Failure of the TCAS

TASK 34-43-00-810-801-A
Failure of the TCAS

1. Possible Causes

CMPTR-TCAS [1SG]
coaxial cables from the antennas (7SG1) and (7SG2) to the TCAS computer (1SG)
ANTENNA-TCAS, TOP [7SG1]
ANTENNA-TCAS, BOTTOM [7SG2]
DATA LOADER RECEPTACLE (194VC)
short to ground at the wiring between the circuit breaker (4SG) and the two units (1SG, 194VC)
C/B-NAV/TCAS
short to ground at the wiring between the circuit breaker (4SG) and the TCAS (1SG)

2. Job Set-up Information
A. Referenced Information

REFERENCE	DESIGNATION
AMM 34-43-00-740-001	BITE Test of the TCAS
ASM 344301
AMM 34-43-11-000-001	Removal of the TCAS Antenna
AMM 34-43-11-400-001	Installation of the TCAS Antenna
AMM 34-43-34-000-001	Removal of the TCAS Computer
AMM 34-43-34-400-001	Installation of the TCAS Computer

3. Fault Confirmation
Subtask 34-43-00-865-065-A

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

PANEL	DESIGNATION	FIN	LOCATION
** ON A/C ALL
121VU	COM NAV/TCAS	4SG	K10

Subtask 34-43-00-740-050-A

B. Test
(1) If the circuit breaker (4SG) trips, refer to Para. 4. C. of this trouble shooting procedure.
(2) Do the BITE test of the TCAS AMM 34-43-00-740-001.

If the BITE test is not possible, refer to Para. 4. B. of this trouble shooting procedure.

4. Fault Isolation
Subtask 34-43-00-810-050-A ** ON A/C NOT FOR ALL

A. If the circuit breaker (4SG) is closed, and if the BITE test gives the maintenance message TCAS (1SG):

replace the CMPTR-TCAS [1SG] AMM 34-43-34-000-001 and AMM 34-43-34-400-001.

Subtask 34-43-00-810-050-D ** ON A/C NOT FOR ALL

A. If the circuit breaker (4SG) is closed, and if the BITE test gives the maintenance message TCAS (1SG):
(1) On the MCDU, on the TCAS menu page, push the line key adjacent to the TROUBLE SHOOT DATA indication to get the TCAS TROUBLE SHOOTING DATA (TSD) page.
(a) If the TSD page does not give the message CABLE CALIBRATION:

replace the CMPTR-TCAS [1SG] AMM 34-43-34-000-001 and AMM 34-43-34-400-001.

(b) If the TSD page gives the message CABLE CALIBRATION:
1 Visually examine the antennas (7SG1) and (7SG2) and their connectors for signs of corrosion or water.
2 Do a check of the coaxial cables from the antennas (7SG1) and (7SG2) to the TCAS computer (1SG) ASM 344301.
a If there is no continuity, repair the related coaxial cable.

if the fault continues, replace the related antenna ANTENNA-TCAS, TOP [7SG1] or ANTENNA-TCAS, BOTTOM [7SG2] AMM 34-43-11-000-001 and AMM 34-43-11-400-001.

b If there is continuity and if there are no signs of corrosion or water:

replace the CMPTR-TCAS [1SG] AMM 34-43-34-000-001 and AMM 34-43-34-400-001.

Subtask 34-43-00-810-051-A

B. If the circuit breaker (4SG) is closed and if the BITE test is not possible

do a check for 115VAC at pin AC/1 of the TCAS.

(1) If there is no 115VAC:

do a check of the wiring of the 115VAC signal from circuit breaker (4SG) to TCAS computer (1SG) ASM 344301.

(a) If there is no continuity:

repair the above wiring.

(b) If there is continuity:

replace the C/B-NAV/TCAS (4SG).

(2) If there is 115VAC:

do a check of the wiring of the ground signal at pin AC/7.

(a) If there is no continuity:

repair the above wiring.

Subtask 34-43-00-810-079-A ** ON A/C NOT FOR ALL

C. If the circuit breaker (4SG) is open:

close this circuit breaker.

(1) If the circuit breaker (4SG) trips:

disconnect these two units:
. CMPTR-TCAS [1SG] AMM 34-43-34-000-001
. DATA LOADER RECEPTACLE (194VC)
close the circuit breaker (4SG).

(a) If this circuit breaker stays closed:

connect the DATA LOADER RECEPTACLE (194VC)

1 If the circuit breaker trips again:

replace the DATA LOADER RECEPTACLE.

2 If the circuit breaker stays closed:

replace the TCAS computer AMM 34-43-34-000-001 and AMM 34-43-34-400-001

(b) If this circuit breaker trips again:

do a check for a short to ground at the wiring between the circuit breaker (4SG) and the two units (1SG, 194VC) ASM 344301.

1 If there is a short to ground:

repair the above wiring.

2 If there is no short to ground:

replace the C/B-NAV/TCAS.

3 Install these two units:

TCAS computer AMM 34-43-34-400-001
DATA LOADER RECEPTACLE (194VC).

Subtask 34-43-00-810-079-F ** ON A/C NOT FOR ALL

C. If the circuit breaker (4SG) is open:

close this circuit breaker.

(1) If the circuit breaker (4SG) trips:

disconnect the: CMPTR-TCAS [1SG] AMM 34-43-34-000-001
close the circuit breaker (4SG).

(a) If this circuit breaker stays closed:

replace the TCAS computer AMM 34-43-34-000-001 and AMM 34-43-34-400-001

(b) If this circuit breaker trips again:

do a check for a short to ground at the wiring between the circuit breaker (4SG) and the TCAS (1SG) ASM 344301.

1 If there is a short to ground:

repair the above wiring.

2 If there is no short to ground:

replace the C/B-NAV/TCAS.

3 Install the TCAS computer AMM 34-43-34-400-001

Subtask 34-43-00-740-051-A

D. Do the test given in Para. 3.

[Rev.8 from Aug 2018] 2026.04.04 04:33:11 UTC