Airframe Structures: Wood Structures 🔊 Flashcards

1
Q

What species of wood is used as a standard for strength properties of other species of wood used in aircraft structures?

A

Spruce

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2
Q

Is northern white pine an acceptable substitute for spruce?

A

Yes, but only if its larger in size to make up for the lower strength

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3
Q

Are knots allowed in aircraft wood?

A

Yes, within limitations (type, location, spacing, and number)

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4
Q

What type of wood quality must be used in the repair of aircraft structures?

A

Must be aircraft quality and equivalent to its original strength or greater

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5
Q

What is the difference between laminated wood and plywood?

A

Both consist of two or more layers of wood which have been glued together. Laminated wood has the grain of all layers approximately parallel. Plywood grain runs 90° with adjacent ply.

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6
Q

What are two types of glue used for aircraft wood structure repair?

A

Casein and synthetic resin glue

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7
Q

What method is used to prepare plywood for bending?

A

The wood is soaked in hot water then placed in a form until completely dry

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8
Q

What are the results of using insufficient gluing pressure when making a wood joint?

A

Thick glue lines which indicate a weak joint

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9
Q

What is the recommended clamping pressure for a glued joint?

A

125 to 150 psi

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10
Q

How long should a wood glue joint be kept under pressure before removing the clamps?

A

Time will vary depending on the temperature of the room. Higher temperature cures glue faster. (85° for at least 7 hours; full joint strength after two days)

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11
Q

What are some of the various methods used to apply pressure to joints in aircraft gluing operations?

A

Brads, nails, screws, clamps, or hydraulic and electric power presses

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12
Q

Why does the strength of a scarf joint depend upon the accuracy of the two beveled surfaces?

A

An inaccurate bevel will reduce the amount of effective glue area

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13
Q

Why is sanding unacceptable when preparing a joint for slicing?

A

The dust created from sanding will clog the pores of the wood, preventing the proper penetration of glue.

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14
Q

What type of patch is preferred for repair of stressed plywood skin and why?

A

Scarf patch; Scarfed patches are 12 to 1 slope and it uses reinforcements under the patch where the glue joints occur.

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15
Q

Are mineral streaks acceptable in aircraft wood?

A

Yes

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16
Q

How do you inspect for decay/rot in wood?

A

Visual, odor, tapping, probe, or prying

17
Q

How can the moisture content of wood be determined?

A

A moisture meter or more accurately take a sample, weigh it, then dry it in an oven at 100°C to 105°C, and reweigh it.

18
Q

What area of the wood spar may not be spliced?

A

Under wing attachment fittings, landing gear fittings, engine mount fittings, or lift-and-interplane strut fittings

19
Q

What type of joint is generally used in splicing structural members in aircraft?

A

A scarf joint

20
Q

What is compression wood and why is it not acceptable for aircraft structures?

A

It is characterized by high specific gravity and has the appearance of an excessive growth of summer wood. This defect is difficult to recognize and is very detrimental to strength.

21
Q

What are three forms of wood?

A

Solid, ply, and laminated.

22
Q

What are two forms of wood that are acceptable for the repair of wooden aircraft skin?

A

Plywood or laminated woods

23
Q

What would be the greatest number of splices placed into one spar?

A

Two

24
Q

What is the largest hole diameter that can be repaired in a plywood wing skin when using a fabric patch?

A

1 inch