WOOD, COMPOSITE, AND TRANSPARENT PLASTIC STRUCTURES

Question 1

What are the three forms of wood commonly used in aircraft construction?

Answer 1

Solid, Laminated, and Plywood.

Question 2

What type of wood should be used when splicing or reinforcing plywood webs?

Answer 2

The same type of plywood as originally used.

Question 3

Name at least four different types of defects found in wood

Answer 3

Knots, Checks, Splits, Pitch pockets, Cross grain, curly grain, decay, dry rot, etc.

Question 4

Can a section of wood containing a hard knot be used?

Answer 4

Yes, within specified limits.

Question 5

What type of glue may have been used in older wooden aircraft construction that requires careful inspection to defect deterioration?

Answer 5

Casein glue.

Question 6

What are the three types of glued used in modern aircraft construction and repair?

Answer 6

Resorcinol glue, Phenol-formaldehyde glue, and epoxy resin glue.

Question 7

Is compression wood acceptable for structural repairs?

Answer 7

NO

Question 8

Why should the various pieces of wood being joined be kept in the same room for at least 24 hours prior to joining?

Answer 8

To allow the moisture content to equalize, thereby minimizing dimensional changes in the wood.

Question 9

Why is it important to consider the open-assembly time when gluing wooden structures?

Answer 9

If the maximum open-assembly time is exceeded, the joint may fail since the glue may begin setting up before the joint is assembled.

Question 10

Why is it important to apply the proper clamping pressure to a glue joint?

Answer 10

Clamping forced air out of the joint, brings the wood surfaces together evenly and is, in part, responsible for the strength of the glue line.

Question 11

Describe some of the methods used to apply pressure to glue joints.

Answer 11

Clamps, nailing strips, power presses, brads, nails, and small screws.

Question 12

That minimum curing temperature should be observed when joining wood with various adhesives?

Answer 12

70 degrees Fahrenheit or as specified by the glue manufacturer.

Question 13

When inspecting wood structures, why might it be important to consider stains and discolored areas?

Answer 13

Stains and discoloration usually accompany decay and/ or rot.

Question 14

Describe the acceptable methods used to repair elongated bolt holes found in a wooden wing spar.

Answer 14

Remove the section containing the elongated hole(s) and splice in a new section or replace the entire spar.

Question 15

What type of joint is used to splice a solid or rectangular wood spar?

Answer 15

A scarf joint

Question 16

In what areas are splices to a wood spar prohibited?

Answer 16

Under an attachment fitting for the wing root, landing gear, engine-mount, lift, or inter-plane strut.

Question 17

What is the maximum number of splices allowed for any single spar?

Answer 17

TWO.

Question 18

Describe the characteristics of a scarf joint?

Answer 18

The pieces to be joined are tapered or beveled on a slope of 1 to 10 or 1 to 12.

Question 19

Why must the beveled cut be accurate on both pieces of wood being repaired with scarfed joint?

Answer 19

The two pieces must match exactly to ensure a tight glue joint.

Question 20

What are the two primary uses for plywood in aircraft construction?

Answer 20

Gusset (or reinforcing) plates and aircraft skin.

Question 21

Provide examples of at least three types of plywood skin repairs.

Answer 21

Splayed patches, surface patches, plug patches, and scarfed patches.

Question 22

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?

Answer 22

A splayed patch may be used if the hole can be cleared out to a diameter of less than 15 thickness of the skin

Question 23

What should be done to prevent a plywood patch and the pressure plate from sticking together if glue is extruded from the joint?

Answer 23

Place a piece of waxed paper or vinyl plastic between the patch and the pressure plate.

Question 24

Why are lightweight steel bushings sometimes be used in wooden structures?

Answer 24

Bushings prevent the wood from being crushed when bolts are tightened.

Question 25

What is the purpose of large surface area washers when used on wooden structures?

Answer 25

Large washers prove additional bearing area for hardware to help preclude damage to the wood when the hardware is tightened.

Question 26

Name several facings and core materials used in bonded honeycomb structures intended for special applications.

Answer 26

Stainless steel, titanium, magnesium, plywood, glass, nylon, and cotton cloth.

Question 27

Describe the construction of a bonded honeycomb structure.

Answer 27

It is a laminated structure that has a solid facing bonded to either side of a core consisting of open, six-sided cells.

Question 28

What must be done with damaged area in a bonded honeycomb structure prior to beginning repairs?

Answer 28

The area must first be inspected to determine the damaged area prior to completely removing the damaged material.

Question 29

A drill bit used for drilling composites should operate at approximately what speed?

Answer 29

Use an air-driven tool capable of a free speed of up to 20, 000 rpm.

Question 30

What are the most common causes for delamination of a composite structure?

Answer 30

Sonic vibration, expansion of internal moisture, liquid leakage, and a manufacturing error.

Question 31

What type of defect in, or damage to, a bonded honeycomb structure can be repaired using the potted repair method?

Answer 31

Filling a hole.

Question 32

Name some of the factors that cause crazing in transparent plastic windows and windshields?

Answer 32

Exposure to ultraviolet light, stress, solvents, and improper handling.

Question 33

How should a hole be drilled in plexiglas to avoid damage to the hole when the drill breaks through to the underside?

Answer 33

Back up the plastic with a piece of wood and feed the drill slowly.