Fire Protection System

Gulfstream GVII

Eddie sez:

The fire protection system is fairly standard for a Gulfstream with a few exceptions. The engine, for example, is divided into two zones and you only use the fire bottles on one of them. Like before, some systems are hardwired and others go through computers; but in the G500 it is more clear which are which.

For a quick refresher or a good intro, be sure to see Ivan Luciani's notes: G500 Fire Protection System Notes.

There are also a few flash cards here: Quizlet.

Everything here is from the references shown below, with a few comments in an alternate color.


Photo: G500 Engine nacelle fire protection, PAS, p. 5-2
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Last revision:


APU Overheat and Fire Detection

APU Enclosure

[PAS, p. 5-4] Titanium box like enclosure which can contain a fire for 15 minutes. If not extinguished within 15 minutes, damage to structure or other systems may occur.


Photo: G500 APU fire detection, PAS, p. 5-4
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APU Compartment Fire Detector

[PAS, p. 5-4] APU Overheat / Fire Detection System

  • Distinctly different from engine fire detection system.

  • Consists of a 7’ helium filled tube secured to the top of the APU enclosure. As temperature increases, the gas expands and pressure in the tube rises, triggering pressure switches in the sensor element. An average temperature rise over the entire tube indicates an overheat. A large temperature rise on a small length of the tube indicates a fire. Outputs are sent to DCN and APU ECU.

  • The data concentration network (DCN) determines when APU overheat/fire condition exists, sending APU overheat/fire indication to flight deck.

    • Overheat indication: APU Exceedance (U)

    • Fire indication: "FIRE" capsule light, APU Fire (U), and APU Fail. On the ground an APU fire bell will sound.

    • Sends fire signal to APU engine control unit (ECU); ECU closes APU fuel supply valve to shut down APU; Closes load control valve; Shuts off APU generator; Closes APU inlet door.

  • Detection system constantly monitored; DCN activates CAS message for helium leak (loss of pressure); APU Fire Detector Fail.

APU Fire Extinguishing


Photo: G500 APU fire extinguishing, PAS, p. 5-5
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[PAS, p. 5-5] APU Fire Extinguishing system

  • Fire extinguisher discharge switch (guarded), located on APU control panel. Lift guard then press and release. Discharges left fire bottle halon into APU compartment, illuminates FIRE EXT DISCHD on the switch capsule. Only one shot available, the right bottle for main engines only.

  • Available down to main battery power only.

  • Bottle discharge generates CAS message L/APU Fire Bottle Dischrg.

  • Both CAS message and capsule discharge indications remain active until fire bottle is recharged. Note: START/STOP switchlight not illuminated because APU ECU shuts down the APU automatically when fire detected.


Photo: G500 APU fire extinguisher control panel, PAS, p. 5-14
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[PAS, p. 5-14] APU Fire Extinguisher Control Panel

  • Bottom right of overhead panel, left of APU Control

  • “FIRE” Capsule light illuminates when APU fire is detected, causes ECU to initiate immediate APU protective shutdown, closes load control valve, shuts off APU generator, closes APU inlet door, extinguishes when APU fire no longer detected.

  • APU fire extinguisher discharged switch. Cross-hatched in orange and amber, guarded switch. When pressed in, illuminates “FIRE EXT DISCHD” capsule. Turns black again when released, discharges left fire bottle into APU compartment. L/APU Fire bottle Dischrg.

Engine Overheat and Fire Detection

Engine Fire Zones


Photo: G500 Engine fire extinguishing control, PAS, p. 5-15
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[PAS, p. 5-15] Engine Fire

  • Fire detected in Zone 1 of engine by both fire detect loops or by a single loop if other loop determined to be faulty via logic in DCN.

  • Indications: 3 chime aural warning, 5 Lights (2 Red master WARN indications, fire handle, fuel control switch), and 2 CAS messages (R Engine Fire (U) and Reduce R Throttle To Idle).

  • Fire handles (2) → Left and right

    • Located at left and right front of center pedestal

    • Locked in stowed position by electrical solenoid; solenoid is released when fire is detected; can manually release via button under handle

    • When pulled → Shuts off fuel at applicable shutoff valve at fuel hopper, electrics at applicable IDG GCU, and hydraulics at applicable hydraulic shutoff valve.

    • When rotated: discharges fire bottle 1 or 2 into Zone 1 only. Always rotate to discharge 1 first (outboard). Uses right bottle saving left for APU if possible. Discharge 2 if fire indications persist for 30 secs


Photo: G500 Engine core fire, PAS, p. 5-16
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[PAS, p. 5-16] Engine Core Fire

  • Fire detected in Zone 2 of engine by both fire detect loops or by a single loop if other loop determined to be faulty by logic in DCN.

  • Indications: 3 chime aural warning, 5 Lights (2 Red master WARN indications, fire handle, fuel control switch), and 2 CAS messages (R Engine Core Fire).

  • Fire handles: DO NOT ROTATE for an engine core fire (fire bottles discharge into Zone 1 only).

Engine Fire Extinguishing

Fire Extinguishing Bottles


Photo: G500 Fire extinguishing bottles, PAS, p. 5-3
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[PAS, p. 5-3] Fire extinguishing bottles:

  • Located in the tail compartment.

  • Left and right fire bottle can be discharged into either engine, zone 1 only. (Zone 2 fire controlled by fluid shutoff, drainage and ventilation.)

  • Filled with non-toxic, non-corrosive Halon 1301.

  • Right bottle is labeled DISCH 1 on fire handles. Always discharge first.

  • Left bottle can also be discharged into APU and is labeled DISCH 2 on fire handles. It is used only if right bottle alone not sufficient and is saved for APU if right bottle was sufficient for the engine.

  • Available down to main battery power only.

  • Bottle discharge generates CAS messages:

    • L/APU Fire Bottle Dischrg

    • L-R Fire Bottle Dischrg

Equipment Area Overheat Detection

Thermal Switches

[PAS, p. 5-6] Overheat Detection System

  • 10 Areas monitored by thermal switches:

    • 250°F trip point areas (5), generally bleed air related

      • Left aft floor hot

      • Right aft floor hot

      • Aft equipment hot

      • Left pylon hot

      • Right pylon hot

    • 150°F trip point areas (5), generally electrical related

      • Left Electronic Equipment Rack (LEER)

      • Right Electronic Equipment Rack (REER)

      • Forward under floor area

      • Forward baggage EER

      • Aft baggage EER

Baggage Compartment Smoke Detection and Evacuation

Smoke detectors


Photo: G500 Smoke detectors, PAS, p. 5-7
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[PAS, p. 5-7] Smoke Detectors

  • 1 Standard: Baggage compartment

  • 4 Optional: Cabin, Galley, Aft lavatory, Forward lavatory.

  • Operation. If an optical sensor senses smoke then issues CAS message through DCN. If two independent temperature monitors sense more than 212°F. Resulting CAS messages: Fwd-Aft Lav Smoke, Lav Smoke (for single lav configuration), Baggage Smoke, Cabin Smoke, and Galley Smoke.

  • Service LED lights: Performs BIT test every 5 minutes with two lights: green / red, and amber. Flashing green is normal, call maintenance for any other indication.

Emergency smoke evacuation valve handle


Photo: G500 Smoke evacuation panel, PAS, p. 5-8
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[PAS, pp. 5-8 to 5-9] Emergency smoke evacuation valve handle:

  • When selected to VENT SMOKE:

    • Baggage compartment air vented overboard through baggage compartment ceiling vent.

    • Integrated door stop for interior baggage door. Use this prior to selecting VENT SMOKE, it will keeps door open 2” for use with “Fire/Smoke/Fumes in Baggage Compartment” procedure.
    • I'm not sure about this. In previous Gulfstreams opening this door 2" in this situation will depressurize the airplane.

    • If interior baggage door is closed a significant pressure differential develops vs cabin. When this pressure differential is sensed the baggage compartment ventilation valve closes and additional airflow to compartment also shutoff. This allows the compartment to completely depressurize, starves compartment fire of oxygen, and the interior baggage door becomes pressure bulkhead. It will be impossible to open without equalizing pressure first. CAS message: Baggage Compt Low Press.

  • When selected to CLOSED:

    • Blocks baggage compartment vent line

    • Reopens baggage compartment ventilation shutoff valve

    • Restores airflow to compartment. Internal baggage door handle → open position, opens 2 square inch vent and allows cabin air to expedite repressurization.

  • Normal operations. The emergency smoke evacuation valve handle is CLOSED and conditioned air is routed through the baggage compartment shutoff valve. The baggage compartment is pressurized slightly higher than the cabin to induces air flow from compartment to cabin through a valve in top left of internal baggage door. The valve is hinged to allow airflow into cabin only and will close if baggage compartment depressurizes.

  • Baggage compartment vent valve sense test port. If a differential pressure (compartment vs cabin) is sensed greater than 4 psid: Baggage Compt Low Press.

  • Baggage compartment light switch. A red guarded switch that allows turning on compartment light without entering. The ground service bus must be powered.

  • Baggage compartment communication jacks. Allows communication with cockpit. To use must select H’MIC on TSC #5 comm page. When using protective breathing equipment (PBE) may have to place boom mic against throat.

Portable fire extinguishers


Photo: G500 Portable extinguishers, PAS, p. 5-10
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[PAS, p. 5-10] Portable fire extinguishers

  • Red Halon Extinguishers (3): a 2.5 lb unit is mounted on forward face of cockpit bulkhead behind pilot. a 13 lb unit mounted in aft lavatory left hand bottom cabinet, the third location varies depending on galley location. These are for class B and C fires (flammable liquids, oil, grease-fueled, and electrical.)

  • Green Water Extinguisher: mounted under halon extinguisher near galley. For Class A fires (wood, paper, cloth, trash, and plastics.)

System Tests

APU and Engine Fire Test Switch


Photo: G500 APU and engine fire test, PAS, p. 5-11
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[PAS, p. 5-11] APU and Engine Fire Test Switch

  • Located on any OHPTS in 2 places: IRS/APU/Batt page → Fire Test (Only on initial aircraft power up) and DU Ctrl/Test Page → System Test → Fire Test.

  • Accomplishes test for both APU and engines. Checks fire detection indications only (fire detection functionality continuously monitored). Produces a master warning aural tone (3 chimes). Verify 13 indications for proper test:

    • Overhead APU “fire” light illuminated

    • Master warning light illuminated (2)

    • APU Fire (U)

    • APU Fail

    • L-R Engine Core Fire (Count L-R as 2)

    • L-R Engine Fire (U) (Count L-R as 2)

    • Fire handle lights illuminated (2)

    • Fuel control fire lights illuminated (2)

  • When on the ground the test activates an APU fire bell sound in nose wheel well

Master Test Switch


Photo: G500 Master test switch, PAS, p. 5-12
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[PAS, p. 5-12] Master Test Switch

  • Located on any OHPTS → DU Ctrl/Test Page.

  • Latching switch.

  • Icons below Master Test switch indicate tests performed: Annunciator lights, Smoke detect, Passenger oxygen, Equipment overheat.

  • All Cockpit annunciated lights illuminate except: Fire handles (2), Fuel control fire lights (2), Pass oxygen ON light (right console), ELT ON Light (right console).

  • 15 CAS messages displayed (14 if only 1 lavatory installed), as shown above.


Photo: G500 System test page, PAS, p. 5-13
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[PAS, p. 5-13]

  • System Test Page, located on any OHPTS → DU Ctrl/Test Page → System Test. Allows selection of individual fire protection system tests. Press and hold for smoke detect, equipment overheat, and fire tests.

  • Smoke Detect Test. Checks functionality of detectors, CAS messages displayed for smoke circuits being tested: Baggage Smoke, Bag Smoke Det Fault. Optional Equipment: Cabin Smoke, Fwd-Aft Lav Smoke, Galley Smoke, Lav Smoke, Cabin Smoke Det Fault, Fwd-Aft Lav Smoke Det Fault, Galley Smoke Det Fault, and Lav Smoke Det Fault.

  • Equipment Overheat Test. Checks CAS indication function for all 10 overheat areas

    • L-R Pylon Hot

    • L-R Aft Floor Hot

    • Aft Equipment Hot

    • Aft Baggage EER Hot

    • Fwd Floor Area Hot

    • L-R EER Hot

    • Fwd Baggage EER Hot

See Also:

Gulfstream GVII-G500 Production Aircraft Systems, Revision 3, July 15, 2019