Electrical Bonding; Figure 4-56 - Nut And Washer Electrical Bonding; Figure 4-57 - Nut Plate Electrical Bonding - Garmin G5 Installation Manual

4.5 Electrical Bonding

The GAD 29/29B and GAD 13 are the LRUs installed by this STC that require chassis bonding.
Sections 4.5, 4.5.1, 4.5.2, 4.5.3 present data on acceptable methods of electrical bonding for the GAD
29/29B and GAD 13. For G5 and GMU 11 bonding strap requirements and associated installations, refer
to section 4.5.4 and 4.5.5.
GAD 29/29B and GAD 13 electrical bonding can be achieved with mounting hardware (rivets, bolts,
nuts, washers, etc.). A reliable electrical bond relies on mated surfaces to be clean of any
primer/grease/dirt. When bolts are used to secure racks/brackets/etc. and are relied upon for electrical
bond, in lieu of the mating surfaces of the racks/brackets/etc. then the area under the head of the
bolt/screw or washer must be free of primer and a burnished area should be prepared that is at least
0.125 inch wider than the head of the bolt or the washer (if used) under the head. If primer or film was
removed to achieve this then any exposed area still visible after the bond is completed must be
refinished with the original finish or other suitable film (e.g. primer) or coating, ref ARP1870. If the bolt
is secured with washer and nut then a similar burnish area as described above shall occur between the
washer and the mounting structure, see Figure 4-56. Rivets used to mechanically attach
brackets/shelves/etc. provide an inherent electrical bond through the rivets and require no additional
bond preparation. Similarly riveted nut plates do not need any special bonding preparation and can be
relied upon to provide electrical bond between the fastener and the nut plate. The top or bottom side of
the Garmin racks or equipment flanges do not need any special bond preparations, see Figure 4-57.
Additional details on how to accomplish electrical bonding can also be found in SAE ARP1870 section
5.
When equipment is mounted to honeycomb shelves, the face sheets must be metal. The honeycomb
Garmin G5 Electronic Flight Instrument Part 23 AML STC Installation Manual
Figure 4-56 – Nut and Washer Electrical Bonding
Figure 4-57 – Nut Plate Electrical Bonding
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