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(WARNING)
RED MESSAGE (CAUTION)
AMBER MESSAGE (ADVISORY)
CYAN MESSAGE (STATUS)
WHITE MESSAGE Require immediate crew attention. These messages are accompanied by flashing master warning, triple chime attenson with or without voice message or dedicated tone. Require immediate crew awareness and future crew action may be required in the form of alternate system selection or performance limitation. These message are accompanied by flashing master caution and a single chime. Indicate safe or normal system operation which require crew awareness, over and above the dark cockpit philosophy. Indicate minor failures or reduction in systems capability, which require no crew action.

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04/02/21

Message Overview:

Message Name:

NO TAWS-1 BUS OUTPUT

Message Code:

B3-642545

Associated CAS:

None

Reporting LRU: TAWS MARK V
System Description: 34-42-00
Schematic Diagram: 34-42-00
Wiring Diagram: 34-42-01

Message Description:

TAWS-1 bus data absent at L-IOC and R-IOC.

Possible Causes:

  • Terrain-Avoidance Warning System (TAWS) Computer (A34)
  • Junction Box (JB4)
  • Input/Output Concentrator Unit 1 (IOC) (A4-IOC1)
  • Input/Output Concentrator Unit 2 (IOC) (A4-IOC2)
  • Integrated-Avionics Processor System (IAPS) Card Cage (ICC) (A4)
  • Associated Wiring

Troubleshooting Tips:

Advisory Wire/Service Bulletin: None

Forum Articles/Infoservice/Newsletter: None

Quick Links:

Removal of the Junction Box JB4 AMM 24-63-13-000-802
Installation of the Junction Box JB4 AMM 24-63-13-400-802
Removal of the Integrated-Avionics Processor System (IAPS) Card Cage (ICC) AMM 31-45-01-000-801
Installation of the Integrated-Avionics Processor System (IAPS) Card Cage (ICC) AMM 31-45-01-400-801
Removal of the Input/Output Concentrator Unit (IOC) AMM 31-45-05-000-801
Installation of the Input/Output Concentrator Unit (IOC) AMM 31-45-05-400-801
Removal of the Terrain-Avoidance Warning System (TAWS) Computer AMM 34-42-01-000-801
Installation of the Terrain-Avoidance Warning System (TAWS) Computer AMM 34-42-01-400-801
Standard Practices - Replace Wiring SPM 20-12-00-02
Standard Practices - Repair Wiring SPM 20-12-10-02

Troubleshooting Recommendations:

  1. Reset TAWS (CB2-A6) circuit breaker or push in the TAWS TEST/RESET switch on the center pedestal.

    1. If system check passes, do close out.
    2. If fault remains, continue with next step.

  2. Do the wiring check of the ARINC 429 data bus TAWS-1 between TAWS computer connector A34BP1, through Junction Box 4, to the ICC connector A4P1 and A4P101. Repair/replace as required.

    1. If system check passes, do close out.
    2. If fault remains, continue with next step.
      NOTE: An internal short of any LRUs connected to this data bus might cause this failure.

  3. Replace TAWS computer.

    1. If system check passes, do close out.
    2. If fault remains, continue with next step.

  4. Replace Left IOC.

    1. If system check passes, do close out.
    2. If fault remains, continue with next step.

  5. Replace Right IOC.

    1. If system check passes, do close out.
    2. If fault remains, continue with next step.

  6. Replace the ICC.
  7. Do close out.

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