W DOC AIRBUS | TSM A320F

APU AUTO SHUTDOWN - UNDERSPEED, Fuel Flow disagrees with Command (131-9(A))

TASK 49-00-81-810-806-A
APU AUTO SHUTDOWN - UNDERSPEED, Fuel Flow disagrees with Command (131-9(A))

1. Possible Causes
  • FUEL FLOW DISAGREES WITH COMMAND
  • damage/contamination of electrical connector P19
  • FUEL CONTROL UNIT (P19)
  • aircraft wiring
  • ELECTRONIC CONTROL BOX [59KD]
  • FUEL CONTROL UNIT (8022KM)
2. Job Set-up Information
 A. Fixtures, Tools, Test and Support Equipment
REFERENCE
QTY
DESIGNATION
No specific
AR
MULTIMETER - STANDARD
 B. Referenced Information
REFERENCE
DESIGNATION
AMM 49-00-00-860-008
APU Start by External Power
AMM 49-32-11-000-003
Removal of the Fuel Control Unit (FCU) (131-9(A))
AMM 49-32-11-400-003
Installation of the Fuel Control Unit (FCU) (131-9(A))
ASM 496104
AMM 49-61-34-000-003
Removal of the Electronic Control Box (ECB) (131-9(A))
AMM 49-61-34-400-003
Installation of the Electronic Control Box (ECB) (131-9(A))
3. Fault Confirmation
Subtask 49-00-81-710-098-A ** ON A/C NOT FOR ALL
A. Read-out of ECB Trouble-Shooting Data
   (1) Put the APU MASTER SW to the ON position.
   (2) Get access to the APU SHUTDOWN report.
   (3) Push the '>' adjacent to LRU DATA:
  • the MCDU menu shows
    FUEL FLOW DISAGREES WITH COMMAND
   (4) Start the APU and apply Bleed Air for 20 seconds, minimum AMM 49-00-00-860-008.
4. Fault Isolation
Subtask 49-00-81-810-080-A ** ON A/C NOT FOR ALL
A. If an APU auto shutdown occurs during the APU operation and the APU SHUTDOWN report gives the maintenance message:

UNDERPEED
FUEL CONTROL UNIT P19/APU FUEL SUPPLY

associated with Fault Code Number (FCN) 79

  • do a check for damage/contamination of electrical connector P19 of the FUEL CONTROL UNIT (P19)
   (1) If the electrical connector P19 is damaged/contaminated:
  • do a repair/cleaning.
   (2) If the electrical connector is OK:
  • use a MULTIMETER - STANDARD to do a resistance check across pin 6 and pin 7 of the FUEL CONTROL UNIT (P19).
     (a) If the resistance value is not between 31 Ohms and 41 Ohms:
     (b) If the resistance value is in the specified limit:
  • do a check and repair of the aircraft wiring from the ECB (59KD) AB/H11,G7 to the FUEL CONTROL UNIT (P19) P19/6,7 ASM 496104.
       1 If the fault continues:
Subtask 49-00-81-810-080-B ** ON A/C NOT FOR ALL
A. If an APU auto shutdown occurs during the APU operation and the APU SHUTDOWN report gives the maintenance message:

UNDERPEED
FUEL CTRL UNIT(8022KM) / APU FUEL SUPPLY

associated with Fault Code Number (FCN) 79

  • do a check for damage/contamination of electrical connector P19 of the FUEL CONTROL UNIT (8022KM)
   (1) If the electrical connector P19 is damaged/contaminated:
  • do a repair/cleaning.
   (2) If the electrical connector is OK:
  • use a MULTIMETER - STANDARD to do a resistance check across pin 6 and pin 7 of the FUEL CONTROL UNIT (8022KM)
     (a) If the resistance value is not between 31 Ohms and 41 Ohms:
     (b) If the resistance value is in the specified limit:
  • do a check and repair of the aircraft wiring from the ECB (59KD) AB/H11,G7 to the FUEL CONTROL UNIT (8022KM) P19/6,7 ASM 496104.
       1 If the fault continues:
Subtask 49-00-81-710-099-A ** ON A/C NOT FOR ALL
B. Do the test given in Para. 3.
[Rev.8 from Aug 2018] 2026.04.04 04:34:32 UTC
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