Fuel Quantity Indication Computer (FQIC) A320
WARNING: OBEY THE FUEL SAFETY PROCEDURES.
WARNING: WHEN YOU DO WORK ON THE FUEL SYSTEM WIRING, YOU MUST USE TEST EQUIPMENT THAT IS APPROVED (REFER TO INTERNATIONAL OR NATIONAL SPECIFICATIONS FOR INTRINSICALLY SAFE TEST EQUIPMENT: EN60079, UL913 OR EQUIVALENT). TEST EQUIPMENT THAT IS NOT APPROVED CAN CAUSE FIRE OR AN EXPLOSION.
1. Possible Causes:
-FQIC (3QT)
-water contamination
-microbiological contamination
-FQIS fuel tank harness
-fused/shorting plug connector
-fuel probe
2. Job Set-up Information
A. Referenced Information
| REFERENCE | DESIGNATION |
| Ref. 28-42-00-810-807-A | Fuel Quantity/CIC Probe 24QT1(2), Left(Right) Wing Tank |
| Ref. 28-42-00-810-822-A | Fuel Quantity/CIC Probe 39QT, Center Tank |
| Ref. 28-42-00-810-848-A | FQIS — Attitude Data From the ADIRUs is Possibly Incorrect |
| Ref. 28-42-00-810-874-A | FQIS and ECAM FQIs Fluctuate When ADIRS is set to off |
| Ref. 28-42-00-810-875-A | FQIs Degraded, Malfunction in a W/Tank when Fused Connector Plugs are Installed An Alternative Task for the Connector Plug Only and Caused by Moisture Ingress |
| Ref. 28-42-00-810-879-A | The Fuel Quantity Indications Go Inoperative Or Degraded Associated With Multiple Fuel Probe Failures Due To Water & Microbiological Contamination |
| Ref. AMM 12-32-28-281-001 | Drain Water Content |
| Ref. AMM 12-32-28-281-003 | Sample Fuel for Microbiological Contamination Analysis |
| Ref. ESPM 20-53-21 | |
| Ref. AMM 24-41-00-861-002 | Energize the Aircraft Electrical Circuits from the External Power |
| Ref. AMM 28-11-00-600-003 | Removal of the Microbiological Particles |
| Ref. AMM 28-42-00-740-003 | Interrogation of the FQIS Input Parameters Pages |
| Ref. AMM 28-42-00-740-007 | Interrogation of the (SMITHS INDUSTRIES) FQIS Troubleshooting Data |
| Ref. AMM 28-42-34-000-001 | Removal of the Fuel Quantity-Indicating Computer (FQIC) |
| Ref. AMM 28-42-34-400-001 | Installation of the Fuel Quantity-Indicating Computer (FQIC) |
| Ref. AMM 28-42-43-000-008 | Removal of the Wing Tank Fuel Quantity Indicating Probe Fused/Shorting Plug Connectors |
| Ref. AMM 28-42-43-400-008 | Installation of the Wing Tank Fuel Quantity Indicating Probe Fused/Shorting Plug Connectors |
| Ref. AMM 31-32-00-860-001 | Procedure to Get Access to the SYSTEM REPORT/TEST Menu Page |
| Ref. AMM 31-60-00-860-001 | EIS Start Procedure |
| Ref. AMM 34-10-00-860-005 | ADIRS Stop Procedure |
| Ref. 28-42-00-03 | QUANTITY INDICATING — TASK SUPPORTING DATA |
3. Fault Confirmation
SUBTASK 28-42-00-865-050-A
A. Table of the circuit breakers used in this procedure:
| PANEL | DESIGNATION | FIN | LOCATION |
| 49VU | FUEL/FQI/CHAN/1 | 1QT | A13 |
| 121VU | FUEL/FQI/CHAN/2 | 2QT | M27 |
SUBTASK 28-42-00-710-050-D
B. Test
NOTE: The FQIS is a negative DC capacitive system. In such a system the fuel probes (which are the sensors) operate as capacitors. The dielectric of the capacitors is:
— fuel if a fuel probe is covered with fuel
— air if a fuel probe is not covered with fuel.
Each fuel probe operates as a variable capacitor with a capacitance value related to the ratio of the fuel probe covered in air or fuel. This is because the permittivity of the fuel is approximately two times that of air. Thus the fuel is a component part of the electrical FQIS.
If water (and/or other unwanted materials) gets into a fuel-tank, it can cause problems. Example, it can cause a partial or a complete short circuit between the two concentric tubes of the fuel probe.
The theory of operation given above is not applicable to the density section of the cadensicons. This operates by electromagnetic induction and the sensor (detector) is a transformer whose transformation ratio is proportional to its core position. The position of the core is controlled by a float. The position of which is proportional to the density of the adjacent fuel.
It is very important that the water in each fuel tank is kept to a minimum. The procedures given in the MPD, AMM must be fully completed. A failure to do so can cause the problems that follow:
— water contamination
— microbiological contamination
— chemical contamination
— local fuel-tank corrosion
— engine corrosion
— the engine fuel filters to become blocked
— the aircraft is out of service for a long period some time in the future while the microbiological contamination is removed
— possible aircraft safety issues.
(1) If you are:
— not sure that the AMM refuel and all the MPD scheduled servicing tasks (related to water and microbiological contamination of the fuel) have been correctly done, do the TSM procedure Ref. TSM TASK 28-42-00-810-879
— sure that the AMM refuel and all the MPD scheduled servicing tasks (related to water and microbiological contamination of the fuel) have been correctly done, do step (2).
(2) It has been identified that with FQIC Part No. SIC5059-13-10 an occasional mis-read of analogue data can result. The effect of the mis-read data is to cause an analogue signal to go beyond its BITE limits. Due to the mis-read of the analogue data it is possible that during normal airline service the FQIC will exhibit spurious FQIC 3QT fault logs (FUEL QUANTITY FQIC 3QT) on the maintenance CFDS display unit.
All FQIC 3QT faults reported (other than a FQIC 3QT fault shown with a related FQIC troubleshooting fault code 6J) which have no associated degradation of fuel gauging or temperature measurement should initially be thought of as an error and no maintenance action taken. If the fault is present on the next flight, the applicable maintenance action should be done. If the fault is not present on the next flight, then this makes sure that the fault during the previous flight (LEG) was an error (spurious).
It is recommended to troubleshoot the fault that follows because it can be correct (real) and not spurious:
— FAILURE MESSAGE — FUEL QUANTITY FQIC 3QT
— related FQIC troubleshooting data fault code — 6J
— and/or FAILURE MESSAGE — FWC2: NO DATA FROM FQI2A/2B
— flight crew OBS — it is not possible to initialize GW on the FMGC-2 automatically
— flight crew OBS — FMS1/FMS2 GW DIFF message given on the captains MCDU.
(3) If the FQIC 3QT is reported, without the associated degradation of the fuel quantity or temperature measurement:
— at the first time, do step (4)
— at the subsequent flight, or LEG, or as given in step (2), do step (5).
(4) If the FQIC 3QT is reported, without associated degradation:
(a) Make a record of this in the aircraft technical log.
(b) No more maintenance work is necessary.
(5) To keep the number of computer removals and replacements to a minimum do the Power-on BITE test of the FQI system as follows:
(a) If the FQIS is not energized:
1 Close the C/Bs 1QT and 2QT.
2 Energize the Aircraft Electrical Circuits from the External Power Ref. AMM 24-41-00-861-002.
(b) If the FQIS is energized, reset the FQIC as follows:
1 Open the C/Bs 1QT and 2QT.
2 Wait 5 seconds.
3 Close the C/Bs 1QT and 2QT.
NOTE: For the FQIC to do a (new) power-on BITE test, a power supply interrupt (interval) of more than 5 seconds is necessary. This gives the current status of the FQIS/FLSS components.
(6) Do the EIS Start Procedure (ECAM only) Ref. AMM 31-60-00-860-001.
(7) Make sure that the ADIRS is set to OFF. If necessary, do the ADIRS stop procedure Ref. AMM 34-10-00-860-005.
NOTE: This step is important if this procedure is being used to trouble shoot a FQI display (ECAM and FQIS) fluctuation problem. It will disconnect the external acceleration inputs that are used to give pitch and roll.
(8) On the ECAM control panel, push (in) the FUEL P/BSW.
(9) Make sure that the FUEL page shows on the ECAM lower display unit.
(10) Wait 60 seconds.
(11) Continue as follows:
NOTE: The FUEL page FQIs will show XXs in amber color for 35 seconds during the FQIC power-on BITE test and the intercell transfer valves can be seen to move.
(a) Do the procedure to get access to the SYSTEM REPORT/TEST menu page Ref. AMM 31-32-00-860-001.
(b) When the SYSTEM REPORT/TEST menu page comes into view, push the line key adjacent to FUEL.
(c) When the FUEL menu page 1 comes into view, push the NEXT PAGE key on the MCDU keyboard to see the FUEL menu page 2.
NOTE: If a menu has more than one page (shown by the more to come symbol > on the top line, right side of the MCDU display) each operation of the NEXT PAGE key on the MCDU keyboard will cause the next page to be shown. When the last page of any menu is shown, operation of the NEXT PAGE key will cause the first page to be shown.
(d) When the FUEL menu page 2 comes into view, push the line key adjacent to FQIS STATUS.
(12) Examine the FQIS STATUS page.
(a) Make a record of the messages shown (or use the PRINT function to get a copy).
1 If the FQIS STATUS page shows the message FQIC 3QT, press the function/line key (to the right of that message) to see the FQIC TROUBLE SHOOTING data Ref. AMM 28-42-00-740-007.
2 Make a record of the troubleshooting data shown (or use the PRINT function to get a copy).
(b) When you have got your copies or print(s), press the RETURN key on the MCDU (as applicable) and return to the FUEL menu page 2.
(c) When the FUEL menu page 2 comes into view, push the line key adjacent to INPUT PARAMETER VALUES.
(13) Examine the INPUT PARAMETER VALUES (page 1 — FQIS INPUT PARAMETERS).
(a) Make a record of the page 1 (or use the PRINT function to get a copy).
(b) When you have got a copy or print, press the NEXT PAGE key on the MCDU.
(14) Examine the INPUT PARAMETERS (page 2 — FQIS PROBE CAPACITANCES).
(a) Make a record of the page 2 (or use the PRINT function to get a copy).
(b) Put a mark on each of your records (PRINTS) to identify them as from the FQIC 3QT that gave the original fault (message).
(15) Monitor the FQIs on the ECAM FUEL page and the FQIS indicators.
(16) Compare the original failure, the FQI indications and your records with those that follow:
— if the FQI goes inoperative or degraded and is associated with multiple fuel probe failures, do the TSM procedure Ref. TSM TASK 28-42-00-810-879
— if multiple fuel probe messages are given on the FQIS STATUS page with multiple values on the I/P PARAMETER page 1 and page 2 (shown with an * (asterisk) or a X), do the procedure Ref. TSM TASK 28-42-00-810-879
— if the FQIC 3QT message is shown, or the FQIC 3QT message and other FQIS probe messages are shown, go to Para. 4.A.
— if only FQIS probe messages are shown (and the related values given on the I/P PARAMETER page 1 and 2 are shown with an * (asterisk) or a X), trouble-shoot the identified LRU(s), refer to step (17)
— if no FQIS messages are shown, but the FQIs are seen to fluctuate (vary/change over a period of time), do the TSM procedures, FQIS and ECAM FQIs Fluctuate When ADIRS is set to off Ref. TSM TASK 28-42-00-810-874, and Attitude Data From the ADIRUs is Possibly Incorrect Ref. TSM TASK 28-42-00-810-848
— if no messages are shown, the values given on the I/P PARAMETER pages are shown correctly related to the fuel levels in the tanks and the FQI indications are stable, no trouble shooting work steps are necessary.
NOTE: In normal operation the FQI indicators (FQIS and ECAM, FOB and each tank) can increase or decrease by 10 kg/20 lb (which is one unit of the display resolution). If a tank value increases or decreases by 10 kg/20 lb, the total (FOB) will increase or decrease by the same amount.
NOTE: The (serviceable and unserviceable) input parameter display values shown on the pages 1 and 2 are given in the AMM procedure Ref. AMM 28-42-00-740-003.
(17) Refer to the TSM list of CFDS Fault Messages for the applicable Fault Isolation Task number(s).
4. Fault Isolation
SUBTASK 28-42-00-810-050-C
A. Procedure
(1) Temporarily replace the FQIC 3QT with a serviceable item Ref. AMM 28-42-34-000-001 and Ref. AMM 28-42-34-400-001.
NOTE: The step (1) has been included because it is important to make sure that the FQIC 3QT is the cause of the malfunction before you start more steps.
Make sure that the FQIC 3QT to be installed is of the same type as that removed.
(a) Do the test given in Para. 3.B.
(b) Put a mark on the new records/PRINTS to identify them as from the temporary installed serviceable FQIC 3QT.
(2) If the message FQIC 3QT:
— is not shown (and the related input parameter values show correct), complete the installation of the replacement FQIC (3QT) Ref. AMM 28-42-34-000-001 and Ref. AMM 28-42-34-400-001
— is shown (and the related input parameter values stay incorrect), do step (3).
(3) Remove the temporary installed FQIC 3QT Ref. AMM 28-42-34-000-001 and return it to stores.
(4) Install the initial FQIC 3QT Ref. AMM 28-42-34-400-001.
(a) Do the test given in Para. 3.B.
(5) If the fault continues:
(a) Get the records/PRINTS of the troubleshooting data and the FQIS input parameters pages you got from the MCDU before/above.
(b) From the troubleshooting data get the location (alpha/numerical position) — GRID REF that is set to a 1 (one).
1 From the FQIC Trouble Shooting Data List Ref. AMM 28-42-00-740-007 read off the failure type for that GRID REF location.
(c) Examine all of the records/PRINTS and look for an item or a value(s) (any) that can cause the malfunction, for example:
— compare fuel probe parameters (values — CAD K, DENS, CIC K, INNTEMP, OUTTEMP,PITCH F and ROLL F) with the others given on page 1 for similarity of the fuel conditions and ambient temperatures
— compare fuel probe capacitance values with the value of the same probe in the opposite wing or group
— look for blank indications (of related capacitance values) for a harness group.
(d) If (on the parameter page 1) the PITCH shows A and and the ROLL shows A:
1 Set the ADIRS to OFF.
2 Go (return) to Para. 3.B. and do the test again.
NOTE: An A, after PITCH and ROLL, shows that the pitch and roll inputs are from the ADIRS. To eliminate the external pitch and roll inputs as the possible cause of the FQI fluctuations, the ADIRS must be set to OFF.
An F, after PITCH and ROLL, shows that the pitch and roll has been made by the FQIS internally.
(e) If necessary, monitor the FQIS input parameters pages at the MCDU screen live. Look for an abnormal value, an intermittent value or one that is seen to have unexplained fluctuations.
NOTE: The FQIS input parameter pages are not automatically updated.
To see the operation of the fuel system via the CFDS (FUEL), Input Parameter pages in real time the pages must be continually updated. Use the NEXT PAGE control on the MCDU to cycle the pages to update the screen. If this procedure is not used/adopted the pages will remain as they were at the time of the page (menu option) selection.
(f) Make an analysis from the input parameter, the troubleshooting data and from the MCDU screen direct in step (5)(e).
(g) If the analysis:
— gives/shows you a fault symptom, go to the TSM Fault Symptoms list for the related Task number
— does not give you a fault symptom, do the steps that follow.
(6) If the fault continues:
(a) Do a check for water contamination as given in the procedure ‘Drain Water Content’ Ref. AMM 12-32-28-281-001.
(b) Do a check (sample) for microbiological contamination Ref. AMM 12-32-28-281-003. If the results are MODERATE or HEAVY, do the applicable procedure or action Ref. AMM 28-11-00-600-003.
NOTE: Different microbiological contamination test kits are available. If no water is present in the drained sample, it is important to use a kit which can test contamination in the fuel phase. It is also important you make sure you use a kit which is correct for the timescale for the results availability.
(7) If one or more fuel probe value(s) is/are not what you would expect, do troubleshooting on the applicable LRU(s).
NOTE: The normal range of fuel probe capacitance values is given in Ref. TSM 28-42-00-03.
NOTE: A fuel probe can fail and stay in its range and/or not be reported on the FQIS STATUS page.
(a) Do the test given in Para. 3.B.
(8) If the capacitance values of related fuel probe LRUs (attached to a FQIS fuel tank harness) are shown blank, fluctuate or are outside the range of a similar group:
(a) Do a check of the related fused/shorting plug connector and replace, if necessary Ref. AMM 28-42-43-000-008 and Ref. AMM 28-42-43-400-008.
1 If the aircraft is Post Mod 28904/SB28-1087, do the TSM procedure Ref. TSM TASK 28-42-00-810-875.
(b) Do a check of the related aircraft wiring as given in a procedure for a fuel probe in the defective group. Make sure that you check the wiring (between the FQIC rack connector and the fused/shorting plug connector) in all the wires that follow:
— common drive (excitation)
— common drive screen
— common drive return.
1 Repair all the unserviceable wiring and connectors Ref. ESPM 20-53-21.
(c) Trouble shoot the related harness as given in a procedure for a fuel probe in the defective group.
1 If necessary, replace the applicable harness.
(d) Trouble shoot the fuel probes on the related harness.
Start with the multi sensor (CADENSICON, CAPACITANCE INDEX COMPENSATOR), if applicable, fuel probes first.
(e) Do the test given in Para. 3.B.
(9) If the fault continues trouble-shoot:
— the fuel quantity probes/CICs 24QT1(2), Ref. TSM TASK 28-42-00-810-807
— the fuel quantity probe/CIC 39QT, Ref. TSM TASK 28-42-00-810-822.
NOTE: The step (9) is necessary because of a FQIC software deviation.
The probes with a Capacitance Index Compensator (CIC) are monitored as two probes (rather than one) by the software, as they supply two separate signals to the FQIC. As a result the failure of both of them is considered an internal drive oscillator failure; this causes the FQIC to be reported as the failed LRU and the cell/tank set to degraded. By examination of the Input Parameters page 2 (the FQIS PROBE CAPACITANCES) during an initial FQIC power-on (or reset), the failed LRU can be identified.
