Fuel System

Question 1

Where is the genesis of the air for the Nitrogen Generating System for C Fuel tank?

Answer 1

4 pneumatic ducts

Question 2

When do the C tank scavenge pumps start working?

Answer 2

<1200lbs
Main tanks below 50%

Question 3

What powers the C tank Scavenge pumps?

Answer 3

Mode of flow – differential between high and low flow (high pressure to low pressure)

Question 4

How many fuel pumps are there?

Answer 4

6 AC powered pumps (2 L + 2 R AC Fuel pumps, 2 C OVRD AC Pumps)
2 AC jettison pumps
1 DC APU pump

Question 5

When does the EICAS Fuel Imbalance message display?

Answer 5

2000lbs +/-500lbs

Question 6

How many fuel sensing probes are there, where do they send information?

Answer 6

1 L + 1R
2 C
Sends information to the fuel quantity processor

Question 7

What are the main functions of the fuel quantity processor?

Answer 7

Sends adjusted fuel information (temp/density) to:
Fuel quantity indicating system
Fuel totaliser via the FMC
Fuel Configuration light

Question 8

When is it acceptable to takeoff with a FUEL CONFIG light?

Answer 8

<5000lbs in C tank

Question 9

How much fuel do we burn per hour?

Answer 9

10,000lbs

Question 10

What does UFI stand for?

Answer 10

Universal Fault Interrupter circuitry

Question 11

What do the UFI’s do:

Answer 11

Approx 1200lbs:
EICAS Advisory (L)(R) Pump pressure Low
Boeing logic DEPOWERS both C pumps off
2 Fuel pump lights
Pilots turn off pumps

Question 12

L or R tank reaches 50% capacity, what happens?

Answer 12

High Pressure and Low pressure scavenge pumps (Not AC powered) take the remaining 1200lbs from C tank.

Question 13

What do the FMC fuel totaliser and the total fuel indication on the fuel quantity indicator have in common?

Answer 13

the same calculation

Question 14

When does the FUEL CONFIG light come on?

Answer 14

Fuel Imbalance 2000+/- 500
Low quantity <2200lbs in L or R tank
Turn off OVRD boost pumps with more than 1200lbs in C tanks

Question 15

Why aren’t the OVRD Boost pumps on for take off with less than 5000lbs in C tank?

Answer 15

Abnormal delays may cause transition from C OVRD boost pumps to L/R Boost pumps during critical phase

Question 16

When are the OVRD boost pumps inhibited? Why?

Answer 16

<50% N2
Electrical load required needs IDG to support load

Question 17

In the event of an engine shut down in flight, what happens to the OVRD boost pump for that engine?

Answer 17

<50% N2 the pump is load shed due to loss of generator

Question 18

Why is the OVRD pump inhibit removed with the refuelling door open?

Answer 18

Allows refuelled access to all fuel pumps

Question 19

On engine start, if >50N2 and the OVRD pressure light remains on as pump is un-inhibited, what has happened?

Answer 19

Fuel Panel door still open, or switch fault.

Question 20

Where is fuel temperature measured?

Answer 20

Left tank, because its coolest due to only 1 HYD fuel heat exchanger

Question 21

If Calculated and totaliser fuel don’t match how do you know?

Answer 21

Fuel disagree message displayed on the scratch pad

Question 22

When does the FMC light illuminate?

Answer 22

Whenever the FMC wants to tell you something, and is displaying information on the scratch pad

Question 23

When does the FMC light illuminate?

Answer 23

Whenever the FMC wants to tell you something, and is displaying information on the scratch pad

Question 24

What is the path of flow of fuel from the tank?

Answer 24

EEC commands fuel through the fuel metering unit.
Fuel fed from tank through:
Spar valve > 1st stage pump > 2nd stage pump > Heat Exchanger > Filter/Filter bypass > Fuel metering >Burner Can

Question 25

Can you jettison to zero fuel in C tank?

Answer 25

Yes. UFI inhibited

Question 26

When will the fuel disagree light illuminate?

Answer 26

> 3000lbs difference between totaliser and calculated fuel. Displayed on scratch pad

Question 27

Boeing Load-shed/inhibit logic during fuel jettison is?

Answer 27

L3 and R3 side window heat
Inhibit calculated and totaliser comparison fuel disagree for <3000lbs
Inhibit UFI circuitry

Question 28

When jettison selector moved to on, what happens?

Answer 28

Energising both jettison pumps
Both jettison transfer valves open
Fuel flows from centre tanks to closed jettison nozzles
In the back ground: L3 and R3 side window heat + Inhibit of FMC calculated fuel for fuel disagree for <3000lbs + Inhibit UFI circuitry

Question 29

What impacts the jettison fault light?

Answer 29

Either jettison pumps didn’t energise (1 or both)
jettison transfer valves didn’t open (1 or both)

Question 30

Jettison pump or transfer valves with fault light, does jettison have to stop?

Answer 30

No, valve partially open.

Question 31

What is the jettison rate?

Answer 31

2600lbs per minute
80600lbs in half an hour

Question 32

After jettison does fuel comparison and totaliser calculation return?

Answer 32

Yes

Question 33

If the wing tanks aren’t full, what is the maximum amount of fuel you are allowed to load in to the C Fuel tank?

Answer 33

22,050

Question 34

What depowers the C OVRD boost pumps?

Answer 34

Boeing logic through the UFI’s

Question 35

What light does the fuel quantity processor turn on?

Answer 35

Fuel Configuration light

Question 36

What type of heat exchangers are located in the wings?

Answer 36

Hydraulic

Question 37

What does UFI circuitry do?

Answer 37

Stops fuel leaving the C fuel tank at 1200lbs

Question 38

Where are the jettison nozzles located?

Answer 38

Inboard of the outboard ailerons