Fuel System Flashcards
What path does a molecule take from the center tank to the engines?
- Center tank
- Transfer ejector
- Wings
- Gravity(primary), scavenger ejector(secondary)
- Collector tank
- Main ejector or boost pump
- SOV
- Filter
- Engines
Scavenger ejectors
2 in each wing and they transfer off the lowest part of the wing to the collector tank
How do ejectors move fuel
Motive flow
What creates motive flow
Eng. driven fuel pump
Transfer ejectors
Moves fuel from center tanks to the wings
What send fuel to the collector tanks
Flapper check valves through gravity and through the scavenger ejectors
Main ejectors
Sends fuel from the collector tanks to the eng. driven fuel pumps
What must happen before the fuel system computer can transfer from center tank to the wing tank?
One engine must be running and fuel in the main tanks below 94%
When will boost pumps turn on automatically?
If the main ejectors fail
What creates positive pressure in the wing fuel tanks?
NACA scoops and vent lines
Why are pressure refueling limits higher than gravity limits?
Fuel cap is lower than highest point in tank
What happens when fuel pressure is low with both pumps armed?
Both pumps will come on
What tank can’t be fueled using gravity?
Center tank
How would you manually cross flow if auto cross flow failed
Low side XFLOW switch
Why do you have to be especially careful during manual cross flow?
There are no protections until your imbalance is above 800 lbs
What indication would you receive if the Refuel/De-Fuel computer was left on?
“Auto XFLOW inhibit” status
How is the fuel kept above 5* C?
Oil/Fuel heat exchanger
What is the MLI?
Magnetic level indicator - to manually check fuel loads
Why might you see an increase in the center fuel tank after takeoff?
Fuel back flows through the vent lines
Where is the bulk temperature fuel probe and readout located?
EICAS right main tank
How do you reset FUEL USED value on the FUEL synoptic page
Fuel used reset through the EICAS menu page
What would it mean if the powered cross flow pump depiction on the EICAS synoptic page was Amber?
PSM 13-30-3
The pump failed
What are the functions of the fuel boost pumps?
PSM 13-40-1
- Supplies fuel to the engines during start
2. Backup to the main ejectors if they fail
What bus is the AZpU fuel pump on?
PSM 13-40-7
Battery bus
What prevents overfilling of the fuel tanks?
High level sensors
