FAA Advisory Circular 43.13-1B
Acceptable Methods, Techniques, and Practices
Aircraft Inspection and Repair
AC 43.13-1B | 3. Fiberglass and Plastics | 1. Repair of Light Load Laminate Structures | 3-2. Fiberglass Laminate Repairs
AC 43.13-1B
9/8/98
essential, as any moisture remaining on the
surface will inhibit the cure of the resin. Dry
the fiberglass laminate thoroughly prior to
bonding repair. Mix enough resin, using the
manufacturer’s instructions, to completely
cover the damaged area, and apply one or two
coats. Cover the resin with a peel ply to ex
clude all air from the resin while it is curing.
After the resin has cured, remove the film and
file or sand the surface to conform to the origi
nal shape of the part. Ensure that all edges of
the laminate part are sealed to prevent water
absorption. Then refinish it to match the rest
of the structure.
b. Superficial scars, scratches, surface
abrasion, or rain erosion can generally be re
paired by applying one or more coats of a suit
able low temperature resin, catalyzed to cure at
room temperature, to the abraded surface. The
number of coats required will depend upon the
type of resin and the severity of the damage.
(1) Damage not exceeding the first layer
or ply of fiberglass laminate can be repaired by
filling with a putty consisting of a compatible
room-temperature-setting resin and clean short
glass fibers. Before the resin sets, apply a
sheet of peel ply over the repair area and work
out any bubbles and excess resin. After the
resin has cured, sand off any excess and pre
pare the area for refinishing.
FIGURE 3-1. Typical laminate (facing) repair.
(3) Damage that extends completely
through one facing and into the core requires
the replacement of the damaged core and fac
ing. A method for accomplishing this type of
repair is shown in figure 3-2. An alternate
method for repairing the facing is shown in
figure 3-3. The damaged portion is carefully
trimmed out to a circular or oval shape and the
core material is removed completely to the op
posite facing. Exercise caution so as not to
damage the opposite facing or to start delami
nation between the facings and the core around
the damage.
(2) Damage deep enough to seriously
affect the strength of the laminate (usually
more than the first ply or layer of fabric) may
be repaired as illustrated in figure 3-1. Coat
the sanded area with room-temperature-setting
resin and apply contoured pieces of glass fab
ric soaked in resin. Apply a peel ply sheet
over the repair and work out any bubbles and
excess resin. After the resin has cured, scrape
off the excess resin and sand the surface of the
repair to the original contour.
FIGURE 3-2. Typical core and facing repair.
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