Fuel Quantity/CIC Probe 39QT, Center Tank

TASK 28-42-00-810-822-A
Fuel Quantity/CIC Probe 39QT, Center Tank

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: EN50020, UL913 OR EQUIVALENT). TEST EQUIPMENT THAT IS NOT APPROVED CAN CAUSE FIRE OR AN EXPLOSION.

1. Possible Causes

FQIC [3QT]
fused adaptor at 7512VC
aircraft wiring
water contamination
microbiological contamination
unwanted material
HARNESS-CHAN B, CTR TK [18QT]
PROBE-FUEL QTY, NO 5 AND CIC, CTR TK GROUP B [39QT]

2. Job Set-up Information
A. Fixtures, Tools, Test and Support Equipment

REFERENCE	QTY	DESIGNATION
No specific	AR	MULTIMETER - STANDARD

B. Referenced Information

REFERENCE	DESIGNATION
TSM TASK 28-11-00-810-810-A	Fuel - Unwanted Material (Debris) In The Center-Tank Fuel Installation
TSM TASK 28-42-00-810-803-A	Fuel Quantity - Cadensicon 20QT, Center Tank
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 12-32-28-281-001	Drain Water Content
AMM 12-32-28-281-003	Sample Fuel for Microbiological Contamination Analysis
ESPM 2052210
ESPM 2052220
ESPM 2053210
AMM 24-41-00-861-002	Energize the Aircraft Electrical Circuits from the External Power
AMM 24-41-00-862-002	De-energize the Aircraft Electrical Circuits Supplied from the External Power
AMM 28-10-00-910-001	Safety Procedures When You Do Work in a Fuel Tank
AMM 28-10-00-910-002	Access to the Fuel Tanks and the Work Areas
AMM 28-11-00-600-003	Removal of Microbiological Particles
AMM 28-42-00-00-
AMM 28-42-00-740-003	Interrogation of the FQIS Input Parameters Pages
AMM 28-42-00-740-007	Interrogation of the (SMITHS INDUSTRIES) FQIS Trouble Shooting Data
ASM 284209
AMM 28-42-15-000-002	Removal of the Center Tank Fuel-Quantity-Probe
AMM 28-42-15-400-002	Installation of the Center Tank Fuel-Quantity-Probe
AWM 284216
AMM 28-42-34-000-001	Removal of the Fuel Quantity-Indicating Computer (FQIC)
AMM 28-42-34-400-001	Installation of the Fuel Quantity-Indicating Computer (FQIC)
AMM 28-42-44-000-002	Removal of the Center Tank Harness
AMM 28-42-44-400-002	Installation of the Center Tank Harness
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
AMM 31-60-00-860-002	EIS Stop Procedure
AMM 32-12-00-010-001	Open the Main Gear Doors for Access
AMM 32-12-00-410-001	Close the Main Gear Doors after Access

3. Fault Confirmation
Subtask 28-42-00-865-071-A ** ON A/C NOT FOR ALL

A. Table of the circuit breakers used in this procedure:

PANEL	DESIGNATION	FIN	LOCATION
** ON A/C NOT FOR ALL
49VU	FUEL/FQI/CHAN/1	1QT	A13
121VU	FUEL/FQI/CHAN/2	2QT	M27

Subtask 28-42-00-710-071-B ** ON A/C NOT FOR ALL

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.

It is very 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
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.

The fuel probe sensor of this procedure has its inner (aluminium) tube divided into two sections.
The lower section is called the compensator.
In normal operation the compensator stays fully covered (immersed) in fuel because it is installed near the fuel tank floor.
It lets the FQIC 3QT compute the permittivity (K value) of the fuel in the center tank from a second source.
The primary source of the permittivity (K value) is the center tank cadensicon 20QT (Ref. TSM TASK 28-42-00-810-803).

(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) To keep the number of computer replacements (with no fault found) to a minimum, do the power on BITE test of the FQIS 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 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 up BITE test, a power supply interrupt (interval) of more than 5 seconds is necessary. This gives the current status of the FQIS components.

(3) Do the EIS Start Procedure (ECAM only) AMM 31-60-00-860-001.
(4) On the ECAM control panel, push (in) the FUEL P/BSW.
(5) Make sure that the FUEL page shows on the ECAM lower display unit.
(6) Wait 60 seconds.
(7) Continue as follows:

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.

(a) Do the procedure to get access to the SYSTEM REPORT/TEST menu page 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.
(8) Examine the FQIS STATUS page.
(a) Make a record of the messages shown (or use the PRINT function to get a copy).
(b) When you have got a copy or print, press the RETURN key on the MCDU.
(c) When the FUEL menu page 2 comes into view, push the line key adjacent to INPUT PARAMETER VALUES.
(9) 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.
(10) 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).
(11) Compare the original failure and your records with those that follow:

if the FQI goes inoperative or degraded and is associated with multiple fuel probe failures, do the 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 message C QTY PROBE 39QT is shown and the CIC K given on the I/PARAMETER page 1 (and/or the related L(R) wing capacitance value on page 2) are shown with an * (asterisk) or a X, do Para. 4.A.
if the message C QTY PROBE 39QT is not shown and the values given on the I/P PARAMETER pages are correct, no trouble shooting work steps are necessary.

NOTE: The (serviceable and unserviceable) input parameter display values shown on the pages 1 and 2 are given in the AMM procedure AMM 28-42-00-740-003.

NOTE: You can get data from the:

Description and Operation (D and O) section of the Aircraft Maintenance Manual (AMM), the Fuel Quantity Indicating System (FQIS) AMM 28-42-00-00-
Trouble-shooting Manual (TSM) - Task Supporting Data (Ref. P. Block 301)
Aircraft Schematic Manual (ASM) ASM 284209.

NOTE: You can get more Trouble-shooting data from the CFDS(FUEL):

Input Parameters Page 2 AMM 28-42-00-740-003
FQIC Trouble Shooting Data AMM 28-42-00-740-007.

NOTE: OPTIONAL TESTING:
If a DC Capacitance Fuel System Tester is available, measurements can be taken before a decision is made to go into or close up a fuel tank. The Tester can be connected to the FQIC rack connector or the related tank wall connector. (Ref. P. Block 301 for the Tank Units DC Capacitance Values).

4. Fault Isolation
Subtask 28-42-00-810-071-C ** ON A/C NOT FOR ALL

A. Procedure
(1) Temporarily replace the FQIC 3QT with a serviceable item AMM 28-42-34-000-001 and 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 serviceable before you start more steps.

(2) If the message C QTY PROBE 39QT:

is not shown (and the related input parameter values show correct), complete the installation of the FQIC [3QT] AMM 28-42-34-000-001 and AMM 28-42-34-400-001
is shown (and the related input parameter values stay incorrect), do step (3).

(3) Remove the temporary installed serviceable FQIC 3QT AMM 28-42-34-000-001 and return it to stores.
(4) Install the initial FQIC 3QT AMM 28-42-34-400-001.
(5) Get access to the tank wall connector 7512VC and fused adaptor in the right MLG bay AMM 32-12-00-010-001.
(6) Remove the fused adaptor at the tank wall connector 7512VC.

NOTE: The fused connector is installed between the tank wall connector 7512VC and the free connector 7512VC-A. All of the capacitive drive return wires go through a fuse.

(7) Use a MULTIMETER - STANDARD to do a check for continuity, of the related in line fuses ASM 284209 between:
(a) The pins D and D.
(b) The pins V and V.
(8) If the continuity test shows:
(a) The two fuses have continuity (serviceable), install the serviceable fused adaptor and continue with step (9).
(b) One fuse or two fuses are open circuit (first time unserviceable):
1 Replace the fused adaptor at 7512VC with a serviceable item.
2 Do the test given in Para. 3.B.
(c) One fuse or two fuses are open circuit (second time unserviceable):
1 Continue with step (9), only replace the fused adaptor at 7512VC when the cause of the short circuit has been identified and corrected.
(9) Remove the FQIC 3QT AMM 28-42-34-000-001.
(10) Get access to the tank wall connector 7512VC in the right MLG bay AMM 32-12-00-010-001.
(11) Do a visual inspection and electrical tests of the aircraft wiring AWM 284216 between the FQIC rack connector 3QT-A and the tank wall connector 7512VC-A as follows:
(a) Visual Inspection
Make sure that good lighting is available.
Do a visual inspection and look for distortion (bent, pinched or stretched), damage (broken, chafed or cut), discoloration, overheating (burnt, melted or arcing), liquid contamination, loose electrical connection or incorrect assembly, of the items that follow:

FQIC rack connector 3QT-A, pins 5C, 7C, 10C and 13E
receptacle 210VC and connector 210VC-A
receptacle 1970VC and connector 1970VC-A
terminal block 7522VT and all of its connections
receptacle 7570VC and connector 7570VC-A
pressure seal feedthrough 7510VP
receptacle 7512VC-A, pins U, E, V, D and C
adjacent and related connecting wires.

(b) Electrical Tests
Do a continuity test ESPM 2052210 and a test for a short circuit ESPM 2052220 of the wires that follow AWM 284216:

FQIC rack connector 3QT-A, pin 5C to connector 7512VC-A, pin U (probe 5 signal)
FQIC rack connector 3QT-A, pin 7C to connector 7512VC-A, pin E (CIC signal)
FQIC rack connector 3QT-A, pin 10C to connector 7512VC-A, pin V and D (common drive return)
FQIC rack connector 3QT-A, pin 13E to connector 7512VC-A, pin C (common drive).

the connector 7512VC-A to the fused adaptor
the fused adaptor to the tank wall receptacle 7512VC.

(e) Install the initial FQIC 3QT AMM 28-42-34-400-001.
(f) Do the test given in Para. 3.B.
(12) If the fault continues:
(a) Do a check for water contamination as given in the procedure 'Drain Water Content' AMM 12-32-28-281-001.
(b) Do a check (sample) for microbiological contamination AMM 12-32-28-281-003. If the results are MODERATE or HEAVY do the applicable procedure or action 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.

(c) Get access to the center tank AMM 28-10-00-910-001 and AMM 28-10-00-910-002.
(d) If during the steps to get access to the fuel probe you find:
1 Microbiological contamination in the fuel-tank, do the steps that follow:
a Make a record of what you have found in the aircraft technical log.
b Remove all the microbiological contamination AMM 28-11-00-600-003.
2 Debris unwanted material (example, locking wire or an aircraft fastener), do the TSM procedure for Unwanted Material (Debris) In The Center-Tank Fuel Installation (Ref. TSM TASK 28-11-00-810-810).
(13) Do a check of the HARNESS-CHAN B, CTR TK [18QT] AWM 284216 and replace, if necessary, AMM 28-42-44-000-002 and AMM 28-42-44-400-002.
(14) If the harness 18QT is serviceable, replace the PROBE-FUEL QTY, NO 5 AND CIC, CTR TK GROUP B [39QT] AMM 28-42-15-000-002 and AMM 28-42-15-400-002.

5. Close-up
Subtask 28-42-00-942-057-A ** ON A/C NOT FOR ALL

A. Close-up and Removal of Equipment
(1) Do the EIS Stop Procedure AMM 31-60-00-860-002.
(2) If applicable, close the MLG doors AMM 32-12-00-410-001.
(3) If necessary, de-energize the aircraft electrical circuits AMM 24-41-00-862-002.
(4) Make sure that the work area is clean, clear of tool(s) and other items.
(5) Remove the ground support and maintenance equipment, the special and standard tools and all other items.

[Rev.8 from Aug 2018] 2026.04.04 04:29:00 UTC