Fuel

Question 0

Which tanks are used first?

Answer 0

Center tank is used first, with the main tank fuel used after the Center tank has been used.

Question 1

How is fuel normally loaded?

Answer 1

Normally - Fuel is loaded in the main wing tanks first, and if additional fuel capacity is required - fuel is loaded into the Center tank.

Question 2

How are boost pumps pwred, cooled and lubed?

Answer 2

Two AC powered boost pumps are installed for each tank to provide pressurized fuel from the tank to the engines and APU.
The pumps are cooled and lubricated by the fuel.

Question 3

How can the APU get fuel?

Answer 3

APU Fuel pressure is normally provided by a Tank 1 pump, however, the APU can suction feed from tank 1.
The APU can also receive fuel directly from the left pump in the Center tank.
If the Crossfeed Valve is open, the APU can receive fuel from a pump in Tank 2 or from the right pump in the Center tank.

Question 4

Can engines or APU suction feed from the Center tank?

Answer 4

No

Question 5

What & where are bypass valves?

Answer 5

Bypass valves are installed in the Main Tanks.
This feature allows the engines to suction feed from the respective Main Tank.
In addition, the Main Tanks can be defueled by suction defueling due to the operation of these bypass valves.

Question 6

Can the 737 dump fuel and transfer fuel from tank to tank when inflight?

Answer 6

No

Question 7

Where are fuel qty and alerts displayed?

Answer 7

Upper DU

Question 8

What and where are fuel floatsicks?

Answer 8

When necessary, maintenance personnel can determine tank quantity by use of Fuel Floatsticks.
Six fuel floatsticks are installed in each main tank and four in the center tank.
The floatsticks are used in conjunction with fuel correction charts.
The pilot will ensure the floatsticks are secured during the preflight inspection.

Question 9

Describe the fuel vent system:

Answer 9

Fuel Vent Lines allow air to enter the space in the tank as the fuel is consumed - and to provide a relief route for excess fuel if a tank is overfilled.
Therefore, the Vent system prevents damage to the wings due to excessive build up of a positive or negative pressure in the tanks.
The tanks are vented to surge tanks - which vent through a single opening at each wing tip.

Question 10

What type of pwr do fuel boost pumps use?

Answer 10

All fuel boost pumps require normal AC electrical power.
The two pumps in each fuel tank are each powered by different electrical busses to ensure that both pumps in one tank do not fail with a loss of one electrical bus.

Question 11

Is suction feed possible from the center tank?

Answer 11

No

Question 12

With fuel in all tanks, which tanks drain first?

Answer 12

The center tank boost pumps operate at a slightly higher pressure than the main tank boost pumps.
Therefore, the center tank will feed the engines and APU (before the main tanks) when all boost pumps are operating.

Question 13

What bus powers the cross feed valve?

Answer 13

Battery Bus

Question 14

What happens when both main tank lights LOW PRESSURE come on?

Answer 14

If two Main Tank LOW PRESSURE lights illuminate in the same tank, the MASTER CAUTION and FUEL system annunciator lights will automatically come on.

Question 15

What do center tank LOW PRESSURE lights mean?

Answer 15

The LOW PRESSURE lights for the Center tank pumps are different.
These lights are inhibited when the associated pump switch is selected to OFF or when the pump switch is on and the pump is providing normal output pressure.
Therefore the Center tank pump LOW PRESSURE lights illuminate if the associated Center Tank pump switch is ON - but the pump has low output pressure, which may be caused by pump failure or an empty fuel tank.

Question 16

When does the LOW light illuminate for the main tanks?

Answer 16

Inflight, if the fuel quantity is less than 2000 lbs (907 kgs) in either main tank, the indication displays amber and LOW appears below the digital quantity.
This amber display remains until the tank quantity increases to 2500 lbs (1134 kgs), during refueling.
Note: This LOW quantity display is inhibited on the ground.

Question 17

What does the CONFIG message mean?

Answer 17

On the ground or in flight, when at least one engine is operating, if the center tank pumps are producing no or low pressure, and center tank quantity is greater than 1600 lbs (726 kgs), the center tank quantity displays amber and CONFIG is displayed.
The CONFIG display remains until at least one center tank boost pump is producing sufficient pressure, or both engines are shut down, or center tank quantity is less than 800 lbs (363 kgs).

Question 18

Talk about IMBAL message:

Answer 18

Inflight, if the main tank quantities differ by more than 1000 lbs (453 kgs), the indication on the tank with lower quantity turns amber and IMBAL appears below the digital quantity display.
This display continues until on the ground, or the imbalance is reduced to 200 lbs (91 kgs).
Note: This display is inhibited by the fuel LOW indication when both conditions exist or when the aircraft is on the ground.

Question 19

Is total wt in FMU pages reliable with inop fuel gauge(s)?

Answer 19

No, must be manually entered

Question 20

The fuel panel quantity indicators, fueling valves, and tank shutoff float valves use DC power from the Xxx Bus.

Answer 20

Hot battery

Question 21

Where is the manual defuel valve and how does it work?

Answer 21

A Manual Defueling Valve is located under the right wing between the #2 engine and the refueling panel.
This valve connects the crossfeed manifold with the refueling manifold. It is used for Defueling or for Tank to Tank Transfer - when on the ground.