DOC AIRBUS | TSM A320FFOB Shows XX
TASK 28-42-00-810-836-A
FOB Shows XX
A. Referenced Information
3. Fault Confirmation
Subtask 28-42-00-865-081-A
Subtask 28-42-00-810-085-A ** ON A/C NOT FOR ALL
[Rev.8 from Aug 2018]
2026.04.04 04:29:06 UTC
FOB Shows XX
WARNING:
OBEY THE FUEL SAFETY PROCEDURES.
1. Possible Causes- This procedure identifies which TSM procedures are applicable when the FOB shows XX. The possible causes are listed in the applicable procedures
A. Referenced Information
| REFERENCE | DESIGNATION |
|---|---|
| TSM TASK 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 |
| AMM 31-32-00-860-001 | Procedure to Get Access to the SYSTEM REPORT/TEST Menu Page |
| AMM 31-60-00-860-001 | EIS Start Procedure |
Subtask 28-42-00-865-081-A
A. Table of the circuit breakers used in this procedure:
Subtask 28-42-00-710-122-A | PANEL | DESIGNATION | FIN | LOCATION |
|---|---|---|---|
| ** ON A/C ALL | |||
| 49VU | FUEL/FQI/CHAN/1 | 1QT | A13 |
| 121VU | FUEL/FQI/CHAN/2 | 2QT | M27 |
B. Prerequisite Test
Subtask 28-42-00-710-085-A ** ON A/C NOT FOR ALL NOTE: The FQIS is a DC capacitive system. In such a system the fuel probes (which are the sensors) operate as capacitors. The dielectric of the capacitors is:
Each fuel probe operates as a variable capacitor with the capacitance value proportion to the ratio of the fuel probe covered in air or fuel. This is because the permittivity of the fuel is approximately twice 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.
It is important that the water in each fuel tank is kept to a minimum. The procedures given in the MPD and AMM must be fully completed. A failure to do so can cause the problems that follow:
(1) If you are: - 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 the capacitance value proportion to the ratio of the fuel probe covered in air or fuel. This is because the permittivity of the fuel is approximately twice 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.
It is important that the water in each fuel tank is kept to a minimum. The procedures given in the MPD and AMM must be fully completed. A failure to do so can cause the problems that follow:
- water contamination
- microbiological contamination (and growth)
- 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 (growth) is removed
- possible aircraft safety issues.
- not sure that the AMM refuel and all the MPD scheduled servicing tasks (related to water and mircrobiological contamination of the fuel) have been correctly and fully completed, do the TSM procedure (Ref. TSM TASK 28-42-00-810-879) and then do Para. 3.C.
- sure that the AMM refuel and all the MPD scheduled servicing tasks (related to water and mircrobiological contamination of the fuel) have been correctly and fully completed, do Para. 3.C.
C. Test
(1) If necessary, do the EIS Start Procedure (ECAM only) AMM 31-60-00-860-001.
(2) Do a check of the upper ECAM, ENGINE/WARNING DISPLAY to see if the FOB shows XX.
Subtask 28-42-00-710-085-B ** ON A/C NOT FOR ALL (1) If necessary, do the EIS Start Procedure (ECAM only) AMM 31-60-00-860-001.
(2) Do a check of the upper ECAM, ENGINE/WARNING DISPLAY to see if the FOB shows XX.
NOTE: XX data is known as a blanked display and is shown when there is no computed data.
(3) If the FOB: - shows a total fuel quantity and XX is not shown, no trouble shooting work steps are necessary
- shows XX, do Para. 4.A.
NOTE: The total fuel quantity, the fuel on board (FOB) shows XX if a (any) tank/cell shows XX.
A tank/cell will show XX if the worse case gauging error for that tank/cell is worse than five times the specified accuracy. This corresponds to Grades 4 or 5 as shown on the FQIS STATUS page.
A tank/cell will show XX if the worse case gauging error for that tank/cell is worse than five times the specified accuracy. This corresponds to Grades 4 or 5 as shown on the FQIS STATUS page.
C. Test
(1) If necessary, do the EIS Start Procedure (ECAM only) AMM 31-60-00-860-001.
(2) Do a check of the upper ECAM, ENGINE/WARNING DISPLAY to see if the FOB shows XX.
4. Fault Isolation(1) If necessary, do the EIS Start Procedure (ECAM only) AMM 31-60-00-860-001.
(2) Do a check of the upper ECAM, ENGINE/WARNING DISPLAY to see if the FOB shows XX.
NOTE: XX data is known as a blanked display and is shown when there is no computed data.
(3) If the FOB: - shows a total fuel quantity and XX is not shown, no trouble shooting work steps are necessary
- shows XX, do Para. 4.A.
NOTE: The total fuel quantity, the fuel on board (FOB) shows XX if a (any) tank shows XX.
A tank will show XX if the worse case gauging error for that tank is worse than five times the specified accuracy. This corresponds to Grade 4 as shown on the FQIS STATUS page.
A tank will show XX if the worse case gauging error for that tank is worse than five times the specified accuracy. This corresponds to Grade 4 as shown on the FQIS STATUS page.
Subtask 28-42-00-810-085-A ** ON A/C NOT FOR ALL
A. Procedure
(1) On the ECAM CONTROL PANEL, push (in) the FUEL P/BSW.
(2) Examine the FUEL system page to see at which location(s) the tank/cells show XX.
(a) Make a record of which tank/cell shows XX.
(3) If available, read the POST FLIGHT REPORT (PFR) to see if any FQIS, FAULT MESSAGES are shown.
(a) Make a record of all the FQIS, FAULT MESSAGES shown.
(4) Do the procedure to get access to the SYSTEM REPORT/TEST menu page AMM 31-32-00-860-001.
(5) When the SYSTEM REPORT/TEST menu page comes into view, push the line key adjacent to FUEL.
(6) 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.
(8) Examine the FQIS STATUS page and make a record of all the FAULT MESSAGES shown.
(a) Open the C/Bs 1QT and 2QT.
(b) Wait 5 seconds.
(c) Close the C/Bs 1QT and 2QT.
(11) If, after the FQIC reset, any fault messages recorded in steps (3)(a) and (8) are not now shown, remove (erase/delete) them from the (your) record.
(13) If the FOB:
(a) Shows a total fuel quantity, no more maintenance steps are necessary.
(b) Shows XX, remove (erase/delete) from the (your) record of fault messages, those fault messages (fuel probe LRUs) that are not installed in the tank/cell that shows XX and recorded in step (2)(a).
1 For the rectification of the FOB XX fault:
a Refer to the list of CFDS FAULT MESSAGES (LRUs) in AirN#agrave#V, Advanced Functions (Troubleshooting Package) for the applicable FAULT ISOLATION TASKs related to the final record of FAULT MESSAGES in step (13)(b).
b Do the applicable/related TSM tasks.
Subtask 28-42-00-810-085-B ** ON A/C NOT FOR ALL (1) On the ECAM CONTROL PANEL, push (in) the FUEL P/BSW.
(2) Examine the FUEL system page to see at which location(s) the tank/cells show XX.
(a) Make a record of which tank/cell shows XX.
(3) If available, read the POST FLIGHT REPORT (PFR) to see if any FQIS, FAULT MESSAGES are shown.
(a) Make a record of all the FQIS, FAULT MESSAGES shown.
(4) Do the procedure to get access to the SYSTEM REPORT/TEST menu page AMM 31-32-00-860-001.
(5) When the SYSTEM REPORT/TEST menu page comes into view, push the line key adjacent to FUEL.
(6) 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.
(7) When the FUEL menu page 2 comes into view, push the line key adjacent to FQIS STATUS. (8) Examine the FQIS STATUS page and make a record of all the FAULT MESSAGES shown.
NOTE: If necessary, use the MCDU PRINT option to get the record.
(9) Reset the FQIC as follows: (a) Open the C/Bs 1QT and 2QT.
(b) Wait 5 seconds.
(c) Close the C/Bs 1QT and 2QT.
NOTE: For the FQIC to do a (new) power up BITE test, a power supply interrupt (interval) of more than 5 seconds is necessary. This gives the current status of the FQIS components.
NOTE: The FUEL page FQIs will show XXs in amber color, for 35 seconds, during the FQIC power up BITE test.
A FQIS sensor fault must be sensed by the FQIC for 60 seconds before the applicable LRU identification is transmitted to the CFDS as unserviceable. The fault message is shown on the MCDU when set to SYSTEM REPORT/TEST (FUEL) and the FQIS STATUS page.
(10) When the BITE test is complete (XX shown on the FQIs for 35 seconds and the display has no dashes for 60 seconds), examine the FQIS STATUS page (again) for FAULT MESSAGES shown. A FQIS sensor fault must be sensed by the FQIC for 60 seconds before the applicable LRU identification is transmitted to the CFDS as unserviceable. The fault message is shown on the MCDU when set to SYSTEM REPORT/TEST (FUEL) and the FQIS STATUS page.
(11) If, after the FQIC reset, any fault messages recorded in steps (3)(a) and (8) are not now shown, remove (erase/delete) them from the (your) record.
NOTE: Maintenance steps are not necessary for those fault messages because they are considered spurious.
(12) Do a check of the upper ECAM, ENGINE/WARNING DISPLAY to see if the FOB is (has stayed) XX. (13) If the FOB:
(a) Shows a total fuel quantity, no more maintenance steps are necessary.
(b) Shows XX, remove (erase/delete) from the (your) record of fault messages, those fault messages (fuel probe LRUs) that are not installed in the tank/cell that shows XX and recorded in step (2)(a).
1 For the rectification of the FOB XX fault:
a Refer to the list of CFDS FAULT MESSAGES (LRUs) in AirN#agrave#V, Advanced Functions (Troubleshooting Package) for the applicable FAULT ISOLATION TASKs related to the final record of FAULT MESSAGES in step (13)(b).
b Do the applicable/related TSM tasks.
NOTE: This procedure identifies which TSM procedures are applicable when the FOB shows XX. The possible causes are listed in the applicable procedures .
c Do the check in Para. 3.C(2). A. Procedure
(1) On the ECAM CONTROL PANEL, push (in) the FUEL P/BSW.
(2) Examine the FUEL system page to see at which location(s) the tanks show XX.
(a) Make a record of which tank shows XX.
(3) If available, read the POST FLIGHT REPORT (PFR) to see if any FQIS, FAULT MESSAGES are shown.
(a) Make a record of all the FQIS, FAULT MESSAGES shown.
(4) Do the procedure to get access to the SYSTEM REPORT/TEST menu page AMM 31-32-00-860-001.
(5) When the SYSTEM REPORT/TEST menu page comes into view, push the line key adjacent to FUEL.
(6) When the FUEL menu page comes into view, push the line key adjacent to FQIS STATUS.
(7) Examine the FQIS STATUS page and make a record of all the FAULT MESSAGES shown.
(a) Open the C/Bs 1QT and 2QT.
(b) Wait 10 seconds.
(c) Close the C/Bs 1QT and 2QT.
(10) If, after the FQIC reset, any fault messages recorded in steps (3)(a) and (7) are not now shown, remove (erase/delete) them from the (your) record.
(12) If the FOB:
(a) Shows a total fuel quantity, no more maintenance steps are necessary.
(b) Shows XX, remove (erase/delete) from the (your) record of fault messages, those fault messages (fuel probe LRUs) that are not installed in the tank that shows XX and recorded in step (2)(a).
1 For the rectification of the FOB XX fault:
a Refer to the list of CFDS FAULT MESSAGES (LRUs) in AirN#agrave#V, Advanced Functions (Troubleshooting Package) for the applicable FAULT ISOLATION TASKs related to the final record of FAULT MESSAGES in step (12)(b).
b Do the applicable/related TSM tasks.
(1) On the ECAM CONTROL PANEL, push (in) the FUEL P/BSW.
(2) Examine the FUEL system page to see at which location(s) the tanks show XX.
(a) Make a record of which tank shows XX.
(3) If available, read the POST FLIGHT REPORT (PFR) to see if any FQIS, FAULT MESSAGES are shown.
(a) Make a record of all the FQIS, FAULT MESSAGES shown.
(4) Do the procedure to get access to the SYSTEM REPORT/TEST menu page AMM 31-32-00-860-001.
(5) When the SYSTEM REPORT/TEST menu page comes into view, push the line key adjacent to FUEL.
(6) When the FUEL menu page comes into view, push the line key adjacent to FQIS STATUS.
(7) Examine the FQIS STATUS page and make a record of all the FAULT MESSAGES shown.
NOTE: If necessary, use the MCDU PRINT option to get the record.
(8) Reset the FQIC as follows: (a) Open the C/Bs 1QT and 2QT.
(b) Wait 10 seconds.
(c) Close the C/Bs 1QT and 2QT.
NOTE: For the FQIC to do a (new) power up BITE test, a power supply interrupt (interval) of more than 10 seconds is necessary. This gives the current status of the FQIS components.
NOTE: The FUEL page FQIs will show XXs in amber color, for 35 seconds, during the FQIC power up BITE test.
A FQIS sensor fault must be sensed by the FQIC for 60 seconds before the applicable LRU identification is transmitted to the CFDS as unserviceable. The fault message is shown on the MCDU when set to SYSTEM REPORT/TEST (FUEL) and the FQIS STATUS page.
(9) When the BITE test is complete (XX shown on the FQIs for 35 seconds and the display has no dashes for 60 seconds), examine the FQIS STATUS page (again) for FAULT MESSAGES shown. A FQIS sensor fault must be sensed by the FQIC for 60 seconds before the applicable LRU identification is transmitted to the CFDS as unserviceable. The fault message is shown on the MCDU when set to SYSTEM REPORT/TEST (FUEL) and the FQIS STATUS page.
(10) If, after the FQIC reset, any fault messages recorded in steps (3)(a) and (7) are not now shown, remove (erase/delete) them from the (your) record.
NOTE: Maintenance steps are not necessary for those fault messages because they are considered spurious.
(11) Do a check of the upper ECAM, ENGINE/WARNING DISPLAY to see if the FOB is (has stayed) XX. (12) If the FOB:
(a) Shows a total fuel quantity, no more maintenance steps are necessary.
(b) Shows XX, remove (erase/delete) from the (your) record of fault messages, those fault messages (fuel probe LRUs) that are not installed in the tank that shows XX and recorded in step (2)(a).
1 For the rectification of the FOB XX fault:
a Refer to the list of CFDS FAULT MESSAGES (LRUs) in AirN#agrave#V, Advanced Functions (Troubleshooting Package) for the applicable FAULT ISOLATION TASKs related to the final record of FAULT MESSAGES in step (12)(b).
b Do the applicable/related TSM tasks.
NOTE: This procedure identifies which TSM procedures are applicable when the FOB shows XX. The possible causes are listed in the applicable procedures .
c Do the check in Para. 3.C(2).