FAA Advisory Circular 43.13-1B
Acceptable Methods, Techniques, and Practices
Aircraft Inspection and Repair
AC 43.13-1B | 2. Fabric Covering | 1. Practices and Precautions | 2-14. Inspection Rings and Drain Grommets
AC 43.13-1B
9/8/98
NOTE: It is important that any dam-
age found to ribs, such as oversize
rivet or screw holes, and cracks or
breaks in the rib cap, should be tagged
immediately for easy location and re-
pair later.
c. When repairs are made to fabric sur
faces attached by special mechanical methods,
duplicate the original type of fastener. When
self-tapping screws are used for the attachment
of fabric to the rib structure, observe the fol
lowing procedure:
(1) Redrill the holes where necessary
due to wear, distortion, etc., and in such cases,
use a screw one size larger as a replacement.
(2) Extend the length of the screw be
yond the rib capstrip at least two threads.
(3) Install a thin washer, preferably
aluminum, under the heads of screws and dope
pinked-edge tape over each screw head.
2-13. FINISHING TAPE.
a. Finishing tape (surface tape) is in
stalled after the fabric has been pulled taut
with the initial dope application. This proce
dure is performed to prevent ripples from
forming in fabric panels adjacent to newly ap
plied tapes. Ripple formation is caused by the
inability of the combined tape and fabric to
tighten uniformly with adjacent fabric when
additional dope is applied.
width should be sufficient to bond the fabric a
minimum of 3/8 inch on each side of all fabric
attachments. Two inch width tape is normally
used. Tapes over wing rib lacing should ex
tend a minimum of 1/2 inch past each end of
any reinforcing tapes. Random or widely-
spaced attachments may be covered by indi
vidual sections of fabric or finishing tape.
c. Installation of finishing tapes for ad
ditional wear resistance is recommended over
the edges of all fabric-forming structures. This
includes fuselage stringers, longerons, leading
and trailing edges, false or nose ribs, control
surfaces, and empennage ribs not already cov
ered and protected by a finishing tape that is
required to be on a fabric seam or fabric at
tached to the structure. Compound surfaces,
such as wingtip bow and empennage surfaces,
are more conveniently taped using bias cut
finishing tape, which easily conforms to the
compound contour, rather than notching linear
cut tape to fit the surface. Bias cut tape will be
reduced to approximately two thirds the origi
nal cut width when pulled tight around a
wingtip bow and should be considered when
selecting the width of tape for the various lo
cations.
d. Finishing tapes are applied by coating
the fabric surface over which the tape will be
applied with dope, applying the tape over the
wet dope film, then brushing the tape firmly
onto the fabric surface. This action will assure
a good bond by thoroughly saturating and wet
ting the finishing tape.
b. In addition to the tape widths re-
quired to be installed over fabric seams speci
fied in paragraph 2-7, finishing tape should be
installed as weather protection over all rib
lacing, screws, rivets, wire clips, or other de
vices used to secure fabric. This includes
wings, control surface ribs, empennage surface
ribs, and fuselage stringers, where so installed
by the original aircraft manufacturer. Tape
2-14. INSPECTION RINGS AND DRAIN
GROMMETS.
a. Inspection Rings. Inspection access is
provided adjacent to or over every control
bellcrank, drag-wire junction, cable guide,
pulley, wing fitting, or any other component
throughout the aircraft which will be inspected
or serviced annually. They are installed only
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