Aircraft finishes

Question 1

Name the safety and health precautions to be observed in operating a dope room, including storage of material.

Answer 1

The dope room should be well lighted and ventilated using spark proof motors, lights, and switches, All flammable material should be stored in fireproof containers in protected areas. Dope and paint rooms that are not located in a separate building should be isolated from the rest of the building by metal partitions and fireproof doors

Question 2

What primer is used when maximum protection of the metal is desired?

Answer 2

Epoxy.

Question 3

What type of test can be performed to identify existing paint finishes?

Answer 3

Apply a coat of engine oil to a small area. Nitrocellulose will soften in a few minutes, but acrylic and epoxy will show no effects. If not identified, next wipe down a small area with MEK. MEK will pick up pigment from an acrylic finish, but will not affect an epoxy coating.

Question 4

What causes blushing when applying dope or lacquer, and how can it be prevented?

Answer 4

When doping is accomplished under humid conditions, blushing is possible. Rapid evaporation of thinners and solvents lower the temperature of the surface of the wet dope causing condensation of moisture from the air. The moisture causes a milky white or cloudy appearance known as blush.
The condition may be eliminated by heating the room to decrease humidity, or by using a blushretarding thinner to increase the drying time. Blushing is also caused by moisture in the air supply, drafts, or change in temperature.

Question 5

What is the purpose of using fungicidal dope when finishing aircraft fabric?

Answer 5

To prevent micro-biological deterioration (rotting) of the fabric.

Question 6

What are the identification marking requirements for United States registered fixed wing aircraft?

Answer 6

The Roman capitol letter “N” followed by the registration number must be displayed on both sides of the fuselage.

Question 7

What should the color of registration markings be?

Answer 7

The color of markings should contrast their background.

Question 8

What are two types of dope used for aircraft finishes?

Answer 8

They are nitrate and butyrate.

Question 9

What is the advantage of butyrate over nitrate?

Answer 9

Less flammable.

Question 10

What would happen if dope was ever used over paint or enamel?

Answer 10

It would have the tendency to lift and remove such materials.

Question 11

What is applied to metallic surfaces as a common resistant covering before the application of enamel or lacquer?

Answer 11

Zinc chromate primer is normally used for this purpose.

Question 12

What can be done to the surface of components to prevent filiform corrosion?

Answer 12

Ensure that the primer is completely cured.

Question 13

What are the most common methods of applying aircraft finishes?

Answer 13

They are dipping, brushing, or spraying.

Question 14

What type of paint may be used over any paint system that is in good condition?

Answer 14

Epoxy topcoats will adhere to all paint systems that are in good condition and may be used as a general touchup, including touchup of defects in baked enamel coatings.

Question 15

What is normally the cause of runs and sags in a spray application of a paint finish?

Answer 15

Holding the gun too long in one place or holding the gun too close can cause too much paint to be applied in one area.

Question 16

What causes an spray dust?

Answer 16

Incorrect spray gun setting, incorrect air pressure, incorrect paint viscosity, and holding the gun too far from the work.

Question 17

What causes, fisheyes in paint?

Answer 17

Surface contamination.

Question 18

What is used with zinc chromate primer if it is too thick and needs to be thinned?

Answer 18

Toluene.

Question 19

Which federal regulation prescribes the size and location requirements for aircraft identification numbers?

Answer 19

FAR Part 45

Question 20

What type of materials should be thoroughly protected when using paint remover?

Answer 20

Synthetic rubber surfaces, aircraft tires, fabric, and acrylics must be protected against possible contact with paint remover.

Question 21

What instructions should be followed when covering an aircraft with materials specified in an STC?

Answer 21

The instructions are included in the STC.

Question 22

What are the common types of paint used on aircraft?

Answer 22

Primers, enamels, lacquers, and multipart finishing formulas (epoxies).

Question 23

What is the purpose of zinc chromate primer?

Answer 23

It serves as a corrosion resistant covering and base coat for protective topcoats.

Question 24

What is a blushing paint finish?

Answer 24

A dull milky haze that appears in a paint finish.

Question 25

What causes orange peel spray mottle?

Answer 25

Not enough reducer (too thick) or the wrong type reducer for the ambient temp; or material not uniformly mixed; or forced drying method too quick; or too little flash time between coats; or ambient temp is either too hot or too cold.

Question 26

What will cause a blushing paint finish?

Answer 26

It occurs when moisture is trapped in the paint. Usually due to moisture in the air supply, adverse humidity, or changes in temperature.

Question 27

Many of the solvents and thinners used in modern finishing systems are toxic; what health safety precaution should the mechanic observe?

Answer 27

Proper respirators and fresh-air breathing systems must be available to all personnel.

Question 28

What paint system is compatible with epoxy topcoats?

Answer 28

Any paint system in good condition.

Question 29

What areas must be protected from damage when using paint remover/stripper?

Answer 29

All window material, vents and static ports, rubber seals and tires, and composite components that may be affected by the chemicals.