Fuel System Flashcards

1
Q

Explain fuel flow from fuel tanks to engine.

A
  • 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
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2
Q

What is the center tank capacity?

A

182,800 lbs

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3
Q

What is the total fuel capacity?

A

320,800 lbs

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4
Q

What is the capacity of the main tanks?

A

69,000 lbs

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5
Q

What is displayed on the EICAS when the fuel jettison switch is armed?

A

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.

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6
Q

What do you do to dump to a weight lower than max landing weight?

A

Pull on and rotate the FUEL TO REMAIN selector to manually decrease or increase the TO REMAIN quantity

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7
Q

What is the minimum fuel to remain that the system will allow?

A

8,500 pounds/3800 kilograms

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8
Q

What kind of duration will the max dump leave you?

A

About 1 hours

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9
Q

What is the purpose of the extra cross feed valve?

A

To meet 2 engine ETOPs requirements and redundancy.

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10
Q

During preflight with all fuel pumps “off” you notice the left forward fuel boost pump pressure light is not illuminated. What causes this?

A

When the APU is running the left forward pump comes on automatically to supply the APU.

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11
Q

What other fuel pump source is available to the APU?

A

There is a DC fuel pump in the left main for APU start when no AC power is available.

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12
Q

What other functions does the DC pump provide?

A

In flight, the DC fuel pump operates automatically for quick left engine relight with the loss of both engines and all AC power.

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13
Q

How many pumps are in the left main tank?

A

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.

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14
Q

What is the sequence of fuel usage with center tank fuel?

A

Center first then main tanks.

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15
Q

What makes this sequence happen?

A

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.

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16
Q

What is the fuel scavenge system?

A

When the main tank pumps are operating the fuel scavenge system transfers the fuel remaining in the center tank into the main tanks.