Loss of the message bus RS422 between the FWC 1 and the DMC 3

TASK 31-63-00-810-958-A
Loss of the message bus RS422 between the FWC 1 and the DMC 3

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 31-63-00-865-187-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 31-63-00-740-326-A ** ON A/C NOT FOR ALL

B. Test
Do the EIS input test (EIS 3) AMM 31-60-00-740-002.

Subtask 31-63-00-740-326-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 31-63-00-810-206-A ** ON A/C NOT FOR ALL

A. If the test gives the maintenance message:
DMC 3 : 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 3 (1WT3) pins AB/14J, 14K to pins AA/9C, 9D ASM 315205.

Subtask 31-63-00-810-206-B ** ON A/C NOT FOR ALL

A. If the test gives the maintenance message:
FWC1(1WW1) BUS MESSAGEX/DMC3(1WT3)

(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 3 (1WT3) pins AB/14J, 14K to pins AD/5G, 5H ASM 315205.

Subtask 31-63-00-740-327-A

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

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