190-01007-A1
System Maintenance Manual GTN 6XX/7XX Part 23 AML STC
Rev. 5
Page 4-5
4.5.3 GMA 35 (Metallic or Tube/Fabric Aircraft)
A bonding check is required for the GMA 35. Perform an electrical bonding check as follows:
1. Gain access to the GMA 35 by removing the GTN 7XX.
2. Remove the GMA unit from the mounting rack.
3. Remove backplate assembly from the rack.
NOTE
The GTN 7XX backplate assembly must be removed from the GTN rack prior to
performing Step 4.
4. Measure the resistance between the mounting rack and nearby exposed portion of aircraft metallic
structure and verify it is less than or equal to 10 milliohms.
In the event of bonding test failure, remove the GMA 35 rack and clean the attachment points with a
bonding brush at both the GMA rack and the aircraft attachment points. Re-verify the resistance between
the mounting rack and nearby exposed portion of aircraft metallic structure and ensure that the resistance is
less than or equal to 2.5 milliohms.
5. Reinstall the backplate assembly and reinstall the GMA unit in the mounting rack.
4.5.4 GMA 35 (Composite Aircraft)
1. Gain access to the GMA 35 by removing the GTN 7XX.
2. Remove the GMA unit from the mounting rack.
3. Remove the backplate assembly from the rack.
NOTE
The GTN 7XX backplate assembly must be removed from the GTN rack prior to
performing Step 4.
4. Measure the resistance between the mounting rack and the instrument panel, and verify it is less
than or equal to 10 milliohms.
In the event of bonding test failure, remove the GMA 35 rack and clean the attachment points with a
bonding brush at both the GMA rack and the aircraft attachment points. Re-verify the resistance between
the mounting rack and the instrument panel and ensure that the resistance is less than or equal to 5
milliohms.
5. Reinstall the backplate assembly and reinstall the GMA unit in the mounting rack.
