Would structures

Question 1

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

Answer 1

Spruce is used as a standard of which all would your compared

Question 2

Is Northern white pine an acceptable substitute for spruce

Answer 2

Yes but only if the pine is larger to make up for it slower strength

Question 3

Are not allowed in aircraft wood

Answer 3

Knots are allowed if within limitations.

Factors that determine if knots are acceptable include the type of not, location, spacing, and number of nights

Question 4

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

Answer 4

The wood must be of aircraft quality an equivalent in its original strength or greater

Question 5

What is the difference between laminated wood and plywood

Answer 5

Laminated wood and plywood consist of two or more layers of wood which have been glued together.

Laminated wood has the grain of all layers approximately parallel. The grain of plywood runs 90° with the adjacent ply

Question 6

What are two types of glue used for Aircraft wood repair

Answer 6

They are casein and synthetic resin glue.

Question 7

What method is used to prepare plywood for bending

Answer 7

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

Question 8

What are the results of using insufficient gluing pressure When making a wood join

Answer 8

The results will normally be thick glue lines which indicate a week joint

Question 9

What is recommended clamping pressure for a glued join

Answer 9

125 to 150 psi

Question 10

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

Answer 10

Depending on the temperature of the curing room.

The curing temperatures are from 70°F and up. Higher temperatures will cause the glue to set faster. To be certain that the glue joint is satisfactory, it is recommended that it remain under pressure at about 85°F for a period of at least seven hours. Full joint strength will develop only after conditioning for at least two days

Question 11

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

Answer 11

Brad’s, nails, screws, clamps, or hydraulic an electrical power pressure

Question 12

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

Answer 12

Because and inaccurate bevel will reduce the amount of affective glue area

Question 13

Why is sanding unacceptable and preparing a joint for splicing

Answer 13

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

Question 14

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

Answer 14

A properly prepared and inserted scarf patch is the best repair for plywood, and it is preferred for most skin repairs. It differs from a splayed patch in that the edges are scarfed to a 12 to 1 slope instead of a 5 to 1 slope, and it uses reinforcements under the patch where the glue joint occurs

Question 15

Are mineral streaks acceptable in aircraft wood

Answer 15

Yes, providing careful inspection fails to reveal any decay

Question 16

How do you inspect for decay and would

Answer 16

Visual, odor, tapping, probe, prying

Question 17

How can the moisture content of would be determined

Answer 17

Use a moisture meter.

However, the most accurate method is to take a sample of the wood, wet, dry it in an oven at a temperature of 100 to 105°C, re-weigh it, and then compute the moisture content by using the following formula

W1-w2
———— x 100
W2

W1 equals the weight of the wood sample before drying

W2 equals the weight of the wood sample after drawing

Question 18

What area of wood spar may not be spliced

Answer 18

It may not be spliced or under the wing attachment fittings, landing gear fittings, engine mount fittings, or lift and interplane strut fittings

Question 19

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

Answer 19

A scarf joint

Question 20

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

Answer 20

high specific gravity and has the appearance of an excessive growth of Summer wood ( Hard, non-porous).

This defect is difficult to recognize and is very detrimental to strength. Reject all material containing compression would

Question 21

What are three forms of wood

Answer 21

Solid, ply, and laminate

Question 22

What are two forms of wood that are acceptable for the repair of wood Aircraft skins

Answer 22

The plywood and laminated woods are preferred for this application

Question 23

What would be the greatest amount of splices placed into one spar

Answer 23

2

Question 24

What is the largest whole diameter that can be repaired in a plywood wings spar when using a fabric patch

Answer 24

1 in.