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 | 2-30. General
9/27/01
SECTION 3. INSPECTION AND TESTING
AC 43.13-1B CHG 1
2-30. GENERAL. All components of the
covering should be inspected for general con-
dition. Loose finishing tape and reinforcing
patches; chafing under fairings; brittle, crack-
ing, peeling, or deteriorated coatings; fabric
tears and rock damage; broken or missing rib
lacing; and rodent nests are unacceptable. The
entire fabric covering should be uniformly taut
with no loose or wrinkled areas, or excess ten-
sion which can warp and damage the airframe.
a. Excess Tension. There are no methods
or specifications for measuring acceptable fab-
ric tension other than observation. Excess ten-
sion may warp critical components, such as
longerons, wing rib, and trailing edges out of
position, weakening the airframe structure.
(1) Excess tension with cotton, linen,
and glass fiber fabric covering is usually
caused by excessive dope film on a new cov-
ering, or continuous shrinking of an originally
satisfactory dope film as the plasticizers mi-
grate from the dope with age. Heat from sun
exposure accelerates plasticizer migration.
(2) Excess tension with polyester fabric,
coated with dope, is usually caused by the
combined tension of the heat tautened polyes-
ter fabric and continuous shrinking of the dope
film as the plasticizers migrate from the dope
with age.
b. Loose Fabric. Fabric that flutters or
ripples in the propeller slipstream, balloons, or
is depressed excessively in flight from the
static position, is unacceptable.
(1) Loose or wrinkled cotton, linen, and
glass fabric covering may be caused by inade-
quate dope film; poor quality dope; fabric in-
stalled with excess slack; or by a bent, broken,
or warped structure.
(2) Loose or wrinkled polyester fabric
covering, finished with coatings other than
dope, may be caused by inadequate or exces-
sive heat application; excess slack when the
fabric was installed; or bent or warped struc-
ture. Polyester fabric which does not meet air-
craft quality specifications will very likely be-
come loose after a short period of time.
(3) Glass fabric covering should be
tested with a large suction cup for rib lacing
cord failure and reinforcing tape failure caused
by chafing on all wing ribs and other structural
attachments throughout the airframe. Particu-
lar attention should be given to the area within
the propeller slipstream. If failure is indicated
by the covering lifting from the static position,
the rib lacing cord and reinforcing tape must
be reinstalled with double the number of origi-
nal laces.
NOTE: Temporary wrinkles will de-
velop in any fabric coated and fin-
ished with dope, when moisture from
rain, heavy fog, or dew is absorbed
into a poor-quality dope film, causing
the film to expand. Temporary wrin-
kles may also develop with any type of
thick coatings, on any type of fabric,
when an aircraft is moved from a cold
storage area to a warm hangar or
parked in the warming sunshine,
causing rapid thermal expansion of
the coating.
c. Coating Cracks. Fabric exposed
through cracks in the coating may be initially
tested for deterioration by pressing firmly with
a thumb to check the fabric’s strength. Natural
fibers deteriorate by exposure to ultraviolet ra-
diation, mildew, fungus from moisture, high
acid-content rain, dew, fog, pollution, and age.
Polyester filaments will deteriorate by expo-
sure to UV radiation.
Par 2-30
Page 2-33