Altitude Discrepancy Warning on the Upper ECAM Display Unit

TASK 34-13-00-810-924-A
Altitude Discrepancy Warning on the Upper ECAM Display Unit

1. Possible Causes

DMC-1 [1WT1]
wiring of the AIR DATA OUTPUT BUS1 bus from the ADIRU1 (1FP1) to the DMC1 (1WT1)
ADIRU-1 [1FP1]
DMC-2 [1WT2]
wiring of the AIR DATA OUTPUT BUS1 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 341301

3. Fault Confirmation

NOTE: Before you do this procedure, make sure that the two baro displays on the FCU are on the same scale (BARO, STD) and show the same indication. If there is a differential altitude between CAPT PFD and F/O PFD > 300ft: the CHECK ALT message is shown on the two PFDs with related NAV ALTI DISCREPANCY warning when the two baro displays are QNH or QFE, the NAV BARO REF DISCREPANCY message is shown one the two PFDs when one baro display is in QNH and the other one in QFE.

Subtask 34-13-00-710-145-A

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

4. Fault Isolation
Subtask 34-13-00-810-174-A

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

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

(1) If the CHECK ALT message is in view on the CAPT PFD:

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 AIR DATA OUTPUT BUS1 bus from the ADIRU1 (1FP1) to the DMC1 (1WT1) ASM 341301.

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 ALT message is in view on the F/O PFD:

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 AIR DATA OUTPUT BUS1 bus from the ADIRU2 (1FP2) to the DMC2 (1WT2) ASM 341301.

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 34-13-00-860-062-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 04:32:28 UTC