Wood Structures

Question 1

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

Answer 1

Spruce is standard of which all woods are compared

Question 2

2. Is northern white pine an acceptable substitute for spruce?

Answer 2

Yes

Question 3

3. Are knots allowed in aircraft wood?

Answer 3

Allowed within limits

Question 4

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

Answer 4

Aircraft quality & equivalent to its original strength or greater

Question 5

5. What is the difference between laminated wood & plywood?

Answer 5

Consist of two or more layers glued together
Laminate has grain parallel
Plywood grain is 90 degrees adjacent ply

Question 6

6. What are two types of glue used for aircraft wood structures repair?

Answer 6

Casein & synthetic resin glue

Question 7

7. What method is used to prepare plywood for bending?

Answer 7

Soaked in hot water, then placed in a form until completely dry

Question 8

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

Answer 8

Normally be a thick glue line, indicates weak joint

Question 9

9. What is the recommended clamping pressure for a glued joint?

Answer 9

125-150 psi

Question 10

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

Answer 10

Time varies depending on temperature of room

Recommended room temperature of 85 degrees under pressure for at least 7 hours full strength after two days

Question 11

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

Answer 11

Brads
Nails
Screws
Clamps
Hydraulic & electric power presses

Question 12

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

Answer 12

Inaccurate bevel will reduce amount of effective glue area

Question 13

13. Why is sanding unacceptable when preparing a joint for splicing?

Answer 13

Dust from sanding clogs pores, preventing proper glue penetration

Question 14

14. What type of patch is preferred for repair of stressed plywood skin & why?

Answer 14

Scarf patch it uses reinforcements under the patch where the flue joints occur

Question 15

15. Are mineral streaks acceptable in aircraft woods?

Answer 15

Yes, as long as no decay

Question 16

16. How do you inspect for decay/rot in wood?

Answer 16

Visual
Odor
Tapping
Probe
Prying

Question 17

17. How can the moisture content of wood be determined?

Answer 17

Moisture meter

Question 18

18. What are of the wood spar may not be spliced?

Answer 18

Under wing attachment fittings
Landing gear fittings
Engine mount fittings
Lift & inter-plane strut fittings

Question 19

19. What type of joint is generally used in splicing structural member in aircraft?

Answer 19

Scarf joint

Question 20

20. What is compression wood & why is it not acceptable for aircraft structures?

Answer 20

Wood with high specific gravity and weak, reject all material

Question 21

21. What are three forms of wood?

Answer 21

Solid
Ply
Laminate

Question 22

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

Answer 22

Plywood & laminate woods

Question 23

23. What would be the greatest number of splices place into one spar?

Answer 23

Two

Question 24

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

Answer 24

1 inch