07/14/23
Message Overview:
Message Description:
The FQGC has detected a discrepancy between the Attitude Heading Computer (AHC) inputs, leading to degraded fuel quantity accuracy. The fault will automatically clear if the discrepancy is resolved.
Possible Causes:
- Attitude Heading Computer (AHC) (A11)
- Fuel Quantity Gauging Computer (FQGC) (A57)
- Left Input/Output Concentrator (IOC) 1 (A4-IOC1)
- Right Input/Output Concentrator (IOC) 2 (A4-IOC2)
- Associated Wiring
Troubleshooting Tips:
Advisory Wire/Service Bulletin: None
Forum Articles/Infoservice/Newsletter: None
- The FQGC uses Attitude and Heading Reference System (AHRS) inputs to compensate for fuel movement in the wing tanks due to pitch and roll changes. If a discrepancy between the AHRS 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 Remote Data Concentrator (RDC) | AMM 31-41-05-000-802 |
| Installation of the Remote Data Concentrator (RDC) | AMM 31-41-05-400-802 |
| Removal of the Attitude Heading Computer (AHC) | AMM 34-21-01-000-801 |
| Installation of the Attitude Heading Computer (AHC) | AMM 34-21-01-400-801 |
| Operational Test of the Attitude Heading Computer (AHC) | AMM 34-21-01-710-801 |
| 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' fault related to pitch and/or roll is present or has been recorded at the time of the fault.
- If an 'EFIS MISCOMPARE' fault is found, 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 (ATT HDG 1) and CB2-C2 (ATT HDG 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 Fuel Quantity Gauging Computer (FQGC).
- Do close out.
