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

Question 3

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

Answer 3

Yes, within specified limits.

Question 4

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

Answer 4

Casein glue.

Question 5

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

Answer 5

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

Question 5

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

Answer 5

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

Question 6

Is compression wood acceptable for structural repairs?

Answer 6

No

Question 7

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

Answer 7

The allow the moisture content to equalize, thereby minimizing dimensional changes int he wood.

Question 7

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

Answer 7

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 8

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

Answer 8

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

Question 8

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

Answer 8

70 degrees F or as specified by the glue manufacturer

Question 9

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

Answer 9

Stains and discoloration usually accompany decay and/or rot.

Question 10

Describe the acceptable methods used to repair elongated bolt bolts found in a wooden wing spar?

Answer 10

Remove the section containing the elongated holes and splice in a new section or replace the entire spar.

Question 11

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

Answer 11

Two

Question 11

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

Answer 11

A scar joint

Question 12

In what areas are splices to a wood spar prohibited?

Answer 12

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

Question 13

Describe the characteristics of a scar joint.

Answer 13

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

Question 14

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

Answer 14

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

Question 15

What are two primary uses for plywood in aircraft construction?

Answer 15

Gusset plates and aircraft skin

Question 16

Provide examples of at least three types of plywood skin repairs

Answer 16

Splayed patches, surface patches, plug patches and scarfed patches

Question 17

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 17

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

Question 18

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

Answer 18

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

Question 19

Why are lightweight steel bushings sometimes used in wooden structures?

Answer 19

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

Question 20

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

Answer 20

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

Question 20

Describe the construction of a bonded honeycomb structure.

Answer 20

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

Question 21

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

Answer 21

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

Question 22

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

Answer 22

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

Question 23

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

Answer 23

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

Question 24

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

Answer 24

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

Question 25

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

Answer 25

Filling a hole.

Question 26

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

Answer 26

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

Question 27

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

Answer 27

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