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