Fuel Flashcards
Crossfeed Selector Knob LOW 1 (2)/OFF
LOW 1 (2) - opens crossfeed valve and activates AC fuel pump, supply fuel to both engines from one wing tank OFF - closes crossfeed valve
DC Fuel Pump Selector Knob AUTO/OFF/ON
OFF - deactivates DC fuel pump
AUTO - operates DC fuel pump according to system logic
ON - activates the DC fuel pump
AC Fuel Selector Knob AUTO/OFF/ON
OFF - deactivates associated AC fuel pump
AUTO - operates AC fuel pumps according to system logic
ON - activates the AC fuel pump
Each wing tank incorporates:
- a collector tank
- a surge tank
What is the purpose of the collector tank
keeps fuel pumps submerged ensuring a constant fuel flow
Describe vent tank
ensures a differential pressure between tank and ambient and prevents fuel spillage during flight maneuvers, vented through vent lines and supplemented by a high capacity pressure relief valve to guard against fuel tank overpressure
Fuel quantity indication
- thirteen electrical sensors in each tank
- additional independent fuel low lever sensor
- three magnetic level indicator under each wing
Each fuel tank contains the following pumps
- ejector fuel pump
- AC electric fuel pump
- three scavenge ejector pumps
- DC electric fuel pump (right tank only)
Describe the primary ejector pump
- venturi ejector pump
- no moving parts
- powered by motive flow
The AC electric fuel pump supplies fuel to the following components
- onside engine during engine starts
- cross side engine during crossfeed operations
- APU when engine is not running
- backup if ejector pump fails
What busses power which AC fuel pump
left - AC BUS 1
right - AC ESS BUS
Describe the scavenge ejector pumps
three scavenge jet pumps maintain fuel level in collector tank
Describe the DC fuel pump
- installed in right wing only
- provides pressurized fuel for APU operation and engine start when AC pumps not available
- powered by DC ESS BUS 2
When will the fuel low level warning activate
660 lbs remaining in associated tank
FUEL 1 or 2 LO LEVEL warning
low level senors indicate that 660 lbs of fuel remain in respective tank
APU FUEL SOV FAIL caution
shutoff valve is not in the commanded position
ENG 1 or 2 FUEL SOV FAIL caution
associated shutoff valve is not in the commanded position
FUEL IMBALANCE caution
indicates an imbalance of fuel between the two tanks of greater than or equal to 800 lbs. it remains displayed until the imbalance is reduced to 100 lbs
FUEL TANK LO TEMP caution
temperature sensed in the left collector bay is less than or equal to -40C
FUEL XFEED FAIL caution
indicates a discrepancy between the cockpit control position and either the valve position or the affected pump status
DEFUEL SOV OPEN advisory
defuel shutoff valve is open
FUEL AC 1 or 2 PUMP FAIL advisory
indicates a discrepancy between the commanded and actual pump state
FUEL DC PUMP FAIL advisory
indicates a discrepancy between the commanded and actual pump state
FUEL EQUAL XFEED OPEN advisory
the imbalance is less than 100 lbs and the crossfeed valve is open
