Based on our vast experience with EASA PART 66 examination questions and question databanks, we have prepared a practice example of questions with explanations to practice for your next exam.
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Module 6: Materials and hardware
Which case hardening technique is most appropriate for a low carbon steel component?
- A. Flame or induction hardening
- B. Pack or gas carburising
- C. Nitriding
Correct Answer: B. Pack or gas carburising
Explanation: Low carbon steel does not have enough carbon to harden on its own. Carburising is a process where carbon is added to the surface layer (the case), which can then be hardened by quenching. The core remains tough and ductile.
What is the term for the internal stresses that remain within a material after all manufacturing and heat treatment processes are finished?
- A. Residual stress
- B. Working stress
- C. Applied stress
Correct Answer: A. Residual stress
Explanation: Residual stresses are stresses that are locked in to a material or component even when it is not subjected to any external forces. They are a result of manufacturing processes like casting, welding, and heat treatment.
What is the principal reason for tempering a component made of hardened steel?
- A. To significantly reduce brittleness without a major loss of strength
- B. To retain core hardness but soften the surface
- C. To retain surface hardness but soften the core
Correct Answer: A. To significantly reduce brittleness without a major loss of strength
Explanation: Hardening makes steel very strong but also very brittle. Tempering is a secondary heat treatment that reduces this brittleness and increases the material’s toughness, with only a slight decrease in hardness.
For High Speed Steel (HSS) to maintain its cutting ability at high temperatures (e.g., a dull red colour), which alloying element is crucial?
- A. Nickel
- B. Tungsten
- C. Vanadium
Correct Answer: B. Tungsten
Explanation: Tungsten is the key alloying element in High Speed Steel. It forms very hard carbides and helps the steel retain its hardness and cutting edge even at the high temperatures generated during machining operations.
If a low carbon steel bolt is stretched past its elastic limit but does not fracture, what is the result?
- A. It will deform permanently
- B. It will deform temporarily
- C. It will become more ductile
Correct Answer: A. It will deform permanently
Explanation: The elastic limit is the point beyond which a material will no longer return to its original shape after a load is removed. Any deformation beyond this point is permanent, a characteristic known as plastic deformation.
How can fatigue failure be best described?
- A. A reduction in strength due to alternating loads
- B. Failure due to a sudden impact
- C. Failure caused by stress exceeding the material’s Ultimate Tensile Strength (U.T.S.)
Correct Answer: A. A reduction in strength due to alternating loads
Explanation: Fatigue failure is the progressive structural damage that occurs when a material is subjected to repeated or fluctuating (cyclic) loads, even at stress levels much lower than its ultimate tensile strength.
What is the primary outcome of normalising a steel component?
- A. It relieves internal stresses
- B. It increases toughness
- C. It increases hardness
Correct Answer: B. It increases toughness
Explanation: Normalising is a heat treatment process that refines the grain structure of the steel. This results in a material with increased toughness and ductility compared to its as-cast or as-forged state.
Which of these descriptions best fits the properties of cast iron?
- A. Very malleable
- B. Heavy and brittle
- C. Tough
Correct Answer: B. Heavy and brittle
Explanation: Cast iron has a high carbon content, which makes it very hard and compressive-strong but also brittle, meaning it is prone to fracturing without significant plastic deformation.
In the steel production process, what element is primarily removed from molten pig iron by blowing air or oxygen through it?
- A. Oxides
- B. Sulphur
- C. Carbon
Correct Answer: C. Carbon
Explanation: The process of refining pig iron into steel involves lowering its high carbon content to a specific percentage. This is achieved by introducing oxygen, which combines with the excess carbon and is removed as a gas.
For aircraft hydraulic systems that require a flared tube, a two-piece connector (sleeve and nut) is used. What problem does this design prevent?
- A. The possibility of reducing the flare thickness by wiping or ironing during tightening
- B. Wrench damage to the tubing during the tightening process
- C. The need for a flaring operation before assembly
Correct Answer: A. The possibility of reducing the flare thickness by wiping or ironing during tightening
Explanation: The sleeve in this type of connector supports the flare. As the nut is tightened, it pushes the sleeve and flare squarely into the fitting, preventing the flare from being thinned out, wiped, or ironed, which would weaken the connection.
What occurs during a tensile strength test of a material sample?
- A. The material is pulled until it breaks
- B. The material is pulled to the limit of its elasticity
- C. The material is pulled until it reaches its UTS
Correct Answer: A. The material is pulled until it breaks
Explanation: A tensile test involves applying a pulling (tensile) force to a sample until it fractures. The test measures the material’s response to this force, including its ultimate tensile strength (UTS) and ductility.
How soon after undergoing solution treatment can an aluminium alloy component be put into service?
- A. After 24 hours
- B. Straight away
- C. After approximately 5 days
Correct Answer: C. After approximately 5 days
Explanation: After solution treatment and quenching, aluminium alloys undergo a natural ageing process (precipitation hardening) at room temperature. They gain strength over time and typically require about four to five days to reach their fully hardened condition.
What is the maximum allowable time between removing an aluminium alloy part from a heat treatment furnace and quenching it?
- A. 10 seconds
- B. 3 seconds
- C. 7 seconds
Correct Answer: A. 10 seconds
Explanation: This time, known as the quench delay, must be extremely short. A maximum of 10 seconds is typically allowed to prevent the alloying elements from precipitating out of solution prematurely, which would prevent the material from achieving its full strength after ageing.
During the buffing of an aluminium alloy surface, what layer is being taken off?
- A. Aluminium
- B. The oxide layer
- C. The alloy
Correct Answer: B. The oxide layer
Explanation: Buffing is a finishing process that removes the thin, naturally occurring layer of aluminium oxide from the surface, revealing the shiny, unoxidized metal underneath.
How can magnesium alloys used in aviation typically be identified visually?
- A. By the yellowish surface from a protective treatment
- B. By a shiny, chromium-plated surface
- C. By a silver surface due to a protective coating
Correct Answer: A. By the yellowish surface from a protective treatment
Explanation: Magnesium is highly susceptible to corrosion. To protect it, a chemical conversion coating (chromating) is applied, which typically gives the surface a yellowish or golden hue.
How is ‘Alclad’ best described?
- A. Duralumin with a pure aluminium coating
- B. Aluminium with a duralumin cladding
- C. Duralumin with a magnesium cladding
Correct Answer: A. Duralumin with a pure aluminium coating
Explanation: Alclad is a composite material consisting of a high-strength aluminium alloy core (like Duralumin) with a thin layer of pure, corrosion-resistant aluminium metallurgically bonded to its surfaces.
The process of bonding a layer of pure aluminium onto the surface of an aluminium alloy is known as?
- A. Cladding
- B. Metalizing
- C. Electroplating
Correct Answer: A. Cladding
Explanation: Cladding is the process of bonding together dissimilar metals. In the case of Alclad, it refers to pressure-rolling a sheet of pure aluminium onto an alloy sheet to enhance corrosion resistance.
Which definition accurately describes the property of brittleness?
- A. The property of a material to fracture without significant deformation
- B. The property to resist deformation
- C. The property to resist wear
Correct Answer: A. The property of a material to fracture without significant deformation
Explanation: Brittleness is the opposite of ductility. A brittle material, when subjected to stress, will break or crack with little to no prior plastic deformation.
The proof stress of a material corresponds to the stress at which…?
- A. a small amount of permanent set takes place
- B. the material yields
- C. necking of the material begins
Correct Answer: A. a small amount of permanent set takes place
Explanation: Proof stress is the stress level at which a material undergoes a specified, small amount of permanent (plastic) deformation, typically 0.2%. It is often used as an approximation of the elastic limit for materials that do not have a clearly defined yield point.
How is the value of stress in a material calculated?
- A. Load / Cross-sectional area
- B. Load * Cross-sectional area
- C. Cross-sectional area / Load
Correct Answer: A. Load / Cross-sectional area
Explanation: Stress (σ) is a measure of the internal forces within a material. It is defined as the force (or load) applied per unit of the material’s cross-sectional area. The formula is σ = F/A.
