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Knowledge Levels

• Knowledge levels for Aircraft Maintenance Licence categories A, B1, B2 are indicated by numerical indicators (1, 2, or 3) for each subject.
• Category C applicants must meet either B1 or B2 basic knowledge levels.

Knowledge Indicators

Level 1

• Applicant should be familiar with basic elements.
• Applicant should give simple descriptions using common words and examples.
• Applicant should use typical terms

Level 2

• Applicant should have a general knowledge of theoretical and practical aspects.
• Applicant should be able to understand theoretical fundamentals.
• Applicant should give general descriptions with typical examples
• Applicant should apply mathematical formulas with physical laws.
• Applicant should read and understand sketches, drawings and schematics.
• Applicant should apply knowledge practically using detailed procedures.

Level 3

• Applicant should have detailed knowledge of theoretical and practical aspects.
• Applicant should combine and apply elements of knowledge logically
• Applicant should know the theory and interrelationships with other subjects.
• Applicant should give detailed descriptions using theoretical fundamentals and specific examples.
• Applicant should understand and use mathematical formulae.
• Applicant should read, understand, and prepare sketches, simple drawings and schematics.
• Applicant should be able to apply his knowledge in a practical manner using manufacturer's instructions.
• Applicant should interpret results and apply corrective action.

Aircraft Materials - Ferrous (6.1.1)

• The content covers the characteristics and properties of common alloy steels used in aircraft, identification of common alloy steels, heat treatment of alloy steels and application of alloy steels

Metal Alloy Steels

• Metal characteristics - features or qualities of a material.
• Metal property - attribute, quality, or characteristic of a metal.
• Alloying can change material characteristics dramatically
• Adding carbon to steel increases hardness.

Ferrous Metal Characteristics and Properties

• Metals possess characteristics such as strength, hardness, malleability, ductility, brittleness, conductivity, expansion, elasticity, toughness, fusibility and density.

Strength

• Metal strength is determined by percentages of parent metal and other elements used to make an alloy.
• Types of strengh: tensile, compressive, shear, torsional, bending, fatigue, and impact (toughness)

Metal Loading Forces

• Tensile strength: ability of sheet metal to withstand stress in tension.
• Yield strength: stress at which material strain changes from elastic to plastic deformation, causing permanent deformation.
• Ultimate strength: maximum stress a material can withstand when subjected to tension, compression or shearing; the maximum stress on the stress-strain curve.
• Breaking strength: stress coordinate on the stress-strain curve at the point of rupture.

Fundamental Loading Forces

• Compressive strength: ability to withstand being pressed or squeezed.
• Shear strength: ability to withstand shear stress.
• Torsional strength: ability to resist rotational shear.
• Bending strength: metal's bending strength.
• Fatigue strength/endurance strength: ability to resist repeated loading.
• Impact strength (toughness): ability to resist shock.

Hardness

• Hardness is the ability of a metal to withstand cutting, penetration or abrasion.
• Tensile strength of steel directly relates to hardness.
• Metals harden through heat-treating or work hardening.
• Metals are softened by annealing.

Malleability

• Malleability: material's ability to be bent, formed or shaped without cracking or breaking.
• Hardness and malleability are generally considered opposite properties.
• Metals are annealed or softened to increase malleability for complex shapes.
• Metal being fully annealed when the forming is started, but hammering and shaping can harden it to such an extent that it must be re-annealed before forming is completed.
• Malleable metal is able to be hammered, pressed, or rolled into thin sheets without breaking
• Malleable metal is highly ductile and a non-malleable metal is brittle

Ductility

• Ductility: ability of metal to be drawn into wire stock, extrusions or rods.
• Ductile metals are preferred for aircraft use because of their ease of forming and resistance to failure under shock loads.

Brittleness

• Brittleness: material's tendency to break or shatter when exposed to stress; the opposite of ductility and malleability.
• A brittle metal is more apt to break or crack before it changes shape..
• Structural metals are often subjected to shock loads.
• Brittleness is not a desirable property
• Cast iron and very hard steel are brittle ferous metals.

Elasticity

• Elasticity: metal's tendency to return to its original shape after normal stretching and bending.
• The point at which a metal no longer returns to its original shape after a deforming force is removed is the elastic limit
• Non-ferous metals have low elastic limits, while hard spring steel is very high.

Toughness

• Toughness is a material's ability to resist tearing or breaking when it is bent or stretched.
• Hammer faces and wrenches are examples of metal that must be tough and hard.

Conductivity

• Conductivity - the property which enables a metal to carry heat or electricity.
• If a metal can transmit heat, it is thermally conductive.
• Metals that conduct heat also conduct electrons, making them good electrical conductors.
• Electrical conductivity is the measurement of a material's ability to allow electron flow.

Thermal Expansion

• Thermal expansion: ability of a metal to expand when heated and shrink when cooled.
• Amount of expansion or contraction at specific temperatures: coefficient of expansion.
• All aircraft experience thermal expansion and contraction as ambient temperature changes.

Fusibility

• Fusibility: ability of metal to be joined by heating and melting.
• Fusing metal means to melt two or more compatible pieces of metal into one continuous part.
• Correct term: fusion joining or welding.

Ferrous Metals

• Ferrous metal: any alloy that contains more iron.

Iron (Ferrite)

• Ferrous metals include steel, cast iron, and titanium, as well as alloys of iron with other metals (such as with stainless steel).
• The most common ferrous metal in aircraft structures is steel, an alloy of iron with a controlled amount of carbon added.
• Iron in its pure form is fairly soft, malleable and ductile.
• It is silvery white in colour and quite heavy
• Iron combines readily with oxygen to form iron oxide, which that is more commonly known as rust.
• For this reason iron is usually mixed with various forms of carbon and other alloying agents or impurities.
• Cast iron comes from furnace-poured iron into moulds, contains more than 2% carbon and some silicon
• Cast iron doesn’t have many aircraft applications due to low strength-to-weight ratio.
• Cast iron is in engines for items such as valve guides: its porosity and wear characteristics allow it to hold a lubricant film.
• Cast iron is also used in piston rings.

Steel

• Steel is a material composed primarily of iron.
• All types of steel contain carbon
• Many other alloying elements are used in most steel, but iron and carbon are the only elements found in all steel

Composition of Steel

• The difference between steel, cast iron and wrought iron is primarily based on the carbon content.

Identification of Steels

• The Society of Automotive Engineers (SAE) uses a four-numerical index system to represent chemical composition standards for steel specifications.
• The first digit identifies the principal alloying element
• The second digit indicates the percentage of the principal alloying element.
• The last two digits indicate the average carbon content in hundredths of a percent.

SAE Steel Numbering System

SAE designations for major classifications of steel

• 1xxx: Carbon Steels.
• Chromium-Vanadium Steels: 6xxx
• Nickel Steels: 2xxx.
• Nickel Chromium Molybdenum Steels: 8xxx.
• Nickel-Chromium Steels: 3xxx.
• Nickel Molybdenum Steels: also 4xxx
• Silicon Manganese Steels: 9xxx.
• Molybdenum Steels: 4xxx.
• Chromium Steels: 5xxx.
• Tungsten Steels: 7xxx

Alloying Agents in Steel

• Iron has few practical uses in its pure state.
• Adding small amounts of other materials to molten iron dramatically changes its properties.
• Common alloying agents include carbon, sulphur, silicon, phosphorous, nickel and chromium.

Carbon

• Carbon is the most common alloying element found in steel.
• Carbon in steel allows the steel to be heat-treated to obtain hardness, strength and toughness
• The higher the carbon content: the more receptive steel is to heat treatment, therefore higher the tensile strenght and hardness.
• Higher carbon content decreases the malleability and weldability of steel.
• A metal's hardness, or temper, is indicated by a letter designation that is separated from the alloy designation by a dash.

Ferrous materials classified according to carbon content:

• Low-carbon or mild steel is used in non-structural applications like steel-tube construction and is easily welded
• Medium-carbon steels accept heat treatment, are adaptable for machining or forging, and have surface hardness.is desired.
• High-carbon steels are very hard and primarily used in springs, files and some cutting tools.

Other Alloying Agents

• Silicon is a hardener that improves ductility
• Mangalloy(manganese steel) is a non-magnetic steel.
• It displays extreme anti-wear properties, and is abrasion resistant, achieves three times its surface hardness during conditions of impact.
• It does all this without any increase in brittleness.Sulphur:
• Sulphur must be removed during the refining process since it causes steel when rolled or forged to be brittle..
• If all sulphur cannot be removed: effects countered by adding manganese, which combines with sulphur to form manganese sulphide, which doesn’t harm the steel and eliminates oxides in the metal.
• Manganese also improves the forging characteristics by less-brittle rolling and forging temperatures
• Alloying additions of sulphur in small amounts improves the machinability of a steel.
• Machinability is the ease with which metal is cut (machined).
• Phosphorus improves low-carbon steels' resistance to atmospheric corrosion and raises the yield strenght of steel

Nickel

• Adding nickel increases its yield strength ,strength and hardness, slows hardening when is heat-treated, and results in a finer grain structure and reduces steel's tendency to warp or scale during the heat-treating process.

Chromium

• Chromium with steel increases strength/hardness as well as improves resistance to wear/corrosion.
• Chromium is used in balls and rollers of antifriction bearings.
• It can be electrolytically deposited on bearing journals and cylinder walls to provide wear-resistant surfaces.

Nickel-Chromium Steel

• Nickel toughens steel /chromium hardens steel, both elements alloyed gives steel desirable characteristics for use in high-strength structural applications!

Molybdenum

• Molybdenum is frequently used in structural steel for airframes since it reduces the grain size, increases the elastic limit/impact strength.
• Molybdenum steels are very wear-resistant and possess a great fatigue strength.
• Chrome-moly easily receives gas/electric arc weld machining and responds well to heat treatment.
• Chrome moly steel is commonly selected for gear structures / engine mounts.

Vanadium

• With chromium, vanadium produces strong hard steel alloy (chrome-vanadium steel).
• Ball bearings are made of chrome-vanadium steel

Tungsten

• Tungsten adds a extremely high melting point. Because tungsten steels have high density (high mass) and retain their hardness when operating temperatures elevate, control surface balance weights/breaker contacts in magnetos utilize tungsten.

Titanium

• Titanium steel alloys have very high tensile strength and toughness (esp. at high temperatures).
• It is lightweight, and has the capacity to deal with resisting corrosion under various conditions.

Stainless Steel

• Stainless steel contains lots of both chromium/nickel, classifying it as corrosion resistant steel.
• The strenght and corrosion resistant stainless steel is selected to work in high temperature firewalls/exhausts.

Heat Treatment of Steel

• Pure iron: unsuitable for structural material due to weakness, softness, and high ductility
• Steel (iron alloyed with carbon and elements) allows heat treatment, giving wide strengths/durability

Purpose of Steel Heat Treatment

• It is heating/cooling that results in changes of its mechanical/physical properties without its change in volume. As the carbon distribution control.

Heat treatment is associated with:

• Increasing strength as well as improve formability/machineability, or restore ductility.
• Heat may improve product performance by upping the strength with some traits

Steel Heat Treatment Processes

• Annealing: it cools and softens steel in the furnace in order to remove interior stress and involves the heating of and cooling of metal.
• Normalising: reduces stresses and involves uniform heating and cooling metals in the oven, it could lead to failure, its for welded parts.
• Hardening: makes carbon harder, carbon will display uniformly/the allows hardness depend
• Tempering: reduces the steel's quality of brittleness and is done by soak heating and air cooling. It not only reduces the hardness, also relieve stress helps with ductility as well toughness
• Case Harding: uses hard surfaces/core material bearings/gears. It’s best to have carbon alloy’s/low alloys its will penetrate cores hardness if case is made steel in high carbon

Aircraft Materials - Non-Ferrous (6.2.1)

• The content covers the characteristics and properties of common non-ferrous materials used in aircraft, identification of common non-ferrous materials, heat treatment of non-ferrous materials and application of non-ferrous materials

Properties of Non-Ferrous Metals

• Non-ferrous metal: metals base that elements have iron than
• Comonly used - titanium, magnesium and aluminium to aircraft construction/repair.

Pure aluminum lacks sufficient strength to be used for aircraft construction

• Alloyed it up - mixed better with other metals (copper/zinc/resultant alloy like strong,weight light resistance)
• Aluminum - by major alloying ingredient

Elements for aluminum alloying as follows:

• magnesium
• copper
• zinc
• manganese

Classes of aluminium are two main

• ingot rolling or specified shapes extruding.
• mold pouring liquid /cooling is when cast aluminum alloys from

Wrought Aluminium Alloys Designation System

• Four-digit index system is when identify aluminum wrought allots
• Alloy Series - Principal Element
• Aluminum 99.00 % minimum :1xxx
• Copper: 2xxx
• Silicon: 4xxx
• Magnesium :5xxx
• Manganese & Silicon: 6xxx
• Zinc 7xxx

Aluminium four-digit number system

• The 1xxx series includes the only exception to the wrought alloy designation .

The first digit means aluminum 99% minimum.

Modifications to impurities are the second indicator of the limit. eg (1000) The second number does not mean unique limit control occurs, but only indicate particular percentage/ individual contaminates control exists

TwoXXX Through 9xxx Series

The numbers indicated are digit first

• Alloy modifications are second indicators.

When Assigned:

1/9 Consecutive

• Have only certain significance because group numbers of identifiers serve - but are not unique to

No such significance over digits

• Only serve unique ID within the group

Alloying table element:

• Mn:3XXX
• Zinc 7xxx
• Other 8xxx
• Copper: 2xxx
• Mg 5xxx
• Silicone 4xxx

Aluminum And Alloy's

• 1xxx Pure Alloys have
• Strain hardenable features
• Electrical Conductivity
• High form / resistive corrode
• Chemical Electric Application!
• 2xxx uses cooper when Series alloys have agents alloying of principles, but causes problems when heat properly the treat!
• skins and rivets structure (aircraft) can 2024/2017 the commonly use!

The 4xxx Series

• aluminum is with lower silicone temperature then aluminum/ silicon will well work from brazing with welding!
• 5xxx makes good resistive corrosion as when high cold works has increased temperature from magnesium

Aluminum & silicon then produces:

• with having stringth that carriers the corrosion resistance with good forming and corrosion properties (6xxx Series designation)

For parts requires less farming Aluminum alloys then:

• They addition of zinc, so are stronger when they're harder (series 7xxx aluminum allots makes alloys) /7075 & 7178 used form zinc aluminum
• Windows /bulkheads = 7079!
• Upper skins beam,longers bars =7178 with copper mix

High Elastic and strenght

• 8xxx increases in component weight (high strenght + stiffness); provides less applications space
• Aluminium 8xxx alloys - 8090 Al-Li Alloy fractured faces

Aluminium (Clad) Alloy:

• Aircraft made from Alclad aluminum the exteriros parts /heat treated sheets allots Aluminum to construction, resistive corrosion Aluminum alloys will better

Sheet will

• Scratches abrasion must protect from corrosion
• Alots must stress
• Potential abrasion may come in that point

Aluminium (Heat Treat)

• state their their metals,heating treat/ Cooling involve/ makes serve useful
• treat metals can resistance affect or make easier/strong

But (some property is high) the brittle results of metals/ heating operation can product all these

• Treat 2 is used over solution/precip

Aluminium Heat Treat (solution)

Heating makes more aluminum certain alloy allow the base metal by MIXING.

• heat to keep just the best temperature through element uniform alloy If takes cooling soon in time.
• Aluminum allow metal alloy is to precipitate (alloy grains become suspension by the in Aluminum /this stop, weakened)
• minimize water for alloy/Aluminum baths with appropriate cooling.

Aluminium (Sheet) Warps & Hardens

• Must keep salt residue (sodium potassium nitrates) - that leads rinses from alloys if alloy's lead corrodes
• Heat alloy allows & Treat

Aluminium (Heat Precip):

• Aluminum alloy’s will soften or quench! While metal hardness has strength when more allowed of temp for longer /Natural to alloys can several take for alloy to improve when age

Aluminum alloy

• Sub subtime or aging short-lengthen/ temperature the processes can slowly time/temp reheat rate with time is quick!
• Artificial aging (precip) - corrosion develops resistance by the structure of metal-locking

Aluminum Alloy That Aging are Called

• Highzinc-mag zinc those requires.
• Those heat is treatment what needs then require-fully thermal treatment strength developed.

Aluminum (Temper Alloy)

Where designated of T the alloy hard by commonly have commonly number the more The Number T:

• So Heat / Strain is treated
• T3 - Solved, then 5% thickness down to aged fabric:

Solved heat-Stable: T4 is alloy can get artificial treated from after casting

Aluminum Reheat

• Those that treats and be the alloy can rivet 2024 alloy or really hard/repeated often solution treated to enough drive! The materials allow more of the clad over these limited treatments and no 3 more from treating/lowers over resistance of corrode.

Non (Heat Treat)

• usually alloy are for 5xxx, 1000/ proper cold work treat. Heat Aluminum pure doesn't help because there are no allow to structure

Strain Treat

• It (Cold/ non heat aluminum will improve working + working well
• Mechanically, critical ranges hardens and grain alter the structure, consist pressing drawings

Hard (Appropriate)

• or after are tensile have treated alloy
• rolled, the no one hand non treat-on however, all much part - for designate letters temper

If Designation then separate

• Basic more one has defined the if is-numbers
• Then digits then of: H1, H 2 and H3 /the number 8 is the tensile the example (fully - H38 has stable/hard)

Many Aluminum Alloys.

• Magnesium with form their are alloy with one light the aluminum weight but with some to structures working
• Aluminum Magnesium - used core use wheels

To that corrosion and oxygen of drawbracks

• Surfaces can oxide chemical /exclude form. cracking and heated such is form
• Then small

In grind should burn and be

• Dry other /machine dust magnesium exercise if occurs the fire if the fire happens but surfaces then cool aluminum