Fuel on the Boeing 757 is contained in a sealed wing box structure. The fuel system supplies fuel for the engines and APU. Fuel suction feed is available only from the left and right main tanks. The wing structure contains left and right main tanks and a centre tank section. Fuel picked up in the vent system and fuel in the refuelling manifold drains into the centre tank.

The boxes below show the useable fuel in each tank with the aircraft at a level attitude, followed by a fuel tank location diagram.

LEFT 6,600 kgs		CENTRE 20,800 kgs		RIGHT 6,600 kgs
		TOTAL 34,000 kgs

Fuel quantity data is measured by probes in each fuel tank, and transmitted to the Fuel Quantity Processor where it is processed, corrected for density and converted to kilograms (KGS) or pounds (LBS) depending on the carrier option. It is 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.


On the digital fuel quantity displays a zero will be displayed on either side of the decimal point to confirm that the quantity is either less than one thousand KGS / LBS (for example 0.7 = 700 kgs / lbs) or an even number of thousand kgs / lbs (for example 3.0 = 3,000 kgs / lbs).

The fuel temperature probe reads the temperature of the fuel in the right main tank in degrees celsius and displays the value on the fuel quantity indicator.

When total useable fuel in either main tank drops below 1,000 kilograms, the Master CAUTION and FUEL CONFIG lights illuminate, caution Aural sounds and the EICAS caution message LOW FUEL is displayed.

The fuel quantity indicators may be tested by holding the test switch, on the Accesory Panel, in the FUEL QTY position. This powers each segment of the liquid crystal displays, and all digits should read "8" except the first figure in the Total Fuel Quantity indicator which reads "1".

The fuel Temperature indicator should read "- 185^oC" +/- 2^oC during the test. Any other value represents an indicator failure. The fuel quantity test also initiates a low fuel caution including:

  - aural caution sounds
  - master CAUTION lights
  - an EICAS message LOW FUEL
  - a FUEL CONFIG light

Loss of any of these caution elements represents a failure in the low fuel caution system. Releasing the switch returns the system to its original condition. If the test switch is held in the FUEL QTY position for longer than approximately six seconds, the original condition and display will also return automatically.

Each main tank contains two AC motor driven fuel pumps. Each pump has the capacity of supplying adequate fuel to one engine for all thrust conditions.


Two AC motor driven fuel pumps are installed in the centre tank. These centre fuel pumps have approximately double the output pressure of the main tank fuel pumps, this ensures that when all pumps are operating, fuel is supplied to the engines by the centre tank fuel pumps.

The fuel pumps provide a positive flow of fuel under pressure to the engine driven fuel pumps. There is a low pressure sensor for each pump located between the pump outlet and the discharge check valve.

The appropriate PRESS light illuminates and an EICAS message such as "R FWD FUEL PUMP" is displayed to identify any pump with low output pressure.

EICAS caution messages "L FUEL SYS PRESS" or "R FUEL SYS PRESS" indicate low fuel pressure in the left or right fuel manifold. The fuel pump low pressure messages are inhibited by the corresponding "L FUEL SYS PRESS" or "R FUEL SYS PRESS" messages.

If the main tank pump switches are OFF, the low pressure lights and EICAS messages for the pumps are illuminated. When the centre pump switches are OFF, the low pressure lights and EICAS messages for the pumps are inhibited.

If AC power is not available, a DC motor driven fuel pump in the left main tank provides fuel to the APU. There are no panel controls for this pump. Pump operation may be checked by an EICAS maintenance message on the ground only.

The centre tank pumps are inhibited when the associated N3 is less than 50% RPM as a load shed function.

On the ground, both centre tank pumps are inhibited with the engine shutdown. As the engine is started and N3 RPM increases above 50%, the inhibit is removed when the refuelling door is opened. In flight, with an engine shutdown, the associated centre tank pump is inhibited.

Engine fuel manifolds are connected so that any fuel pump may supply fuel to either engine. A crossfeed valve isolates the left fuel manifold from the right. This valve is normally closed providing fuel feed from tank to engine. The valve may be opened any time it becomes necessary to feed an engine from an opposite fuel tank. If the valve position does not agree with the switch position, a valve disagreement light illuminates and the EICAS advisory message FUEL CROSSFEED is displayed.

The left and right fuel systems are similar, except that the right system contains additional features not found in the left system. These are:

- Fuelling panel and associated plumbing
- Fuel temperature probe

The left system contains the DC pump and APU fuel feed.

The Fuel Configuration Light illuminates and a FUEL CONFIG advisory message appears on EICAS under the following conditions:

- centre fuel pump switches are OFF with greater than 600 kgs in the centre tank
- a fuel imbalance between main tanks of 800 kgs

Fuel balance can be achieved by using fuel from the heavy tank to feed both engines. The allowable fuel imbalance can be found in the Fuel Limitations section.

The Fuel Configuration Light illuminates, LOW FUEL message appears, the caution tone sounds and both caution lights illuminate when either main tank is below 1,000 KGS.

Fuel is supplied to the APU from the left fuel manifold. APU fuel feed can be provided be any operating AC pump or the DC pump. With the APU switch ON and AC power on the aircraft, the left forward fuel pump operates automatically regardless of the switch position and it cannot be turned off on the ground. In flight it can be turned off with the pump switch.

Normal fuelling is accomplished through dual fuel nozzle adapters located on the right wing leading edge spar at the fuelling stations. All fuelling operations, except fuel pump control, are accomplished at the fuelling station. Opening the station access door applies DC power to the fuelling system and removes the N3 inhibit to the centre tank fuel pumps.


Fuel flows through the dual nozzles to pressurise a fuelling manifold. Fuelling valves control the flow of fuel from the fuelling manifold into each of the three switches on the fuelling panel. A fuel quantity may be preselected for each tank. The fuelling valves close automatically when the preselected quantity is reached or when the tank is full, whichever occurs first.

A tank overfill system is provided to prevent fuel spillage. If any fuel is sensed in the surge tanks during fuelling, a signal is sent to close all fuelling valves.

The aircraft is filled automatically by hydrant or tank truck pressure. All tanks may be fuelled at the same time. The main tanks may also be fuelled manually through over wing fill ports. There are no over wing fill ports for the centre tank.

Left and right defuelling valves connect their respective engine fuel manifolds with the fuelling manifold.

Fuel can be pumped from any tank to the corresponding engine fuel manifold by operating the tank fuel pump(s). Opening the appropriate defuelling valve (left valve for left side - right valve for right side) routes the fuel from the corresponding engine fuel manifold to the fuelling manifold.

For defuelling, the flow into the fuelling manifold is reversed for fuel to flow back into a truck or hydrant.

Suction defuelling can be accomplished by opening the respective defuelling valve and applying an outside suction source to the fuelling nozzles. Suction defuelling is not available for the centre tank.

On the ground fuel can be transferred from a source tank to a receiving tank by operating the fuel pump(s) in the source tank and opening the Left or Right defuelling valve which pressurises the fuelling manifold from the respective Left or Right fuel manifold. Opening the fuelling valves in the receiving tank completes the transfer.

A fuel jettison system is not installed on the 757. The best configuration for reducing aircraft weight is to fly at 250 knots with the gear down. Speedbrakes may be used if desired. It should be emphasised that while the Boeing 757 is certified for landing up to the Maximum Takeoff Weight (MTOW) in an emergency, overweight landings should only be made if a delay to burn off fuel would expose the aircraft and / or it's occupants to additional hazard.