Electrical Bonding; Cabling And Wiring - Garmin GTS 8 Series Installation Manual

2.3

Electrical Bonding

Electrical equipment, supporting brackets, and racks should be electrically bonded to the aircraft's main
structure. Refer to SAE ARP 1870 section 5 when surface preparation is required to achieve electrical
bond. The electrical bond should achieve direct current (DC) resistance less than or equal to 2.5
milliohms to local structure to where the equipment is mounted. Compliance should be verified by
inspection using a calibrated milliohm meter. An equivalent OEM procedure may also be substituted.
There may be OEM-specific reasons for electrically isolating equipment or having a higher bond
resistance. These reasons should be rationalized upon installation approval. In general, Garmin
recommends that all GTS 8XX equipment be electrically bonded.
The antenna ground plane and doubler plate must be electrically bonded to the antenna baseplate. The
electrical bond must achieve direct current (DC) resistance less than or equal to 2.5 milliohms.
For composite aircraft, the antenna baseplate must be electrically bonded to the common ground of other
installed equipment for lightning purposes. This can be achieved through the antenna mounting screws.

2.4 Cabling and Wiring

Use #24 AWG or larger diameter wire for all connections unless otherwise specified. The minimum
diameter wire size for all GTS 8XX installation wiring is #24 AWG, except in the case of Aircraft Power
and Aircraft Ground and both shall be a minimum of #18 AWG. Refer to Table 2-1 for GPA 65 wiring
specifications.
A single circuit breaker shall be dedicated to the GTS 8XX unless specifically approved by the
manufacturer on a case by case basis, or allowed by the STC. Do not attempt to combine more than one
unit on the same circuit breaker unless it is specified on an aircraft manufacturer approved drawing, or
STC documentation, for the specific installation requiring a combined configuration.
The current rating for each standard density 37-pin D-sub connector pin is 5 Amps, and the current rating
for each high density 78-pin D-sub connector pin is 2 Amps. A 14 Vdc installation requires a minimum
of two Aircraft Power and two Aircraft Ground wires in the harness. A 28 Vdc installation requires a
minimum of one Aircraft Power and one Aircraft Ground wires in the harness.
It is the responsibility of the installing agency to take into account wire sizing based on the length and
number of wires, current draw of the unit, D-sub connector pin current rating, and the unit's internal
protection requirements.
NOTE
GTS 8XX/GPA 65 Installation Manual Page 2-5
190-00587-00 Revision 4TP