Fuel System Flashcards
What fuel tanks does the CRJ have?
- 1 Center Tank
- 2 Wing Tanks
- 2 Collector Tanks
Which pumps create motive flow?
Engine driven fuel pumps
Which pumps transfer from Center tank to wing tanks?
Transfer Ejectors
How does fuel get from wing tanks to collector tanks?
Gravity or scavenge ejectors
How does fuel get from collector tanks to engines?
Main ejectors
How does motive flow work?
Venturi flow effect created by engine driven fuel pumps
What must happen before the fuel system computer can transfer fuel from center tank to wing tanks?
- One of the two wing tanks drops below 94%.
- Center tank has fuel
- Engines are on allowing pumps to be on
What does selecting the L FUEL BOOST PUMP do?
Arms the fuel pump
When will boost pumps both turn on automatically?
When main ejector pressure is low
Why are pressure refueling limits higher than gravity limits?
Gravity fueling does not allow fuel to fill the space above the cap.
Which tank cannot be refueled using gravity fueling?
Center tank
Describe automatic cross fueling process:
Over 200lb Imbalance:
1. XFLOW pump turns on and indicates direction on EICAS page
2. Turns off when new tank has 50lbs more than tank its pulling from.
How would you manually cross flow should auto cross flow fail?
X FLOW OVERRIDE switch on top panel
What do you have to be careful with when manually cross flowing?
It will not stop (No protection)
What is the maximum fuel imbalance limit and what message would you receive if that limit were exceeded?
FUEL IMBALANCE caution message when over 800lbs (300lb limitation for takeoff)
Prior to engine start, why may auto cross flow move fuel to the left wing tank?
APU draws fuel from left side
Will the APU shutdown following an APU pump failure?
No, bypass valve allows gearbox pump to take over.
What would an “AUTO XFLOW INHIBIT” caution message mean?
Refuel/Defuel computer left on after refueling
How is fuel from the wings heated before reaching the engine?
Oil/Fuel heat exchanger
What is an MLI and why would you use it?
Magnetic Level Indicator
Used to manually check fuel level if computer fails
What prevents fuel from flowing to the outside of the lower wing during a turn?
One way flapper valves
What is the restriction when adding fuel to the center tank?
No more than 500 lbs in center tank until at least 4,400 lb in wing tanks.
What creates positive pressure in the wing fuel tanks?
NACA scoop
You notice after takeoff your center tank fuel quantity increases by 300 lbs. Why would that occur?
Fuel in the fuel lines flows into tank when AoA increases.
