System Maintenance Manual GTN 6XX/7XX Part 23 AML STC 190-01007-A1Page 4-4 Rev. 54.5 Electrical Bonding Test4.5.1 GTN Bonding Check (Metallic or Tube/Fabric Aircraft)Perform an electrical bonding check as follows:1. Remove the GTN 6XX or GTN 7XX from the mounting rack.2. Remove the backplate assembly from the rack.NOTEFor GTN 7XX only, if the GMA 35 is installed, it must be removed from its rack and theGMA 35 backplate assembly must be removed prior to performing Step 3. When aGMA 35 bonding check is planned, perform the GMA 35 bonding check prior toreinstalling the GTN backplate assembly to the rack.3. Measure the resistance between the mounting rack and nearby exposed portion of aircraft metallicstructure and verify it is less than or equal to 10 milliohms.In the event of bonding test failure, remove the GTN rack and clean the attachment points with a bondingbrush at both the GTN rack and the aircraft and reattach the rack to the rails in the panel. Re-verify theresistance between the mounting rack and nearby exposed portion of aircraft metallic structure and ensurethat the resistance is less than or equal to 2.5 milliohms.4. Reinstall the backplate assembly and reinstall the GTN in the mounting rack.4.5.2 GTN (Composite Aircraft)Perform an electrical bonding check as follows:1. Remove the GTN 6XX or GTN 7XX from the mounting rack.2. Remove the backplate assembly from the rack.NOTEFor GTN 7XX only, if the GMA 35 is installed, it must be removed from its rack and theGMA 35 backplate assembly must be removed prior to performing Step 3.3. Measure the resistance between the mounting rack and the instrument panel, verify it is less thanor equal to 10 milliohms.In the event of bonding test failure, remove the GTN rack and clean the attachment points with a bondingbrush at both the GTN rack and the aircraft and reattach the rack to the rails in the panel. Re-verify theresistance between the mounting rack and the instrument panel and ensure that the resistance is less than orequal to 5 milliohms.4. Reinstall the backplate assembly and reinstall the GTN in the mounting rack.
