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FUEL - FOB BELOW 3 T Memo Message Shown Permanently

TASK 28-46-00-810-847-A
FUEL - FOB BELOW 3 T Memo Message Shown Permanently

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 28-46-00-865-052-A ** ON A/C NOT FOR ALL
A. Table of the circuit breakers used in this procedure:
PANELDESIGNATIONFINLOCATION
** ON A/C NOT FOR ALL
49VUSDAC/1/SPLY3WVF04
121VUEIS/SDAC/2/SPLY2WVQ06
Subtask 28-46-00-710-078-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 both the wing tank FQIs show more than approximately 1500kg (3300lb) when the FOB BELOW 3 T memo message is not given:
  • no maintenance steps are necessary.
4. Fault Isolation
Subtask 28-46-00-810-096-A ** ON A/C NOT FOR ALL
A. If the two wing tank FQIs show more than approximately 1500kg (3300lb) when the FOB BELOW 3 T memo message is 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 1 = wet):
     (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 any of the above bit positions in 4.A.(6)(a) and 4.A.(6)(b):
     (a) Show a 0, (when the sensors are wet):
  • Go to the CFDS, or the Table of Contents and do the applicable troubleshooting procedure.
   (8) If all above bit positions show a 1, (the sensors are wet), and the fault continues:
     (a) Remove the two 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:
     (a) Not given:
       1 Install one FLSCU AMM 28-46-34-400-001 at a time and then apply power to the system/aircraft:
       2 Replace the FLSCU-1 [7QJ] 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 to be given.
     (b) Given:
       1 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.
   (10) Repair all the unserviceable wiring and connectors.
   (11) If the fault continues:
  • open the C/Bs 3WV (SDAC1) and 2WV (SDAC2) in turn:
   (12) If the fault is displayed on one powered/active SDAC:
  • interchange the SDACs to confirm the faulty LRU.
   (13) Check/replace the SDAC-1 [1WV1] or SDAC-2 [1WV2] , AMM 31-55-34-000-001 and AMM 31-55-34-400-001, that cause(s) the false FOB BELOW 3 T memo message 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 giving a false memo message as shown in the table below.
---------------------------------------------------------------------------
! 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
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