the learning never stops!

Fuel System

G500 Systems

If you've flown Gulfstreams for a while you will recognize a lot about the G500 fuel system. The basic system is a lot like what we had in the GV but many of the components have been upgraded many times over. In a nutshell, all of the fuel is in the wings which makes center of gravity control in this airplane very easy. Each wing feeds a hopper tank which makes fuel delivery to the engines very easy. The fuel pumps are designed to keep each engine happy as well as provide for crossflow (that you will rarely need) and that makes your fuel management chores very easy. Do you notice a trend here?

This is a work in progress



How it Works . . .


Fueling and Defueling System

Gravity (Overwing) Fueling System

Work in progress

Pressure Fueling and Defueling

Work in progress

Fuel Distribution System

Work in progress

Heated Fuel Return System

[G500 PAS, p. 7-20]

    images

    Photo: G500 Heated Fuel Return System(HFRS), G500 PAS, p. 7-20

    Click photo for a larger image

  • Prevents fuel tank temps from getting too cold during long range, high altitude flights; sends fuel heated by engine oil cooler back to wing tanks through spray bars inside the tanks.
  • Controlled by Fuel Return switch on OHPTS. The Auto mode defaults on power up.
  • Auto ON → Tank temp ≤ 0°C, Auto OFF → Tank temp > 10°C
  • Indications on fuel synoptic page (2/3) and OHPTS Fuel page.
  • Inhibited when fuel tank temp > 10°C, crossflow valve OPEN, engine thrust lever setting at high power, Fuel Return switch selected OFF, engine fire handle pulled / not stowed, engine power setting below idle, low fuel pressure, low fuel quantity, FADEC HFRS inhibit ON, engine fuel filter blocked, or an abnormal engine condition.

[G500 PAS, p. 7-23]

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    Photo: G500 HFRS OHPTS, G500 PAS, p. 7-23

    Click photo for a larger image

  • The Fuel Return Switch controls HFRS mode.
  • The default power up mode is Green "Auto" where: auto on when tank temperature ≥ 0°C and auto off when > 10°C.
  • A cyan "Auto" means there is failure within HFRS and the valve is not in the commanded position. You will get a L-R Fuel Return Fail CAS message.
  • An amber "Auto" means you have invalid HFRS data and the valve position is unknown.
  • A White "Off" inhibits the HFRS.

Fuel Quantity Management System

Work in progress

The Single Point Refueling Process

Unlike previous Gulfstreams we have an outside refueling panel, but we also need to have at least the ground service bus powered to take on fuel through the single point refueling receptacle. The batteries will do this, but if you are taking on a lot of fuel, you should have the APU running so as not to drain the batteries.

The Refueling Process

[G500 PAS, p. 7-8]

  • Fuel entering from the truck nozzle regulated at 35 to 55 psi.
  • I think the PAS means to say that the pressure should be regulated to between 35 to 55 psi.

  • Fuel flows through main fill line to a cross-fitting, then through left and right tank fill lines, through left and right refueling shutoff valves, and then into wing tanks.
  • Refueling shutoff valves will not open until:
    • the GSCP refueling FUEL/OFF switch is set to FUEL and the fuel truck provides fuel at or above 35 psi, or
    • The fuel load is entered and activated at a TSC and the fuel truck provides fuel between 30-50 psi.
  • Fuel flows through flapper valves in baffle ribs, to wing centerline, then flows towards outboard section of wing as centerline fills.
  • The Fuel Quantity Signal Conditioner (FQSC) receives data from fuel quantity sensors in wing tanks and electrically closes refuel shutoff valves when desired quantity is reached. The FQSC controls maximum imbalance during refueling to 200 lbs. When an imbalance exceeds 200 lbs, the FQSC closes the refuel shutoff valve in the higher tank, until the imbalance is below 200 lbs.
  • High Level Sensors in the upper portion of each wing provide overfill protection. If a high level sensor gets wet, the FQSC closes respective refueling shutoff valve and illuminates a HIGH LEVEL WARN light on the refueling panel.
  • It takes about 20 minutes to refuel a G500.
  • A Remote Fuel Shutoff switch on the Refueling Panel, the OHTPSs, or TSCs allow pilots to close the refuel shutoff valves.

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    Photo: G500 Single Point Refueling, G500 PAS, p. 7-8

    Click photo for a larger image

[G500 PAS, p. 7-24]

  • The Remote Fuel Shutoff switch is inhibited in flight.
  • The Remote Fuel Shutoff switch is normally white, allowing auto pressure fueling. This means the pressure fueling shutoff valves are ready to open if a fuel load is entered via GSCP or TSC and pressure is sensed at the valves.
  • The Remote Fuel Shutoff switch turns green if both pressure fueling shutoff valves are closed, which shuts off all fuel entering the tanks.

Setting a Fuel Load from the Refueling Panel

[G500 PAS, p. 7-9]

  • Select GND SVC BUS → ON (if GSB not powered)
  • Select PANEL POWER → ON (Illuminates fuel display, will indicate “TSC Control” if already programmed in TSC)
  • TSC fuel load will override GSCP set fuel load. GSCP load can override TSC load only if the GSCP Fuel / Off switch is set to Fuel and then a GSCP load is set that exceeds the TSC load.
  • INCREASE / DECREASE switch (Toggle to desired fuel load while FUEL / OFF switch is toggled OFF.
  • FUEL / OFF switch → FUEL (arms refuel system)

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    Photo: G500 Single Point Refueling, G500 PAS, p. 7-9

    Click photo for a larger image

Setting a Fuel Load from a TSC

[G500 PAS, p. 7-10]

  • Ensure the ground service bus is powered.
  • From TSC’s 1-4: Main Menu → Systems → Ground Service (Land on Refuel window and keypad appears, type in desired fuel load and press Enter).
  • From TSC 5: Main Menu → Systems → Fluid Quantity (Land on Refuel window and keypad appears, type in desired fuel load and press Enter.
  • Ensure GSCP FUEL / OFF switch set to OFF to prevents a higher GSCP entry.

  • images

    Photo: G500 Single Point Refueling, G500 PAS, p. 7-10

    Click photo for a larger image

The Gravity Refueling Process

You will probably never do this. But if you do, consider two fuel trucks to keep within the 1,000 lb imbalance limit.

[G500 PAS, p. 7-11]

  • Over-wing fueling adapter installed on top of each wing (Locking fuel cap, sleeve intake that extends into wing tank with an enclosed screen filter to prevent foreign object contamination.
  • Grounding jack located on refueling panel in front of right wing.
  • Location of fuel caps guarantees min of 2% expansion space available within each tank when gravity filled to overflowing, which makes it impossible to fill tank beyond rated capacity.
  • Fill each tank via its over-wing adapter, but remember the on-ground limitation of no more than a 1000 lb imbalance.

  • images

    Photo: G500 Gravity refueling, G500 PAS, p. 7-11

    Click photo for a larger image

The Defueling Process

What seems to go unsaid with any discussion of defueling is how rare it will be to find someone to do this. The only place I've been allowed to defuel is at a military base or at a manufacturer's service center where they have a place to hold your fuel and then return that same fuel to you when your service is complete. The issue is they cannot risk taking your fuel and using it on any other airplane.

[G500 PAS, pp. 7-12 to 7-13]

    Method 1 (For pilots)

  • Attach pressure fueling nozzle into adapter under right wing.
  • Apply suction from truck instead of pressure.
  • Pickup ports for defuel located in each hopper tank. Fuel is replenished to hoppers from fuel in wing tanks through hopper wall flapper valves.
  • This method doesn’t require electric power unless you need to track fuel quantity indications or monitor for fault detection.
  • This method will not completely empty tanks

  • images

    Photo: G500 Defueling method 1, G500 PAS, p. 7-12

    Click photo for a larger image

    Method 2 (For maintenance)

  • A drain fitting on right engine feed line uses fuel truck suction to draw fuel from right engine feed line.
  • Aircraft power is required due to use of crossflow valve and boost pumps. (Procedure in maintenance manual.)
  • Any Remaining Fuel

  • Any fuel remaining after suction defueling can be drained using hopper drain valves on bottom of the fuselage.

  • images

    Photo: G500 Defueling method 3, G500 PAS, p. 7-13

    Click photo for a larger image

Fuel Transfer System

Fuel Balancing

[AFM, §02-08-60]

  1. Fuel Balancing using the Fuel Crossflow

    1. FUEL CROSSFLOW . . . OPEN

    2. CAUTION

      THE ENGINE ONLY RUNS ON SUCTION FUEL FEED AT OR BELOW 20,000 FEET.

      ABOVE 20,000 FEET, THE ENGINE WILL RUN ERRATICALLY AND FLAME OUT IF THE FUEL CROSSFLOW IS NOT OPEN WITH AT LEAST ONE FUEL PUMP ON.

    3. FUEL PUMP(S) (Light Tank Side) . . . OFF (one at a time)

    4. Fuel Balancing . . . Monitor

    5. When the desired balance has been achieved:

    6. NOTE

      Fuel pump operation can be verified using fuel synoptic display.

      (1) FUEL PUMP(S) ON (one at a time)

      (2) FUEL CROSSFLOW CLOSE

  2. Fuel Balancing using the Fuel Intertank

  3. NOTE

    Balancing fuel using the fuel intertank requires the airplane to be placed in a sideslip condition. Use of autopilot is recommended.

    1. RUDDER TRIM (in the direction of heavy tank) . . . Apply

    2. FUEL INTERTANK . . . OPEN

    3. Fuel Balancing . . . Monitor

    4. When within 200 Pounds of the Desired Fuel Balance

    5. NOTE

      Due to fuel indicating system inaccuracies while in sideslip flight, stop the balancing process just prior to both tanks indicating equal. Stopping the process 200 lbs early results in balanced indications once sideslip has been removed.

      (1) FUEL INTERTANK CLOSE

      (2) RUDDER TRIM As required to hold zero sideslip

      (3) Fuel Balancing Check


The Components in Greater Detail . . .


Cockpit Controls and Indications

Fire handles and fuel control switches

[G500 PAS, p. 7-21]

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    Photo: G500 Fuel system center pedestal, G500 PAS, p. 7-21

    Click photo for a larger image

  • Fire handles shut off fuel at onside tank by closing the fuel shutoff valve, trips GCU shutting off electrics from generator, shuts off onside hydraulics in tail compartment.
  • Fuel control switches shut off fuel at engine.

Route fuel summary (TSCs)

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Photo: G500 Route fuel summary, TSC, G500 PAS, p. 7-28

Click photo for a larger image

[G500 PAS, p. 7-28] The Start Up page on the TSCs provides computed fuel burn, fuel reserve, total fuel required, and alternate fuel (when applicable).

Fuel Remaining (TSCs)

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Photo: G500 Fuel remaining, TSC, G500 PAS, p. 7-29

Click photo for a larger image

[G500 PAS, p. 7-29] The Phase of Flight En route page provides fuel remaining at the next waypoint, top of descent, and destination. The FPLN Flight Plan page gives leg fuel between each waypoint as well as the fuel remaining.

Fuel Management

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Photo: G500 Fuel management, TSC, G500 PAS, p. 7-30

Click photo for a larger image

[G500 PAS, p. 7-30] The FPLN Flight Progress page gives specific range (ground and air burn in nm/lb), fuel data (fuel flow in lb/hr), and time and range to reserve fuel.

Crossflow Valve

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Photo: G500 Crossflow valve, G500 PAS, p. 7-18

Click photo for a larger image

[G500 PAS, p. 7-18]

  • The normal position is closed, which isolates the left and right fuel tank boost manifolds.
  • The open position joins left an right fuel tank manifolds, allowing pressurized fuel from boost pumps to flow to both engines. You can balance fuel by having more pumps operating on one side than the other; when you do this a green arrow will be depicted over the valve on the synoptic.
  • The valve is controlled by a switch on the OHPTS.
  • A CAS message appears in gray, Fuel Crossflow Valve Open, which turns blue, Fuel Crossflow Valve Open after 5 minutes. Cycling the switch resets to the white CAS.
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Photo: G500 Fuel crossflow switch, G500 PAS, p. 7-26

Click photo for a larger image

[G500 PAS, p. 7-26]

  • The Crossflow Switch is a soft guarded switch, it requires a "Confirmation" or "Cancel" step prior to completion.
  • The Crossflow Switch is normally white (closed) and is activated green (open) to allow fuel movement between hoppers.

Defueling Suction Check Valves

Work in progress

Densitometer

Work in progress

Digital Fuel Gauging Probes

Work in progress

Ejector Pumps

Work in progress

Fuel Boost Pumps

[G500 PAS, p. 7-15]

  • There are four identical and interchangeable boost pumps located in each wheel well, attached to the aft of each hopper. There are 2 main (left and right) boost pumps powered by their respective Essential DC buses. There are 2 alternate (left and right) boost pumps powered by their respective Main DC buses. Each pump draws about 25 amps.
  • Each pumps delivers fuel at low pressure.
  • If the pumps fail, suction enables engine to siphon fuel below 20,000 feet.
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Photo: G500 Fuel pump switches, OHPTS, G500 PAS, p. 7-27

Click photo for a larger image

[G500 PAS, p. 7-15]

  • The fuel pump switches power up in a white "off" position. When turned on, they turn green.
  • During flight the fuel pump switches become soft guarded switches and require a "Accept" or "Cancel" confirmation step prior to changing.
images

Photo: G500 Fuel system automated functions, G500 PAS, p. 7-22

Click photo for a larger image

[G500 PAS, p. 7-22]

  • The left main fuel pump automatically comes on when the APU MASTER is selected ON.
  • The left and right main fuel pumps automatically come on when their respective engine fuel control switch is selected ON.
  • The left and right alternate fuel pumps automatically come on when their respective engine stabilizes after engine start.

Fuel Distribution Lines

Work in progress

Fuel Drain Valve Assembly

Work in progress

Fuel Probes with Compensator

Work in progress

Fuel Quantity Signal Conditioner (FQSC)

Work in progress

Fuel Shutoff Valves

Work in progress

Fuel Tank Access Panels

Work in progress

Fuel Tank Check (Flapper) Valves

Work in progress

Fuel Tanks

This has been the classic fuel tank setup since the GII. The dihedral of the wing funnels fuel inboard to fuel hoppers where the fuel pumps are. As fuel is burned the CG shifts slightly forward but CG is figured at Zero Fuel Weight so the shift in CG isn't a concern for preflight planning.

[G500 PAS, pp. 7-2 to 7-6]

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    Photo: G500 Wing and hopper tanks, G500 PAS, p. 7-2

    Click photo for a larger image

  • Total fuel capacity is 30,250 lbs.
  • There is a hopper inside each tank adjacent to the centerline rib with a capacity of 1,100 lbs.

  • images

    Photo: G500 Fuel baffle ribs and plenum tanks, G500 PAS, p. 7-3

    Click photo for a larger image

  • The wing tanks contain baffle ribs which divide the wing into a series of compartments that prevent sudden fuel movement.
  • There are small "weep holes" on the bottom of the baffle ribs to allow fuel below the flapper valves to move inboard.

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    Photo: G500 Fuel tank flapper valve, G500 PAS, p. 7-3

    Click photo for a larger image

  • There is a plenum (vent tank) the catches fuel entering the vent system. It allows for about a 2% fuel expansion. Fuel from the plenum is drawn back into the fuel tanks during stable flight.

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    Photo: G500 wing ventilation, G500 PAS, p. 7-4

    Click photo for a larger image

  • Wing ventilation protects the wing from over and under pressurization to allow for movement of air, fuel, and fuel vapors. The system is fully automatic and does not require any electrical power. It allows air to escape during refueling, allow fuel to escape if tanks are overfilled, and prevents the wing from collapsing due to negative pressure as fuel is consumed.
  • Ventilation components include:
    • Float valves which allow air to escape as fuel tanks fill, or air to enter as fuel is sent to the hoppers.
    • Pressure relief valves to pass fuel into vent stringers and then to the plenum.
    • The plenum, which is an empty chamber outboard of the outboard-most fuel bay.
    • Vent tubes (stringers) located near top of fuel tank which run the length of the wing and are connected to the plenum.
    • Fuel tank NACA vents located underneath each wing at the plenum, used to maintain a slight positive internal tank pressure during flight. This is where fuel is discharged if over filled.

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    Photo: G500 Fuel tank drainage, G500 PAS, p. 7-g

    Click photo for a larger image

  • There are four drains below the hoppers just forward of the wheel wells, as well as a drain at each plenum.
  • These valves are operated manually to allow water to be drained.

Fuel Ventilation System

Work in progress

Vent Stringer

Work in progress

Vent Valves

Work in progress

Bladder Vent Valves

Work in progress

Stringer Positive Pressure Relief Valve

Work in progress

Overboard Vent and Ram-Air Inlet (NACA Scoop)

Work in progress

Flame Arrestor

Work in progress

Positive/Negative Relief Pressure Relief Valve

Work in progress

Gravity Water / Fuel Drain System

Work in progress

Ground Service Control Panel (GSCP)

Work in progress

Hopper Tanks

Each hopper has a capacity of 1,100 lbs.

[G500 PAS, pp. 7-14 to 7-19]

    Hopper Tanks

  • Each hopper tank has two boost pumps (Main and Alternate) that deliver fuel at low pressure to the engines and the APU.
  • The PAS seems to have an error when it comes to fuel balancing on this page, saying it happens from one hopper directly to the opposite engine. Based on the diagram, it appears that fuel balancing through the cross flow valve happens from one boost pump manifold to the opposite manifold, or through the intertank valve from one hopper to the opposite hopper.

  • Fuel flows into the hopper via gravity → Through flapper valves and via Motive flow → Via fuel ejectors using boost pump pressure.
  • I don't this is quite right. I would rewrite this as follows: Fuel flows into the hoppers using motive flow from fuel ejectors which use boost pump pressure. This tends to pressurize the hopper itself. Absent this pressure (if both boost pumps have failed) fuel can flow into the hopper using gravity feed through the flapper valves.

  • The hopper should remain full during straight and level flight at any altitude, since engine consumption is less than ejector pump supply. During a maximum power, lightweight takeoff, the hopper will be depleted 40% during a 5 min climb to 25,000’ but once above 25,000’ or when the throttles are reduced, the hopper steadily replenishes to 100%.
  • If the fuel level in a hopper falls below 650 lbs, you will get a L-R Fuel Level Low CAS message. (That is your only indication.) Do not attempt a go around.

  • images

    Photo: G500 Hopper tanks, G500 PAS, p. 7-14

    Click photo for a larger image

    Fuel Flow Into Hoppers


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    Photo: G500 Fuel flow into hoppers, G500 PAS, p. 7-17

    Click photo for a larger image

  • Each hopper has three flapper valves to allow fuel from the wing tank.
  • Each hopper has an ejector pump the uses boost pump pressure to motivate fuel flow at low pressure but high volume, about 4,550 pph.
  • A gap above each hopper allows excess hopper fuel to spill back into the wing tank.

Intertank Valve

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Photo: G500 Intertank valve, G500 PAS, p. 7-19

Click photo for a larger image

[G500 PAS, p. 7-19]

  • The normal position is closed, which isolates the left and right hoppers.
  • The open position allows gravity flow between left and right fuel tanks via the hoppers.
  • The valve is controlled by a switch on the OHPTS.
  • A CAS message appears in gray, Fuel Intertank Valve Open, which turns blue, Fuel Intertank Valve Open after 5 minutes. Cycling the switch resets to the white CAS.
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Photo: G500 Fuel intertank switch, OHPTS, G500 PAS, p. 7-25

Click photo for a larger image

[G500 PAS, p. 7-25]

  • The Intertank Switch is a soft guarded switch, it requires a "Confirmation" or "Cancel" step prior to completion.
  • The Intertank Switch is normally white (closed) and is activated green (open) to allow fuel movement between hoppers.

Low and High Level Sensors

Work in progress

Overhead Panel Touchscreens (OHPTS)

Work in progress

Refuel Check Valves

Work in progress

Refuel / Defuel Adapter

Single Point Refueling Panel and TSCs

[G500 PAS, p. 7-7]

  • Located under right wing near Ground Service Control Panel (GSCP).
  • The Ground Service Bus must be powered to single point refuel.
  • The desired fuel load can be entered at the Refueling Panel located near single point fueling port or at any of 5 TSC’s in the cockpit. However with only GSB power it must be entered at either the Refueling Panel or TSC 5.
  • Once fuel load is set on a TSC, other locations are locked out. If the fuel load was set at the GSCP, a new TSC load will override the GSCP load.
  • An auto test of the system prior to each refuel will test the Refueling shutoff control (Green lights → Shutoff valves open, Red lights → Shutoff valves closed) and the High level sensors,

  • images

    Photo: G500 Single Point Refueling, G500 PAS, p. 7-7

    Click photo for a larger image

Refuel Shutoff Valves

Work in progress

Synoptic Page 2/3

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Photo: G500 Fuel synoptic 2/3 page, G500 PAS, p. 7-38

Click photo for a larger image

[G500 PAS, pp. 7-38 to 7-39]

  • Fuel level mismatch white arrows appear at a 500 lb imbalance and disappear when the imbalance decreases to below 100 lbs. The arrows turn blue above 1,000 lbs and a Fuel Imbalance CAS message appears. The arrows are amber and the deflection is full scale with a 1,000 lb imbalance on the ground or 2,000 lb imbalance in flight, with an amber Fuel imbalance CAS message.
  • Fuel flow mismatch white arrows appear when FF ≥ 40 PPH and fully deflect when > 300 PPH. The arrows disappear at 40 PPH, if a fuel flow sensor becomes invalid, or the power mode is TO/GA, FLEX, or CLIMB.
  • The Heated Fuel Return System lines are white when the fuel return valve is commanded closed, green when commanded open, blue when the valve is not in the commanded position, and amber when the position is unknown.
  • In general, white means it isn't operating, green means it is operating and normal, amber means it is abnormal, and red means the fire handle has been pulled.
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Photo: G500 Fuel synoptic 2/3 page, G500 PAS, p. 7-39

Click photo for a larger image

Touchscreen Controllers (TSC)

Work in progress


Limitations and Abnormal Procedures


Limitations

Maximum Fuel Imbalance

[G500 AFM, §01-03-80]

  • Takeoff: 1,000 lb.

  • In Flight: 2,000 lbs.

Usable Fuel Capacities

[G500 AFM, §01-28-10]

  • Gravity refueling: 22,500 lbs

  • Pressure refueling:

    • Pressure refueling: 30,250 lbs; 4,515 gallons
    • If either tank quantity exceeds 15,125 lbs, the affected side and total fuel quantities turn to white dashes.

Fuel Pumps

[G500 AFM, §01-28-20]

  • Select operable fuel pumps on for all phases of flight unless balancing fuel.

Fuel Tank Temperature

[G500 AFM, §01-28-30]

  • Maximum supplied to engine: 55°C up to 40,000' decreasing linearly to 34°C at 51,000'

  • Minimum: -37°C with > 5,000 lbs, -30° with < 5,000 lbs

  • In flight if fuel temp ≤ 30°C and < 5000 lbs total remaining, descend to an altitude where SAT ≥ -60°C, minimum speed is 0.80M.

Abnormal / Emergency Operations

References

Gulfstream GVII-G500 Airplane Flight Manual, Revision 1, August 31, 2018

Gulfstream GVII-G500 Production Aircraft Systems, Revision 1, Oct 1, 2018

Revision: 20190527
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