6.3.2 Wooden Structures Flashcards

1
Q

What type of structure do fabric covered aircraft have

A

Truss type

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2
Q

What may the wing spars be made from

A

Sika spruce and may be solid or laminated

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3
Q

What is the advantage of a laminated spar over a solid spar

A

A laminated spar is just as strong and is much cheaper

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4
Q

What are the wing spars on wooden aircraft separated by

A

Compression members made of aluminium tubing or steel

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5
Q

What type of loads does a built up box spar take

A

Torsional and bending

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6
Q

What conditions should an aircraft be in for inspection purposes

A

In a dry well ventilated hangar with all inspection panels removed

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7
Q

What must be done before inspecting glued joints

A

The aircraft must be fully dried

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8
Q

What is the main problem associated with inspecting glued joints

A

There is no good non destructive testing

Access is difficult

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9
Q

What shape should access holes be

A

Access holes should be circular in shape and special tools used to avoid jagged edges

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10
Q

What must be done to the edges of all access holes

A

They must be smoothed with fine glass paper before inspection

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11
Q

What must be done before checking a glue line

A

All protective coatings must be removed by careful scraping

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12
Q

How is the inspection of a glue line carried out

A

With a magnifying glass and feeler gauge

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13
Q

What must be done if penetration is had on a glue line when inspecting

A

The piece must be rejected

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14
Q

How is dry rot identified

A

By small patches of crumbling wood

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15
Q

How would water penetration be identified in wood

A

Dark discolouration and grey streaks

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16
Q

What should be done to drain holes during routine maintenance

A

They should be cleaned out

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17
Q

How is a timber shrinkage inspection carried out

A

By removing paint or varnish and inserting a feeler gauge

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18
Q

What is had when elongated bolt holes are found

A

Can be due to landing or shear stresses

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19
Q

When would bruising or crushing be found

A

Where someone has over tightened a bolt

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20
Q

What type of loads are glued joints mainly designed to take

A

Shear loads

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21
Q

What is done to timber after it has been cut

A

It is stacked ready for shipment for 60 days

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22
Q

How is timber seasoned

A

In drying sheds for 1-3 years

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23
Q

Instead of waiting 1-3 years for timber to season, is there an alternative

A

Kiln drying

24
Q

What is the purpose of seasoning

A

To make sure the wood is in equilibrium with the surrounding atmosphere and it makes applying surface protection and finishes easier

25
Q

What must be done when the timber has been properly seasoned

A

It must be tested (6 inches from the end cut off first because it may be drier than the rest)

26
Q

How is the moisture content of timber determined

A

By weighing and drying or even better is the moisture meter

27
Q

What roughly should the moisture content be

A

15%

28
Q

How is the density of timber determined

A

By weighing and measuring

29
Q

What testing could be carried out on timber for brittleness

A

izod impact testing

30
Q

What rate of growth should be rejected

A

Less than 6 rings per 25mm

31
Q

How long should test pieces be kept for

A

No less than 2 years

32
Q

What type of sawing produces a flower face

A

Tangential sawing

33
Q

What two types of sawing are the same

A

Rift and quarter

34
Q

What is the worst of all defects found on timber

A

Dote disease

35
Q

What precaution is done to help prevent the felled tree having dote disease

A

It is cut 10 feet from the ground as dote disease lives at the root of the living tree

36
Q

How is dote disease recognised

A

Brownish yellow spots similar to mineral oil

37
Q

What must be done to timber that is suspected to have dote disease

A

It should be burnt because dote disease is contagious

38
Q

What is wood decay/rot

A

Symptoms similar to dote but occurs after the tree has been felled and promoted by large amounts of moisture

39
Q

What is the limit of grade inclination for grade A and grade B spruce

A

1 in 15 for grade A

1 in 12 for grade B

40
Q

What is heart shake

A

Follows a sap duct

Defect should be cut out of the timber

41
Q

What is ring shake

A

Occurs by the parting of the annular rings caused by frost

The defect should be cut from the timber

42
Q

What is the limit for knot size in timber

A

No larger than quarter of an inch diameter

43
Q

What is blue stain

A

Only occurs in sapwood

Should not be used in aircraft parts

44
Q

What is the advantage of using synthetic resin adhesives over mechanical methods when attaching wooden structures

A

Provide less stress on the joints over mechanical methods

45
Q

What two parts do synthetic resin adhesives normally consist of

A

The resin and the hardener

46
Q

In what forms can synthetic adhesives be had

A

Liquid and powder

47
Q

What type of synthetic resin adhesives typically have longer shelf lives

A

Powder - not susceptible to as much deterioration

48
Q

How are powder resins mixed

A

The powder is mixed with water before it is mixed with the hardener

It should not then be diluted

49
Q

Before gluing wooden structures what must be done

A

Must be sanded

50
Q

How many sides of the joint must be covered in adhesive

A

Both sides of the joint

51
Q

Some adhesives contain a solvent which needs to evaporate before the joint is made - what happens if the solvent doesn’t evaporate

A

Bubbles are created in the joint which forms a weakness

52
Q

What must be done when large surfaces are being glued together

A

Small vent holes should be drilled in the structure to allow trapped air to dissipate

53
Q

What is the advantage to applying heat to a glued surface

A

The setting time of the glue will decrease

54
Q

The fractured glued faces should show why when they have been tested

A

75% of wood fibres

55
Q

What type of joints should wet tests be carried out on

A

One that have been conditioned for at least 2-3 weeks

56
Q

In what form of stress do glued joints perform in its strongest form

A

Shear