Installation Instructions

190-01007-A3 GTN 6XX/7XX AML STC Installation Manual
Rev. 4 Page B-5
B.3 Avionics Stack Cutout
Some instrument panels may require minor modification to increase width or height of the avionics stack
cutout to accommodate installation of the GTN 6XX, GTN 7XX, or both.
In order to satisfy the structural requirements for the installation of the GTN 6XX/7XX the following
conditions must be met:
1. A cutout cannot be made into aircraft primary structure.
2. Cutout area must not affect any subpanel structure.
3. Some stationary instrument panels are considered primary structure. Modification of such panels
is not covered by this STC and requires additional approval.
4. Refer to Figure A-9 for dimensions of GTN 6XX/7XX cutouts.
5. Radius corners and remove burrs from cut edges. Finish paint the cut edge or apply corrosion
protection as specified in Section B.2.
B.4 Modification of Avionics Stack Mounting Rails
Existing mounting rails may contain holes from previously installed equipment. If existing rail holes do
not match holes in GTN 6XX/7XX mounting racks, it may be acceptable to modify the rails by adding
fastener holes to accept installation of GTN 6XX/7XX mounting racks.
In order to satisfy the structural requirements for the installation of the GTN 6XX/7XX the following
conditions must be met:
1. Additional fastener holes shall maintain an edge distance at least 2*D.
2. Added and existing holes in the mounting rail shall maintain at least 3*D distance between hole
centers.
3. If existing brackets or mounting rails are determined to be unsuitable for installation of the
GTN 6XX/7XX, new parts need to be fabricated. In some cases, there may be too many holes
from previous avionics mounting tray installations.
In order to satisfy the structural requirements for the installation of the GTN 6XX/7XX the following
conditions must be met:
1. Carefully remove existing mounting rails from instrument panel. Avoid enlarging existing rivet
holes.
2. Fabricate new parts as close to the original design as possible (e.g. “rails” that have had too many
holes drilled to be functional for another installation should be replaced with new “rails” of the
same material thickness and type with only the holes necessary for the planned avionics stack).
3. If material type of the original rails or brackets is unknown, replace with 2024-T3 (bare or Clad)
of the same thickness as the original part. Use sheet metal techniques (bend radius, fillets, etc.)
appropriate to material type and thickness.
4. Fabricated parts shall be corrosion protected. Apply zinc chromate primer that meets FED STD
TT-P-1757, or epoxy primer that meets MIL-P-23377, or other corrosion protection methods
listed in the aircraft’s maintenance manual. Area around the fastener holes on the side of the
fabricated rail that attaches to the GTN mounting rack must be cleaned and prepared for electrical
bond per Section 2.4.5 of this manual.
5. Install fabricated mounting rails to instrument panel. Use number and size of rivets appropriate to
original rivets removed.