The Airbus A380-800, the world’s largest commercial passenger aircraft, is a double-deck, wide-body airliner with a maximum takeoff weight (MTOW) of approximately 560 tons and a range of about 8,200 nautical miles. It entered commercial service with Singapore Airlines in October 2007, featuring a three-class cabin layout accommodating around 550 passengers.
The A380-800 has a maximum fuel capacity of 81,890 U.S. gallons, equivalent to roughly 250 metric tons of jet fuel at standard temperature conditions (around 70°F). All fuel is carried in integral wing tanks, which are visible in structural diagrams as the darker wing areas between the front and rear spars. [Figure 1]
The A380 fuel system is highly sophisticated, designed to meet several demanding operational requirements, including:
The fuel system supports a wide range of functions: refueling and defueling, engine and APU fuel supply, fuel jettison, and comprehensive fuel measurement and management. The management function itself incorporates several advanced control features, such as refuel distribution, automatic fuel transfer, sequenced fuel burn, wing-load alleviation, lateral balancing, and active longitudinal CG control.
Each of these system functions is explained in detail in the following sections.
The system uses two main refuel galleries, each equipped with discharge valves and diffusers. This dual-gallery architecture provides substantial flexibility, allowing the aircraft to continue refueling even with several component failures.
Defueling—either of the entire aircraft or selected tanks—can be performed using:
Defuel operations are usually conducted manually using the Refuel/Defuel selectors on the IRP. Internal pumps used for defueling are controlled from the Overhead Panel (OHP) in the flight deck.
During defueling, the system continues to provide full fuel quantity gauging, although fuel characterization and integrity checks are locked out for safety and procedural reasons.
Inside each collector cell are two motor-driven boost pumps, which supply pressurized fuel to the engine. One pump serves as the primary feed pump, while the second provides automatic backup, activating if the primary pump loses pressure.
To improve reliability, each collector cell is also equipped with scavenge ejectors, powered by engine feed pressure. These ejectors remove any free water that collects at the bottom of the collector cell and discharge it as fine droplets into the boost-pump inlet stream, allowing the engine to ingest and burn the mixture safely.
Figure 4 presents the engine-feed arrangement for the aircraft’s left side (ejectors are omitted for clarity).
The system incorporates four crossfeed valves, enabling any engine to receive fuel from any feed tank. This ensures that fuel in the tank associated with a shut-down engine can still be used by the remaining operating engines, enhancing fuel flexibility and extending range after an engine failure.
The APU receives fuel from the right outer feed tank. It includes a dedicated DC-powered boost pump for starting the APU when the main outer-tank engine feed pumps are not running. After the main engines are started and pressurized fuel becomes available, the DC pump is no longer required and can be switched off. A separate low-pressure APU isolation valve (not shown in the figure) is installed near the APU to control the supply line.
The aircraft performs several distinct—and in some cases highly sophisticated—fuel-transfer functions, including:
The outer wing tanks and the trim tank are the last auxiliary tanks to be used. Throughout this programmed burn sequence, the system maintains proper lateral balance by coordinating tank transfers and managing fuel quantities symmetrically.
The outer tanks remain full through most of the cruise phase, when the aircraft still carries substantial weight. This improves structural efficiency and reduces bending loads.
As aircraft weight decreases by top of descent, additional wing bending relief is no longer necessary.
As fuel is burned, the aircraft’s CG naturally shifts aft until it reaches the optimal cruise CG position. If the CG begins to move outside its allowable range, the fuel-management system automatically transfers fuel between the trim tank and the wing tanks to keep it within limits.
This active CG control improves aerodynamic efficiency and reduces drag during cruise.
Fuel exits the aircraft through jettison valves that route fuel from the aft gallery to dump masts located at each wing tip area, ensuring safe dispersion behind the aircraft.
Because this heat is ultimately returned to the associated feed tanks, the system must ensure that elevated fuel temperatures do not compromise the engine-feed integrity or interfere with fuel-quantity gauging accuracy. Of particular concern is the potential for localized heating near fuel-quantity probes, which can temporarily alter fuel density and lead to erroneous readings.
Therefore, the routing and mixing of the returned, warmed fuel are managed carefully to avoid these issues.
Figure 8 provides an overview of the fuel-system architecture and the associated flow of control and monitoring data.
Each CPIOM is a simplex compute module equipped with an operating system capable of hosting multiple software partitions. These partitions run standardized I/O interfaces, while the FMMS supplier is responsible for developing and maintaining the applications specific to fuel measurement, transfer, and management.
The core objective of the IMA concept is reduction of lifecycle costs through standardization of avionics hardware. However, because different aircraft systems have unique I/O requirements and safety-integrity levels, several CPIOM variants were developed for the A380.
The AFDX network—also called the Aircraft Data Communications Network (ADCN)—supports simultaneous bidirectional data exchange among all CPIOMs at 100 Mbps, using deterministic bandwidth management tailored for aerospace applications.
The CPIOMs are grouped into pairs, forming independent computing lanes. Within each lane:
The A380’s FMMS uses two such computing lanes, and either lane is capable of performing full system functionality. One lane operates as the Primary, while the other remains in Standby.
System health is continuously evaluated by the Built-In Test Equipment (BITE) functions within the MON channel. If the primary lane’s health degrades below that of the standby lane, automatic lane transfer occurs, handing control to the healthier standby lane to maintain system integrity.
Each computing lane interfaces with the aircraft’s two Fuel Quantity Data Concentrators (FQDCs). These units collect raw data from all in-tank sensors—including probes, compensators, and temperature sensors—and distribute the processed data to the FMMS for use in:
Each FQDC transmits this processed information to the CPIOMs through dual-redundant ARINC 429 high-speed channels. The units also perform Built-In Test (BIT) on both in-tank components and their own internal processing hardware.
Each FQDC contains three independent, “brick-walled” processing channels:
Each Tank Signal Processor delivers processed measurement data from:
The AGP channel provides:
All processed information is sent to the CPIOMs via redundant ARINC 429 outputs.
The fuel-system supplier develops all FMMS-specific software hosted within these CPIOMs.
The COM channel executes the primary control logic, while the MON channel continuously supervises system health and integrity.
It is notable that Boeing long-range aircraft typically feature simpler fuel systems with fewer tanks and minimal automation, whereas Airbus designs, such as the A380, employ more complex automated fuel management modes, including wing-load alleviation and active CG control.
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The A380-800 has a maximum fuel capacity of 81,890 U.S. gallons, equivalent to roughly 250 metric tons of jet fuel at standard temperature conditions (around 70°F). All fuel is carried in integral wing tanks, which are visible in structural diagrams as the darker wing areas between the front and rear spars. [Figure 1]
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| Figure 1. The Airbus A380-800 |
The A380 fuel system is highly sophisticated, designed to meet several demanding operational requirements, including:
- High dispatch reliability and system availability, essential for an aircraft of this size where delays or cancellations can be extremely costly.
- Robust measurement, management, and handling capability to support advanced operational modes such as active center-of-gravity (CG) control and wing-load alleviation.
- Accurate fuel-quantity gauging, with minimal performance degradation even in the event of equipment faults.
The fuel system supports a wide range of functions: refueling and defueling, engine and APU fuel supply, fuel jettison, and comprehensive fuel measurement and management. The management function itself incorporates several advanced control features, such as refuel distribution, automatic fuel transfer, sequenced fuel burn, wing-load alleviation, lateral balancing, and active longitudinal CG control.
Each of these system functions is explained in detail in the following sections.
Fuel Storage
The Airbus A380-800 uses a distributed fuel-storage configuration consisting of five tanks in each wing along with a trim tank located in the horizontal stabilizer. As illustrated in Figure 2, the wing tanks are connected to outboard vent tanks, which allow proper venting and pressure equalization. Each wing also includes a mid-span surge tank, designed to accommodate fuel expansion and manage fuel movement during ground refueling—particularly when fuel and engine weight may trap an air pocket in the surge-tank region. |
| Figure 2. A380-800 fuel tank arrangement |
The trim tank, positioned inside the horizontal stabilizer, is vented through a standard outboard vent arrangement located on the right side of the tank.
During ground refueling, the outer wing tanks are intentionally quantity-limited to avoid excessive wing-bending moments caused by combined engine and fuel weight near the wing tips. Once the aircraft becomes airborne and the Weight-on-Wheels (WOW) signal switches to false, the system automatically transfers fuel from the mid and inner wing tanks to the outer tanks. This increases the outboard fuel mass, providing wing-load alleviation during the early stages of flight.
The outer tanks generally remain full until the top of descent, by which time aircraft weight has been significantly reduced through fuel burn, making additional wing-bending relief unnecessary.
The A380-800 does not incorporate a center fuel tank in the production configuration. However, the aircraft’s structural design includes provisions within the center wing box to support optional additional fuel capacity for potential long-range variants.
To help illustrate the system’s operation, each schematic highlights the components relevant to the function being described, shown in bold, while all other equipment is displayed in grayscale.
The fluid-mechanical architecture enables the following major fuel-system operations:
Each of these functions is explained in the following sections from a fluid-mechanical standpoint, while topics related to system management, automated control, and fault handling are discussed later in the post.
As with other modern airliners, the fuel management system automatically controls the refueling sequence to maintain proper lateral and longitudinal balance throughout the operation. Should the automatic system be unavailable, ground personnel can operate the system manually by selecting the necessary refuel valves directly from the IRP.
Figure 3 illustrates the left-wing refuel plumbing arrangement, which is mirrored on the right wing.
During ground refueling, the outer wing tanks are intentionally quantity-limited to avoid excessive wing-bending moments caused by combined engine and fuel weight near the wing tips. Once the aircraft becomes airborne and the Weight-on-Wheels (WOW) signal switches to false, the system automatically transfers fuel from the mid and inner wing tanks to the outer tanks. This increases the outboard fuel mass, providing wing-load alleviation during the early stages of flight.
The outer tanks generally remain full until the top of descent, by which time aircraft weight has been significantly reduced through fuel burn, making additional wing-bending relief unnecessary.
The A380-800 does not incorporate a center fuel tank in the production configuration. However, the aircraft’s structural design includes provisions within the center wing box to support optional additional fuel capacity for potential long-range variants.
Fluid-Mechanical System
The fluid-mechanical fuel system of the Airbus A380-800 is exceptionally complex due to the wide range of functions it must support and the number of tanks distributed across the aircraft. In total, the system incorporates 21 fuel pumps and 46 control valves, not including scavenge ejectors, air-release valves, and thermal-relief valves, which are omitted from the upcoming schematics for clarity.To help illustrate the system’s operation, each schematic highlights the components relevant to the function being described, shown in bold, while all other equipment is displayed in grayscale.
The fluid-mechanical architecture enables the following major fuel-system operations:
- Refueling and defueling
- Fuel feed to the engines and APU
- Fuel transfer for burn sequencing
- Fuel transfer for center-of-gravity (CG) control and wing-load alleviation
- Fuel jettison
- Hydraulic system cooling, via heat exchangers using fuel as a thermal sink
Each of these functions is explained in the following sections from a fluid-mechanical standpoint, while topics related to system management, automated control, and fault handling are discussed later in the post.
Refuel and Defuel
The A380-800 uses a pressure refueling system served by two refuel stations located along the wing leading edges. Each station provides access to the aircraft’s refuel manifold through two standard pressure-refueling nozzle connections. An Integrated Refuel Panel (IRP) is installed on the lower fuselage between the wings, combining system controls and fuel-quantity indications.As with other modern airliners, the fuel management system automatically controls the refueling sequence to maintain proper lateral and longitudinal balance throughout the operation. Should the automatic system be unavailable, ground personnel can operate the system manually by selecting the necessary refuel valves directly from the IRP.
Figure 3 illustrates the left-wing refuel plumbing arrangement, which is mirrored on the right wing.
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| Figure 3. Refuel system schematic |
The system uses two main refuel galleries, each equipped with discharge valves and diffusers. This dual-gallery architecture provides substantial flexibility, allowing the aircraft to continue refueling even with several component failures.
Defueling—either of the entire aircraft or selected tanks—can be performed using:
- the aircraft’s internal pumps,
- or an external suction source.
Defuel operations are usually conducted manually using the Refuel/Defuel selectors on the IRP. Internal pumps used for defueling are controlled from the Overhead Panel (OHP) in the flight deck.
During defueling, the system continues to provide full fuel quantity gauging, although fuel characterization and integrity checks are locked out for safety and procedural reasons.
Engine and APU Feed
The A380 engine-feed system follows a conventional Airbus design using collector cells located inside each dedicated engine feed tank. These collector cells are kept full by large motive-flow ejector pumps, which draw fuel from the forward inboard section of each feed tank. The ejectors receive their driving (motive) flow from the discharge of the engine feed pumps and are sized to supply the engine’s maximum takeoff fuel-flow demand. Under normal conditions, the ejectors maintain a slight positive pressure within the collector cells, with excess fuel returned to the surrounding feed tank.Inside each collector cell are two motor-driven boost pumps, which supply pressurized fuel to the engine. One pump serves as the primary feed pump, while the second provides automatic backup, activating if the primary pump loses pressure.
To improve reliability, each collector cell is also equipped with scavenge ejectors, powered by engine feed pressure. These ejectors remove any free water that collects at the bottom of the collector cell and discharge it as fine droplets into the boost-pump inlet stream, allowing the engine to ingest and burn the mixture safely.
Figure 4 presents the engine-feed arrangement for the aircraft’s left side (ejectors are omitted for clarity).
 |
| Figure 4. Engine and APU feed system |
The system incorporates four crossfeed valves, enabling any engine to receive fuel from any feed tank. This ensures that fuel in the tank associated with a shut-down engine can still be used by the remaining operating engines, enhancing fuel flexibility and extending range after an engine failure.
The APU receives fuel from the right outer feed tank. It includes a dedicated DC-powered boost pump for starting the APU when the main outer-tank engine feed pumps are not running. After the main engines are started and pressurized fuel becomes available, the DC pump is no longer required and can be switched off. A separate low-pressure APU isolation valve (not shown in the figure) is installed near the APU to control the supply line.
Fuel Transfer
The A380’s fuel-transfer system uses the forward refuel/transfer gallery for all routine transfer operations. As illustrated in Figure 5, the aft gallery is available as a backup path in the event of equipment failures, providing system redundancy and operational flexibility. |
| Figure 5. Fuel transfer system |
The aircraft performs several distinct—and in some cases highly sophisticated—fuel-transfer functions, including:
Fuel Burn Sequencing
During normal flight, the fuel management system automatically transfers fuel from the inner and mid-wing tanks into the feed tanks, keeping the feed tanks essentially full until the inner and mid tanks are depleted.The outer wing tanks and the trim tank are the last auxiliary tanks to be used. Throughout this programmed burn sequence, the system maintains proper lateral balance by coordinating tank transfers and managing fuel quantities symmetrically.
Wing Load Alleviation
To reduce wing-root bending stresses, fuel is transferred from the inner and mid tanks to the outer tanks shortly after takeoff.The outer tanks remain full through most of the cruise phase, when the aircraft still carries substantial weight. This improves structural efficiency and reduces bending loads.
As aircraft weight decreases by top of descent, additional wing bending relief is no longer necessary.
Active Longitudinal CG Control
The amount of fuel initially loaded into the trim tank is determined during refueling based on aircraft loading conditions and is calculated as part of the refuel distribution logic.As fuel is burned, the aircraft’s CG naturally shifts aft until it reaches the optimal cruise CG position. If the CG begins to move outside its allowable range, the fuel-management system automatically transfers fuel between the trim tank and the wing tanks to keep it within limits.
- As long as fuel remains in the inner and mid tanks, any forward transfer (from trim to wing) is directed into the inner tanks.
- Once the inner and mid tanks are empty, forward transfer routes fuel directly into the feed tanks.
This active CG control improves aerodynamic efficiency and reduces drag during cruise.
Gravity Transfer
In the event of pump failures, fuel can be transferred from the outer tanks or trim tank using gravity flow.
Gravity transfer provides a passive backup method to ensure fuel availability under degraded-system conditions.
As shown in Figure 6, the jettison system uses the aft transfer gallery exclusively. Jettison pumps installed in the inner and mid tanks provide the necessary flow for dumping. During jettison, the trim tank is first drained into the inner tanks, after which the combined fuel is discharged overboard.
- Gravity transfer from the trim tank to the wing tanks is only possible within specific aircraft pitch-attitude limits.
- Gravity transfer from the outer tanks is accomplished by opening the transfer valve located in the mid-wing surge tank, allowing fuel to flow inward.
Gravity transfer provides a passive backup method to ensure fuel availability under degraded-system conditions.
Fuel Jettison
The A380’s fuel-jettison system is controlled by the flight crew using guarded switches on the flight deck, which both arm and activate the function. The crew may pre-select a target fuel quantity—known as “Dump to Gross Weight”—at which point the jettison process automatically terminates. If no target is set, the system continues jettisoning fuel until the aircraft reaches its certified maximum landing weight.As shown in Figure 6, the jettison system uses the aft transfer gallery exclusively. Jettison pumps installed in the inner and mid tanks provide the necessary flow for dumping. During jettison, the trim tank is first drained into the inner tanks, after which the combined fuel is discharged overboard.
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| Figure 6. Jettison system schematic |
Fuel exits the aircraft through jettison valves that route fuel from the aft gallery to dump masts located at each wing tip area, ensuring safe dispersion behind the aircraft.
Hydraulic System Cooling
The A380 uses its fuel system as a thermal sink to dissipate heat generated by the aircraft’s hydraulic systems. As illustrated in Figure 7, hydraulic-fluid heat exchangers transfer heat into the fuel flow from the outer-engine feed circuits. |
| Figure 7. Hydraulic system cooling |
Because this heat is ultimately returned to the associated feed tanks, the system must ensure that elevated fuel temperatures do not compromise the engine-feed integrity or interfere with fuel-quantity gauging accuracy. Of particular concern is the potential for localized heating near fuel-quantity probes, which can temporarily alter fuel density and lead to erroneous readings.
Therefore, the routing and mixing of the returned, warmed fuel are managed carefully to avoid these issues.
Fuel Measurement and Management System (FMMS)
FMMS Architecture
The A380 employs an Integrated Modular Avionics (IMA) architecture built around multiple Central Processor Input/Output Modules (CPIOMs). These modules communicate through an Avionics Full-Duplex Switched Ethernet (AFDX) network— an aviation-adapted form of Ethernet—used to operate and integrate numerous aircraft systems, including the Fuel Measurement and Management System (FMMS).Figure 8 provides an overview of the fuel-system architecture and the associated flow of control and monitoring data.
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| Figure 8. Fuel Measurement and Management System (FMMS) architecture overview |
Each CPIOM is a simplex compute module equipped with an operating system capable of hosting multiple software partitions. These partitions run standardized I/O interfaces, while the FMMS supplier is responsible for developing and maintaining the applications specific to fuel measurement, transfer, and management.
The core objective of the IMA concept is reduction of lifecycle costs through standardization of avionics hardware. However, because different aircraft systems have unique I/O requirements and safety-integrity levels, several CPIOM variants were developed for the A380.
The AFDX network—also called the Aircraft Data Communications Network (ADCN)—supports simultaneous bidirectional data exchange among all CPIOMs at 100 Mbps, using deterministic bandwidth management tailored for aerospace applications.
The CPIOMs are grouped into pairs, forming independent computing lanes. Within each lane:
- one CPIOM acts as the Command (COM) channel, and
- the other serves as the Monitor (MON) channel.
The A380’s FMMS uses two such computing lanes, and either lane is capable of performing full system functionality. One lane operates as the Primary, while the other remains in Standby.
System health is continuously evaluated by the Built-In Test Equipment (BITE) functions within the MON channel. If the primary lane’s health degrades below that of the standby lane, automatic lane transfer occurs, handing control to the healthier standby lane to maintain system integrity.
Each computing lane interfaces with the aircraft’s two Fuel Quantity Data Concentrators (FQDCs). These units collect raw data from all in-tank sensors—including probes, compensators, and temperature sensors—and distribute the processed data to the FMMS for use in:
- fuel quantity calculations,
- distribution management, and
- automated system control.
FMMS Avionics
Figure 9 illustrates the A380’s avionics architecture, showing how the four CPIOM units interface with the Fuel Quantity Data Concentrators (FQDCs) and the Integrated Refuel Panel (IRP). |
| Figure 9. FMMS avionics architecture |
Fuel Quantity Data Concentrators (FQDCs)
The aircraft is equipped with two FQDCs, which act as the primary data acquisition and preprocessing units for the fuel system. Their functions include:- collecting and processing data from all in-tank components,
- generating alternative fuel-quantity computations,
- acquiring pump and valve feedback signals, and
- providing backup level warnings (e.g., low-level, overflow).
Each FQDC transmits this processed information to the CPIOMs through dual-redundant ARINC 429 high-speed channels. The units also perform Built-In Test (BIT) on both in-tank components and their own internal processing hardware.
Each FQDC contains three independent, “brick-walled” processing channels:
- Tank Signal Processor A (TSPA)
- Tank Signal Processor B (TSPB)
- Alternate Fuel Gauging Processor (AGP) + Discrete Input Node (DIN)
Each Tank Signal Processor delivers processed measurement data from:
- capacitance fuel-quantity probes,
- densitometers,
- fuel-temperature sensors.
The AGP channel provides:
- a fully independent backup calculation of fuel quantity (used for cross-checking),
- backup low-level and overflow warnings,
- pump and valve discrete-status feedback via the DIN interface.
All processed information is sent to the CPIOMs via redundant ARINC 429 outputs.
CPIOM Software Partitioning
Each CPIOM pair assigned to the fuel system runs the FMMS application software, divided into Command (COM) and Monitor (MON) partitions, as illustrated in Figure 10. |
| Figure 10. CPIOM software partitioning |
The fuel-system supplier develops all FMMS-specific software hosted within these CPIOMs.
The COM channel executes the primary control logic, while the MON channel continuously supervises system health and integrity.
FMMS Functionality
The FMMS performs the following core functions:Fuel Quantity Measurement and Indication
The A380’s fuel gauging system uses an AC capacitance design that maintains accuracy even in the presence of multiple failures, measuring, processing, and monitoring fuel quantity in each tank with better than ±1% accuracy. A self-healing algorithm compensates for failures and predicts measurement accuracy. Fuel quantity data is transmitted to aircraft systems such as the ECAM, CDS, and CMF. The system achieves a data display integrity of 10⁻⁹ per hour, representing the likelihood of displaying an erroneous but believable fuel quantity. This is enabled by the Alternative Fuel Gauging Processor (AGP), which computes fuel quantity using algorithms independent from the main system. Any significant discrepancy between the main gauging system and the AGP triggers an integrity failure alert.Fuel Temperature Measurement and Indication
Fuel temperature is monitored and processed within each tank in a fault-tolerant manner. Redundant sensors ensure compliance with catastrophic failure requirements. High-integrity fuel temperature warnings are provided for each feed tank, while low-temperature warnings are issued for trim and outer tanks. Accurate temperature measurements are also used in the fuel gauging algorithm.Fuel Level Determination and Indication
High-integrity low-level signals are provided from two independent sources for each feed tank and relayed over the AFDX bus, with backup discretes from the FQDC in case of IMA or AFDX loss. High-level fuel indications are measured via tank probes, with display on the IRP and transmission over AFDX to other aircraft systems. Surge tanks also provide overflow indications from dual independent sources, again with backup discretes for redundancy.CG Measurement
To meet hazardous failure requirements, aircraft CG is computed using two independent methods based on zero-fuel aircraft CG and fuel data. The system also predicts the accuracy of CG measurements and initializes CG information as commanded by the aircraft interface.CG Management
FMMS calculates aircraft CG targets and executes forward and aft fuel transfers via the trim tank to maintain CG within predefined limits. A CG limit warning is provided to the flight crew if thresholds are exceeded.Fuel Transfer Control
All transfer modes, including fuel burn sequencing and wing-load alleviation, are automatically controlled by the FMMS using tank quantity data to operate pumps and valves. Manual override is available via the Overhead Panel (OHP), allowing the flight crew to manage individual pumps and valves in the event of system failures. [Figure 11] |
| Figure 11. A380-800 Flight deck fuel panel |
Refuel Control
The FQMS supports both automatic and manual refueling via the Integrated Refuel Panel (IRP), with automatic control also available from the flight deck. The operator preselects the required fuel mass, and individual tank quantities are targeted to maintain longitudinal CG and lateral balance within limits. The system predicts post-refuel distribution for each tank and aborts automatic operation if limits are exceeded, providing complete status updates on the IRP display.Defuel Control
Defueling can be accomplished using internal aircraft pumps or external suction, controlled manually via the IRP Refuel/Defuel switches. Internal pumps are activated from the flight deck OHP. Full gauging capability is maintained during defueling, though fuel characterization and integrity checks are temporarily inhibited.Jettison Control
Fuel jettison is initiated via push-button selection by the crew. The desired fuel quantity can be specified using the Jettison Fuel to Gross Weight (JFWG) function. Jettison stops automatically when the selected quantity has been released or when reaching predetermined limits. High-integrity control from the Command and Monitor CPIOMs governs the jettison valves, and full fuel gauging is maintained throughout the operation.Transfer Status, Warning, and Caution Indication
The FMMS provides comprehensive status information for pumps, valves, and transfers. Pump status includes ‘on,’ ‘off,’ ‘abnormal on,’ and ‘abnormal off.’ Valve status includes ‘open,’ ‘shut,’ ‘failed open,’ and ‘failed shut.’ Transfer status indicates whether a transfer is active, failed, or inhibited.System BITE
The system features enhanced Built-In Test Equipment (BIT), including power-up and safety tests. Continuous cyclic monitoring evaluates all fuel system components, reducing failure exposure time. Extensive fault analysis isolates and identifies failures in tank sensors (open, short, contaminated), LRUs, CPIOMs, and wiring harnesses. The system interfaces with the aircraft’s Central Maintenance Function (CMF).It is notable that Boeing long-range aircraft typically feature simpler fuel systems with fewer tanks and minimal automation, whereas Airbus designs, such as the A380, employ more complex automated fuel management modes, including wing-load alleviation and active CG control.
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