SUBJECT A. METALLIC STRUCTURES

Question 1

1. What are key areas to consider when inspecting a metal structure? (AM.II.A.K1)

Answer 1

a. Inspect riveted joints, looking for chipped or cracked paint that may indicate shifted or loose rivets. Smoking around rivets indicates movement, or fretting rivets. Check for cracked rivets and missing shop and manufactured heads.
b. Look for cracks near rivets or stressed areas.
c. Inspect for corrosion.

Question 2

2. What are the types of damage and defects that may be observed on sheet metal aircraft parts? (AM.II.A.K2)

Answer 2

Brinelling, burnishing, burr,
corrosion, crack, cut, chattering,
dent, erosion,
galling, gouge, inclusion,
nick, pitting,
scratch, score, stain, upsetting.

Question 3

3. What is one of the most important considerations when selecting materials for a sheet metal repair? (AM.II.A.K3)

Answer 3

The repair material must duplicate the strength of the original structure.

Question 4

4. For maximum strength of a formed sheet metal fitting, should the bend be made along or across the grain of the metal? (AM.II.A.K4)

Answer 4

Across the grain.

Question 5

5. What determines the minimum bend radius that can be used when forming a sheet metal structural fitting? (AM.II.A.K4)

Answer 5

The alloy, the metal thickness, and its hardness.

Question 6

6. What is meant by the neutral axis in a sheet of metal? (AM.II.A.K4)

Answer 6

A plane WITHIN THE METAL that neither stretches nor shrinks when the metal is being bent.

Question 7

7. What is a mold line in the development of a flat pattern for a formed metal part? (AM.II.A.K4)

Answer 7

An extension of the flat sides beyond the radius.

*imaginary line at which the outside surface of a bent part would intersect if the bend radius were zero

Question 8

8. What is the bend tangent line? (AM.II.A.K4)

Answer 8

A line in a flat pattern layout at which the bend starts.

*point where the straight portion of a part meets the curved portion of a bend

Question 9

9. What is meant by setback? (AM.II.A.K4)

Answer 9

The distance the JAWS of a brake MUST BE SET BACK from the mold line to FORM A BEND.

Distance the brake must be positioned back from the mold line to allow the bend radius.
*distance between mold line and bend tangent line

**SB = T + R

Question 10

10. What is meant by bend allowance? (AM.II.A.K4)

Answer 10

The actual amount of metal in a bend. It is the distance between the bend tangent lines in a flat pattern layout.

BA = 2pi(R + .5T) / 4

Question 11

11. What is a sight line? (AM.II.A.K4)

Answer 11

A line drawn on a flat pattern layout within the bend allowance that is one bend radius from the bend tangent line. When the sight line is directly below the nose of the radius bar on the brake, the bend will start at the bend tangent line.

*also called bend line - 1 radius. Where you put the nose of the shoe

Question 12

12. What is the main function of throatless shears in an aircraft sheet metal shop? (AM.II.A.K4)

Answer 12

Throatless shears are used to cut mild carbon steel up to 10-gauge, and stainless steel up to 12-gauge. They can be used to cut IRREGULAR curves in the metal.

Question 13

13. What kind of metal forming is done by a slip roll former? (AM.II.A.K4)

Answer 13

Simple curves with a large radius.

Question 14

14. What kind of metal forming is done by bumping? (AM.II.A.K4)

Answer 14

Compound curves in sheet metal.

Question 15

15. When forming a curved angle, what must be done to the flanges? (AM.II.A.K4)

Answer 15

The flanges must be stretched for a convex curve and shrunk for a concave curve.

Shrinker-Stretcher

Question 16

16. When hand-forming a piece of sheet metal that has a concave curve, should the forming be started in the center of the curve, or at its edges? (AM.II.A.K4)

Answer 16

Start at the edges and work toward the center.

Question 17

17. What is meant by a joggle in a piece of sheet metal? (AM.II.A.K4)

Answer 17

A joggle is a small offset near the edge of a piece of sheet metal that allows the sheet to overlap another piece of metal.

Question 18

18. What type of device is a Cleco fastener? (AM.II.A.K5)

Answer 18

A patented fastener that is inserted in the rivet holes and used to hold two pieces of sheet metal together until they can be riveted.

Question 19

19. What type of rivet may be used to replace a round head rivet in an aircraft structure? (AM.II.A.K5)

Answer 19

A universal head rivet.

Question 20

20. How long should a rivet be to join two pieces of sheet metal? (AM.II.A.K5)

Answer 20

The combined thickness of the metal sheets plus 1-1/2 times the rivet shank diameter.

Question 21

21. How can rivets be physically identified for part number and type of material? (AM.II.A.K5)

Answer 21

The identifying mark on the head of an aluminum alloy rivet indicates the specific alloy used in the manufacture of the rivet.

Question 22

22. What type of metal should be hot-dimpled? (AM.II.A.K6)

Answer 22

7075-T6, 2024-T81 aluminum alloys, and magnesium alloys should be hot-dimpled.

Question 23

23. What is the minimum edge distance allowed when installing rivets in a piece of aircraft sheet metal structure? (AM.II.A.K7)

Answer 23

Two times the diameter of the rivet shank.

Question 24

24. What is the recommended transverse pitch to use when making a riveted two row splice in a piece of sheet metal? (AM.II.A.K7)

Answer 24

Three-fourths of the distance between the rivets in the rows.

Question 25

25. Which stringer attached to a wing skin would require the greatest number of rivets for a splice? (AM.II.A.K7)

Answer 25

A stringer in the lower surface.

Question 26

26. Why should aluminum alloy rivets be driven with as few blows as is practical? (AM.II.A.K8)

Answer 26

Excessive hammering will work-harden the rivets and make them difficult to drive.

Question 27

27. What determines whether a piece of sheet metal should be dimpled or countersunk when installing flush rivets? (AM.II.A.K8)

Answer 27

The thickness of the sheet. Countersinking should be done only when the thickness of the sheet is greater than the thickness of the rivet head.

Question 28

28. What should be done to protect a riveted joint between aluminum alloy and magnesium alloy from corrosion? (AM.II.A.K8)

Answer 28

Coat the faying surface with a corrosion-inhibiting primer, dip the rivets in the primer, and drive them while the primer is wet.

Question 29

29. What is the purpose of the beehive spring on a rivet gun? (AM.II.A.K8)

Answer 29

It holds the rivet set in the gun and allows the gun to vibrate on the set.

Question 30

30. What must be done to an aircraft fuel tank before it can be repaired by welding? (AM.II.A.K9)

Answer 30

The gasoline fumes must all be purged from the tank by running live steam through it for at least 30 minutes, by soaking it in hot water, or by filling it with nitrogen or carbon dioxide.

Question 31

31. When drilling out rivets on an airplane or drilling holes for a repair, what precaution should be taken? (AM.II.A.K9)

Answer 31

Do not allow the drill to enter into the space behind the structure, as the drill may cause damage to other structures or systems.

Question 32

32. What are the two fuel gases most generally used for gas welding? (AM.II.A.K10)

Answer 32

Oxygen and acetylene.

Question 33

33. What fuel gases are used for welding aluminum? (AM.II.A.K10)

Answer 33

Oxygen and hydrogen.

Question 34

34. Why is it important that the pressure of the gas in an acetylene cylinder be kept low? (AM.II.A.K11)

Answer 34

Acetylene gas becomes unstable when it is kept under pressure of more than about 15 psi.

Question 35

35. What are two types of torches used in gas welding? (AM.II.A.K12)

Answer 35

Balanced-pressure torches and injector torches.

Question 36

36. What determines the amount of heat that is put into a weld by an oxy-acetylene torch? (AM.II.A.K12)

Answer 36

The size of the orifice in the torch tip.

Question 37

37. What is the difference in the appearance of an oxidizing flame, a neutral flame, and a reducing flame produced by an oxy-acetylene torch? (AM.II.A.K12)

Answer 37

An oxidizing flame has a pointed inner cone, and the torch makes a hissing noise. A neutral flame has a rounded inner cone, and there is no feather around the inner cone. A reducing flame has a definite feather around the inner cone.

Question 38

38. What is one method of minimizing distortion when making a long butt weld? (AM.II.A.K12)

Answer 38

Skip welding minimizes distortion. Tack weld the materials together and then complete the welds between the tacks, starting at a tack and working back toward the finished weld.

Question 39

39. What is meant by tack welding? (AM.II.A.K12)

Answer 39

Tack welding is the use of small welded spots to hold the material together until the final bead is run.

Question 40

40. Why must thick plates of metal be preheated before they are welded? (AM.II.A.K12)

Answer 40

Preheating is a method of controlling the expansion and contraction of the metal being welded. Preheating minimizes the stresses that are caused when welding thick metal.

Question 41

41. What must be done to an aircraft structure after it has been welded while clamped in a heavy jig or fixture? (AM.II.A.K12)

Answer 41

It must be normalized by heating it to a uniform red heat and allowed to cool slowly in still air. Relieve internal stress from expansion and contraction

Question 42

42. Why is it important that all traces of the welding flux be removed after a piece of aluminum or magnesium is welded? (AM.II.A.K12)

Answer 42

Welding flux is corrosive and it must be removed to keep the metal from corroding.

Question 43

43. What is the difference between brazing and welding? (AM.II.A.K12)

Answer 43

In brazing, the base metal is not melted, but is covered with a low-melting-point alloy. In welding, the base metal is melted.

Question 44

44. What kind of flame should be used when gas welding aluminum? (AM.II.A.K12)

Answer 44

A soft, neutral oxy-hydrogen flame.

Question 45

45. What is an acceptable acetylene line pressure to use when welding with an oxy-acetylene rig? (AM.II.A.K12)

Answer 45

About 5 psi.

Question 46

46. What kind of flame should be used when gas welding stainless steel? (AM.II.A.K12)

Answer 46

A slightly carburizing flame.

Question 47

47. How much should the bead penetrate the material when welding two pieces of steel with a butt weld? (AM.II.A.K12)

Answer 47

The joint should have 100% penetration.

Question 48

48. What is meant by a soft flame? (AM.II.A.K12)

Answer 48

A soft flame is one that is made when the pressures of the gases are low enough that the flame does not make a noise and does not blow the puddle.

Question 49

49. What color lenses are used for gas welding steel? (AM.II.A.K12)

Answer 49

Green or brown.

Question 50

50. What color lenses are used for gas welding aluminum? (AM.II.A.K12)

Answer 50

Blue.

Question 51

51. What is another name for GTA welding? (AM.II.A.K13)

Answer 51

TIG welding. Gas Tungsten Arc Tungsten Inert Gas

Question 52

52. What is used as the electrode in GTA welding? (AM.II.A.K13)

Answer 52

A small-diameter tungsten wire.

Question 53

53. What are three types of power that can be used for GTA welding? (AM.II.A.K13)

Answer 53

DC - straight polarity - deep penetration DC - reverse polarity - shallow penetration but clean oxide AC - both

Question 54

54. Which type of power provides the greatest heat and deepest penetration in GTA welding? (AM.II.A.K13)

Answer 54

DC-straight polarity.

Question 55

55. Which type of power is used for GTA welding aluminum and magnesium? (AM.II.A.K13)

Answer 55

DC-reverse polarity.

Question 56

56. What type of shielding gases are used for GTA welding? (AM.II.A.K14)

Answer 56

Helium and argon. Protect molten weld puddle from the air

Question 57

57. What is the function of the inert gas used in GTA and GMA welding? (AM.II.A.K14)

Answer 57

The inert gas forms a shield to keep oxygen away from the weld puddle so oxides cannot form and weaken the weld.

Question 58

58. Why is GTA welding preferred over oxy-acetylene welding for building and repairing welded steel tube aircraft structure? (AM.II.A.K15)

Answer 58

The heat is concentrated in the weld and does not cause as much distortion as gas welding.

Question 59

59. What type of repair can be used when a steel structural tube is dented to more than 1/4 of its circumference? (AM.II.A.K15)

Answer 59

A patch may be welded over the damage.

Question 60

60. What type of repair can be used when a steel structural tube is dented at a cluster? (AM.II.A.K15)

Answer 60

A patch may be welded over the damaged area with fingers extending up along each member of the cluster.

Question 61

61. What is the preferred method of splicing a new piece of tubing into a structure? (AM.II.A.K16)

Answer 61

An inner sleeve splice.

Question 62

62. How is the inner sleeve tube held in the structural tube until the gap is welded? (AM.II.A.K16)

Answer 62

It is held in place with rosette welds.

Question 63

63. What is one limitation of using an outer-sleeve splice in an aircraft structure? (AM.II.A.K16)

Answer 63

This type of splice is not suitable where it would cause a bulge in the fabric.

Question 64

64. How should the ends of an outer-sleeve be cut? (AM.II.A.K16)

Answer 64

Cut it with a 30° fishmouth.

Question 65

65. Should a riveted joint fail in shear or in bearing? (AM.II.A.K17)

Answer 65

It should fail in shear. The rivets should shear before the sheet tears at the rivet holes.