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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 TUNING AND POOR RECEPTION

Message Code: 231OBS004
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:

High Frequency (HF) 1 or 2 will not tune to a specific frequency or range of frequencies. No HF 1 or 2 internal or antenna faults reported by CAIMS.

Possible Causes:

None

Troubleshooting Tips:

Advisory Wire/Service Bulletin:

  • Rockwell Collins SB MT-9042A-23-1 - COMMUNICATIONS - MT-9042A - TUNE FAULT MITIGATION REGARDING HIGH ANTENNA LOOP RESISTANCE

Forum Articles/Infoservice/Newsletter: None

NOTE 1: Make sure to carry out the resistance check as instructed in the 'Pretest' section 3.A.(1) (a) & (b) of SB MT-9042A-23-1 prior to performing the SB.

NOTE 2: 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:

Removal of the HF Transceiver Mounting Tray AMM 23-12-03-000-801 [ Global Express ]  [ G5000 ]  [ Global XRS ]
Installation of the HF Transceiver Mounting Tray AMM 23-12-03-400-801 [ 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 ]
Removal of the HF Antenna Coupler Mounting Tray AMM 23-12-07-000-802 [ Global Express ]  [ G5000 ]  [ Global XRS ]
Installation of the HF Antenna Coupler Mounting Tray AMM 23-12-07-400-802 [ Global Express ]  [ G5000 ]  [ Global XRS ]

Troubleshooting Recommendations:

  1. Check bonding of coupler trays. Remove couplers from trays. Measure bonding from coupler center conductor to outer ring <20 mΩ as per Fig 1.

    1. If <20 mΩ, go to step 3.
    2. If >20 mΩ, continue with next step.

  2. Remove metallic strip linking coupler trays to antenna feed line as per Fig 2. Scrape off paint between screws anchor point as per Fig 3. Re-install metallic strip and apply humiseal over screws.
  3. Measure bonding from coupler trays to airframe <2.5 mΩ.

    1. If <2.5 mΩ, go to step 5.
    2. If >2.5 mΩ, continue with next step.

  4. Scrape off any paint to airframe at tray anchor points (x4). Verify coupler trays proper installation of ground straps (x4).
  5. Test HF as per maintenance manual.
  6. Do close out.

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