordinary combustible materials such as wood and cloth?
Which class of fire involves ordinary combustible materials such as wood and cloth?
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What type of fires involve energized electrical equipment, requiring nonconductive extinguishing media?
What type of fires involve energized electrical equipment, requiring nonconductive extinguishing media?
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Which fire detection method is typically NOT included in most large turbine-engine aircraft fire protection systems?
Which fire detection method is typically NOT included in most large turbine-engine aircraft fire protection systems?
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What type of fire involves combustible metals such as magnesium and lithium?
What type of fire involves combustible metals such as magnesium and lithium?
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Which of the following compartments is not typically protected by a fixed fire extinguishing system in aircraft?
Which of the following compartments is not typically protected by a fixed fire extinguishing system in aircraft?
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What characteristic distinguishes a thermocouple fire warning system from a thermal switch system?
What characteristic distinguishes a thermocouple fire warning system from a thermal switch system?
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Which of the following statements accurately describes pneumatic continuous-loop systems?
Which of the following statements accurately describes pneumatic continuous-loop systems?
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What type of gases fill the fire/overheat detector in pneumatic systems to facilitate temperature measurement?
What type of gases fill the fire/overheat detector in pneumatic systems to facilitate temperature measurement?
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What is a limitation of thermocouple systems in fire detection?
What is a limitation of thermocouple systems in fire detection?
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In the context of continuous-loop systems, which component permits more complete coverage compared to spot-type detectors?
In the context of continuous-loop systems, which component permits more complete coverage compared to spot-type detectors?
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What is the role of the alarm switch in the pneumatic continuous-loop fire/overheat detector?
What is the role of the alarm switch in the pneumatic continuous-loop fire/overheat detector?
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Which mechanism is employed by the light refraction type of smoke detector to activate its alarm?
Which mechanism is employed by the light refraction type of smoke detector to activate its alarm?
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In the event of a failure in the helium gas pressure in the test circuit, what is the primary indication for the flight crew?
In the event of a failure in the helium gas pressure in the test circuit, what is the primary indication for the flight crew?
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How does the averaging and discrete function of the fire/overheat detector respond to temperature changes?
How does the averaging and discrete function of the fire/overheat detector respond to temperature changes?
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Which type of gas is used in the core material of the fire/overheat detector, and what is its significance?
Which type of gas is used in the core material of the fire/overheat detector, and what is its significance?
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Study Notes
Aircraft Fire Protection Systems
- Fire is a serious threat to aircraft, protected by fixed systems.
- "Fixed" systems are permanent installations, contrasting with portable extinguishers.
- A comprehensive system includes detection and extinguishing mechanisms.
- Common fire zones include engines, auxiliary power units (APUs), cargo/baggage, lavatories, electronic bays, wheel wells, and bleed air ducts.
Fire Detection Methods
- Modern aircraft use various detection methods.
- Rate-of-temperature-rise detection is a method used to alert against overheating.
- Overheat detectors are crucial in identifying abnormal temperature increases.
- Smoke detectors are used to identify the presence of smoke which is indicative of a fire condition.
- Carbon monoxide detectors are essential to identify the dangerous gas.
- Visual observation by crew or passengers is occasionally used.
Classes of Aircraft Fires
- Aircraft fires are classified by their fuel source
- Class A: Ordinary combustibles (wood, cloth, paper, plastics).
- Class B: Flammable liquids (petroleum, oils, solvents).
- Class C: Electrical equipment fires (demand electrically non-conductive extinguishing media).
- Class D: Combustible metal fires (magnesium, titanium).
Overheat and Fire Protection System Requirements
- Current aircraft systems rely primarily on fire detection, not crew observation.
- Ideal systems should not give false alarms, locate fires accurately, indicate fire extinguishment, detect re-ignition, continuously monitor fire, and allow electrical testing from the cockpit.
- Systems should withstand various conditions (oil, water, extreme temperatures, vibration).
- Systems should connect with the aircraft power supply directly.
- Systems should have visual indicators and audible alarms that show the fire location.
- Every engine has its own detection system.
Thermal Switch System
- Thermal switches are heat-sensitive units.
- The switches complete circuits at certain temperatures and they are connected in parallel.
- The switches are in series with the indicator lights.
- If the temperature rises to a set value, the switch closes the circuit to indicate fire or overheating.
Thermocouple Systems
- Thermocouples are made from dissimilar metals (like chromel and constantan) and function based on temperature differences to trigger alarms when heat is detected.
- Thermocouples vary from thermal switches in that they depend on the rate of temperature rise rather than specific temperatures.
- Their use in the system is useful as a warning against engine over-heating or electrical shorts.
- When a fire occurs, the hot junction heats more quickly than the reference junction, triggering an alarm.
Continuous-Loop Systems
- Continuous-loop systems allow more comprehensive coverage than spot temperature detectors.
- They commonly use thermistor-type detectors (like Kidde and Fenwal) or pneumatic pressure detectors (like Systron-Donner).
- The detection loop often surrounds areas like power plants and wheel wells, where it monitors temperature and signals when there's a danger.
Pneumatic Continuous-Loop Systems
- These systems detect general temperature changes.
- They use pressure inside a fixed-volume device containing helium gas to gauge temperature changes.
- A pressure diaphragm responds to temperature changes, operating the alarm circuit.
- The measurements are factory-preset and cannot be adjusted.
- A reduction in the pressure activates the alarm system to return to a normal configuration.
Smoke Detection Systems
- The systems monitor lavatories and baggage compartments for smoke.
- Light refraction detectors use photoelectric cells to detect light changes.
- Ionization detectors use radioactive material to ionize air particles when smoke is present.
Lavatory Smoke Detectors
- Each lavatory must have a built-in fire extinguisher, and a smoke detector located on the ceiling to detect smoke which issues an alarm in the cockpit, cockpit light, and audible warning on flight attendant stations.
Flame Detection System
- Optical sensors detect specific radiation emissions from flames (infrared and ultraviolet).
- The sensing device minutely heats up from the radiation, resulting in small voltages, which signal a possible fire.
- They detect hydrocarbon flames and ignore false alarm sources like sunlight and lights.
Carbon Monoxide Detection System
- Carbon monoxide is a dangerous, colorless, odorless gas.
- Systems are used for crew and passenger safety.
- Electronic detectors and color-change detectors are used, changing color in the presence of the gas.
Extinguishing Agents
- Halogenated hydrocarbons (e.g., Halon 1301, 1211) are effective on various aircraft fires with their high efficiency and low toxicity.
- Inert gases (e.g., carbon dioxide) work well on external fires as they dilute the oxygen content, thus inhibiting combustion processes.
Installed Fire Extinguisher Systems
- Aircraft have fixed fire extinguishing systems in various parts, like engine compartments, APU compartments, cargo compartments, and lavatories.
- Cargo compartment systems have smoke detectors that trigger alarms in the flight deck if smoke is sensed; indicators light up and give warnings on the flight console.
Cargo Compartment Extinguisher System
- The system uses squibs (explosive devices) to release extinguishing agents when smoke detectors trigger activation on the flight deck.
- This occurs at precise and manageable amounts to control and contain fire damage.
- The system uses two types: a dump system which releases agent immediately and a metered system to carefully regulate the release over time, both ensuring a consistent fire suppression in specific locations of the aircraft.
Lavatory Fire Extinguisher System
- Lavatories have fire extinguishers with Halon.
- When the temperature reaches 170°F in the lavatory, the extinguishing process begins.
Fire Detection System Maintenance
- Regular checks are important to maintain the condition of the detection system located in high-activity areas.
- The system should regularly check for any issues like crushed, kinked, sharp bends, and any other irregularities.
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Description
Test your knowledge on aircraft fire protection systems, including detection methods and fire classification. This quiz covers critical fire zones and the technologies used to combat and detect fires on aircraft. Understand the importance of fixed systems compared to portable extinguishers.
