Fuel

Question 1

How many fuel tanks and what are the approx. capacities?

Answer 1

7 tanks
CWT = 52.2 T (kg)
Main 2 and 3 = 38.1 T (each)
Main 1 and 4 = 13.3 T
Res 2 and 3 = 4.0T

Question 2

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

Answer 2

FSMCs - Fuel System Management Cards

Question 3

Which cross feed valves are affected by flap extension on the ground?

Answer 3

Xfeed 2 and 3 (allows for engines 2 + 3 to be fed by respective tanks. CWT feeds engines 1+4

Question 4

Which fuel pumps are system logic pumps?
i.e which are commanded to turn on and off by system logic during normal operations?

Answer 4

Override/jettison fuel pumps 2+3

Question 5

Trace fuel flow of fuel to engines when there are >7700kgs fuel in CWT from block out

Answer 5

• CWT pumps turned on - CTR tanks feed all engines
• Flaps extended - CTR tanks feed engine 1 and 4, main tanks 2 and 3 feed respective engines (Xfeed valves 2+3 auto-close)
• Flaps retracted - CTR tanks feed all engines (xfeed valves 2+3 auto-open)
• ‘FUEL LOW CTR’ - OVD pump 2 feeds eng 1 and 2, OVD pump 3 feeds eng 3 and 4
• ‘TANK/ENG’ - Each main tank pumps feed their engine (xfeed valves 1 and 4 turned off, OVD pumps 2+3 turned off)

Question 6

When do the FSMCs open the reserve transfer valves

Answer 6

main tank 2 or 3 = 18,200kg

Question 7

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

Answer 7

• During fuel jettison, when main tank 2 or 3 reach 9,072kg
• XFR valves 1 and 4 open and gravity feed

Question 8

Can fuel be manually transferred from any tank to any other tank

Answer 8

No - no manual controls for reserve tank transfer

Question 9

What occurs when Fuel Jettison Switch is selected to either A or B?

Answer 9

• arms jettison system
• displays preselected fuel to remain on EICAS

Question 10

Describe how the fuel quantity indication changes upon termination of fuel jettison.

Answer 10

fuel to remain qty changes from magenta to white and flashes for 5 secs

Question 11

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

Answer 11

• jettison nozzle valve selected open
• when jettison system armed, activates override/jettison pumps in tanks containing fuel (pump switches must be ON)

Question 12

What is the source of fuel for the APU?

Answer 12

• Main tank 2
• AC power available: aft boost pumps in main tank 2/3 supply pressure (3 operates to prevent tank-to-tank transfer, provides fuel if main pump 2 aft fails)
  AC power not available: dedicated DC pump in main tank 2

Question 13

In general, how are fuel imbalance situations handled?

Answer 13

• opening/closing x-feed valves + turning off and on fuel pump switches
• wait for EICAS - see FUEL BALANCING supp procedure

Question 14

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

Answer 14

adversely affects CG, aerodynamic drag, and fuel
economy.

Question 15

When is an engine on suction feed, and how are suction feed situations corrected?

Answer 15

• Main tank fuel pump pressure low, each engine can draw fuel from main tank through suction feed line bypassing pumps
• correct by open x-feed valves: fuel pressure can be provided from main tank with operating pumps to another engine

Question 16

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

Answer 16

No - bypasses main tank fuel pumps

Question 17

A single Main Tank Fuel Pump can provide sufficient fuel to how many engines?

Answer 17

1 engine at takeoff thrust
2 engines at cruise thrust

Question 18

A single Main Tank 2 or 3 Override/Jettison Pump can provide sufficient fuel to how many engines?

Answer 18

2 engines at takeoff or cruise thrust

Question 19

Can the Main Tank 2 or 3 Override/Jettison Pump operate when the related Main Tank is below 3200 kgs (standpipe level)?

Answer 19

No

Question 20

Fuel tank temperature is measured in which tank?

Answer 20

Main tank 1

Question 21

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

Answer 21

-37 deg (3 more than Jet A limit)

Question 22

How is the Center Wing Tank fuel scavenged?

Answer 22

4 jet pumps - 2 to main 2, 2 to main 3

Question 23

What three different conditions will generate a fuel imbalance message on the EICAS?

Answer 23

• FUEL IMBALANCE = after reaching FUEL TANK/ENG condition - there is a longitudinal fuel imbalance of 2,720 kgs between inboard main tanks and outboard main plus reserve tanks. Message no longer displayed when difference less than 450 kgs.
• FUEL IMBAL 2-3 = Fuel difference of 2,720 between main tanks 2 & 3. Message no longer displayed when difference is less than 450 kgs.
• FUEL IMBAL 1-4 = Fuel difference of 1,360 between main tanks 1 & 4. Message no longer displayed when difference less than 450 kgs

Question 24

When does the fuel imbalance message no longer display on the EICAS?

Answer 24

difference < 450 kgs

Question 25

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

Answer 25

crossfeed valve opens when commanded by system logic

Question 26

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

Answer 26

crossfeed valve opens