Antenna Grounding - Garmin GA 56W Installation Instructions Manual

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Table Of Contents

Table of Contents

1.2

Antenna Doubler/Backing Plate

The antenna installation must provide adequate support for the antenna considering a maximum drag load

of 5 lbs. (at subsonic speed). A doubler plate is required when the antenna is mounted on any

unsupported skin area. Never weaken the aircraft structure when choosing a mounting area. Refer to the

aircraft manufacturer's specifications and AC 43.13-2A Chapter 3 for appropriate guidance on antenna

installation. Make use of any available reinforcements where appropriate. Antenna performance is

improved by having an appropriate ground plane. When designing the doubler, the installer should

evaluate the ground plane requirements and make decisions to accomplish both functions with the

doubler.

Antenna installations on pressurized cabin aircraft require FAA approved installation

design and engineering substantiation data whenever such antenna installations

incorporate alteration (penetration) of the cabin pressure vessel by connector holes and/or

mounting arrangements. For needed engineering support pertaining to the design and

approval of such pressurized aircraft antenna installations, it is recommended that the

installer proceed according to any of the following listed alternatives:

1. Obtain approved antenna installation design data from the aircraft manufacturer.

2. Obtain an FAA approved STC pertaining to and valid for the antenna installation.

3. Contact the FAA Aircraft Certification Office in the appropriate Region and request identification

of FAA Designated Engineering Representatives (DERs) who are authorized to prepare and

approve the required antenna installation engineering data.

4. Obtain FAA Advisory Circular AC-183C and identify a DER from the roster of individuals in it.

5. Contact an aviation industry organization such as the Aircraft Electronics Association for

assistance.

1.3

Antenna Grounding Plane

The antenna should be attached to a metal ground plane (aircraft skin). The ground plane should be a

conductive surface as large as practical, with a minimum diameter of 8 inches. To use an antenna in

aircraft with fabric or composite skin, a ground plane is recommended. It is usually installed under the

skin of the aircraft, below the antenna, and is made either of aluminum sheet or of wire mesh.

1.4