Troubleshooting from the FQIS STATUS REPORT (BITE) When a Channel Grade Shows 4

TASK 28-42-00-810-877-A
Troubleshooting from the FQIS STATUS REPORT (BITE) When a Channel Grade Shows 4

WARNING: OBEY THE FUEL SAFETY PROCEDURES.

1. Possible Causes

fuel contamination (example, water or microbiological)
FQIC [3QT]
CADENSICON-RIB 2-3, L WNG TK INR GROUP A [19QT1]
aircraft wiring
PROBE-FUEL QTY NO 4 AND CIC,RIB 2-3 L WNG TK INR GRP B [24QT1]
CADENSICON-RIB 2-3, R WNG TK INR GROUP A [19QT2]
CADENSICON-CTR TK [20QT]
PROBE-FUEL QTY NO 4 AND CIC,RIB 2-3 R WNG TK INR GRP B [24QT2]
PROBE-FUEL QTY, NO 5 AND CIC, CTR TK GROUP B [39QT]

2. Job Set-up Information
A. Referenced Information

REFERENCE	DESIGNATION
TSM TASK 28-42-00-810-802-A	Fuel Quantity - Cadensicon 19QT1(2), Left(Right) Wing
TSM TASK 28-42-00-810-803-A	Fuel Quantity - Cadensicon 20QT, Center Tank
TSM TASK 28-42-00-810-807-A	Fuel Quantity/CIC Probe 24QT1(2), Left(Right) Wing Tank
TSM TASK 28-42-00-810-822-A	Fuel Quantity/CIC Probe 39QT, Center Tank
AMM 12-11-28-650-003	Pressure Refuel with Automatic Control
AMM 12-11-28-650-004	Pressure Refuel with Manual Control
AMM 12-32-28-281-001	Drain Water Content
AMM 12-32-28-281-003	Sample Fuel for Microbiological Contamination Analysis
AMM 28-25-00-650-001	Pressure Defuel
AMM 28-25-00-650-003	To Drain Remaining Fuel from the Wing Tanks and the Center Tank
AMM 28-42-00-740-001	Status Report (BITE)
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)

3. Fault Confirmation
Subtask 28-42-00-865-113-A ** ON A/C NOT FOR ALL

A. Table of the circuit breakers referred to 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 28-42-00-710-118-B ** ON A/C NOT FOR ALL

B. Test

Use this procedure if:

during the FQIS operation, with the two (28VDC supply) C/Bs of the FQIC 3QT closed, no FQIS normal mode or class 3 fault messages are given on the CFDS-FUEL
during the Status Report (BITE) when each C/B of the FQIC 3QT is pulled (in sequence), it causes the powered channel tank grade to change from GRADE 1 to 4 on the CFDS - FUEL, FQIS STATUS.

NOTE: The operating grade numbers for each channel (given before), is as follows:

GRADE 1 = Normal Operation
GRADE 4 = Failed Operation (FQIS displays show crosses).

(1) Make sure that all the applicable fuel and fuel tank scheduled servicing tasks from the Maintenance Planning Document (MPD) have been complied with.

NOTE: Steps (1) thru (3) must be done fully (thoroughly) to eliminate or remove (as far as is possible) the effects of fuel contamination (example, water or microbiological).

(2) If you are not sure when the fuel tanks were last:
(a) Sampled for microbiological contamination, do AMM 12-32-28-281-003.
(b) Drained of water content, do AMM 12-32-28-281-001.
(3) If you are not sure of the quanlity of all the fuel in the aircraft tanks:
(a) Defuel the aircraft AMM 28-25-00-650-001.
(b) Drain the remaining fuel from the fuel tanks AMM 28-25-00-650-003.
(c) Refuel (with fuel of known specification) AMM 12-11-28-650-003 or AMM 12-11-28-650-004.
(4) Do the Status Report (BITE) AMM 28-42-00-740-001.
(a) If, during channel 1 operation (when C/B-2QT pulled) the FQIS STATUS shows:

CH1 GRADE 4 and CH2 GRADE X, do Para. 4.A.
CH1 GRADE 1 and CH2 GRADE X, no maintenance steps are necessary.

(b) If, during channel 2 operation (when C/B-1QT pulled) the FQIS STATUS shows:

CH1 GRADE X and CH2 GRADE 4, do Para. 4.B.
CH1 GRADE X and CH2 GRADE 1, no maintenance steps are necessary.

4. Fault Isolation
Subtask 28-42-00-810-134-E ** ON A/C NOT FOR ALL

A. Procedure - When Channel 1 Shows Grade 4
(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) Do the Status Report (BITE) AMM 28-42-00-740-001.
(3) If, on the FQIS STATUS (as the related channel C/Bs are pulled):

CH1 shows GRADE 1 (or X) and CH2 show GRADE X (or 1), complete the installation of the FQIC [3QT] AMM 28-42-34-000-001 and AMM 28-42-34-400-001.
CH1 shows GRADE 4 (or X) and CH2 show GRADE X (or 4), do step (4).

Subtask 28-42-00-810-135-E ** ON A/C NOT FOR ALL

B. Procedure - When Channel 2 Shows Grade 4
(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) Do the Status Report (BITE) AMM 28-42-00-740-001.
(3) If, on the FQIS STATUS (as the related channel C/Bs are pulled):

CH1 shows GRADE 1 (or X) and CH2 show GRADE X (or 1), complete the installation of the FQIC [3QT] AMM 28-42-34-000-001 and AMM 28-42-34-400-001.
CH1 shows GRADE 4 (or X) and CH2 show GRADE X (or 4), do step (4).

(4) Remove the temporary installed serviceable FQIC 3QT AMM 28-42-34-000-001 and return it to stores.
(5) Installed the original FQIC 3QT AMM 28-42-34-000-001 and continue with step (6).
(6) If the fault continues, trouble shoot:
(a) The CADENSICON-RIB 2-3, R WNG TK INR GROUP A [19QT2] as given in TSM (Ref. TSM TASK 28-42-00-810-802) Para. 4.A. from the step reference the aircraft wiring.
(b) The CADENSICON-CTR TK [20QT] as given in TSM (Ref. TSM TASK 28-42-00-810-803) Para. 4.A. from the step reference the aircraft wiring.
(7) If the fault continues, trouble shoot:
(a) The PROBE-FUEL QTY NO 4 AND CIC,RIB 2-3 R WNG TK INR GRP B [24QT2] as given in TSM (Ref. TSM TASK 28-42-00-810-807) Para. 4.A. from the step reference the aircraft wiring.
(b) The PROBE-FUEL QTY, NO 5 AND CIC, CTR TK GROUP B [39QT] as given in TSM (Ref. TSM TASK 28-42-00-810-822) Para. 4.A. from the step reference the aircraft wiring.

[Rev.8 from Aug 2018] 2026.04.04 04:29:10 UTC