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General A&P Oral > Metallic Structures > Flashcards

Metallic Structures Flashcards

1
Q

What are key areas to consider when inspecting a metal structure?

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.
-Look for cracks near rivets or stressed areas.
-Inspect for corrosion.

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2
Q

Wat are the types of damage and defects that may be observed on sheet metal aircraft parts?

A

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

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3
Q

What is one of the most important considerations when selecting materials for a sheet metal repair?

A

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

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4
Q

For maximum strength of a formed sheet metal fitting, should the bend be made along or across the grain of the metal.

A

Across the grain.

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5
Q

What determines the minimum, bend radius that can be used when forming a sheet metal structural fitting?

A

the alloy, the metal thickness, and its hardness.

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6
Q

What is meant by the neutral axis in a sheet of metal?

A

A plane withing the metal that neither stretches nor shrinks when the metal is being bent.

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7
Q

What is a mold line in the development of a flat patter for a formed metal part?

A

An extension of the flat sides beyond the radius.

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8
Q

What is the bend tangent line?

A

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

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9
Q

What is meant by setback?

A

The distance the jaws of a brake must be set back from the mold line to form a bend.

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10
Q

What is meant by bend allowance?

A

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

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11
Q

What is a sight line?

A

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

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12
Q

What is the main function of throatless shears in an aircraft sheet metal shop?

A

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

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13
Q

What kind of metal forming is done by a slip roll former?

A

Simple curves with a large radius.

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14
Q

What kind of metal forming is done by bumping?

A

Compound curves in sheet metal.

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15
Q

When forming a curved angle, what must be done to the flanges?

A

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

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16
Q

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 as its edges?

A

Start at the edges and work toward the center.

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17
Q

What is meant by a joggle in a piece of sheet metal?

A

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.

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18
Q

What type of device is a Cleco fastener?

A

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.

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19
Q

What type of rivet may be used to replace a round head rivet in an aircraft structure?

A

A universal head rivet.

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20
Q

How long should a rivet be to joint two pieces of sheet metal?

A

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

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21
Q

How can rivets be physically identified for part number and type of material?

A

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

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22
Q

What type of metal should be hot-dimpled?

A

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

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23
Q

What is the minimum edge distance allowed when installing rivets in a piece of aircraft sheet metal structure?

A

Two times the diameter of the rivet shank.

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24
Q

What is the recommended traverse pitch to use when making a riveted two row splice in piece of sheet metal?

A

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

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25
Q

Which stringer attached to a wing skin would require the greatest number of rivets for a splice?

A

A stringer in the lower surface.

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26
Q

Why should aluminum alloy rivets be driven with as few blows as is practical?

A

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

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27
Q

What determines whether a piece of sheet metal should be dimpled or countersunk when installing flush rivets?

A

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.

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28
Q

What should be done to protect a riveted joint between aluminum alloy and magnesium alloy from corrosion?

A

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

29
Q

What is the purpose of the beehive spring on a rivet gun?

A

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

30
Q

What must be done to an aircraft fuel tank before it can be repaired by welding?

A

The gas 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.

31
Q

When drilling out rivets on an airplane or drilling holes for a repair, what precaution should be taken?

A

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

32
Q

What are the two fuel gasses most generally used for gas welding?

A

Oxygen and acetylene.

33
Q

What fuel gases are used for welding aluminum?

A

Oxygen and hydrogen.

34
Q

Why ii it important that the pressure of the gas in an acetylene cylinder be kept low?

A

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

35
Q

What are two types of torches used in gas welding?

A

Balanced-pressure torches and injector torches.

36
Q

What determines the amount of heat that is put into a weld by an oxy-acetylene torch?

A

The size of the orifice in the torch tip.

37
Q

What is the difference in the appearance of an oxidizing flame, a neutral flame, and a reducing flame produced by an oxy-acetylene torch?

A

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.

38
Q

What is one method of minimizing distortion when making a long butt weld?

A

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.

39
Q

What is meant by tack welding?

A

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

40
Q

Why must thick plates of metal be preheated before they are welded?

A

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.

41
Q

What must be done to an aircraft structure after it has been welded while clamped in a heavy jig or fixture?

A

It must be normalized by heating it to a uniform red heat and allowed to cool slowly in still air.

42
Q

Why is it important that all traces of the welding flux be removed after a piece of aluminum or magnesium is welded?

A

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

43
Q

What is the difference between brazing and welding?

A

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

44
Q

What kind of flame should be used when gas welding aluminum?

A

A soft, neutral oxy-hydrogen flame.

45
Q

What is acceptable acetylene line pressure to use when welding with an oxy-acetylene rig?

A

About 5 psi.

46
Q

What kind of flame should be used when gas welding stainless steel?

A

A slightly carburizing flame.

47
Q

How much should the bead penetrate the material when welding two pieces of steel with a butt weld?

A

The joint should have 100% penetration.

48
Q

What is meant by a soft flame?

A

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.

49
Q

What color lenses are used for gas welding steel?

A

Green or brown.

50
Q

What color lenses are used for gas welding aluminum?

A

Blue.

51
Q

What is another name for GTA welding?

A

TIG welding.

52
Q

What is used as the electrode in GTA welding?

A

A small-diameter tungsten wire.

53
Q

What are three types of power than can be used for GTA welding?

A

DC-straight polarity, DC-reverse polarity, and AC.

54
Q

Which type of power provides the greatest heat and deepest penetration in GTA welding?

A

DC-straight polarity.

55
Q

Which type of power is used for GTA welding aluminum and magnesium?

A

DC-reverse polarity.

56
Q

What type of shielding gases are used for GTA welding?

A

Helium and argon.

57
Q

What is the function of the inert gas used in GTA and GMA welding?

A

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

58
Q

Why is GTA welding preferred over oxy-acetylene welding for building and repairing welded steel tube aircraft structure?

A

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

59
Q

What type of repair can be used when a steel structural tube is dented to more than 1/4 of its circumference?

A

A patch may be welded over the damage.

60
Q

What type of repair can be used when a steel structural tube is dented at a cluster?

A

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

61
Q

What is the preferred method of splicing a new piece of tubing into a structure?

A

An inner sleeve splice.

62
Q

How is the inner sleeve tube held in the structural tube until the gap is welded?

A

It is held in place with rosette welds.

63
Q

What is one limitation of using an outer-sleeve splice in an aircraft structure?

A

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

64
Q

How should the ends of an outer-sleeve be cut?

A

Cut it with a 30° fishmouth.

65
Q

Should a riveted joint fail in shear or in bearing?

A

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

66
Q

Explain the risks associated with choosing the incorrect materials for a repair.

A

The repair material should be the same strength as the original material. Material that is too weak will cause the repair to be weaker than the original. Material that is stronger than the original will cause stresses to move to other structure, increasing the risk of failure to the surrounding structure. Choosing a dissimilar metal for the repair increases the chance of corrosion.

67
Q

What are some precautions and safety practices that should be used when working with sheet metal repairs?

A

-Use caution when working around equipment such as metal shears and breaks which can cause personal injury.
-Freshly cut sheet metal has harp edges than can cause personal damage or scratches and gouges on adjoining structure.
-When drilling out rivets or rivet holes, metal shavings will be present. Use extra caution when drilling overhead.
-Use caution with drill. Never place fingers or hands behind the area being drilled and be careful to not damage surrounding structure or systems when the drill bit passes through.

68
Q

What PPE should be used when making a sheet metal repair?

A

Use eye protection at all times. Use gloves when working with sharp edges or drills. Use ear protection when working in closed areas, especially when driving rivets.

69
Q

What precautions should be taken when using electric welding equipment?

A

Electric welding requires the completion of a circuit. It is important that this circuit is kept complete, and the materials being welded must be well grounded as well as the surface area or bench where the welding is taking place. Poor electrical grounds can cause electric shock to the individual doing the welding.

General A&P Oral (28 decks)

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