AF Wood Structures

Laminated wood spars may be substituted for solid rectangular wood spars

only in certain instances where the primary load is shared by one or more other original structural member.
if the same quality wood is used in both.
only upon specific approval by the manufacturer or the FAA.

The strength of a well-designed and properly prepared wood splice joint is provided by the

bearing surface of the wood fibers.
glue.
reinforcement plates.

Where is information found concerning acceptable species substitutions for wood materials used in aircraft repair?

AC 43.13-1B.
Aircraft Specifications or Type Certificate Data Sheets.
Technical Standard Orders.

In cases of elongated bolt holes in a wood spar or cracks in the vicinity of bolt holes,

it is permissible to ream the hole, plug with hardwood, and re-drill.
the spar may be reinforced by using hardwood reinforcing plates.
a new section of spar should be spliced in or the spar replaced entirely.

A faint line running across the grain of a wood spar generally indicates

compression failure.
shear failure.
decay.

Any wood member that has been overstressed is subject to which type of failure?

Stretch.
Compression.
Torsion.

Which statement about wood decay is correct?

Decay that occurs before the wood is seasoned does not affect the strength of the finished piece.
A limited amount of certain kinds of decay is acceptable in aircraft woods since decay affects the binding between the fibers and not the fibers themselves.
Decay is not acceptable in any form or amount.

Which statement concerning wood decay is correct?

Decay that appears to be mineral streaks is acceptable.
A limited amount of decay along the beveled edges of unrouted beams is acceptable.
Any form or amount of decay is not permitted.

Which of the following conditions will determine acceptance of wood with mineral streaks?

Careful inspection fails to reveal any decay.
They produce only a small effect on grain direction.
Local irregularities do not exceed limitations specified for spiral and diagonal grain.

The I-beam wooden spar is routed to

increase strength.
obtain uniform strength.
reduce weight.

Pin knot clusters are permitted in wood aircraft structure provided

they produce a small effect on grain direction.
they have no mineral streaks.
no pitch pockets are within 12 inches.

The cantilever wing uses

external struts or wire bracing.
no external bracing.
the skin to carry most of the load to the wing butt.

Laminated wood is sometimes used in the construction of highly stressed aircraft components. This wood can be identified by its

parallel grain construction.
similarity to standard plywood construction.
perpendicular grain construction.

When patching a plywood skin, abrupt changes in cross-section areas which will develop dangerous stress concentration should be avoided by using

circular or elliptical patches.
square patches.
doublers with any desired shaped patches.

Glue deterioration in wood aircraft structure is indicated

when a joint has separated and the glue surface shows only the imprint of the wood with no wood fibers clinging to the glue.
when a joint has separated and the glue surface shows pieces of wood and/or wood fibers clinging to the glue.
by any joint separation.

Compression failures in wood aircraft structures are characterized by buckling of the fibers that appear as streaks on the surface

at right angles to the growth rings.
parallel to the grain.
at right angles to the grain.

AF Wood Structures

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