Fuel Quantity Probe 66QT2, ACT 2

TASK 28-42-00-810-859-A
Fuel Quantity Probe 66QT2, ACT 2

1. Possible Causes

FQIC [3QT]
aircraft wiring
water contamination
microbiological contamination
PROBE-FQI NO 2, ACT2 [66QT2]

2. Job Set-up Information
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 12-32-28-281-001	Drain Water Content
AMM 12-32-28-281-003	Sample Fuel for Microbiological Contamination Analysis
ESPM 2053210
AMM 24-41-00-861-002	Energize the Aircraft Electrical Circuits from the External Power
AMM 28-11-00-600-003	Removal of Microbiological Particles
AMM 28-11-27-000-001	Removal of the Additional Center Tank (ACT)
AMM 28-42-00-740-003	Interrogation of the FQIS Input Parameters Pages
ASM 284209
AWM 284221
AMM 28-42-24-000-001	Removal of the Fuel Quantity Probe of the ACT
AMM 28-42-24-400-001	Installation of the Fuel Quantity Probe of the ACT
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 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
AWM 944220
TSM TASK 28-42-00-03	QUANTITY INDICATING - TASK SUPPORTING DATA

3. Fault Confirmation
Subtask 28-42-00-865-093-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 28-42-00-710-108-B ** ON A/C NOT FOR ALL

B. Test

NOTE: The FQIS is a positive 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.

(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 10 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 10 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 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 comes into view, push the line key adjacent to INPUT PARAMETERS.
(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).
(b) When you have got a copy or print, press the NEXT PAGE key on the MCDU.
(11) Examine the INPUT PARAMETERS (page 3 - FQIS PROBE CAPACITANCES (of ACTs).
(a) Make a record of the page 3 (or use the PRINT function to get a copy).
(12) 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, 2 and 3 (shown with a - (dash) or out of range (see the note below)), do the procedure (Ref. TSM TASK 28-42-00-810-879)
if the message A2 QTY PROBE 66QT2 or A2 QTY PROBE 66QT2/WRG is shown and the values given on the I/P PARAMETER page 1 and 2 are correct (but related ACT value on page 3 is shown with a - (dash) or out of range), do Para. 4.A.
if the message A2 QTY PROBE 66QT2 or A2 QTY PROBE 66QT2/WRG is not shown and the values given on the I/P PARAMETER pages are correct, no trouble shooting work steps are necessary.

NOTE: If the input parameter values are calculated (in the FQIC 3QT) they are shown (displayed). This is also true when the parameters are out of range. A - (dash) is shown if a parameter is not measured. Example, because of a fuel-probe sensor detector failure. Out of range values of more than the display capability are shown as the maximum value of the display.

The normal range of fuel-probe capacitance values (at dry and full) can be got from the Tank Units DC Capacitance Values 28-42-00-03 TSM TASK 28-42-00-03.

NOTE: You can get data from the:

Description and Operation (D and O) section of the Aircraft Maintenance Manual (AMM), Chap. 28-42-00, the Fuel Quantity Indicating System (FQIS)
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 3, the ACT PROBE CAPACITANCES AMM 28-42-00-740-003
FQIC Trouble Shooting Data (Ref. P. Block 301).

4. Fault Isolation
Subtask 28-42-00-810-108-B ** 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 is serviceable before you start more steps.

(2) If the message A2 QTY PROBE 66QT2 or A2 QTY PROBE 66QT2/WRG:

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) Get access to:

the PROBE-FQI No. 2, ACT 2 connector 66QT2-A AMM 28-42-24-000-001
the ACT 2 aircraft to tank break connector 7618VC2 AMM 28-11-27-000-001.

(5) Do a check of the aircraft wiring AWM 284221 between:

the connector 66QT2-A and the connector 7618VC2-A
the connector 7618VC2 and the FQIC 3QT rack connector.

NOTE: Each capacitive fuel probe is supplied with an alternating current drive, from the FQIC.
The fuel probes of the ACT 1 and ACT 2 share the drive and drive return (two aircraft wires) between the FQIC rack connector and the terminal block 7517VT.
The location of the terminal block is 145STA1860 AWM 944220.
At the terminal block:

the drive wire divides to supply the ACT 1 left side fuel probe 65QT1 and the ACT 2 right side fuel probe 66QT2 in parallel
the drive return wire also divides to supply the ACT 1 left side fuel probe 65QT1 and the ACT 2 right side fuel probe 66QT2 in parallel.

Diodes located in the terminal housing of the fuel probe half wave rectify the output signal. The positive going, dc current signal (in proportion to the capacitance value/fuel height from the fuel probe) is routed directly from the related tank connector to the FQIC.

(6) Repair all the unserviceable wiring and connectors ESPM 2053210.
(7) Install the initial FQIC 3QT AMM 28-42-34-400-001.
(8) Do the test given in Para. 3.B.
(9) 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.

[Rev.8 from Aug 2018] 2026.04.04 04:39:48 UTC