FAA Advisory Circular 43.13-1B
Acceptable Methods, Techniques, and Practices
Aircraft Inspection and Repair
AC 43.13-1B | 1. Wood Structure | 1. Materials and Practices | 1-2. Woods
9/8/98
CHAPTER 1. WOOD STRUCTURE
AC 43.13-1B
SECTION 1. MATERIALS AND PRACTICES
1-1. GENERAL. Wood aircraft construc-
tion dates back to the early days of certificated
aircraft. Today only a limited number of wood
aircraft structures are produced. However,
many of the older airframes remain in service.
With proper care, airframes from the 1930’s
through the 1950’s have held up remarkably
well considering the state of technology and
long term experience available at that time. It
is the responsibility of the mechanic to carefully
inspect such structures for deterioration and
continuing airworthiness.
1-2. WOODS.
a. Quality of Wood. All wood and ply-
wood used in the repair of aircraft structures
should be of aircraft quality (reference Army
Navy Commerce Department Bulletin
ANC-19, Wood Aircraft Inspection and Fabri-
cation). Table 1-1 lists some permissible
variations in characteristics and properties of
aircraft wood. However, selection and ap-
proval of woodstock for aircraft structural use
are specialized skills and should be done by
personnel who are thoroughly familiar with in-
spection criteria and methods.
b. Substitution of Original Wood. The
wood species used to repair a part should be
the same as that of the original whenever pos-
sible; however, some permissible substitutes
are given in table 1-1. Obtain approval from
the airframe manufacturer or the Federal
Aviation Administration (FAA) for the re-
placement of modified woods or other non-
wood products with a substitute material.
c. Effects of Shrinkage. When the
moisture content of a wooden part is lowered,
the part shrinks. Since the shrinkage is not
equal in all directions, the mechanic should
consider the effect that the repair may have on
the completed structure. The shrinkage is
greatest in a tangential direction (across the fi-
bers and parallel to the growth rings), some-
what less in a radial direction (across the fibers
and perpendicular to the growth rings), and is
negligible in a longitudinal direction (parallel
to the fibers). Figure 1-1 illustrates the differ-
ent grain directions and the effects of shrink-
age on the shape of a part. These dimensional
changes can have several detrimental effects
upon a wood structure, such as loosening of
FIGURE 1-1. Relative shrinkage of wood members due to drying.
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