Failure of the 1553 Data Bus between GCU 1 and GAPCU

TASK 24-22-00-810-829-A
Failure of the 1553 Data Bus between GCU 1 and GAPCU

1. Possible Causes

2. Job Set-up Information
A. Referenced Information

REFERENCE	DESIGNATION
AMM 24-22-34-000-001	Removal of the GCU-1(2)
AMM 24-22-34-400-001	Installation of the GCU-1(2)
ASM 242302
AMM 24-41-00-740-002	Operational Check of the GAPCU via the CFDS
AMM 24-41-34-000-001	Removal of the Ground Power Control Unit (GPCU)
AMM 24-41-34-400-001	Installation of the Ground Power Control Unit (GPCU)

3. Fault Confirmation
Subtask 24-22-00-740-075-A ** ON A/C NOT FOR ALL

A. Test
(1) Do the BITE test of the GAPCU AMM 24-41-00-740-002.

4. Fault Isolation
Subtask 24-22-00-810-084-A ** ON A/C NOT FOR ALL

A. If the BITE test gives the maintenance message GCU1 (1XU1) 1553 BUS/ GAPCU (24XG):

(1) If the fault continues:

(2) If the fault continues:

do a check and repair the wiring of the 1553 data bus ASM 242302 for an open circuit, a short to ground, a short to shield or a short circuit between:
. pin A/6J of the GCU 1 and pin A/11E of the GAPCU
. pin A/6H of the GCU 1 and pin A/12E of the GAPCU
. pins A/11E and A/10E of the GAPCU (short to shield)
. pins A/12E and A/10E of the GAPCU (short to shield).

Subtask 24-22-00-740-076-A ** ON A/C NOT FOR ALL

B. Do the test given in Para. 3.

[Rev.8 from Aug 2018] 2026.04.04 04:26:38 UTC