components thoroughly to a smooth
is to be applied between the contact surfaces of
the patch and parent skin (fay surface sealing) so
that squeeze-out can be used to form a illet. In
addition, permanent fasteners should be installed wet
(3) Application of a Sealing Repair. All bolted
repair patches shall be installed with sealant. Sealant
(a) Fay Surface Sealing. For this type of
Solvent clean dimples, counter-
sealing, sealant is applied between the
sinks and surrounding area.
contact surfaces of the patch and the
Apply small bead or layer of sealant
around fastener shank, counter-
sink, dimple or conical area of
Solvent clean patch and parent
fastener head with brush.
Install Fastener. Remove sealant
If required, cut pieces of scrim cloth
which extrudes out around fastener
to it patch(es). Cut holes in scrim
immediately with solvent moist-
at each fastener hole with a knife.
ened wiping cloth.
Apply sealant to one mating sur-
(c) Fillet Seal. Once the repair patch has
face using pneumatic sealant gun
been installed, a inal seal around the
equipped with sealant gun noz-
patch may be required. If the repair is a
zle. Apply two continuous beads of
lap repair installed on the outer moldline
sealant centered between fastener
of the aircraft, the periphery of the patch
hole pattern and each edge of part.
should be faired in with the surrounding
Place parts in assembly position
immediately after sealant applica-
Clean the parent skin around the
tion. Install enough temporary fas-
patch periphery with solvent.
teners to pull faying surfaces into
contact and squeeze out excess
After the solvent wiped surface is
sealant before installing permanent
dry, apply masking tape around the
fasteners. Install permanent fas-
patch. The tape should be parallel
teners with wet sealant.
with the patch edges and allow a
gap of approximately 0.25 inches.
Fair sealant squeeze-out into illet
around patch periphery.
Apply sealing compound over the
skin adjacent to the patch. Using a
Remove any sealant which
squeegee, fair the sealant between
extrudes through fastener holes,
the patch and the edge of the tape.
fraying surfaces and/or butt joints
onto exterior with a solvent moist-
Remove tape from skin.
ened wiping cloth immediately after
installation of patch.
h. Partial Thickness Damage Bolted Repair. This
repair is applicable to surface damage in composite
(b) Fastener Sealing.
skins without penetrating the composite skin. It is
fasteners used for bolted repair
also applicable to the repair of unsuccessful adhesive
patches shall be installed wet with
injection delamination repairs. Typical repairs are