Section II Airframe Structures (wood 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 Wood is the benchmark to which all woods are compared.

Question 2

Is Northern White Pine an acceptable substitute for spruce?

Answer 2

Yes, but only if the pine is a larger size to make up for its lower strength.

Question 3

Are knots allowed an aircraft wood?

Answer 3

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

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 and equivalent to its original strength or greater.

Question 5

What is the difference between laminated wood and plywood?

Answer 5

Laminated wood grain runs parallel and plywood runs 90° with adjacent ply.

Question 6

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

Answer 6

Casein and synthetic resin glue.

Question 7

What is the method used to prepare plywood for bending?

Answer 7

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

Question 8

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

Answer 8

The results will normally be thick glue lines, which indicate a weak joint.

Question 9

What is the recommended clamping pressure for a glued joint?

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

The pressure time will vary depending on the temperature of the curing room. Higher temps will cause the glue to set faster. It is recommended that it remain under pressure for at least 7 hours.

Question 11

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

Answer 11

Brads , nails , screws, clamps, or hydraulic and electrical power presses.

Question 12

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

Answer 12

because an inaccurate bevel will reduce the amount of effective glue area.

Question 13

Why is sanding unacceptable when preparing a joint for splicing?

Answer 13

The dust created from sanding will clog the pores of the 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 Scarf patch is the best repair for plywood , and is preferred for most skin repairs.It uses reinforcements under the patch where the glue joints occur.

Question 15

Are mineral streaks acceptable in aircraft wood?

Answer 15

Yes, providing careful inspection fails to reveal any decay.

Question 16

How would you inspect for decay/rot in wood?

Answer 16

Visual (dark discoloration or gray stains ), Odor (musty or moldy), Tapping (sharp solid report), Probe (sharp metal tool), Prying (bonded joints).

Question 17

How can the moisture content of wood be determined?

Answer 17

Use a moisture meter. The most accurate method is to take a sample of the word, wet, dry it on an oven at a temperature of 100°C to 105°C, reweigh it, and then compute the moisture content by using the formula.

Question 18

What area of the wood spar may not be spliced?

Answer 18

It may not be spliced under the wing attachment fittings, landing gear fittings, engine mount fittings or lift and interplain Strat fittings.

Question 19

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

Answer 19

A scarf joint

Question 20

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

Answer 20

Compression worries would that is characterized by high specific gravity and has appearance of 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 wood.

Question 21

What are three forms of wood ?

Answer 21

Solid , Ply , Laminate

Question 22

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

Answer 22

Plywood and laminated wood

Question 23

What would be the greatest amount of spices placed into one spar?

Answer 23

Two

Question 24

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

Answer 24

1 inch

Question 25

what determines the required quality and strength of fabric that is we use for covering aircraft?

Answer 25

It is determined by the pounds per square foot of wing load, and then never exceed their speed of the aircraft aircraft.