1
AIRCRAFT HARDAWARE AND MATERIAL
Aircraft Material and Hardware Individual
Assignment
Name Kirubel Abebe Yigrem
ID Number: 109098
2
AIRCRAFT HARDAWARE AND MATERIAL
Aircraft Materials
Aircraft Materials: Ferrous
1. What properties are needed in the selection of different metals for aircraft part
construction and repair?
Many different metals are required in the repair of aircraft due to varying needs with
respect to strength, weight, durability and resistance to deterioration of specific
structures or parts.
2. Which metals are grouped under ferrous metals?
Group of metals having iron as their principal constituent.
3. What is the vital knowledge in the construction and maintenance of aircraft equipment,
especially airframes?
Knowledge and understanding of the uses, strengths, limitations, and other
characteristics of structural metals is vital to properly construct and maintain any
equipment
4. Write two methods of increasing metal hardness
 Cold working the metal and
 Heat treatment - in the case of steel and certain aluminum alloys.
5. What are the different types of strengths metals exhibit?
 Tensile Strength
 Shear Strength
 Compressive Strength
6. Which property of metals is necessary in sheet metal that is worked into curved shapes?
Malleability
7. Which property of metals is essential for making wire and tubing?
Ductility
8. Which property of metals is not desirable?
Brittleness
9. Which properties of metals are useful for metal welding?
Fusibility
3
AIRCRAFT HARDAWARE AND MATERIAL
10. Which properties of metals determine the type of jig to be used to control expansion
and contraction during metal welding?
Heat conductivity and Thermal expansion
11. What identification system is used to identify the chemical compositions of the
structural steels?
(SAE):Society of Automotive Engineers
(AISI) : American Iron and Steel Institute numerical index.
12. Explain the SAE and AISI four-digit numerical index
 The first digit identifies the principal alloying element in the steel.
 The second digit, the percentage of the alloying element.
 The last two digits, the percentage in hundredths of a percent of the carbon in the
steel.
 Where there is more than 0.99% carbon, a fifth digit is added.
13. What are incidental elements in a metal alloy?
Small unspecified quantities of certain elements present in alloy steels.
14. Write the different types of steel and their classification
 Low Alloy (Carbon Steel)
 High alloy (Alloy Steel)
Low alloy classified in to three depending on their carbon content
 Low carbon steel: contains 0.3% carbon
 Medium carbon steel: contains 0.3%-0.8% carbon
 High carbon steel: contains more than 0.8% carbon
And high alloy classified in to two
 Stainless steel
 Tool steel
15. Write the different forms and shapes in which metal stock is manufactured
 Sheets - made in a number of sizes and thicknesses. The sheet metal is usually formed
cold in such machines as presses, bending brakes, drawbenches, or rolls.
 Bars and rods - supplied in a variety of shapes, such as round, square, rectangular,
hexagonal, and octagonal.
 Tubing - in round, oval, rectangular, or streamlined shapes. The size of tubing is
generally specified by outside diameter and wall thickness.
 Extrusions
 Forgings - shaped or formed by pressing or hammering heated metal in dies.
 Castings - by pouring molten metal into molds. The casting is finished by machining.
16. How are sheet metal thicknesses designated?
The sizes and thicknesses sheet metal s commonly specified by nonlinear measurement
called gauge. The larger the gauge numbers the thinner the metal, Specification designate
thicknesses in thousandths of an inch.
4
AIRCRAFT HARDAWARE AND MATERIAL
17. How is the size of tubing is generally specified?
The size of tubing is generally specified by outside diameter and wall thickness.
18. What type of metals are commonly identified by spark test?
Ferrous metals like Alloy steel, High carbon steel, wrought iron, Low carbon steel.
19.What is the purpose of coke in the pig iron production?
The purpose of coke is used to supply the chemical element of carbon needed for the
reduction and carburization of the iron ore.
20.What are the chief alloying elements of cast iron?
Chief alloying elements are iron, silicon, and carbon.
21.What are the different types of cast iron?
 Gray cast iron
 White cast iron
 Chilled cast iron, and
 Malleable cast iron
22.What is wrought iron?
It is a metal that contains high purity iron and iron silicate. It is very low in carbon
23. What is the difference between commercially available ferrous metals and steel?
Commercially available ferrous metals contain a proportion of carbon, in fact cast iron
contains more carbon than high carbon steel! The difference is in the form that the
carbon takes; steel never contains free carbon (graphite).
24.what is the carbon content of plain carbon steel?
Plain carbon steels are alloys of iron and up to 1.7% carbon although 1.5% is seldom
exceeded.
25.Discuss the three groups of plain carbon steel.
 Low carbon or 'mild' steel contains up to 0.3% carbon,
 Medium carbon steel 0.3% to 0.8% carbon and
 High Carbon Steel 0.8% to 1.7% carbon.
26. What happens to carbon which is above 1.7 percent? What is the effect?
Above 1.7% Carbon, the excess is in the form of free (uncombined) carbon or graphite,
which has very low strength (e.g., cast iron).
27. List the different impurities found in most ordinary steels and discus their effect
 Manganese, left over during the steel making process dissolves in steel, slightly increasing
its strength and hardness, and helps reduce the Sulphur content of the steel.
 Sulphur and phosphorous are harmful impurities causing brittleness in steels.
5
AIRCRAFT HARDAWARE AND MATERIAL
28. Describe pearlite, ferrite and cementite.
 Ferrite is soft, ductile and not very strong
 Pearlite is strong and tough, but soft enough to be worked.
 Cementite is very hard and brittle.
29. Mention two conditions which affect the properties of steel metals?
 Composition
 The condition of its crystalline grains.
30. Discuss the effects of cold working and hot working
 Cold working: is performed on the metal at normal temperatures, such as bending,
squeezing and stretching the grains become distorted and stressed, and the metal
becomes stiff and brittle. In this state it is said to be 'work hardened'.
 Hot working: such as forging, hot rolling and extrusion at elevated temperatures, can lead
to excessive grain growth, which occurs well below the melting point and which again
weakens the metal.
31. How are alloy steels named?
Alloy steels are normally named after the principal alloying elements.
32. What is the percentage of manganese and silicon in alloy steel?
In carbon steels manganese normally varies up to 1 percent and silicon up to 0.3 percent.
33. What is the corrosion-resistant steel most often used in aircraft construction?
The corrosion-resistant steel most often used in aircraft construction is known as 18-8
steel because it is 18 %chromium and 8 % nickel. One distinctive feature of 18-8 steel is
that its strength can be increased by cold working.
34. What is the major disadvantage of 'Corrosion Resistant Steels'?
These steels expand about 50 percent more than mild steel and conduct heat only about
40 percent as rapidly; they are more difficult to weld.
35. Which alloy steel is adaptable for welding and, for this reason, are used principally for
welded structural parts and assemblies?
Chrome-molybdenum steel
36. What is the result of a chemical identification test (solution of cupric chloride and
hydrochloric acid) on Inconel (60% nickel, 29% chromium, 6% iron) and stainless steel?
 If the metal is stainless steel, the copper in the cupric chloride solution will be deposited on
the metal leaving a copper-colored spot.
 If the sample is Inconel, a shiny spot will be present.
6
AIRCRAFT HARDAWARE AND MATERIAL
37. What is heat treatment process?
Heat treatment is a series of operations involving the heating, soaking and cooling of
metals in the solid state.
38. What are the effects of heat treatment?
Its purpose is to change properties of the metal so that it will be harder, stronger or more
resistant to impact. It can also make a metal softer and more ductile when it has become
work hardened and release internal stresses after cold working.
39. How should steel be heated during heat treatment?
During heat treatments, steel should be heated slowly and uniformly. Close control of
temperature is essential.
40. What are the different methods of cooling after heat treatment?
 Slow Cooling - after heating can be carried out in the furnace, in air
 Fast Cooling - quenching in liquid depending on the process. Oil is normally used for
quenching alloy steels.
41. What are the important considerations in the heat treatment of steel parts?
The first important consideration in the heat treatment of a steel part is to know its
chemical composition. This, in turn, determines its upper critical point.
The next consideration is the rate of heating and cooling to be used. Carrying out these
operations involves the use of uniform heating furnaces, proper temperature controls, and
suitable quenching mediums.
42. What happens at the 'critical"' or 'arrest' points during heat treatment?
During these periods of arrest, the metal absorbs heat, but instead of raising the
temperature, the heat brings about a structural change in the steel.
43. At what temperature does a change in the internal structure of a ferrous metal occur during
heat treatment?
The temperature at which the changes start (the lower critical point) is the same for all
steels and is about 723°C.
44. Describe the condition of carbon in steel at normal temperature.
At ordinary temperatures, the carbon in steel exists in the form of particles of iron carbide
scattered throughout an iron matrix known as “ferrite.”
45. What determines the hardness of a steel?
The number, size, and distribution of particles of iron carbide determine the hardness of
the steel.
46. What happens to the carbon at elevated temperatures?
7
AIRCRAFT HARDAWARE AND MATERIAL
At elevated temperatures, the carbon is dissolved in the iron matrix in the form of a solid
solution called “austenite,” and the carbide particles appear only after the steel has been
cooled.
47. Describe the effect of cooling rate on the formation of iron carbide during heat treatment.
If the cooling is slow, the carbide particles are relatively coarse and few. In this condition,
the steel is soft. If the cooling is rapid, as by quenching in oil or water, the carbon
precipitates as a cloud of very fine carbide particles, and the steel is hard.
48. What is the reason that pure iron, wrought iron, and extremely low carbon steels cannot be
appreciably hardened by heat treatment?
Since they contain no hardening element which is carbon.
49. What affects the maximum hardness of carbon steel during heat treatment?
In plain carbon steel, the maximum hardness depends almost entirely on the carbon
content of the steel. As the carbon content increases, the ability of the steel to be
hardened increases.
However, this increase in the ability to harden with an increase in carbon content
continues only to a certain point. In practice, that point is 0.85 percent carbon content.
When the carbon content is increased beyond 0.85 percent, there is no increase in wear
resistance.
50. Describe the hardening process of steel.
For most steels, the hardening treatment consists of heating the steel to a temperature
just above the upper critical point, soaking or holding for the required length of time, and
then cooling it rapidly by plunging the hot steel into oil, water, or brine. Although most
steels must be cooled rapidly for hardening, a few may be cooled in still air.
51. What is the time allowed until the temperature is cooled below 1000"F during quenching?
What would happen if this time is exceeded?
It must be cooled to below 1,000 °F in less than 1 second. Should the time required for the
temperature to drop to 1,000 °F exceed1 second, the austenite begins to transform into
fine pearlite. This pearlite varies in hardness, but is much harder than the pearlite formed
by annealing and much softer than the martensite desired. After the 1,000 °F temperature
is reached, the rapid cooling must continue if the final structure is to be all martensite.
52. What is the effect of adding alloys to steel on the time limit for the temperature drop to
1,000 F during quenching?
When alloys are added to steel, the time limit for the temperature drop to 1,000 °F
increases above the 1 second limit for carbon steels. Therefore, a slower quenching
medium will produce hardness in alloy steels.
53. What is the cracking temperature range during quenching?
8
AIRCRAFT HARDAWARE AND MATERIAL
Temperature range from 200 °F down to room temperature is the cracking range. steel
must be tempered just before it becomes cold.
54. List some precautions related to hardening heat treatment.
A variety of different shapes and sizes of tongs for handling hot steels is necessary
When selective hardening is desired, portions of the steel may be protected by covering
with alundum cement or some other insulating material.
55. What is the purpose of tempering?
Tempering reduces the brittleness imparted by hardening
56. What is the temperature at which tempering is conducted?
Tempering is always conducted at temperatures below the low critical point of the steel.
57. What is annealing of steel?
Annealing of steel produces a fine grained, soft, ductile metal without internal stresses or
strains. It is the process of softening a hardened steel.
58. Describe the annealing process of steel.
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.
59. what is the purpose of normalizing steel?
The normalizing of steel removes the internal stresses set up by heat treating, welding,
casting, forming, or machining.
60. How is normalizing accomplished?
Normalizing is accomplished by heating the steel above the upper critical point and cooling
in still air.
Aircraft Materials: non-Ferrous
1. Give some examples of "nonferrous" metals
Aluminum, titanium, copper, and magnesium, as well as such alloyed metals as Monel and
Babbitt.
2. Which aluminum alloy is susceptible to corrosive action?
Alloys in which substantial percentages of copper are used are more susceptible to
corrosive action.
3. Which aluminum alloys show little attack in corrosive environments?
Aluminum alloys in which the principal alloying ingredients are manganese, chromium, or
magnesium and silicon show little attack in corrosive environments.
9
AIRCRAFT HARDAWARE AND MATERIAL
4. What properties of aluminum make it preferable for aircraft use?
 Light weight.
 Because of its high strength-to-weight ratio
 Comparative ease of fabrication
 Aluminum melts at the comparatively low temperature of 1 250°𝐹.
 Nonmagnetic and is an excellent conductor.
5. What are the two classes of aluminum alloys? which one is most widely used in aircraft
construction?
 The casting alloys (those suitable for casting in sand, permanent mould, or die castings),
and
 The wrought alloys (those which may be shaped by rolling, drawing, or forging).
Of these two, the wrought alloys are the most widely used in aircraft construction
6. Aluminum casting alloys are divided into heat treatable and non-heat treatable. (True/ False)
True
7. Explain the four-digit index system of aluminum alloy identification 1XXX group.
 The first digit indicates the principal alloying element.
 The second digit identifies the alloy modification. 0 indicates that the alloy is original. 1
indicates that the alloy has been modified once etc.
 The 3rd and 4th digits identify the specific aluminum alloy.
9. Write the major alloying elements in each group of aluminum alloy.
In the 1st group: 1xxx aluminum
2nd group: 2xxx Manganese
: 3xxx Copper
: 4xxx silicon
: 5xxx Magnesium
: 6xxx Magnesium and silicon
: 7xxx Zink
: 8xxx other elements
rd
3 group: unused series
10. What is the major problem of magnesium metal?
Magnesium is difficult to obtain from its ore, and is now normally extracted from sea
water or deep well brine by electrolysis.
11. How should we fight magnesium fires?
Magnesium fires should be fought with dry powder extinguishing as water and foam will
intensify combustion and may cause explosions.
12. How can corrosion on magnesium be prevented?
 Chemical surface treatments and coating processes give it good protection from
corrosion by excluding oxygen.
10
AIRCRAFT HARDAWARE AND MATERIAL
 Use of compatible bolts, nuts, rivets etc. is also important in combating dissimilar metal
corrosion.
13. What does the number 31 indicate in the AZ31A T4 designation of magnesium alloys?
31 indicate 3% aluminum and 1% zinc.
14. Write the two types of nickel alloys and their nickel content.
There are basically two nickel alloys used in aircraft. They are Monel and Inconel. Monel
contains about 68 percent nickel and 29 percent copper
15. What property of copper makes it ideal for making wire?
Malleable and ductile
16. What is brass? Muntz? Bronze?
 Brass is a copper alloy containing zinc and small amounts incidental elements
 Muntz metal is a brass composed of 60 percent copper and 40 percent zinc. It has
excellent corrosion resistant qualities in salt water.
 Red brass, sometimes termed “bronze” because of its tin content, is used in fuel and oil
line fittings.
17. what makes titanium an excellent corrosion resistant metal?
Titanium has excellent corrosion resistance properties due to the oxide film which
forms. It is not normally susceptible to stress, fatigue, intergranular or galvanic
corrosion, pitting or localized attack.
18. Why is titanium treated with chlorine gas to form a coating of titanium dioxide?
Under certain circumstances it will burn in air, so to prevent its reaction with oxygen or
nitrogen it may be treated with chlorine gas to form a coating of titanium dioxide.
19. What are the three classes of titanium?
A. Alpha: is weldable, tough, strong both hot and cold and resistant to oxidization.
B. Beta: Has excellent bend ductility, strong both hot and cold but vulnerable to
contamination.
C. Combined alpha and beta with compromised performance. Strong cold and warm but
weak hot, excellent forgeability, good bendability, moderate contamination resistance.
20. What are some of the problems associated with titanium?
Special care is required when machining titanium due to its extreme work hardening
properties, Fine titanium swarf or powder, even when moist, is a possible fire risk. Piles
of fine titanium
21. What type of hardening treatment is done on aluminum alloy by low-temperature thermal
treatment after solution heat treatment?
11
AIRCRAFT HARDAWARE AND MATERIAL
Aging
22. What is the effect of using higher -than- recommended temperatures during solution heat
treatment?
When excessive temperatures are used, there is danger of melting the low-melting
constituents of some alloys with consequent lowering of the physical properties of the
alloy. Even if melting does not occur, the use of higher -than- recommended
temperatures promotes discoloration and increases quenching strains.
23. How is the time at temperature, referred to as soaking time measured?
Soaking time is measured from the time the coldest metal reaches the minimum limit of
the desired temperature range.
24. What are the effects of excessive soaking period?
Excessive soaking period aggravates high-temperature oxidation.
Aircraft Materials: Composite & Non-Metallic
1. What is a composite?
A Composite is a combination of two or more macro constituents which are different in
composition or form.
2. Give two examples of composite materials
 Epoxy adhesive.
 Adobe bricks
3. What are the two major components of a composite material?
Fibers- carry load
Matrix - specially formulated medium
4. What is the transverse property of a resin matrix?
The ability of the matrix to transfer loads from one fiber to another, are called transverse
properties.
5. What is the relationship between the load-carrying properties of a fibrous composite and the
direction of load applied?
The load-carrying properties of a fibrous composite are greatest when the load applied
runs in the same direction as the fibers.
Loads that do not run parallel to the reinforcement fibers must, at least in part, be
transferred through the matrix, which typically has the lowest load-carrying capability.
6. Mention three common types of reinforcing fibers.
 Kevlar
 carbon fiber, commonly referred to as graphite (even though it is not a mined material),
12
AIRCRAFT HARDAWARE AND MATERIAL
 Spectra
7. Mention three important advantages of fibrous reinforced composite materials.
 High strength to weight ratio
 High durability
 Resistant to corrosion
8. What is a sandwich structure?
It is a special class of composite materials that is fabricated by attaching two thin but stiff
skins to a lightweight but thick core.
9. How is a solid laminate constructed?
By layering multiple sheets of high quality craft paper together with thermosetting
phenolic resins and are then pressed together using intense heat and pressure.
10. Mention three areas on the aircraft where transparent plastic materials could be Used?
Transparent plastic materials used in aircraft are canopies, windshields, windows.
11. Describe the properties of the two classes of plastics.
The two classes are: thermoplastic and thermosetting.
 Thermoplastic materials will soften when heated and harden when cooled. These
materials can be heated until soft, and then formed into the desired shape.
 Thermosetting plastics harden upon heating, and reheating has no softening effect.
These plastics cannot be reshaped once being fully cured by the application of heat.
12. Which form of transparent plastics is used in many pressurized aircraft?
Because of its shatter resistant qualities, laminated plastic is superior to solid plastics and is
used in many pressurized aircraft.
13. What are the disadvantages of natural rubber?
 Its suitability for aircraft use is somewhat limited because of its inferior resistance to
most influences that cause deterioration.
 It swells and often softens in all aircraft fuels and in many solvents (naphthas, and so
forth).
 Natural rubber deteriorates more rapidly than synthetic rubber.
14. What are the most widely used synthetic rubbers?
The most widely used are the butyls, Bunas, and neoprene
15. List some of the purposes of sealants
 Used to block the passage of fluids through openings in materials
 Used to reinforce and seal aircraft parts to improve structural integrity
16. Which type of PR1440 sealant can be applied with brush?
Type A
17. How is mechanical adhesive bond achieved?
The adhesive penetrates into the surface and forms a mechanical lock, by keying into
surface irregularities.
It also forms re-entrants, where the adhesive penetrates behind parts of the structure, and
becomes an integral part of the component to be joined.
18. What are the four main types of stress on adhesive joints?
 Tensile stress
 Shear stress
13
AIRCRAFT HARDAWARE AND MATERIAL
 Compression stress
 Cleavage stress
19. What type of adhesives are used where there is slight relative movement of the joint is
essential?
Flexible adhesives are used when some flexing, or slight relative movement of the joint, is
essential and where high load-carrying properties are not paramount. In general, flexible
adhesives are based on flexible plastics or elastomers. They are used for internal
decorative trim etc. Examples include Evostik and Tretobond.
20. Write the different forms of adhesives
liquid, paste and film
21. Which wood species is taken as a reference for aircraft wood selection?
Sitka spruce
22. How is laminated wood made?
Laminated wood is made of strips of wood glued together in such a way that the grain of all
strips run in the same direction.
23. Write three types of glues used to join aircraft wood.
Plastic resin and resorcinol are generally FAA -approved for use on certificated airplanes.
24. What does a splintering of wood indicate upon sticking a sharp-pointed knife blade into a
discolored area and prying?
If it comes up as a long splinter, the wood is good, and no decay is present. But if it comes up
as a chunk about the size of the knife blade tip or crumbles when disturbed by the knife, the
wood has decayed and must be replaced.
25. Write the requirements for aircraft wood selection.




Moisture content -12%
Minimum annual rings per inch-6
Maximum slope of the grain -1 inch in 15 inches
26. List two types of organic aircraft covering fabrics
Cotton and linen
27. List two types of inorganic aircraft covering fabrics
polyester fibers and fabric made of glass filaments.
28. Write the three steps of aircraft fabric covering process
 First, select an approved fabric
 Second, follow the applicable STC steps to attach the fabric to the airframe and to
protect it from the elements.
 Third, apply the approved topcoat to give the aircraft its color scheme and final
appearance.
14
AIRCRAFT HARDAWARE AND MATERIAL
Corrosion
1. What is corrosion?
Corrosion is the electrochemical deterioration of a material or its properties due to its
chemical reaction with the surrounding environment.
2. What are the four necessary conditions for corrosion to occur?
 A metal which has a tendency to corrode must be present (the corroding metal is called
the anode);
 A dissimilar conductive material (the cathode), which has less tendency to corrode than
the anode, must be present (a dissimilar metal may be a different metal, a protected part of
the same metal, or conductive plastic);
 A conductive liquid (electrolyte) must connect the anode and cathode (so that ions can
carry electric current between them); and
 Electrical contact between the anode and cathode (usually in the form of metal-tometal contact) must exist so that electrons can move between the anode and the cathode.
3. How can an electrolyte be prevented from contacting the anode and cathode?
paint film on a metal surface will prevent the electrolyte from connecting the anode and
cathode
4. What is galvanic corrosion and how is it recognized?
Galvanic corrosion occurs when different metals are in contact with each other in the
presence of an electrolyte
5. How do microorganisms (bacteria and fungi) cause corrosion?
 The tendency of the growth to hold moisture, which then causes corrosion;
 Digestion of the substrate as food for the microorganism; or
 Corrosion of the surface beneath the growth by secreted corrosive fluids.
6. How can the presence of bacteria and fungi be identified?
The presence of bacteria and fungi can readily be identified by damp, slimy, and bad smelling
growths. These vary in color from black, blue-green, green, to yellow.
7. What type of corrosion results in cracking?
stress corrosion
8. What type of corrosion results in localized holes in the metal?
Pitting Corrosion
9. Where does exfoliation corrosion most often occur?
Exfoliation occurs on extruded rolled, wrought, and forged high strength aluminum and
magnesium parts
15
AIRCRAFT HARDAWARE AND MATERIAL
10. What type of corrosion occurs where a stagnant solution pooled at gasket surfaces, lap
joints, and under bolt or rivet heads?
Crevice corrosion
11. What type of corrosion is identified by its characteristic wormlike trace of corrosion
products beneath the coating?
Filiform Corrosion
12. What type of corrosion occurs at contact areas between materials under load subject to
repeated vibration?
Fretting corrosion
13. Describe the effect of the relative size of anode to cathode on the rate of corrosion.
If the surface area of the corroding metal (the anode) is smaller than the surface area of the
less active metal (the cathode), corrosion will be rapid and severe. But, when the corroding
metal is larger than the less active metal, corrosion will be slow and superficial.
Aircraft Hardware
1. What type of fastening or attaching devices are used on aircraft parts that must be taken
apart and put back together at frequent intervals.
Quick-release fasteners
2. What are the two requirements of aircraft fasteners?
Give the required security of attachment and rigidity.
3. Write the difference and similarity between bolts and screws.
BOLT
SCREW
Used where great strength is
required
Used where strength is not the deciding factor
Blunt threaded end
either blunt or pointed threaded end
Assembled with nut
Fit into a receptacle or the material itself
Short threaded and long grip length
Long threaded section and no clearly defined grip
length
Tightened by turning the nut
Always tightened by turning its head
4. What is the diameter and number of threads per inch of a 4-28 bolt?
1/4-inch (4/16 inch) diameter and 28 threads in 1 inch of its threaded length
16
AIRCRAFT HARDAWARE AND MATERIAL
5. Write the four standards which specifies the diameter, length and threads of fasteners. And
mention the features of each standard.
 NC : American national coarse
 NF: American national fine
 UNC : American standard unified coarse
 UNF: American standard unified fine
6. What does the class of thread indicate?
The class of a thread indicates the tolerance allowed in manufacturing
7. What identification is used to identify male (external) threads and b for female (internal)
threads on a fastener?
A identifies male
B identifies female
 A male thread has the grooves known as the thread on the outside, has a straight thread
and 30 degree internal chamfer.
 A female thread has the grooves known as the thread on the inside, and has a straight
thread and an inverted 30 degree .
8. Can class 3A bolt be used with class 4B nut? why?
No , Using mismatch bolt and nut can cause bolt breaking of thightness.
9. Write the common specifications for aircraft bolts.
AN, NAS or MS