20-4 STRUCTURAL REPAIR / GENERAL BONDED FASTENER REPLACEMENT
ICON A5 / MAINTENANCE MANUAL CHANGE C0
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Read these repair instructions in their entirety before starting. Any questions or uncertainties regarding
interpretation of these instructions shall be forwarded to ICON Owner Support before any work is
done.
All substrate materials must be protected from temperatures exceeding 200°F during the application
of heat to soften the adhesive material attaching the fastener. Excessive temperatures can cause
disbond, delamination, and blistering of composite substrates, resulting in a loss of strength and reli-
ability.
CAUTION: Temperature more than 200°F (93°C) can permanently damage
the composite aircraft structure. Use extreme caution whenever
using applied heat.
Use the following methods to prevent temperature damage
• Keep the maximum output air temperature of the heat gun below the threshold of damage of
the substrate and any surrounding components (200°F).
• Use any available technologies (e.g. infrared thermometer, thermocouple, etc.) to monitor the
temperature of the nearby substrate during the operation. It should always below the threshold
temperature of 200°F (93°C).
• Mask adjacent components and substrates with thermal barrier (e.g. silicone sheet) to mini-
mize heat transfer to unintended areas.
1. Cut a conformal mask from silicone rubber sheet (0.25-inch thick). The mask should extend a
minimum of 3-inches beyond the fastener in all directions. In the middle of the mask, cut a mini-
mally sized hole to permit access to the fastener intended to be heated and removed. Drape the
mask over the fastener and secure with aluminum foil tape (3M 425).
2. Use a heat gun to heat the fastener for removal. Hold the heat gun at a 90° inclination to the
fastener (perpendicular to the adhesion surface), and position it approximately one inch from the
baseplate of the fastener. Center the airstream on the fastener base plate to soften the under-
lying adhesive.
3. Allow the heat gun to dwell above the fastener until the underlying adhesive softens (about 30 to
45 seconds). It may help to grip the fastener with pliers and apply a twisting load (twisting about
an axis perpendicular to substrate surface) while the heat is applied.
4. Once the adhesive is soft, and before any cooling occurs, use pliers to grip and twist the fastener
from the substrate. The twisting motion is important as it allows the initial bond to be broken with
an in-plane load. An out-of-plane load, such as that generated by pulling or prying, is more likely
to result in delamination damage.
5. If any adhesive remains on the substrate after fastener removal, use the same method to heat
the remaining adhesive and use a hard plastic chisel or similar tool to wedge the adhesive and
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