A/THR Engagement Inoperative after Installation of the New FMGC

TASK 22-31-00-810-803-A
A/THR Engagement Inoperative after Installation of the New FMGC

1. Possible Causes

wiring of the ATH INST DISC NO and ATH INST DISC NC discretes (from the FMGC 1 (1CA1) to the two relays (5CA1 and 5CA2))
wiring of the ATH OWN ENGD COM OPP discrete on the FMGC 1 (1CA1)
wiring of the ATH OWN ENGD COM OWN discrete on the FMGC 1 (1CA1)
FCU [2CA]
wiring of the A/THR 1 SW COM discrete from the FCU (2CA) to the FMGC 1 (1CA1)
wiring of the ATH OWN ENGD MON OPP discrete on the FMGC 1 (1CA1)
wiring of the ATH OWN ENGD MON OWN discrete on the FMGC 1 (1CA1)
wiring of the A/THR 1 SW MON discrete from the FCU (2CA) to the FMGC 1 (1CA1)
wiring of the ATH INST DISC NO and ATH INST DISC NC discretes (from the FMGC 2 (1CA2) to the first terminal block)
wiring of the ATH OWN ENGD COM OPP discrete on the FMGC 2 (1CA2)
wiring of the ATH OWN ENGD COM OWN discrete on the FMGC 2 (1CA2)
wiring of the A/THR 2 SW COM discrete from the FCU (2CA) to the FMGC 2 (1CA2)
wiring of the ATH OWN ENGD MON OPP discrete on the FMGC 2 (1CA2)
wiring of the ATH OWN ENGD MON OWN discrete on the FMGC 2 (1CA2)
wiring of the A/THR 2 SW MON discrete from the FCU (2CA) to the FMGC 2 (1CA2)

2. Job Set-up Information
A. Referenced Information

REFERENCE	DESIGNATION
AMM 22-30-00-710-003	Operational Test of the Engine / Autothrust System Isolation (with AIDS)
ASM 223101
AMM 22-81-12-000-001	Removal of the FCU
AMM 22-81-12-400-001	Installation of the FCU
AMM 22-96-00-710-001	Operational Test of the AFS
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 34-10-00-860-004	IR Alignment Procedure

3. Fault Confirmation
Subtask 22-31-00-860-050-A

A. Job Set-up
(1) Aircraft Maintenance Configuration
(a) Energize the aircraft electrical circuits
AMM 24-41-00-861-002.
(b) Do the IR alignment procedure AMM 34-10-00-860-004.
(c) On the Flight Control Unit (FCU), make sure that the pushbutton switches AP 1 and AP 2 are not engaged (the two pushbutton switches are off).
(d) On the FCU, make sure that the pushbutton switches FD 1 and FD 2 are engaged (the two pushbutton switches are on).

Subtask 22-31-00-865-052-A

B. Make sure that this(these) circuit breaker(s) is(are) closed:

PANEL	DESIGNATION	FIN	LOCATION
** ON A/C ALL
49VU	AUTO FLT/FCU/1	9CA1	B05
49VU	AUTO FLT/FMGC/1	10CA1	B02
121VU	AUTO FLT/FCU/2	9CA2	M21
121VU	AUTO FLT/FMGC/2	10CA2	M17

Subtask 22-31-00-710-054-A

C. Test
(1) Do this test:

ACTION	RESULT
1.On the FCU:
Push the FD 2 pushbutton switch.	The FD 2 pushbutton switch goes off.
Pull the SPD MACH selector knob.
Make sure that a speed is displayed on the SPD display on the FCU.
Push the A/THR pushbutton switch.	The A/THR pushbutton switch comes on.
Push the A/THR pushbutton switch.	The A/THR pushbutton switch goes off.
2.On the FCU:
Push the FD 1 and FD 2 pushbutton switches.	The FD 1 pushbutton switch goes off and the FD 2 pushbutton switch comes on.
Make sure that a speed is displayed on the SPD display on the FCU.
Push the A/THR pushbutton switch.	The A/THR pushbutton switch comes on.

(2) If the A/THR pushbutton switch does not engage after you try to engage it two times:

Do the operational test of the engine/autothrust system isolation AMM 22-30-00-710-003.

4. Fault Isolation
Subtask 22-31-00-810-052-A

A. If the A/THR does not engage when you open the circuit breaker 10CA2 only:

do the operational test of the AFS AMM 22-96-00-710-001 and read the result for the FMGC 1.

(1) If the test gives the maintenance message AFS : FMGC 1/ATHR DISC CKT:

do a check and repair the wiring of the ATH INST DISC NO and ATH INST DISC NC discretes (from the FMGC 1 (1CA1) to the two relays (5CA1 and 5CA2)) ASM 223101.

(2) If the test gives the message LRU TEST NOT COMPLETED:

push the line key adjacent to the RETURN indication until the AFS MAIN MENU page comes into view
push the line key adjacent to the TROUBLE SHOOTING DATA indication
push the line key adjacent to the FG 1 COM indication, then FG 1 MON indication:
. make sure that there is a snapshot related to an event 1 at AFS TEST time
on word 5, make sure that the third number is equal to:
. 1 or 3 or 5 or 7 or 9 or B or D or F (on command and monitoring channels).

(a) If the third number is not equal to the above values on the command channel:

do a check of the wiring of the ATH OWN ENGD COM OPP discrete on the FMGC 1 (1CA1) (from pin AA/14D to pin AB/1D)
do a check of the wiring of the ATH OWN ENGD COM OWN discrete on the FMGC 1 (1CA1) (from pin AB/12D to pin AB/1F)
ASM 223101.

1 If there is no continuity:

repair the above wiring.

2 If there is continuity:

replace the FCU [2CA] AMM 22-81-12-000-001 and AMM 22-81-12-400-001.

a If the fault continues:

do a check and repair the wiring of the A/THR 1 SW COM discrete from the FCU (2CA) to the FMGC 1 (1CA1) ASM 223101.

(b) If the third number is not equal to the above values on the monitor channel:

do a check of the wiring of the ATH OWN ENGD MON OPP discrete on the FMGC 1 (1CA1) (from pin AD/14F to pin AE/1D)
do a check of the wiring of the ATH OWN ENGD MON OWN discrete on the FMGC 1 (1CA1) (from pin AE/12E to pin AE/1F)

ASM 223101.
1 If there is no continuity:

repair the above wiring.

2 If there is continuity:

replace the FCU [2CA] AMM 22-81-12-000-001 and AMM 22-81-12-400-001.

a If the fault continues:

do a check and repair the wiring of the A/THR 1 SW MON discrete from the FCU (2CA) to the FMGC 1 (1CA1) ASM 223101.

Subtask 22-31-00-810-064-A

B. If the A/THR does not engage when you open the circuit breaker 10CA1 only:

do the operational test of the AFS AMM 22-96-00-710-001 and read the result for the FMGC 2.

(1) If the test gives the maintenance message AFS : FMGC 2/ATHR DISC CKT:

do a check and repair the wiring of the ATH INST DISC NO and ATH INST DISC NC discretes (from the FMGC 2 (1CA2) to the first terminal block) ASM 223101.

(2) If the test gives the message LRU TEST NOT COMPLETED:

push the line key adjacent to the RETURN indication until the AFS MAIN MENU page comes into view
push the line key adjacent to the TROUBLE SHOOTING DATA indication
push the line key adjacent to the FG 2 COM indication, then FG 2 MON indication:
. make sure that there is a snapshot related to an event 1 at AFS TEST time
on word 5, make sure that the third number is equal to:
. 1 or 3 or 5 or 7 or 9 or B or D or F (on command and monitoring channels).

(a) If the third number is not equal to the above values on the command channel:

do a check of the wiring of the ATH OWN ENGD COM OPP discrete on the FMGC 2 (1CA2) (from pin AA/14D to pin AB/1D)
do a check of the wiring of the ATH OWN ENGD COM OWN discrete on the FMGC 2 (1CA2) (from pin AB/12D to pin AB/1F)

ASM 223101.
1 If there is no continuity:

repair the above wiring.

2 If there is continuity:

replace the FCU [2CA] AMM 22-81-12-000-001 and AMM 22-81-12-400-001.

a If the fault continues:

do a check and repair the wiring of the A/THR 2 SW COM discrete from the FCU (2CA) to the FMGC 2 (1CA2) ASM 223101.

(b) If the third number is not equal to the above values on the monitor channel:

do a check of the wiring of the ATH OWN ENGD MON OPP discrete on the FMGC 2 (1CA2) (from pin AD/14F to pin AE/1D)
do a check of the wiring of the ATH OWN ENGD MON OWN discrete on the FMGC 2 (1CA2) (from pin AE/12E to pin AE/1F)

ASM 223101.
1 If there is no continuity:

repair the above wiring.

2 If there is continuity:

replace the FCU [2CA] AMM 22-81-12-000-001 and AMM 22-81-12-400-001.

a If the fault continues:

do a check and repair the wiring of the A/THR 2 SW MON discrete from the FCU (2CA) to the FMGC 2 (1CA2) ASM 223101.

Subtask 22-31-00-710-055-A

C. Do the test given in Para. 3.C.(2).

5. Close-up
Subtask 22-31-00-860-051-A

A. Put the aircraft back to its initial configuration.
(1) De-energize the aircraft electrical circuits
AMM 24-41-00-862-002.

[Rev.8 from Aug 2018] 2026.04.04 04:25:08 UTC