G3X Installation Manual – Antennas Page 6-7190-01115-01 Revision A6.4 Teardrop Footprint Antenna Installation (GA 55 and GA 56)This section describes the structural mounting of the teardrop footprint antenna installation.An acceptable installation method is to use Garmin P/N: 115-00846-10 doubler plate with the GA 55 orGA 56 stud mount antennas. Another acceptable method is to fabricate and install one of three doublers(Figure 6-4, Figure 6-5, and Figure 6-6), depending on the thickness of the skin. The three doublerdesigns vary only by number of rivets and hole preparation for installation with flush rivets. Table 6-5provides a summary of design and installation details for selecting the appropriate antennadoubler/backplate.Figure 6-7 shows an example of the doubler installed between stringers on the top fuselage skin, just offcenterline. The location should be flat, with no gaps between the skin and doubler, to keep fromdeforming the skin during installation.Table 6-5. Teardrop Footprint Antenna Doubler Design and InstallationAircraft Skin Thickness 0.032” to 0.049” 0.049” to 0.051” 0.051” to 0.063”Doubler Design (Figure) Figure 6-4 Figure 6-5 Figure 6-6Number of Rivets Required 12 16 16Type of Rivets Required 1 MS20426AD4-x MS20426AD4-x MS20426AD4-xSkin Preparation for Rivets Dimple Dimple CountersinkDoubler Preparation for Rivets Countersink Countersink NoneSkin Cutout Detail (Figure) Figure 6-8 Figure 6-9 Figure 6-10Doubler Installation (Figure) Figure 6-11 Figure 6-12 Figure 6-13Notes:1. Rivet length determined at installation, dependent on thickness of material (rivet length = grip length +1.5*rivet diameter)Refer to Figure B-2.X for Garmin Antenna installation drawings.6.4.1 Preparation of Doubler1. Use Garmin P/N: 115-00846-10, or refer to Table 6-5 for guidance on selecting the appropriatedoubler drawing based on the thickness of skin at the antenna location. Make the doubler from2024-T3 Aluminum (AMS-QQ-A-250/5), 0.063” sheet thickness.2. For installation in aircraft skins of thickness less than 0.051”, countersink the rivet holes in thedoubler for use with flush head rivets (MS20426AD4-x).3. When using Garmin P/N: 115-00846-10 doubler, sixteen rivet holes exist in the part. Forinstallation of Garmin P/N: 115-00846-10 in skins of thickness between 0.032” and 0.049”, onlythe rivets identified for use through the skin cutout detail (Figure 6-8) and doubler installation(Figure 6-11) are required.
