FUEL - FOB BELOW 3 T Memo Message Not Shown

TASK 28-46-00-810-846-A
FUEL - FOB BELOW 3 T Memo Message Not Shown

WARNING: OBEY THE FUEL SAFETY PROCEDURES.

WARNING: WHEN YOU DO WORK ON THE FUEL SYSTEM WIRING, YOU MUST USE TEST EQUIPMENT THAT IS APPROVED (REFER TO INTERNATIONAL OR NATIONAL SPECIFICATIONS FOR INTRINSICALLY SAFE TEST EQUIPMENT: EN50020, UL913 OR EQUIVALENT). TEST EQUIPMENT THAT IS NOT APPROVED CAN CAUSE FIRE OR AN EXPLOSION.

1. Possible Causes

FLSCU-1 [7QJ]
FLSCU-2 [9QJ]
aircraft wiring
SDAC-1 [1WV1]
SDAC-2 [1WV2]

2. Job Set-up Information
A. Referenced Information

REFERENCE	DESIGNATION
AMM 28-46-00-740-001	Functional (BITE) Test
ASM 284602
AMM 28-46-34-000-001	Removal of the Fuel-Level Sensing Control-Unit (FLSCU)
AMM 28-46-34-400-001	Installation of the Fuel-Level Sensing Control-Unit (FLSCU)
AMM 31-55-34-000-001	Removal of the SDAC
AMM 31-55-34-400-001	Installation of the SDAC

3. Fault Confirmation
Subtask 28-46-00-865-051-A ** ON A/C NOT FOR ALL

A. Table of the circuit breakers used in this procedure:

PANEL	DESIGNATION	FIN	LOCATION
** ON A/C NOT FOR ALL
49VU	SDAC/1/SPLY	3WV	F04
121VU	EIS/SDAC/2/SPLY	2WV	Q06

Subtask 28-46-00-710-077-A ** ON A/C NOT FOR ALL

B. During normal operation of the FLSS/FWC/DMC this is a configuration memo.
If in either wing tank a pair of low level sensors that are AND gated together become dry indicating a fuel level of less than approximately 1500kg (3300lb) the memo message is given.
It is not a warning of a system/LRU failure or malfunction.

However, if the low level warning system is under suspicion:
(1) On the ECAM CONTROL PANEL push (in) the FUEL P/BSW.
(2) On the FUEL System Display (Lower ECAM) examine the wing tank FQIs.
(3) If either the wing tank FQI shows less than approximately 1500kg (3300lb) when the FOB BELOW 3 T memo message is given:

no maintenance steps are necessary.

4. Fault Isolation
Subtask 28-46-00-810-095-A ** ON A/C NOT FOR ALL

A. If either wing tank FQI shows less than approximately 1500kg (3300lb) and the FOB BELOW 3 T memo message is not given:
(1) Do the BITE test of the FLSS AMM 28-46-00-740-001.
(2) If failures are detected examine the FLSS STATUS page for any of the messages that follow:

L(R) LO LEVEL SENSOR 15QJ1(2)
L(R) LO LEVEL SENSOR 40QJ1(2)
FLSCU1 7QJ
FLSCU2 9QJ.

(3) If none of the above messages are shown:

go to step (5).

(4) If one or more of the messages identified in Para 4.A.(2) are shown:

trouble shoot the LRU(s) before you start more steps.
Refer to CFDS and do the applicable troubleshooting procedure.

(5) On the MCDU set to:
(a) CFDS.
(b) SYSTEM REPORT/TEST.
(c) FUEL.
(d) INPUT PARAMETER VALUES page 3, the FQIS DISCRETE INPUTS.
(6) Examine the bit positions as follows (a 0 = dry):
(a) For the left wing:

E4 (15QJ1-LS5/FLSCU2)
H3 (40QJ1-LS8/FLSCU1).

(b) For the right wing:

E3 (15QJ2-LS5/FLSCU1)
H4 (40QJ2-LS8/FLSCU2).

NOTE: The Fuel Level Sensors Operating (Changeover) Values can be got from P. Block 301.

(7) If both of the above bit positions in 4.A.(6)(a) or 4.A.(6)(b):
(a) Show a 1, (when the sensors are dry):

Go to the CFDS, or the Table of Contents and do the applicable troubleshooting procedure.

(8) If both the bit positions in 4.A.(6)(a) or 4.A.(6)(b) show a 0, (the sensors are dry), and the fault continues:
(a) Remove both FLSCUs from the rack AMM 28-46-34-000-001.
(b) Apply power to the system/aircraft.
(9) If the FOB BELOW 3 T memo message is:

not given:

(10) Install one FLSCU AMM 28-46-34-400-001 at a time and then apply power to the system/aircraft:
(11) Replace the FLSCU-1 [7QJ] and/or FLSCU-2 [9QJ] , AMM 28-46-34-000-001 and AMM 28-46-34-400-001 that causes the FOB BELOW 3 T memo message not to be given.
(12) If the fault continues do a check of the aircraft wiring ASM 284602, between:

the FLSCU-1 rack connector AA pin 10B and the SDAC 1 connector AD pin 4F
the FLSCU-1 rack connector AA pin 10B and the SDAC 2 connector AD pin 4F
the FLSCU-2 rack connector AA pin 10B and the SDAC 1 connector AA pin 4D
the FLSCU-2 rack connector AA pin 10B and the SDAC 2 connector AA pin 4D
the FLSCU-1 rack connector AA pin 4C and the FLSCU-2 rack connector AA pin 9B
the FLSCU-1 rack connector AA pin 9B and the FLSCU-2 rack connector AA pin 4C.

(13) Repair all the unserviceable wiring and connectors.
(14) If the fault continues:

open the C/Bs 3WV (SDAC1) and 2WV (SDAC2) in turn:

(15) If the fault is displayed on one powered/active SDAC:

interchange the SDACs to confirm the faulty LRU.

(16) Check/replace the SDAC-1 [1WV1] or SDAC-2 [1WV2] , AMM 31-55-34-000-001 and AMM 31-55-34-400-001, that causes the FOB BELOW 3 T memo message not to be given:

NOTE: When AIDS is installed in the aircraft, the AIDS PARA LABEL CALL-UP Menu option can be used to identify which SDAC is not giving a memo message as shown in the table that follows.

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! PARA LABEL CALL-UP ! SIGNAL DISCRIPTION !

!---------------------------------! (LO LEVEL CHANs identified below !

! EQ ! SYS ! LAB ! SDI ! DATABITS ! refer to 1500kg/3300lb) !

!----!-----!-----!-----!----------!-----------------------------------------!

! 29 ! 1 ! 001 ! 01 ! 29 ! L WING TK LO LEVEL CHAN B FROM SDAC 1 !

! 29 ! 1 ! 001 ! 00 ! 29 ! R WING TK LO LEVEL CHAN B FROM SDAC 1 !

! 29 ! 2 ! 001 ! 01 ! 29 ! L WING TK LO LEVEL CHAN B FROM SDAC 2 !

! 29 ! 2 ! 001 ! 00 ! 29 ! R WING TK LO LEVEL CHAN B FROM SDAC 2 !

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[Rev.8 from Aug 2018] 2026.04.04 04:29:18 UTC