Wood

What is the steepest acceptable slope of a scary cut in a spar repair?

15:1

Laminated wood can be identified by?

2 or more layers of wood glued together with the grain of all layers or laminations approximately parallel

What is the best repair for most damaged plywood?

A scarf patch.

Can a plug patch be used in an area that suffered structural damage beneath the skin?

No, it is only a skin repair

What is the simplest repair method to repair a hole in plywood 1" or less in diameter?

a fabric patch

what type of patch is a splayed patch?

a flush patch, 5:1

In cases of elongated boltholes in a wood spar or cracks in the vicinity of bolt holes, what must be done?

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

What does insufficient pressure to a glue joint produce?

a thick glue line, indicating a weak joint

The amount of time glue can be safely used after being mixed is called what?

adhesive pot life

What type of woods are distributed by reputable aircraft suppliers?

aircraft grade

Describe aircraft plywood construction.

an odd number of piles are glued together with the grains of each layer placed 90° with the adjacent layer

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

circular or elliptical patches

What conditions would determine acceptance of wood with mineral streaks?

if inspection doesnt reveal decay

Laminated wood spars may be substituted for solid rectangular wood spars

if the same quality 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 in what direction compared to the grain?

right angles to the grain

Most commonly used repair method for a wing rib?

scarf splice

What are the three types of wood used in aircraft manufacture and repair?

solid, laminated, plywood

Who is the person that certifies wood that is used in construction or repair in certificated aircraft?

the A+P mechanic/technician

what provides the strength in a glue joint using brads?

the adhesive (glue)

adhesive pot life?

the amount of time an adhesive can still be used after it is mixed

Who must be satisfied with the repair of wood damage before the log book is completed and signed?

the technician/A+P Mechanic

Define closed assembly time

time between the assembly of the joints and the application of pressure

What is the purpose of using brads, staples, or screws in wooden assemblies?

to create and keep pressure on a joint. can be left in wood so long as made of brass

Describe laminated wood assembly.

two or more layers of wood that have been glued together with the grain of all layers parallel

How does temperature affect the cure of a glue joint?

weakens the joint (if higher than 70°F the temp will shorten the assembly time)

What could be considered the ideal range of moisture content for wood?

8-12%

what publication can be utilized to determine acceptable repair methods for wood structure?

AC 43.13-1B

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

AC 43.13-1B/2B

what type of glues should now be considered obsolete?

Casein and plastic resin

If the repair is considered major, what document must be completed and approved?

Form 337

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

Glue joint, not the screws or nails used to create pressure

Which species of wood is considered the primary based on strength and weight properties?

Sitka spruce

A faint line running across the grain of a wood spar generally indicates what type of failure?

compression failure

What are some factors that might cause glue joint deterioration?

development of fungal growth, mechanical forces caused mainly by wood shrinkage, and chemical reactions caused by aging, moisture, extreme temperatures, or a combination.

Visual indicator of rot?

discoloration

Pin knot clusters are permitted in wood aircraft structure provided what circumstances?

if they produce only a small effect on grain direction

What should NOT be used in spar repairs?

nails or screws

The cantilever wing uses what for strength?

no external bracing, uses internal wing spars for strength

Which type of the three forms of wood is typically being repaired if a splayed patch is being used in the repair process?

plywood

The I-beam wooden spar is routed to?

reduce weight

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 (an irregular appearance)

A damaged spar unless specified by the manufacturer, can be spliced most anywhere except where?

wing attachment, landing gear, engine mount, and lift-and-interplanetary strut fittings