FAA Advisory Circular 43.13-1B
Acceptable Methods, Techniques, and Practices
Aircraft Inspection and Repair
AC 43.13-1B | 2. Fabric Covering | 3. Inspection and Testing | 2-32. Coating Identification
AC 43.13-1B
9/8/98
(1) Glass fabric will not deteriorate
from UV exposure, but will be deteriorated by
acid rain, dew fallout, and chaffing if loose in
the prop blast area.
(2) Cotton, linen, and glass fabric cov-
erings are dependent solely on the strength and
tautening characteristics of the dope film to
carry the airloads. Dope coatings on heat-
tautened polyester fabric will also absorb all
the airloads because the elongation of polyes-
ter filaments are considerably higher than the
dope film. Polyester fabric that is coated with
materials other than dope, is dependent solely
on the heat tautening and low-elongation char-
acteristics of the polyester filaments to develop
tension and transmit the airloads to the air-
frame without excess distortion from a static
position.
(3) Cracks in coatings will allow any
type of exposed fabric to deteriorate. Cracks
should be closed by sealing or removing the
coatings in the immediate area and replace
with new coatings, or recover the component.
2-31. FABRIC IDENTIFICATION.
Cotton Fabric meeting TSO-C15 or TSO-C14
can be identified by an off-white color and
thread count of 80 to 94 for TSO-C14b and
80 to 84 for TSO-C15d in both directions.
a. Aircraft linen conforming to British
specification 7F1 may be identified by a
slightly darker shade than cotton fabric and ir-
regular thread spacing. The average thread
count will be about the same as Grade A fabric
(TSO-C15d). The non-uniformity of the linen
thread size is also noticeable, with one thread
half the size of the adjacent thread. When
viewed under a magnifying glass, the ends of
the cotton and linen fiber nap may be seen on
the backside. The nap is also seen when the
coating is removed from the front or outside
surface. A light-purple color showing on the
back side of cotton or linen fabric indicates a
fungicide was present in the dope to resist de-
terioration by fungus and mildew.
b. Polyester fabric conforming to
TSO-C14b or TSO-C15d is whiter in color
than cotton or linen. The fabric styles adapted
for use as aircraft covering have a variety of
thread counts, up to ninety-four (94), depend-
ing on the manufacturing source, weight, and
breaking strength. Polyester is a monofilament
and will not have any nap or filament ends
showing.
c. Glass fabric is manufactured white in
color, and one source is precoated with a blue-
tinted dope as a primer and to reduce weave
distortion during handling. Thread count will
be approximately 36 threads per inch. Glass
fabrics are monofilament and will not have any
nap or filament ends showing unless they are
inadvertently broken.
d. When a small fabric sample can be
removed from the aircraft and all the coatings
removed, a burn test will readily distinguish
between natural fabric, polyester, and glass
fabric. Cotton and linen will burn to a dry ash,
polyester filaments will melt to a liquid and
continue burning to a charred ash, and glass
filaments, which do not support combustion,
will become incandescent over a flame.
2-32. COATING IDENTIFICATION.
Nitrate or butyrate dope must be used to de-
velop tension on cotton, linen, and glass fab-
rics. When a small sample can be removed,
burn tests will distinguish nitrate dope-coated
fabric from butyrate dope-coated fabric by its
immediate ignition and accelerated combus-
tion. Butyrate dope will burn at less than
one-half the rate of nitrate dope. Coating types
other than nitrate or butyrate dope may have
been used as a finish over dope on cotton,
linen, and glass fiber fabric coverings.
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