Fuel - ACT 2 Sequence Failure

TASK 28-28-00-810-807-A
Fuel - ACT 2 Sequence Failure

WARNING: OBEY THE FUEL SAFETY PROCEDURES.

1. Possible Causes

FLSCU 3 [47QJ]
PROBE-FQI NO 1, ACT2 [65QT2]
PROBE-FQI NO 2, ACT2 [66QT2]
C/B-ACT2/CTL & SPLY [10QH]
aircraft wiring
RELAY-POWER SUPPLY SWITCH [39QU]
RELAY-SEQUENCE [18QH]
RELAY-FAULT SENSE, ACT 2 (31QH)
[14QH]
RELAY-REFUEL/TRANSFER CONTROL, ACT2 [36QU]
RELAY-REFUEL INHIBIT, ACT2 [38QU]
RELAY-INLET VALVE CONTROL, ACT2 [20QH]
ACTUATOR-FUEL INLET VALVE, ACT2 [5QH2]
VALVE-FUEL INLET, ACT2 [166QM2]
RELAY-AUTO/MANUAL TRANSFER, ACT [23QH]

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 28-28-00-810-801-A	Fuel Pumps - ACT Manual Transfer Pump 1QH System Malfunction
TSM TASK 28-28-00-810-801-A-01	Fuel Pumps - ACT Manual Transfer Pump 1QH System Malfunction (802VU ACT Relay Testbox)
TSM TASK 28-46-00-810-834-A	ACT 2 - FLSCU-3 Channel LS8 - Low Level Sensor No. 1 Failure
TSM TASK 28-46-00-810-835-A	ACT 2 - FLSCU-3 Channel LS2 - Low Level Sensor No. 2 Failure
AMM 25-71-11-000-001	Removal of the Additional Center-Tank (ACT) Relay-Box 802VU
AMM 25-71-11-400-001	Installation of the Additional Center-Tank (ACT) Relay-Box 802VU
AMM 28-28-00-710-001	Operational Check of the ACT Manual Transfer System
ASM 282801
ASM 282803
AMM 28-28-34-000-001	Removal of the ACT Fuel Inlet Valve (166QM)
AMM 28-28-34-400-001	Installation of the ACT Fuel Inlet Valve (166QM)
AMM 28-28-54-000-001	Removal of the ACT Fuel Inlet Valve Actuator (5QH)
AMM 28-28-54-400-001	Installation of the ACT Fuel Inlet Valve Actuator (5QH)
AMM 28-46-34-000-001	Removal of the Fuel-Level Sensing Control-Unit (FLSCU)
AMM 28-46-34-400-001	Installation of the Fuel-Level Sensing Control-Unit (FLSCU)

3. Fault Confirmation
Subtask 28-28-00-865-054-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
121VU	ACT2/CTL & SPLY	10QH	P28

Subtask 28-28-00-710-056-A ** ON A/C NOT FOR ALL

B. Test
(1) Do the Operational Test of the ACT Manual Transfer System AMM 28-28-00-710-001.

NOTE: To get a fuel transfer from ACT 2:

the ACT 2 must contain more than approximately 80 kg (176.3698 lb) of fuel
the center tank must contain less than approximately 6000 kg (13227.7320 lb) of fuel.

(2) If fuel can be seen to transfer from the ACT 1 but it is not possible to transfer fuel from the ACT 2:

open, then close the C/B-ACT2/XFR VLV/AUTO CTL (10QH).

NOTE: Do not open the C/B-10QH more than once every 60 seconds.
This is to give the relay logic and actuator drives time to return to the prerequisite positions.

(3) Do the test in step (1).
(4) If it is not possible to transfer fuel from ACT 2, during steps (1) thru (3);

OR

The ACT 2 Fuel Inlet - Actuator and Valve Positions, fail to take up the positions as shown in ACT Manual Transfer, Pump System Failure (Ref. TSM TASK 28-28-00-810-801) Para. 4.A. step (2) thru (3) (d) 2_:

go to Para. 4.A.

4. Fault Isolation
Subtask 28-28-00-810-056-B ** ON A/C NOT FOR ALL

A. Procedure
(1) Remove the FLSCU-3 (47QJ) from its rack AMM 28-46-34-000-001.

NOTE: This is to simulate known correct inputs to the relay logic, from the ACT 1 and the ACT 2, of all low level sensors wet.

(2) Make sure that the P/BSW-FUEL/ACT/AUTO (24QH) is pushed in (ACT manual transfer is selected).
(3) Connect a MULTIMETER - STANDARD (in preparation to do a test for 28VDC) to the RELAY-PANEL (802VU) test connector 4068VC, between the pin E (+) and a suitable ground.
(4) Monitor the multimeter during the next step of the procedure and for a further 75 seconds.
(5) Open, then close the C/B-ACT2/XFR VLV/AUTO CTL (10QH).
(6) Compare the results of the test with those listed in the table that follows and go to the necessary step of the procedure.

TEST RESULT	GO TO STEP
The 28VDC shows momentarily	(7)
The 28VDC is not shown	(8)
The 28VDC is shown permanently	(9)
The 28VDC shows momentarily, and then after 15 secs comes back	(10)
The 28VDC shows momentarily, and then after 60 secs comes back	(11)
secs = seconds

(7) The 28VDC shows momentarily

NOTE: With the FLSCU-3 (47QJ) removed, this shows the relay logic has selected the ACT 2 inlet valve (to open) and has been correctly latched (held open).

(a) Install the FLSCU 3 [47QJ] AMM 28-46-34-400-001.
(b) Do the test given in Para. 3.B.(1).
(c) If the fault continues:

do the PROBE-FQI NO 1, ACT2 [65QT2] Failure (Ref. TSM TASK 28-46-00-810-834)
do the PROBE-FQI NO 2, ACT2 [66QT2] Failure (Ref. TSM TASK 28-46-00-810-835).

(d) Install the FLSCU3 AMM 28-46-34-400-001.
(e) Do the test given in Para. 3.B.(1).
(f) If the fault continues, do a check, for obvious signs of damage, blockage or incorrct installation of:
1 The ACT 2 interconnecting fuel and vent pipes.
2 The ACT 2 internal fuel and vent pipes.
3 Repair, un-block or install correctly all the unserviceable ACT 2 fuel and vent pipes.
(g) Do the test given in Para. 3.B.(1).
(8) The 28VDC is not shown

NOTE: This shows some type of 28VDC power supply failure.

(a) Do a check of and replace, if necessary, the C/B-ACT2/CTL & SPLY [10QH] .
(b) Do a check of the aircraft wiring ASM 282801 between the C/B-ACT2/XFR VLV/AUTO CTL (10QH), terminal 2 and the free connector 4065VC-A, pin H.
1 Repair all the unserviceable wiring and connectors.
2 Install the FLSCU3 (47QJ) AMM 28-46-34-400-001.
3 Do the test given in Para. 3.B.(1).
(c) If the fault continues, replace the RELAY-PANEL (802VU) AMM 25-71-11-000-001 and AMM 25-71-11-400-001.

If there is no relay panel available, go to step (d).

1 Do the test given in the Para. 3.B.
(d) If the fault continues:
1 Do a check of ASM 282803 and replace if necessary:

the RELAY-POWER SUPPLY SWITCH [39QU]
the RELAY-SEQUENCE [18QH] .

2 Do a check of the RELAY-PANEL (802VU) wiring ASM 282801 and ASM 282803 between the connector to relay and relay to relay wires, as shown in the table that follows:

NOTE: The circuit connections shown in the table are abbreviated, for example:

the connector 4065VC, pin H is shown as 4065VC-H
the RELAY-POWER SUPPLY, SW (39QU), terminal D3 is shown as RL 39QU-D3.

-----------------------------------------------------------------------------

! CONNECTOR-PIN ! RELAY-TERMINAL TO RELAY-TERMINAL ! CONNECTOR-PIN !

!-----------------------------------------------------------------------------!

! 4065VC-H ----------------------------------- RL 39QU-D3 !

! RL 39QU-D2 ----------------- RL 18QH-C2 !

! RL 18QH-C3 ---------------------------------- 4068VC-E !

-----------------------------------------------------------------------------

a Repair all the unserviceable wiring and connectors.
b Install the FLSCU3 (47QJ) AMM 28-46-34-400-001.
c Do the test given in Para. 3.B.(1).
(9) The 28VDC is shown permanently

NOTE: This shows that the C/B-10QH is closed and the system configured for two (2) ACT operation but that the RELAY-18QH stays in the ACT 1 position.
The trouble-shooting in this step checks components and wiring associated with the initial circuit path to set (energize) the sequence relay 18QH.

(a) If the fault continues, replace the RELAY-PANEL (802VU) AMM 25-71-11-000-001 and AMM 25-71-11-400-001.

If there is no relay panel available, go to step (b).

1 Do the test given in the Para. 3.B.
(b) Do the steps that follow:
1 Do a check of ASM 282803 and replace, if necessary:

the diode 4005VD
the RELAY-SEQUENCE [18QH]
the RELAY-FAULT SENSE, ACT 2 (31QH)
the [14QH] .

a Do a check of the RELAY-PANEL (802VU) wiring ASM 282801 and ASM 282803 between the connector to relay and relay to relay wires, as shown in the table that follows:

NOTE: The circuit connections shown in the table are abbreviated, for example:

the connector 4065VC, pin H is shown as 4065VC-H
the RELAY-POWER SPLY SW (39QU), terminal D3 is shown as RL 39QU-D3

-----------------------------------------------------------------------------

! CONNECTOR-PIN ! RELAY-TERMINAL TO RELAY-TERMINAL ! CONNECTOR-PIN !

!-----------------------------------------------------------------------------!

! 4065VC-H ----------------------------------- RL 39QU-D3 !

! RL 39QU-D2 ----------------- RL 31QH-B2 !

! RL 31QH-B3 (+) via diode (-) RL 18QH-X1 !

! RL 18QH-X2 ----------------- RL 14QH-B3 !

! RL 14QH-B2 ---------------------------------- 4065VC-<T !

-----------------------------------------------------------------------------

b Repair all the unserviceable wiring and connectors.
c Install the FLSCU3 (47QJ) AMM 28-46-34-400-001.
d Do the test given in Para. 3.B.(1).
(10) The 28VDC is shown momentarily, and then after 15 seconds comes back

NOTE: When an ACT manual transfer is selected the initial set sequence relay circuit path is broken after 15 seconds by the action of the RELAY-FAULT SENSE ACT 2 (31QH) (15 second time delay relay).
If during this 15 seconds the ACT 2 inlet valve actuator has failed to go to the fully open position, the sequence relay will de-energize and return to its ACT 1 position.
This is because the ACT 2 inlet valve actuator has failed to supply the required 28VDC latching signal to hold the sequence relay 18QH energized (via relay 14QH).

(a) Remove the multimeter positive lead (+) from the RELAY-PANEL (802VU) test connector 4066VC, pin E and connect to pin P.

NOTE: The RELAY-PANEL (802VU) test connector 4066VC, pin P monitors the relay logic output OPEN command to the ACT 2, inlet valve actuator (5QH2).

(b) Open, then close C/B-10QH.
(c) If the fault continues, replace the RELAY-PANEL (802VU) AMM 25-71-11-000-001 and AMM 25-71-11-400-001.

If there is no relay panel available, go to step (d).

1 Do the test given in the Para. 3.B.
(d) If the 28VDC is not shown at the test connector 4066VC, pin P:

NOTE: This shows the relay logic did not issue an OPEN command to the ACT 2, fuel inlet valve actuator (5QH2).

1 Do a check of ASM 282801 and ASM 282803. Replace, if necessary:

the RELAY-SEQUENCE [18QH]
the RELAY-REFUEL/TRANSFER CONTROL, ACT2 [36QU]
the RELAY-REFUEL INHIBIT, ACT2 [38QU]
the RELAY-INLET VALVE CONTROL, ACT2 [20QH] .

2 Do a check of the RELAY-PANEL (802VU) wiring ASM 282801 and ASM 282803 between the connector to relay and relay to relay wires, as shown in the table that follows:

NOTE: The circuit connections shown in the table are abbreviated, for example:

the connector 4065VC, pin G is shown as 4065VC-G
the RELAY-SEQUENCE (18QH), terminal D1 is shown as RL 18QH-D3.

-----------------------------------------------------------------------------

! CONNECTOR-PIN ! RELAY-TERMINAL TO RELAY-TERMINAL ! CONNECTOR-PIN !

!-----------------------------------------------------------------------------!

! RL 18QH-D1 ----------------- RL 36QU-C3 !

! RL 36QU-C2 ----------------- RL 38QU-A2 !

! RL 38QU-A3 ----------------- RL 20QH-X2 !

! RL 39QU-D2 ----------------- RL 20QH-X1 !

! RL 20QH-C1 ---------------------------------- 4065VC-G !

! RL 20QH-C2 ----------------- RL 36QU-B3 !

! RL 36QU-B2 ----------------- RL 39QU-D2 !

-----------------------------------------------------------------------------

a Repair all the unserviceable wiring and connectors.
b Install the FLSCU3 (47QJ) AMM 28-46-34-400-001.
c Do the test given in Para. 3.B.(1).
(e) If the 28VDC is shown for 15 seconds only at the test connector 4066VC, pin P, do a check of the aircraft wiring ASM 282801 between:

NOTE: This shows the relay logic output commanded the ACT 2 inlet valve actuator to OPEN for the timed (15 second) period. During this time the sequence relay-18QH failed to become latched (held on) and then at the end of the 15 seconds returned to the ACT 1 (de-energized) condition.

the RELAY-PANEL (802VU) free connector 4065VC-A, pin G and the ACT A/C to tank break connector 7619VC2, pin 15
the ACT A/C to tank break free connector 7619VC2-A, pin 15 and the ACTUATOR-FUEL INLET VALVE, ACT 2 (5QH2) free connector 5QH2-A, pin A
the RELAY-PANEL (802VU) free connector 4065VC-A, pin M and the ACT A/C to tank break connector 7619VC2, pin 16
the ACT A/C to tank break free connector 7619VC2-A, pin 16 and the ACTUATOR-FUEL INLET VALVE, ACT 2 (5QH2) free connector 5QH2-A, pin C
the ACT A/C to tank break free connector 7619VC2-A, pin 5 and the ACTUATOR-FUEL INLET VALVE, ACT 2 (5QH2) free connector 5QH2-A, pin E
the ACT A/C to tank break connector 7619VC2, pin 5 and the ground point DC1.

(f) Do a check of and replace, if necessary:
1 The ACTUATOR-FUEL INLET VALVE, ACT2 [5QH2] AMM 28-28-54-000-001 and AMM 28-28-54-400-001.

NOTE: The actuator can drive to the open position (appear serviceable), but unless the internal, end of travel microswitch changes over and supplies the needed sequence relay latch signal, the relay logic will again select the ACT 1 after the 15 seconds time delay.

2 The VALVE-FUEL INLET, ACT2 [166QM2] AMM 28-28-34-000-001 and AMM 28-28-34-400-001.
(g) If the fault continues:
1 Do a check of ASM 282803 and if necessary, replace the diode 4005VD.
a Do a check of the RELAY-PANEL (802VU) wiring ASM 282801 and ASM 282803 between the connector to relay and relay to relay wires, as shown in the table that follows:

NOTE: The circuit connections shown in the table are abbreviated, for example:

the connector 4065VC, pin M is shown as 4065VC-M
the RELAY-SEQUENCE (18QH), terminal A3 is shown as RL 18QH-X1.

-----------------------------------------------------------------------------

! CONNECTOR-PIN ! RELAY-TERMINAL TO RELAY-TERMINAL ! CONNECTOR-PIN !

!-----------------------------------------------------------------------------!

! 4065VC-M -----------(+) via diode (-)----------- RL 18QH-X1 !

-----------------------------------------------------------------------------

b Repair all the unserviceable wiring and connectors.
c Install the FLSCU3 (47QJ) AMM 28-46-34-400-001.
d Do the test given in Para. 3.B.(1).
(11) The 28VDC is shown momentarily, and then after 60 seconds comes back

NOTE: A short circuit to ground on one of the ACT2 low level input wires or the related SDAC1(2) monitor wires will start the 60 seconds time delay of the relay 14QH.
The ACT low level sensors are connected:

in parrallel in a manual ACT fuel transfer
in series in an automatic ACT fuel transfer.

A false ACT2 low level dry signal will cause the sequence relay 18QH to change over to the ACT1 position at the end of the relay 14QH, 60 seconds, Time Delay (TD).

(a) Do a check of the aircraft wiring ASM 282803 between:

the RELAY-PANEL (802VU) free connector 4065VC-A, pin D and the FLSCU3 (47QJ) rack connector AA, pin 4C
the RELAY-PANEL (802VU) free connector 4065VC-A, pin C and the FLSCU3 (47QJ) rack connector AA, pin 10A
the RELAY-PANEL (802VU) free connector 4065VC-A, pin D and the SDAC 1 (1WV1) rack connector AD, pin 14E
the RELAY-PANEL (802VU) free connector 4065VC-A, pin D and the SDAC 2 (1WV2) rack connector AD, pin 14E.

(b) If the fault continues, replace the RELAY-PANEL (802VU) AMM 25-71-11-000-001 and AMM 25-71-11-400-001.

If there is no relay panel available, go to step (c).

1 Do the test given in the Para. 3.B.
(c) If the fault continues:
1 Do a check of ASM 282803 and replace, if necessary:

the [14QH]
the RELAY-AUTO/MANUAL TRANSFER, ACT [23QH] .

a Do a check of the RELAY-PANEL (802VU) wiring ASM 282803 between the connector to relay and relay to relay wires, as shown in the table that follows:

NOTE: The circuit connections shown in the table are abbreviated, for example:

the connector 4065VC, pin D is shown as 4065VC-D
the RELAY-LOW LEVEL SENSE, ACT2 (14QH), terminal X2 is shown as RL 14QH-X2.

-----------------------------------------------------------------------------

! CONNECTOR-PIN ! RELAY-TERMINAL TO RELAY-TERMINAL ! CONNECTOR-PIN !

!-----------------------------------------------------------------------------!

! 4065VC-D --------------------------------------- RL 14QH X2 !

! 4065VC-D --------------------------------------- RL 14QH A2 !

! 4065VC-D --------------------------------------- RL 23QH D1 !

! 4065VC-C --------------------------------------- RL 23QH D2 !

! 4065VC-C ---------------------------------------------------- 4068VC-B !

-----------------------------------------------------------------------------

b Repair all the unserviceable wiring and connectors.
c Install the FLSCU3 (47QJ) AMM 28-46-34-400-001.
d Do the test given in Para. 3.B.(1).

5. Close-up
Subtask 28-28-00-860-051-A ** ON A/C NOT FOR ALL

A. System Configuration
(1) Make sure that the FLSCU-3 (47QJ) is installed AMM 28-46-34-400-001.

[Rev.8 from Aug 2018] 2026.04.04 04:28:51 UTC