190-01279-01
GTS 8XX Part 23 AML STC Maintenance Manual
Rev. 2
Page B-4
B.3 Composite Aircraft
Use the following guidance when repairing or replacing electrical bonding components. Use aluminum
tape (3M P/N 438 or other adhesive-backed dead soft aluminum foil with minimum metal thickness of
7.2 mils) when replacing existing aluminum foil that has been damaged. If using a bonding tape, a
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). A minimum tape width of six inches is required for bonding strips. If a bonding strap is
used in conjunction with a bond tape, the bond tape maximum length-to-width ratio of 5:1 must be
maintained (i.e., up to five inches in length for every one inch in width). Maintain the existing aluminum
tape routing. Additional guidance can be found in AC 43.13-1B and SAE ARP1870, Sections 5.1 and 5.5.
Additional considerations:
•
Ensure isolation from the carbon composite material is maintained to prevent corrosion due to
dissimilar materials
•
The GTS ground must be routed to the aircraft ground reference specified in Table 2-2
•
The aluminum tape must not have any tears in the joint or along the length of the tape, as tears
will degrade the bonding performance
•
Where the tape is bonded with any mating metal part:
◦
The tape must be folded over twice onto itself
◦
The folded area must be covered with a thin aluminum plate to avoid damage from
fasteners and to provide good contact with all tape strips
◦
Mating metal-to-metal contact surfaces must be carefully cleaned to ensure good contact
◦
The plate and tape must be secured to the mating metal part with multiple fasteners
When replacing damaged aluminum foil, the following procedure is recommended for bonding on
composite structures:
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 B-4.
Figure B-4 Fiberglass Insulation for Carbon Material
ALUMINUM TAPE
CARBON
FIBER
STRIP OF LIGHT FIBERGLASS CLOTH
SUCH AS 1080-50 (1.45 OZ/SQ. YARD)
ATTACHED WITH FIBERGLASS RESIN.
¼” MINIMUM DISTANCE
EACH SIDE.
6” MINIMUM
