07/18/23
Message Overview:
Message Description:
FQGC has detected an incoherence in IRS inputs leading to a fuel quantity degraded accuracy.
Possible Causes:
- R Inertial Reference Unit (IRU) 2 (A232)
- L Inertial Reference Unit (IRU) 1 (A233)
- Fuel Quantity Gauging Computer (FQGC) (A57)
- Left Input/Output Concentrator 1 (IOC) (A4-IOC1)
- Right Input/Output Concentrator 2 (IOC) (A4-IOC2)
- Associated Wiring
Troubleshooting Tips:
Advisory Wire/Service Bulletin:
- AW300-28-0398 - SmartFix Plus Fuel System Troubleshooting Updates
- AW300-28-0138 - Fuel tank sumping
Forum Articles/Infoservice/Newsletter: None
- The FQGC uses Inertial Reference System (IRS) inputs to compensate for fuel movement in the wing tanks due to pitch and roll changes. If a discrepancy between the IRS inputs is detected, The FQGC will use default values for its calculations (degraded mode), but the fuel quantity indication on the fuel synoptic page will remain white.
- Note that a Pitch of over -20 degrees or +40 degrees and/or a roll of over ±15 degrees maintained for more than 1 minute will trigger this fault. In this case, the fault may be ignored.
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 Input/Output Concentrator Unit (IOC) | AMM 31-45-05-000-801 |
| Installation of the Input/Output Concentrator Unit (IOC) | AMM 31-45-05-400-801 |
| Operational Test of the Input/Output Concentrator Unit (IOC) | AMM 31-45-05-710-801 |
| Operational Test of the Inertial Reference System (IRS) | AMM 34-45-00-710-801 |
| Removal of the Inertial Reference Unit (IRU) | AMM 34-45-01-000-801 |
| Installation of the Inertial Reference Unit (IRU) | AMM 34-45-01-400-801 |
| 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:
- Verify if an 'EFIS MISCOMPARE' or any IRS related fault is present or has been recorded at the time of the fault.
- If an 'EFIS MISCOMPARE' or IRS related fault, troubleshoot accordingly before addressing the FQGC fault.
- If not, go to next step.
- Make sure the Refuel/Defuel panel is set to OFF and reset CB3-C3 (FUEL QTY 1), CB4-C3 (FUEL QTY 2), CB1-C2 (IRU 1) and CB2-C2 (IRU 2), waiting 10 seconds before pushing the breakers back.
- Wait 5 minutes. If the fault is triggered, go to next step.
- Re-rack the Fuel Quantity Gauging Computer (FQGC). Is the fault message still present?
- If YES, go to next step.
- If NO, do close out.
- Replace the Fuel Quantity Gauging Computer (FQGC).
- Do close out.
