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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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06/22/21

Message Overview:

Message Name:

HF SYSTEM FAULTS POSTED ON RMU

Message Code: 231OBS003
Effectivity: All
System: HF Communication System
System Description: 23-12-00
Schematic Diagram: 23-12-00 [ Global Express ]  [ G5000 ]  [ Global XRS ]
Wiring Diagram: 23-12-01 [ Global Express ]  [ G5000 ]  [ Global XRS ]

Message Description:

One or more High Frequency (HF) Systems are defective. HF transmission and/or reception are not serviceable. The procedures that follow contain instruction for one HF system. The instruction is also applicable to the other HF system. Differences are identified.

Possible Causes:

  • High Frequency (HF) Transceiver 1 (A49)
  • High Frequency (HF) Transceiver 2 (A50)
  • High Frequency (HF) Coupler 1 (CP4)
  • High Frequency (HF) Coupler 2 (CP5)
  • Radio Management Unit (RMU) 1 (A25)
  • Radio Management Unit (RMU) 2 (A26)
  • High Frequency (HF) Lead Feedline
  • High Frequency (HF) Antenna
  • High Frequency (HF) Coupler Mount
  • Fiber Optic
  • Associated Wiring

Troubleshooting Tips:

Advisory Wire/Service Bulletin: None

Forum Articles/Infoservice/Newsletter: None

NOTE: Replacement of the HF Antenna Coupler is never required if due to low pressure. Checking the HF Antenna Coupler pressure is not a troubleshooting step in service. Neither required is the recharging the coupler pressure per AMM TASK 23-12-05-780-802. The HF Antenna Coupler is considered 'on-condition' and only requires replacement if the troubleshooting clearly identifies the coupler has a fault.

Quick Links:

Operational Test of the HF Communication System AMM 23-12-00-710-801 [ Global Express ]  [ G5000 ]  [ Global XRS ]
Removal of the HF Transceiver AMM 23-12-01-000-801 [ Global Express ]  [ G5000 ]  [ Global XRS ]
Installation of the HF Transceiver AMM 23-12-01-400-801 [ Global Express ]  [ G5000 ]  [ Global XRS ]
Removal of the HF Antenna Couplers AMM 23-12-05-000-801 [ Global Express ]  [ G5000 ]  [ Global XRS ]
Installation of the HF Antenna Couplers AMM 23-12-05-400-801 [ Global Express ]  [ G5000 ]  [ Global XRS ]
Functional Test (Pressure) of the High Frequency (HF)
Communication Antenna Coupler		 AMM 23-12-05-780-802 [ Global Express ]  [ G5000 ]  [ Global XRS ]
Operational Test of the Radio Management Units (RMU) AMM 23-81-01-710-801 [ Global Express ]  [ G5000 ]  [ Global XRS ]
Wire Repair - Maintenance Practices - ALL SPM 20-12-10-02 [ Global Express ]  [ G5000 ]  [ Global XRS ]
Fiber Optics - Maintenance Practices - ALL SPM 20-51-00-02 [ Global Express ]  [ G5000 ]  [ Global XRS ]

Troubleshooting Recommendations:

WARNING: Make sure all personnel are clear of the HF Antenna, Antenna Feedline and Coupler when you do the HF System Test. The HF System can cause bad radio frequency burns when it transmits.

  1. Make sure the Aircraft is in the Weight-On-Wheels (WOW) condition to perform the RMU Power On Self Test (POST).
  2. Perform the operational test of the RMU (RMU 1 for HF 1 problems and RMU 2 for HF2).

    1. If the POST test results are not satisfactory, go to step 4.
    2. If the POST test results are satisfactory, continue with next step.

  3. Perform the operational test of the HF communication system.

    1. If the test results are satisfactory, do close out.
    2. If the test results are not satisfactory, continue with next step.

  4. On the RMU, access the HF MAINTENANCE LOG page and look at the faults for the last Power-On-Count (POC).
  5. Check if the fault message R/T FLT is present.

    1. If the fault message R/T FLT is present, go to step 29.
    2. If the fault message R/T FLT is not present, continue with next step.

  6. Check if the fault message PWR LOSS is present.

    1. If the fault message PWR LOSS is not present, go to step 8.
    2. If the fault message PWR LOSS is present, continue with next step.

  7. Check for 28 VDC power input at the R/T.

    1. If there is no 28 VDC, repair as required and do close out.
    2. If there is 28 VDC, continue with next step.

  8. Check if the fault message PA HOT is present.

    1. If the fault message PA HOT is present, go to step 29.
    2. If the fault message PA HOT is not present, continue with next step.

  9. Check if the fault message PA VOLT is present.

    1. If the fault message PA VOLT is present, go to step 29.
    2. If the fault message PA VOLT is not present, continue with next step.

  10. Check if the fault message FILT FLT is present.

    1. If the fault message FILT FLT is present, go to step 29.
    2. If the fault message FILT FLT is not present, continue with next step.

  11. Check if the fault message CPLR FLT is present.

    1. If the fault message CPLR FLT is present, go to step 30.
    2. If the fault message CPLR FLT is not present, continue with next step.

  12. Check if the fault message CPL VOLT is present.

    1. If the fault message CPL VOLT is present, go to step 30.
    2. If the fault message CPL VOLT is not present, continue with next step.

  13. Check if the fault message TUNE FLT is present.

    1. If the fault message TUNE FLT is present, troubleshoot it first and continue with next step.
    2. If the fault message TUNE FLT is not present, continue with next step.

  14. Perform a wiring check between RF cables at the coupler mount and coupler.

    1. If wiring checks are not good, repair defective wiring as required and do close out.
    2. If wiring checks are good, continue with next step.

  15. Check if the fault message CPL HOT is present.

    1. If the fault message CPL HOT is present, go to step 30.
    2. If the fault message CPL HOT is not present, continue with next step.

  16. Check if the fault message CPL VSWR is present.

    1. If the fault message CPL VSWR is present, troubleshoot it first and continue with next step.
    2. If the fault message CPL VSWR is not present, continue with next step.

  17. Perform a wiring check between RF cables at the coupler mount, coupler, and antenna.

    1. If wiring checks are not good, repair defective wiring as required and do close out.
    2. If wiring checks are good, go to step 30.

  18. Check if the fault message CNTL FLT is present.

    1. If the fault message CNTL FLT is present, troubleshoot it first and continue with next step.
    2. If the fault message CNTL FLT is not present, continue with next step.

  19. Perform a wiring check of the ARINC cables between the HF R/T and the RMU.

    1. If wiring checks are not good, repair defective wiring as required and do close out.
    2. If wiring checks are good, continue with next step.

  20. Check if the fault message FO FLT is present.

    1. If the fault message FO FLT is present, troubleshoot it first and continue with next step.
    2. If the fault message FO FLT is not present, continue with next step.

  21. Inspect Fiber Optic cables between HF R/T and coupler.

    1. If there is damage, repair as required and do close out.
    2. If there is no damage, continue with next step.

  22. Check if the fault message BUS A is present.

    1. If the fault message BUS A is present, troubleshoot it first and continue with next step.
    2. If the fault message BUS A is not present, continue with next step.

  23. Perform a wiring checks of the ARINC cables between the HF R/T and the RMU.

    1. If wiring checks are not good, repair defective wiring as required and do close out.
    2. If wiring checks are good, continue with next step.

  24. Check if the fault message BUS B is present.

    1. If the fault message BUS B is present, troubleshoot it first and continue with next step.
    2. If the fault message BUS B is not present, continue with next step.

  25. Perform a wiring checks of the ARINC cables between the HF R/T and coupler.

    1. If wiring checks are not good, repair defective wiring as required and do close out.
    2. If wiring checks are good, continue with next step.

  26. Check if the fault message BUS C is present.

    1. If the fault message BUS C is present, troubleshoot it first and continue with next step.
    2. If the fault message BUS C is not present, continue with next step.

  27. Perform a wiring checks of the ARINC cables between the HF R/T and coupler.

    1. If wiring checks are not good, repair defective wiring as required and do close out.
    2. If wiring checks are good, continue with next step.

  28. Perform the operational test of the HF COMM system.

    1. If system checks are good, do close out.
    2. If fault remains, continue with next step.

  29. Replace the HF Receiver/Transceiver (R/T).

    1. If system checks are good, do close out.
    2. If fault remains, continue with next step.

  30. Replace the HF Coupler.
  31. Do close out.

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