FAA Advisory Circular 43.13-1B
Acceptable Methods, Techniques, and Practices
Aircraft Inspection and Repair
AC 43.13-1B | 1. Wood Structure | 4. Repairs | 1-52. Fabric Patch
9/8/98
AC 43.13-1B
doubler from a rib or a spar. Refer to fig-
ure 1-17 for repair details.
(b) Prepare a patch and a doubler of
the same species plywood as the surrounding
skin using the dimensions shown in fig-
ure 1-17.
(c) Lay the oval plug patch over the
damage and trace the patch onto the skin. Saw
to the line, and trim the hole edges with a knife
and sandpaper.
(d) Mark the exact size of the patch
on one surface of the oval doubler and apply
adhesive to the area outside the line. Insert
doubler through the hole and bring it, adhesive
side up, to the underside of the skin with the
pencil outline of the patch matching the edges
of the hole. If the curvature of the surface to
be repaired is greater than a rise of 1/8 inch in
6 inches, the doubler should be preformed by
hot water or steam bending to the approximate
curvature. As an alternative to preforming of
the 1/4 inch stock, the doubler may be lami-
nated from two thicknesses of 1/8 inch ply.
(e) Apply nailing strips outlining the
hole to apply bonding pressure between dou-
bler and skin. Use a bucking bar to provide
support for nailing. When two rows of nails
are used, stagger nail spacing. Allow adhesive
to cure.
(f) Apply adhesive to remaining sur-
face of the doubler and to the mating surface
on the patch. Lay the patch in position over
the doubler, and screw the pressure plate to the
patch assembly using a small nail to line up the
holes that have been previously made with
patch and plate matching. No. 4 round head
screws are used. Lead holes in the plywood
doubler are not necessary. Waxed paper or
plastic wrap between the plate and patch pre-
vents adhesive from bonding the plate to the
patch. No clamps or further pressure need be
applied, as the nailing strips and screws exert
ample pressure.
(2) Round plug patches may be made
by following the steps in figure 1-18. The
steps are identical to those for making the oval
patch except for the insertion of the doubler.
In using the round patch, where access is from
only one side, the round doubler cannot be in-
serted unless it has been split.
1-52. FABRIC PATCH. Small holes not
exceeding 1 inch in diameter, after being
trimmed to a smooth outline, may be repaired
by doping a fabric patch on the outside of the
plywood skin. The edges of the trimmed hole
should first be sealed, and the fabric patch
should overlap the plywood skin by at least
1 inch. Holes nearer than 1 inch to any frame
member, or in the leading edge or frontal area
of the fuselage, should not be repaired with
fabric patches.
Par 1-51
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