Message Name:

FUEL QUANTITY DASHED

The left, right or both fuel quantity indications replaced by magenta dashes indicates that the Fuel Quantity Gauging Computer (FQGC) is not able to carry out fuel quantity calculations or fuel quantities are not received or cannot be displayed by the Remote Data Concentrator (RDC).

• Fuel Computer System Unit (A57)
• Fuel Quantity Probe
• Remote Data Concentrator (RDC) Unit (A13)
• Water in Fuel Tank
• 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.
• Location of probe 10 (compensator) is attached to probe 8, there is no separate electrical identification for probe 10 as it is attached to probe 8 and identified as MT13 or MT14.
• The IPC 28-41 list the "PROBE, FUEL, COMPENSATOR, NO.8" and is identified as MT13 MT14
• The Left Wing Probe P8 and Compensator P10 (MT13) are combined together and shown in the Wire Manual with P8 aligned with pins 1-2-3 and P10 Compensator aligned with pins A-B-C.
• The Right Wing Probe P8 and Compensator P10 (MT14) are combined together and shown in the Wire manual with the P8 aligned with pins 1-2-3 an P10 Compensator aligned with pins A-B-C.
• 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
   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]B3-007128 - 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]B3-007690 - OPN/SHRT/OUT OF RANGE [R COLLECT 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]B3-648401 - 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.