Preparation Of Doubler; Antenna Installation Instructions - Garmin GDU 37X Installation Manual

3.5.1 Preparation of Doubler

1. Use Garmin P/N: 115-00846-00, or refer to Table 3-6 for guidance on selecting the appropriate doubler
drawing based on the thickness of skin at the antenna location. Make the doubler from 2024-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 the doubler
for use with flush head rivets (MS20426AD4-x).
3. When using Garmin P/N: 115-00846-00 doubler, sixteen rivet holes exist in the part. For installation
of Garmin P/N: 115-00846-00 in skins of thickness between 0.032" and 0.049", only the rivets
identified for use through the skin cutout detail (Figure 3-18) and doubler installation (Figure 3-21) are
required.

3.5.2 Antenna Installation Instructions

1. Refer to Table 3-6 (and to Figures C-2.X) for guidance on selecting the appropriate mounting cutout.
Drill or punch the holes to match the mating part (doubler).
2. Install a doubler plate to reinforce the aircraft skin, as required. Refer to Section 3.5.1 for doubler
preparation and Table 3-6 for additional guidance on the doubler installation. Dimple aircraft skin
when the skin thickness is less than 0.051" for installation of flush head rivets. Countersink aircraft
skin when the skin thickness is between 0.051" and 0.063" for installation of flush head rivets.
3. Place the install gasket on top of aircraft skin using the four screw holes to align the gasket.
4. Locking nuts are required to secure the antenna (locking nuts installed on doubler). Torque the four
supplied #10-32 stainless steel screws (Garmin P/N: 211-60212-20, MS51958-67, or equivalent) 20-25
in-lbs. Torque should be applied evenly across all mounting studs to avoid deformation of the
mounting area.
5. Ensure that the antenna base and aircraft skin are in continuous contact with the gasket.
6. Seal the antenna and gasket to the fuselage using Dow Corning 738 Electrical Sealant or equivalent.
Run a bead of the sealant along the edge of the antenna where it meets the exterior aircraft skin. Use
caution to ensure that the antenna connectors are not contaminated with sealant.
Do not use construction grade RTV sealant or sealants containing acetic acid.
These sealants may damage the electrical connections to the antenna. Use of
these type sealants may void the antenna warranty.
Page 3-14
Revision C
CAUTION
GDU 37X Installation Manual
190-01054-01