Chapter 12 - Cleaning and Corrosion - Oral Questions

Question 1

Is there any requirement for cleaning an aircraft prior to an annual or 100 hour inspection?

Answer 1

It is a legal requirement as specified in FAR Part 43, Appendix D

Question 2

Discuss the general precautions that should be observed when washing an airplane.

Answer 2

Avoid or protect areas which may be damaged or contaminated such as

Pitot and static ports,

hinges,

sealed areas, and

bearings

Question 3

What are some of the more common light duty cleaning agents?

Answer 3

Soap or detergents and water

Question 4

What materials are commonly used as heavy duty cleaners?

Answer 4

Solvents and emulsions

Question 5

What are the preferred cleaners for plastic surfaces such as windshields

Answer 5

Mild soap and water or a manufacturer approved cleaner

Question 6

What type of cleaning agents should be used to remove grease, oil or fuel from aircraft tires?

Answer 6

Soap and Water

Question 7

Give at least three examples of the factors that cause or influence corrosion

Answer 7

1) The environmental conditions
2) The presence of dissimilar metals
3) The type of metal
4) the presence of electrolytes and or contaminants
5) The condition of protective coatings

Question 8

Name at least three forms of corrosion

Answer 8

1) Surface
2) Intergranular
3) Filliform
4) Dissimilar metal (galvanic)
5) Oxidation

6) Pitting
7) Stress

8) Fretting

Question 9

Name at least one cause of filliform corrosion

Answer 9

1) Improper or incomplete curing of a wash primer prior to painting
2) Failure to completely wash off acidic surface contamination

Question 10

What are the visible signs of filliform corrosion?

Answer 10

Blistered paint surfaces, worm or thread-like tracks under the paint

Question 11

What are two primary factors that may cause development of stress corrosion cracks?

Answer 11

A corrosive environment and sustained tensile stress

Question 12

What are the visible signs of fretting corrosion?

Answer 12

Corrosion residue has a dark, smoky appearance and often appears around and streaming back from rivet heads

(smoking guns)

Question 13

Why are piano-type hinges prime spots for corrosion?

Answer 13

The steel pin and aluminum hinge material are dissimilar metals and the hinge design tends to trap moisture and contaminants

Question 14

What is the best way to protect piano hinges from corrosion?

Answer 14

Keep them clean and properly lubricated

Question 15

Provide at least four examples of procedures used to prevent corrosion

Answer 15

1) Cleaning
2) Lubrication
3) Treatment
4) Sealing
5) Inspection
6) Installing protective covers
7) Keeping drain holes free and clear

Question 16

Describe the tools that should be used to remove corrosion from aluminum surfaces

Answer 16

Nylon scrubber pads (scotch brite),

bristle brushes,

aluminum wool or

aluminum wire brushes

Question 17

Describe the effects of using steel brushes or steel wool to remove corrosion from aluminum surfaces

Answer 17

Steel brushes or steel wool must not be used to clean aluminum because steel particles can become embbedded in the aluminum and cause corrosion

Question 18

What is the purpose of alodine?

Answer 18

Alodine is a chemical process that deposits a protective film on aluminum alloys. This film improves corrosion reistance and paint adhesion

Question 19

For what reason should you avoid cleaning anodized aluminum surfaces with aluminum metal polish

Answer 19

The polish removes the protective oxide coating

Question 20

Why should aircraft fabrics and plastics be cleaned only with recommended cleaners?

Answer 20

They cause the least amount of deterioration or damage

Question 21

List at least five areas of an aircraft prone to corrosion

Answer 21

1) Battery compartments
2) Exhaust trail areas
3) Bilge areas
4) Vent areas
5) Landing gear and wheel wells
6) Fuel tanks
7) Wing flap recesses
8) Around and below galleys and lavatories
9) Piano Hinges
10) Any area that can trap water