AVGM Test Prep Flashcards
1
Q
Which coupling nut should be selected for use with 1/2-inch aluminum oil lines which are to be assembled using flared tube ends and standard AN nuts, sleeves, and fittings?
A
AN-818-
Expl- An AN-818-5 nut will fit a 5/16-inch tube. (The last dash number is the tube diameter in 1/16-inch increments.) An AN-818-16 nut will fit a 1-inch tube. An AN-818-8 nut will fit a 1/2-inch tube.
2
Q
Metal tubing fluid lines are sized by wall thickness and
A
outside diameter in 1/16 inch increments
Expl- Metal tubing used in aircraft fluid power installations is sized by its outside diameter, which is measured fractionally in sixteenths of an inch
3
Q
Rolling-type Flaring Tools are used to flare X, X, and X tubing
A
Soft copper, aluminum, brass.
Expl- Use rolling-type flaring tools only to flare soft copper, aluminum, and brass tubing. Do not use with corrosion resistant steel or titanium
4
Q
From the following sequences of steps, indicate the proper order you would use to make a single flare on a piece of tubing:
- Place the tube in the proper size hole in the flaring block.
- Project the end of the tube slightly from the top of the flaring tool, about the thickness of a dime.
- Slip the fitting nut and sleeve on the tube.
- Strike the plunger several light blows with a lightweight hammer or mallet and turn the plunger one-half turn after each blow.
- Tighten the clamp bar securely to prevent slippage.
- Center the plunger or flaring pin over the tube.
A
3, 1, 6, 2, 5, 4.
Expl- The correct sequence for making a single flare on a piece of tubing is:
(3) Slip the fitting nut and sleeve on the tube.
(1) Place the tube in the proper size hole in the flaring block.
(6) Center the plunger or flaring pin over the tube.
(2) Project the end of the tube slightly from the tip of the flaring tool, about the thickness of a dime.
(5) Tighten the clamp bar securely to prevent slippage.
(4) Strike the plunger several light blows with a lightweight hammer or mallet. Turn the plunger one-half turn after each blow.
5
Q
Hydraulic tubing, which is damaged in a localized area to such an extent that repair is necessary, may be repaired
A
by cutting out the damaged area and utilizing a swaged tube fitting to join the tube ends.
Expl- If a piece of high-pressure hydraulic tubing is damaged in a localized area, the damage can be cut out and a new piece of tubing cut to replace the damaged section. Swage- type splice fittings are slipped over each end of the tubing, and the fittings are swaged to the tube ends.
6
Q
What is an advantage of a double flare on aluminum tubing?
A
More resistant to damage when the joint is tightened.
Expl- Tubing made of 5052-O and 6061-T aluminum alloy in sizes from 1/8- to 3/8-inch OD should be flared with a double flare. Double flares are smoother than single flares and are more concentric. Also, the extra metal makes the flare more resistant to the shearing effect when the fittings are torqued.
7
Q
A certain amount of slack must be left in a flexible hose during installation because, when under pressure, it
A
contracts in length and expands in diameter.
Expl- When flexible hose is installed in an aircraft, it must be given a certain amount of slack because when pressure is applied to the hose, it contracts in length and expands in diameter.
8
Q
The term ‘cold flow’ is generally associated with
A
impressions left in natural or synthetic rubber hose material.
Expl- The term ‘cold flow’ describes the deep, permanent impression left in a natural or synthetic rubber hose by the pressure of hose clamps or supports.
9
Q
What is the color of an AN steel flared-tube fitting?
A
Black.
Expl- Steel AN flared tube fittings are colored black. Aluminum alloy AN fittings are colored blue.
10
Q
Which of the following statements is/are correct in reference to flare fittings?
- AN fittings have an identifying shoulder between the end of the threads and the flare cone.
- AC and AN fittings are considered identical except for material composition and identifying colors.
- AN fittings are generally interchangeable with AC fittings of compatible material composition.
A
1.
Expl- AN flare fittings have a shoulder between the end of the threads and the flare cone. In AC fittings the threads go all the way to the cone. AN fittings are dyed blue or black and AC fittings are gray or yellow. The threads on an AN fitting are courser than those on an AC fitting. AN and AC fittings are not interchangeable.
11
Q
Flexible lines must be installed with
A
a slack of 5 to 8 percent of the length.
Expl- When flexible lines are installed in a fluid power system, they should be between 5 percent and 8 percent longer than the space between the fittings. This extra length (this slack) makes allowance for expansion in the system due to heat and for the fact that a hose contracts in its length when it is pressurized.
12
Q
The maximum distance between end fittings to which a straight hose assembly is to be
A
52 1/2 inches.
Expl- When a flexible line is installed in a fluid power system, it should be between 5 percent and 8 percent longer than the space between the fittings. If the distance between the fittings is 50 inches, the hose should be at least 5 percent longer than this, or 52- 1/2 inches long.
13
Q
Excessive stress on fluid or pneumatic metal tubing caused by expansion and contraction due to temperature changes can best be avoided by
A
providing bends in the tubing.
Expl- Never select a path for a rigid fluid line that does not require bends in the tubing. Bends are necessary to permit the tubing to expand and contract under temperature changes and to absorb vibration.
14
Q
The material specifications for a certain aircraft require that a replacement oil line be fabricated from 3/4-inch 0.072 5052-0 aluminum alloy tubing. What is the inside dimension of this tubing?
A
0.606 inch.
Expl- Find the inside diameter of a tube by subtracting two times the wall thickness from its outside diameter.
0.750 - 2(0.072) = 0.606 inch
The inside diameter is 0.606 inch.
15
Q
In most aircraft hydraulic systems, two-piece tube connectors consisting of a sleeve and a nut are used when a tubing flare is required. The use of this type connector eliminates
A
the possibility of reducing the flare thickness by wiping or ironing during the tightening process.
Expl- There are two types of flare fittings that can be used in aircraft hydraulic systems. One type is the single-piece AN817 nut, and the other is the two-piece MS20819 sleeve and an AN818 nut. The AN818 nut and sleeve are preferred over the single-piece fitting because it eliminates the possibility of reducing the thickness of the flare by the wiping or ironing action when the nut is tightened. With the two-piece fitting, there is no relative motion between the fitting and the flare when the nut is being tightened.
16
Q
Which statement(s) about Military Standard (MS) flareless fittings is/are correct?
1. During installation, MS flareless fittings are normally tightened by turning the
nut a specified amount, rather than being torqued.
2. New MS flareless tubing/fittings should be assembled clean and dry without lubrication.
3. During installation, MS flareless fittings are normally tightened by applying a specified torque to the nut
A
1.
Expl- MS flareless fittings are attached to the end of a metal tube by presetting the fitting on the tube.
Presetting consists of putting enough pressure on the fitting to deform the ferrule and cause it to cut into the outside of the tube. Presetting is done by lubricating the threads of the presetting tool and the nut with hydraulic fluid, assembling the nut and ferrule on the tube, putting it in the presetting tool, and tightening the nut by hand until resistance is felt, then turning it with a wrench from 1 to 1-1/4 turns.
When installing the fitting in an aircraft hydraulic system, tighten the nut by hand until resistance is felt, then turn it 1/6 to1/3 of a turn (one hex to two hexes) with a wrench
17
Q
When flaring aluminum tubing for use with AN fittings, the flare angle must be
A
37°.
Expl- The flare angle used with AN fittings is 37°.
18
Q
Scratches or nicks on the straight portion of aluminum alloy tubing may be repaired if they are no deeper than
A
10 percent of the wall thickness.
Expl- Scratches or nicks are allowed in a piece of aluminum alloy tubing provided it is no deeper than 10 percent of the wall thickness of the tube, and it is not in the heel of a bend. Scratches and nicks should be burnished out of the tube, to prevent stress concentrations.
19
Q
Flexible hose used in aircraft systems is classified in size according to the
A
inside diameter.
Expl- The size of flexible hose is determined by its inside diameter. Sizes are in 1/16- inch increments and relate to corresponding sizes of rigid tubing with which it can be used.
20
Q
When a Teflon hose has been in service for a time, what condition may have occurred and/or what precaution should be taken when it is temporarily removed from the aircraft?
A
The hose may have developed a set, or have been manufactured with a pre-set shape, and must be supported to maintain its shape.
Expl- Teflon hoses develops a permanent set after having been in use for an extended period of time or may have been manufactured with a permanent set for the particular function, thus is should be supported to maintain its shape and prevent inadvertent straightening.
21
Q
A scratch or nick in aluminum tubing can be repaired provided it does not
A
appear in the heel of a bend.
Expl- Scratches or nicks not deeper than 10 percent of the wall thickness in aluminum alloy tubing, that are not in the heel of a bend, may be repaired by burnishing (forcing the displaced metal back into the nick or scratch) with a polished steel burnishing hand tool.
22
Q
Which of the following hose materials are compatible with phosphate-ester base hydraulic fluids?
A
1 and 2.
Expl- Butyl is not suitable for use with petroleum products, but is an excellent inner liner for phosphate-ester base hydraulic fluids. Teflon hose is unaffected by any fuel, petroleum, or synthetic-base oils, alcohol, coolants, or solvents commonly used in aircraft. Buna-N should not be used with phosphate-ester base hydraulic fluids. Neoprene is not suitable for use with phosphate-ester base hydraulic fluids.
23
Q
Which tubing have the characteristics (high strength, abrasion resistance) necessary for use in a high-pressure (3,000 PSI) hydraulic system for operation of landing gear and flaps?
A
Corrosion-resistant steel annealed or 1/4H.
Expl- Rigid tubing made of corrosion-resistant steel, either annealed or 1/4 hard, is used in high-pressure hydraulic or pneumatic systems where high strength and abrasion resistance are important.
24
Q
When installing bonded clamps to support metal tubing
A
remove paint or anodizing from tube at clamp location.
Expl- When a piece of metal tubing is installed in a bonded clamp, any paint or anodizing oxide film must be removed from the portion of the tube where the clamp is to fit. Both paint and the oxide film are electrical insulators.
25
In a metal tubing installation
tension is undesirable because pressurization will cause it to expand and shift.
Expl- When making an installation of rigid metal tubing, each run of the tubing must have at least one bend in it to allow for the shifting of the line as it is pressurized. There must be no tension on the line (the flare in both ends of the tube should rest squarely on the flare cones of the fittings and not have to be pulled into place with the nut).
26
The best tool to use when cutting aluminum tubing, or any tubing of moderately soft metal is a
hand operated wheel-type tubing cutter.
Expl- A hand operated wheel-type tubing cutter is the best tool to use when cutting aluminum tubing, or any tubing of moderately soft metal.
27
The primary purpose of providing suitable bends in fluid and pneumatic metal tubing runs is to
prevent excessive stress on the tubing.
Expl- When making an installation of rigid metal tubing, each run of the tubing must have at least one bend in it to allow for the shifting of the line as it is pressurized. This prevents excessive stress on the tubing.
28
Which of the following statements is true regarding minimum allowable bend radii for
1.5 inches OD or less aluminum alloy and steel tubing of the same size?
The minimum radius for steel is greater than for aluminum.
Expl- The minimum allowable bend radius for a 1.5 inch OD aluminum tubing is 5 inches. The minimum allowable bend radius for the same diameter steel tubing is 5.25 inches. Steel tubing in sizes smaller than 1.5 inch OD require a greater minimum bend radius than aluminum alloy tubing of the same size.
29
A gas or fluid line marked with the letters PHDAN is
used to carry a hazardous substance.
Expl- The marking PHDAN on a fluid line indicates that the fluid carried in the line is physically hazardous and dangerous to personnel.
30
Which statement is true regarding the variety of symbols utilized on the identifying color-code bands that are currently used on aircraft plumbing lines?
Symbols are always black against a white background regardless of line content.
Expl- The fluid carried in fluid lines in an aircraft is identified by a series of color- coded bands around the line. These bands have from one to three contrasting colors. There is also a white band with black geometric symbols for the benefit of color-blind personnel.
31
If a flared tube coupling nut is overtightened, where is the tube most likely to be weakened/damaged?
At the sleeve and flare junction.
Expl- Overtightening a flared tube coupling nut will likely weaken or damage the tube and it is most likely to fail at the sleeve and flare junction.
32
Which statement concerning Bernoulli's principle is true?
The pressure of a fluid decreases at points where the velocity of the fluid increases.
Expl- Bernoulli's principle is one of the most useful principles we have to explain the behavior of fluid (either liquid or gas) in motion. Bernoulli's principle tells us that if we neither add energy nor take any energy from fluid in motion, an increase in the velocity of the fluid (its kinetic energy) will result in a corresponding decrease in its pressure (its potential energy).
33
(1) Bonded clamps are used for support when installing metal tubing.
(2) Unbonded clamps are used for support when installing wiring. Regarding the above statements, -
both No. 1 and No. 2 are true.
Expl- Statement (1) is true. Bonded clamps (clamps in which the tube is contacted with a piece of bare metal) are used when installing metal tubing in an aircraft. Bonded clamps keep the tube at the same electrical potential as the aircraft structure. Statement (2) is also true. Unbonded (cushion) clamps are used when securing wire bundles to the aircraft structure. The soft cushion in the clamp prevents abrasion wearing away the insulation on the wire.
34
Which statement is true regarding flattening of tubing in bends?
Flattening by not more than 25 percent of the original diameter is permissible.
Expl- Tubing in the bend is often deformed, and the bend is not satisfactory if its small diameter is less than 75% of the outside diameter of the straight tubing. This allows a flattening in the bend of not more than 25% of the original OD of the tube.
35
A 3/8 inch aircraft high pressure flexible hose as compared to 3/8 inch metal tubing used in the same system will
have equivalent flow characteristics.
Expl- Flexible hose may be used in any part of an aircraft fluid system where it has been proven by the aircraft manufacturer to be suitable. The hose must be able to carry the pressure, withstand the vibration, and pass the required fluid flow. The size of a flexible hose is approximately its inside diameter in 1/16-inch increments. This refers to the outside diameter of a rigid tube that has the equivalent flow characteristics.
36
Magnetic particle inspection is used primarily to detect
flaws on or near the surface.
Expl- Magnetic particle inspection is used to detect flaws in ferromagnetic material on or near the surface. These flaws form north and south magnetic poles when the part is magnetized. Iron oxide suspended in a fluid pumped over the part is attracted to and held by the magnetism and it outlines the flaw.
37
Liquid penetrant inspection methods may be used on which of the following?
1. porous plastics.
2. ferrous metals.
3. nonferrous metals.
4. smooth primer-sealed wood.
5. nonporous plastics.
2, 3, 5.
Expl- Liquid penetrant inspection methods may be used to detect faults that extend to the surface on both ferrous and nonferrous metals and nonporous plastics.
38
Which of these nondestructive testing methods is suitable for the inspection of most metals, plastics, and ceramics for surface and subsurface defects?
Ultrasonic inspection.
Expl- Ultrasonic inspection uses high-frequency sound waves to detect faults in a material. It can be used on a wide variety of materials such as ferrous and nonferrous metals, plastics and ceramics. It can detect subsurface as well as surface defects.
39
Which of the following defects are not acceptable for metal lines?
1. Cracked flare
2. Seams
3. Dents in the heel of a bend less than 20% of the diameter
4. Scratches/nicks on the inside of a bend less than 10% of wall thickness
5. Dents in straight section that are 20% of tube diameter
1, 2, 3, and 5.
Expl- 1. A cracked flare is cause for rejection of a metal fluid line.
2. Metal fluid lines must be made of seamless tubing.
3. A dent in the heel of a bend of more than 10% of the tube diameter is not acceptable.
4. Scratches/nicks less than 10% of the wall thickness of the tube are repairable if they are not in the heel of the bend.
5. A dent of more than 20% of the tube diameter is not acceptable
40
What nondestructive testing method requires little or no part preparation, is used to detect surface or near-surface defects in most metals, and may also be used to separate metals or alloys and their heat-treat conditions?
Eddy current inspection.
Expl- Eddy current inspection requires relatively little preparation of the part being inspected. It induces a magnetic field into the part which causes eddy currents to flow. Variations in the magnitude of the eddy currents affect this magnetic field, and when it is analyzed electronically, it gives information regarding such structural characteristics as flaws, discontinuities, thickness, and alloy or heat-treat condition of the material.
Eddy current inspection is used to locate defects both on the surface and below the surface.
41
What method of magnetic particle inspection is used most often to inspect aircraft parts for invisible cracks and other defects?
Continuous.
Expl- The continuous method of magnetic particle inspection is used for most aircraft parts because it provides the strongest magnetic field to attract the oxide from the fluid. In the continuous method of magnetic particle inspection, the part is either placed between the heads of the magnetizing machine or held inside the solenoid (coil).
Magnetizing current flows while the fluid is pumped over the part. In the residual method of magnetic particle inspection, used for some smaller parts, the parts are magnetized and the magnetizing current is shut off. Only residual magnetism is left in the part to attract the oxide.
42
How many of these factors are considered essential knowledge for x-ray exposure?
1. Processing of the film.
2. Material thickness and density.
3. Exposure distance and angle.
4. Film characteristics.
Three.
Expl- The factors of radiographic exposure are so interdependent that it is necessary to consider all factors for any particular radiographic exposure. These factors include, but are not limited to, the following:
1. Material thickness and density
2. Shape and size of the object
3. Type of defect to be detected
4. Characteristics of X-ray machine used
5. The exposure distance
6. The exposure angle
7. Film characteristics
8. Type of intensifying screen, if used
43
The testing medium that is generally used in magnetic particle inspection utilizes a ferromagnetic material that has
high permeability and low retentivity.
Expl- The testing medium used to indicate the presence of a fault in magnetic particle inspection is a finely ground iron oxide that has a high permeability and low retentivity, and is nontoxic. It is usually suspended in a light oil such as kerosine.
44
Which statement relating to the residual magnetizing inspection method is true?
It may be used with steels which have been heat treated for stressed applications.
Expl- In the residual method of magnetic particle inspection, the part is magnetized and removed from the magnetic field before the oxide-carrying fluid is pumped over it. Steel that has a high retentivity (retains its magnetism after the magnetizing force has been removed) can be inspected by the residual method. Steel that has been heat-treated for stressed applications has a high retentivity and it can be inspected by the residual method.
45
A mechanic has completed a bonded honeycomb repair using the potted compound repair technique. What nondestructive testing method is used to determine the soundness of the repair after the repair has cured?
Metallic ring test.
Expl- After a bonded honeycomb repair has been made using the potted-compound repair technique, the soundness of the repair can be tested by using the metallic ring test. The repaired surface is tested by tapping it with the edge of a coin. If the repair is sound, the tapping will produce a metallic ringing sound. If there is any void in the material, the tapping will produce a dull, thudding sound.
46
What two types of indicating mediums are available for magnetic particle inspection?
Wet and dry process materials.
Expl- The magnetic medium used for magnetic particle inspection can be applied either as a dry oxide powder dusted over the surface or (as is more commonly done) suspended in a light oil such as kerosene and pumped over the surface. The iron oxide used as the indicating medium is often treated with a fluorescent dye that causes it to glow with a green light when an ultraviolet light (black light) is shone on it.
47
Which of the following materials may be inspected using the magnetic particle inspection method?
1. Magnesium alloys.
2. Aluminum alloys.
3. Iron alloys.
4. Copper alloys.
5. Zinc alloys.
3
Expl- In order for a part to be inspected by the magnetic particle method, it must be magnetizable. The only magnetizable metals listed in the alternatives are iron alloys.
48
One way a part may be demagnetized after magnetic particle inspection is by
slowly moving the part out of an ac magnetic field of sufficient strength.
Expl- A steel part is magnetized by holding it in a strong, steady magnetic field that aligns all of the magnetic domains in the material. It is demagnetized by placing it in an AC magnetic field that continually reverses its polarity. This causes the domains to continually reverse their direction. As the domains are reversing, the part is slowly moved from the field so the domains remain in a disoriented state when the demagnetizing force is removed.
49
Which type crack can be detected by magnetic particle inspection using either circular or longitudinal magnetization?
45°.
Expl- Longitudinal magnetization produces a magnetic field that extends lengthwise in the material. It is used to detect faults that extend across the part, perpendicular to the lines of magnetic flux. Circular magnetization produces a magnetic field that extends across the material. It can detect faults that are oriented along the length of the part. Either type of magnetization can detect a fault that runs at 45° to the length of the part.
50
Which of the following methods may be suitable to use to detect cracks open to the surface in aluminum forgings and castings?
1. Dye penetrant inspection.
2. Magnetic particle inspection.
3. Metallic ring (coin tap) inspection.
4. Eddy current inspection.
5. Ultrasonic inspection.
6. Visual inspection.
1, 4, 5, 6.
Expl- Dye penetrant, eddy current, ultrasonic, and visual inspections may be used on aluminum forgings and castings. Magnetic particle inspection can only be used on ferrous metals, and the metallic ring inspection is used to check for delamination in bonded composite structural materials.
51
To detect a minute crack using dye penetrant inspection usually requires
a longer-than-normal penetrating time.
Expl- The amount of penetrant that can enter a small crack is determined by both the length of time the penetrant is allowed to remain on the surface and the temperature of the part. When looking for very small cracks, the part can be heated (but not enough to cause the penetrant to evaporate from the surface), and the penetrant can be allowed to stay on the surface for a longer than normal time before it is washed off.
52
Which of the following is a main determinant of the dwell time to use when conducting a dye or fluorescent penetrant inspection?
The size and shape of the discontinuities being looked for.
Expl- The dwell time (the time the penetrant is allowed to remain on the surface) is determined by the size and shape of the discontinuity being looked for.
53
When checking an item with the magnetic particle inspection method, circular and longitudinal magnetization should be used to
reveal all possible defects.
Expl- Since longitudinal magnetization detects faults that lie across a part, and circular magnetization detects faults that lie parallel to its length, a complete inspection that will show up all possible defects requires that the part be magnetized twice, longitudinally and circularly, and given two separate inspections.
54
In magnetic particle inspection, a flaw that is perpendicular to the magnetic field flux lines generally causes
a large disruption in the magnetic field.
Expl- In order to locate a defect in a part by the magnetic particle inspection method, it is essential that the magnetic lines of force pass approximately perpendicular to the defect. This causes the maximum disruption of the magnetic field and forms magnetic poles which attract the indicating medium across the defect.
55
If dye penetrant inspection indications are not sharp and clear, the most probable cause is that the part
was not thoroughly washed before the developer was applied.
Expl- After the penetrant has been on the surface of a part for the correct dwell time, the surface must be thoroughly washed to remove all traces of the penetrant. When the surface is clean and dry, the developer is sprayed or dusted on. Any penetrant left on the surface or in the pores of the material will stain the developer and faults will not show up as sharp and clear marks.
56
(1) An aircraft part may be demagnetized by subjecting it to a magnetizing force from alternating current that is gradually reduced in strength.
(2) An aircraft part may be demagnetized by subjecting it to a magnetizing force from direct current that is alternately reversed in direction and gradually reduced in strength.
Regarding the above statements,
both No. 1 and No. 2 are true.
Expl- Statement (1) is true. A part is demagnetized by placing it in an AC magnetic field whose strength is gradually reduced while it continually reverses its polarity. This leaves the domains in a disoriented state when the demagnetizing force is removed.
Statement (2) is also true. A DC magnetic field whose direction is continually reversed and the strength is gradually reduced may be used to demagnetize an aircraft part that has been inspected by the magnetic particle inspection method.
57
The pattern for an inclusion is a magnetic particle buildup forming
parallel lines.
Expl- Inclusions are impurities trapped inside a piece of metal when it was cast.
When the part is inspected by magnetic particle inspection, the inclusion does not show up as a clearly defined fault but the indication is fuzzy. Rather than sharply defined poles, there are several sets of poles that cause the oxide to form in a series of parallel lines.
58
A part which is being prepared for dye penetrant inspection should be cleaned with
a volatile petroleum-base solvent.
Expl- It is important when performing a dye penetrant inspection that the surface of the part be as clean as possible. Volatile petroleum-based solvents such as Stoddard solvent and naphtha are widely used for cleaning parts to be inspected.
59
Under magnetic particle inspection, a part will be identified as having a fatigue crack under which condition?
The discontinuity is found in a highly stressed area of the part.
Expl- Fatigue cracks usually show up in areas that have been subjected to high concentrations of stresses. They are likely to form where the cross-sectional area of the part changes sharply.
60
In performing a dye penetrant inspection, the developer
acts as a blotter to produce a visible indication.
Expl- To perform a dye penetrant inspection, the part to be inspected is thoroughly cleaned and soaked in a liquid penetrant which seeps into any cracks or defects that extend to the surface. After the part is soaked for the required dwell time, the penetrant is washed from the surface, and the surface is covered with a developer which, acting as a blotter, pulls the penetrant from the fault. The penetrant pulled out by the developer shows up as a visible indication.
61
What defects will be detected by magnetizing a part using continuous longitudinal magnetization with a cable?
Defects perpendicular to the long axis of the part.
Expl- A part magnetized longitudinally by current flowing through a cable wrapped around it will show up defects that are perpendicular (at right angles) to the long axis of the part.
62
Circular magnetization of a part can be used to detect which defects?
Defects parallel to the long axis of the part.
Expl- A part magnetized circularly by the magnetizing current flowing lengthwise through it, will show up defects parallel to the long axis of the part.
63
(1) In nondestructive testing, a discontinuity may be defined as an interruption in the normal physical structure or configuration of a part.
(2) A discontinuity may or may not affect the usefulness of a part. Regarding the above statements,
both No. 1 and No. 2 are true.
Expl- Statement (1) is true. In nondestructive testing, a discontinuity may be defined as an interruption in the normal physical structure or configuration of a part. Statement (2) is also true. A discontinuity may or may not affect the usefulness of a part.
64
What type of corrosion may attack the grain boundaries of aluminum alloys when the heat treatment process has been improperly accomplished?
Intergranular.
Expl- An aluminum alloy part is heat-treated by being heated in an oven and then removed and immediately quenched in cold water. If there is a delay between the time the part is removed from the oven and the time it is quenched, the grains in the metal will grow.
Because of this, there is a good probability that intergranular corrosion will develop along the boundaries of the grains within the metal.
65
Which of the following describe the effects of annealing steel and aluminum alloys?
1. decrease in internal stress.
2. softening of the metal.
3. improved corrosion resistance.
1, 2.
Expl- Steel and aluminum alloys may be annealed to decrease internal stresses and soften the metal. Annealing does not improve corrosion resistance.
66
Which heat-treating process of metal produces a hard, wear-resistant surface over a strong, tough core?
Case hardening.
Expl- Case hardening is a heat treatment process for steel in which the surface is hardened to make it wear resistant, but the inside of the metal remains strong and tough. Annealing is a heat treatment process for either ferrous or nonferrous metal that makes the metal softer. Tempering is a method of heat treatment in which some of the hardness is removed from a hardened metal. Removing some of the hardness makes the metal less brittle.
67
Which heat-treating operation would be performed when the surface of the metal is changed chemically by introducing a high carbide or nitride content?
Case hardening.
Expl- In case hardening, the surface of the metal is changed chemically by introducing a high carbide or nitride content. The core is unaffected chemically. When heat-treated, the surface responds to hardening while the core remains tough.
68
Normalizing is a process of heat treating
iron-base metals only.
Expl- Normalizing is a heat treating process in which an iron-base metal is heated to a temperature above its critical temperature and allowed to cool in still air. Normalizing reduces the stresses in the metal that were put there by the fabrication process.
69
Which of the following occurs when a mechanical force is repeatedly applied to most metals at room temperature, such as rolling, hammering, or bending?
1. The metals become artificially aged.
2. The metals become stress corrosion cracked.
3. The metals become cold worked, strain or work hardened.
3.
Expl- When a mechanincal force such as rolling, hammering, or bending is repeatedly applied to most metals at room temperature, the metals become cold worked, strain, or work hardened. They become so hard and brittle that they break.
70
The reheating of a heat treated metal, such as with a welding torch
can significantly alter a metal's properties in the reheated area.
Expl- When a heat-treated metal is reheated with a welding torch there is no close control of the temperature and the metal's properties in the reheated area may be significantly altered.
71
Why is steel tempered after being hardened?
To relieve its internal stresses and reduce its brittleness.
Expl- Steel is tempered after it is hardened to remove some of the internal stresses and make it less brittle. Tempering is done by heating it to a temperature quite a way below its critical temperature and allowing it to cool in still air.
72
What aluminum alloy designations indicate that the metal has received no hardening or tempering treatment?
3003-F.
Expl- In the temper designations used with aluminum alloy, these letters have the following meanings: F means 'as fabricated.' There has been no control over its temper.
H36 means the metal is non-heat-treatable, but it has been strain-hardened and stabilized to its 3/4 hard state. O means the metal has been annealed.
73
Which material cannot be heat treated repeatedly without harmful effects?
Clad aluminum alloy.
Expl- Clad aluminum alloy sheets have a core of high-strength aluminum alloy onto whose surface have been rolled a thin layer of pure aluminum. When clad sheets are heated in the process of heat treatment, some of the pure aluminum diffuses into the core alloy and weakens the sheet. The manufacturer of the aluminum specifies the number of times clad sheets can be heat-treated. Typically, they allow the sheet to be heat-treated only one to three times.
74
What is descriptive of the annealing process of steel during and after it has been annealed?
Slow cooling; low strength.
Expl- Annealing of steel is accomplished by heating the metal to just above the upper critical point, soaking at that temperature and cooling very slowly in the furnace.
Annealing of steel produces a fine-grained, soft, ductile metal without internal stresses or strains. In the annealed state steel has its lowest strength.
75
Unless otherwise specified, torque values for tightening aircraft nuts and bolts relate to
clean, dry threads.
Expl- The amount of torque used to screw a nut onto a bolt is critical in determining the integrity of a bolted joint. For torque to be uniform and to allow the torque specified by the manufacturer to be duplicated in the field, the following rule applies: Unless it is specified otherwise, the values given in a torque chart relate to clean, dry threads.
76
What is generally used in the construction of aircraft engine firewalls?
Stainless steel.
Expl- The material most generally used for firewalls on aircraft is stainless steel at least 0.015 inch thick. Mild steel, at least 0.018 inch thick and protected from corrosion, terneplate at least 0.018 inch thick, and Monel at least 0.018 inch thick may also be used.
77
What metal has special short-time heat properties and is used in the construction of aircraft firewalls?
Titanium alloy.
Expl- Titanium has some merit for short-time exposure up to 3,000 degrees F where strength is not important. Aircraft firewalls demand this requirement.
78
Unless otherwise specified or required, aircraft bolts should be installed so that the bolt head is
upward, or in a forward direction.
Expl- An accepted rule of thumb for installing bolts in an aircraft structure is to have the bolt head up, forward, or outboard. When the bolt is installed in this way, it is least likely to fall out if the nut should ever back off.
79
Alclad is a metal consisting of
pure aluminum surface layers on an aluminum alloy core.
Expl- Alclad is the registered trade name for an aluminum alloy sheet that has pure aluminum rolled onto its surfaces. The pure aluminum protects the alloy core from corrosion.
80
A fiber-type, self-locking nut must never be used on an aircraft if the bolt is
subject to rotation.
Expl- Fiber-type, self-locking nuts depend upon the fiber insert in the end of the nut gripping the bolt threads tight enough to prevent the nut backing off. Since there is no mechanical lock between the nut and the bolt, the FAA recommends that a fiber-type self- locking nut not be used in any installation in which the fastener is subject to rotation.
81
The Society of Automotive Engineers (SAE) and the American Iron and Steel Institute use a numerical index system to identify the composition of various steels. In the number '4130' designating chromium molybdenum steel, the first digit indicates the
basic alloying element.
Expl- In the SAE four-digit numbering system for identifying the composition of steel, the first two digits identify the basic alloy, and the second two digits show the percentage of carbon in hundredths of a percent.
82
(Refer to Figure 42.) Which of the bolt head code markings shown identifies an AN corrosion resistant steel bolt?
3
Expl- The cross on the head of a bolt identifies it as a standard AN bolt made of nickel alloy steel. The cross inside a triangle identifies the bolt as an NAS close-tolerance bolt. The single dash on the head of a bolt identifies it as a standard bolt made of corrosion-resistant steel.
83
Aircraft bolts with a cross or asterisk marked on the bolt head are
standard steel bolts.
Expl- A cross or asterisk on the head of a bolt identifies it as a standard AN bolt made of nickel alloy steel.
84
Which statement regarding aircraft bolts is correct?
In general, bolt grip lengths should equal the material thickness.
Expl- Bolts for installation in an aircraft structure should be selected so that their grip length (the length of the unthreaded shank) is equal to the thickness of the material being joined.
85
Generally speaking, bolt grip lengths should be
equal to the thickness of the material which is fastened together.
Expl- Bolts for installation in an aircraft structure should be selected so that their grip length (the length of the unthreaded shank) is equal to the thickness of the material being joined.
86
When the specific torque value for nuts is not given, where can the recommended torque value be found?
AC 43.13-1B.
Expl- A list of recommended torque values for nut-bolt combinations (without lubrication) are found in AC 43.13-1B on page 7-9.
87
(Refer to Figure 43.) Identify the clevis bolt illustrated.
3
Expl- The bolt shown in View 1 is a drilled-head, hex-head bolt. The bolt shown in View 2 is an eyebolt. The bolt shown in View 3 is a clevis bolt.
88
A particular component is attached to the aircraft structure by the use of an aircraft bolt and a castle tension nut combination. If the cotter pin hole does not align within the recommended torque range, the acceptable practice is to
change washers and try again.
Expl- When tightening castle nuts on bolts, the cotter pin holes may not line up with the slots in the nuts at maximum recommended torque, plus friction drag. If the hole and nut castellation do not align, change washers and try again. Exceeding the maximum recommended torque is not recommended.
89
A bolt with a single raised dash on the head is classified as an
AN corrosion-resistant steel bolt.
Expl- An AN corrosion-resistant steel bolt is identified by a single raised dash on its head.
90
How is a clevis bolt used with a fork-end cable terminal secured?
With a shear nut tightened to a snug fit, but with no strain imposed on the fork and safety tied with a cotter pin.
Expl- When a clevis bolt is used to secure a fork-end cable terminal, a shear castle nut should be used on the clevis bolt. The nut should be tightened until it is snug, but there must be no strain on the fork. The nut is secured to the clevis bolt with a cotter pin.
91
Where is an AN clevis bolt used in an airplane?
Where external tension loads are applied.
Expl- A clevis bolt should be used only where the load to which the bolt is applied is a shear load. A clevis bolt is not designed to take any type of tensile load. The threaded portion of a clevis bolt is short and there is a groove between the threads and the shank. The head of a clevis bolt has a screwdriver slot rather than flats for the use of a wrench.
92
A bolt with an X inside a triangle on the head is classified as an
NAS close tolerance bolt.
Expl- An NAS or an AN standard aircraft bolt has a raised cross or asterisk on its head. An NAS close-tolerance bolt has a cross or an X inside a triangle on its head. An AN corrosion-resistant steel bolt has a single raised dash on its head.
93
The core material of Alclad 2024-T4 is
heat-treated aluminum alloy, and the surface material is commercially pure aluminum.
Expl- Alclad 2024-T4 is a type of sheet metal that has a core of 2024-T4 solution-heat- treated aluminum alloy. Commercially pure aluminum is rolled onto the surfaces of the sheet for corrosion protection. The name Alclad is a registered trade name.
94
The aluminum code number 1100 identifies what type of aluminum?
99 percent commercially pure aluminum.
Expl- Aluminum identified by the code number 1100 is 99 percent commercially pure aluminum.
95
Aircraft bolts are usually manufactured with
class 3 fit for the threads.
Expl- A class-1 fit is a loose fit. This is used for coarse-thread stove bolts and square nuts. A class-2 fit is a free fit. It is used on some machine screws. A class-3 fit is a medium fit. It is used on almost all standard aircraft bolts.
96
In the four-digit aluminum index system number 2024, the first digit indicates
the major alloying element.
Expl- In the four-digit numbering system for identifying aluminum alloys, the first digit shows the major alloy used with the aluminum. The 1000 series is commercially pure aluminum. The 2000 series has copper as the main alloy. The 3000 series has manganese as the main alloy. The 4000 series has silicon as the main alloy. The 5000 series has magnesium as the main alloy. The 6000 series has magnesium and silicon in it. The 7000 series has zinc as the main alloy.
97
How is the locking feature of the fiber-type locknut obtained?
By the use of an unthreaded fiber locking insert.
Expl- A fiber-type lock nut is held firmly on the threads of a bolt by pressure caused by an unthreaded fiber insert locked into a recess in the end of the nut. When the bolt is screwed through the nut, it forces its way through the unthreaded fiber. The fiber grips the threads and applies a downward force between the threads in the nut and those on the bolt. This force prevents the nut vibrating loose.
98
Why should an aircraft maintenance technician be familiar with weld nomenclature?
In order to gain familiarity with the welding technique, filler material, and temperature range used.
Expl- It is extremely important to make a weld repair equal to the original weld. Identifying the kind of metal to be welded, identifying the kind of welding process used in building the part originally, and determining the best way to make welded repairs are of utmost importance.
99
Why is it considered good practice to normalize a part after welding?
To relieve internal stresses developed within the base metal.
Expl- When a part is welded, it has expanded and been fused to another part. When it cools, stresses inside it try to deform it. After a part has been welded, it should be normalized by heating it to a temperature above its critical temperature and allowed to cool in still air. This heating relieves the stresses in the metal, and the part is not so likely to crack in service.
100
Which condition indicates a part has cooled too quickly after being welded?
Cracking adjacent to the weld.
Expl- Heat causes metal to expand. Cooling causes it to contract. If a metal is cooled too quickly after it is welded, it will contract unevenly and stresses will remain in the metal. These stresses produce cracks adjacent to the weld.
101
Which tool can be used to measure the alignment of a rotor shaft or the plane of rotation of a disk?
Dial indicator.
Expl- A dial indicator is used to measure the alignment of a rotor shaft. The dial indicator is clamped to the structure, the contact finger is placed against the surface of the shaft, and the indicator is zeroed. The shaft is rotated and the dial indicator measures the amount the shaft is out of alignment. The plane of rotation of a disk may also be measured with a dial indicator.
102
Identify the correct statement.
Dividers do not provide a reading when used as a measuring device.
Expl- Dividers do not provide a reading when they are used as a measuring device. They are used by placing their points at the locations between which the measurement is to be taken. Then the distance between the points is measured with a steel machinist's scale.
103
Which tool is used to measure the clearance between a surface plate and a relatively narrow surface being checked for flatness?
Thickness gauge.
Expl- A part is checked for flatness by putting it on a surface plate and sliding a thickness gauge (a feeler gauge) between the part and the surface plate. The thickness of the feeler gauge that will slip between the part and the surface plate is the amount the part lacks being flat.
104
Which number represents the vernier scale graduation of a micrometer?
.0001.
Expl- The vernier scale (the series of parallel lines on the sleeve) on a vernier micrometer caliper is used to give an indication of one ten thousandth of an inch (0.0001 inch) of spindle movement.
105
Which tool is used to find the center of a shaft or other cylindrical work?
Combination set.
Expl- The center of a shaft or other circle can be found with the center head of a combination set. A combination set consists of a steel scale that has three heads that can be moved to any position on the scale and locked in place. The three heads are a stock head that measures 90° and 45° angles, a protractor head that can measure any angle between the head and the blade, and the center head that uses one side of the blade as the bisector of a 90-degree angle. The center head is placed against the circumference of the circle and a diameter is drawn along the edge of the blade. The head is moved about a quarter of the way around the circle and another diameter is drawn. The two diameters cross in the center of the circle.
106
If it is necessary to accurately measure the diameter of a hole approximately 1/4 inch in diameter, the mechanic should use a
small-hole gauge and determine the size of the hole by taking a micrometer reading of the ball end of the gauge.
Expl- The diameter of a small hole is measured by placing a ball-type, small-hole gauge in the hole and expanding it until its outside diameter is exactly the same size as the inside diameter of the hole. Remove the small-hole gauge from the hole and measure its outside diameter with a micrometer caliper.
107
What tool is generally used to set a divider to an exact dimension?
Machinist scale.
Expl- Dividers are not considered to be a precision measuring tool. They are set with a machinist's scale. One of the points of the dividers is placed at the one-inch mark on the scale. The other point is moved out until it touches the mark for the distance you want between the points.
108
What tool is generally used to calibrate a micrometer or check its accuracy?
Gauge block.
Expl- Micrometer calipers are precision measuring instruments. They are checked for accuracy by using gauge blocks. A 0- to 1-inch micrometer is checked with the thimble screwed down against the anvil. No gauge block is used. A 1- to 2-inch micrometer uses a 1-inch gauge block. A 2- to 3-inch micrometer uses a 2-inch gauge block.
109
What precision measuring tool is used for measuring crankpin and main bearing journals for out-of-round wear?
Micrometer caliper.
Expl- A vernier micrometer caliper is used to measure a crankpin and a main bearing journal for an out-of-round condition. Two measurements are made at right angles to each other. The difference between the two readings is the amount the shaft is out-of-round.
110
The side clearances of piston rings are measured with a
thickness gauge.
Expl- A thickness gauge (a feeler gauge) is used to measure the side clearance of a piston ring in its ring groove. The ring is installed in the groove and its outside edge is held flush with the side of the piston. A feeler gauge is placed between the side of the piston ring and the edge of the ring groove to measure the amount of clearance between the ring and the groove.
111
How can the dimensional inspection of a bearing in a rocker arm be accomplished?
Telescopic gauge and micrometer.
Expl- A dimensional inspection of a bearing in a rocker arm can be made by expanding a telescopic gauge inside the bushing (bearing) until its length is exactly the same as the inside diameter of the bushing. Remove the gauge and measure it with a vernier micrometer caliper. Measure the rocker arm shaft with the same vernier micrometer caliper.
The difference between the diameter of the shaft and that of the hole is the fit of the shaft in its bushing.
112
The twist of a connecting rod is checked by installing push-fit arbors in both ends, supported by parallel steel bars on a surface plate. Measurements are taken between the arbor and the parallel bar with a
thickness gauge.
Expl- Connecting rod twist is measured by fitting a feeler gauge (a thickness gauge) between the ends of arbors and the parallel bars.
113
The clearance between the piston rings and the ring lands is measured with a
thickness gauge.
Expl- A thickness gauge (a feeler gauge) is used to measure the side clearance of a piston ring in its ring groove. The ring is installed in the groove. Its outside edge is held flush with the side of the piston. A feeler gauge is placed between the side of the piston ring and the ring land (the edge of the ring groove) to measure the amount of clearance between the ring and the groove.
114
What may be used to check the stem on a poppet-type valve for stretch?
Micrometer.
Expl- The stem of a poppet valve is checked for stretch by using a vernier micrometer caliper to measure the stem diameter in the center of the stem and at the spring end. If the center diameter is less than the diameter at the spring end, the valve stem has been stretched.
115
Which tool can be used to determine piston pin out-of-round wear?
Micrometer caliper.
Expl- Piston pin out-of-round can be measured with a vernier micrometer caliper. Measure each end of the pin in two directions at right angles to each other. The difference in the two readings is the amount the pin is out-of-round.
116
(Refer to Figure 44.) Identify the weld caused by an excessive amount of acetylene.
3
Expl- The weld in view 1 was made too rapidly. The long and pointed appearance of the ripples was caused by an excessive amount of heat or by an oxidizing flame. If this weld were cross-sectioned, it would probably show gas pockets, porosity, and slag inclusions. The weld in view 2 has improper penetration and cold laps caused by insufficient heat. It appears rough and irregular and its edges are not feathered into the base metal.
The weld in view 3 has been made with a flame that had an excess of acetylene. There are bumps along the center of the bead and craters at the edge of the weld. Cross checks are apparent where the body of the weld is sound. If this weld were cross-sectioned, it would show pockets and porosity.
The weld in view 4 has considerable variations in depth of penetration. It often has the appearance of a cold weld.
117
(Refer to Figure 44.) Select the illustration which depicts a cold weld.
2
Expl- The weld in view 2 is a cold weld. It has improper penetration and cold laps caused by insufficient heat. It appears rough and irregular and its edges are not feathered into the base metal.
118
Holes and a few projecting globules are found in a weld. What action should be taken?
Remove all the old weld, and reweld the joint.
Expl- Blow holes and projecting globules are indications of a poor weld. All of the old weld bead should be removed and the material rewelded.
119
Select a characteristic of a good gas weld.
The weld should taper off smoothly into the base metal.
Expl- The bead of a gas weld that has good penetration and good fusion is uniform and straight. It has a slightly crowned surface that tapers off smoothly into the base metal.
120
One characteristic of a good weld is that no oxide should be formed on the base metal at a distance from the weld of more than
1/2 inch.
Expl- When making a good weld, the heat should be concentrated in the area being welded. The oxides that form on the base metal give an indication of the amount of heat put into the metal. Oxides formed for a distance of much more than 1/2 inch from the weld show that too much heat was put into the metal. The metal may have been weakened.
121
In examining and evaluating a welded joint, a mechanic should be familiar with
likely ambient exposure conditions and intended use of the part, along with type of weld and original part material composition.
Expl- It is important when evaluating a welded joint that you are familiar with the likely ambient conditions to which the part will be exposed, the intended use of the part, the type of weld, and the material of which the part is made.
122
(Refer to Figure 45.) What type weld is shown at A?
Butt.
Expl- Weld A is a single butt weld. Weld B is a double butt weld.
Welds C are both butt welds. Weld D is a rosette weld.
Weld E is a fillet weld. Weld F is an edge weld. Welds G are lap welds.
123
(Refer to Figure 45.) What type weld is shown at B?
Double butt.
Expl- Weld B is a double butt weld. Both sides of the material have been ground in a V and a bead is formed on both sides of the sheet.
124
(Refer to Figure 45.) What type weld is shown at G?
Lap.
Expl- The two welds shown at G are lap welds. When both edges are welded as is done here, the joint is called a double lap joint.
125
On a fillet weld, the penetration requirement includes what percentage(s) of the base metal thickness?
25 to 50 percent.
Expl- A properly made fillet weld has a penetration of 25 to 50 percent of the thickness of the base metal.
126
(Refer to Figure 46.) The measurement reading on the illustrated micrometer is
0.2851.
Expl- The thimble has been screwed out more than 0.275 inch (the third mark beyond the 2 is visible). The thimble has rotated just a bit more than ten hundredths of the way around, as is shown by the line on the sleeve. It is just beyond the 10 on the thimble. This means that 0.010 is added to the 0.275 on the sleeve. The vernier line on the barrel for 1 is lined up with one of the marks on the thimble, and this means that we add 0.0001 inch to the two other numbers we have. The total reading of this vernier micrometer is 0.275 + 0.010 + 0.0001 = 0.2851 inch.
127
(Refer to Figure 47.) What is the measurement reading on the vernier caliper scale?
1.436 inches.
Expl- The zero on the vernier scale is beyond the 1. This shows the measurement is more than 1 inch. It is beyond the 4. This shows it is more than 1.4 inch. It is beyond the first 0.025 mark on the bar. This shows that it is more than 1.425 inch. The 11 line on the vernier scale lines up with one of the marks on the bar. This 0.011 is added to the reading we have. The total reading is 1.425 + 0.011 = 1.436 inches.
128
(Refer to Figure 48.) What does the micrometer read?
.3004.
Expl- The thimble has been screwed out slightly more than 0.300 inch (the line by the 3 is just barely visible). The thimble has rotated just a bit beyond the zero line on the sleeve. The vernier line on the barrel for 4 is lined up with one of the marks on the thimble, and this means that we add 0.0004 inch to the other numbers we have. The total reading of this vernier micrometer is 0.300 + 0.0004 = 0.3004 inch.
129
(Refer to Figure 49.) The measurement reading on the micrometer is
.2792.
Expl- The thimble has moved out beyond two tenths of an inch (0.200 inch). It has moved out to a point that is beyond the third twenty-five thousandths of an inch mark. (0.075 inch.) The 4 mark on the thimble has just passed the scale on the sleeve (0.075 + 0.004 inch = 0.079). The 2 line on the vernier scale lines up with a number on the thimble. This adds 0.0002 inch. The total measurement is 0.2792 inch.
130
A primary reason why ordinary or otherwise nonapproved cleaning compounds should not be used when washing aircraft is because their use can result in
hydrogen embrittlement in metal structures.
Expl- Some nonapproved commercial cleaning compounds can cause a chemical reaction with some of the metals used in aircraft structure. This reaction releases hydrogen gas that can be absorbed into the metal and cause hydrogen embrittlement which weakens the metal and can cause cracking and failure.
131
How may magnesium engine parts be cleaned?
Wash with a commercial solvent, decarbonize, and scrape or grit blast.
Expl- Magnesium engine parts are cleaned by washing them with a commercial solvent such as naphtha or Stoddard solvent, then soaking them in a decarbonizer that has been proven safe for magnesium.
Any hard deposits that are not removed by this treatment can be removed with a scraper or
with a grit blast.
132
When an anodized surface coating is damaged in service, it can be partially restored by
chemical surface treatment.
Expl- An anodized coating is an electrolytically deposited film of oxide that covers the surface of the metal and keeps air and moisture away from it. If this coating is damaged, the metal can corrode. Damaged anodized coating can be repaired by treating the damaged area with a chemical conversion coating material such as Alodine. This chemical treatment forms a hard oxide film on the surface much like the anodized surface.
133
For which of the following reasons would a water break test be conducted?
To make certain that a bare metal surface is thoroughly clean.
Expl- Alodine can be applied to a surface after all traces of corrosion have been removed. The surface should be chemically cleaned until it supports an unbroken water film. Any breaks in the film of rinse water show that there some wax, grease, or oil on the surface, and further cleaning must be done.
134
Select the solvent recommended for wipe down of cleaned surfaces just before painting.
Aliphatic naptha.
Expl- Aliphatic naptha is a petroleum product between gasoline and kerosine in its characteristics. It is well suited for use as a cleaning agent for removing fingerprints, dust, and oily deposits that have settled on a surface to prepare the surface for painting. Dry-cleaning solvent, such as Stoddard solvent, leaves a slight residue on the surface that can interfere with the adhesion of the paint.
Aromatic naptha is a coal tar derivative that is toxic and attacks acrylics and rubber products. It is not suitable for wiping down a surface before painting.
135
Nickel-cadmium battery cases and drain surfaces which have been affected by electrolyte should be neutralized with a solution of
boric acid.
Expl- An area that has been affected by the electrolyte from a nickel-cadmium battery should be washed and neutralized with ammonia or a boric acid solution, allowed to dry thoroughly, then painted with an alkali-resisting varnish.
136
Which of the following are acceptable to use when utilizing chemical cleaning agents on aircraft?
1. Synthetic fiber wiping cloths when using a flammable agent.
2. Cotton fiber wiping cloths when using a flammable agent.
3. Atomizing spray equipment.
2 and 3.
Expl- When cleaning and/or depainting an aircraft surface with a flammable agent, use only a cotton wiping cloth or a natural bristle brush. Synthetic fibers tend to create unsafe charges of static electricity that could ignite the flammable agent. Emulsion-type cleaning agents may be applied to the surface with atomizing spray equipment. After the agent has penetrated the dirt or exhaust residue, it is scrubbed with a natural bristle brush and washed from the surface.
137
Select the solvent used to clean acrylics and rubber
Aliphatic naphtha.
Expl- Aliphatic naphtha is the only one of the three materials listed here that will not damage rubber or acrylic plastic. Be sure that aromatic naphtha (a coal tar derivative) is not used.
138
Fayed surfaces cause concern in chemical cleaning because of the danger of
entrapping corrosive materials.
Expl- Fayed surfaces are the parts of a structure that are covered in a lap joint. It is important when a structure is chemically cleaned that the fayed surfaces be protected so that corrosive materials do not seep between the sheets in the lap joints. This would cause corrosion to form in an area where it is hard to detect.
139
Caustic cleaning products used on aluminum structures have the effect of producing
corrosion.
Expl- Aluminum alloys such as those used in an aircraft structure are reactive metals. This means that they are likely to react with chemicals to form salts (corrosion). Many caustic cleaning products react with aluminum alloy and cause them to corrode.
140
Fretting corrosion is most likely to occur
when two surfaces fit tightly together but can move relative to one another.
Expl- Fretting corrosion is a form of corrosion that forms between closely fitting assembled parts that have a slight amount of relative motion. When sheets of aluminum alloy are riveted together, there should be no relative motion between the sheets or between the sheets and the rivets. But if there is a slight bit of movement, the protective oxide coating will be rubbed off of the metal and a new oxide coating will form. The material that has been rubbed off acts as an abrasive and accelerates the wear.
141
The rust or corrosion that occurs with most metals is the result of
a tendency for them to return to their natural state.
Expl- Corrosion is a natural phenomenon which attacks metal by chemical or electrochemical action and converts it into a metallic compound, such as an oxide, hydroxide, or sulfate. Corrosion occurs because of the tendency for metals to return to their natural state.
Noble metals like gold and platinum do not corrode since they are chemically uncombined in their natural state.
142
Which of the following are the desired effects of using Alodine on aluminum alloy?
1. A slightly rough surface.
2. Relieved surface stresses.
3. A smooth painting surface.
4. Increased corrosion resistance.
1 and 4.
Expl- Alodine is a conversion coating used to prepare aluminum alloys for painting. It etches the surface providing a microscopically rough surface and forms an oxide film on the surface to increase the corrosion resistance.
143
Which of the listed conditions is NOT one of the requirements for corrosion to occur?
The presence of a passive oxide film.
Expl- There are four conditions that must exist before corrosion can occur:
1. The presence of a metal that will corrode, the anode.
2. Presence of a dissimilar conductive material, the cathode, which has less tendency to corrode.
3. Presence of a conductive liquid, the electrolyte.
4. Electrical contact between the anode and cathode.
A passive oxide film is used as a corrosion preventive.
144
The lifting or flaking of the metal at the surface due to delamination of grain boundaries caused by the pressure of corrosion residual product buildup is called
exfoliation.
Expl- Exfoliation corrosion is a severe form of intergranular corrosion that normally forms in extruded metal. When metal is extruded, its grain structure is basically arranged in a series of layers. If an extrusion is improperly heat-treated, the grains are enlarged to the extent that intergranular corrosion can form along the grain boundaries within the metal. Severe intergranular corrosion in an extruded material causes it to delaminate (the layers of the metal to push apart). The surface of the metal lifts or flakes off.
145
A nonelectrolytic chemical treatment for aluminum alloys to increase corrosion resistance and paint-bonding qualities is called
alodizing.
Expl- Alodizing is the depositing of an oxide film on the surface of aluminum alloy by the application of the patented chemical, Alodine. The generic term for this type of nonelectrolytic corrosion protection is conversion coating. Anodizing is a method of electrolytically depositing a hard film of aluminum hydroxide on the surface of the metal.
146
Which of the following are acceptable to use in cleaning anodized surfaces?
1. Steel wool.
2. Brass wire brush.
3. Aluminum wool.
4. Stainless steel wire brush.
5. Fiber bristle brush.
3 & 5.
Expl- Anodized surfaces should never be cleaned with anything that could scratch through the anodizing and expose the untreated alloy, or that could contaminate the surface. For this reason only aluminum wool or fiber bristle brushes are suitable for cleaning these surfaces.
147
Intergranular corrosion in aluminum alloy parts
cannot always be detected by surface indications.
Expl- Intergranular corrosion forms along the grain boundaries within an aluminum alloy. Since this type of corrosion does not necessarily extend all the way to the surface of the metal in its early stages, it is quite possible for intergranular corrosion to reach an advanced state before it shows up on the surface.
148
Which of the following may not be detectable even by careful visual inspection of the surface of aluminum alloy parts or structures?
Intergranular corrosion.
Expl- Intergranular corrosion is an attack along the grain boundaries of an alloy and commonly results from a lack of uniformity in the alloy structure. Intergranular corrosion is difficult to detect in its early stage, and ultrasonic and eddy current inspection methods must be used.
149
What may be used to remove corrosion from highly stressed steel surfaces?
Fine-grit aluminum oxide.
Expl- Any corrosion on the surface of a highly stressed steel part is potentially dangerous, and all of the corrosion products must be removed. The removal can be done with mild abrasive papers such as rouge or fine grit aluminum oxide, or fine buffing compounds on cloth buffing wheels.
150
A primary cause of intergranular corrosion is
improper heat treatment
Expl- One of the primary causes for intergranular corrosion is improper heat treatment. If there is a delay in the time between the removal of a metal part from the heat treatment oven and the time the part is quenched, the grains of the metal have an opportunity to grow large enough that an electrical potential exists across the grain boundaries. This potential within the metal causes the formation of intergranular corrosion.
151
Corrosion should be removed from magnesium parts with a
stiff, nonmetallic brush.
Expl- Mechanical removal of corrosion from magnesium parts should be limited to the use of stiff hog-bristle brushes and similar nonmetallic cleaning tools.
152
Why is it important not to rotate the crankshaft after the corrosion preventive mixture has been put into the cylinders on engines prepared for storage?
The seal of corrosion preventive mixture will be broken.
Expl- When a reciprocating engine is prepared for storage, the inside of the cylinders are sprayed with a mixture of engine oil and a preservative oil. The oil mixture forms a seal on the cylinder wall and across the top of the piston. This mixture keeps air and moisture away from the metal surface. If the propeller is turned, the pistons will move and break the seal so that air and moisture can reach the cylinder walls and cause them to rust.
153
Which of the following is an acceptable first step procedure to help prevent scratching when cleaning a transparent plastic surface?
Flush the surface with clean water.
Expl- When cleaning the transparent plastic windshield of an aircraft, you should first flush it with a stream of clean fresh water to remove all sand and grit from the surface. After the surface is free of anything that can scratch the soft plastic, it can be washed with soap and water and then rinsed.
154
What should be done to prevent rapid deterioration when oil or grease come in contact with a tire?
Wipe the tire with a dry cloth followed by a washdown and rinse with soap and water.
Expl- When an aircraft tire comes in contact with oil or grease, remove all of the excess material by wiping it with a dry cloth. Then wash the tire with a solution of mild soap and warm water. Rinse the tire with fresh water and dry it with compressed air.
155
Galvanic corrosion is likely to be most rapid and severe when
the surface area of the anodic metal is smaller than the surface area of the cathodic metal.
Expl- Galvanic corrosion occurs when two dissimilar metals make electrical contact in the presence of an electrolyte. The rate at which corrosion occurs depends on the difference in the activities of the two metals. The greater the difference, the faster the corrosion occurs. The rate of galvanic corrosion also depends on the size of the parts in contact. If the surface area of the corroding material, the anode, is smaller than the surface area of the less active metal, the cathode, corrosion will be rapid and severe.
156
Corrosion caused by galvanic action is the result of
contact between two unlike metals.
Expl- Galvanic corrosion is caused by an electrolytic action that takes place when two metals that have a different place in the galvanic scale are in contact with each other and are covered with an electrolyte. The more anodic of the metals reacts with the electrolyte and some of it changes into salts (it corrodes).
157
Which of these materials is the most anodic?
Magnesium.
```
Expl- Some of the common metals in the order of their electrochemical activity are: (Most anodic)
Magnesium Zinc Cadmium
7075 Aluminum alloy
2024 Aluminum alloy Mild steel
Copper Stainless Steel Chromium
Gold
(Most cathodic)
```
158
The interior surface of sealed structural steel tubing would be best protected against corrosion by which of the following?
A coating of linseed oil.
Expl- The inside of structural steel tubing on an aircraft is protected from rust and corrosion by drilling small holes in the end of each section of the tube and pumping linseed oil through the hole. After the inside is thoroughly coated, the excess oil is drained out and the hole is sealed with a drive screw or by welding it shut.
159
Which of these materials is the most cathodic?
Stainless steel.
```
Expl- Some of the common metals in the order of their electrochemical activity are: (Most anodic)
Magnesium Zinc Cadmium
7075 Aluminum alloy
2024 Aluminum alloy Mild steel
Copper Stainless Steel Chromium
Gold
(Most cathodic)
```
160
Of the following, when and/or where is galvanic corrosion is most likely to occur?
At the interface of a steel fastener and aluminum alloy inspection plate in the presence of an electrolyte.
Expl- Galvanic corrosion occurs any time two dissimilar metals make electrical contact in the presence of an electrolyte.
161
One way of obtaining increased resistance to stress corrosion cracking is by
creating compressive stresses (via shot peening) on the metal surface.
Expl- Stress-corrosion cracking is an intergranular cracking of the metal which is caused by a combination of stress and corrosion. Shot peening a metal surface increases its resistance to stress corrosion cracking by creating compressive stresses on the surface. Any applied tensile stress must first overcome the surface compression before the tensile stress is felt.
162
(1) In the corrosion process, it is the cathodic area or dissimilar cathodic material that corrodes.
(2) In the Galvanic or Electro-Chemical Series for metals, the most anodic metals are those that will give up electrons most easily.
Regarding the above statements,
only No. 2 is true.
Expl- Statement (1) is false. It is the anodic, not the cathodic, material that is destroyed in the corrosion process. Statement (2) is true. Corrosion occurs in an anodic material when it gives up electrons to a cathodic material. The more easily a material gives up electrons, the more anodic, or corrosive, it is.
163
Spilled mercury on aluminum
causes rapid and severe corrosion that is very difficult to control.
Expl- Mercury spilled in an aircraft requires immediate action for its isolation and recovery to prevent it from causing corrosion damage and embrittlement of the aluminum structural components. Mercury is highly toxic and spreads very easily from one surface to another.
