Fuel System Flashcards
Explain fuel flow from fuel tanks to engine.
- Fuel supplied by fuel pumps located in the fuel tanks
- Flows through spar valves loc in main tank
- Passes through 1st stage fuel pump where pressure is added
- Passes through 2nd stage fuel pump adds more pressure
- Passes through fuel/oil heat exchanger
- Passes through fuel filter
- Goes into fuel metering unit
- Finally flows through the Engine Fuel Valve into the engine
What is the center tank capacity?
182,800 lbs
What is the total fuel capacity?
320,800 lbs
What is the capacity of the main tanks?
69,000 lbs
What is displayed on the EICAS when the fuel jettison switch is armed?
The jettison system automatically sets the fuel–to–remain to the MLW fuel quantity. The TO REMAIN quantity replaces fuel temperature on the EICAS display.
What do you do to dump to a weight lower than max landing weight?
Pull on and rotate the FUEL TO REMAIN selector to manually decrease or increase the TO REMAIN quantity
What is the minimum fuel to remain that the system will allow?
8,500 pounds/3800 kilograms
What kind of duration will the max dump leave you?
About 1 hours
What is the purpose of the extra cross feed valve?
To meet 2 engine ETOPs requirements and redundancy.
During preflight with all fuel pumps “off” you notice the left forward fuel boost pump pressure light is not illuminated. What causes this?
When the APU is running the left forward pump comes on automatically to supply the APU.
What other fuel pump source is available to the APU?
There is a DC fuel pump in the left main for APU start when no AC power is available.
What other functions does the DC pump provide?
In flight, the DC fuel pump operates automatically for quick left engine relight with the loss of both engines and all AC power.
How many pumps are in the left main tank?
Each fuel tank contains two AC–powered fuel pumps.
The left main tank also has a DC powered pump that operates automatically when no AC power is available.
A single AC pump can supply sufficient fuel to operate one engine under all conditions.
What is the sequence of fuel usage with center tank fuel?
Center first then main tanks.
What makes this sequence happen?
The two center tank fuel pumps are override/jettison pumps. The pumps have higher output pressure than the left and right main tank fuel pumps. The center tank override/jettison pumps override the main tank pumps so the center tank fuel is used before wing tank fuel.
