Chapter 3 - Wood, Composite, and Transparent Plastic Structures - Oral Questions Flashcards
What are three forms of wood commonly used in aircraft construction?
Solid, laminated, and plywood
What type of would should be used when splicing or reinforcing plywood webs?
The same type of plywood as originally used
Name at least four different types of defects found in wood
Knots, checks, splits, pitch pockets, cross grain, curly grain, decay, dry rot
Can a section of wood containing a hard knot be used?
Yes, within specified limits
What type of glue may have been used in older wooden aircraft construction that requires careful inspection to detect deterioration?
casein glue
What are the three types of glues used in modern aircraft construction and repair?
Resorcinol glue
phenol-formaldehyde glue
epoxy resin glue
Is compression wood acceptable for structural repairs?
no
Why should the various pieces of wood being joined be kept in the same room for at least 24 hours prior to joining?
To allow the moisture content to equalize, minimizing dimensional changes
Why is it important to consider the open-assembly time when gluing wooden structures?
If the maximum open-assembly time is exceeded the joint may fail since the glue may begin setting up before the joint is assembled
Why is it important to apply the proper clamping pressure to a glue joint?
Clamping forces air out of the joint, brings the surfaces together evenly, and is responsible for the strength of the glue line
Describe some of the methods used to apply pressure to glue joints
Clamps,
nailing strips,
power presses,
brads,
nails,
and small screws
What minimum curing temperature should be observed when joining wood with various adhesives?
70 degrees F or as specified by the manufacturer
When inspecting wood structures, why is it important to consider stains and discolored areas?
They usually accompany decay or rot
Describe the acceptable methods used to repair elongated bolt holes found in a wooden wing spar
Remove the section containing the elongated holes and splice in a new section, or replace the entire spar
What type of joint is used to splice a solid or rectangular wood spar?
A scarf joint
Where are splices to a wood spar prohibited?
Under an attachment fitting for the wing root,
landing gear,
engine mount, lift,
or inter plane strut
What is the max number of splices for a single spar?
2
Describe the characteristics of a scarf joint
The pieces are tapered or beveled on a slope of 1 to 10 or 1 to 12
Why must the beveled cut be accurate on both pieces of wood with a scarf joint?
They must match exactly for a tight glue joint
What are the two primary uses for plywood in aircraft construction?
Gusset (reinforcing) plates, and aircraft skin
Give three examples of plywood skin repairs
Splayed patches,
surface patches,
plug patches,
scarfed patches
What type of patch should be used to repair small holes in thin plywood skin if the skin is less than 1/10th inch thick?
A splayed patch may be used if the hole can be cleared out to a diameter of less than 15 thicknesses of the skin
What should be done to prevent a plywood patch and the pressure plate from sticking together if glue is extruded from the joint?
Place waxed paper or vinyl plastic between the patch and the plate
Why are lightweight steel bushings sometimes used in wooden structures?
Bushings prevent the wood from being crushed when bolts are tightened
