Loss of the message bus RS422 between the FWC 1 and the DMC 1

TASK 31-63-00-810-956-A
Loss of the message bus RS422 between the FWC 1 and the DMC 1

1. Possible Causes

2. Job Set-up Information
A. Referenced Information

REFERENCE	DESIGNATION
ASM 315205
AMM 31-53-34-000-001	Removal of the Flight Warning Computer (FWC)
AMM 31-53-34-400-001	Installation of the Flight Warning Computer (FWC)
AMM 31-60-00-740-002	Perform Electronic Instrument System (EIS) Input Test
AMM 31-60-00-740-007	GROUND SCANNING Test of the DMC
AMM 31-63-34-000-001	Removal of the DMC
AMM 31-63-34-400-001	Installation of the DMC

3. Fault Confirmation
Subtask 31-63-00-865-185-A

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

PANEL	DESIGNATION	FIN	LOCATION
** ON A/C ALL
49VU	FWS/FWC1/SPLY	3WW	F01

Subtask 31-63-00-740-322-A ** ON A/C NOT FOR ALL

B. Test
Do the EIS input test (EIS 1) AMM 31-60-00-740-002.

Subtask 31-63-00-740-322-B ** ON A/C NOT FOR ALL

B. Test
Do the Ground Scanning Test of the DMC AMM 31-60-00-740-007.

4. Fault Isolation
Subtask 31-63-00-810-204-A ** ON A/C NOT FOR ALL

A. If the test gives the maintenance message:
DMC 1 : NO FWC 1 MSG

(1) If the fault continues:

(a) If the fault continues:

do a check and repair the wiring from the FWC 1 (1WW1) to the DMC 1 (1WT1) pins AB/14F, 14G to pins AA/9D, 9C ASM 315205.

Subtask 31-63-00-810-204-B ** ON A/C NOT FOR ALL

A. If the test gives the maintenance message:
FWC1(1WW1) BUS MESSAGEX/DMC1(1WT1)

(1) If the fault continues:

(a) If the fault continues:

do a check and repair the wiring from the FWC 1 (1WW1) to the DMC 1 (1WT1) pins AB/14F, 14G to pins AD/5G, 5H ASM 315205.

Subtask 31-63-00-740-323-A

B. Do the test given in Para. 3.B.

[Rev.8 from Aug 2018] 2026.04.04 04:30:49 UTC