FAA Advisory Circular 43.13-1B
Acceptable Methods, Techniques, and Practices
Aircraft Inspection and Repair
AC 43.13-1B | 1. Wood Structure | 3. Inspection | 1-29. Inspection Methods
AC 43.13-1B
9/8/98
subjected to the compression load. An area of
grain waviness would indicate a potential
compression failure. In all cases the manufac-
turer’s inspection data should be followed.
g. Moisture Meters are effective tools for
detection of excessive moisture content in
wood members. An instrument such as this
allows the mechanic to insert a probe into the
wood member and read its moisture content di-
rectly off the meter. A correction chart usually
accompanies the instrument to correct for tem-
perature and species of wood. Any reading
over 20 percent indicates the probability of
fungus growth in the member. Moisture con-
tent of the wood should be 8-16 percent, pref-
erably in the 10-12 percent range (this range is
during inspection). Where plywood skin cov-
ers the spar and the spar would be inaccessible
without removing the skin, the moisture meter
probe can be inserted through the plywood
skin and into the spar to check the moisture
content of the spar. The small holes made by
the probe are easily sealed.
h. Destructive testing of sample bonded
joints whenever a new bond joint is made, a
sample joint should be made with the adhesive
from the same batch used on the repair and
scraps of wood left over from the repair. After
curing, the sample joint should be destruc-
tively tested to ensure proper bonding of the
two wood pieces. Any failure in the bond line
indicates a cohesive failure of the adhesive.
Any failure along the bond line indicates an
adhesive failure, which is indicative of poor
bonding. The ideal situation is when wood fi-
bers are observed on both sides of the fracture
surface. This indicates a failure in the wood,
and indicates the bond joint is actually stronger
than the wood.
1-30.1-35. [RESERVED.]
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