A complete engine fire protection system on a turbine-powered aircraft consists of which two basic subsystems?
ACS code: AM.III.E
Correct answer: A fire detection system and a fire extinguishing system
Rationale: A fire protection system is divided into two functional parts: a detection system that warns the crew of a fire or overheat condition, and an extinguishing system that delivers an agent to put the fire out. The other choices name individual components but not the two-part division of the overall protection system.
Which type of fire detector senses fire by responding to the rate at which a monitored area's temperature increases?
ACS code: AM.III.E
Correct answer: Rate-of-rise (thermal switch) detector
Rationale: A rate-of-rise detector uses thermocouples or bimetallic elements arranged so that a rapid temperature increase, faster than normal engine warm-up, triggers the warning. Optical detectors sense radiant energy, and CO detectors sense a gas, not a rate of temperature change.
What is the principal advantage of a continuous-loop fire detection system over a series of individual spot detectors?
ACS code: AM.III.E
Correct answer: It provides more complete coverage of the fire hazard area
Rationale: A continuous loop runs as an unbroken sensing element around the entire hazard zone, so a fire anywhere along its length is detected, giving better area coverage than discrete spot units. Loop systems still require power and, like any system, can give false warnings, so those statements are incorrect.
A pneumatic (gas-filled tube) continuous-element detector triggers a fire warning when heating causes what to occur inside the sensing tube?
ACS code: AM.III.E
Correct answer: Gas pressure rises and closes the diaphragm switch
Rationale: In pneumatic detectors the sealed tube is charged with a gas; localized or average heating raises the internal pressure, which acts on a diaphragm that closes the alarm switch contacts. A drop in pressure instead indicates a leak (integrity fault), and the core-short mechanism describes a resistance-type loop, not a pneumatic one.
A fire detection system that gives a warning when actually heated but does not signal a fault when the loop is broken would most likely fail to indicate which condition?
ACS code: AM.III.E
Correct answer: An open (broken) sensing element
Rationale: Modern detection systems include integrity (fault) monitoring that flags an open in the loop so a broken element is not mistaken for a no-fire condition. A system lacking that feature would still alarm on real heat or certain shorts but would silently fail to reveal an open element, leaving the area unprotected.
What method is commonly used to determine whether an engine fire extinguisher container holds its required charge of agent?
ACS code: AM.III.E
Correct answer: Weigh the container and compare it to the specified charged weight
Rationale: The standard check of an installed extinguisher charge is to weigh the bottle and compare the result against the placarded full charge weight, since the agent quantity correlates directly to weight. Shaking is unreliable, and cartridge resistance verifies the firing circuit, not the agent quantity.
From where does an aircraft auxiliary power unit (APU) receive its fire-warning signal?
ACS code: AM.III.E
Correct answer: Its own dedicated fire-detection system.
Rationale: The APU is protected by its own dedicated fire-detection system because it must operate safely and unattended when the main engines are shut down. It does not rely on the engine fire-detection loops or share a common airframe system for its fire warning.
Pipes, electrical cables, and associated components of a fire-detection system that pass through a fire zone should be
ACS code: AM.III.E
Correct answer: fire resistant.
Rationale: Components of a fire-detection system located in a fire zone, such as pipes, cables, and fittings, must be fire resistant so they continue to function long enough during a fire to provide warning. Fireproof is a higher standard reserved for items like firewalls, while fire retardant merely slows ignition and is insufficient here.
A continuous-loop (fire wire) detector element is installed so that it will
ACS code: AM.III.E
Correct answer: withstand the inertia, vibration, and thermal movement of normal operation.
Rationale: Per FAA-H-8083-32, a continuous-loop detector element is routed and clamped so it can withstand the inertia, vibration, and thermal movement of normal operation while still reliably sensing a fire. Its routing is dictated by the area it must protect, not by a fixed vertical or horizontal orientation.
Resistance- and capacitance-type continuous-loop fire detector elements are tested with a
ACS code: AM.III.E
Correct answer: megohmmeter and an ohmmeter.
Rationale: Per FAA-H-8083-32, continuous-loop fire detectors are checked for insulation resistance to ground with a megohmmeter (megger) and for element/loop continuity with an ohmmeter, confirming the element is neither shorted to the case nor open. A voltmeter or a general multimeter check does not properly verify both the high insulation resistance and the loop continuity.
The rubber grommets used in the support clips of a continuous-loop fire detector are provided to
ACS code: AM.III.E
Correct answer: cushion and support the detector element against vibration.
Rationale: Per FAA-H-8083-32, the rubber grommets in fire-detector support clips cushion and support the element, holding it securely while allowing for vibration and thermal movement without chafing. They are not provided to block heat transfer (which would defeat detection) or to electrically insulate the element.
Most aircraft fire extinguishing agents put out a fire primarily by
ACS code: AM.III.E
Correct answer: displacing or combining with the available oxygen to starve the fire.
Rationale: Per FAA-H-8083-32, most fire extinguishing agents work by smothering, excluding, or combining with the available oxygen so the fire is starved of the oxidizer it needs to sustain combustion. Creating more oxygen would feed the fire, and merely 'reducing oxygen' is less complete than displacing or combining with it to break the fire triangle.
When a fire detector element or its wiring is routed through a zone other than the one it monitors, that section must be
ACS code: AM.III.E
Correct answer: protected from the heat sources present in that zone.
Rationale: Per FAA-H-8083-32, where a detector element or its wiring passes through a zone it does not monitor, that section must be shielded from local heat sources so the system does not give a false fire warning from heat in the wrong zone. Such routing is permitted provided this protection is installed, so an outright prohibition is incorrect.
Operating the test switch of a continuous-loop fire detection system provides a
ACS code: AM.III.E
Correct answer: continuity check of the sensing loop.
Rationale: Per FAA-H-8083-32, pressing the test switch on a continuous-loop detector applies a test current through the sensing element and back, proving the loop is electrically complete. It confirms continuity (no broken element or open connection); it does not measure insulation resistance or electrical bonding, which are separate checks.
The two operating principles used by continuous-loop fire detection elements are
ACS code: AM.III.E
Correct answer: resistance and capacitance.
Rationale: Per FAA-H-8083-32, continuous-loop fire detection elements sense fire either by a decrease in the core material's resistance with rising temperature (resistance type, e.g., Kidde) or by a change in the element's capacitance with heat (capacitance type, e.g., Fenwal). Both effects are used, so naming only one—or substituting inductance—is incorrect.
What is the operating principle of the spot-type detector used in a fire detection system?
ACS code: AM.III.E
Correct answer: A bimetallic thermoswitch that closes its contacts when heated to a preset temperature.
Rationale: Per FAA-H-8083-32, a spot detector is a bimetallic thermal switch; when a preset high temperature is reached, the differing expansion of the two bonded metals snaps the contacts closed to complete the warning circuit. It is a temperature-actuated switch, not a thermocouple that generates current nor a resistance-core continuous element.
Two continuous-loop fire detection systems that will still signal a fire but fail their self-test when the detector element is broken are the
ACS code: AM.III.E
Correct answer: Kidde system and the Fenwal system.
Rationale: Per FAA-H-8083-32, the Kidde and Fenwal continuous-loop systems are resistance/capacitance types that can still raise a fire alarm even with a broken element, but the break prevents the integrity test current from flowing, so they fail the self-test. The thermocouple and Lindberg systems operate differently and are not the pair described.
Which fire detection system senses fire by comparing temperature rise against a reference temperature?
ACS code: AM.III.E
Correct answer: Thermocouple system.
Rationale: Per FAA-H-8083-32, a thermocouple fire-detection system uses an active (hot) junction exposed to the fire and a reference (cold) junction; the voltage produced depends on the temperature difference between them. It therefore responds to a rapid temperature rise above the reference, unlike a thermal switch or a continuous-loop element that reacts to a fixed overheat level.
A fire involving energized electrical equipment is classified as a
ACS code: AM.III.E
Correct answer: Class C fire.
Rationale: Per FAA-H-8083-32, fires involving energized electrical equipment are classified as Class C, where the live electrical supply is the principal hazard. Class B covers flammable liquids and Class D covers combustible metals, so neither applies to energized electrical equipment.
Most aircraft turbine engine fire extinguishing systems discharge the agent by means of
ACS code: AM.III.E
Correct answer: an electrically discharged explosive cartridge (squib).
Rationale: Per FAA-H-8083-32, most turbine-engine fire bottles are fired by an electrically initiated explosive cartridge (squib) that ruptures the container seal and releases the agent the instant the crew operates the discharge switch. This gives fast, remote, all-attitude operation that a manual valve or mechanical pushrod cannot reliably provide.
A fire detection system that signals an alarm based on the rate of temperature rise is the
ACS code: AM.III.E
Correct answer: thermocouple system.
Rationale: Per FAA-H-8083-32, a thermocouple detection system responds to the rate of temperature rise: a fast rise creates a large temperature difference between the active and reference junctions, generating enough voltage to trip the alarm, while a slow general heat soak does not. Thermal-switch and continuous-loop systems instead react to a fixed overheat level.
Why does one type of Fenwal fire detection system wire its spot detectors in parallel between two separate circuits?
ACS code: AM.III.E
Correct answer: So that a single fault can exist in the system without producing a false alarm.
Rationale: Per FAA-H-8083-32, wiring the spot detectors in parallel between two separate circuits means a single fault in one circuit alone will not complete the alarm path, so no false fire warning is produced. A genuine fire heats the detectors and closes both circuits together, giving a true alarm.
How does carbon dioxide (CO2) extinguish an aircraft engine fire?
ACS code: AM.III.E
Correct answer: It lowers the temperature of the air and displaces the oxygen.
Rationale: Discharged CO2 expands, cools the surrounding air, and—being heavier than air—blankets the fire and displaces the oxygen needed for combustion. Per FAA-H-8083-32, this smothering (oxygen-displacement) effect is the principal extinguishing mechanism; CO2 does not work mainly by blowing the fire out with spray pressure.
A fuel or oil fire is classified as a
ACS code: AM.III.E
Correct answer: Class B fire.
Rationale: Per FAA-H-8083-32, fuel, oil, and other flammable-liquid fires are classified as Class B. Class A covers ordinary solid combustibles such as wood or paper, and Class C covers energized electrical equipment, so neither fits a fuel or oil fire.
Which fire-extinguishing agent is the safest to use from the standpoint of toxicity and corrosion hazards?
ACS code: AM.III.E
Correct answer: Bromotrifluoromethane (Halon 1301).
Rationale: Per FAA-H-8083-32, Halon 1301 (bromotrifluoromethane) is the least toxic and least corrosive of the common halon agents, which is why it is favored for fixed installations. Halon 1211 and especially Halon 1202 are more toxic and present greater corrosion and health hazards.
The explosive cartridge (squib) in the discharge valve of a fire-extinguisher container is
ACS code: AM.III.E
Correct answer: a life-dated unit.
Rationale: Per FAA-H-8083-32, the explosive cartridge (squib) that fires the discharge valve contains a propellant charge that degrades with age, so it is a life-dated item and must be replaced at its expiration. It is electrically, not mechanically, fired, and it cannot be regarded as having unlimited service life.
A fire detection system operates on the principle of a buildup of gas pressure within a tube proportional to temperature. Which system does this describe?
ACS code: AM.III.E
Correct answer: Lindberg continuous element system.
Rationale: Per FAA-H-8083-32, the Lindberg (pneumatic/gas) continuous element contains a gas-filled tube; heat raises the gas pressure in proportion to temperature, and this pressure operates a diaphragm switch to signal a fire or overheat. The Kidde and thermal-switch systems work on resistance change or contact closure, not gas pressure.
How is the fire-extinguishing agent distributed in the engine section?
ACS code: AM.III.E
Correct answer: Through spray nozzles and perforated tubing.
Rationale: Per FAA-H-8083-32, the extinguishing agent is delivered around the engine compartment through spray nozzles and perforated (slotted) tubing positioned to flood the zone evenly. The bottle's own stored nitrogen pressure expels the agent, so separate fluid pumps or slinger rings are not used for distribution.
What is the principle of operation of the continuous-loop fire detector system sensor?
ACS code: AM.III.E
Correct answer: A core resistance material that prevents current flow at normal temperatures.
Rationale: Per FAA-H-8083-32, the continuous-loop element has a temperature-sensitive core whose resistance is very high at normal temperatures, blocking current; as the element heats, the core resistance falls sharply and current flows to trigger the alarm. It is not a bimetallic switch nor a one-shot fusible (melting) device.
The fire detection system that uses a single wire surrounded by a continuous string of ceramic beads in a tube is the
ACS code: AM.III.E
Correct answer: Fenwal system.
Rationale: Per FAA-H-8083-32, the Fenwal continuous element uses a single inner conductor surrounded by a continuous column of ceramic beads inside the outer tube; heat lowers the bead material's resistance to ground, completing the alarm circuit. The Kidde element instead uses two embedded wires, and a thermocouple uses dissimilar-metal junctions.
The fire detection system that uses two wires embedded in a ceramic core within a tube is the
ACS code: AM.III.E
Correct answer: Kidde system.
Rationale: Per FAA-H-8083-32, the Kidde continuous element has two wires embedded in a temperature-sensitive ceramic core inside the tube; as the core heats, its resistance between the two wires drops and current flows to signal a fire or overheat. The Fenwal element by contrast uses a single wire surrounded by ceramic beads.
A continuous-loop fire detector is what type of detector?
ACS code: AM.III.E
Correct answer: Overheat detector.
Rationale: Per FAA-H-8083-32, a continuous-loop detector responds when any part of its length reaches a set overheat temperature, so it functions as an overheat detector covering an area rather than a single spot. It does not work on rate-of-temperature-rise, and it is a length element rather than a single spot detector.
Which fire detection systems will detect a fire when an element is inoperative but will not test when the test circuit is energized?
ACS code: AM.III.E
Correct answer: The Kidde system and the Fenwal system.
Rationale: Per FAA-H-8083-32, the Kidde and Fenwal resistance/capacitance loops still detect a real fire even when the element is open, because the fire bridges the fault, but that same break stops the test current so the system fails its self-test. The thermocouple and Lindberg systems do not share this particular behavior.
After a fire is extinguished or an overheat condition is removed in an aircraft equipped with a Systron-Donner fire detector, the detection system
ACS code: AM.III.E
Correct answer: automatically resets.
Rationale: Per FAA-H-8083-32, the Systron-Donner (pneumatic) detector responds to gas pressure that rises with heat and falls again as the area cools, so once the fire or overheat is removed the pressure drops and the diaphragm switch reopens, resetting the system automatically. No manual reset or element replacement is required.
What is the function of a fire detection system?
ACS code: AM.III.E
Correct answer: To activate a warning device in the event of a powerplant fire.
Rationale: Per FAA-H-8083-32, a fire detection system's job is to sense a fire or overheat and activate a warning to alert the crew; it does not itself extinguish the fire or pinpoint its exact origin. Discharging the agent is the separate function of the fire-extinguishing system, operated by the crew after the warning.
What retains the nitrogen charge and fire-extinguishing agent in a high-rate-of-discharge (HRD) container?
ACS code: AM.III.E
Correct answer: A breakable disk or fusible disk.
Rationale: Per FAA-H-8083-32, in a high-rate-of-discharge container the agent and its nitrogen charge are held in by a frangible (breakable) disk that the squib ruptures on firing, plus a fusible disk that melts to relieve pressure safely if the bottle overheats. A pressure gauge or switch only monitors the charge; it does not retain it.
The use of water on a Class D fire
ACS code: AM.III.E
Correct answer: will cause the fire to burn more violently and can cause an explosion.
Rationale: Per FAA-H-8083-32, Class D fires involve burning metals that react violently with water, splitting it into hydrogen and oxygen and intensifying the fire, with a risk of explosion. Water therefore must not be used on metal fires; it is neither harmless nor effective even as a fine mist here.
On a typical large jet aircraft fire protection system, pulling out (or down) an illuminated fire handle commonly accomplishes which events?
ACS code: AM.III.E
Correct answer: Closes the fuel shutoff, closes the hydraulic shutoff, disconnects the generator field, and arms the fire-extinguishing system.
Rationale: Per FAA-H-8083-32, pulling the illuminated fire handle isolates the engine: it closes the fuel and hydraulic firewall shutoffs, trips the generator field to de-energize it, and arms the extinguisher ready for discharge. The crew oxygen supply is not shut off by this action, and the handle arms rather than automatically discharges the bottle.
The most satisfactory extinguishing agent for an electrical fire is
ACS code: AM.III.E
Correct answer: carbon dioxide.
Rationale: Per FAA-H-8083-32, carbon dioxide is the preferred agent for an electrical fire because it is a non-conductive gas that smothers the fire by displacing oxygen and leaves no corrosive or conductive residue. Carbon tetrachloride and methyl bromide are highly toxic and are not acceptable choices.
Which type of fire detector is commonly used in the power section of an engine nacelle?
ACS code: AM.III.E
Correct answer: Rate-of-temperature-rise detectors.
Rationale: Per FAA-H-8083-32, the power (hot) section of an engine nacelle normally uses rate-of-temperature-rise detectors, which respond quickly to the rapid heat increase of a fire. Carbon monoxide detectors and smoke detectors are unsuited to this high-temperature, high-airflow environment.
Which engine fire detection systems use actual heat as the input during a normal system test?
ACS code: AM.III.E
Correct answer: The thermocouple system and the pneumatic system.
Rationale: Thermocouple and pneumatic (gas-charged) continuous-loop systems are functionally tested by applying heat: a test heater warms the sensing element so the system responds to a genuine temperature rise, proving the entire sensing-to-warning chain. Resistance-type continuous loops such as Kidde and Fenwal are instead checked electrically by verifying element continuity and insulation resistance rather than by heating the element.
How are the discharge spray nozzles or rings of an engine fire extinguishing system checked for freedom from obstruction?
ACS code: AM.III.E
Correct answer: By blowing dry compressed air through them.
Rationale: Per FAA-H-8083-32, the distribution tubing and spray nozzles are checked for blockage by blowing dry compressed air through them and confirming unobstructed flow at every outlet. Discharging the system would expend the agent charge, and forcing water through the lines could introduce contamination and corrosion, so neither is used for a routine clearance check.
Which family of agents is used as the extinguishing agent in aircraft engine fire extinguisher bottles?
ACS code: AM.III.E
Correct answer: Halogenated hydrocarbons.
Rationale: FAA-H-8083-32 identifies halogenated hydrocarbons (the halons, such as Halon 1301) as the agents charged into engine fire extinguisher containers. These agents extinguish by chemically interrupting the combustion reaction and leave little or no residue. Water is not used in engine fire bottles, and the term refers to the whole halogenated family rather than a single brand name.
What is the principal advantage of a two-shot engine fire extinguishing system?
ACS code: AM.III.E
Correct answer: Either bottle can be discharged into either engine.
Rationale: In a two-shot system the bottles are cross-fed through the distribution plumbing so the contents of either bottle can be directed to whichever engine has the fire, providing a reserve discharge if the first shot does not extinguish it. It is not simply one bottle delayed in time, nor a single bottle discharged twice.
Which items are checked to verify that an installed fire extinguisher bottle is serviceable without removing it from the aircraft?
ACS code: AM.III.E
Correct answer: Check the discharge indicators, the expiration date, and the gauge pressure.
Rationale: An in-place serviceability check confirms the discharge indicator disks are intact (showing the bottle has not fired), the cartridge and agent are within their expiration date, and the gauge pressure is correct when temperature-corrected. Weighing the container requires removing it, so a weight check is not part of an in-place inspection.
Resistance-type continuous-loop fire detector elements are tested using which instruments?
ACS code: AM.III.E
Correct answer: A megohmmeter and an ohmmeter.
Rationale: Resistance-type continuous-loop elements are checked with an ohmmeter to verify loop continuity and with a megohmmeter (insulation tester) to verify insulation resistance between the conductor and ground. An ammeter or voltmeter does not provide the resistance and insulation measurements these elements require.
When checking the firing circuit of an installed fire extinguisher cartridge (squib), which instrument is used?
ACS code: AM.III.E
Correct answer: A low-current safety ohmmeter.
Rationale: The squib firing circuit is checked with a low-current safety ohmmeter that limits test current well below the squib's firing threshold, so continuity can be confirmed without accidentally igniting the cartridge. An ordinary multimeter or a lamp-and-cell could deliver enough current to fire the squib and must not be used.
When using a megohmmeter on a fault-free continuous-loop fire detector element, the correct practice is to
ACS code: AM.III.E
Correct answer: Apply it only briefly, because it can polarize the element.
Rationale: A megohmmeter applies a high test voltage that can polarize the temperature-sensitive core of a fire detector element and produce misleading readings if applied for a prolonged period, so insulation testing is kept brief. The instrument is not prohibited outright, but it must not be used in the extended manner of a normal insulation test.
Which three checks confirm the serviceability of a fixed fire extinguisher bottle while it remains installed in the aircraft?
ACS code: AM.III.E
Correct answer: Gauge pressure, discharge indicator, and thermal discharge disk.
Rationale: An installed bottle is verified without removal by reading the gauge pressure (temperature-corrected), confirming the discharge indicator (pop-up) is stowed, and confirming the thermal discharge indicator disk is intact. Weighing the container requires its removal, so a weight check is not one of the in-place inspections.
Omitting the crushable sealing washer when reassembling an engine fire detector wire connector will most likely
ACS code: AM.III.E
Correct answer: Allow moisture to enter the connector.
Rationale: The crushable washer environmentally seals the fire detector connector; leaving it out creates a path for moisture to enter, which can corrode the contacts and cause leakage or nuisance faults over time. The detector element's continuity and capacitance are not directly altered by the missing washer.