Electrical Bonding Test; Gps 175/Gnx 375/Gnc 355 Bonding Check (Metallic Or Tube-And-Fabric Aircraft); Gps 175/Gnx 375/Gnc 355 Bonding Check (Composite Aircraft) - Garmin GPS 175 Maintenance Manual

4.5 Electrical Bonding Test

4.5.1

GPS 175/GNX 375/GNC 355 Bonding Check (Metallic or Tube-and-Fabric Aircraft)

NOTE
A bonding test failure may occur if a fastener is not torqued to the specified torque value.
For installations that use screws in lieu of rivets to secure the rack to surrounding
structure, verify that the screws are torqued to the appropriate value before proceeding to
remove the rack. Refer to Section 4.4 for torque values.
Perform an electrical bonding check as follows:
1. Remove the GPS 175/GNX 375/GNC 355 from the mounting rack.
2. Remove the backplate assembly from the rack.
3. Measure the resistance between the mounting rack and nearby exposed portion of aircraft metallic
structure and verify it is less than or equal to 5 mΩ.
In the event of bonding test failure, remove the GPS 175/GNX 375/GNC 355 rack, clean the attachment
points with a bonding brush at both the rack and the aircraft, and re-attach the rack to the rails in the panel.
Measure 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 mΩ.
4. Re-install the backplate assembly and re-install the GPS 175/GNX 375/GNC 355 in the mounting
rack.
4.5.2

GPS 175/GNX 375/GNC 355 Bonding Check (Composite Aircraft)

NOTE
A bonding test failure may occur if a fastener is not torqued to the specified torque value.
For installations that use screws in lieu of rivets to secure the rack to surrounding
structure, verify that the screws are torqued to the appropriate value before proceeding to
remove the rack. Refer to Section 4.4 for torque values.
Perform an electrical bonding check as follows:
1. Remove the GPS 175/GNX 375/GNC 355 from the mounting rack.
2. Remove the backplate assembly from the rack.
3. Measure the resistance between the mounting rack and the instrument panel and verify it is less
than or equal to 10 mΩ.
In the event of bonding test failure, remove the GPS 175/GNX 375/GNC 355 rack, clean the attachment
points with a bonding brush at both the rack and the aircraft, and re-attach the rack to the rails in the panel.
Measure the resistance between the mounting rack and the instrument panel and ensure that the resistance
is less than or equal to 5 mΩ.
4. Re-install the backplate assembly and re-install the GPS 175/GNX 375/GNC 355 in the mounting
rack.
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GPS 175/GNX 375/GNC 355 Part 23 AML STC Maintenance Manual
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