Fuel System

Gulfstream GVII

Eddie sez:

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?

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

How it Works . . .

The Components in Greater Detail . . .

Limitations and Abnormal Procedures . . .

Last revision:

2020-03-31


How it Works . . .


Fueling the airplane

The airplane is normally refueled using a Single Point Refueling System receptacle located under the right wing from a source (usually a fuel truck) with pressure regulated at 35 to 55 psi. The onload can be controlled at the Ground Service Control Panel (GSCP) just forward of the right wing. The fuel source should be grounded to the airplane; there is a grounding jack at the GSCP. The fueling can also be controlled at any of the Touch Screen Controllers (TSC) in the cockpit. Single Point Refueling requires the Ground Service Bus be powered. If only the Ground Service Bus is powered, the refuel can only be controlled by the GSCP or TSC 5. The GSCP can override the TSC, but only if the GSCP fuel load exceeds that on the TSC.

A full load of fuel can be uploaded using the Single Point Refueling System. That is 30,250 lbs for a G500 and 41,730 lbs for a G600.

Some operators have found that refueling while powering the system with aircraft batteries can be too taxing on the batteries. They recommend refueling only while on external or APU electrical power.

A Fuel Quantity Signal Conditioner (FQSC) keeps the fuel balanced during fueling to within 200 lbs by shutting off fuel from the high tank when the imbalance exceeds 200 lbs. The FQSC shuts off the fuel when the desired quantity is reached, when the high level sensors are actuated or when the Remote Fuel Shutoff switches on any OHPTS, any TSC, or the GSCP is actuated.

It takes about 20 minutes to put a full load of fuel on a G500, about 26 minutes for a G600.

The Refuel System Fail CAS message may appear when pressure refueling aircraft. This is a nuisance message that goes away once refueling begins.

Sometimes when powering up the aircraft, the Fuel Level Low, L-R CAS is present and the synoptic fuel levels will be amber even though the fuel level is well above fuel low levels. If the aircraft has been sitting for a while, the fuel will gradually migrate from the hoppers to the wings due to differences in tank level. This is normal. The fuel will quickly fill the hoppers once the boost pumps are turned on during engine start. If desired, the pilots can turn on the boost pumps prior to engine start to move fuel to the hoppers.

The aircraft can also be refueled over the wings using a Gravity Fueling System, but the maximum fuel load will be reduced to 22,500 lbs in the G500, 22,600 lbs in the G600. The fuel is loaded through fueling adapters on the top of each wing. There is a grounding point near each adapter. It will be up to the operator to ensure the fuel imbalance does not exceed 1,000 lbs.

Storing the Fuel

There are two Fuel Tanks, one in each wing. Total capacity is 30,250 lbs in a G500, 41,730 lbs in a G600. Each tank has a fuel hopper inside the tank, adjacent to the centerline rib, with a capacity of 1,100 lbs.

Each tank is baffled to prevent sudden fuel movement. The dihedral of the wing pushes fuel inboard through flapper valves and weep holes a the bottom of the baffle ribs.

Each wing is ventilated to prevent under and over pressurization and to account for the movement of fuel and air in the tanks. Float valves allow air into the tank to displace fuel. There is a plenum outboard each fuel tank to catch fuel entering the vent system and to allow a 2% fuel expansion. Each plenum includes a NACA vent to provide a slight positive pressure inside the tank and also to discharge fuel if over filled. There is a second NACA vent, outboard the fuel tank plenums, in dry bays used for flight control equipment.

There are four drains below the hoppers and a drain at each plenum.

Each hopper should remain full during straight and level flight due to gravity flowing through three flapper valves from the fuel tank as well as intake from an ejector pump which uses boost pump pressure. The ejectors will provide about 4,550 pph, more fuel than an engine consumes, except during a maximum thrust, light weight takeoff. The hopper will be depleted 40%, for example, during a 5 minute climb to 25,000' but at that point the hopper will steadily be replenished. A gap above each hopper allows excess fuel to return to the wing tank.

Preventing the fuel from freezing

Heated Fuel Return

A Heated Fuel Return System doesn't heat the fuel in the tanks but slows the rate of cooling to prevent the fuel from getting too cold. It does this by sending fuel heated by the engine oil cooler back to the wings using spray bars inside the tanks.

The system is automatic, activating when fuel in the tanks is less than or equal to 0°C, deactivating when the fuel in the tanks exceeds 10°C. The system will be inhibited if the crossflow valve is open, engines are at a high thrust or below idle, the system is selected off, or if there is an abnormal engine condition.

Keeping the fuel balanced

Fuel Balancing

Fuel must be balanced within 1,000 lbs. for takeoff and 2,000 lbs otherwise, but you are not allowed to balance the fuel while inflight until it gets to the point a CAS message is generated. The primary means of balance fuel is through a Crossflow Valve.

The crossflow valve is located between the left and right fuel tank manifolds and when opens allows fuel to move from one side to the other if there are more boost pumps operating on one side. The valve is normally closed but can be opened by a switch on the OHPTS. The valve itself is powered by the L ESS DC bus and when open will generate a Fuel Crossflow Valve Open CAS message in gray. After five minutes it becomes a Fuel Crossflow Valve Open CAS message in cyan.

The procedure is given in AFM, §02-08-60, and includes the warning that the engine will only read on unboosted pressure (suction feed) at or below 20,000 feet. The steps are to open the crossflow valve, turn of the fuel pumps on the light tank side one at a time, and monitor the fuel movement. Once balanced, the fuel pumps are returned to on, one at a time, and the crossflow valve is closed.

A secondary fuel balancing method is through an Intertank Valve, which is located between each hopper. It is controlled by a switch in the OHPTS. The valve itself is powered by the R ESS DC bus and when open will generate a Fuel Intertank Valve Open CAS message in gray. After five minutes it becomes a Fuel Intertank Valve Open CAS message in cyan.

The procedure is given in AFM, §02-08-60, and includes the warning that the engine will only read on unboosted pressure (suction feed) at or below 20,000 feet. The steps are to apply rudder trim in the direction of the heavy tank, open the intertank valve, and monitor the fuel movement. The procedure recommends the transfer be stopped 200 lbs before the desired balance.

Getting the fuel to the engines and APU

While fuel in the hoppers can be drawn by suction from the engines up to 20,000 feet, the fuel is normally pressurized by Fuel Boost Pumps. There are four identical and interchangeable boost pumps in the aft end of each hopper, accessible through the wheel wells. Each hopper has a main boost pump powered by the onside DC ESS bus, and an alternate boost pump powered by the onside MAIN DC bus. Each pump draws about 25 amps and delivers fuel at low pressure.

The left main pump automatically comes on when the APU MASTER is selected ON. Both main pumps automatically come on when their respective engine fuel control switch is selected ON. The alternate pumps come on when their respective engines stabilize after engine start. The pumps do not go OFF automatically after engine shutdown.

The fuel passes through Fuel Shutoff Valves (SOVs) located just after of each hopper and powered by the onside ESS DC bus. The engine valves respond to the position of the onside fire handle, the APU SOV to the APU ECU.


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
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  • 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
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[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
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[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
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[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
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[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 and 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
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[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 System

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Photo: G500 Defueling method 1, G500 PAS, p. 7-12
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[G500 PAS, p. 7-12] Ensure truck storage capacity exceeds amount to be defueled. Three methods:

  1. Method to be used by pilots: attach pressure fueling nozzle into adapter under right wing, apply suction from truck instead of pressure. Pickup ports for defuel are located in each hopper tank, fuel is replenished to hoppers from fuel in wing tanks through hopper wall flapper valves. This doesn’t require electric power unless following required fuel quantity indications or needing fault detection. This method does not result in empty tanks.
  2. Maintenance procedure: 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.
  3. Any fuel remaining after suction defueling can be drained using hopper drain valves on bottom of fuselage.

You will be hard-pressed to find someone willing to take fuel off your airplane outside of a service center with facilities to do just that. Out of about ten attempts to find someone outside of a service center or when I was in the Air Force, I was successful once. The FBO had a truck available and took 1,000 gallons from us with the understanding we had to take in back within five days. They had to run a full spectrum of tests on the fuel and had the fuel failed we would have had to pay for doing a complete cleanup of the tank on the truck. If we were unable to take the fuel within the agreed upon period, we would have had to pay for the disposal.

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

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Photo: Fuel shutoff valves, G500 PAS, p. 7-16
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[G500 PAS, p. 7-16]

  • There are three fuel shutoff valves located in the wheel well, attached to the aft portion in each hopper. There is one for each engine and one for the APU.
  • The engine SOVs are operated by the respective fire handles, the APU SOV by the APU Engine Control Unit (ECU).
  • During the exterior preflight inspection the engine SOVs are checked to ensure the yellow rectangles are in the OP (open) position.

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
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  • 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.

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    Photo: G500 Fuel baffle ribs and plenum tanks, G500 PAS, p. 7-3
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  • 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
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  • There is a plenum (vent tank) that 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
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  • 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
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  • 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

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Photo: Wing ventilation, PAS, p. 7-4.
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[G500 PAS, p. 7-5]

  • The ventilation system protects the wing from over and under pressurization within the wing and allows the free movement of air, fuel vapors, and fuel.
  • The system is fully automatic and doesn't require any electrical power.
  • The system also prevents wing rupture from positive pressure during refueling by allowing air to escape as fuel fills the tanks and by allowing any overflow of fuel from the tanks if a malfunction leads to over fueling.
  • Finally, the system prevents wing collapse due to negative pressure when fuel is consumed by displacing fuel with ambient air as fuel is sent to the hoppers.
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Photo: Wing ventilation, PAS, p. 7-5.
Click photo for a larger image

[G500 PAS, p. 7-5]

  • Float valves provide passage for air to escape as fuel fills tanks and displaces fuel with ambient air as fuel is sent to the hoppers.
  • Pressure relief valves allow for fuel to escape tanks if overfilled during refueling or when balancing fuel. They pass into vent stringers and then to the plenum.
  • The Pressure Relief Vent Valve (PRVV) is a dual action relief valve that relieves positive and negative pressures if a NACA vent clogs.
  • The plenum is an empty chamber located outboard of outboard-most wet bay where fuel can move in and out via vent system due to over fueling or expansion due to temperature. The plenum allows for 2% fuel expansion (when combined with vent tubes). The plenum should be drained of any fuel prior to takeoff via a drain valve in the bottom.
  • Vent tubes or stringers are located near top of the fuel tanks just below upper skin, running the length of each wing and connected to the plenums.
  • Fuel tank NACA vents are located underneath each wing at plenum, designed to help maintain slight positive internal tank pressure in flight. Fuel is discharged here as well to relieve excess pressure if over fueled or during improper fuel balancing. Fuel is forced through pressure relief valves, through vent stringers to the onside plenum, then overboard through the NACA vent. This is normally prevented by fueling shutoff valves closing when either the preselected fuel load is reached (via Fuel Quantity Signal Conditioner) or when the high level sensors get wet. A flame arrestor installed in NACA vent lines suppress any flames entering from outside.
  • Equipment bay NACA vents are located underneath each wing on outermost equipment dry bay. They provide ventilation for dry bays where flight control equipment is housed

Fuel / Water Drain System

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Photo: Fuel / Water Drain, PAS, p. 7-6.
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[G500 PAS, p. 7-6]

  • Four drain valves are located underneath [the] fuselage forward of the wheel wells: one for each hopper and one for the main portion of each wing tank.
  • There are two drain valves located at the plenums, exposed on lower wing skin near fuel NACA vent. These should be drained of any fuel prior to takeoff and are operated manually.
  • The drains allow for drainage of water due to rain seepage, condensation, or contamination.
  • Water accumulates at the bottom of fuel tanks because water is heavier than fuel.
  • This is a pilot responsibility if maintenance is not available.
  • Pilot Preflight: check to ensure not leaking and access doors are secure.

Gravity Fueling System

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Photo: Gravity Refueling, G500 PAS, p. 7-11
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[G500 PAS, p. 7-11] There is an over-wing fueling adapter installed on the top of each wing with a locking fuel cap and a sleeve intake that extends into wing tank. The adapter includes a screen filter to prevent foreign object contamination. There is a grounding jack located on refueling panel in front of right wing. The location of each fuel caps guarantees a minimum of 2% expansion space is available within each tank when gravity filled to overflowing. That makes it impossible to fill a tank beyond rated capacity. Fill each tank via its over-wing adapter but be mindful of the on-ground limitation of a 1000 lb. maximum imbalance. During the pilot's Interior Preflight Inspection: Check fuel tank caps are secure. The maximum fuel load gravity refueling is 22,500 lbs. (G500) and 22,600 lbs. (G600)

Heated Fuel Return System

[G500 PAS, p. 7-20]

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    Photo: G500 Heated Fuel Return System(HFRS), G500 PAS, p. 7-20
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  • 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.
    • I heard in class that the HFRS only comes on above 30,000 feet or when N2 is below 58.5% -- I don't see this in writing anywhere. I used to suspect everything I hear from an FSI instructor as hearsay until proven, but this was from a member of the design build team.

[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.

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 think 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.

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    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
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  • 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
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[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.

Refuel / Defuel Adapter

[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.

Single Point Refueling System

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Photo: Single Point Refueling, G500 PAS, p. 7-7
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[G500 PAS, p. 7-7] A single point refueling receptacle is located under the right wing near Ground Service Control Panel (GSCP). The Ground Service Bus must be powered to single point refuel. You can enter desired fuel load in 6 locations: at the Refueling Panel located near single point fueling port or at any of the five TSC’s in the cockpit. But with GSB power only you can only use the Refueling Panel and TSC 5. Once the fuel load is set on a TSC, the other location’s ability to adjust is locked out. If a fuel load is set at the GSCP, a new TSC load will override GSCP load. The GSCP load can override a TSC load only if the GSCP Fuel / Off switch is set to Fuel and if the GSCP load exceeds the TSC load. The system auto tests prior to each refuel. Refueling shutoff control: Green lights mean the shutoff valves are open, Red lights means shutoff valves are closed.

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Photo: Single Point Refueling, G500 PAS, p. 7-8
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[G500 PAS, p. 7-8] Fuel entering from truck nozzle should be regulated at 35 to 55 psi. It flows through main fill line to a cross-fitting, then through the left and right tank fill lines, through left and right refueling shutoff valves, and then into wing tanks. Refueling shutoff valves will not open when GSCP refueling until the FUEL / OFF switch is set to FUEL and the fuel truck presents 35 psi or more. When TSC refueling the valves open once a fuel load is entered and activated and the fuel truck presents between 30 and 50 psi. Fuel flows through flapper valves in baffle ribs, to wing centerline, then towards the outboard section of wing as centerline fills. The Fuel Quantity Signal Conditioner (FQSC) receives data from fuel quantity sensors in wing tanks, electrically closes refuel shutoff valves when the desired quantity is reached, controls max imbalance during refuel to 200 lbs. When the imbalance exceeds 200 lbs the FQSC closes the refuel shutoff valve in the higher tank until the imbalance is less than 200 lbs.

[G500 PAS, p. 7-8] There are High Level Sensors located in the upper portion of each wing to provide overfill protection. If a high level sensor gets wet, FQSC closes respective refueling shutoff valve and the HIGH LEVEL WARN lights illuminate yellow on the refueling panel.

[G500 PAS, p. 7-8] The approximate refueling time for a G500 is 20 mins and for a G600 is 26 mins.

[G500 PAS, p. 7-8] Remote Fuel Shutoff switches on OHPTS 1-3, the refuel panel, and on TSCs 1-5 allows the pilot to close the refuel shutoff valves.

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Photo: Single Point Refueling, G500 PAS, p. 7-9
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[G500 PAS, p. 7-9] To set a fuel load at the refueling panel: select GND SVC BUS to ON (if GSB not powered), select PANEL POWER to ON, and toggle the desired fuel load. If the refuel panel indicates “TSC Control,” a fuel load is already programmed in a TSC. The GSCP can override TSC load only if GSCP Fuel / Off switch set to Fuel and a higher load in inputted.

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Photo: Single Point Refueling, G500 PAS, p. 7-10
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[G500 PAS, p. 7-10] To set a fuel load from TSCs, ensure the ground service bus is powered. From TSCs 1 through 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 prevent a higher GSCP fuel load from overriding a lower TSC load.


Limitations and Abnormal Procedures


Limitations

Fuel Reserves

[G500-MOL-19005, §01-03-100] In addition to the fuel reserve requirements of 14 CFR 91.151, 91.167, 135.209 or 135.223 (as applicable), carry 45 minutes extra fuel.

Maximum Fuel Imbalance

[G500-MOL-19005, §01-28-40] Fuel Balancing is prohibited in flight unless the displayed fuel imbalance is greater than 1,000 lbs and a Fuel Imbalance CAS message is displayed.

[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


See Also:

Gulfstream GVII-G500 Airplane Flight Manual, Revision 4, August 29, 2019

Gulfstream GVII-G500 Maintenance and Operations Letter, G500-MOL-19-0005, Fuel (ATA 28) AFM Supplement to Address Erroneous Fuel Quantity Display and Fuel Imbalance Crew Alerting System Message, June 19, 2019

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