Fuel System - Question Bank

Question 1

How many fuel tanks do we have and what is their approx capacities?

Answer 1

-7 Tanks
-CTR: 52.2kgs
-2&3 Mains: 38.1kgs
-1 & 4 Mains: 13.3kgs
-2&3 Reserves: 4.0kgs
Total: 163.0kgs

Question 2

What commands fuel valves to open or close and fuel pumps to turn on or off according to fuel management logic?

Answer 2

Fuel System Management Cards (FSMCs)

Question 3

Which XFEED valves are affected by flap extension on the ground?

Answer 3

2 & 3 XFEED valves are closed by FMCSs when flaps extend to T/O when on the ground.

Question 4

Which fuel pumps are system logic pumps? (Which turn on and off by system logic during norm ops)

Answer 4

OVRD/JETT pumps 2 & 3.

They are inhibited when PX is detected from both CTR OVRD/Jett pumps

Question 5

Trace the flow of fuel to the engines when there are 7700kgs or more fuel in the CWT from blockout.

Answer 5

• Both CWT pump switches should be on
• XFEED Valves 2 & 3 close when flaps extended for T/O
• CWT pumps feed engines 1 & 4
• Main pumps 2 & 3 feed related engine

Question 6

Trace the flow of fuel to the engines when there is less than 7700 kgs of fuel in
the center wing tank, from blockout.

Answer 6

• Both CWT tank pumps should be off.
• X-feed valves 2 and 3 close when flaps extended for takeoff.
• Override/jettison pumps 2 feed engine 1
• Override/jettison pumps 3 feed engine 4.
• Main pumps 2 and 3 feed their related engine.

Question 7

When do the FSMCs open the reserve transfer valves?

Answer 7

• When main tank 2 or 3 fuel quantity decreases to approximately 18,200
kgs.
• Fuel transfers from reserve tanks 2 and 3 to the related main tank.

Question 8

Under what conditions would fuel automatically transfer from main tanks 1 and
4 to their adjacent tanks 2 and 3?

Answer 8

During fuel jettison, when either main tank 2 or 3 fuel quantity decreases
to 9,072 kgs.

Question 9

Can fuel be manually transferred from any tank to another tank?

Answer 9

• Yes, there is a Main Tank 1 and 4 Transfer Switch on the overhead
panel.
• Fuel can transfer from the outboard to the inboard main tanks, to
approximately 3,200 kgs remaining in each outboard main tank.

Question 10

State what 2 events occurs when you select the Fuel Jettison Switch to A or B.

Answer 10

• Arms the jettison selector.

* Displays preselected fuel to remain on EICAS

Question 11

Describe how the fuel quantity indication changes upon termination of fuel
Jettison

Answer 11

• The fuel to remain quantity indication changes from magenta to white.
• The fuel to remain quantity flashes for 5 seconds.

Question 12

What occurs when you push either fuel jettison nozzle valve to ON during the
QRH fuel jettison procedure?

Answer 12

• It activates all override/jettison pumps in the tanks containing fuel (pump
switches must be on).
• The required jettison nozzle valve also opens.

Question 13

What is the source of fuel for the APU?

Answer 13

• Normally supplied from main tank 2.
• When ac power is available, fuel is supplied by main pump 2 aft.
• If AC power is not available, a dedicated DC pump in main tank 2
supplies fuel to the APU.
• Main pump 3 aft operates to prevent tank to tank transfer and provides
fuel if main pump 2 aft fails (with aircraft exceptions)

Question 14

In general, how would you handle a fuel imbalance situation?

Answer 14

By opening or closing crossfeed valves and turning off and on fuel pump
switches (refer to QRH and Supplementary Procedures)

Question 15

What is the impact on the aircraft of excessive fuel imbalance?

Answer 15

• Adversely affects CG
• Aerodynamic drag
• Fuel economy

Question 16

When is an engine on suction feed, and how would you correct a suction feed
situation?

Answer 16

• An engine is on suction feed when main tank fuel pressure is low.
• Open the appropriate fuel crossfeed valve from a main tank with
operating pumps.

Question 17

Does the suction feed line go through the main tank fuel pumps?

Answer 17

No, the suction feed line bypasses the pumps

Question 18

A single main tank fuel pump can provide sufficient fuel to how many engines?

Answer 18

• One engine at takeoff thrust

* Two engines at cruise thrust.

Question 19

A single main tank 2 or 3 override/jettison pump can provide sufficient fuel
to how many engines?

Answer 19

Two engines at takeoff and cruise conditions

Question 20

Can the main tank 2 or 3 override/jettison pumps operate when the related Main tank is below 3,200 kgs (standpipe level)

Answer 20

No

Question 21

Fuel tank temperature is measured in which tank?

Answer 21

Main Tank 1

Question 22

When does the fuel temperature display on primary EICAS display in amber?

Answer 22

-37 C or below

Question 23

Which aircraft are the only ones with horizontal stabilizer tanks?

Answer 23

Passenger aircraft

Question 24

How is Center Wing Tank Fuel scavenged?

When does scavenge begin?

Answer 24

• CWT fuel is scavenged by 4 jet pumps, two pumping into each main tank
2 and 3.
• Scavenge begins when main tank 2 or 3 fuel quantity decreases to
approximately 27,200 kgs.

Question 25

What are the fuel imbalance differences that would generate an EICAS Advisory
message?

Answer 25

• 1360 between tanks 1 and 4
• 2720 between tanks 2 and 3
• 2720 between inboard and outboard tanks after FUEL TANK/ENG

Question 26

When correcting a fuel imbalance condition, when would you expect the associated
EICAS Advisory IMBAL message to no longer display?

Answer 26

< 450kgs

Question 27

What does a Crossfeed Valve ON, with the bar visible, indication mean for
Crossfeed Valve Switches 2 and 3?

Answer 27

Crossfeed valve open when commanded by system logic

Question 28

What does a Crossfeed Valve ON, with the bar visible, indication mean for
Crossfeed Valve Switches 1 and 4?

Answer 28

The crossfeed valve is open

Question 29

What does it mean when the main tank 2 and 3 Override (OVRD) Fuel Pump
Switches are ON? How about OFF, ON not visible?

Answer 29

• ON – fuel pump operates when commanded by system logic.

* OFF (ON not visible) – fuel pump selected OFF.