Fuel System

1
Fuel System
BY 744 FO ALPHA
2
Please explain system logics and function of the
following Switches of fuel system? X-feed valve
switch 1,2,3,4
The FSMCs close crossfeed valves 2 and 3 when
flaps extend to takeoff position on the ground.
Flaps out of range of flaps 10-----2,3 X-feed
valve open
3

• Fuel pumps switches

X-feed valve switch 1,4
Illuminated (amber) - crossfeed valve position
does not agree with switch position. ON (bar
visible) - crossfeed valve opens.
4
1.?CWT?80.4000 (67.000???),STB???? 2.?STB 2600
L??, 1300 R?? 3.?CWT 3000 CTR?? 4.MAIN
40,000 ?? RES ????(Jettison???)
5

• Fuel to remain selector

Rotate selects fuel to remain after
jettison displays value on EICAS
6

• Fuel jettison Nozzle valve switches/Valve light

ON - jettison nozzle valve selected open when
jettison system armed, activates
override/jettison and transfer/jettison pumps in
tanks containing fuel (pump switches must be
ON) Off - jettison nozzle valve selected closed.
7
Fuel jettison Nozzle valve switches/Valve light

• Fuel Jettison Nozzle VALVE Lights
• Illuminated (amber) jettison nozzle valve not
  in selected position.

8

• Fuel jettison selector

OFF disarms jettison system removes EICAS
fuel to remain indication
A or B arms jettison system displays
preselected fuel to remain on EICAS
9

• Fuel transfer main 14 switch

FUEL Transfer (XFER) MAIN 1 4 Switch ON
--- main 1 and 4 transfer valves open. Off
--- main 1 and 4 transfer valves open/ close when
commanded by system logic
10

• Fuel temperature is measured at which tank?

TANK 1

• Fuel Temperature
• Fuel temperature is measured in main tank 1 and
  displays on primary EICAS.
• The temperature normally displays in white.
• It displays in amber when the fuel temperature is
  -37C or below.
• During jettison, the TO REMAIN quantity replaces
  the EICAS display fuel temperature indication.

11

• What do you do if you have a gtFuel temp low
  MSG?
• Change ALT, Increase SPD, Deviate, Reroute
• or do nothing
• 0.1Mach0.5-0.7C, Below tropopause each
  1000ft--2
• In extreme condition ----descend below FL250
• When MSG display ?
• Fuel temperature -37or less
• Do we need to check the type of fuel being used?
• Yes
• Except JET A, Temp greater than -43---do nothing

12

• What is the stand pipe level during the fuel
  transfer valve operation for tank (14)?
• 7000 lb

13
If you have a both 2 main pump failed can you
use the 2 override pump to pump all fuel into
the 2 engine till last 2000lbs?
Yes You can, but last 7000lbs only by suction AOM
4.55/7
14
What is the difference between jet pumps and
scavenge pumps
B-18271 - B-18275 CWT fuel is scavenged by an
electric pump activated by system logic when one
CWT override/jettison pump has low output
pressure and/or when reserve tanks transfer.
After each activation, the pump will operate for
approximately two hours or until the scavenge
pump pressure is low, whichever occurs first. The
scavenged fuel is pumped into main tank
2. B-18201 - B-18251, B-18701 - B-18717 CWT fuel
is scavenged by four jet pumps, two pumping into
each main tank 2 and 3. Scavenge begins when main
tank 2 or 3 fuel quantity decreases to
approximately 60,000 pounds.
????Tank 2?? Elec. Pump, ?? Tank 2,3?? Jet pump
Elec. x 1???RES???(4?)??????Scavenge
???2??.(271-275) Jet x 4Main tank 2 or 3 6000lb
?????(????)
15
When you have a fuel suction feed, what is the
caution about that?

• As the airplane climbs, dissolved air is released
  from the fuel in the tank due to the decrease in
  air pressure. This air may collect in the suction
  feed line and restrict fuel flow. At high
  altitude, thrust deterioration or engine flameout
  may occur as a result of the fuel flow reduction.
• The dissolved air in the fuel tank will
  eventually deplete after reaching cruise
  altitude. The depletion time is dependent upon
  airplane altitude, fuel temperature, and type of
  fuel. Once the dissolved air is depleted, the
  engine may be capable of suction feed operation
  at cruise power.

16
What are meaning of fuel imbalance messages (1
4, 2 3 or inboard outboard)?
FUEL IMBAL 1-4 Advisory MSG Fuel difference of
3,000 pounds between main tanks 1 and 4. Message
no longer displayed when difference less than
1,000 pounds. FUEL IMBAL 2-3 Advisory MSG Fuel
difference of 6,000 pounds between main tanks 2
and 3. Message no longer displayed when
difference less than 1,000 pounds. FUEL
IMBALANCE Advisory MSG Fuel difference of 6,000
pounds between inboard main tanks and outboard
main tanks after reaching FUEL TANK/ENG
condition. Message no longer displayed when
difference less than 1,000 pounds.
17
Can the B744 be fueled if the left and right wing
fueling stations are unusable?
???????? Refueling Station, ? Control panel
??? ???? Main Tank 1,2,3,4 ??? Fill Port ?? ????.
18
What is the difference between Totalized and
calculated fuel?

• Totalized Fuel ????? Sensor Fuel
• Calculated Fuel ???? Metering Valve ??????????
• ??? Totalized Calculated
• Progress Page ????? Last Position ??? Calculated
  Fuel
• ? Calculated ? Totalized ? 9000 lb ???,?? MSG
  FUEL DISAGREE ,? Progress Page ????? USE

19
When will the reserve tank 2 and 3 transfer fuel?
Each reserve tank contains two transfer valves.
The valves open and fuel gravity transfers to
the inboard main tanks when main tank 2 or 3
fuel quantity decreases to 40,000 pounds.
20
How is the APU fuel being supplied?
B-18271 - B-18275 APU fuel is 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.
21
B-18201 - B-18251, B-18701 - B-18717 APU fuel is
normally supplied from main tank 2. When AC
power is available, fuel is supplied by main
pump 2 aft main pump 3 aft operates to
prevent tank-to-tank transfer and provides fuel
if main pump 2 aft fails. If AC power is not
available, a dedicated DC pump in main tank 2
supplies fuel to the APU.
22
What is the configuration of fuel system on GND
after flaps are in T/O position? What about
after T/O?
The FSMCs close crossfeed valves 2 and 3 when
flaps extend to takeoff position on the
ground. The FSMCs open crossfeed valves 2 and 3
when the flaps are retracted. The CWT
override/jettison pumps provide fuel to all
engines.
23
When will the jet pumps activate?
B-18201 - B-18251, B-18701 - B-18717 CWT fuel is
scavenged by four jet pumps, two pumping into
each main tank 2 and 3. Scavenge begins when
main tank 2 or 3 fuel quantity decreases to
approximately 60,000 pounds. Jet Pump x 4
?6000lb ??????? Main
tank 2 or 3
24
During fuel jettison the Main tank 14 transfer
valve will open when?
When either main tank 2 or 3 fuel quantity
decreases to 20,000 pounds during jettison, both
main tank 1 and 4 transfer valves open.
25
If CWT quantity drops below approximate
5000 Pd and total fuel consumption is greater
than 15000 pd/hr, is this configuration call
Shared flow situation? Please explain it.
When CWT quantity drops below approximately 5,000
pounds and Total fuel consumption is greater
than 15,000 pounds per hour, the CWT
override/jettison pumps can no longer provide
full override of the outboard main tank pumps.
As a result, a shared flow situation between the
CWT and outboard main tanks is established.
During this shared flow situation, approximately
2,000 pounds of fuel are consumed from each
outboard main tank prior to display of the EICAS
message FUEL LOW CTR.
26
Fuel jettison Sequences during the fuel jettison?
The FSMCs open the reserve transfer valves when
main tank 2 or 3 fuel quantity decreases to
40,000 pounds. Fuel transfers from reserve
tanks 2 and 3 to the related main tank.
When either main tank 2 or 3 fuel quantity
decreases to 20,000 pounds During jettison, both
main tank 1 and 4 transfer valves open.
27
Fuel Cross-feed Manifold ? Jettison Manifold
?? ??,????
28
Jettison timing is estimated by?
The jettison time is initially estimated using
preprogrammed rates. The system begins updating
the estimate based on Actual fuel quantity rate
of change ninety seconds after jettison begins.
29
QRH Messages By Examiners discretion
gtFUEL LO STAB L Horizontal stabilizer tank 8,000
in climb or 2600 in cruise
gtFUEL LO STAB R Horizontal stabilizer tank
quantity 8,000 in climb or 1,300 in cruise
gtFUEL LOW CTR L, R Center wing tank lt 17,000
before start, or 7,000 pounds in climb or 3,000
pounds in cruise with pump switches ON
gtFUEL OVD CTR L, R Center wing tank quantity
gt17,000 pounds on ground or 4,000 pounds in
cruise with Center Wing Tank Pump switch OFF