FUEL SYSTEM Flashcards
Fuel system consists of
Centre tank
Two main tanks
Two surge tanks
Fuel x feed connects left and right fuel manifolds through 2 cross feed valves
Fuel pumps
Two centre override and jettison pumps
Two additional jettison pumps one in each of left and right tank (used to assist main jettison pumps jettison fuel)
Left and right main tanks contains two AC fuel pumps
Dc pump left main tank feeds fuel to APU
FQIS
Height and density to measure fuel quantity in tanks
Temp to measure fuel temp
Pre flight fuel pump panel
All pressure lights illuminated except for left forward fuel pump
When AC power is established and APU running the left forward fuel pump operates automatically and the pump pressure light is extinguished indicating the pump is in operation
Pump load shed on centre tank pumps
Due only one power source
Displayed as press light underneath
Centre tank pump pressures
Higher than main tank
Therefore will override main tank pumps to feed fuel
Fuel burn
Fuel burnt from centre tanks first because of higher output pressure
When below a fixed value, fuel low center msg will appear and this indicates pilot to turn off centre tank pump switches in normal ops
Pumps will turn off automatically after 15 seconds of low pressure but the switches must still be turned off
Scavenge pumps
Automatically transfer any residual fuel from centre tank to main tanks
Fuel to remain knob operation
Pushed in reverts to MLW
Pulled out you can select manually a different value
Jettison fuel
Arm
Fuel to remain knob select value, push in for MLW, pull out to manually adjust
Fuel jettison nozzle switches on
Nozzles can not open on the ground
Standpipes
Ensure at least 5200kgs of fuel remains in each main tank after fuel jettison is complete
Manually terminate jettison
Close both nozzles or
Deselecting the arm switch
How many fuel pumps associated with system
Two AC powered fuel pumps, two each tank
Two center tank fuel pumps, they are override and jettison pumps
DC powered pump in left tank
Provides fuel to APU when AC power not available and the APU selector is on
Center pump pressure has and will
Higher than L/R main pumps, this is so center tanks can be used before main tanks
Shutoff automatically after 15 seconds of continuous low pressure
Shutoff is inhibited during jettison
Operate only when electrical power sources are available on the ground
How many and purpose of surge tanks
One provided in each wing, outboard of each main tank
Fuel in surge tank and fuel remaining in refueling manifold is drained into main tanks
Centre tank scavenge system
Uses main tank fuel jettison pumps to transfer the fuel remaining in the centre tank when centre tanks not operating
Inhibited for 45 minutes after the fuel center pump switches are off
Following 45 minutes they operate for a maximum of 4 hours or until the AC is on the ground
FUEL IN CENTER EICAS msg
Displays when both center fuel pump switches are off with fuel in center tank
FUEL LOW CENTER EICAS msg
Displays when one or both center pump switches are on and the Center tank quantity is low
Fuel crossfeed system
Valves closed during normal operations
Closed crossfeed valves isolate the left and right systems
Either valve can be opened to feed an engine from the opposite fuel tank
FUEL CROSSFEED FWD OR AFT EICAS Msg
Valve position does not agree with switch position
Crossfeed light illuminates
FUEL IMBALANCE EICAS msg
Fuel quantity differs left and right main tanks
Fuel balancing is achieved how
By opening either crossfeed valve and turning off fuel pump switches for the fuel tank with lowest quantity
APU FUEL SUPPLY
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 tank DC fuel pump
Left AC or DC pump automatic operation
With AC power
Left forward AC pump operates automatically regardless of switch position, DC off
In flight the DC pump operates automatically for quick left engine relight with the loss of both engines and all AC power
Jettison time
Displays in minutes on the fuel synoptic, time increases with an increase in altitude
Fuel jettison with AC FWD CG and heavy
Fuel is automatically jettisoned from the centre tank first to keep the CG within limits
Main tank jettison pump operation is delayed
VH VOZ. OR VHVPH
5200kg of fuel remaining in each main tank as a minimum
VHVPH
3800kg
