FAA Advisory Circular 43.13-1B
Acceptable Methods, Techniques, and Practices
Aircraft Inspection and Repair
AC 43.13-1B | 4. Metal Structure, Welding, and Brazing | 4. Metal Repair Procedures | 4-58. Repair Methods and Precautions for Aluminum Structure
9/27/01
AC 43.13-1B CHG 1
used for patching plywood may be used. The
rivet pattern used, however, must follow stan
dard practice to maintain satisfactory strength
in the sheet.
g. Splicing of Sheets. The method of
copying the seams at the edges of a sheet may
not always be satisfactory. For example, when
the sheet has cutouts, or doubler plates at an
edge seam, or when other members transmit
loads into the sheet, the splice must be de
signed as illustrated in the following examples.
(1) Material: Clad 2024 sheet,
0.032 inch thickness. Width of sheet (i.e.,
length at splice) = “W” = 10 inches.
(2) Determine rivet size and pattern for
a single-lap joint similar to figure 4-5.
(a) Use rivet diameter of approxi
mately three times the sheet thickness,
3 x 0.032 = 0.096-inch. Use 1/8-inch 2117-T4
(AD) rivets (5/32-inch 2117-T4 (AD) would
be satisfactory).
(b) Use the number of rivets re
quired per inch of width “W” from table 4-10.
(Number per inch 4.9 x .75 = 3.7 or the total
number of rivets required = 10 x 3.7 or 37 riv
ets.) See notes in table.
(c) Lay out rivet pattern with spacing
not less than shown in figure 4-5. Referring to
figure 4-5(A), it seems that a double row pat
tern with the minimum spacing will give a to
tal of 40 rivets. However, as only 37 rivets are
required, two rows of 19 rivets each equally
spaced over the10 inches will result in a satis
factory splice.
h. Straightening of Stringers or Inter
mediate Frames. Members which are slightly
bent may be straightened cold and examined
with a magnifying glass for cracks or tears to
the material. Reinforce the straightened part to
its original shape, depending upon the condi
tion of the material and the magnitude of any
remaining kinks or buckles. If any strain
cracks are apparent, make complete reinforce
ment in sound metal beyond the damaged por
tion.
i. Local Heating. Do not apply local
heating to facilitate bending, swaging, flatten
ing, or expanding operations of heat-treated
aluminum alloy members, as it is difficult to
control the temperatures closely enough to
prevent possible damage to the metal, and it
may impair its corrosion resistance.
j. Splicing of Stringers and Flanges. It
is recommended that all splices be made in ac
cordance with the manufacturer’s recommen
dations. If the manufacturer’s recommenda
tions are not available, the typical splices for
various shapes of sections are shown in figures
4-17 through 4-19. Design splices to carry
both tension and compression, and use the
splice shown in figure 4-18 as an example il
lustrating the following principles.
(1) To avoid eccentric loading and con
sequent buckling in compression, place splic
ing or reinforcing parts as symmetrically as
possible about the centerline of the member,
and attach to as many elements as necessary to
prevent bending in any direction.
(2) To avoid reducing the strength in
tension of the original bulb angle, the rivet
holes at the ends of the splice are made small
(no larger than the original skin attaching riv
ets), and the second row of holes (those
through the bulbed leg) are staggered back
from the ends. In general, arrange the rivets in
the splice so that the design tensile load for the
member and splice plate can be carried into the
splice without failing the member at the out
ermost rivet holes.
Par 4-58
Page 4-27