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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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04/26/21

Message Overview:

Message Name:

HEADING FLAG (Warning)

Identifier: 342OBS003
Effectivity: AIRCRAFT 20501 - 20999
System: Navigation
Associated CAS: None
System Description: 34-21-00
Schematic Diagram: None
Wiring Diagram: 34-21-09

Message Description:

The red 'HDG' warning flag indicates invalid heading source.

  • A loss of all heading data from the selected IRS, most likely caused by an IRS fault or failure.
  • Verification of system failure, or data bus loss can be checked on the MDC current fault page for further system details.

Possible Causes:

  • Flux Valve
  • Magnetic Field Disruption around the Flux Valve.
  • Inertial Reference System (IRS) Calibration
  • Input/Output Concentrator (IOC) (A4-IOC)
  • Inertial Reference Unit 1 (IRS 1) (A233)
  • Inertial Reference Unit 2 (IRS 2) (A232)
  • Data Bus Failure
  • Associated Wiring

Troubleshooting Tips:

Advisory Wire/Service Bulletin: None

Forum Articles/Infoservice/Newsletter: None

  • A loss of all heading data from the selected IRS, most likely caused by an IRS fault or failure.
  • Verification of system failure, or data bus loss can be checked on the MDC current fault page for further system details.

45_current_faults

Quick Links:

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
Operational Test of the Input/Output Concentrator Unit (IOC) AMM 31-45-05-710-801
Operational Test of the Inertial Reference System (IRS) AMM 34-45-00-710-801
Removal of the Inertial Reference Unit (IRU) AMM 34-45-01-000-801
Installation of the Inertial Reference Unit (IRU) AMM 34-45-01-400-801
Wiring - Maintenance Practices - ALL SPM 20-12-00-02
Wire Repair - Maintenance Practices - ALL SPM 20-12-10-02

Troubleshooting Recommendations:

  1. Access the MDC fault messages. Look for failures associated to the Inertial Reference System (IRS) or databus faults between the Input Output Concentrator (IOC) and the IRS.

    1. If related faults are displayed, troubleshoot them first.
    2. If no related faults are present, continue with next step.

  2. Swap the affected side IRU with the opposite side IRU. Is the fault still present?

    1. If YES, continue with next step.
    2. If NO, replace defective IRU and do close out.

  3. Perform a wiring check between the affected IRS and the IOC. Repair defective wiring if required.
  4. Do close out.

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