Fuel System Flashcards
Fuel tanks
2 Feed tanks2 wing auxiliary tanks2 forward sponson tanks 1 aft sponson tankProvisions for up to 3 Mission Auxiliary Tanks
Type of fuel pumps
2 suction lift pumps one at each feed tank. Boost pumps which are normally used during refueling and fuel dumping are available to support the suction lift pumps in the event of a failure.
L/R Feed tank capacities
88 gallons (600 lbs)
L/R Wing Aux tank capacities
294 gallons (2000 lbs)
L/R Fwd Sponson tank capacities
478 gallons (3250 lbs)
R Aft Sponson tank Capacity (if installed)
301 gallons (2050 lbs)
Total capacity in normal configuration (L/R Feed, L/R Wing Aux, L/R Fwd Sponson tanks)
11,700 lbs
Quantities of MATS tanks based on 80% full for the forward and 75% full for the mid and aft tanks
Fwd - 345 gallons (2350 lbs)Mid - 324 gallons (2200 lbs)Aft - 324 gallons (2200 lbs)
MATS
Mission Auxiliary Tank System - Comprised of up to 3 430 gallon fuel tanks (Forward, Mid, and Aft tanks if installed)
OBIGGS
Onboard Inert Gas Generating System - Provides a nitrogen enriched atmosphere for fuel tank inerting which reduces tank vulnerability to fire and explosions attributable to ballistic impacts.
Which tanks are 100% self sealing
Wing feed tanks
How many fuel probes are there in each tank
There are two Fuel Quantity Probes in each Feed, Wing Auxiliary, and Forward Sponson Tank. There is only one Fuel Quantity Probe in each Mission Auxiliary Tank and the right Aft Sponson Tank.
Rupture Disks
Aluminum membranes that break and vent fuel overboard through vent lines if the tank is overfilled or if the tank is overpressurized (climb valve fails to open during ascent)
Climb/Dive Valves
As a fuel tank’s pressure increases or decreases due to altitude changes, the Climb/Dive Valves open to compensate
Sump Drain Valves
provided as a means of sampling fuel and defueling tanks by gravity
Negative Gravity Inlet Assemblies
Installed on the left and right Feed Tanks to provide 10 second supply of fuel to the engines during negative G maneuvers
FMU
Provide an interface to the aircraft pumps, valves, and quantity measurement system, and also perform monitoring using Built-In-Test (BIT) and fault annunciation.
How do you isolate tanks
Fuel status layer Menu 3, and Fuel status layer Menu 4 for MATS tanks
Fuel Burn Sequence
Right Aft Sponson (if installed)Aft Mission Aux (if installed)Mid Mission Aux (if installed)Fwd Mission Aux (if installed)L/R Wing AuxL/R Fwd SponsonL/R Wing Feed
When is the Cross Transfer Valve taken out of the AUTO mode
If there is a single FMU failure in which case it defaults to CLOS, or if it’s manually changed by the pilot.
When should the Cross Transfer Valve be manually placed in the OPEN mode
During Single engine operation select the XFER VALVE to OPEN and the Transfer Pumps (TPUMP BOOST) to ON to ensure fuel is made available to the operative engine and mitigate uneven fuel burn
Suction Transfer
Primary means of transferring fuel and the 2 suction lift pumps are automatically controlled by the FMUs
Where are boost pumps installed
Sponson Tanks, Wing Auxiliary Tanks, and MATS (if installed).
All fuel can be dumped except for ___
fuel in the feed tanks (unless the suction lift pump has failed)
Rate that fuel is dumped
Approximately 800 lbs per minute
Fuel Dump System utilizes____
all available boost pumps
Configuration for fuel dump
Cargo ramp door closedLanding gear up Main cabin door closed
Fuel dump altitude limitation
6000 ft AGL and above except for in an emergency
When will fuel dump automatically secure
approximately 70 seconds after usable fuel reaches 1700 lbs indicated
Where is the fuel dump panel located
overhead panel
When can fuel dump not be initiated
With a single FMU failure
How does an FMU failure affect the Fuel Transfer/Crossfeed System
When the Cross-Transfer Valve (XFER VALVE) is operating in the automatic (AUTO) mode, failure of an FMU will automatically set the XFER VALVE to the closed (CLOS) position. If the XFER VALVE is operating in the manually selected OPEN or CLOS position when the FMU failure occurs, it will remain in that selected position.
EARP
Emergency Aerial Refueling Panel - Located above the left hand avionics rack, used to manually open and close the refuel valves and pump bypass valves for the transfer tanks on the FMU failed side to facilitate or secure aerial refueling with an FMU failure.
Fuel Dump capability with single FMU failure
Fuel cannot be dumped with a single FMU failure
FEED TANK LOW Caution
Quantity below 550 lbs +/- 20 lbs or when gauged quantity reads 520 lbs
FEED TANK OVERFILL Caution
Quantity at 675 lbs
What triggers a FUEL TRAPPED Caution
FMU detects a FEED TANK LOW condition and fuel is not transferring from the tank that should be transferring
PRESSURE SOV IN TEST Advisory
Simply lets the crew that an automatic BIT of the Pressure Shut Off Valves has commenced. It may last as long as 15 minutes.
What conditions must be met for the Pressure Shutoff Valve test to begin
- BOTH engines running for more than 60 seconds2. BOTH engines burning more than 600 pph for at least 20 seconds
FUEL PROBE FAULT Advisory
ARRP has failed to reach its commanded position within 3 minutes
What conditions can cause a FUEL PROBE FAULT
- Probe is jammed2. ABIU fails to communicate with JASS 3. Aircraft experiences HYD 3 FAIL or UTIL SYSTEMS INOP Caution
Indications of Suction Lift Pump Failure
- Fuel decreasing in the associated Feed Tank on the FUEL Status Layer (with fuel remaining in sponson tanks)2. L/R WING FEED TANK LOW caution, MASTER ALERT light, and caution tone3. FUEL BST AUTO ON advisory
FARE Kit
Used to transfer MATS to other aircraft or combat weapons systems or to defuel the MATS
FARE flow rate
The pump is rated at 120 gpm but the actual flow rate is 45 gpm for single point setup and 25 gpm for dual point setup
Why should the MATS be isolated during aerial refueling
A low fuel state in the MATS during aerial refueling will provide an air source in the system that will cause the suction lift pump to lose its prime
FMU is powered by ___
Essential/Battery Bus
Describe how the fuel system is crashworthy
The system utilizes Breakaway Fuel Fittings so that if a fuel tank or line separates from its manifold as a result of a crash landing, breakaway fittings at connection points throughout the Fuel System prevent fuel from escaping and decrease the risk of fire.
Describe the self sealing capability of the fuel system
If the protected tank wall is punctured, a natural rubber sealant between the outer and inner liners is activated by the fuel and becomes a tacky substance that will fill the hole and seal the puncture.
How much of the feed tanks are self sealing
Feed Tanks are 100% self-sealing.
How much of the Sponson tanks are self sealing
Sponson Tanks are fully self-sealing, except for the top surface and the top two-thirds of the outboard surface
How much of the Wing Auxiliary tanks are self sealing
Wing Auxiliary Tanks are self-sealing on the lower one-third of the tank
How much of the MATS tanks are self sealing
Mission Auxiliary Tanks are fully self-sealing except for the top surface
2 Sensors contained in each fuel probe
Low level sensor and a high level (overfill) sensor
What happens if a fuel probe fails in a tank with 2 installed
FMU will utilize the remaining probe to measure quantity at reduced accuracy, but system will not indicate more than actual quantity
Number and location of the FMUs
2 located on the midwing forward equipment shelf
Major functions of the FMUs
- Measure fuel quantity2. Manage fuel burn sequence3. Manage ground/aerial refueling, defueling, and fuel dumping4. Monitor fuel system health and isolate component faults5. Communicate system status to the Ground Refuel/Defuel Panel6. Communicate system status to the Integrated Avionics System7. Communicate system status to the Standby Flight Display (SFD)8. Communicate low engine and transmission oil levels to the Ground Refuel/Defuel Panel (GRDP)
How do the FMUs interface with the Ground Refuel Defuel Panel?
FMUs transmit total fuel quantity to the GRDP and send signals to the GRDP when aircraft oil reservoir levels are low
What fuel functions are controlled from the Ground Refuel Defuel Panel
Pressure refueling, gravity refueling, and suction defueling are controlled from the GRDP.
Ground Refuel Defuel Panel Displays ___
fuel SYSTEM STATUS and TOTAL FUEL QTY. The GRDP displays a light when the ENGINE, TILT AXIS GRBX, PROPROTOR GRBX, VF GENERATORs, AUX POWER UNIT, MIDWING GEARBOX, SHAFT DRIVEN COMPRESSOR, and EMERGLUBE RES oil levels are low.
Pressure Refueling Sequence
L/R Wing Feed Tanks, L/R Forward Sponson Tanks, the Forward and Mid Auxiliary Tanks (if installed), and the Wing Auxiliary Tanks (if installed), will fill simultaneously. Once the aircraft has filled past 75% of the total selected forward quantity, the FMGS will fill the Aft Mission Auxiliary Tank (if installed) to 75% quantity at which point the Right Aft Sponson Tank (if installed) will begin to take on fuel.
Overfill Protection
Provided by fuel level control valves in the Wing Feed, Wing Auxiliary, and Sponson Tanks. For the Mission Auxiliary Tanks, an optical sensor triggers the motor operated refuel valve to shut off flow to the tank.
What happens if primary shutoff system fails to stop fuel flow
The FMUs provide secondary shutoff to all transfer tanks.
Menu 1 of the Fuel Status Layer
Provides control of the cross-transfer valve and transfer pump boost mode
Menu 2 of the Fuel Status Layer
Provides control of the aerial refueling mode
Menu 3 of the Fuel Status Layer
Used to isolate a tank to provide selective tank filling, transfer, and suction defueling
Menu 4 of the Fuel Status Layer
Used to isolate a MATS tank to provide selective tank filling, transfer, and suction defueling
What happens when the cross transfer valve is OPEN
fuel on either side of the aircraft is fed simultaneously to both Feed Tanks
Purpose of fuel cross transfer
cg management capability and makes all fuel available to the operating engine in the event of a single engine failure
When is the Cross Transfer Valve unavailable
Ground Refuel/DefuelPreflight BITSOV IN TESTAERIAL REFUELJETTISONEngines or APU not running.
3 Selectable positions of the cross transfer valve (XFER VALVE)
OPENCLOSAUTO
XFER VALVE AUTO
Default position, represented on the Fuel Status Layer by an A encased in a circle. XFER VALVE is controlled automatically by the FMUs
XFER VALVE CLOS
Represented on the Fuel Status Layer by vertical lines encased in a circle.
If XFER VALVE is manually selected to OPEN and an FMU Failure occurs what action should be taken
XFER VALVE should be selected to CLOS to ensure fuel estimation on the failed FMU side will be accurate
XFER VALVE OPEN
Represented on Fuel Stat layer by horizontal lines encased in circle
When are the boost pumps operated
when commanded ON by the FMU during their respective burn sequence when TPUMP BOOST is selected to AUTO, and when TPUMP BOOST is selected to ON. The sponson boost pumps will also operate during gravity refueling and refuel manifold purge. All boost pumps will operate during fuel jettison.
Suction Lift Pumps
Located in each feed tank, transfer fuel from sponson transfer tanks to the feed tanks
What happens to the suction lift pumps during single engine operation
Suction Lift Pump of the inoperative engine will shut down after all sponson transfer tank fuel is used allowing cross-transfer of Feed Tank fuel to the side with the operable engine.
Location Sponson boost pumps
Located in main landing gear bay
When do the sponson boost pumps operate
during gravity refueling, fuel dump, refuel manifold purge, refuel probe stow mode, and when BOOST mode is selected during the sponson phase of the fuel burn sequence.
Where is the fuel dump tube located
attached below the Right Aft Sponson Tank
What system is disabled when FUEL DUMP is selected
AN/ALE-47 CMDS chaff/flare dispensing
Which fuel tanks does FMU 1 manage
The left side fuel tanks and the Forward Mission Auxiliary Tank
Which fuel tanks does FMU 2 Manage
The right side fuel tanks and the Mid and Aft Mission Auxiliary Tanks
What is the EARP used for
To manually open and close the refuel valves and pump bypass valves for the transfer tanks to facilitate or secure aerial refueling
What is the Left Position of the EARP used for
FMU 1 failure and is used to manually control the refuel and pump bypass valves to allow aerial refueling of the left Wing Auxiliary, left Forward Sponson, and Forward Mission Auxiliary Tanks
What is the Right Position of the EARP used for
FMU 2 failure and is used to manually control the refuel and pump bypass valves to allow aerial refueling of the right Wing Auxiliary, right Forward Sponson, right Aft Sponson, and Mid and Aft Mission Auxiliary Tanks
How is an FMU failure depicted on the Fuel Stat Layer for the Auxiliary and Sponson tanks
Quantity indications for the Wing Auxiliary, Sponson, and Mission Auxiliary tanks that the respective FMU monitors will indicate zero
How is an FMU failure depicted on the Fuel Stat Layer for the Feed Tanks
Fuel quantity in the affected Feed Tank will show 526 lbs and remain green until the fuel level uncovers the low level sensor. At that time, the quantity display will change to yellow and the operating FMU will begin estimating fuel remaining in the Feed Tank
How does an FMU Interlink Failure affect the Cross Transfer Valve
Automatically closes the Cross Transfer Valve, disabling fuel dump and aerial refueling capabilities. The Cross Transfer Valve must be operated manually
How his trapped fuel displayed on the fuel status layer
The trapped tank will be red with the last known quantity displayed. The usable fuel quantity will decrease by the amount of fuel trapped.
Procedure for FMU INTERLINK FAIL or FMU X FAIL Caution
- XFER VALVE - Manually operate as required 2. Land as soon as practical
Procedure for FUEL TRAPPED Caution
- TPUMP BOOST - ON2. XFER VALVE - AUTO3. Isolate tank declared trapAllow trapped tank to remain isolated for a minimum of 4 seconds4. De-Isolate tank declared trapped Reference PCL
Procedure for FEED TANK LOW Caution
- FMU/AERIAL REFUEL - Confirm Off2. PROBE OFF - Confirm3. TPUMP BOOST - ON4. XFER VALVE - AUTOIf feed tank does not replenish5. XFER VALVE - OPEN6. Isolate any empty CBN TNKIf feed tank does not replenish7. Maneuver Severity reduce8. Land as soon as possibleIf a safe landing cannot be made prior to the feed tank depleting below 300 lb9. Single Engine Profile - Establish10. Pull both FMU 1 and 2 circuit breakers simultaneously, wait 10 sec and simultaneously reset.If feed tank does replenish11. TPUMP BOOST - AUTO
Procedure for FEED TANK OVERFILL Caution
- Maneuver Severity - Reduce2. ALE-47 MODE Switch - OFFIf the feed tank is overfilled, to manually deplete the feed tank:3. TPUMP BOOST - OFF4. XFER VALVE - CLOSE5. SUCTION LIFT PUMP circuit breaker - Pull (Affected side)If condition persists6. Land as soon as possible, expedite shutdownIf condition is alleviated 7. SUCTION LIFT PUMP circuit breaker - As required8. XFER VALVE - AUTO 9. ALE-47 MODE switch - As required
Landing profile when landing with a fuel leak or venting
ROL, avoiding the use of aft nacelle is recommended to minimize ingestion of fuel into the engines and wheel brakes
FUEL ESTIMATE Advisory
A sensing element of a fuel quantity probe has malfunctioned, and an accurate measurement of fuel in the respective tank may not be possible
FUEL DUMP VLV FAIL Advisory
Dump Valve is not at its commanded position. The Dump Valve may be failed closed or partially open.
When is FUEL DUMP VLV FAIL Detected
This valve is not BIT checked, so the failure will be undetected until Fuel Dump is selected.
