737 Fuel System

Question 1

Explain the meaning of an illuminated Main Tank Fuel Pump LOW PRESSURE light.

What would cause a MASTER CAUTION and FUEL system light to illuminate on the upper panel?

Answer 1

• Fuel pump output pressure is low - OR -
• FUEL PUMP switch is OFF

NOTE: Two LOW PRESSURE lights illuminated for the same fuel tank will illuminate a MASTER CAUTION and FUEL system annunciator light.

NOTE: One LOW PRESSURE light causes MASTER CAUTION and FUEL system annunciator lights to illuminate on MASTER CAUTION recall.

Question 2

Describe logic of blue cross feed VALVE OPEN light.

Answer 2

Bright blue - Valve in transit or the valve position and CROSSFEED Selector disagree

Dim Blue - Valve is open

Extinguished - valve is closed

Question 3

What is the logic of the blue ENGINE VALVE CLOSED and SPAR VALVE CLOSED lights?

Answer 3

Bright Blue:
- Valve is in transition, or
- Valve position and engine start lever or engine fire warning switch in are in disagreement

Dim Blue:
-Valve is closed

Extinguished:
- valve is open

Question 4

Describe meaning of an illuminated amber fuel FILTER BYPASS light.

What will happen if the filter becomes completely clogged?

Answer 4

Impending fuel filter bypass due to a contaminated filter.

Engine will bypass valve will open and fuel will be drawn into the engine directly from the tank.

Question 5

What is the meaning of a fuel quantity amber LOW alert?

Answer 5

• fuel quantity is less than 2000 lbs in the related main tank.

Question 6

What does an amber CONFIG alert below the fuel quantities mean?

Answer 6

See attached pic for answer

Question 7

What is the meaning of an amber IMBAL alert below the fuel quantities?

Answer 7

• the main tanks differ by more than 1000 lbs
• displayed below the main tank with the lower fuel quantity
• displays whether aircraft is in the air or on ground
• inhibited by LOW indication when both indications exist
• disappears when imbalance is reduced to 200 lbs

Question 8

What are two ways that the spar and engine fuel shutoff valves can be closed?

Answer 8

1. Place the engine start lever to cutoff
2. Pull the engine fire warning switch.

Question 9

How is fuel supplied to the engines with all pumps operating?

Answer 9

Center tank pumps produce higher pressure than main tank pumps which ensures that center tank fuel is used before main tank fuel.

NOTE: When main tank fuel pump pressure is low, each engine can draw fuel from its corresponding main tank through a suction feed line that bypasses the pumps.

Question 10

How many tanks on the aircraft?
How much fuel does each hold?
How much total fuel?

Answer 10

3 tanks - 2 wing and 1 center (although there are also two surge tanks in each wing)

Wing tanks - 8630 lbs each
Center tank - 28,803
Total - 46,063 lbs