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Airframe > Jeppesen Oral- Chapter 2 ( Sheet Metal Structures) > Flashcards

Jeppesen Oral- Chapter 2 ( Sheet Metal Structures) Flashcards

1
Q

What is the major type of damage to aluminum structures that is caused by exposure to weather?

A

Corrosion

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2
Q

Name several methods for forming sheet metal?

A

Bending, folding, stretching, shrinking, bumping, crimping

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3
Q

What are the dimensions of a properly formed rivet?

A

Head should be 1.5x the shank diameter (width)

Head should be .5x shank diameter in height

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4
Q

What happens to the stem of a self-plugging (friction lock), rivet, when the rivet is installed?

A

The stem is pulled until it snaps off and the remaining projecting part is trimmed flush with the head

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5
Q

Name at leas three types of self-plugging mechanical rivets.

A

Cherry Maxx, CherryLock, Olympic-Locs, Huck

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6
Q

What is the difference between the ticks required to pull a Cherrylock rivet and a cherrymax rivet?

A

CherryMax only requires one tool for all sizes

Cherrylock, requires different tools for different sizes and heads

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7
Q

Which of the 5 stresses is the most common cause of rivet failure?

A

Shear

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8
Q

If a 20 24 rivet must be replaces with a 21 17 rivet, how do you determine the size to be used?

A

For a 5/32” diameter or smaller, use the next larger size 2117 rivet (assuming the edge distance and pitch requirements are met)

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9
Q

Describe the process for determing the total length of a solid rivet for a particular installation.

A

Add the grip length (thickness of the material being joined together) plus 1.5x diamter

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10
Q

What is the minimum edge distance and spacing that should be used for a single row of protruding head rivets?

A

Not less than two rivet diameters from the edge

Not less than three diameters apart

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11
Q

How can a mechanic determine whether the countersunk for a flush rivet should be dimpled or drilled?

A

By the thickness of the top sheet

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12
Q

What action is taken to prevent cracks from forming while dimpling magnesium or some hard sheet metals?

A

Hot dimpling to preheat and soften metal

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13
Q

What type of damage can occur when using a rivet set that does not properly fit the rivet?

A

If the radius is too small, the rivet might become damaged

If the set radius is too large it may damage the sheet metal

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14
Q

Why is it important to use the proper size and weight bucking bar when riveting sheet metal?

A

Bucking bar too big, difficult to control and cause damage

Too light, will not properly upset the rivet prior to work hardening

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15
Q

What procedures should be followed to properly remove a solid shank rivet?

A

Center punch the rivet and then drill a hole to the base of the rivet head with the same size or one smaller

Use a pin punch to tip off the head and drive out the rest of the shank

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16
Q

What are the two special calculations that must be made when bending sheet metal?

A

Bend allowance and setback

17
Q

What are the factors that must be considered in order to determine setback?

A

Thickness of the material and bend radius

18
Q

What is done to a corner where two bends intersect to prevent cracking?

A

Relief holes are drilled into the corner

19
Q

What are the two reasons for installing a lighting hole n sheet metal wing ribs?

A

Reduces weight, increase stiffness

20
Q

Describe a joggle and explain it’s function

A

Offset formed at an intersection of two or more sheet

Allows multiple sheets of metal to be stacked flat against each other

21
Q

When preparing an all-metal aircraft, how do you determine what metals should be used?

A

Use the same metal and thickness

22
Q

What are three requirements for a repair to a piece of sheet metal aircraft structure?

A

The repair must restore the lost strength and rigidity, and it must not change the aerodynamic shape of the part.

23
Q

When making a riveted repair to an aircraft sheet metal structure, which should be stronger, the shear strength of the rivet, or the nearing strength of the metal sheet?

A

The two strengths should be close to each other, but the bearing strength should be greater.

24
Q

What type of device is a Cleco fastener?

A

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

25
Q

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

A

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

26
Q

What is the purpose of a sight line when laying out sheet metal to be bent in a cornice brake?

A

The sight line allows the jaws of a cornice brake to be positioned so the bend made by the brake will start at the bend tangent line.

27
Q

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

A

Simple curves with a large radius

28
Q

What kind of metal forming is done by bumping?

A

Compound curves in sheet metal

29
Q

What must be done to the flanges of an angle for it to be curved?

A

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

30
Q

What is meant by the bend allowance used in making a bend in a piece of sheet metal?

A

The bend allowance is the amount of metal that is actually used in making the bend in a piece of sheet metal.

31
Q

What determines the minimum bend radius that can be used with a piece of sheet metal?

A

The thickness of the material and its hardness

32
Q

What is meant by setback when bending a piece of sheet metal in a cornice brake?

A

Setback is the distance the jaws bust be set back from the mold line to form the bend.

33
Q

When hand-forming a piece of sheet metal that has a concave curve, should the forming be started in the center or at its edges?

A

Start at the edges and work towards the center.

34
Q

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

A

Excessive hammering will work0harden the rivets and make them difficult to drive.

35
Q

What type of metal should be hot-dimpled?

A

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

36
Q

What special precautions must be taken when repairing a radome?

A

Nothing must be done to the radome that will affect its electrical transparency or its aerodynamic strength

37
Q

How is the point of a twist drill ground that is to be used for drilling transparent acrylic material?

A

The cutting edge should be dubbed off to a zero rake angle, and the included angle of the tip should be ground to 140 degrees.

38
Q

What causes crazing in a piece of transparent sheet metal?

A

Uneven stresses in the material, usually caused by heat.

39
Q

What is the purpose of anodizing a piece of aluminum alloy, and how is it applied?

A

Anodizing is a protective oxide film that is deposited on the surface of aluminum alloy by an electrolytic process.

Airframe (22 decks)

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