B767 

 FuelDO NOT USE FOR FLIGHT

Introduction The fuel system supplies fuel to the engines and the APU. The fuel is contained in a center tank, and left and right main tanks.Refer to Chapter 7, Engines, APU, for an additional description of the engine and APU fuel systems.

Fuel QuantityFuel quantity data, measured by probes in each tank, is fed to the fuel quantity processor where it is corrected for density then displayed on a fuel quantity indicator for each tank. Total fuel quantity, from a separate calculation, is shown on the total fuel quantity indicator and is also provided to the FMC.When total usable fuel in either left or right main tank drops below approximately 2200 pounds, the FUEL CONFIG light illuminates and the LOW FUEL caution message is displayed.

Fuel TemperatureTemperature of the fuel in the left main tank is displayed on the fuel temperature indicator.

Fuel PumpsEach fuel tank contains two AC–powered fuel pumps. A single pump can supply sufficient fuel to operate one engine under all conditions.The two center tank fuel pumps have greater output pressure than the left and right main tank fuel pumps. When all six pumps are operating, the center tank pumps override the left and right main tank pumps so that center tank fuel is used before left or right main tank fuel.If any pump has low output pressure, the appropriate switch PRESS light illuminates and the pump pressure EICAS message is displayed. If the main tank pump switches are OFF, the low pressure lights are illuminated and EICAS messages for the pumps are displayed. When the center pump switches are OFF, the low pressure lights and EICAS messages for the center pumps are inhibited.To reduce electrical loads, the center tank pumps are inhibited when the associated N2 is less than 50% RPM. Thus both center tank pumps are inhibited when the engines are shutdown. As an engine is started and N2 RPM increases above 50%, the inhibit is removed for the associated center tank pump.

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The EICAS caution messages, L or R FUEL SYS PRESS, displays when all fuel pumps have low output pressure or all fuel pumps on one side have low output pressure and the crossfeed switches are off.The fuel pump low pressure messages are inhibited by the corresponding L or R FUEL SYS PRESS messages.During normal operation, the EICAS advisory messages CTR L FUEL PUMP and CTR R FUEL PUMP display to indicate depletion of center tank fuel.With either message displayed, a small amount of center tank fuel may be indicated. A scavenge system will operate automatically to transfer any remaining center tank fuel to the main tanks. Fuel scavenge begins when the main tanks are approximately half empty.The left main tank contains a DC–powered fuel pump. It has no controls or indicators. The DC pump operates automatically to provide fuel to the APU when AC power is not available and the APU selector is ON.

Fuel CrossfeedThe fuel manifolds are arranged so that any fuel tank pump can supply either engine. Two crossfeed valves isolate the left fuel manifold from the right. These valves are normally closed providing fuel feed from tank to engine. Both valves are opened any time it becomes necessary to feed an engine from an opposite fuel tank. Only one open crossfeed valve is required for successful crossfeed operation. A valve disagreement light illuminates and the EICAS advisory message FWD FUEL X–FEED or AFT FUEL X–FEED displays if a valve position does not agree with its switch position. The L or R FUEL SYS PRESS messages are inhibited with either crossfeed valve open.

Suction FeedWhen main tank fuel pump pressure is low, each engine can draw fuel from its corresponding main tank through a suction feed line that bypasses the pumps. As the airplane climbs, dissolved air is released from the fuel in the tank due to the decrease in air pressure. This air may collect in the suction feed line and restrict fuel flow. At high altitude, thrust deterioration or engine flameout may occur as a result of the fuel flow reduction.Fuel pressure can be provided from a main tank with operating fuel pumps to both engines by opening the fuel crossfeed valves. Continued crossfeed use will result in a progressive fuel imbalance.The dissolved air in the fuel tank will eventually deplete after reaching cruise altitude. The depletion time is dependent upon airplane altitude, fuel temperature, and type of fuel. Once the dissolved air is depleted, the engine may be capable of suction feed operation at cruise power.

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Fuel Configuration LightWhen the fuel quantity in left and right main tanks differ by 2000 pounds (plus or minus 500 pounds) or center fuel pump switches are OFF with more than 1200 pounds in the center tank, the FUEL CONFIG light illuminates and the EICAS advisory message FUEL CONFIG is displayed. The FUEL CONFIG light also illuminates when the EICAS caution message LOW FUEL is displayed.

Fuel ImbalanceFuel balancing is accomplished by opening the crossfeed valves and turning off the fuel pump switches for the left or right main fuel tank that has the lowest quantity. Fuel balancing may be done in any phase of flight.

Fuel Tank Locations and Capacities

Fuel Tank Locations

LEFT MAIN TANK

CENTER TANK

RIGHT MAIN TANK

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Fuel Tank CapacitiesTank U.S. Gallons Pounds *

Left main 6,010 40,267

Right main 6,010 40,267

Center 11,900 79,730

Total 23,920 160,264

* Usable fuel at level attitude, fuel density = 6.7 LB/U.S. per Gallon

Tank U.S. Gallons Pounds *

Left main 6,010 40,267

Right main 6,010 40,267

Center 11,960 80,132

Total 23,980 160,666

* Usable fuel at level attitude, fuel density = 6.7 LB/U.S. per Gallon

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Fuel System Schematic

APU Fuel FeedAPU fuel is supplied from the left fuel manifold. APU fuel can be provided by any AC fuel pump supplying fuel to the left fuel manifold or by the left main tank DC fuel pump.

AFT

SSERP

PRESS

ON

L

C PUMPS

XFEEDFUEL

PUMPSL

FWDVALVE

PRESS

ON

ON

VALVE

CROSSFEED

APU

DC

LEFTMAIN

CENTER

ENGINEVALVE

VALVESPAR

APU FUELVALVE

VALVES

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On the ground, with the APU selector ON and no AC power available, the DC pump runs automatically. With AC power available, the left forward AC fuel pump operates automatically, regardless of fuel pump switch position, and the DC fuel pump turns off.

Fuel JettisonThe fuel jettison system allows jettison from the center fuel tank. Fuel is jettisoned through nozzles inboard of each outboard aileron. The common fuel manifold allows jettison pumps in the center tank to pump fuel overboard.Two dual pump units provide a high capacity jettison rate of approximately 2600 pounds per minute.Fuel jettison begins when:

• the FUEL JETTISON selector is selected ON• the jettison transfer valves open• the FUEL JETTISON NOZZLE switches are selected ON• the nozzle valves open, and• the jettison pumps operate

The FMC discontinues fuel value calculations and the totalizer value is used during fuel jettison operation. After fuel jettison is complete, the calculated value will reset using the same value as the totalizer value.The fuel disagree message is not displayed during fuel jettison operation.

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Fuel Jettison Schematic

Fuel System FMS CDU MessagesThe CDU can display the following messages.INSUFFICIENT FUEL – Predicted fuel at destination is less than the FMC reservesFUEL DISAGREE–PROG 2 – The fuel totalizer and calculated fuel quantity disagree

L-NOZZLE-RJETTISON

ONOFF

FUELFAULT

VALVEVALVE

ON ON

NOZZLEVALVE

OUTER MAIN(LEFT)

TANKLEFT MAIN

TANKCENTER

VALVESTRANSFER

JETTISONPUMPS

JETTISON

CENTER/

TO ENGINES

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Fuel System EICAS MessagesThe following EICAS messages can be displayed.

Message Level Light Aural Condition

FUEL CONFIG Advisory FUEL CONFIG

Both center pump switches are OFF with fuel in the center tank or a fuel imbalance between main tanks

AFT FUEL X-FEED

FWD FUEL X-FEED

Advisory VALVE The crossfeed valve position disagrees with the commanded position

FUEL JET NOZ Advisory VALVE In flight, the nozzle valve position disagrees with the commanded position

On the ground indicates one or both fuel nozzle valves are open

L FUEL JET PUMP

R FUEL JET PUMP

Advisory FAULT The associated fuel jettison pump is inoperative

L JET XFER VALVE

R JET XFER VALVE

Advisory FAULT The associated fuel jettison transfer valve is not in the commanded position

CTR L FUEL PUMP

CTR R FUEL PUMP

L AFT FUEL PUMP

R AFT FUEL PUMP

L FWD FUEL PUMP

R FWD FUEL PUMP

Advisory PRESS Fuel pump output pressure is low

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Message Level Light Aural Condition

L FUEL SYS PRESS

R FUEL SYS PRESS

Caution Beeper All fuel pumps have low output pressure or all fuel pumps on one side have low output pressure and the crossfeed switches are off

LOW FUEL Caution FUEL CONFIG

Beeper Fuel quantity is low in either left or right main tank

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Fuel System

1 Left/Center/Right (L/C/R PUMPS) SwitchesON – the fuel pump is selected ONOff (ON not visible) – the fuel pump is selected off

2 Left/Right Pump Pressure (PRESS) LightsIlluminated (amber) – fuel pump output pressure is low

3 Center Pump Pressure (PRESS) LightsIlluminated (amber) –

• fuel pump output pressure is low with the pump selected ON• associated N2 below 50% with pump switch ON

Note: Illumination is inhibited when the center tank fuel pump switch is selected OFF.

4 Fuel Crossfeed (FUEL XFEED) SwitchesOn (bar visible) – the crossfeed valve is selected openOff (bar not visible) – the crossfeed valve is selected closed

PRESS

ON

VALVE

ON

PRESS

ON

PRESS

ON

PRESS

FUELCONFIG

AFT AFT

FWDFWD

LPUMPS

RFUELXFEED

C PUMPS

L R

ON

PRESS VALVE

ON

PRESS

PUMPS

OVERHEAD PANEL

6

4

5

3

1

2

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5 Crossfeed VALVE LightIlluminated (amber) – the crossfeed valve is not in the selected position

6 Fuel Configuration (FUEL CONFIG) LightIlluminated (amber) –

• low fuel quantity• imbalance between left and right main tanks• center tank fuel pumps off with fuel in center tanks

Fuel Indications

Fuel Quantity Indicator

1 Fuel Quantity (L/C/R FUEL QTY) IndicationDisplays usable fuel quantity in the left main, center, and right main tank (pounds x 1000)

2 Fuel Temperature (TEMP) IndicationDisplays temperature of fuel in the left main tank (degrees celsius)

3 TOTAL Fuel Quantity IndicationDisplays total usable fuel quantity in all tanks (pounds x 1000)

OVERHEAD PANEL

L C R

LBLBLB

TOTAL

X 1000

TEMP oC

FUEL QTY

1

2 3

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Fuel Jettison

1 Fuel Jettison Nozzle Switches (L–NOZZLE–R)ON – opens respective jettison nozzleOff (ON not visible) – closes respective jettison nozzle

2 Fuel Jettison Nozzle VALVE LightsIlluminated (amber) – the jettison nozzle valve is not in the selected position

3 FAULT LightIlluminated (amber) – jettison pump(s) and/or transfer valve(s) disagree with jettison switch position

4 Fuel Jettison SelectorOFF – closes both jettison transfer valves and turns off jettison pumpsON – opens both jettison transfer valves and turns on jettison pumps

ONON

VALVE VALVE

FAULT

FUEL

OFFON

JETTISONL-NOZZLE-R

OVERHEAD PANEL

3

4

1

2

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Fuel Quantity Test

1 Fuel Quantity (FUEL QTY) Test SwitchSpring–loaded to centerInitiates fuel quantity test

ACCESSORY PANEL

1

FUELQTY

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