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(WARNING)
RED MESSAGE (CAUTION)
AMBER MESSAGE (ADVISORY)
CYAN MESSAGE (STATUS)
WHITE MESSAGE Require immediate crew attention. These messages are accompanied by flashing master warning, triple chime attenson with or without voice message or dedicated tone. Require immediate crew awareness and future crew action may be required in the form of alternate system selection or performance limitation. These message are accompanied by flashing master caution and a single chime. Indicate safe or normal system operation which require crew awareness, over and above the dark cockpit philosophy. Indicate minor failures or reduction in systems capability, which require no crew action.

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07/14/23

Message Overview:

Message Name:

INTERNAL FAULT

Message Code:

B3-006789

Associated CAS:

FUEL QUANTITY FAIL
(Caution)

Reporting LRU: FQGC
System Description: 28-41-00
Schematic Diagram: 28-41-00
Wiring Diagram: 28-41-01

Message Description:

Both Fuel Quantity Gauging Computer (FQGC) channels have failed or water is present in at least 1 fuel quantity probe.

Possible Causes:

  • Fuel Quantity Gauging Computer (FQGC) (A57)
  • Right Fuel Quantity Probe (No.5) (MT10)
  • Water in Fuel Quantity Probe (MT10)
  • Remote Data Concentrator (RDC) (A13)
  • Input/Output Concentrator Unit (A4-IOC)
  • Associated Wiring

Troubleshooting Tips:

Advisory Wire/Service Bulletin:

  • AW300-28-0118 - No Fault Found Initiative: Fuel Quantity and Gauging Computer (FQGC)
  • AW300-28-0138 - Fuel Tank Sumping
  • SB 100-28-06 - Fuel management and quantity gauging system (FMQGS) - Replacement and Relocation of Fuel Quantity Probes No. 5, and Replacement of Fuel Quantity Probes No. 8 with Compensator to correct Gauging System Faults
  • AW300-28-0398 - SmartFix Plus Fuel System Troubleshooting Updates

Forum Articles/Infoservice/Newsletter: None

  • Because water has a higher dielectric constant than fuel, water in fuel tanks will affect the reading of fuel quantity probes if it comes in contact with them. The reading will become out of range and the FQGC will stop sending fuel quantity for that tank (magenta dashes). At a certain point, enough water in a fuel quantity probe will 'short' the probe's concentric tubes and collapse the oscillator signal feeding all probes for that tank. The FQGC will identify the oscillator as faulty and will shut down the affected tank channel and identify the fault as internal to the FQGC (MDC code B3-006789).
  • Before replacing the FQGC, make sure the failure is not caused by the presence of water in fuel probes.
  • When sumping water from affected fuel tank it is preferable to have fuel probes immersed in fuel, in order for the water to pool at the bottom of the fuel tank.
  • To get most of the water to the bottom of the tank, for T/S purposes do not move aircraft for at least 2 hours before sumping.

Fuel Probes Capacitance
Empty Tank Full Tank Out of Range
Probe Value pf Probe Value pf Value pf
1 29 1 53 <25.88 or >65.1
2 29.1 2 56.8 <25.88 or >65.1
3 29 3 56.8 <25.88 or >65.1
4 34.1 4 67.4 <30.83 or >77.16
5 40.8 5 80.1 <37.13 or >91.93
6 63.8 6 127.1 <58.66 or >146.01
7 59.7 7 118.4 <54.8 or >136.2
8 79.5 8 158.6 <72.94 or >181.43
9 63.7 9 126.9 <58.66 or >146.01
10 66 10 128.2 <121.39 or >138.42

Quick Links:

Pressure Refueling AMM 12-11-01-650-801
Suction Defueling AMM 12-11-09-650-801
Drain Water from the Fuel Tank AMM 28-10-00-680-801
Built-In Test of the Fuel-Quantity Gauging System AMM 28-41-00-740-801
Removal of the Fuel Quantity Computer AMM 28-41-01-000-801
Installation of the Fuel Quantity Computer AMM 28-41-01-400-801
Removal of the Fuel Quantity Probe AMM 28-41-13-000-801
Installation of the Fuel Quantity Probe AMM 28-41-13-400-801
Capacitance Check of the Fuel Quantity Probes AMM 28-41-13-760-801
Cleaning of the Fuel Quantity Probes AMM 28-41-13-160-801
Wiring - Maintenance Practices - ALL SPM 20-12-00-02
Wire Repair - Maintenance Practices - ALL SPM 20-12-10-02
Electrical Connectors - Maintenance Practice - ALL SPM 20-20-00-02

Troubleshooting Recommendations:

  1. Make sure Refuel/Defuel panel is set to OFF, reset the Fuel Quantity System breakers (CB3-C3, CB4-C3), waiting 10 seconds before pushing the breakers back.

    1. After 30 seconds, if the 'FUEL QTY FAIL' EICAS message disappears, no maintenance action is required, but it is recommended to sump fuel in both wing tanks and collector tanks in case water was the cause of the failure.
    2. If the 'FUEL QTY FAIL' EICAS message still displayed, go to next step.

  2. Sump at least 2 gallons of fuel from both wing tanks and collector tanks. If water is noticed in a tank, continue sumping until all water is removed.
  3. Make sure Refuel/Defuel panel is set to OFF, reset the Fuel Quantity System breakers (CB3-C3, CB4-C3), waiting 10 seconds before pushing the breakers back.

    1. After 30 seconds, if the 'FUEL QTY FAIL' EICAS message disappears, do close out.
    2. If the 'FUEL QTY FAIL' EICAS message still displayed, go to next step.

  4. Re-rack the Fuel Quantity Gauging Computer (FQGC). Is the fault message still present?

    1. If YES, go to next step.
    2. If NO, do close out.

  5. Defuel aircraft left and right wing tanks.
  6. Make sure Refuel/Defuel panel is set to OFF, reset the Fuel Quantity System breakers (CB3-C3, CB4-C3), waiting 10 seconds before pushing the breakers back.

    1. After 30 seconds, if the 'FUEL QTY FAIL' EICAS message disappears, do close out.
    2. If the 'FUEL QTY FAIL' EICAS message still displayed, go to next step.

  7. Verify MDC fault history for fuel probe faults. Any recent individual probe fault can indicate which fuel probe might have water in it.

    1. If a fuel probe fault if found in the MDC fault history, remove and clean the affected fuel probe.
    2. If fault continues, go to next step.

  8. Replace FQGC.
  9. If fault continues, replace Refuel/Defuel Panel.
  10. Do close out.

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