General Requirements For Installation In Composite Aircraft - Garmin GTX 335 w GPS Installation Guidance

4.1.3

General Requirements for Installation in Composite Aircraft

Follow general installation guidance provided in section 4.1.2. Installations of fabricated brackets or
shelves in composite aircraft must be completed in accordance with guidance provided by the aircraft
manufacturer, such as the aircraft's maintenance manual (MM) and/or structural repair manual (SRM).
Repair procedures contained in the MM or SRM can be used to support the installation of new brackets or
shelves fabricated for installation of the GTX 335. The MM or SRM provides the following information:
Materials generally used for structural repair, including but not limited to adhesives, resins, pre-
preg tape and broad goods, core material, etc.
Fabrication and processing procedures for structural repair
Number of plies and stacking orientation/sequence
Shape of repair
Applicable dimensions and tolerances
Protective coatings and sealants needed for the repair
Fabricated brackets or shelves can be metallic or composite structure as recommended in the MM or SRM.
Use guidance from the aircraft's MM or SRM to do this procedure:
1. Pre-fit fabricated part(s) to make sure the installation location is correct.
2. Clean and dry the fabricated part(s) and the aircraft structure the part(s) will be attached to.
3. Prepare attachment surfaces on the fabricated part and the aircraft's installation location for
application of adhesive.
4. Prepare composite plies considering orientation, stacking sequence, and size.
5. Reference the method of layup defined in the document.
6. Inspect the installed parts for flaws.
7. Make sure parts and joints have fully cured before installation of equipment.
Aircraft constructed out of non-metallic materials such as fiberglass, carbon composite material, or fabric
must take special precautions to protect the GTX 335 equipment from HIRF and indirect effects of lightning
(IEL).
If applicable bonding structure is not immediately accessible, bonding can be achieved using aluminum
tape (3M P/N 436, 438 or other adhesive-backed dead soft aluminum foil with minimum 7.2 mils metal
thickness). A tape maximum length-to-width ratio of 7:1 must be maintained (i.e., up to seven inches in
length for every one inch in width). Additional guidance can be found in AC43.13-1B and SAE ARP1870,
Sections 5.1 and 5.5.
The following procedure is recommended for implementation of the guidance above.
1. If the aluminum tape must be isolated from carbon composite material, secure a thin layer of
fiberglass cloth to the carbon fiber with fiberglass resin as shown in figure 4-4.
2. Prepare the aluminum surface at the ground location per figure 3.15.1.
OR
Identify or install a ground stud to which the bonding strap can be attached. Any new or existing
ground stud shall be prepared for electrical bonding in accordance with section 3.15.
3. Route the aluminum tape between the transponder mounting rack and the grounding location. If
needed to maintain the length-to-width ratio, the tape width can be overlapped in more than one
strip. If two or more pieces of tape must be joined end-to-end, they can be joined as illustrated in
figure 4-5.
190-00734-17
Rev. 1
GTX 335 w/GPS Installation Guidance
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