1. Wood Structure

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

A compression failure in a piece of wood is identified by a faint line running across the grain of the wood.

Glue deterioration in wood aircraft structure is indicated

A satisfactory glue joint has the strength of the wood. When a glue joint fails, the wood fibers should separate before the glue fails. If the joint separates with no wood fibers clinging to the glue, the glue has deteriorated.

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

Laminated wood is made up of a number of pieces of wood glued together with the grain of all the pieces running in the same direction (parallel to each other).

Which statement about wood decay is correct?

When inspecting a wooden aircraft structure, examine all stains and discolorations carefully to determine whether or not they are harmless or in a stage of preliminary or advanced decay. All pieces must be free from rot, dote, red heart, purple heart, and all other forms of decay.

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

Wood having mineral streaks is acceptable for aircraft structure, provided careful inspection does not reveal any decay. Mineral streaks have no effect on the direction of the grain in the wood.

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

a new section of spar should be spliced in or the spar should replaced entirely

Laminated wood spars may be substituted for solid rectangular wood spars?

if the same quality of wood is used in both

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

Compression failure in aircraft structural wood is characterized by a streak on the surface of the wood at right angles to the grain.

Non-acceptable wood defects are?

Cross grain, Wavy, curly, and interlocked grain, Hard knots, Pin knot clusters, Spike knots, Pitch pockets, Mineral streaks, Checks, shakes, and splits, any kind of Compression failures and Decay

Acceptable wood defects are?

Cross grain, Wavy, curly, and interlocked grain, Hard knots, Pin knot clusters, and Pitch pockets

The cantilever wing uses

A cantilever wing has all its strength inside its structure. The wing spars are built in such a way that they carry all the bending and torsional loads. A cantilever wing uses no external bracing.

The I-beam wooden spar is routed to

A wooden I-beam wing spar is routed to reduce its weight. The material removed is in the web of the spar, and there is very little strength lost by removing this material.

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

AC 43.13-1B.

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

Circular or elliptical patches are used when patching aircraft plywood skin to prevent abrupt changes in the cross-sectional area of the skin. If a rectangular or triangular patch is used, the corners must have ample radii.

Pin knot clusters are permitted in wood aircraft structure provided

Pin knot clusters in a piece of aircraft structural wood are permitted if they are small clusters and produce only a small effect on grain direction.

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

glue