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
AC 43.13-1B
9/8/98
TABLE 1-1. Selection and Properties of Aircraft Wood. (See notes following table.)
Species of Wood
Strength proper-
ties as compared
to spruce
Maximum
permissible
grain deviation
(slope of grain)
Remarks
1.
2.
3.
4.
Spruce(Picea) Sitka (P.
Excellent for all uses. Considered as standard for
Sitchensis) Red (P. Rubra)
100%
1:15
this table.
White (P. Glauca).
May be used as substitute for spruce in same sizes
or in slightly reduced sizes providing reductions are
Douglas Fir
Exceeds spruce.
1:15
substantiated. Difficult to work with handtools.
(Pseudotsuga Taxifolia).
Some tendency to split and splinter during fabrica-
tion and considerable more care in manufacture is
necessary. Large solid pieces should be avoided
due to inspection difficulties. Gluing satisfactory.
Slightly exceeds
Satisfactory characteristics with respect to work-
Noble Fir
spruce except
1:15
ability, warping, and splitting. May be used as di-
(Abies Nobiles).
8% deficient in
rect substitute for spruce in same sizes providing
shear.
shear does not become critical. Hardness some-
what less than spruce. Gluing satisfactory.
Slightly exceeds
Less uniform in texture than spruce. May be used
Western Hemlock
spruce.
1:15
as direct substitute for spruce. Upland growth su-
(Tsuga Heterpphylla).
perior to lowland growth. Gluing satisfactory.
Properties be-
Excellent working qualities and uniform in proper-
Pine, Northern White (Pinus tween 85 % and
ties, but somewhat low in hardness and shock-
Strobus).
96 % those of
1:15
resisting capacity. Cannot be used as substitute
spruce.
for spruce without increase in sizes to compensate
for lesser strength. Gluing satisfactory.
May be used as substitute for spruce in same sizes
White Cedar, Port Orford Exceeds spruce.
1:15
or in slightly reduced sizes providing reductions are
(Charaecyparis Lawsoni-
substantiated. Easy to work with handtools. Glu-
ana).
ing difficult, but satisfactory joints can be obtained
if suitable precautions are taken.
Poplar, Yellow (Liriodendrow Slightly less than
Excellent working qualities. Should not be used as
Tulipifera).
spruce except in
1:15
a direct substitute for spruce without carefully ac-
compression
counting for slightly reduced strength properties.
(crushing) and
Somewhat low in shock-resisting capacity. Gluing
shear.
satisfactory.
Notes for Table 1-1
1. Defects Permitted.
a. Cross grain. Spiral grain, diagonal grain, or a combination of the two is acceptable providing the grain does
not diverge from the longitudinal axis of the material more than specified in column 3. A check of all four faces of the
board is necessary to determine the amount of divergence. The direction of free-flowing ink will frequently assist in
determining grain direction.
b. Wavy, curly, and interlocked grain. Acceptable, if local irregularities do not exceed limitations specified for
spiral and diagonal grain.
c. Hard knots. Sound, hard knots up to 3/8 inch in maximum diameter are acceptable providing: (1) they are
not projecting portions of I-beams, along the edges of rectangular or beveled unrouted beams, or along the edges of
flanges of box beams (except in lowly stressed portions); (2) they do not cause grain divergence at the edges of
the board or in the flanges of a beam more than specified in column 3; and (3) they are in the center third of the
beam and are not closer than 20 inches to another knot or other defect (pertains to 3/8 inch knots—smaller knots
may be proportionately closer). Knots greater than 1/4 inch must be used with caution.
d. Pin knot clusters. Small clusters are acceptable providing they produce only a small effect on grain direction.
e. Pitch pockets. Acceptable in center portion of a beam providing they are at least 14 inches apart when they
lie in the same growth ring and do not exceed 1-1/2 inches length by 1/8 inch width by 1/8 inch depth, and providing
they are not along the projecting portions of I-beams, along the edges of rectangular or beveled unrouted beams, or
along the edges of the flanges of box beams.
f. Mineral streaks. Acceptable, providing careful inspection fails to reveal any decay.
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