Fuel

Question 1

How is fueling accomplished?

Answer 1

Single-point pressure fueling station located on the right wing. The fueling station panel is energized when the panel door is open, powered by the hot battery bus. One of the following electrical sources must be available:
• External power connected, regardless if external power has been selected
• APU generator power
• Battery power (BAT switch must be ON)

Question 2

What does an IMBAL alert on the Fuel Quantity Indicator indicate?

Answer 2

Main tank fuel quantities differ by greater than 1000 lbs for greater than 60 seconds.

The IMBAL will display below the lower quantity fuel tank and turn the fuel quantity indication for the lower side amber. The alert will remain until the difference between the main tanks is 200 lbs or less. IMBAL is inhibited on the ground and with a LOW alert.

Question 3

What does the LOW alert on the Fuel Quantity Indicator indicate?

Answer 3

Either main tank has less than 2000 lbs for 30 seconds. The message remains until the associated main tank has greater than 2500 lbs.

Question 4

What does a CONFIG alert on the Fuel Quantity Indicator indicate?

Answer 4

The CONFIG alert shows when there is 1600 lbs or more in the center tank with both center tank boost pumps OFF and an engine is running.

Question 5

What does INSUFFICIENT FUEL on the Fuel Quantity Indicator indicate?

Answer 5

FMC fuel at the destination is predicted to be less than 2000 lbs.

Question 6

With all fuel pumps operating, what ensures center tank fuel is used before main tank fuel?

Answer 6

Higher fuel pump output pressure from the center tank pumps. Discharge check valves, located downstream of each fuel pump outlet, ensure the proper direction of fuel flow and prevent inadvertent transfer of fuel between tanks.

Question 7

When do the center tank fuel pumps shut off automatically?

Answer 7

Approximately 15 seconds of a continuous LOW PRESSURE light. Turning the respective FUEL PUMPS switch OFF will reset the automatic logic if the pump is switched back to ON. Therefore, the pump will again operate until the automatic shutoff logic is met.

Question 8

How is fuel provided to the engine(s) without the fuel pumps?

Answer 8

Each engine can draw fuel from its respective main tank through a suction feed line that bypasses the pumps. The center tank does not have the ability to suction feed.

NOTE: Suction feeding at high altitude may result in thrust deterioration or engine flameout due to decreased air pressure in the main fuel tanks. Fuel in the main tanks releases dissolved air that may collect in the suction feed bypass lines. Dissolved air will eventually deplete after reaching cruise altitude, depending on altitude, fuel temperature, and type of fuel. The main tank bypass valves may also be used for suction defueling by following a suction defueling procedure.

Question 9

When does the center tank fuel scavenge jet pump activate?

Answer 9

When main tank No. 1 fuel quantity decreases to 4500 lbs or less, a float valve to the scavenge jet pump opens and uses motive flow from the main tank No. 1 forward pump to transfer residual fuel from the center tank. Once the scavenge process begins, it continues for the remainder of the flight, transferring 220–450 lbs per hour.

Question 10

What is the purpose of the crossfeed valve?

Answer 10

crossfeed allows fuel to flow from any of the fuel tanks to either engine.

Question 11

What does the engine start lever control?

Answer 11

Fuel flow to the engines is controlled by fuel shutoff valves located in each engine and wing spar. The position of the fuel shutoff valves is controlled by the start levers below the throttles.

Question 12

What does a bright blue illumination of the VALVE OPEN on the Fuel panel indicate?

Answer 12

A bright ENG VALVE CLOSED light indicates the respective valve is in transit or disagrees with the start lever or FIRE SWITCH position.

Question 13

What does the dim illumination of an ENG VALVE CLOSED light indicate?

Answer 13

A dim ENG VALVE CLOSED indicates the valve is closed. When the valve is open and the start levers are in IDLE, the light is extinguished.

Question 14

What does a bright illumination of a SPAR VALVE CLOSED light indicate?

Answer 14

A bright SPAR VALVE CLOSED light indicates the respective valve is in transit or disagrees with the start lever or FIRE SWITCH position.

Question 15

Where could the APU suction feed fuel from?

Answer 15

Number one main tank only (left wing).

Question 16

Where is the Nitrogen Generation System operability indicator located?

Answer 16

The operability of the NGS is determined by the NGS operability indicator in the main wheel well adjacent to the Fire Control panel.