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 | 2-8. Covering Methods
9/8/98
AC 43.13-1B
(5) For an overlapped and doped seam
on the perimeter of a wing (except a leading
edge), perimeters of wing control surfaces, pe
rimeters of empennage surfaces, and all areas
of a fuselage, on aircraft with a Vne speed up
to and including 150 mph, overlap the fabric
1 inch and cover with a finishing tape that is at
least 3 inches wide, centered on the outside
edge of the overlap seam.
2-8. COVERING METHODS.
The
method of fabric attachment should be identi
cal, as far as strength and reliability are con
cerned, to the method used by the manufac
turer of the airplane being recovered or re
paired. Carefully remove the old fabric from
the airframe, noting the location of inspection
covers, drain grommets, and method of at
tachment. Cotton or linen fabric may be ap
plied so that either the warp or fill-threads are
parallel to the line of flight. Either the enve
lope method or blanket method of covering is
acceptable.
a. The Envelope Method. A wing enve
lope may be developed by two methods. Ma
chine sew together, side by side multiple fabric
sections, cut to reach chordwise around the
wing, starting and ending at the trailing edge
with a minimum of 1 inch excess length. The
sewn envelope is then positioned around the
wing and secured with closely spaced T-Head
pins at the wingtip and trailing edge. Excess
material may then be trimmed. Carefully re
move the envelope and complete by machine
sewing at the wingtip and along the trailing
edge, except where the geometry of the wing
(aileron and flap cut out) would prevent the
sewn envelope from being reinstalled. After
reinstalling the envelope, the un-sewn sections
and butt end are then closed by hand-sewn or
overlapped and doped seams in accordance
with the aircraft Vne speed. (Refer to para
graph 2-7 b.)
(1) An alternative method, when fabric
of sufficient width is available, is to sew to
gether, side-by-side, two sections of fabric,
placing the seams spanwise on the leading
edge, then fit and sew the wingtip and trailing
edge in the same manner as the multiple piece
chordwise envelope.
(2) An envelope may be developed for
the fuselage in the same manner, with a final
closing along a longeron by hand-sewn or
overlapped and doped seams in accordance
with the aircraft Vne speed.
b. The Blanket Method. A blanket is
developed by sewing together, side-by-side,
multiple sections of fabric with the seams
chordwise or two wide sections of fabric,
side-by-side, placing the seam spanwise on the
leading edge, the same as an envelope. Close
the three remaining sides with a hand-sewn
seam or overlapped and doped seams in accor
dance with the aircraft Vne speed. Small
components may be covered by wrapping one
piece of fabric over a straight leading or trail
ing edge, then closing three sides with hand-
stitched or overlapped and doped seams in ac
cordance with the aircraft Vne speed.
NOTE: All overlapped and doped
seams will be made only over under-
lying supporting structures extending
the full width of the seam.
c. Machine-sewn alternate. An alternate
to machine-sewn seams on a wing envelope or
blanket is to use two sections of wide fabric
spanwise. Attach the fabric with overlapped
and doped seams at the leading and trailing
edge, wingtip and wing butt, in accordance
with the aircraft Vne speeds. (Reference para
graph 2-7 b.) Smaller components may be
covered in the same manner. The fuselage may
be covered with multiple fabric sections with
Par 2-7
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