Training Manual
B 737-300/400/500
ATA 28
FUEL
ATA 104 LEVEL 3
Book No:
B737-3 28 L3 E
Lufthansa
Technical Training GmbH
Lufthansa Base
For Training Purposes Only
 Lufthansa 1995
For training purposes and internal use only.
Copyright by Lufthansa Technical Training GmbH.
All rights reserved. No parts of this training
manual may be sold or reproduced in any form
without permission of:
Lufthansa Technical Training GmbH
Lufthansa Base Frankfurt
D-60546 Frankfurt/Main
Tel. +49 69 / 696 41 78
Fax +49 69 / 696 63 84
Lufthansa Base Hamburg
Weg beim Jäger 193
D-22335 Hamburg
Tel. +49 40 / 5070 24 13
Fax +49 40 / 5070 47 46
B737-3 28 L3 E
TABLE OF CONTENTS
ATA 28 FUEL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1
28-00
FUEL GENERAL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
DESCRIPTION AND OPERATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
PANEL DESCRIPTION (COCKPIT) . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
PANEL DESCRIPTION (COCKPIT) . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
PANEL DESCRIPTION (FUELING STATION) . . . . . . . . . . . . . . . . . . . .
2
2
4
6
8
28-10
STORAGE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
TANKS DESCRIPTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
FUEL TANK ACCESS PANEL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
BAFFLE CHECK VALVES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
TANK DRAIN VALVES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
CENTER TANK DRAIN VALVES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
APU SHROUD DRAIN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10
10
12
16
18
22
24
28-20
FUEL VENT SYSTEM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
TANK VENT SYSTEM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
VENT SCOOP AND FLAME ARRESTER . . . . . . . . . . . . . . . . . . . . . . . .
FLAME ARRESTER PRESSURE RELIEF VALVE . . . . . . . . . . . . . . . .
26
26
28
28
28-30
PRESSURE FUELING SYSTEM . . . . . . . . . . . . . . . . . . . . . . .
PRESSURE FUELING STATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
FUELING OPERATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
FUELING MANIFOLD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
FUELING CIRCUIT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
FLOAT SWITCH . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
OVERWING FUELING PORT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
30
30
32
34
36
38
40
28-40
FUEL FEED SYSTEM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
ENGINE FUEL FEED SYSTEM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
ENGINE FUEL FEED SYSTEM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
FUEL BOOST PUMPS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
MAIN AND CENTER TANK BOOST PUMP POWER CONTROL . . .
BOOST PUMP CHECK VALVES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
ENGINE FUEL FEED VALVES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
ENGINE FUEL SHUTOFF VALVE SWITCHES . . . . . . . . . . . . . . . . . . .
DEFUELING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
42
42
44
46
48
50
52
56
58
FRA US/T
Sep 2002
28-50
CENTER TANK FUEL SCAVENGE SYSTEM . . . . . . . . . . .
CENTER TANK FUEL SCAVENGE SYSTEM . . . . . . . . . . . . . . . . . . . .
FUEL SCAVENGE SYSTEM CONTROL LOGIC . . . . . . . . . . . . . . . . . .
FUEL SCAVENGE JET PUMP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
60
60
62
64
28-60
FUEL QUANTITY INDICATING SYSTEM . . . . . . . . . . . . . . .
FUEL QUANTITY INDICATING SYSTEM . . . . . . . . . . . . . . . . . . . . . . . .
FUEL QUANTITY INDICATION CIRCUIT . . . . . . . . . . . . . . . . . . . . . . . .
FUEL QUANTITY SYSTEM BUSSING PLUG AND TRANSIENT
SUPPRESSION DEVICE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
FUEL QUANTITY INDICATOR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
FUEL QUANTITY INDICATOR TEST . . . . . . . . . . . . . . . . . . . . . . . . . . .
MEASURING STICK . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
66
66
68
70
72
74
78
28-70
FUEL FEED LOW PRESSURE INDICATING SYSTEM . . .
FUEL FEED LOW PRESSURE INDICATING SYSTEM . . . . . . . . . . . .
FUEL FEED LOW PRESSURE INDICATING SYSTEM . . . . . . . . . . . .
82
82
84
28-80
FUEL TEMPERATURE INDICATING SYSTEM . . . . . . . . .
FUEL TEMPERATURE INDICATING SYSTEM . . . . . . . . . . . . . . . . . . .
86
86
Page i
B737-3 28 L3 E
TABLE OF FIGURES
Figure 1
Figure 2
Figure 3
Figure 4
Figure 5
Figure 6
Figure 7
Figure 8
Figure 9
Figure 10
Figure 11
Figure 12
Figure 13
Figure 14
Figure 15
Figure 16
Figure 17
Figure 18
Figure 19
Figure 20
Figure 21
Figure 22
Figure 23
Figure 24
Figure 25
Figure 26
Figure 27
Figure 28
Figure 29
Figure 30
Figure 31
Figure 32
Figure 33
Figure 34
Figure 35
FRA US/T
Fuel Tank Arrangement . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Fuel Quantity Indicating System (Cockpit) . . . . . . . . . . . .
Fuel Control and Warning (Cockpit) . . . . . . . . . . . . . . . . . .
Refuel Station . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Fuel Tanks and Access Panels . . . . . . . . . . . . . . . . . . . . . .
Fuel Tank Access Panel . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Center Tank Access Panel . . . . . . . . . . . . . . . . . . . . . . . . . .
Baffle Check Valves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Main Tank Sump Drain Valve . . . . . . . . . . . . . . . . . . . . . . .
Surge Tank Sump Drain Valve . . . . . . . . . . . . . . . . . . . . .
Center Tank Sump Drain Assembly and Valve . . . . . . . .
APU Fuel Line Shroud Drain . . . . . . . . . . . . . . . . . . . . . . .
Fuel Vent System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Vent Scoop / Flame Arrester Pressure Relief Valve . . .
Pressure Fueling Station . . . . . . . . . . . . . . . . . . . . . . . . . .
Pressure Fueling System . . . . . . . . . . . . . . . . . . . . . . . . . .
Fueling Manifold . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Pressure Fueling Electrical Schematic . . . . . . . . . . . . . .
Fuel Tank Float Switches . . . . . . . . . . . . . . . . . . . . . . . . . .
Overwing Fueling Ports . . . . . . . . . . . . . . . . . . . . . . . . . . .
Basic Schematic - Engine Fuel Feed System . . . . . . . .
Fuel Feed System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Fuel Boost Pumps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Main and Center Tank Fuel Boost Pump Power Control
Boost Pump Check Valves and Bypass Valve . . . . . . . .
Engine Fuel Feed Valves . . . . . . . . . . . . . . . . . . . . . . . . . .
Fuel Valve Electrical Circuit . . . . . . . . . . . . . . . . . . . . . . . .
Engine Fuel Shutoff Valve Switches . . . . . . . . . . . . . . . .
Manual Defueling Valve . . . . . . . . . . . . . . . . . . . . . . . . . . .
Center Tank Fuel Scavenge System . . . . . . . . . . . . . . . .
Fuel Scavenge System Control Logic . . . . . . . . . . . . . . .
Fuel Scavenge Jet Pump Check . . . . . . . . . . . . . . . . . . .
Fueling System Schematic . . . . . . . . . . . . . . . . . . . . . . . .
Fuel Quantity Indicating Schematic . . . . . . . . . . . . . . . . .
Component Location . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Sep 2002
3
5
7
9
11
13
15
17
19
21
23
25
27
29
31
33
35
37
39
41
43
45
47
49
51
53
55
57
59
61
63
65
67
69
71
Figure 36
Figure 37
Figure 38
Figure 39
Figure 40
Figure 41
Figure 42
Figure 43
Fuel Quantity Indicator . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Fuel Quantity Indicator Test . . . . . . . . . . . . . . . . . . . . . . .
Fuel Qty. Ind. Error Code Table . . . . . . . . . . . . . . . . . . . .
Fuel Measuring Stick . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Fuel Measuring Stick . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Fuel Feed Low Pressure Indicating System . . . . . . . . . .
Fuel Feed Low Pressure Indicating System Schematic
Fuel Temperature Indicating System . . . . . . . . . . . . . . . .
73
75
77
79
81
83
85
87
Page ii
B737-300/400/500
28-00
ATA 28
FUEL
For Training Purposes Only
Lufthansa Technical Training
FUEL
FRA US/E ur
Oct.96
Page: 1
Lufthansa Technical Training
FUEL
GENERAL
B737-300/400/500
28-00
28-00
FUEL GENERAL
DESCRIPTION AND OPERATION
The Fuel System
- stores and distributes fuel for running the engines and the APU.
- consists of:
S tank No. 1 and No. 2 (integral wingtanks)
S center tank (three cavities)
S Fuel Vent System
S Pressure Fueling System
S Fuel Feed System and
S Indicating and Warning System
For Training Purposes Only
General System Features
The volume of each tank is larger than the full tank fuel capacity to allow for
expansion and vent space. The surge tanks are normally empty and have a
capacity of 30 U.S. Gallons. Fuel is loaded on airplane from a ground source
through a fueling receptacle in the pressure fueling station. The tanks can be
refueled simultaneously or one after another. Fuel can also be loaded into
tanks No. 1 and No. 2 through overwing fueling ports.
The wingtanks No. 1 and No. 2 have to be refueled at first, until the normal
maximum capacity.
The remainder fuel must be filled into the center tank.
Operation
Electric motor-driven pumps and fuel lines deliver fuel from any tank to one or
both engines.
Fuel from boost pumps can also be delivered through a defueling valve
( manual operated on ground only ) into fueling manifold for removal and tankto-tank transfer.
A Fuel Dump System is not installed.
A Fuel Scavenge System transfered the residual fuel in the center tank into
tank No. 1 by a jet pump when the last center tank boost pump switch has
been switched to off.
Fuel quantity indicators in the flight compartment, and fueling quantity indicators at the pressure fueling station, indicate the quantity of fuel on the airplane.
Measuring sticks are installed on the underside of the tank No. 1 and No. 2.
only. They can be used as an alternate method to determine the fuel quantity.
Fuel low pressure lights indicate low engine boost pump outlet pressure and a
fuel temerature indicator shows the fuel temperature in tank No. 1 on the forward overhead panel.
The APU is supplied by a additional DC operated boost pump from fuel tank
No. 1 during starting.
FRA US/E ur
Feb. 2000
Page: 2
Lufthansa Technical Training
FUEL
GENERAL
B737-300/400/500
28-00
SURGE TANK
NO. 2 TANK
For Training Purposes Only
NO. 1 TANK
SURGE TANK
CENTER
TANK
Figure 1
FRA US/E ur
Feb. 2000
Fuel Tank Arrangement
Page: 3
Lufthansa Technical Training
FUEL
GENERAL
B737-300/400/500
28-00
PANEL DESCRIPTION (COCKPIT)
The Fuel Quantity Indicators (3)
- are installed in the pilots center panel
- consits of
S a microcomputer and
S a Liquid Christal Display
- indicate the usable fuel of the respective tank
- send the fuel value to the Fuel Summation Unit
- memories and display faults in the fuel quantity system
by error codes 0-9
The Trim Adjustment Screws (3)
- are installed at the forward pedestal area below captians handmike
- allow to adjust the capacity value, of the fuel quantity indication components, up to each fuel quantity indicator
Note:
The Trim Adustment Screws allow to change the fuel quantity indicators without indicator adjustment.
Note:
The fuel quantity indicators for tank No. 1 and No. 2 in the cockpit are identical
and fully interchangeable with the indicators No. 1 and No. 2 at the pressure
fueling station. The center tank indicators can also be interchanged between
cockpit and fueling station.
The Fuel Summation Unit
- is installed at the right hand side over the first officers seat
- added the fuel values of the fuel quantity indicators and send the signal
to the Flight Management Computer System (FMCS)
For Training Purposes Only
The Control Display Units (CDU) (2)
- are installed in the forward pedestal
- receives and displays data from FMCS
- displays the actual added fueling signal
The Fuel Quantity Test Switch
- is installed at the right hand side of the center tank indicator
- checks the fuel quantity indicators simultaneously when pushing
FRA US/E ur
Feb. 2000
Page: 4
Lufthansa Technical Training
FUEL
GENERAL
B737-300/400/500
28-00
FUEL
CONTROL
PANEL
CATHODE
RAY TUBE
(CRT)
FUEL
SUMMATION
UNIT
MASTER CAUTION
ANNUNCIATOR
FUEL
FMC
FUEL
QUANTITY
INDICATORS
TEST SWITCH
LINE
SELECT
KEY
INITIAL
REFERNCE
BUTTON
CTR
BRT
QTY TEST
FUEL
ERR
CAPACITANCE
TRIMMER
(3 LOCATIONS)
For Training Purposes Only
%
FUEL
FUEL QUANTITY
CALIBRATION
CTR TANK
FUEL
TANK 1
ERR
ERR
%
%
CRT BRIGHTNESS
CONTROL KNOB
TANK 2
HAND MIKE JACK
INIT
REF
RTE
DIR
INTC
LEGS
N1
LIMIT
FIX
D PREV
S PAGE
P
Y W
NEXT
PAGE
CLB
CRZ
DES
DEP
ARR
HOLD
PROG EXEC
A
B
C
D
E
F
G
H
I
J
1
F
A
4
I
L A
7
2
3
K
L
M
N
O
5
6
P
Q
R
S
T
8
9
U
V
W
X
Y
.
0
+/-
Z
DEL
/
CLR
FUEL QUANTITY INDICATORS
M
S
W G
W
CONTROL DISPLAY UNIT (CDU)
Figure 2
FRA US/E ur
Feb. 2000
Fuel Quantity Indicating System (Cockpit)
Page: 5
Lufthansa Technical Training
FUEL
GENERAL
B737-300/400/500
28-00
PANEL DESCRIPTION (COCKPIT)
The Engine Fuel Shutoff Valve Position Indicating Light (2)
- indicates the position of the Engine Fuel Shutoff Valve
S OFF - Valve open
S ON (bright) - Valve in transit or disagree between valve and switch
position
S ON (dim) - Valve in close position
The Master Caution Fuel Light
- at the annunciator panel will illuminates when both Fuel Low Pressure
Indicating Lights of a tank are ON.
Exception: One center tank boost pump switch is in OFF position
and the second center tank Fuel Low Pressure Indicating Light comes on.
The Fuel Temperature Indicator
- indicates fuel temperature of tank No. 1
The Crossfeed Valve Position Indicating Light
- indicates the position of the Crossfeed Valve
S OFF - Valve closed
S ON (bright) - Valve in transit or disagree between valve and switch
position
S ON (dim) - Valve open
The Crossfeed Valve Switch
- controls the Crossfeed Manifold Valve
- connects the engine No. 1 and No. 2 fuel feed lines in order to supply
engine No. 2 out of the tank No. 1 for example, or for fuel transfer on
ground
For Training Purposes Only
The Fuel Boost Pump Switch (6)
- turns on the fuel boost pumps in position ON
The Fuel Low Pressure Indicating Light (6)
- monitors the fuel output pressure of the respective fuel boost pump
S ON - Low pressure ( defective boost pump or low fuel level in the
tank ) or fuel boost pump switch in OFF position
S OFF - Respective boost pump switch in ON and pump delivers sufficiently fuel pressure
Note:
The low pressure lights of the center tank do not illuminate, when the respective fuel boost pump switch has been switched to OFF position.
FRA US/E ur
Feb. 2000
Page: 6
Lufthansa Technical Training
FUEL
GENERAL
B737-300/400/500
28-00
ENGINE FUEL
SHUTOFF VALVE
POSITION
INDICATING
LIGHT
OVERHEAD
FUEL PANEL
P5
FUEL VALVE
CLOSED
B
MASTER
CAUTION
LIGHTS
CROSSFEED
VALVE
POSITION
INDICATING
LIGHT
-40
+40
C
FILTER
BYPASS
VALVE
OPEN
A
CROSS
- ENGINE
START
LEVER
- FIRE HANDLE
ÉÉÉ
ÉÉÉ
ÉÉÉ
ÉÉÉ
FIRE
WARN
FUEL LOW
PRESSURE
INDICATING
LIGHT
(6 PLACES)
MASTER
CAUTION
ÉÉÉÉ
ÉÉÉÉ
ÉÉÉÉ
ÉÉÉÉ
ÉÉÉÉ
ÉÉÉÉ
ÉÉÉÉ
BELL CUTOUT PUSH TO RESET
FLT CONT
ELEC
IRS
APU
FUEL
FUEL BOOST
PUMP SWITCH
(6 PLACES)
FILTER
BYPASS
B
A
FEED
LOW
LOW
PRESSURE PRESSURE
A
A
CROSSFEED
VALVE
SWITCH
For Training Purposes Only
0
FUEL +20
TEMP
-20
FUEL
TEMPERATURE
INDICATOR
(TANK NO. 1)
FUEL VALVE
CLOSED
B
FUEL PUMPS
OFF
L
R
ON
CTR
LOW
LOW
PRESSURE PRESSURE
A
A
AFT
LOW
LOW
PRESSURE PRESSURE
A
A
FWD
FWD
OFF
AFT
OFF
FUEL
ON
1
OVHT/DET
PUMPS
ON
2
LEFT LIGHT SHIELD FUEL FAULT LIGHT
Figure 3
FRA US/E ur
Feb. 2000
Fuel Control and Warning (Cockpit)
Page: 7
Lufthansa Technical Training
FUEL
GENERAL
B737-300/400/500
28-00
PANEL DESCRIPTION (FUELING STATION)
The Refuel Station
- consits the following components for monitoring and controling for refueling / defueling and fueling transfer
S Refuel Panel
S Fueling Receptacle
S Fueling Power Control Switch
S Fueling Valves
The Fueling Valve (3)
- is an electrical controled and hydraulical operated valve
- has a fueling solenoid with a manual override button
S opens, when the fueling solenoid is energized and refuel pressure
availabe
S closes, when the fueling solenoid is deenergized or no refuel pressure
available
The Test Gages & Aux Fueling Power Control Switch
- is normal in OFF position
- has two spring loaded positions
S Test Gages - Used to test fuel quantity system
S Aux Fueling Power Control - Energizes fueling system if fueling
power control switch fails to activate system when door is opened
The Fueling Power Control Switch
- supplies the refuel station with 28 Volt/DC and 115 Volt/AC Power, when
the access door is in open position
The Fueling Valve Position Light (blue) (3)
- indicates the energizing of the fueling valve solenoid
S ON - Fueling valve solenoid is energized
S OFF - Fueling valve solenoid is deenergized
- is a push to test light
For Training Purposes Only
The Fueling Valve Switch (3)
- controls the voltage supply for the fueling valve solenoid
S OPEN - 28 Volt/DC for the fueling valve solenoid available
S CLOSE - Fueling valve solenoid deenergized
The Fueling Quantity Indicator (3)
- indicates the actual fuel quantity of the respective tank
- receives the fuel quantity signal from the fuel indicator in the cockpit
- displays faults in the fuel quantity indication system
by error codes A, F and 8
- is interchangeable with the fuel quantity indicator in the cockpit
FRA US/E ur
Feb. 2000
Page: 8
Lufthansa Technical Training
FUEL
GENERAL
B737-300/400/500
28-00
FUELING
RECEPTACLE
FUELING POWER
CONTROL SWITCH
REFUEL STATION
REFUEL PANEL
(P15 PANEL)
WING
LEADING
EDGE
ACCESS
DOOR
FWD
PANEL
LIGHTS
TEST GAGES &
AUX FUELING POWER
CONTROL SWITCH
REFUEL STATION
VALVE
TEST
GAGES &
FUELING
POSITION
b
b
LIGHTS
FUELING VALVE
POSITION LIGHTS
b
CENTER TANK
TANK No.1
TEST TANK No.2
GAGES
OPEN
OPEN
OPEN
FUELING VALVE SWITCHES
OFF
For Training Purposes Only
AUX FUELING
POWER CONTROL
FUEL
CLOSED
CLOSED
FUEL
CLOSED
FUEL
ERR
ERR
ERR
%
%
%
FUELING QUANTITY INDICATORS
REFUEL PANEL
Figure 4
FRA US/E ur
Feb. 2000
Refuel Station
Page: 9
Lufthansa Technical Training
FUEL
STORAGE
B737-300/400/500
28-10
28-10
STORAGE
TANKS DESCRIPTION
Purpose
Integral fuel tanks, No. 1, No. 2 and center, store fuel required to run the engines and auxiliary power unit. A surge tank, outboard of each wing tank, collects fuel overflow and includes equipment for venting the fuel tanks to overboard.
For Training Purposes Only
Location
The main tank No. 1 and main tank No. 2 are located in the interspar area of
each wing. The center tank is contained entirely within the fuselage. The surge
tanks are extensions of the main tanks.
A surge tank contains any fuel overflow from the tanks and provides the vending. A drain line allows the fuel overflow to drain back into the center tank.
A vent scoop is installed on the bottom skin of the surge tank. The vent scoop
provides a venting of the surge tank and a positve tank pressure during flight.
In case of overfuelling, the fuel will flow through the vent scoop out of the surge
tank on the ground.
In the access panels 1, 4, 6, 8 and 10 of tank No. 1 and No. 2 are drip sticks
installed for an alternate fuel quantity measuring.
Physical Description
Primary wing structure is used for the airplane fuel tanks. The tanks are located
between the front and rear spars and between the upper and lower wing skin.
Solid ”tank end” ribs closes the ends of each tank, while all other wing ribs act
as fuel baffels to reduce fuel slosh. The center tank is diveded into three cavities by spanwise beams.
All fuel tanks are fuel thight. Close metal-to-metal fit of all parts forms the basic seal. Sealing compounds and sealed fasteners are used on all joints to
complete the fluid tight seal. Two of the wing ribs contain a series of baffle
check valves to prevent fuel swapping within the tank and fuel flow away from
the boost pumps during flight.
Access panels on the wing lower surface provide access to each tank. Access
openings in the tank ribs are provided for areas wich are not directly accessibble through the access panels.
In the left air condition bay is a panel installed in order to access the center
tank.
FRA US/E ur
Oct.96
Page: 10
Lufthansa Technical Training
FUEL
STORAGE
B737-300/400/500
28-10
BOOST PUMP
ACCESS PANEL
NO. 1
NO. 2
NO. 1
1
WING CENTER
SECTION ACCESS PANEL
ACCESS
PANELS
1
NO. 3
ACCESS PANELS NO. 1 THRU 13
NO. 4
NO. 5
BOLT
NO. 6
1
NO. 7
NO. 9
NO. 8
2
NO. 11
NO. 10
NO. 13
NO. 12
3
AIR VENT SCOOP
ACCESS PANEL
(NO. 14)
For Training Purposes Only
WING
UPPER
SKIN
BOOST PUMP
ACCESS PANEL
NO. 2
UPPER WING FUEL
UPPER WING
FUEL TANK
ACCESS PANEL
TANK ACCESS PANEL
SURGE TANK
FWD
1
INBD
HIGH IMPACT
RESISTANT
ACCESS PANELS
Figure 5
FRA US/E ur
Oct.96
NOTE: PANEL NO. 1, 4, 6, 8,
____
AND 10, HAVE DRIPSTICK
INSTALLED.
TANK NO. 2 SHOWN
(TANK NO. 1 OPPOSITE)
Fuel Tanks and Access Panels
Page: 11
Lufthansa Technical Training
FUEL
STORAGE
B737-300/400/500
28-10
FUEL TANK ACCESS PANEL
Purpose
Access panels permit entry into the airplane fuel tanks for inspection or component repair.
Physical Description
The access panels in positions No. 1 and No. 2 are molded aluminium honeycomb. All other wing tank access panels are cast aluminium. The access panels are installed in the tank. The panels are installed by inserting screws
through a clamp ring on the outside, flush with wing panel and threading the
screws into captive nuts in the access panel. A molded rubber seal ring, fitted
into a grove in the panel seal face, supplies a static-type fluid seal between the
access panel and the wing skin. Fuel tank access panels are electrically
bonded to the wing structure by coating the gasket and clamp ring with anticorrosion grease.
The center tank has one access panel, wich is located in the left air condition
bay. Each surge tank has two access panels. The No.1 and No. 2 tanks have
12 access panels each. In addition, two smaller panels in each lower wing skin,
permit access to the fuel boost pumps.
For Training Purposes Only
Molded Rubber Seal
This type of seal is fixed to the access panel (old type). This seal is replaceable
on new type access panels only.
Maintenance advice:
Fuel measuring sticks are installed in the fuel tank access panels No.1, 4, 6, 8
und 10. ”Indexing Notches” are located at the inboard section of the fuel tank
access of the wing. The diameter of fuel tank access panel No.10 is about
2 inches less than the other panels.
A ”Flame Arrester Pressure Relief Valve” is installed in the access panel
No. 13. The pressure relief valve must be closed before panel reinstallation.
FRA US/E ur
July 98
Page: 12
Lufthansa Technical Training
FUEL
STORAGE
B737-300/400/500
28-10
MOLDED
RUBBER SEAL
WING LOWER SKIN
SEE A
ACCESS PANEL
PHENOLIC
RING SEAL
GASKET
MOLDED
RING SEAL
INSERT
GASKET
ACCESS
PANEL
WING LOWER
SKIN
MOUNTING
SCREW
(17 LOCATIONS)
CLAMP RING
MOUNTING
SCREW
AIR VENT SCOOP ACCESS PANEL (NO. 14)
HEX NUT
WITH FLAME ARRESTER
For Training Purposes Only
ACCESS PANEL
NUT RETAINING PLUG
GASKET IMPREGNATED WITH
ANTICORROSION GREASE
MOLDED
RUBBER
SEAL
CLAMP RING
1
1
NOT INSTALLED ON
MOLDED ALUMINUM
HONEYCOMB DOOR
WING LOWER SKIN
Figure 6
FRA US/E ur
July 98
PHENOLIC
ANTICHAFE STRIP
A
Fuel Tank Access Panel
Page: 13
B737-300/400/500
28-10
The Center Tank Access Panel
The center tank Access Panel consists of cast aluminium and is located in the
left air condition bay.
The panel is additional sealed because of the built in position (air conditioning
bay).
Installation Note: Do not use grease for screw installation. Thighten each bolt
with small turn. Then tighten a different bolt with a small turn until you have the
correct torque value for each bolt. The run-on torque is the torque necessary
to turn the bolt against the friction of the threads.
Ref. to Maintenance Manual
For Training Purposes Only
Lufthansa Technical Training
FUEL
STORAGE
FRA US/E ur
July 98
Page: 14
Lufthansa Technical Training
FUEL
STORAGE
B737-300/400/500
28-10
Left Air Conditioning Compartment
ACCESS
PANEL
CLAMP
RING
WING SKIN
CENTER TANK
ACCESS PANEL
A
B
ACCESS
PANEL
B
For Training Purposes Only
A
LOWER
CENTER
WING
PANEL
BONDING
JUMPER
FILL CAVITY AND APPLY
CONTINUOUS FILLET OF
SEALANT AROUND INNER
EDGE OF CLAMP RING
APPLY CONTINUOUS
FILLET SEAL AROUND
OUTER EDGE OF
CLAMP RING
APPLY SEALANT OVER
AND AROUND PANEL
ATTACHING BOLT
(23 PLACES)
BMS 5-26, CLASS B SEALANT APPLICATION
CLAMP
RING
WASHER
BOLT
Figure 7
FRA US/E ur
July 98
Center Tank Access Panel
Page: 15
Lufthansa Technical Training
FUEL
STORAGE
B737-300/400/500
28-10
BAFFLE CHECK VALVES
Purpose
The baffle check valves prevent fuel flow in the outboard direction but permit
fuel flow in the inboard direction. Thus the baffle check valves prevent the
boost pump inlets from being uncovered and improve airplane stability.
Location
The valves are located on the bottom of wing ribs at wing buttock line 157.0,
227.0 and 557.0.
For Training Purposes Only
Operation
The baffle check valves are free swinging and flow actuated. Inboard fuel flow
opens and outboard flow closes the valves.
FRA US/E ur
July 98
Page: 16
Lufthansa Technical Training
FUEL
STORAGE
B737-300/400/500
28-10
BAFFLE
CHECK VALVE
(5 LOCATIONS)
(WBL 157.0)
BAFFLE
CHECK VALVE
(6 LOCATIONS)
(WBL 227.0)
SURGE TANK
BODY
VALVE
For Training Purposes Only
BAFFLE
CHECK VALVE
(1 LOCATION)
(WBL 557.0)
INBD
BAFFLE CHECK VALVE
Figure 8
FRA US/E ur
July 98
Baffle Check Valves
Page: 17
Lufthansa Technical Training
FUEL
STORAGE
B737-300/400/500
28-10
TANK DRAIN VALVES
General Purpose
The sump drain valves are used for draining accumulated moisture from each
tank and for draining trapped fuel remaining after defueling.
General Location
In each tank is one drain valve at the lowest point installed.
Description Main Tank Sump Drain Valves
The sump drain valves for the No. 1 and No. 2 tank are spring-loaded closed,
poppet-type valves flush-mounted in the wing lower skin. A screen over each
valve inlet protects the unit from contaminants.
Operation
To drain the main tank fuel sump, the poppet is pushed up to open the valve
and let fuel drain through the drain hole in the center of the valve to outboard.
For Training Purposes Only
Maintenance Practices
The primary drain O-Ring of the main tank drain valve poppet, can be replaced
without draining or entering the fuel tank by placing the valve in the seal service
positon ( old valve version P/N VD82-2941 ). If it is a new valve ( P/N
87-5273 ) installed, a wrench tool is required in order to replace the O-Rings
by release the valve core plug. The removal of the valve assembly requires
draining and entering the tank.
FRA US/E ur
July 98
Page: 18
Lufthansa Technical Training
FUEL
STORAGE
B737-300/400/500
28-10
JAM NUT
SCREEN
GUIDE PIN IN
SEAL REPLACEMENT
POSITION
GUIDE PIN IN
DRAIN POSITION
PRIMARY
DRAIN
O -RING
GUIDE PIN IN
CLOSED POSITION
WING SKIN
VALVE FACE
OLD VALVE VERSION
For Training Purposes Only
WING SKIN
POPPET
PRIMARY
O -RING
OLD VALVE VERSION
NEW VALVE VERSION
VALVE
CORE
O -RING
POPPET
VALVE
CORE
PLUG
NEW VALVE VERSION
Figure 9
FRA US/E ur
July 98
Main Tank Sump Drain Valve
Page: 19
Lufthansa Technical Training
FUEL
STORAGE
B737-300/400/500
28-10
Description Surge Tank Sump Drain Valves
The sump drain valves for the surge tanks are spring-loaded close, poppettype valves flush-mounted in the wing lower skin. A screen over each valve
inlet protects the unit from contaminants.
Operation
To drain a surge tank fuel sump, the poppet is pushed to open the valve and let
fuel drain through the drain hole in the center of the valve to outboard.
For Training Purposes Only
Maintenance Practices
The valve has a flapper valve, therefore the poppet valve assembly is removeable without draining the fuel tank, by using a wrench tool. The valve poppet is
unscrewed from its housing and installed in a thread sleeve of the lower wing
skin ( be careful during change ).
FRA US/E ur
July 98
Page: 20
Lufthansa Technical Training
FUEL
STORAGE
B737-300/400/500
28-10
FLAPPER
VALVE
SCREEN
SPRING
SURGE TANK
FUEL SUMP
DRAIN VALVE
SHRINK-FIT
BUSHING
SURGE TANK
FUEL SUMP
DRAIN VALVE
HINGE PIN
POPPET VALVE
WING
LOWER
SKIN
DRAIN
VALVE
TOOL
For Training Purposes Only
5/8 SOCKET
Figure 10
FRA US/E ur
July 98
USE T-HANDLE
FOR REMOVAL AND
TORQUE WRENCH
FOR INSTALLATION
Surge Tank Sump Drain Valve
Page: 21
Lufthansa Technical Training
FUEL
STORAGE
B737-300/400/500
28-10
CENTER TANK DRAIN VALVES
Purpose
The center tank train valve is used for draining the accumulated moisture and
trapped fuel remaining after defueling.
Location
The center tank drain valve is installed in the wing lower skin in the center
section. The access door is located between the air conditioning bays in front
of the marker beacon antenna.
Description
The center tank sump drain valve is a spring-loaded closed, flapper-type
check valve. A sump drain assembly connects the valve upper housing with the
lower body section of the airplane through the keel beam area.
Maintenance Practices/Sump Drain Valve (Rod-Actuated)
- Sump drain valve change
S The valve can be removed without defueling the center tank, because
of a flapper assembly. It closes the valve opening in the tank, when
the drain valve has been removed.
S The removal and installation procedure is similar as the
tool-operated one.
For Training Purposes Only
Operation
The sump is drained as follows:
- If the sump drain valve does not have an actuating rod (Tool-Operated)
S To drain, insert a broad-bladed screwdriver in slot, turn clockwise and
push up on the plunger.
S To close, release the plunger, let the slot align fore and aft, and close
access door.
- If the sump drain valve has an actuating rod (Rod-Actuated)
S To drain, pull on the actuating rod.
S To close, release the rod and close the access door.
Maintenance Practies/Sump Drain Valve (Tool-Operated)
- Sump drain valve change
S The center tank must be defueled for drain valve removal.
S Access to the assembly is through lightening holes in the keel beam.
S The bonding jumper must be disconnected from the airplane structure.
S The retaining plate must be removed.
S The drain assembly can be turned clockwise until it moves freely from
the upper housing.
- Installation in a vice versa sequence
FRA US/E ur
July 98
Page: 22
Lufthansa Technical Training
FUEL
STORAGE
B737-300/400/500
28-10
SUMP DRAIN
VALVE
ATTACHING
SUMP
DRAIN
VALVE
FLAPPER
ASSEMBLY
LOWER WING
SKIN PANEL
PLUNGER
O-RING
UPPER
HOUSING
O-RING
UPPER
HOUSING
CENTER WING
CAVITY NO. 2
BOLTS
LOCKING
DETENT
EARS
LOCKPIN
VALVE
ACTUATING
CAM
SUMP DRAIN
ASSEMBLY
PLUNGER
DRAIN TUBE
ASSEMBLY
DRAIN TUBE
HOSE
SUMP
DRAIN
ASSEMBLY
SUMP
DRAIN
ASSEMBLY
CLAMP
ACTUATING
ROD
ACTUATING ROD
BONDING JUMPER
(TO STRUCTURE)
ACCESS DOOR
HOSE
RETAINING
PLATE
LOWER
HOUSING
For Training Purposes Only
SUMP DRAIN
PULL TO DRAIN.
RELEASE TO CLOSE.
VERIFY THAT HANDLE
RETURNS TO CLOSED
POSITION.
LOWER BODY
SKIN
DRAIN
TUBE
DOOR
ACCESS
FASTENER DOOR
(ROD ACTUATED SUMP DRAIN ASSEMBLY)
Figure 11
FRA US/E ur
July 98
TURN & PUSH TO DRAIN
RELEASE TO CLOSE
SLOT POSITION TO BEFORE
& AFT FOR CLOSED & LOCKED
RETAINING
PLATE
DRAIN
WELL
ACCESS
DOOR
SUMP DRAIN
LOWER
BODY SKIN
(TOOL ACTUATED SUMP DRAIN ASSEMBLY)
(770328)
Center Tank Sump Drain Assembly and Valve
Page: 23
Lufthansa Technical Training
FUEL
STORAGE
B737-300/400/500
28-10
APU SHROUD DRAIN
Purpose
A shroud drain is provided to drain moisture or any fuel leaking from the APU
fuel line.
Location
The drain line is located in the left main wheel well.
Description
The shroud drain consists of a drain line connected to a drain manifold. The
drain manifold contains a flame arrestor and a drain cock. The line terminates
in a drain mast.
For Training Purposes Only
Operation
During operation, only moistere drains from the mast. If the APU fuel line is
leaking, fuel drains from the drain mast.
The drain cock is used to check for and drain off any leaking fuel while on the
ground. The drain cock must be closed for flight.
Note: It is optional to have the hydraulic resevoir vent line connected to the
drain mast on new B737 airplanes (see ATA 29 Hydraulic).
FRA US/E ur
July 98
Page: 24
B737-300/400/500
28-10
For Training Purposes Only
Lufthansa Technical Training
FUEL
STORAGE
Figure 12
FRA US/E ur
July 98
APU Fuel Line Shroud Drain
Page: 25
Lufthansa Technical Training
FUEL
FUEL VENT SYSTEM
28-20
28-20
FUEL VENT SYSTEM
TANK VENT SYSTEM
Purpose
The fuel vent system prevents damage to the tank structure by providing positive venting of all fuel tanks, regardless of airplane attitude. During flight, the
system also helps to decrease fuel evaporation and assists the fuel boost
pumps-by providing a small positive pressure head on the fuel.
Location
The components associated with the tank vent system are located inside the
fuel tanks. Vent scoops are located on the bottom skin of surge tanks.
For Training Purposes Only
B737-300/400/500
Physical Description
Two parallel vent channels extend into the main and center tanks from the
surge tanks. Two stringers attached to the wing upper skin form each hat section channel. The channels open into each surge tank. The aft channel terminates near the wing root in the wing tanks and is connected to a vent tube. The
forward channel passes through the center tank and forms a continuous channel connecting the left and right surge tanks. The center tank is vented by tubings and is connected to the forward channel.
A tube is mounted to the channel in tanks No. l and 2. In the center tank, tubing
is mounted to the channel at two places. Two drain check valves are installed
in the center tank vent tubing, to drain the tubing/channel/surge tanks.
A surge tank, located at the end of each wing, collects any overflow fuel passing through the vent channels. The overflow fuel flows through a surge tank
drain line into the center tank.
Tank No. l and 2 float valves are located in the channel of the wing tanks. The
center tank float valve is in the vent tubing.
FRA US/E ur
Oct.96
Physical Description (continued)
A fuel float valve opens and closes corresponding to the fuel level in the tanks
and airplane attitude changes. As the fuel level rises the valves begin to close.
As the fuel level lowers, the valve begins to open. A float stop supports the
float in its full open position.
The fuel vent scoop consists of a recessed ram air scoop mounted in a lower
wing surface access panel, and a five-inch standpipe assembly. A screen is
installed at the top of the standpipe to prevent the entrance of foreign matter.
The design of the scoop is such that icing conditions have minimum effect on
ram air pressure.
All fuel tanks are fuel tight. Close metal-to-metal fit of all parts forms the basic
seal. Sealing compounds and sealed fasteners are used on all joints to complete the fluid tight seal. Two of the wing ribs contain a series of baffle check
valves to prevent fuel flow away from the boost pumps.
Access
Access to the vent components in the tanks is through the fuel tank access
panel.
Operation
During fueling of the tanks, if the fueling system fails to close the fueling valve,
excess fuel enters the climb port. (Float valve is closed.) Through the vent
channel, the fuel flows to the surge tank and overflow through the vent scoop.
Fuel trapped in the surge tank (maximum 114 Liters, 30 US gallons) flows to
center tank, after initial burn off, through the vent system.
During climb, the climb port is exposed, float valve is closed, allowing air/vapor
to be vented through the vent scoop.
During cruise, air enters the tank through the normal port (float valve is open)
providing slight pressurization.
During descent, air enters the tank through the normal port since float valve is
open and climb port submerged in fuel.
Page: 26
Lufthansa Technical Training
FUEL
FUEL VENT SYSTEM
B737-300/400/500
28-20
RELIEVES TRAPPED
AIR DURING FUELING
VENT DUCT
(UPPER WING
STRINGER)
HINGE
VALVE STOP
CHECK
VALVE
FLOAT
FLOAT VALVE
(NORMAL VENT)
(TYP 2 PLS)
CHECK
VALVES
(TYP 2 PLACES)
UPPER SURFACE
(SEALED)
STRINGER 11
VALVE STOP
VENT
LINE
CLIMB
VENTS
FWD
FLOAT
DRAIN
SURGE TANK
GRAVITY
DRAIN LINE
VENT
SCOOP
CHECK
VALVE
HOLE
INBD
OVERBOARD
VENT & RAM
PRESSUREINLET
(LWR SURF)
O-RING
CROSSOVER
TUBE
FLOAT VALVE
(NORMAL VENTS)
DEFLECTOR
For Training Purposes Only
CENTER TANK
TANK 1
UPPER SURFACE
(SEALED)
STRINGER 9
TANK 2
SURGE TANK
SURGE TANK
CHECK
VALVE
Figure 13
FRA US/E ur
Oct.96
Fuel Vent System
Page: 27
Lufthansa Technical Training
FUEL
FUEL VENT SYSTEM
B737-300/400/500
28-20
VENT SCOOP AND FLAME ARRESTER
Fuel Vent Scoop
The fuel vent scoops, located in the outboard half of the vent surge tanks, are
the overboard vents for the vent system. Each scoop consists of a recessed
ram air scoop mounted in a lower wing surface access panel and a five inch
standpipe assembly.
The diverging walls of the standpipe act as a plenum chamber ensuring that
ram air will be applied to the vent system during all flight attitudes of the airplane.
A stainless steel, cellular-core flame arrester is installed at the top of the
standpipe to suppress flame transmission into the tanks and vent system from
an external ignition source. The flame arrester also serves as a debris screen
which may be subject to airflow restriction caused by debris or severe icing
conditions.
A surge tank flame arrester pressure relief valve is used to provide the necessary venting when airflow through the flame arrester is restricted.
FLAME ARRESTER PRESSURE RELIEF VALVE
Surge Tank Flame Arrester Pressure Relief Valve
A positive and negative pressure relief valve is used to bypass the fuel vent
scoop for fuel system venting if the surge tank flame arrester core cells are
plugged such as from severe icing conditions. The relief valve is installed on
the access panel for the inboard half of the surge tank.
A spring-loaded poppet, on the relief valve, with outer surface flush with the
wing lower skin is triggered open through a latching mechanism by a pressure
or vacuum force acting on a diaphragm.
The upper chamber of the diaphragm is vented to the atmosphere through
three ambient air holes in the lower outer surface of the valve while the lower
chamber is vented to the interior of the surge tank.
When the poppet opens, it is raised about 1 inch above the wing lower skin
surface which causes a manual reset knob and stem to protrude about the
same distance downward out of the center of the poppet.
Once actuated open, the poppet must be manually reset to the closed position
at the conclusion of the flight. Manual reset is accomplished by pulling reset
knob downward until the poppet is relatched in the closed position. The relief
valve is designed to open at 2.0 to 2.7 psi increasing positive pressure and -4
to -10 inches of water increasing negative pressure or vacuum.
For Training Purposes Only
Maintenance advice:
If the flame arrester pressure relief valve was found open, you must check the
flame arrester for condition (clogging).
FRA US/E ur
Oct.96
Page: 28
Lufthansa Technical Training
FUEL
FUEL VENT SYSTEM
B737-300/400/500
28-20
MANUAL
RESET
KNOB
WING BOTTOM SKIN
PHENOLIC
RING SEAL
GASKET
SURGE TANK ACCESS
PANEL (NO. 13)
PRESSURE
RELIEF VALVE
MOLDED
RING SEAL
INSERT
ACCESS
PANEL
VALVE POPPET
(RAISED-OPEN- POSITION)
WING LOWER SKIN
MOUNTING
SCREW
(17 LOCATIONS)
VALVE OPEN POSITION
MANUAL
RESET
KNOB
FLAME ARRESTER
FILLET SEALANT
(BMS 5-26, TYPE II)
AIR VENT STACK
BOLT AND
SEAL WASHER
(8 LOCATIONS)
For Training Purposes Only
SURGE TANK ACCESS
PANEL (NO. 13)
PRESSURE
RELIEF VALVE
VALVE POPPET
(FLUSH WITH OUTER
SURFACE-CLOSED
POSITION)
WING LOWER SKIN
VALVE CLOSED POSITION
AIR VENT SCOOP ACCESS PANEL (NO. 14)
ACCESS PANEL (NO. 13)
WITH FLAME ARRESTER
WITH FLAME ARRESTER PRESSURE RELIEF VALVE
Figure 14
FRA US/E ur
Oct.96
Vent Scoop / Flame Arrester Pressure Relief Valve
Page: 29
Lufthansa Technical Training
FUEL
PRESSURE FUELING SYSTEM
B737-300/400/500
28-30
28-30
PRESSURE FUELING SYSTEM
PRESSURE FUELING STATION
Purpose
The pressure fueling panel is used for filling the tanks, defueling the tanks or
fuel transfer between the tanks.
Location
The pressure fueling panel (P15) is located in the fueling station.
Physical Description
The fueling panel consists of 3 fuel quantity indicators, 3 fueling valve switches,
3 blue valve position lights, switch for indicator test or for auxiliary fueling
power control.
Access
Access to the fueling panel is by opening the fueling station door.
Power
The power required for the fueling operation is 28 volt dc and 115 volt ac obtained from ground power, APU or battery.
For Training Purposes Only
Control
When the fueling station door is opened, the fueling power switch is actuated
and the panel is illuminated by 3 white lights. (If the fueling power switch fails to
operate, power to the panel can be supplied by holding the auxiliary fueling
power control switch.)
Operation
Prior to the fueling operation, the 3 blue lights and quantity indicators are
checked for proper operation. Using the fueling valve switches in the open
position, allows the fueling valve to open, blue lights illuminate, and fuel proceeds to the respective tank. Fueling can be stopped by placing the valve
switch to the closed position, or fueling stops automatically by a float switch
when the tank is full. Upon completion of fueling, closing of the door removes
power from the fueling station.
FRA US/E ur
Oct.96
Page: 30
Lufthansa Technical Training
FUEL
PRESSURE FUELING SYSTEM
B737-300/400/500
28-30
REFUEL STATION
VALVE
TEST
GAGES &
POSITION
b
b
GROUND REFUELING
RELAYS R10 / R11 IM E 3-3
LIGHTS
b
FUELING
TANK No.2
TEST
GAGES
CENTER TANK
TANK No.1
OPEN
OPEN
OPEN
CLOSED
CLOSED
CLOSED
FUELING
POWER
SWITCH
FUELING
RECEPTACLE
OFF
AUX FUELING
POWER CONTROL
FUEL
FUEL
REFUEL PANEL
(P15 PANEL)
FUEL
ERR
ERR
ERR
%
%
%
WING
LEADING
EDGE
For Training Purposes Only
ACCESS
DOOR
FWD
PANEL
LIGHTS
REFUEL STATION
Figure 15
FRA US/E ur
Oct.96
Pressure Fueling Station
Page: 31
Lufthansa Technical Training
FUEL
PRESSURE FUELING SYSTEM
B737-300/400/500
28-30
FUELING OPERATION
Purpose
The fueling system provides a means of filling the fuel tanks on the airplane.
System Description
Fueling can be accomplished by the use of a single pressure fueling station
through which all tanks can be filled partially or completely. Alternately, the
main tanks can be filled through the overwing ports. The center tank can be
filled by transferring fuel from the main tanks using the fueling station.
General Component Location
The components associated with the fueling system are the fueling station located under the right wing leading edge outboard of the engine, 3 float
switches one inside each fuel tank and 2 overwing ports on top of each main
tank.
Backup Operation
The main fuel tanks can be filled through the overwing ports.
The center tank can be filled by transferring fuel from the main tanks.
For Training Purposes Only
General Operation
All tanks can be filled from the fueling station. The tanks can be filled to any
desired quantity by using the control panel. The float switches sense full tank
condition and automatically stop the fueling. Power requirements are supplied
by ground power, APU or the battery. Pressure fueling can also be done manually. Maximum fuel pressure is 55 psi.
Operation
With the fueling hose connected to the fueling manifold and the three fueling
valves open, fuel is supplied to the three tanks.
Supply to the main tank No. 1 passes through main tank No. 2 and center tank.
Supply to the center tank passes through main tank No. 2 and a check valve.
Upstream of the check valve are vent lines from the two center tank pumps.
These lines ensure automatic repriming of the pumps during fueling.
Supply to the main tank No. 2 is through a restrictor to ensure same fueling
rate as for main tank No. 1.
During the fueling operation, if the fueling valves fail to close, the excess fuel
enters the vent system and proceeds overboard through the vent surge tanks
and the vent scoop.
FRA US/E ur
Oct.96
Page: 32
Lufthansa Technical Training
FUEL
PRESSURE FUELING SYSTEM
B737-300/400/500
28-30
TO THE FUELING FLOAT
SWITCH FOR THE NO. 1 TANK
ELECTRICAL
CONNECTION
(EXAMPLE)
CENTER TANK
BOOST PUMPS
PRIME LINE
FUELING
FLOAT
SWITCH
CENTER TANK
DEFUELING VALVE
(REF 28-23-00)
FUELING RECEPTACLE
CENTER
TANK
SUPPLY
FUELING MANIFOLD
FUELING SHUTOFF
VALVES (3)
For Training Purposes Only
CENTER TANK
NO. 2 TANK
Figure 16
FRA US/E ur
Oct.96
FUELING
FLOAT SWITCH
TANK NO.2
Pressure Fueling System
Page: 33
Lufthansa Technical Training
FUEL
PRESSURE FUELING SYSTEM
B737-300/400/500
28-30
FUELING MANIFOLD
Purpose
The fueling manifold is used as a distribution center for the pressure fueling,
defueling and fuel transfer.
Location
The fueling manifold is located on the right wing front spar in the fueling station.
Physical Description
The manifold consists of a fueling receptacle with a poppet valve, three solenoid-controlled fuel pressure operated valves with manual overrides, and four
outlet ports, three of which contain check valves.
Maintenance Practices
The fueling manifold and its components can be removed and replaced without
defueling the tanks. Removal of the manifold requires evacuating fuel from the
manifold by depressing the poppet valve in the receptacle, disconnecting electrical connectors to the fueling valves, removing the fueling valves and bolts
between the manifold and check valves. Removal and replacement of the fueling check valves requires removal of the manifold. The fueling hose adapter
can be removed and replaced without removing the manifold.
For Training Purposes Only
Access
The access to the manifold is by opening the fueling station door.
Operation
With the fueling hose connected, a plunger in the hose nozzle opens the poppet valve allowing the fuel to enter the fueling manifold. Fuel through the orifice
enters the chamber above the diaphragm, thus equalizing the pressure across
the diaphragm and the spring keeps the valve closed. When the solenoid is
energized or the manual override plunger pushed and held, fuel pressure
above the diaphragm is relieved and fueling valve opens. Fuel from the manifold proceeds to the respective tank through the check valve.
When the solenoid is de-energized or the manual override is released, pressure is equalized across the diaphragm and the fueling valve closes.
During defueling operation, with the defueling valve open, fuel enters the fueling manifold and is taken out by a hose through the fueling receptacle.
During transfer operation, with the defueling valve open and the tank to be filled
fueling valve open, fuel proceeds from-the fueling manifold to the tank.
FRA US/E ur
Oct.96
Page: 34
Lufthansa Technical Training
FUEL
PRESSURE FUELING SYSTEM
B737-300/400/500
28-30
FUELING STATION
FUELING BODY
ELBOW ASSEMBLY
ELECTRICAL
PLUG
FRONT
SPAR
MOUNTING BOLT
(9 LOCATIONS)
0-RING
ELBOW
For Training Purposes Only
FUELING
SHUTOFF
VALVE
BOLT FOR
THE FUELING
SHUTOFF
VALVE
FWD
INBD
WASHER
0-RING
CHECK VALVES
FUELING
RECEPTACLE
MANIFOLD
SUPPORT
BOLT
FUELING RECEPTACLE MANIFOLD
Figure 17
FRA US/E ur
Oct.96
Fueling Manifold
Page: 35
Lufthansa Technical Training
FUEL
PRESSURE FUELING SYSTEM
B737-300/400/500
28-30
FUELING CIRCUIT
Operation
If the battery switch is ON, battery provides power to relay R11. If ground
power is used, the Bus Protection Panel TR unit provides power for relay R11.
When the ‘fueling bay door is open, the fueling power switch (or holding the
auxiliary fueling power control switch) provides a ground for relay R11. This will
provide 28 volts dc for fueling bay illumination, press-to-test of valve position
lights and valve position switches.
Placing the valve position switch to OPEN energizes the valve solenoid through
the closed float switch; the blue light is illuminated when solenoid is energized.
When the tank is full, the float switch opens, de-energizing the solenoid, valve
closes and blue light is extinguished.
Fueling can be stopped at any time by placing the valve position switch to
CLOSE.
For Training Purposes Only
Backup Operation
If dc power is not available, the fueling valve can be opened by the manual
override button next to the solenoid.
FRA US/E ur
Feb. 2000
Page: 36
Lufthansa Technical Training
FUEL
PRESSURE FUELING SYSTEM
B737-300/400/500
28-30
FULL
28V DC
SW.
HOT BAT
C32
BUS
FUELING AND
EXT PWR CONT
(P6-5)
NOT FULL
S578 NO. 2 TANK
FUELING FLOAT SWITCH
W
L281 INBD FUELING
NOZZLE FLOODLIGHT
EXT PWR
TR
G7 PWR BUS
PROTECTION
PANEL
R11 REFUELING PWR
CONTROL RLY (E3-3)
P6 LOAD CONTROL CENTER-RIGHT
V45 NO. 2 TANK
FUELING SHUTOFF
VALVE
W
L280 OUTBD FUELING
NOZZLE FLOODLIGHT
CLOSED
V46 CENTER TANK
FUELING SHUTOFF
VALVE
W
L279 FUELING
PANEL FLOODLIGHT
OPEN
S156 FUELING
PWR CONT
L284
V44 NO. 1 TANK
FUELING SHUTOFF
VALVE
B
POWER
CONTROL
FULL
L283
B
TEST
GAGES
L282
For Training Purposes Only
S160 FUEL
INDICATOR
TEST SWITCH
NOT FULL
S576 CENTER TANK
FUEL FLOAT SWITCH
B
OPEN
S158 TANK 2
FUELING VALVE
CONTROL
CLOSED
OPEN
S159 CTR
TANK FUEL
VALVE CONTROL
CLOSED
FULL
P15 REFUEL PANEL
S157 TANK 1
FUELING VALVE
CONTROL
Feb. 2000
CLOSED
NOT FULL
S574 NO. 1 TANK
FUELING FLOAT SWITCH
Figure 18
FRA US/E ur
OPEN
Pressure Fueling Electrical Schematic
Page: 37
Lufthansa Technical Training
FUEL
PRESSURE FUELING SYSTEM
B737-300/400/500
28-30
FLOAT SWITCH
Purpose
The float switches, one for each tank, prevent the tanks from being overfilled.
Location
The switches are located near the top of each tank and sense full tank quantity.
Physical Description
The switch consists of a capsule surrounded by a cork float containing a magnet; the whole assembly is in a cylindrical container.
Access
Access to the switches is through a fuel tank access panel.
Power
Power supply is 28 volt dc from the fueling station.
For Training Purposes Only
Operation
During pressure fueling with the tank less than full, the float switch allows
power to the fueling valve which will then open with fuel pressure. When the
tank is full, the float switch interrupts power to the fueling valve causing it to
close.
FRA US/E ur
Oct.96
Page: 38
Lufthansa Technical Training
FUEL
PRESSURE FUELING SYSTEM
B737-300/400/500
28-30
SPANWISE
BEAM NO. 2
TANK
CAVITY
N0. 2
ELECTRICAL
CONDUIT
FWD
FUELING
FLOAT SWITCH
CENTER TANK
FUELING
FLOAT SWITCH
MOUNTING
BRACKET
ACCESS
OPENING
SEE B
SPANWISE
BEAM NO. 1
479
WING RIB
FUELING
FLOAT SWITCH
B
NO. 2 TANK FUELING
FLOAT SWITCH
(NO. 1 TANK OPPOSITE)
SEE A
MOUNTING
BRACKET
BONDING
JUMPER
CONDUIT
UNION
CONDUIT NUT
For Training Purposes Only
ACCESS PANEL
NO. 11
ELECTRICAL
CONDUIT
WIRE BUNDLE
WIRE SPLICE
A
WING FRONT
SPAR
Figure 19
FRA US/E ur
Oct.96
Fuel Tank Float Switches
Page: 39
Lufthansa Technical Training
FUEL
PRESSURE FUELING SYSTEM
B737-300/400/500
28-30
OVERWING FUELING PORT
Purpose
The fuel tanks No. 1 and No. 2 can be filled by gravity through the overwing
fueling ports.
Location
The ports are located in the top of the wing towards the wing.
Physical Description
Each assembly consists of a flush fitting cap with a locking mechanism and a
retainer lanyard. The filler cap is opened by rotating the cap counterclockwise.
For Training Purposes Only
Operation
When the filler cap is opened, the main tank can be filled by gravity. The quantity of fuel that can be put into the tank through the overwing port. The fuel
quantity is considerably less than by pressure fueling, because of port location.
CAUTION: Do not open overwing filler cap when the tank has been full refueled
by pressure fueling. More than 400 KG fuel spills out over the wing.
FRA US/E ur
Oct.96
Page: 40
Lufthansa Technical Training
FUEL
PRESSURE FUELING SYSTEM
B737-300/400/500
28-30
OVERWING
FILL PORT
FILLER CAP
HANDLE
OVERWING FILL PORT
LANYARD
For Training Purposes Only
ADAPTER
O-RINGS
RETAINING NUT
SEAL RING
OVERWING FILL PORT
Figure 20
FRA US/E ur
Oct.96
Overwing Fueling Ports
Page: 41
Lufthansa Technical Training
FUEL
DISTRIBUTION
B737-300/400/500
28-40
28-40
FUEL FEED SYSTEM
ENGINE FUEL FEED SYSTEM
Purpose
The distribution system allows fuel to be supplied to the engines and APU. In
addition, the system can be used for defueling the tanks and for fuel transfer
between the tanks.
System Description
The distribution system utilizes pumps, valves and tubing for engine and APU
feed. The fueling station is used for defueling and transfer operations which are
only possible on the ground.
For Training Purposes Only
General Component Location
The fuel distribution components are located inside the main tanks and on the
front and rear spars of the main tanks.
General Operation
A. Engine Feed
- Fuel is first supplied to both engines from the center tank and then from
the respective tanks to engines. The crossfeed valve allows fuel from
one tank to be supplied to both engines. Fuel can also be supplied from
main tanks by suction to both engines.
B. APU Feed
- Fuel to the APU is primarily supplied from tank No. 1, but it can be supplied from any tank using the engine feed components.
C. Defueling
- All tanks can be defueled through the fueling manifold using engine feed
components.
D. Transfer
- Fuel can be transferred between the tanks using engine feed components and the fueling manifold.
FRA US/E ur
Oct.96
Engine Feed
With six pumps operating, the center tank pumps override the main tank
pumps and supply fuel to the engines. This is accomplished by the opening
pressure difference across the check valves at the outlet of the center tank
pumps being less than the opening pressure difference across the check
valves at the outlet of the main tank pumps.
When the center tank fuel is depleted, or the center tank boost pumps are off
the main tank boost pumps supply fuel to the engines. Fuel feed from one side
to the opposite engine is accomplished by opening the crossfeed valve. With
the boost pumps not operating, fuel is supplied to the engines only from the
main tanks through the boost pump bypass valves. Fuel head, vent ram inflight, and engine driven fuel pump suction provide the necessary flow. There is
no bypass valve for the center tank.
APU Feed
Fuel for the APU is normally supplied from No. 1 tank. During APU start, fuel is
supplied by a suction supply line or an optional APU boost pump. Fuel head
pressure and vent ram assist fuel feed in flight. Fuel from a main boost pump
can also be supplied to the APU via the Crossfeed Manifold. The APU fuel
shutoff valve information is in the APU section.
Page: 42
B737-300/400/500
28-40
For Training Purposes Only
Lufthansa Technical Training
FUEL
DISTRIBUTION
Figure 21
FRA US/E ur
Oct.96
Basic Schematic - Engine Fuel Feed System
Page: 43
Lufthansa Technical Training
FUEL
DISTRIBUTION
B737-300/400/500
28-40
ENGINE FUEL FEED SYSTEM
Fuel Transfer
Fuel can be transferred between the tanks on the ground only, because the
fueling system is utilized for this operation. In all cases of fuel transfer the defueling valve must be open (in some cases, the crossfeed valve must be open
also). For example, transfer of fuel from No. 1 to No. 2 tank involves:
- Boost pumps in No. 1 tank operating
- Crossfeed valve open
- Defueling valve open
- No. 2 tank fueling valve open
Fuel from No. 1 tank is pumped by the boost pumps, via the crossfeed manifold, to No. 2 tank. Similar operations are required for other tank-to-tank
transfer.
For Training Purposes Only
Defueling
In all cases of defueling, the defueling valve must be open (in some cases, the
crossfeed valve must be open also). A fuel hose is attached to the fueling receptacle. For example, defueling No. 1 tank (using pumps) involves:
- Boost pumps in No. 1 tank operating.
- Crossfeed valve open.
- Defueling valve open.
Fuel from No. 1 tank flows through the pumps, manifold, valves and fueling
hose to storage. Similar operations are required for defueling the other tanks.
Suction defueling can be used, but it is not selective.
FRA US/E ur
Jan.2000
Page: 44
B737-300/400/500
28-40
For Training Purposes Only
Lufthansa Technical Training
FUEL
DISTRIBUTION
Figure 22
FRA US/E ur
Jan.2000
Fuel Feed System
Page: 45
Lufthansa Technical Training
FUEL
FUEL FEED SYSTEM
28-40
FUEL BOOST PUMPS
Main and Center Tank Boost Pumps
Purpose
The six fuel boost pumps, two per tank, deliver fuel under pressure from various tanks to the two engines. The pumps are also used for defueling the tanks
and for fuel transfer between the tanks. The center tank scavenge system utilizes forward left pump discharge flow for jet pump operation.
The main tank water scavenge system utilizes forward main tank pumps discharge flow for jet pump operation.
Location
The main tank forward pumps are installed on the front spars. The main tank
aft and center tank pumps are located in dry bays in the main tanks.
Physical Description
The boost pump consists of a three-phase motor-driven centrifugal impeller,
inlet port with pump removal valve and handle, drain cock, vent port, discharge
port with connection to a pressure switch and a check valve. The pump is held
in position by two clamps. On the forward pumps, part of the discharge flow is
directed to jet pumps.
NOTE:
For Training Purposes Only
B737-300/400/500
MAIN TANK AND CENTER TANK PUMPS ARE IDENTICAL PUMP
OUTLET CHECK VALVES ARE DIFFERENT FOR PUMPS IN MAIN
AND CENTER TANK. (VALVES ARE INDEXED ON MANIFOLD
SIDE TO PREVENT MISMATCHING.)
Access
The forward boost pumps are accessible by extending the leading edge flaps.
The aft and center pumps are accessible through panels on the bottom wing
skin.
Power
The pump use 115 volt ac, 3Ø, 400 Hz power. With the motor operating, fuel
enters the pump and is delivered to the manifold through the check valve. Upstream of the check valve, the pump performance is monitored by a pressure
switch. Part of the incoming fuel flow (approximately 2 gallons per minute) is
used for cooling and lubricating the pump and is discharged into the tank
through the vent connection. The pump removal and drain valves are used durFRA US/E ur
Oct.96
ing the replacement of the pump. When the removal valve handle is in the
closed position it will interfere with the access panel preventing its reinstallation.
The jet pump for the center tank fuel scavenge takes residual fuel from the
center tank and delivers it to tank No: 1.
The jet pumps for the main tank water scavenge take fuel/water mixture from
the low points in the main tanks and deliver it to the main tank pump inlets.
Maintenance Practices
Removal and installation of all pumps is the same and can be performed without defueling the tanks. The pump removal valve is closed, fuel drained from
the pump and two lower mounting bolts on the clamp are removed. The clamp
can be swung out and pump removed. Prior to installation of the pump, approximately 1/2 pint of fuel is poured into the pump for repriming.
The jet pump nozzle can be removed without defueling the tank.
CAUTION:
WHEN REMOVING A CENTER TANK BOOST PUMP, ALSO
CLOSE THE REMOVAL VALVE FOR OPPOSITE THE CENTER TANK BOOST PUMP TO PREVENT FUEL FLOWING
BACK THROUGH THE REPRIME LINE.
APU DC Boost Pump
The APU DC boost pump supplies fuel under pressure from tank No. 1 to the
APU fuel feed line as necessary for cold starting or after air has entered the
fuel feed line.
The boost pump is mounted on the left lower inboard trailing edge panel and
pumps fuel through tube lines wich penetrade the left wing rear spar. The pump
operates on 28-Volt DC Power and will run for approximately 1 minute during
APU starting.
Page: 46
Lufthansa Technical Training
FUEL
FUEL FEED SYSTEM
B737-300/400/500
28-40
FUEL BOOST
PUMP
B
SEE
FUEL BOOST
PUMP
SEE
A
FUEL BOOST
PUMP
SEE
ELECTRICAL
CONNECTOR
A
ENGINE FUEL
SHUTOFF VALVE
ENGINE FUEL
SHUTOFF VALVE
BONDING
JUMPER
APU DC
BOOST PUMP
OUTLET
APU FUEL
SHUTOFF
VALVE
APU DC
BOOST
PUMP
SEE
FUEL
CROSSFEED
VALVE
C
INLET
LEFT LOWER
INBOARD TRAILING
EDGE PANEL
WING LOWER
SURFACE
BOOST PUMP
HOUSING
C
SHOLDER
BOLT
SHOULDER
BOLT
MOUNTING
CLAMP
ACCESS
OPENING
For Training Purposes Only
MOUNTING
CLAMP
INBD
LOWER
MOUNTING
BOLT
FUEL BOOST
PUMP
(TYPICAL)
FUEL BOOST
PUMP
(TYPICAL)
FWD
DRAIN
VALVE
PUMP REMOVAL
VALVE HANDLE
FWD
Oct.96
PUMP REMOVAL
VALVE HANDLE
INBD
DRAIN
VALVE
A
Figure 23
FRA US/E ur
WING
FRONT
SPAR
WARNING FLAG
CLEARANCE PANEL
B
Fuel Boost Pumps
Page: 47
Lufthansa Technical Training
FUEL
FUEL FEED SYSTEM
B737-300/400/500
28-40
MAIN AND CENTER TANK BOOST PUMP POWER CONTROL
Purpose
The boost pump power sources are arranged to ensure that in the event of a
single generator failure, at least one pump in each tank will remain powered.
Location
The circuit breakers and relays are located in the P6 panel. The boost pump
switches are located on the P5-2 panel.
Power
The power required is 28 Volt DC for the relay and 115 Volt AC for the pump.
For Training Purposes Only
Operation
Placing the pump switch to the ON position energizes the boost pump relay
which in turn connects 115 Volt AC to the pump.
The main tank aft pumps are powered from the transfer busses so that at low
fuel level, if a generator is lost, both aft pumps remain powered. The remaining
pumps are powered from main busses.
FRA US/E ur
Feb. 2000
Page: 48
Lufthansa Technical Training
FUEL
FUEL FEED SYSTEM
B737-300/400/500
28-40
TO OTHER TANKS
BOOST PUMP SWITCH
SHOLDER
BOLT
WING
FRONT
SPAR
MOUNTING
CLAMP
115V AC
LOWER
MOUNTING
BOLT
BOOST PUMP
28V DC
FUEL BOOST
PUMP
(TYPICAL)
RELAY
BOOST PUMP SWITCH
FWD
TYPICAL CIRCUIT FOR ONE BOOST PUMP IN A GIVEN TANK.
OTHER BOOST PUMP CIRCUIT SAME BUT WITH SEPARATE SOURCE
OF POWER AS SHOWN IN TABLE BELOW
PUMP REMOVAL
VALVE HANDLE
INBD
DRAIN
VALVE
WARNING FLAG
CLEARANCE PANEL
BOOST PUMP POWER SOURCE
115V AC BUS NO.
28V DC BUS NO.
FUEL
For Training Purposes Only
TANK
1
2
1
AFT
PUMP
(R18)
FWD
PUMP
(R19)
2
FWD
PUMP
(R21)
AFT
PUMP
(R20)
LEFT
PUMP
(R54)
RIGHT
PUMP
(R55)
CENTER
Figure 24
FRA US/E ur
Feb. 2000
TRANSFER
BUS NO. 1
AFT
PUMP
1
2
TRANSFER
BUS NO. 2
FWD
PUMP
FWD
PUMP
RIGHT
PUMP
AFT
PUMP
LEFT
PUMP
Main and Center Tank Fuel Boost Pump Power Control
Page: 49
Lufthansa Technical Training
FUEL
FUEL FEED SYSTEM
B737-300/400/500
28-40
BOOST PUMP CHECK VALVES
Purpose
The fuel boost pump check valve closes the boost pump outlet line when the
pressure drops below a predetermined amount, thus preventing reverse fuel
flow to the boost pump.
Location
The check valves are located on the pump discharge lines inside the fuel tanks.
Physical Description
The valve consists of a spring-loaded-closed flapper valve mounted in a housing. The housing has three ports: fuel in, fuel out and a pressure sensing port.
The pressure sensing port is located upstream of the flapper valve.
Main tank boost pump check valves differ from center tank boost pump check
valves as the cracking pressure for main tank boost pump check valves is
higher than the cracking pressure for center tank valves.
S cracking pressure of the center tank check valve is 1,5 psi,
S cracking pressure of the wing tank check valve is 12 psi.
For Training Purposes Only
Access
The access to the valves is by entering the fuel tanks.
FRA US/E ur
Oct.96
Page: 50
B737-300/400/500
28-40
For Training Purposes Only
Lufthansa Technical Training
FUEL
FUEL FEED SYSTEM
Figure 25
FRA US/E ur
Oct.96
Boost Pump Check Valves and Bypass Valve
Page: 51
Lufthansa Technical Training
FUEL
FUEL FEED SYSTEM
B737-300/400/500
28-40
ENGINE FUEL FEED VALVES
Engine Fuel Shutoff Valve / Engine Crossfeed Valve
Purpose
Fuel to each engine passes through the engine’s respective fuel shutoff valve.
For supplying fuel from one tank to both engines, the crossfeed valve is used.
Location
The two fuel shutoff valves are located on the front spars outboard of the engines. The crossfeed valve is located on the rear spar on the right side
Physical Description
The valve is motor operated, sliding gate, semi-submerged with manual override handle. The valve consists of gate, actuator, and port adapter assemblies.
The port adapter assembly is mounted inside the tank and supports the manifold. The gate assembly slides into the adapter from the dry side, and the actuator couples to the gate shaft with an index-tooth spline. Three thermal relief
valves are provided.
APU Fuel Shutoff Valve
The APU fuel valve is mounted on the left wing rear spar and controls delivery
of fuel from tank No. 1 to the APU.
The valve is an electric motor-driven rotary gate valve with manual override
handle. The manual override handle provides a visual check of the valve position and a manual method of positioning the valve when the electric motor is
not energized.
To limit pressure buildup in the fuel lines, the valve housing incorporates a thermal relief valve.
The valve is operated by 28 Volt DC Power and is contolled by the APU master
switch for opening and closing, or by APU fire handle for closing only.
Maintenance Practices
The main tank or tanks must be defueled to the quantity indicated on the placard prior to removal of the valve.
Access
The fuel shutoff valves are accessible through individual panels located outboard of the engines on the wing leading edge. The crossfeed valve is accessible from the right main wheel well.
For Training Purposes Only
Power
The valves require 28 Volt DC power.
Operation
When the motor is energized, the actuator assembly drives the gate to close or
open the valve. The fuel shutoff valve is opened by movement of the engine
start lever from CUTOFF to IDLE position. It is closed by the start lever or by
the operation of the corresponding fire handle.
The crossfeed valve is opened or closed by a rotary switch located on the
P5-2 panel. The valve can also be operated by the manual override handle
providing that the corresponding circuit breaker has been pulled. The override
handle also indicates the position of the valve.
The thermal relief valves limit the pressure trapped in the manifold to 45-60 psi
with the system shut down.
FRA US/E ur
Feb. 2000
Page: 52
Lufthansa Technical Training
FUEL
FUEL FEED SYSTEM
B737-300/400/500
28-40
FUEL BOOST
PUMP
FUEL BOOST
PUMP
FUEL BOOST
PUMP
ENGINE FUEL
SHUTOFF VALVE No. 1
ENGINE FUEL
SHUTOFF VALVE No. 2
APU FUEL
SHUTOFF
VALVE
APU DC
BOOST
PUMP
FUEL
CROSSFEED
VALVE
WING SPAR
WING SPAR
For Training Purposes Only
VALVE
POSITION
INDICATOR
MANUAL
OVERRIDE
HANDLE
APU FUEL
VALVE
FWD
APU FUEL SHUTOFF VALVE
ENGINE FUEL SHUTOFF VALVE / ENGINE CROSSFEED VALVE
Figure 26
FRA US/E ur
Feb. 2000
SHUTOFF
VALVE
Engine Fuel Feed Valves
Page: 53
Lufthansa Technical Training
FUEL
FUEL FEED SYSTEM
B737-300/400/500
28-40
Engine Fuel Shutoff Valve Electrical Circuit
Purpose
Fuel from the tanks passes through the two fuel shutoff valves before entering
the engine fuel systems.
Location
The valves are located on the front spars outboard of the engines. The indicating lights and associated circuits are on the P5 panel. Controls for valve operation are below the start levers and on P8 fire control panel.
Power
The power for the light and valve operation is from 28 volt dc hot battery bus.
The circuit breakers are on P6 panel.
Operation
The valve is opened and closed by the engine start lever, and it can be closed
by the respective fire handle. The indicating FUEL VALVE CLOSED blue light
operates as follows:
- Valve closed - dim blue light
- Valve in transit - bright blue light
- Valve open - no light
Power for the light is available when relay R41 is energized by battery switch
ON. The light is illuminated when a ground is available through both transistors
(bright) or through a zener diode and transistor (dim).
Power
The power for the valve and light operation is from 28 Volt DC battery bus the
circuit breaker is on the P6 panel.
Operation
The valve is opened and closed by a rotary switch on P5-2 panel.
The indicating VALVE OPEN blue light operates as follows:
- Valve closed - no light
- Valve in transit - bright blue light
- Valve open - dim blue light
Light is illuminated when ground available through both transistors (bright) or
through a zener diode and transistor (dim).
For Training Purposes Only
Crossfeed Valve Electrical Circuit
Purpose
A fuel crossfeed valve provides the means of directing fuel to both·engines
from a single tank.
Location
The valve is located on the rear spar of tank No. 2, the indicating light, switch
and associated circuits are in the P5-2 panel.
Physical Description
The switch for valve operation is a rotary type. Above the switch is a blue
crossfeed VALVE OPEN light.
FRA US/E ur
Oct.96
Page: 54
Lufthansa Technical Training
FUEL
FUEL FEED SYSTEM
B737-300/400/500
28-40
FUEL SHUTOFF
VALVE INDICATION
28V DC
BAT BUS
CROSSFEED VALVE
B
START
B
FUEL S/O VALVE ENG 2
CUTOFF
S596 ENG 2 START
LEVER SWITCH
L2 ENG 2 FUEL VALVE
CLOSED LIGHT
FUEL S/O VALVE ENG 1
OPEN
28V DC
HOT BAT BUS
NORMAL
M
SW HOT BAT BUS
CLOSED
FIRE
S9 ENG 2
FIRE SW
R41 GEN POWER
CONTROL RLY
P6-3 CIRCUIT BREAKER PANEL
V38 ENG 2 FUEL
SHUTOFF VALVE
P8-1 ENG & APU FIRE
CONTROL PANEL
B
B
L1
L3
L2
L3 CROSSFEED VALVE
OPEN LIGHT
L1, L2
FUEL VALVE
CLOSED
L3
VALVE
OPEN
F.V.C.
F.V.C.
0
-20 +20
-40
FILTER
BYPASS
CROSS
CLOSE
+40
C
CLOSED
NO
FILTER
BYPASS
V.O.
C
NC
OPEN
FEED
S3
CROSSFEED
CONT SW
S3
M
OPEN
V39 FUEL
CROSSFEED VALVE
B
For Training Purposes Only
B
L1 ENG 2 FUEL VALVE
CLOSED LIGHT
NORMAL
OPEN
START
M
FIRE
S8 ENG 1
FIRE SW
CUTOFF
CLOSE
S595 ENG 1 START
LEVER SWITCH
V37 ENG 1 FUEL
SHUTOFF VALVE
P8-1 ENG AND APU
FIRE CONTROL PANEL
P5-2 FUEL SYSTEM PANEL
(102520)
Figure 27
FRA US/E ur
Oct.96
Fuel Valve Electrical Circuit
Page: 55
B737-300/400/500
28-40
ENGINE FUEL SHUTOFF VALVE SWITCHES
Engine Fuel Shutoff Valve Switch
General
The switch for the fuel shutoff valve is installed on brackets in pilot’s control
stand. There is one switch for each start lever.
You can get access to the switch for the fuel shutoff valve for the No. 1 engine
from the left side of the pilot’s control stand.
You can get access to the switch for the fuel shutoff valve for the No. 2 engine
from the right side of the pilot’s control stand.
For Training Purposes Only
Lufthansa Technical Training
FUEL
FUEL FEED SYSTEM
FRA US/E ur
Oct.96
Page: 56
Lufthansa Technical Training
FUEL
FUEL FEED SYSTEM
B737-300/400/500
28-40
REVERSE
THRUST
LEVER
CONTROL
LINK
FORWARD
THRUST
LEVER
ENGINE
START
LEVERS
THRUST DRUM
START LEVERS
START
LEVER
START DRUMS
SWITCH
ACTUATING
CAMS
FUEL VALVE
SHUTOFF
SWITCHES
ENGINE START
LEVER-ACTUATED
SWITCHES
ACCESS PANEL
SWITCH
ACTUATING
CAMS
For Training Purposes Only
PILOT’S CONTROL STAND
START
DRUM
FUEL VALVE
SHUTOFF
SWITCHES
FWD
IGNITION
SWITCHES
FWD
Figure 28
FRA US/E ur
Oct.96
Engine Fuel Shutoff Valve Switches
Page: 57
Lufthansa Technical Training
FUEL
DEFUELING
B737-300/400/500
28-40
DEFUELING
General
The fuel system is designed to permit complete or partial defueling of one or
more tanks, or to permit fuel transfer to other tanks while the airplane is on
ground. To do the defueling or fuel transfer, parts of the pressure fueling, engine fuel feed, and defueling systems are used in combination.
There are four differnt procedures in order to defuel the fuel tanks
- Defuel through the pressure fueling receptacle with the airplane boost
pumps and the defueling (suction) pump on the refuel truck. This procedure defuels all of the tanks at the same time. It is the fastet procedure
to defuel the tanks.
- Defuel through the pressure fueling receptacle with the airplane boost
pumps only.
- Defuel through the pressure fueling receptacle with the defueling (suction) pump on the fuel truck only. Use this procedure only if it is necessary. It is a very slow procedure.
- Defuel through the pressure fueling receptacle with the external power
control unit. For this procedure, it is a special ground support equipment
required.
Operation
The valve is opened and closed by the use of the red valve handle. When the
valve is open, the access panel can not be closed due to panel/handle interference.
Manual Defueling Valve
For Training Purposes Only
Purpose
The defueling valve is used for defueling of the tanks and for fuel transfer between the tanks.
Location
The valve is located inboard of the fueling station.
Physical Description
The valve is a manually operated, sliding gate, semi-submerged unit.
The valve consists of a gate, actuator, and port adapter assemblies. The port
adapter assembly is mounted inside the tank and supports the fuel line. The
gate assembly slides into the adapter from the dry side.
Access
Access to the valve is through a panel inboard of the fueling station.
FRA US/E ur
Oct.96
Page: 58
B737-300/400/500
28-40
DEFUELING VALVE
For Training Purposes Only
Lufthansa Technical Training
FUEL
DEFUELING
Figure 29
FRA US/E ur
Oct.96
Manual Defueling Valve
Page: 59
Lufthansa Technical Training
FUEL
FUEL SCAVENGE SYSTEM
28-50
28-50
CENTER TANK FUEL SCAVENGE SYSTEM
CENTER TANK FUEL SCAVENGE SYSTEM
Purpose
The scavenge fuel shutoff valve, when energized, allows fuel from the No. 1
forward boost pump to the center wing scavenge jet pump.
Location
The valve is mounted on the front spar of the No. 1 fuel tank outboard of the
No. 1 forward boost pump.
Physically Description
The unit consists of a valve body and solenoid assembly containing a solenoid,
plunger, poppet, pins and spring.
Access
The valve is accessible from the front spar of the No. 1 tank.
Operation
When the center tank boost pump switches are on, the solenoid is relaxed and
the plunger/poppet assembly is spring-loaded closed against the valve seat
insert.
Turning both center tank boost pump switches off will energize the solenoid.
The poppet will pull away from the valve seat allowing fuel flaw from the No. 1
tank forward boost pump to the scavenge fuel jet pump.
For Training Purposes Only
B737-300/400/500
Maintenance Practices
Removal of the valve requires defueling the No. 1 tank and extension of the
leading edge flaps to gain access to the attaching hardware. At the front spar,
disconnect the electrical connector and bonding jumper from the valve. Remove the nut and washer. Inside the No. 1 tank disconnect the fuel lines and
remove the valve.
FRA US/E ur
Feb. 99
Center Tank Fuel Scavenge Flow Indicator (Optional)
Purpose
The scavenge flow indicator is used for the center tank fuel scavenge system.
Location
The indicator is located on the front spar of the No. 1 fuel tank.
Physical Description
It consists of a flapper check valve assembly which is connected to a pointer
on the indicator. The deflection of the flapper is proportional to the flow through
the system.
The indicator has three color bands:
- Blue band - no flow
- Red band - flow up to 280 lb / hr at 21°C (70°F)
- Green band - flow above 280 lb / hr
Access
Access to the indicator is by extending the leading edge flap.
Operation
The system is checked by observing the indicator with the center tank boost
pumps switched off and the tank No. 1 forward boost pump switched on.
Maintenance Practices
The indicator removal requires defueling of tank No. 1.
Page: 60
Lufthansa Technical Training
FUEL
FUEL SCAVENGE SYSTEM
B737-300/400/500
28-50
FUEL SCAVENGE
FLOW INDICATOR /
CHECK VALVE
FUEL BOOST
PUMP 1 / FWD
1
FUEL SCAVENGE
JET PUMP
FUEL SCAVENGE
SHUTOFF VALVE
FUEL SCAVENGE
SHUTOFF VALVE
CENTER TANK
NO. 1 TANK
2
O-RING
FLAPPER
CHECK VALVE
LOCKWIRE TO
STRUCTURE
FUEL SCAVENGE
JET PUMP
FRONT SPAR
WASHER
FUEL SCAVENGE
FLOW INDICATOR/
CHECK VALVE
NUT
FWD
For Training Purposes Only
1
FRONT SPAR
Location: Left wing front spar
Leading Edge Flaps must be extendet
CAP
1
Figure 30
FRA US/E ur
Feb. 99
1
NOT INSTALLED ON ALL AIRPLANES
2
NOT INSTALLED ON AIRPLANES WITH FUEL
SCAVENGE FLOW INDICATOR/CHECK VALVE
Center Tank Fuel Scavenge System
Page: 61
Lufthansa Technical Training
FUEL
FUEL SCAVENGE SYSTEM
B737-300/400/500
28-50
FUEL SCAVENGE SYSTEM CONTROL LOGIC
Purpose
The fuel scavenge circuit controls the operation of the scavenge fuel shutoff
valve.
Location
The circuit components are located in the P5 and P6 panels and in the electronic equipment compartment.
Physical Description
The scavenge circuit consists of power sources, two center tank boost pump
switches and -relays, M528 Engine Accessory Module and the scavenge fuel
shutoff valve solenoid.
Power
Power supply for the center tank boost pumps is 115 Volt AC and for the control circuit 28 Volt DC.
For Training Purposes Only
Operation
The circuit is designed to energize the scavenge fuel shutoff valve solenoid
whenever both center tank boost pump switches are positioned to off and keep
the solenoid energized for 20 minutes.
A prerequisite to this operation is that one (or both) center tank boost switches,
must be turned on to arm the M528 control logic. If this is not accomplished,
the scavenge fuel shutoff valve solenoid will not be energized even through
both center tank boost pump switches are in the off position.
FRA US/E ur
Feb. 2000
Page: 62
Lufthansa Technical Training
FUEL
FUEL SCAVENGE SYSTEM
B737-300/400/500
28-50
28V DC
BUS 2
C65
FUEL CONTROL
-NO.1 FWD
-NO.2 AFT
-R CENTER
OFF
20 MINUTE
TIMER
V129 FUEL SCAVENGE
SHUTOFF VALVE
ON
S9 RIGHT CENTER
TANK PUMP SW
THE SCAVENGE FUEL VALVE REMAINS OPEN FOR
20 MINUTES AFTER S8 AND S9 ARE TURNED OFF.
OFF
28V DC
BUS 1
C64
FUEL CONTROL
-NO. 1 AFT
-NO.2 FWD
-L CENTER
ON
S8 LEFT CENTER
TANK PUMP SW
P6 CIRCUIT BREAKER
PANEL
P5-2 FUEL SYSTEM PANEL
FUEL SCAVENGE
CHECK VALVE
M528 ENGINE ACCESSORY UNIT (E3-2)
FORWARD FUEL BOOST
PUMP FOR THE NO. 1 TANK
FUEL SCAVENGE
JET PUMP
FUEL SCAVENGE
SHUTOFF VALVE
CENTER
TANK
OUTLET
For Training Purposes Only
INLET
NO. 1 TANK
FLAPPER
CHECK VALVE
NO. 2 TANK
ENGINE
FUEL FEED
MANIFOLD
Figure 31
FRA US/E ur
Feb. 2000
Fuel Scavenge System Control Logic
Page: 63
Lufthansa Technical Training
FUEL
FUEL SCAVENGE SYSTEM
B737-300/400/500
28-50
FUEL SCAVENGE JET PUMP
General Description
The fuel scavenge jet pump causes a low pressure in the fuel scavenge transfer line when the forward fuel boost pump of tank No. 1 is running and the electrically controlled fuel scavenge shutoff valve is energized.
For Training Purposes Only
Inspection / Check
It is not necessary to go into or defuel the tank in order to clean the nozzle
opening on the jet pump. The flapper valve prevents fuel flow when the nozzle
has been removed.
FRA US/E ur
Oct.96
Page: 64
Lufthansa Technical Training
FUEL
FUEL SCAVENGE SYSTEM
B737-300/400/500
28-50
FUEL SCAVENGE
JET PUMP (REF)
WASHER
FWD
NOZZLE PLUG
JET PUMP
RETAINING
For Training Purposes Only
NUT
JET PUMP NEEDLE
ORIFICE
FRONT
SPAR
FLAPPER
CHECK
VALVE
Figure 32
FRA US/E ur
Oct.96
Fuel Scavenge Jet Pump Check
Page: 65
Lufthansa Technical Training
FUEL
FUEL QUANTITY INDICATING SYSTEM
B737-300/400/500
28-60
28-60
FUEL QUANTITY INDICATING SYSTEM
FUEL QUANTITY INDICATING SYSTEM
Purpose
The fuel quantity indicating units measure the weight of usable fuel in the
tanks. Two types of quantity indicators are used, capacitance for indicators and
manual measuring sticks. The measuring sticks are provided for the main tanks
only.
POWER
The indicators utilize 115 volt ac power.
For Training Purposes Only
Location
The capacitance gaging system tank units and compensators are located inside the tanks. The measuring sticks are located in main tank access panels.
Main Tank - 12 tank units, 1 compensator, 5 measuring sticks.
Center Tank - 2 tank units, 1 compensator.
Physical Description
Tank Units are hollow coaxial cylindrical capacitors mounted vertically to ribs
inside each fuel tank. Fuel is used as the dielectric. The inner tube is profiled to
correspond to the irregular shape of the inside of the fuel tank. The tank units
are located throughout the tanks so an accurate reading is provided whatever
the attitude of the airplane.
Compensator Units are hollow coaxial cylindrical capacitors mounted vertically to ribs inside each fuel tank at the lowest portion so that the compensator
is always submerged in fuel. The compensator is connected electrically into the
gaging circuit to compensate for the different dielectric constants of fuels of
differing chemical compositions.
The tank units are connected together in parallel. The wiring harness from each
main tank is connected to a bussing plug located in the front spar of the wing.
The center tank bussing plug is located on the forward wall of the left main
wheel well.
The TSDs (Transient Suppression Devices) suppress electrical transients,
preventig them from reaching the FQIS wiring and components inside the fuel
tanks.
Drip Sticks are calibrated tubes which can be pulled down for reading of fuel
height.
The Indicators, Summation Unit and Trimmers are in the flight compartment. Repeater indicators are in the fueling station.
FRA US/E ur
Mar. 2002
Page: 66
Lufthansa Technical Training
FUEL
FUEL QUANTITY INDICATING SYSTEM
B737-300/400/500
28-60
115 V/AC Standby Bus
Ext.Power connected
Fuel Summation Unit
FUEL
F.S.U.
ERR
%
Digital Fuel
Quantity Indicator
at Pilots Center Panel
DIG.
F.Q.I.
FMSC
Flight Managment
System Computer
DIG.
F.Q.I.
FMSC Control Display Unit (CDU)
Test Switch
Pilot’s Center Panel
Select Switch
at Refuel Station
to ”TEST GAGES”
Capacitance Trimmer
FUEL
DIG.
F.Q.I.
ERR
DIG.
F.Q.I.
Digital Fueling
Quantity Indicator
at the Refueling Station
%
”Aux Fueling Power”
(hold, at refueling Station)
TSD
TSD
Refueling Bay Door Open
Power Switch
(Contact shown Door Close)
Bussing Plug
Bussing Plug
Center
For Training Purposes Only
(No Measuring Stick)
Tank No. 2
Tank No. 1
(alternate 5 Measuring Sticks)
(alternate 5 Measuring Sticks)
12 Tank Units
1 Compensator Unit
2 Tank Units
1 Compensator Unit
115 V/AC Standby Bus
Ext.Power connected
12 Tank Units
1 Compensator Unit
Bussing Plug
TSD (Transient Suppression Device)
Figure 33
FRA US/E ur
Mar. 2002
Fueling System Schematic
Page: 67
Lufthansa Technical Training
FUEL
FUEL QUANTITY INDICATING SYSTEM
28-60
FUEL QUANTITY INDICATION CIRCUIT
Purpose
The fuel quantity circuit and indicators measure the weight of usable fuel in the
fuel tanks.
Location
System components are located in the flight compartment, fuel tanks and at
the fueling station. Flight compartment components consist of fuel quantity indicators, capacitance trimmer, summation unit and an indicator test switch. Fuel
tank components consist of tank units, compensator units and measuring
sticks. Fueling quantity indicators and indicator test switch are located at the
P15 fueling station panel.
Physical Description
Fuel Quantity Indicator
S Digital fuel quantity indicators on P2 panel show the weight of fuel in each
tank. Each indicator consists of a microcomputer system, radial and a digital
liquid crystal display (L.C.D). The microcomputer measures the capacitance
and resistive current in the tank units. It monitors the leakage current and
when it reaches an unacceptable level, an error code 0 through 9 are displayed, or the display blanks, to assist in troubleshooting the system.
For Training Purposes Only
B737-300/400/500
Fueling Quantity Indicator
S Fueling quantity indicators on the P15 panel show the weight of fuel in each
tank. The fueling quantity indicators function as repeaters of the fuel quantity indicators located in the flight compartment and aid the ground crew in
fueling or defueling operations. The fueling quantity indicators are interchangeable with the fuel quantity indicators. The fueling quantity indicators
are operative only when the fueling station door is open. Error codes 8, A
and F are displayed or the display cycles on/off or blanks on the repeater
indicator.
FRA US/E ur
Mar. 2002
Fuel Summation Unit
S The fuel summation unit takes individual fuel quantity indicator voltage signals and sums them for an output voltage signal representative of the total
fuel remaining. The flight management computer system uses this voltage
signal to derive airplane gross weight related performance data and provides display of total fuel.
Trim Adjustment Screws (Trimmer)
S Capacitance trimmers, can be adjusted to standardize the total tank capacitance. This adjustment allows for replacement of indicators without recalibrating the indicator gage.
Transient Suppression Device
S The Transient Suppression Device is near the penetration to each fuel tank.
This is a safety device to prevent excess power from entering the fuel tank.
Power
The power supply for the indicators is 115 volt ac from the standby bus or external power. If external power is plugged in and the power is good, relay R10
is energized connecting the fuel quantity circuit to the external power ac bus.
Now, if ac power is applied to the airplane such that the number 2 bus transfer
relay (R4) is energized, R 309 will energize switching the fuel quantity circuit
power source to the standby ac bus. This is done to connect the fuel quantity
circuit to the same power source as the flight management computer (FMC) to
phase-match the summation unit total fuel quantity, fuel quantity reference,
and ground reference analog voltages with the FMC reference voltage.
Operation
The tank units function as variable capacitors, their capacitance value being
determined by fuel level in the tank.
A single chip microcomputer system within the indicator performs the measurement of the current through the tank units. The microcomputer converts the
capacitance current to a radial and a digital readout of fuel quantity.
The microcomputer monitors the fuel quantity indicating system and provides
an error indication and code to assist in troubleshooting.
Page: 68
Lufthansa Technical Training
FUEL
FUEL QUANTITY INDICATING SYSTEM
B737-300/400/500
28-60
N62 TANK 2 FUELING
IND (P15)
115V AC
STBY BUS
N63 CENTER TANK
FUELING IND (P15)
INTERNALS SAME
AS N50
C397
FUEL SYSTEMS
QTY
115V AC
EXT PWR
RECEPTACLE C398
EP GND
FUELING
INTERNALS SAME
AS N50
N61 TANK 1 FUELING
FUELING IND (P15)
INTERNALS SAME
AS N50
F12
F10
F9
R10 FUEL POWER
SELECT RELAY
(E3-3)
P6-3 CIRCUIT BREAKER PANEL
F21
F8
F7
F6
S160 FUEL IND
TEST IND (P15)
F5
R309 FUEL POWER
TRANSFER RELAY
F4
F3
POWER
SUPPLY
COMP
POWER
SUPPLY
LB/KG SELECT
M1097
TRIMMER
TANK 2
TANK 2
FUEL
QTY
PROC
TANK 1
F18
F11
FMC
CTR TANK
SELF TEST
TRANSIENT
SUPPRESSION
DEVICE
FUEL SUMMATION UNIT
N50 TANK 2 FUEL QTY IND
F2
D1586
BUSSING M290 ADAPTER
ASSY TANK 2
PLUG
F16
F17
For Training Purposes Only
INTERNALS
SAME AS
N50
COMP
N64 CENTER TANK
FUEL QTY IND
M1098 TRIMMER
CENTER TANK
INTERNALS
SAME AS
N50
N49 TANK 1
FUEL QTY IND
R11 REFUELING POWER
SELECT RELAY (E3-3)
S257 FUEL QTY
TEST SW
M1096 TRIMMER
TANK 1
PILOTS INSTRUMENT PANEL
Figure 34
FRA US/E ur
Mar. 2002
F14
D1590
BUSSING
PLUG
M291 ADAPTER
ASSY CTR TANK
INTERNALS
SAME AS
D1586
INTERNALS
SAME AS
M290 OF
TANK 2
D1588
BUSSING
PLUG
M290 ADAPTER
ASSY TANK 1
TRANSIENT
SUPPRESSION
DEVICE
INTERNALS
SAME AS
TSD TANK 2
Fuel Quantity Indicating Schematic
Page: 69
Lufthansa Technical Training
FUEL
FUEL QUANTITY INDICATING SYSTEM
B737-300/400/500
28-60
FUEL QUANTITY SYSTEM BUSSING PLUG AND TRANSIENT
SUPPRESSION DEVICE
Bussing Plug
Tank unit leads in a given tank, form a harness which terminates at a receptacle.
S The receptacles for the No. 1 and No. 2 tanks are found in the applicable
wing front spar,
S and for the center tank in the left forward bulkhead in the wheel well for the
main landing gear.
Attached to each receptacle is a bussing plug assembly. The plug assembly
connects the tank units in parallel.
Transient Suppression Device
The TSD is a safety device that provides isolation of excess power from the
fuel quantity signals into the fuel tank. A special EMI shielded cable connects
the TSD to the fuel tank bussing plug.
S The TSDs for the No. 1 and No. 2 tanks are located on the respective wing
front spar,
S and for the center tank on the main wheel well ceiling near the System A
hydraulic reservoir.
For Training Purposes Only
Maintenance Advice:
For troubleshooting the Fuel Quantity Indicating System a system tester can be
connected to the indicator plug and to the bussing plug. But the respective TSD
must be bypassed by using the TSD Bypass Cable.
For instruction see the AMM.
FRA US/E ur
Mar. 2002
Page: 70
Lufthansa Technical Training
FUEL
FUEL QUANTITY INDICATING SYSTEM
B737-300/400/500
28-60
TRANSIENT
SUPPRESSION
DEVICE
(Tank No. 2 similar)
TANK UNITS
(EXAMPLE)
BULKHEAD
RECEPTACLE
FOR THE
FUEL TANK
CENTER TANK
1
BUSSING PLUG
TANK NO. 1
(Tank No. 2 similar)
BUSSING PLUG
CENTER TANK
BUSSING PLUG
ELECTRICAL
CONNECTOR
COMPENSATOR
UNITS
(1 EACH TANK)
O-RING SEAL
TRANSIENT
SUPPRESSION
DEVICE
(CENTER TANK)
NO. 1 TANK SHOWN
(NO. 2 TANK OPPOSITE)
BUSSING PLUG
BULKHEAD
RECEPTACLE
FOR THE
FUEL TANK
For Training Purposes Only
2
BUSSING PLUG
PLUG
ELECTRICAL
CONNECTOR
1
2
TRANSIENT SUPPRESSION DEVICE
Figure 35
FRA US/E ur
Mar. 2002
AIRPLANES WITH A RECTANGULAR
BUSSING PLUG
AIRPLANES WITH A CIRCULAR
BUSSING PLUG
COUPLING RING
BUSSING PLUG
Component Location
Page: 71
Lufthansa Technical Training
For Training Purposes Only
FUEL
FUEL QUANTITY INDICATING SYSTEM
B737-300/400/500
28-60
FUEL QUANTITY INDICATOR
Fuel Quantity Indicator
Digital fuel quantity indicators show the weight of fuel and percentage of full
capacity in each fuel tank.
Each fuel quantity indicator has a single chip microcomputer system and a digital liquid crystal display (LCD). The microcomputer sends periodicaly a short
time AC-Signal of 10 Volt and 5 kHz over the LO-Z wire directly to the tank
units, there after to the compensator unit and measures the current in the HI-Z
wire. By this capacity measuring method, the micro computer calculates the
fuel quantity.
When a parameter reaches an unacceptable level, the fuel quantity indicator
shows either normal or zero fuel quantity, the word ERR, and an error code
between 0 and 9. The error code can be used to help in troubleshooting the
system.
To clear any stored error codes, including those stored by activating the selftest switches, cycle indicator power from ON to OFF to ON again, with the EP
GND FUELING and fuel QTY circuit breakers on the P6 panel.
FUEL
ERROR CODES:
KG
Master Indicator
0 to 9
ERR
Repeater Indicator
A, F or 8
%
Refuel Quantity Indicator
Refuel quantity indicators on the P15 panel show the weight of fuel in the fuel
tanks. The refuel quantity indicators function as repeaters of the fuel quantity
indicators found in the control cabin and help the ground crew in refuel or defueling operations.
The refuel quantity indicators are interchangeable with the fuel quantity indicators. The refuel quantity indicators operate only when the access door for the
station is open.
When the access door is closed, power to the refuel quantity indicators is interrupted by a reed-switch. The fueling quantity indicators monitor the signal received from the fuel quantity indicators and display an error code if a system malfunction exists.
FRA US/E ur
Dec. 97
Page: 72
B737-300/400/500
28-60
For Training Purposes Only
Lufthansa Technical Training
FUEL
FUEL QUANTITY INDICATING SYSTEM
TO REPEATER INDICATOR &
SUMMATION UNIT
Figure 36
FRA US/E ur
Dec. 97
Fuel Quantity Indicator
Page: 73
B737-300/400/500
28-60
FUEL QUANTITY INDICATOR TEST
Operation - Fuel Quantity Indicator
By pressing of the fuel quantity test switch on pilots center panel, a test of the
fuel quantity indicators will be started.
Test sequence:
- push and hold test switch until Indicators displays ”0” and ”ERR 4”
- release test switch
- all segments ”ON” for 2 sec.
- all segments ”OFF” for 2 sec.
- if Error Codes memorized, each will displayed for 2 sec. one after
another (numerical order). The highest code will displayed at first.
- maximum possible indicator value of each indicator
- the indicators display actual quantity
NOTE: The test is not possible or unuseable, if the following actual ERRCodes are displayed:
S 2, 3, 5, 6 or 8
Does a ERR-Code ”3” exist, the indicator will display ERR-Code ”2” while the
test switch is being pressed.
When the following actual ERR-Codes are displayed:
S 1, 3, 5 or 7
the indicator accuracy will shift about 3 %.
During fueling indicator test, the repeater indicators on the fueling station show
a display test.
Operation - Fueling Quantity Indicator
By switching of the Test Gages & Aux Fueling Power Control Switch to ”Test
Gages Position”, a test of the fueling indicator will be started.
Test sequence:
- push and hold test switch to ”Test Gages” position
- all segments ”ON”
- the indicators show ”Blank”
- maximum possible indicator value
- release switch
- the indicators display actual quantity
NOTE: During fueling quantity indicator test, the fuel quantity indicators in the
cockpit display ERR-Code ”3”.
For Training Purposes Only
Lufthansa Technical Training
FUEL
FUEL QUANTITY INDICATING SYSTEM
FRA US/E ur
Dec. 97
Page: 74
B737-300/400/500
28-60
1
2
3
4
5
6
For Training Purposes Only
Lufthansa Technical Training
FUEL
FUEL QUANTITY INDICATING SYSTEM
Figure 37
FRA US/E ur
Dec. 97
Fuel Quantity Indicator Test
Page: 75
B737-300/400/500
28-60
FUEL QTY INDICATOR TEST (CONT.)
For Training Purposes Only
Lufthansa Technical Training
FUEL
FUEL QUANTITY INDICATING SYSTEM
FRA US/E ur
Dec. 97
Page: 76
Lufthansa Technical Training
FUEL
FUEL QUANTITY INDICATING SYSTEM
B737-300/400/500
28-60
ERROR FUEL QUANTITY
CODE
INDICATOR VALUE
MASTER INDICATOR
USUAL
CAUSE
RECOMMENDED
ACTION
0
ZERO
A TANK UNIT IS NOT INSTALLED
or A TANK UNIT IS DISCONNECTED
Verify continuity of in-tank wiring to each Tank Unit,
HI-Z isolation from shield.
1
NORMAL
TANK CONTAMINATION
Drain the tank and check condition of each Tank Unit.
2
ZERO
A BAD HI-Z LEAD
3
NORMAL
BAD COMPENSATOR WIRING
Check HI-Z wire from Indicator to tank, LO-Z wires to Tank Units
and Compensators.
Check LO-Z wire from Indicator to Compensator.
4
ZERO
BAD TANK UNIT WIRING
5
NORMAL
BAD COMPENSATOR
6
ZERO
BAD TANK UNIT
7
NORMAL
CONTAMINATION OR
WATER IN COMPENSATOR
8
ZERO
BAD INDICATOR
9
NORMAL OR ZERO
INCORRECTLY CALIBRATED INDICATOR
Replace Indicator. Check for short to ground on Tank Unit and
Compensator LO-Z.
Replace Indicator.
BLANK
BAD INDICATOR
Replace Indicator.
Verify proper operation of master indicator. Check wiring between
master and repeater indicators.
Correct problem at master indicator.
Check LO-Z wire from Indicator to Tank Units.
Check for shorted Test Switch.
Drain the tank and check condition of Compensator.
Check HI-Z shield continuity.
Check Condition of each Tank Unit using Test Set.
Check HI-Z shield continuity. Check for water and ice in Tank Units.
Drain the sump area and check condition of Compensator.
Check Compensator HI-Z shield continuity.
For Training Purposes Only
REPEATER INDICATOR
A
ZERO
PARITY ERROR
F
same data as
master
BAD MASTER INDICATOR
8
ZERO
BAD INDICATOR
Replace Indicator. Check for short to ground on Tank Unit
and Compensator LO-Z.
NO DATA FROM MASTER INDICATOR
Check master indicator operation.
BAD COMPUTER
Replace Indicator.
CONTINUOUS
DISPLAY TEST
BLANK
Figure 38
FRA US/E ur
Dec. 97
Fuel Qty. Ind. Error Code Table
Page: 77
Lufthansa Technical Training
FUEL
FUEL QUANTITY INDICATING SYSTEM
B737-300/400/500
28-60
MEASURING STICK
Purpose
The measuring sticks are used to measure the fuel quantity in tanks No. 1 and
2 by mechanical means. The fuel quantity measurements obtained by measuring sticks assist the ground crew in fueling operations when electrical power for
fuel quantity indicators is not available. The measuring sticks are also used for
comparing the fuel weight indicated by the fuel quantity indicators to the reading obtained by measuring sticks.
tank when its indicators do not operate. You can also move fuel to refuel one
of the wing tanks as an alternative to the fuel measuring stick procedure.
Use the Fuel Measuring Sticks to Refuel the No. 1 Tank or the No. 2
Tank when the Fuel Quantity Indicating System does not operate
NOTE: Calculating of the fuel weight by the Measuring Sticks
(Ref. Maintenance Manual)
Location
There are five measuring sticks for each main tank, located in wing fuel tank
access panels No. 1, 4, 6, 8, and 10.
Physical Description
The measuring stick consists of a fiberglass tube in a housing attached to the
access panel. The tube is graduated in inches, gallons or kilograms, (a customer option). At the side of the housing is a removal valve, which allows stick
removal without defueling.
For Training Purposes Only
Operation
To determine the fuel quantity in the tank, the measuring stick is unlocked and
slowly lowered until the fuel enters the upper end of the stick and drips out of
the lower end. The drip hole is marked on the base of the measuring stick with
a red arrow.
Tables of capacities, corrected for airplane attitude, are found in the measuring
stick document.
Maintenance Practices
The sticks can be removed without defueling the tanks. Removal of 3 retaining
screws allows the stick assembly to be pulled out from the access panel.
General
You can refuel a tank with a fuel quantity indicating system that does not operate correctly (a bad indicator). You can do this task with the fuel measuring
sticks in the No. 1 tank or the No. 2 tank. You must also use the applicable document to calculate the fuel quantity from the values on the fuel measuring
sticks. You must move fuel from a different tank if you must refuel the center
FRA US/E ur
Oct.96
Page: 78
Lufthansa Technical Training
FUEL
FUEL QUANTITY INDICATING SYSTEM
B737-300/400/500
28-60
FUEL MEASURING STICK
(IN TANK ACCESS DOORS
NO. 1,4,6,8 AND 10)
FLOAT
CALIBRATED ROD
FLAPPER
VALVE
NO. 2 TANK SHOWN
(NO. 1 TANK OPPOSITE)
SLEEVE
MEASURING
STICK
SPRING
BODY
MEASURING
STICK HOUSING
RETAINING
SCREW
MOUNTING BASE
For Training Purposes Only
BAYONET
LOWER
WING SKIN
LOCKING
PIN
MEASURING STICK
READING PLANE
DRIP
HOLE
TANK ACCESS
DOOR
SCREWDRIVER SLOT
FUEL MEASURING STICK WITH OPEN TUBE
Figure 39
FRA US/E ur
TANK ACCESS
DOOR
Oct.96
SOCKET
HEAD OF THE
MEASURING
STICK
FUEL MEASURING STICK MAGNETIC FLOAT TYPE
Fuel Measuring Stick
Page: 79
Lufthansa Technical Training
For Training Purposes Only
FUEL
FUEL QUANTITY INDICATING SYSTEM
B737-300/400/500
28-60
The Open Type Fuel Measuring Stick (Dripstick)
To operate the fuel measuring stick, apply a slight pressure and turn the fuel
measuring stick 90 degrees in the counterclockwise direction. Slowly lower the
fuel measuring stick until fuel appears from the drip hole. Read the fuel quantity
on the fuel measuring stick to find the quantity of fuel in the fuel tank.
The Magnetic Float Type Fuel Measuring Stick
To operate the fuel measuring stick, it is unlocked from the base by applying a
slight pressure and a 90-degree counterclockwise turn to the end of the stick.
When the fuel measuring stick is unlocked, it is lowered to the fully extended
position. Depending on fuel level, a bearing found on top of the stick will
magnetically latch onto a magnet in the float before full extension. In this event,
a slight pressure should be applied to assure a full extension. At the fully extended position, the fuel measuring stick stops against a cushion giving a
soft firm feel.
To find the fuel level
To find the fuel level, the fuel measuring stick is gently raised until the magnetic latch is felt to engage. There is a positive feel in this position since the
magnetic latch is strong and will jerk the fuel measuring stick into its position.
The fuel measuring stick is now read to find the fuel level in the fuel tank.
If the fuel measuring stick is being monitored during a refuel or defueling operation, the float and stick sub assembly will move with the fuel level. However,
since the magnetic attachment between the magnets of the stick sub assembly
and float causes a small friction against the housing, the stick sub assembly
and float will not move up smoothly with the fuel level, but in distinct jumps as
the fuel level rises on the float to overcome the static friction. On declining fuel
levels when defueling, friction will occur in the opposite direction. Calibration
marks on the stick sub assembly are set to read on rising fuel levels and the
most accurate reading will be immediately after a jump of the stick sub assembly.
FRA US/E ur
Oct.96
Page: 80
Lufthansa Technical Training
FUEL
FUEL QUANTITY INDICATING SYSTEM
B737-300/400/500
28-60
MOUNTING BASE
ASSEMBLY
BODY
READ FUEL
QUANTITY
HERE
LOCKING
PIN
CALIBRATED
ROD
1
HEAD
DRIP
HOLE
READ FUEL
QUANTITY
HERE
WING LOWER SKIN OR
TANK ACCESS DOOR
OUTER SURFACE
WING LOWER SKIN OR
TANK ACCESS DOOR
OUTER SURFACE
STICK
SUB ASSEMBLY
LATCH
HEAD
Open Tube Type
Magnetic Float Type
For Training Purposes Only
BODY
ALIGNMENT
MARKS
1
SCREWDRIVER SLOT
Calibrated in Kilogram
For correct value see Conversion Tables in Fuel Measuring Document
Figure 40
FRA US/E ur
Oct.96
Fuel Measuring Stick
Page: 81
Lufthansa Technical Training
FUEL
FUEL FEED LOW PRESS. IND. SYSTEM
B737-300/400/500
28-70
28-70
FUEL FEED LOW PRESSURE INDICATING SYSTEM
FUEL FEED LOW PRESSURE INDICATING SYSTEM
Purpose
The condition of each boost pump is monitored by a pressure switch, sensing
pump output pressure, and an amber LOW PRESSURE light operated by the
pressure switch. The low pressure warning system also actuates the MASTER
CAUTION and the FUEL annunciator lights.
Location
The low pressure warning system circuits are located in the P5-2 panel.
Physical Description
The system consists of the six pressure switches, two center tank pump
switches, six LOW PRESSURE amber lights, MASTER CAUTION and FUEL
annunciator amber lights.
For Training Purposes Only
General
The fuel feed low-pressure indicating system provides an indication when the
output pressure of any fuel boost pump falls below a preset value. The system
consists of six pressure actuated switches and six indicator lights, one for each
fuel boost pump, together with connecting fuel lines.
If the outlet fuel pressure of a fuel boost pump falls to the preset value, its fuel
low pressure switch will be actuated; this will illuminate the appropriate indicator light on the overhead panel.
Fuel Feed Low Pressure Switches
Fuel feed low pressure switches control the fuel low pressure indicating lights
on the overhead panel. Each switch assembly consists of a cylindrical housing
containing a diaphragm and a switch. Each switch has one inlet port for a
pressure sensing line coming from a fuel boost pump. The switch is vented to
atmosphere. The fuel feed low pressure switches are located on wing front
spar.
FRA US/E ur
Oct.96
Page: 82
Lufthansa Technical Training
FUEL
FUEL FEED LOW PRESS. IND. SYSTEM
B737-300/400/500
28-70
FUEL VALVE
CLOSED
B
FUEL VALVE
CLOSED
0
FUEL +20
TEMP
-20
-40
B
+40
0C
OVERHEAD PANEL
FILTER
BYPASS B
FILTER
BYPASS B
VALVE
OPEN B
FEED
CROSS
LOW
LOW
PRESSURE PRESSURE
A
A
FUEL PUMPS
BOOST PUMP FUEL
LOW PRESSURE SWITCHES
OFF
R
L
ON
CTR
LOW
LOW
PRESSURE PRESSURE
A
A
AFT
LOW
LOW
PRESSURE PRESSURE
A
A
FWD
FWD
OFF
FUEL LOW PRESSURE
INDICATING LIGHTS
AFT
OFF
FUEL
ON
1
PUMPS
FRONT SPAR
ON
2
FRONT SPAR
P5-2
For Training Purposes Only
TANK 1 OR 2
FWD BOOST PUMP AND
CENTER TANK LEFT OR
RIGHT BOOST PUMP
FUEL LOW PRESSURE
SWITCH
C
SEE
FWD
C
(LEFT WING SHOWN, RIGHT WING OPPOSITE)
Figure 41
FRA US/E ur
Oct.96
Fuel Feed Low Pressure Indicating System
Page: 83
B737-300/400/500
28-70
FUEL FEED LOW PRESSURE INDICATING SYSTEM
Operation
Low pressure fuel from any boost pump in any tank will turn on a fuel feed low
pressure light. Low pressure from both fuel boost pumps in the same tank will
turn on the applicable low pressure lights and in addition, the fuel annunciator
light and the master caution lights will illuminate.
When the master caution light is pressed, the circuit is rearmed and the master
caution and fuel annunciator lights are extinguished. Pressing the fuel annunciator lights provided the low pressure condition remains (Ref Chapter 33 Master Warning and Caution Lights).
When the fuel in the center tank is depleted, the center tank boost pump low
pressure lights are illuminated. The low pressure lights for the center tank
boost pumps are extinguished when the boost pumps are turned off. The low
pressure lights for the No. 1 or 2 tank boost pumps are illuminated when low
fuel pressure exists or when the boost pumps are turned off.
For Training Purposes Only
Lufthansa Technical Training
FUEL
FUEL FEED LOW PRESS. IND. SYSTEM
FRA US/E ur
Feb. 2000
Page: 84
Lufthansa Technical Training
FUEL
FUEL FEED LOW PRESS. IND. SYSTEM
B737-300/400/500
28-70
P
A
6 PSIG
A
LOW PRESSURE LT TANK 1 FWD PUMP
33-15-20
MASTER
DIM & TEST
TANK 1 FWD LOW
PRESSURE SWITCH
P
A
115V AC
BUS
BOOST PUMP
TANK 1 FWD
28V DC
BUS
FUEL CONTROL
NO. 1 FWD NO. 2 AFT CTR R
6 PSIG
A
LOW PRESSURE LT TANK 1 AFT PUMP
TANK 1 FWD
BOOST PUMP
RELAY (P6)
33-15-20
MASTER
DIM & TEST
TANK 1 AFT LOW
PRESSURE SWITCH
OFF
ON
TANK 1 FWD
PUMP SW
115V AC
TRANS
BUS BOOST PUMP
TANK 1 AFT
OFF
ON
TANK 1 AFT
PUMP SW
TANK 1 AFT
BOOST PUMP
RELAY (P6)
OFF
P
15 PSIG
LEFT CENTER
TANK LOW
PRESSURE SWITCH
For Training Purposes Only
28V DC
BUS
FUEL CONTROL
NO. 1 AFT NO. 2 FWD CTR L
ON
CENTER
FUEL
TANK LEFT
SCAVENGE PUMP SW
SYSTEM
115V AC
BUS
BOOST PUMP
LEFT CTR
TANK
A
LEFT CTR BOOST
PUMP RELAY (P6)
A
LOW PRESSURE LT CENTER TANK LEFT PUMP
PANEL P6-3
Figure 42
FRA US/E ur
Feb. 2000
33-15-20
MASTER
DIM & TEST
P5-2 FUEL SYSTEM PANEL
Fuel Feed Low Pressure Indicating System Schematic
Page: 85
Lufthansa Technical Training
FUEL
FUEL TEMPERATURE IND. SYSTEM
B737-300/400/500
28-80
28-80
FUEL TEMPERATURE INDICATING SYSTEM
FUEL TEMPERATURE INDICATING SYSTEM
Purpose
The temperature indicator displays the fuel temperature in tank No. 1.
Location
The indicator is located on the P5 panel.
Physical Description
The fuel temperature indicator is resistance ratiometer-type unit. It consists of
a no-power sweep-off coil, deflection coil, cabin temperature compensator, dial
calibrated from -56°C to 56°C and integral lights.
Power
Power supply is 28 Volt AC.
For Training Purposes Only
Operation
The indicator rectifies the ac power to dc and applies it to the metering circuits
through an electromagnetic sweep-off mechanism. This forces the meter to
respond to the coil torques. The indicator applies a voltage to the temperature
bulb and the resulting current is a measure of the fuel temperature. With power
off, the pointer remains off scale at the low temperature end.
FRA US/E ur
Oct.96
Page: 86
Lufthansa Technical Training
FUEL
FUEL TEMPERATURE IND. SYSTEM
B737-300/400/500
28-80
FUEL VALVE
FUEL VALVE
CLOSED
CLOSED
B
-20
TANK NO. 1
0
FUEL
TEMP
-40
B
+20
FUEL TEMPERATURE
INDICATOR
+40
0C
FILTER
BYPASS
VALVE
OPEN
A
CROSS
FILTER
BYPASS
B
A
FEED
FORWARD OVERHEAD PANEL
FUEL
TEMPERATURE
BULB
WING REAR SPAR
FUEL TANK NO. 1
TEMPERATURE
BULB LEADS
TEMPERATURE BULB
LOCKING CAP
For Training Purposes Only
FUEL TEMPERATURE
BULB (SHOWN IN
INSTALLED POSITION BULB NOT VISIBLE)
Figure 43
FRA US/E ur
Oct.96
Fuel Temperature Indicating System
Page: 87