Message Name:

FAULTY FUEL INDICATION

The fuel quantity or temperature indication on the fuel synoptic page is erroneous or missing.

NOTE: The Fuel Quantity Computer (A57) processes fuel gauge and fuel level sensor signals to provide fuel quantity, temperature status and warning and failure condition information that is stored in a nonvolatile memory.

• After computation, the Fuel Quantity and Gauging Computer (FQGC) sent the fuel quantity information on ARINC 429 link to the Remote Data Concentrator (RDC), the RDC in turn sends this to the Data Concentrator Unit (DCU) for display on Engine Indicating and Crew Alerting System (EICAS).

• Fuel Probe
• Fuel System Computer Unit (A57)
• Associated Wiring

Advisory Wire/Service Bulletin:

• AW300-28-0118 - No Fault Found Initiative: Fuel Quantity and Gauging Computer (FQGC)
• AW300-28-0138 - Fuel Tank Sumping
• AW300-28-0398 - SmartFix Plus Fuel System Troubleshooting Updates

Full Throttle Blog/Forum Articles/Infoservice/Newsletter: None

Flight Operation Notifications Manual (FONM): None

NOTES:

• 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 contamination on 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.
• You can view and compare the Left wing and Right wing Fuel probe capacitance values via the MDC on the Fuel Probe Capacitance Display page. If one probe seems off compared to the other side, the affected probe may need to be cleaned.
• Fill the Detailed FQGC Troubleshooting Report if Fuel Quantity Gauging Computer (FQGC) pn 738360-1-2 is replaced.

1. Review the AWs and NOTEs in the Troubleshooting Tips prior to beginning the troubleshooting.
2. Select the active MDC fault or equation from the drop down below prior to following the troubleshooting below.
   Select the MDC Codes:B3-006788 - NO FQGC OUTPUT TO RDC [FQGC]B3-006789 - INTERNAL FAULT [FQGC]B3-006790 - NO L-GP-5 BUS INPUT [FQGC]B3-006791 - NO R-GP-5 BUS INPUT [FQGC]B3-006792 - WOFFW INPUT DISAGREE [FQGC]B3-006793 - NO FQGC-A BUS TO RDC [FQGC]B3-006794 - NO FQGC-B BUS TO RDC [FQGC]B3-006795 - AHC INPUT DISAGREE [FQGC]B3-007021 - OPN/SHRT/OUT OF RANGE [L COLLECT PROBE]B3-007114 - OPN/SHRT/OUT OF RANGE [L ENG OIL PROBE]B3-007128 - OPN/SHRT/OUT OF RANGE [L TNK PR 8/COMP]B3-007135 - OPN/SHRT/OUT OF RANGE [L TNK PROBE 1]B3-007136 - OPN/SHRT/OUT OF RANGE [L TNK PROBE 2]B3-007137 - OPN/SHRT/OUT OF RANGE [L TNK PROBE 3]B3-007138 - OPN/SHRT/OUT OF RANGE [L TNK PROBE 4]B3-007139 - OPN/SHRT/OUT OF RANGE [L TNK PROBE 5]B3-007140 - OPN/SHRT/OUT OF RANGE [L TNK PROBE 6]B3-007141 - OPN/SHRT/OUT OF RANGE [L TNK PROBE 7]B3-007142 - OPN/SHRT/OUT OF RANGE [L TNK HI LVL]B3-007690 - OPN/SHRT/OUT OF RANGE [R COLLECT PROBE]B3-007837 - OPN/SHRT/OUT OF RANGE [R ENG OIL PROBE]B3-007850 - OPN/SHRT/OUT OF RANGE [R TNK PR 8/COMP]B3-007857 - OPN/SHRT/OUT OF RANGE [R TNK PROBE 1]B3-007858 - OPN/SHRT/OUT OF RANGE [R TNK PROBE 2]B3-007859 - OPN/SHRT/OUT OF RANGE [R TNK PROBE 3]B3-007860 - OPN/SHRT/OUT OF RANGE [R TNK PROBE 4]B3-007861 - OPN/SHRT/OUT OF RANGE [R TNK PROBE 5]B3-007862 - OPN/SHRT/OUT OF RANGE [R TNK PROBE 6]B3-007863 - OPN/SHRT/OUT OF RANGE [R TNK PROBE 7]B3-007864 - OPN/SHRT/OUT OF RANGE [R TNK HI LVL]B3-648401 - IRS INPUT DISAGREE [FQGC]
   

   1. If any of the fault codes, listed on that page are present on the aircraft, troubleshoot these fault codes first.
   2. If none of the fault codes are present, continue with next step.

3. 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.
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. Access the fuel probe capacitance page on the MFD, check probe values are within the limits below:

   1. On the CCP L/R select switch to R
   2. Access the maintenance main menu by pushing the A/ICE, ECS and FUEL buttons simultaneously
   3. Using the joystick and ENTER button, select the LRU TEST
   4. Using the joystick and ENTER button, select FQGC
   5. Using the joystick and ENTER button, select TEST
   6. Using the joystick and ENTER button, select FUEL PROBES CAPACITANCE DISPLAY
      

6. Note the capacitance values for the respective side fuel probes and note the fuel quantity of each tank as it is displayed on the MDC.
   Fuel probe location diagram.
   
   The table below represents estimated pf values with temperatures around 27°C.

   Probe Designation (odd LH, even RH)	pf Dry (new)	0 lbs	2,000 lbs	4,000 lbs	8,000 lbs	10,390 lbs (full)	Out of Range	Result
   P1 (MT1/MT2)	28.4	29.1 ±1.5	28.8	28.8	28.8	28.8	<25.88 or >65.1
   P2 (MT3/MT4)	28.4	29.1 ±1.5	29	29	29	29	<25.88 or >65.1
   P3 (MT5/MT6)	28.4	29.1 ±1.5	28.9	28.9	28.9	33.7	<25.88 or >65.1
   P4 (MT7/MT8)	33.3	34.5 ±1.5	33.9	33.9	33.9	52.9	<30.83 or > 77.16
   P5 (MT9/MT10)	40	40.8 ±1.5	41.2	42.5	55.4	73.4	<37.13 or >91.93
   P6 (MT11/MT12)	62.9	63.7 ±1.5	70.1	79.9	95.7	116.4	<58.66 or >146.01
   P7 (MT17/MT18)	58.8	59.7 ±1.5	81.4	98.3	119.6	119.6	<54.8 or >136.2
   P8 (MT13/MT14)	78.1	79.1 ±1.5	106.5	123.4	160.1	153.3	<72.94 or >181.43
   P9 (MT107/MT108)	62.9	63.7 ±1.5	98	118.5	128.2	128.2	<58.66 or >146.01
   P10	64.1*	64.19 ±2*	129.3	129.3	129.4	129.4	<121.39 or >138.42*

   *Capacitance range values are nominal only when the fuel probe is immersed in fuel.

   1. If the fuel probe capacitance is out of range, there is a possibility of water contamination inside the fuel system, drain water from the fuel tank. A fuel sampler is required to drain the water from the tank.
   2. If probe readings are still out of tolerance, before replacement attempt to clean the fuel probe. The affected fuel tank may need to be treated with biocide if contamination is found. Refer to AW300-28-0138.
      

7. Replace the Fuel Quantity Gauging Computer (FQGC) (A57).
8. Do close out.