FAA Advisory Circular 43.13-1B
Acceptable Methods, Techniques, and Practices
Aircraft Inspection and Repair
AC 43.13-1B | 1. Wood Structure | 4. Repairs | 1-46. Rib Repairs
AC 43.13-1B
If splice is made where routing is feathered to full width of spar, tapered
plates (conforming to the contour of the routing) should be added first;
otherwise, the splice is the same as shown.
9/8/98
Reinforcement plates may be of plywood, the same material as the
spar, or material of equal or higher quality; and should be bonded
only with ends feathered out with a 5:1 slope.
FIGURE 1-6. Method of splicing solid “I” spars.
in the same storage area as the part to be re-
paired, for no less than 2 weeks.
c. Preventing Cracks. An important step
in the prevention of longitudinal cracking,
particularly in spar butts, is to ensure that the
wood is thoroughly sealed with a penetrating
and highly moisture-resistant finish. Applica-
tion of a thin, slow-curing epoxy adhesive or
sealer can be very effective in slowing or pre-
venting moisture changes in spar butts.
1-45. ELONGATED HOLES IN SPARS.
In cases of elongated bolt holes in a spar, or
cracks in the vicinity of bolt holes, splice in a
new section of spar, or replace the spar en-
tirely. If hole elongation or cracking is mini-
mal and the bolt holes are for noncritical fit-
tings, repair (rather than replacement) may be
feasible. Obtain approval for any such repair
from the manufacturer or a representative of
the FAA. In many cases, it has been found ad-
vantageous to laminate the new section of the
spar, particularly if the spar butts are being re-
placed.
1-46. RIB REPAIRS. Ribs may be replaced
by new parts made by the manufacturer or the
holder of a PMA for that part. Owner-
produced ribs may be installed providing they
are made from a manufacturer-approved
drawing or by reference to an existing original
rib. A rib may be made by reference to an ex-
isting rib providing sufficient evidence is pre-
sented to verify that the existing rib is an
original part and that all materials and dimen-
sions can be determined. The contour of the
rib is important to the safe flying qualities of
the aircraft, and care should be taken that any
replacement ribs accurately match the manu-
facturer’s original design.
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