Heading Discrepancy Warning on the Upper ECAM Display Unit

TASK 34-14-00-810-891-A
Heading Discrepancy Warning on the Upper ECAM Display Unit

1. Possible Causes

DMC-1 [1WT1]
wiring of the INERTIAL REFERENCE OUTPUT BUS 1 bus from the ADIRU1 (1FP1) to the DMC1 (1WT1)
ADIRU-1 [1FP1]
DMC-2 [1WT2]
wiring of the INERTIAL REFERENCE OUTPUT BUS 1 bus from the ADIRU2 (1FP2) to the DMC2 (1WT2)
ADIRU-2 [1FP2]

2. Job Set-up Information
A. Referenced Information

REFERENCE	DESIGNATION
AMM 31-63-34-000-001	Removal of the DMC
AMM 31-63-34-400-001	Installation of the DMC
AMM 34-12-34-000-001	Removal of the ADIRU
AMM 34-12-34-400-001	Installation of the ADIRU
ASM 341401

3. Fault Confirmation
Subtask 34-14-00-710-081-A

A. Test
(1) Not applicable, the fault is evident.

4. Fault Isolation
Subtask 34-14-00-810-143-A

A. If the NAV HDG DISCREPANCY message comes into view on the upper ECAM DU:

make sure that the CHECK HDG message is in view on the CAPT ND or on the F/O ND.

(1) If the CHECK HDG message is in view on the CAPT ND:

on the center pedestal, on the SWITCHING panel 8VU, set the EIS DMC selector switch to CAPT 3.

(a) If the messages go out of view:

replace the DMC-1 [1WT1] AMM 31-63-34-000-001 and AMM 31-63-34-400-001.

1 If the fault continues:

do a check of the wiring of the INERTIAL REFERENCE OUTPUT BUS 1 bus from the ADIRU1 (1FP1) to the DMC1 (1WT1) ASM 341401.

a If there is no continuity:

repair the above wiring.

b If there is continuity:

replace the ADIRU-1 [1FP1] AMM 34-12-34-000-001 and AMM 34-12-34-400-001.

(b) If the messages stay in view:

replace the ADIRU-1 [1FP1] AMM 34-12-34-000-001 and AMM 34-12-34-400-001.

(2) If the CHECK HDG message is in view on the F/O ND:

on the center pedestal, on the SWITCHING panel 8VU, set the EIS DMC selector switch to F/O 3.

(a) If the messages go out of view:

replace the DMC-2 [1WT2] AMM 31-63-34-000-001 and AMM 31-63-34-400-001.

1 If the fault continues:

do a check of the wiring of the INERTIAL REFERENCE OUTPUT BUS 1 bus from the ADIRU2 (1FP2) to the DMC2 (1WT2) ASM 341401.

a If there is no continuity:

repair the above wiring.

b If there is continuity:

replace the ADIRU-2 [1FP2] AMM 34-12-34-000-001 and AMM 34-12-34-400-001.

(b) If the messages stay in view:

replace the ADIRU-2 [1FP2] AMM 34-12-34-000-001 and AMM 34-12-34-400-001.

5. Close-up
Subtask 34-14-00-860-063-A

A. Put the aircraft back to its initial configuration.
(1) On the center pedestal, on the SWITCHING panel 8VU, set the EIS DMC selector switch to NORM.

[Rev.8 from Aug 2018] 2026.04.04 04:32:48 UTC