DOC AIRBUS | TSM A320FAutothrust Instinctive Disconnect Hardwired Discrete Signal Failure Channel A
TASK 76-11-00-810-824-A
Autothrust Instinctive Disconnect Hardwired Discrete Signal Failure Channel A
1. Possible Causes
A. Fixtures, Tools, Test and Support Equipment
B. Referenced Information
3. Fault Confirmation
Subtask 76-11-00-710-092-A ** ON A/C NOT FOR ALL
Subtask 76-11-00-860-050-A ** ON A/C NOT FOR ALL
[Rev.8 from Aug 2018]
2026.04.04 04:40:50 UTC
Autothrust Instinctive Disconnect Hardwired Discrete Signal Failure Channel A
1. Possible Causes
- HARNESS-FAN, WF02 [4218KS]
- RELAY-A/THR1 INST DISC [5CA1]
- RELAY-A/THR2 INST DISC [5CA2]
- aircraft wiring
[4000KS]
A. Fixtures, Tools, Test and Support Equipment
| REFERENCE | QTY | DESIGNATION |
|---|---|---|
| No specific | 1 | MULTIMETER - STANDARD |
| No specific | 1 | PLIERS - JAWED, SOFT |
| REFERENCE | DESIGNATION |
|---|---|
| TSM TASK 71-00-00-810-834-A | General Troubleshooting Guidelines for Additional Troubleshooting Information |
| TSM TASK 71-00-00-810-835-A | Component and Harness Intermittent Troubleshooting Procedure for Guidance Troubleshooting Intermittent Faults |
| 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 70-70-00-910-803 | SPOP 6 - Cleaning of the Contact Points and Wiring Harnesses |
| AMM 71-13-00-010-802 | Opening of the Fan Cowl Doors |
| AMM 71-13-00-410-802 | Closing of the Fan Cowl Doors |
| AMM 73-21-01-000-801 | Removal of the Electronic Engine Control (EEC) |
| AMM 73-21-01-400-801 | Installation of the Electronic Engine Control (EEC) |
| AMM 73-21-62-000-802 | Removal of the EEC Wiring Harness (WF02) |
| AMM 73-21-62-400-802 | Installation of the EEC Wiring Harness (WF02) |
| AWM 732523 | |
EEC Wiring HarnessesSubtask 76-11-00-710-092-A ** ON A/C NOT FOR ALL
A. Energize the FADEC of the engine that has a fault report.
(1) Energize the aircraft electrical circuits AMM 24-41-00-861-002.
(2) On the ENG section of maintenance panel 50VU:
(a) Release the FADEC GND PWR/1(2) pushbutton switch (the ON legend comes on).
(a) If no problems are found, return the engine to service. Monitor the engine for reoccurring maintenance message.
(5) If the maintenance message comes back (hard fault), go to the Para. Fault Isolation.
4. Fault Isolation(1) Energize the aircraft electrical circuits AMM 24-41-00-861-002.
(2) On the ENG section of maintenance panel 50VU:
(a) Release the FADEC GND PWR/1(2) pushbutton switch (the ON legend comes on).
NOTE: After the FADEC is energized, wait ten seconds before you start the test. If you do not wait ten seconds, the interactive mode stops the EEC self-test and this can cause spurious faults.
(3) On Multipurpose Control and Display Unit (MCDU) screen, check if the fault is displayed on ground scanning report. NOTE: The Electronic Engine Control (EEC) has detected the autothrust instinctive disconnect discrete circuit for the flight control unit is out of range or rate in channel A. The autothrust instinctive disconnect discrete circuit is activated by a push button on the flight control unit.
(4) If the maintenance message does not come back, examine the harness and electrical connectors as described in the component and harness intermittent fault isolation procedure (Ref. TSM TASK 71-00-00-810-835). - Refer to the general troubleshooting guidelines for additional troubleshooting information (Ref. TSM TASK 71-00-00-810-834).
- Refer to the component and harness intermittent troubleshooting procedure for guidance troubleshooting intermittent faults (Ref. TSM TASK 71-00-00-810-835).
(a) If no problems are found, return the engine to service. Monitor the engine for reoccurring maintenance message.
(5) If the maintenance message comes back (hard fault), go to the Para. Fault Isolation.
WARNING:
BE CAREFUL WHEN YOU DO WORK ON THE ENGINE AFTER SHUTDOWN. THE ENGINE CAN STAY HOT FOR A LONG TIME. IF YOU DO NOT OBEY THIS WARNING, INJURY CAN OCCUR.
WARNING:
REFER TO THE MSDS FOR ALL MATERIAL USED AND THE MANUFACTURER'S SAFETY INSTRUCTIONS FOR ALL EQUIPMENT USED. IF YOU DO NOT OBEY THIS WARNING, INJURY CAN OCCUR.
CAUTION:
MAKE SURE YOU REMOVE ELECTRICAL POWER FROM THE EEC BEFORE YOU REMOVE THE ELECTRICAL CONNECTORS. IF YOU DO NOT OBEY THIS INSTRUCTION, DAMAGE TO THE EEC CAN OCCUR.
Subtask 76-11-00-810-078-A ** ON A/C NOT FOR ALL A. If there is confirmation of the fault:
(1) Open the fan cowl-doors AMM 71-13-00-010-802.
(2) Examine the WF02 (4218KS) harness, connector P1 (4000KS-P1) - EEC (4000KS) and connector P406 (406VC-A) - pylon junction box, for problems which are possible between the EEC (4000KS) and the pylon junction box.
(a) Inspect for harness damage.
(b) Inspect for loose or damaged connectors.
1 Replace HARNESS-FAN, WF02 [4218KS] AMM 73-21-62-000-802 and AMM 73-21-62-400-802.
2 Do the test given in Para. 3.
(3) If no problems are found with the harness or the fault continues, use a PLIERS - JAWED, SOFT to disconnect the electrical connector P1 (4000KS-P1) from the EEC (4000KS) and connector P406 (406VC-A) from the pylon junction box.
(a) Examine the pins and sockets (contacts) for alignment and damage. Look for contacts pushed rearward into the connector face. Replace parts as necessary.
(b) Clean the contacts with contact cleaner and clean cloth per SPOP 6. Blow dry with air (at less than 30 psi) across the connector face AMM 70-70-00-910-803.
(c) Reconnect the electrical connector P1 (4000KS-P1) to the EEC (4000KS) and connector P406 (406VC-A) to the pylon junction box.
(d) Do the test given in Para. 3.
(4) If the fault continues:
(a) Disconnect the electrical connector P1 (4000KS-P1) from the EEC (4000KS) and connector P406 (406VC-A) from the pylon junction box. Use a MULTIMETER - STANDARD to test the autothrust instinctive disconnect discrete circuits in the harness. Refer to Table 1. Look for:
1 Wire-to-wire shorts
2 Shorts to ground
3 Continuity (less than 5 ohms resistance).
(b) If a problem is found with the harness or connectors:
1 Replace HARNESS-FAN, WF02 [4218KS] AMM 73-21-62-000-802 and AMM 73-21-62-400-802.
2 Do the test given in Para. 3.
(5) If no problems are found with the harness or connectors, check the aircraft circuits for the autoflight instinctive disconnect discrete AWM 732523.
(a) On the relay plate 187VU, replace RELAY-A/THR1 INST DISC [5CA1] and RELAY-A/THR2 INST DISC [5CA2] AWM 732523.
(b) Do the test given in Para. 3.
(c) If fault continues, check for aircraft wiring continuity:
1 On throttle control lever, make sure that both A/THR instinctive disconnect pushbutton switches (7CA1) and (7CA2) are released.
2 Check for continuity between pins 6 and 7:
a At 406VC1 for fault on ENG 1.
b At 406VC2 for fault on ENG 2.
(d) Repair any problems found.
(e) Do the test given in Para. 3.
(6) If the fault continues:
(a) Replace
(b) Do the test given in Para. 3.
5. Close-up(1) Open the fan cowl-doors AMM 71-13-00-010-802.
(2) Examine the WF02 (4218KS) harness, connector P1 (4000KS-P1) - EEC (4000KS) and connector P406 (406VC-A) - pylon junction box, for problems which are possible between the EEC (4000KS) and the pylon junction box.
(a) Inspect for harness damage.
(b) Inspect for loose or damaged connectors.
NOTE: Loose connectors must be disconnected and examined for further wear or damage.
(c) If a problem is found with the harness or connectors: 1 Replace HARNESS-FAN, WF02 [4218KS] AMM 73-21-62-000-802 and AMM 73-21-62-400-802.
2 Do the test given in Para. 3.
(3) If no problems are found with the harness or the fault continues, use a PLIERS - JAWED, SOFT to disconnect the electrical connector P1 (4000KS-P1) from the EEC (4000KS) and connector P406 (406VC-A) from the pylon junction box.
(a) Examine the pins and sockets (contacts) for alignment and damage. Look for contacts pushed rearward into the connector face. Replace parts as necessary.
(b) Clean the contacts with contact cleaner and clean cloth per SPOP 6. Blow dry with air (at less than 30 psi) across the connector face AMM 70-70-00-910-803.
(c) Reconnect the electrical connector P1 (4000KS-P1) to the EEC (4000KS) and connector P406 (406VC-A) to the pylon junction box.
(d) Do the test given in Para. 3.
(4) If the fault continues:
(a) Disconnect the electrical connector P1 (4000KS-P1) from the EEC (4000KS) and connector P406 (406VC-A) from the pylon junction box. Use a MULTIMETER - STANDARD to test the autothrust instinctive disconnect discrete circuits in the harness. Refer to Table 1. Look for:
1 Wire-to-wire shorts
2 Shorts to ground
3 Continuity (less than 5 ohms resistance).
NOTE: A short to ground is found when the resistance is less than 100 000 (100K) ohms.
Table 1: Autothrust Instinctive Disconnect Discrete Channel A Connector Contacts | WF02 (4218KS) Harness P1 (4000KS-P1) EEC (4000KS) Connector Contacts | WF02 (4218KS) Harness P406 (406VC-A) Pylon Junction Box Connector Contacts |
|---|---|
| LL | 7 |
| PP | 6 |
1 Replace HARNESS-FAN, WF02 [4218KS] AMM 73-21-62-000-802 and AMM 73-21-62-400-802.
2 Do the test given in Para. 3.
(5) If no problems are found with the harness or connectors, check the aircraft circuits for the autoflight instinctive disconnect discrete AWM 732523.
(a) On the relay plate 187VU, replace RELAY-A/THR1 INST DISC [5CA1] and RELAY-A/THR2 INST DISC [5CA2] AWM 732523.
(b) Do the test given in Para. 3.
(c) If fault continues, check for aircraft wiring continuity:
1 On throttle control lever, make sure that both A/THR instinctive disconnect pushbutton switches (7CA1) and (7CA2) are released.
2 Check for continuity between pins 6 and 7:
a At 406VC1 for fault on ENG 1.
b At 406VC2 for fault on ENG 2.
(d) Repair any problems found.
(e) Do the test given in Para. 3.
(6) If the fault continues:
(a) Replace
(b) Do the test given in Para. 3.
Subtask 76-11-00-860-050-A ** ON A/C NOT FOR ALL
A. Put the aircraft back to its initial configuration.
(1) Make sure that the work area is clean and clear of tools and other items.
(a) Close the fan cowl-doors AMM 71-13-00-410-802.
(b) De-energize the aircraft electrical circuits AMM 24-41-00-862-002.
(1) Make sure that the work area is clean and clear of tools and other items.
(a) Close the fan cowl-doors AMM 71-13-00-410-802.
(b) De-energize the aircraft electrical circuits AMM 24-41-00-862-002.