Airframe Structures: Sheet Metal & Non-metallic Structures 🔊

Question 1

What is the grip length of a rivet?

Answer 1

It is the combined thickness of the material to be joined

Question 2

Where are special rivets, such as Huck or Cherry lock rivets located?

Answer 2

They are used in places where access to both sides of the riveted structure is impossible or where limited space will not permit the use of a bucking bar. (also known as blind rivets)

Question 3

What is bonded honeycomb (sandwich) construction?

Answer 3

It is a laminar construction consisting of a combination of alternating dissimilar materials; assembled and fixed in relation to each other so that the properties of each can be used to attain specific structural advantages for the whole assembly while reducing weight.

Question 4

What type of materials are used in honeycomb construction?

Answer 4

Stainless steel, titanium, magnesium, plywood, resin impregnated paper, E-glass, nylon in various combinations

Question 5

Where are sandwich construction assemblies used?

Answer 5

Bulkheads, control surfaces, fuselage panels, wing panels, radomes, empennage skins, or shear webs

Question 6

What procedures should be used to prevent damage to the hole when drilling through Plexiglas?

Answer 6

Plexiglas should be backed with wood and the feed slowed. The drill bit should be modified to a 60° tip angle. The cutting edge to zero-rake angle and the back lip clearance angle increased 12-15°.

Question 7

What calculations must be made when bending sheet metal?

Answer 7

Setback and bend allowance

Question 8

What factors are used to determine setback?

Answer 8

Radius of the bend and thickness of the material. (Setback = radius + thickness)

Question 9

When bending sheet metal, how should the grain be in relation to the bend?

Answer 9

Perpendicular to the bend

Question 10

What is a bend tangent line?

Answer 10

The line at which the metal starts to bend

Question 11

What is a joggle?

Answer 11

An offset near the edge of a piece of sheet metal to allow clearance for a sheet or extrusion

Question 12

What are several methods used in forming sheet metal?

Answer 12

Folding, bumping, crimping, shrinking, and stretching

Question 13

What kind of metal forming is done by bumping?

Answer 13

Compound curves

Question 14

What is crazing and how does it occur?

Answer 14

Hairline cracks in the surface plastic. Uneven heating causing one side to expand more than the other, subjecting plastics to large stresses, and exposure to harmful solvents

Question 15

Briefly describe the anodizing process and what purpose it serves.

Answer 15

Aluminum alloys are placed in an electrolytic bath which causes a thin film of hydroxide to form on the surface. The coating provides excellent resistance to corrosion, but it is also an excellent bond for paint.

Question 16

What are the proper dimensions for the shop head of a rivet?

Answer 16

1.5 times the diameter in width and .5 times the diameter in height after bucking

Question 17

When inspecting Plexiglas, what should you look for?

Answer 17

Crazing and discoloration

Question 18

What causes honeycomb structure to delaminate?

Answer 18

Moisture

Question 19

What are the acceptable repair methods for bonded honeycomb structure that has been damaged?

Answer 19

A potted repair or a laminated glass fabric cloth overlay, if the damage exceeds the repair limitations of the potted compound method.

Question 20

What size drill should be used for the common shank rivet diameters of 3/32 inch, 4/32 inch, and 5/32 inch?

Answer 20

3/32 = number 40; 4/32 = number 30; 5/32 = number 21

Question 21

What is used for hole filling in a bonded honeycomb repair?

Answer 21

Potting compound

Question 22

What is a lightning hole?

Answer 22

They are cut into rib sections, fuselage frames, and other structural parts to decrease weight.

Question 23

What special precautions should be observed when repairing a radome?

Answer 23

Repair must retain its strength and electrical transparency.

Question 24

What is a warp line?

Answer 24

A highlighted strand in the fabric used for ply orientation.

Question 25

What does “pot life” mean?

Answer 25

The length of time a resin will remain workable after the catalyst is added.

Question 26

What is a Barcol hardness test?

Answer 26

A device that pushes a spike into material such as composites. The depth of penetration can be measured to determine if resins in the composite have cured.

Question 27

What is done to honeycomb before repairing?

Answer 27

Remove damaged honeycomb and either replace with potting compound or a honeycomb replacement plug.

Question 28

What is the difference between thermoplastics and thermosetting plastics?

Answer 28

Thermoplastics can be remelted and reformed. Thermosetting cannot.

Question 29

When cutting a piece of sheet metal at the edge, and you bend the corners in, what needs to be done?

Answer 29

You must drill a relief hole.