Failure of the GCU 1 Air/Ground Status

TASK 24-20-00-810-878-A
Failure of the GCU 1 Air/Ground Status

1. Possible Causes

GCU-1 [1XU1]
wiring
LGCIU-1 [5GA1]

2. Job Set-up Information
A. Referenced Information

REFERENCE	DESIGNATION
ASM 242201
AMM 24-22-34-000-001	Removal of the GCU-1(2)
AMM 24-22-34-400-001	Installation of the GCU-1(2)
AMM 24-41-00-740-002	Operational Check of the GAPCU via the CFDS
AMM 32-31-71-000-001	Removal of the LGCIU
AMM 32-31-71-400-001	Installation of the LGCIU

3. Fault Confirmation
Subtask 24-20-00-740-070-A ** ON A/C NOT FOR ALL

A. Test
(1) Do the BITE test of the GAPCU AMM 24-41-00-740-002.
(a) If the BITE test gives the message TEST FAILED:

do the trouble shooting given in Para 4.B.

(b) If the BITE test gives the message TEST PASSED:

do the trouble shooting given in Para 4.C.

4. Fault Isolation
Subtask 24-20-00-865-066-A ** ON A/C NOT FOR ALL

A. Table of the circuit breakers used in this procedure:

PANEL	DESIGNATION	FIN	LOCATION
** ON A/C NOT FOR ALL
49VU	L/G/LGCIU/SYS1/NORM	1GA	C09
49VU	FWS/FWC1/SPLY	3WW	F01
121VU	HYDRAULIC/LGCIU/SYS2	2GA	Q35
121VU	HYDRAULIC/LGCIU/SYS1/GRND SPLY	52GA	Q34
121VU	EIS/FWC2/SPLY	2WW	Q07

Subtask 24-20-00-810-192-A ** ON A/C NOT FOR ALL

B. If the BITE test gives the message TEST FAILED:

push the line key adjacent to the TEST FAILED message.

(1) If the maintenance message GCU1 (1XU1) comes into view with AC GEN maintenance status:

NOTE: The AC GEN maintenance status can appear during ATA 32 maintenance action. To make sure that it is an unwanted warning, do the steps that follow to do a reset of the LGCIU 1(2) and FWC 1(2) to clear the warning.

(a) Open circuit breakers 52GA, 1GA and 2GA.

Wait for 30 seconds and make sure that on the upper ECAM display unit and STATUS pages, fault warnings come into view.

(b) Open circuit breakers 3WW and 2WW.

Wait for 30 seconds.

Wait for 30 seconds.

(d) Close circuit breakers 3WW and 2WW.

Make sure that the AC GEN maintenance status is no longer shown on the upper ECAM display unit.
If the AC GEN maintenance status continues to be shown, replace the GCU-1 [1XU1] AMM 24-22-34-000-001 and AMM 24-22-34-400-001.

(2) If the maintenance message GCU1 (1XU1) comes into view without AC GEN maintenance status:

replace the GCU-1 [1XU1] AMM 24-22-34-000-001 and AMM 24-22-34-400-001.

Subtask 24-20-00-810-166-A ** ON A/C NOT FOR ALL

C. If the BITE test gives the message TEST PASSED:
(1) Do the trouble shooting for chapter-32 CFDS messages related to the LGCIU 1.
(2) If there are no CFDS messages related to the LGCIU 1:

do a check of the ground/flight status wiring for a short circuit or a short to ground between pin A/2C of the GCU 1 and pin B/9E of the LGCIU 1 (5GA1) ASM 242201.

(a) If there is no continuity:

repair or replace as necessary.

(b) If there is continuity:

replace the GCU-1 [1XU1] AMM 24-22-34-000-001 and AMM 24-22-34-400-001.

1 If the fault continues:

replace the LGCIU-1 [5GA1] AMM 32-31-71-000-001 and AMM 32-31-71-400-001.

Subtask 24-20-00-740-071-A ** ON A/C NOT FOR ALL

D. Do the test given in Para. 3.

[Rev.8 from Aug 2018] 2026.04.04 04:26:17 UTC