Airframe Chapters (Wood Structure)

Where is information found concerning acceptable species substitutions for wood materials used in aircraft repair? a) AC 43. 13-1B b) aircraft specifications or type certificate data sheet c) technical standard orders

a) AC 43. 13-1B

Which of the following conditions will determine acceptance of wood with mineral streaks? a) careful inspection fails to reveal any decay. b) they produce only a small effect on grain direction. c) Local irregularities do not exceed limitations specified for spiral and diagonal grain.

a) careful inspection fails to reveal any decay. 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.

When patching a plywood skin, abrupt changes in cross-sectional areas which will develop dangerous stress concentration should be avoided by using a) circular or elliptical patches. b) square patches. c) doubles with any desired shaped patches.

a) circular or elliptical patches. 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.

A faint line running across the grain of a wood spar generally indicates a) compression failure. b) shear failure. c) decay

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

Laminated wood is sometimes used in the construction of highly stressed aircraft components. This wood can be identified by its a) parallel grain construction. b) similarity to standard plywood construction. c) perpendicular grain construction.

a) parallel grain construction. 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). Plywood is also made up of layers of wood, but the grain of each alternate layer runs at an angle to the ones next to it.

Pin knot clusters are permitted in wood aircraft structure provided a) they produce a small effect on grain direction. b) they have no mineral streaks. c) no pitch pocket are within 12 inches.

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

Glue deterioration in wood aircraft structure is indicated a) when a joi nt has separated and the glue surface shows only the imprint of the wood with no wood fibers clinging to the glue. b) when a joint has separated and the glue surface shows pieces of wood and/or wood fibers cling to the glue. c) by any joint separation.

a) when a joint has separated and the glue surface shows only the imprint of the wood with no wood fibers clinging to the glue. A satisfactory glue joint has the strength of the wood. When a glue joints 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.

Any wooden member that has been overstressed is subject to which type of failure? a) bond failure. b) compression failure. c) finished failure.

b) compression failure. Compression failure of a wood structure can take place when that wood structure is overstressed.

The strength of a well-designed and properly prepared wood splice joint is provided by the a) bearing surface of the wood fibers. b) glue. c) reinforcement plates.

b) glue. Completely by the glue. No other type of load-carrying fastener is used in a glues joint.

The cantilever wing uses a) external struts or wire bracing. b) no external bracing. c) the skin to carry most of the load to the wing butt.

b) no external bracing. 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.

In case of elongated bolt holes in a wood spar or cracks in the vicinity of bolt holes a) it is permissible to ream the hole, plug with hardwood, and red rill. b) the spar may be reinforced by using hardwood reinforcement plates c) a new section of spar should be spliced in or the spar replaced entirely.

c) a new section of spar should be spliced in or the spar replaced entirely. The only repair that is approved for an elongated bolt hole in a wood aircraft wing spar is to cut out the section of the par that contains the damage splice in a new section.

Compression failures in wood aircraft structures are characterized by buckling of the fibers that appear as streaks on the surface a) at right angles to the growth rings. b) parallel to the grain. c) at right angles to the grain.

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

Which statement about wood decay is correct? a) decay that occurs before the wood is seasoned does not affect the strength of the finished piece. b) a limited amount of certain kinds of decay is acceptable in aircraft wood since decay affects the binding between the fibers and not the fibers themselves. c) decay is not acceptable in any form or amount.

c) decay is not acceptable in any form or amount. 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.

The I-beam wooden spar is routed to a) increase strength. b) obtain uniform strength. c) reduce weight.

c) reduce weight 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.