Failure of the TCAS Bottom Antenna

TASK 34-43-00-810-808-A
Failure of the TCAS Bottom Antenna

1. Possible Causes

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 34-43-00-740-059-A

A. Test
Do the BITE test of the TCAS AMM 34-43-00-740-001.

4. Fault Isolation
Subtask 34-43-00-810-058-A ** ON A/C NOT FOR ALL

A. If the test gives the maintenance message TCAS BOT ANTENNA (7SG2)

do a check of the coaxial cables from the bottom antenna (7SG2) to the TCAS computer (1SG) ASM 344301.

(1) If there is no continuity:

(2) If there is continuity:

make sure that there is discontinuity between the core and the shield of the coaxial cable (J1, J2, J3 and/or J4)

(a) If there is continuity:

(b) If there is no continuity:

1 If the fault continues:

Subtask 34-43-00-810-058-F ** ON A/C NOT FOR ALL

A. If the test gives the maintenance message TCAS BOT ANTENNA (7SG2):

(1) Do a check of the resistances of the coaxial cables J1, J2, J3 and J4 between:

The core and the shield of the coaxial cable J1 (1000 ohms +/- 100 ohms)
The core and the shield of the coaxial cable J2 (8060 ohms +/- 800 ohms)
The core and the shield of the coaxial cable J3 (4020 ohms +/- 400 ohms)
The core and the shield of the coaxial cable J4 (2000 ohms +/- 200 ohms)
ASM 344301.

(a) If the resistance values are in the specified limits:

(b) If one or more of the resistance value(s) is (are) out of the specified limits:

1 Disconnect the related coaxial cable(s) from the TCAS bot antenna (7SG2)

Do a check of the related connector(s) for moisture:
- If there is moisture, dry and clean the connector(s)
Do a check of the resistance at the related TCAS bot antenna connector(s):
- J1 (1000 ohms +/- 100 ohms)
- J2 (8060 ohms +/- 800 ohms)
- J3 (4020 ohms +/- 400 ohms)
- J4 (2000 ohms +/- 200 ohms).

2 If the resistance value is (are) in the specified limits:

3 If the resistance value is (are) out of the specified limits:

[Rev.8 from Aug 2018] 2026.04.04 04:33:12 UTC