Aircraft Materials, Hardware, and Processes — FAA A&P Test Questions (ACS AM.I.E)
Aircraft Materials, Hardware, and Processes is the largest subject area on the General written, and it is the one that decides most pass and fail results. It runs from bolt grip length and safety wire direction through torque wrench extension math, aluminum alloy and temper designations, heat treatment, corrosion, and nondestructive inspection. The breadth is the difficulty: no single concept is hard, but there are dozens of small facts and the FAA samples them heavily. Work this area in blocks by hardware, materials, and processes rather than trying to absorb it in one pass.
Written by the AMTprep editorial team · Published · Last reviewed
Written against the FAA primary sources cited at the foot of this page.
What ACS AM.I.E covers
Hardware is the first block and the largest. Expect bolts and their part numbering and head markings, grip length chosen so the plain shank rather than the threads carries shear load, nuts including castellated nuts locked with a cotter pin and self-locking nuts that are not used where the nut or bolt rotates, washers, screws, rivets, pins, and turnlock fasteners. Safetying is tested hard: the double-twist safety wire method must be routed so the wire's pull tends to tighten each fastener, and cotter pin installation follows the same positive-locking logic. Precision measurement and torque sit alongside it, including the extension formula that turns a specified torque at the fastener into a different reading on the wrench dial. Materials is the second block: ferrous and nonferrous alloys, the four-digit aluminum designation whose first digit names the principal alloying element, temper suffixes such as T3, T4 and T6 that record heat treatment and working, plus composites, plastics and transparencies. Processes is the third: heat treatment, annealing, solution heat treatment and aging, case hardening, corrosion identification and treatment, and nondestructive inspection by dye penetrant, magnetic particle, eddy current, ultrasonic and radiographic methods. FAA-H-8083-30 covers all three blocks, and its hardware and materials chapters are where the exact wording of these answers comes from. Because the work here is performed under 14 CFR Part 43, questions often frame a fact as a decision about whether a part is serviceable.
Where this sits on the test
ACS AM.I.E is tested on the FAA General written test, one of 1,553 ACS-tagged questions in the General bank. Every question tagged to this area carries a worked rationale and its FAA handbook reference, so you can drill the code itself rather than the whole test.
FAA handbook references
- FAA-H-8083-30
Three traps candidates fall into
- The torque extension correction gets applied backwards. With 50 inch-pounds specified, an 8-inch wrench and a 2-inch extension in line, you set the wrench to 50 times 8 divided by 10, or 40 inch-pounds. Dialing the full 50 instead puts roughly 62 inch-pounds into the fastener and overtorques it.
- The alloy number and the temper answer different questions. In 2024-T3 the first digit names the principal alloying element, copper, while T3 describes the heat treatment and cold working the metal received. Candidates asked for the temper quote the alloy family, and candidates asked for the alloy quote the T number.
- Grip length is chosen so the plain shank, not the threads, carries the shear load. Candidates treat a longer bolt as the safer bolt and stack washers to take up the difference. Once threads sit in the shear plane, the joint's strength is set by the smaller root diameter and the thread roots concentrate stress.
50 free sample questions from ACS AM.I.E
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When installing a standard AN bolt with a self-locking nut in a joint subject to tension loads, what is the proper thread engagement requirement?
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Answer: At least one thread of the bolt must extend beyond the nut.
Why: FAA guidance requires that a bolt of correct length show at least one thread (including the chamfer) extending past the nut after tightening. A bolt threaded flush or short of the nut may not be fully engaged, and stating 'three threads inside the nut' does not address the visible-thread inspection standard used to verify correct grip length.· FAA-H-8083-30 — Aircraft Hardware (bolt installation and grip length)
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Why should the threaded portion of a bolt, rather than the grip, never bear the shear load in a joint?
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Answer: Threads concentrate stress and reduce the effective cross-sectional area in shear.
Why: A bolt's grip is the smooth, full-diameter shank designed to carry shear. The threaded section has a smaller root diameter and the thread roots act as stress risers, so loading threads in shear weakens the joint. Threads are not specially case-hardened to brittleness, and the nut does not carry the joint's shear load.· FAA-H-8083-30 — Aircraft Hardware (bolt grip length and shear loading)
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What is the primary purpose of using a cotter pin with a castellated (castle) nut on a bolt?
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Answer: To prevent the nut from rotating off the bolt.
Why: A cotter pin passes through the slots of a castellated nut and a hole in the bolt to positively lock the nut against rotation. It is a mechanical safety device, not a means of adding clamping force or sealing threads; the torque on the nut establishes clamp load.· FAA-H-8083-30 — Aircraft Hardware (nuts and safetying)
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When using the double-twist method to safety wire two bolts together, in which direction must the wire be installed relative to each bolt?
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Answer: So that loosening of either bolt tightens the wire.
Why: Safety wire must be routed so that any tendency of a bolt to loosen puts tension on the wire, pulling the adjacent bolt tight. Running the wire over the heads or around the grip does not oppose the loosening rotation and would not perform the safetying function.· FAA-H-8083-30 — Aircraft Hardware (safety wiring methods)
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What is the standard temper designation for aluminum alloy that has been solution heat-treated and then artificially aged?
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Answer: T6
Why: The -T6 temper designates aluminum that is solution heat-treated and then artificially aged. The -T3 temper is solution heat-treated, cold worked, and naturally aged, while -O designates the annealed condition. These designations follow the standard aluminum temper system in the handbook.· FAA-H-8083-30 — Aircraft Materials (aluminum alloy temper designations)
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In the four-digit aluminum alloy designation 2024, what does the first digit indicate?
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Answer: The principal alloying element of the alloy.
Why: In the four-digit wrought aluminum system, the first digit identifies the principal alloying element group; for 2024 the leading 2 indicates copper as the major alloying element. The first digit is not a percentage, and temper is shown separately by a dash and letter/number suffix.· FAA-H-8083-30 — Aircraft Materials (aluminum alloy numbering system)
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What is the principal advantage of using a torque wrench when installing a nut and bolt?
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Answer: It applies a specified, uniform tension to the fastener.
Why: A torque wrench is used to develop a specified, repeatable clamping tension by measuring the torque applied, preventing both under- and over-tightening. Proper torque alone does not lock the nut, so safetying is still required, and torquing does not by itself prevent all loosening.· FAA-H-8083-30 — Aircraft Hardware (torque and torque wrenches)
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The specified torque for a fastener is 50 inch-pounds, but a 2-inch extension must be added in line with an 8-inch torque wrench to reach the bolt. What reading on the wrench will produce the specified torque at the bolt?
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Answer: 40 inch-pounds.
Why: When an extension is added in line with the wrench handle, the effective lever lengthens and the wrench scale under-reads the true fastener torque. The wrench reading equals desired torque times wrench length divided by (wrench + extension) length: 50 x 8 / (8 + 2) = 40 inch-pounds at the wrench to achieve 50 inch-pounds at the bolt.· FAA-H-8083-30 — Aircraft Materials, Hardware, and Processes
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Which of the following composite reinforcing fibers is most susceptible to the absorption of moisture?
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Answer: Aramid (Kevlar)
Why: Aramid (Kevlar) fiber readily absorbs moisture, which can degrade the resin bond and reduce strength, so aramid laminates must be carefully dried before repair. Glass and carbon fibers do not absorb water the same way. See FAA-H-8083-30, Aircraft Materials, Hardware, and Processes, on composite materials.· FAA-H-8083-30 — Aircraft Materials, Hardware, and Processes
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When drilling stainless steel, the technician should use a
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Answer: drill ground to 120 degrees with a slow cutting speed.
Why: Stainless steel work-hardens rapidly and conducts heat poorly, so a slow cutting speed with firm, continuous feed prevents glazing and overheating. A more obtuse 120-degree point reduces cutting load and helps the lip bite before the surface hardens. A fast speed or a sharper 90-degree point would generate heat that hardens the metal ahead of the drill. See FAA-H-8083-30, Aircraft Materials, Hardware, and Processes.· FAA-H-8083-30 — Aircraft Materials, Hardware, and Processes
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How is a material galvanized?
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Answer: It is dipped in a bath of molten zinc.
Why: Galvanizing applies a sacrificial zinc coating; the classic hot-dip process immerses cleaned steel in a bath of molten zinc that bonds to the surface and protects the steel by acting anodically. Heating in zinc dust is a different process, and spraying nickel is a separate plating method. See FAA-H-8083-30, Aircraft Materials, Hardware, and Processes.· FAA-H-8083-30 — Aircraft Materials, Hardware, and Processes
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At what temperature range is steel tempered?
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Answer: Below the annealing temperature.
Why: Tempering is a low-temperature reheat applied to already-hardened steel to relieve quenching stresses and trade a little hardness for greatly improved toughness. It is carried out below the lower critical (annealing) temperature so the structure is not re-transformed. Heating to or above the annealing temperature would soften the steel. See FAA-H-8083-30, Aircraft Materials, Hardware, and Processes.· FAA-H-8083-30 — Aircraft Materials, Hardware, and Processes
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The addition of chromium to steel produces increased
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Answer: hardness.
Why: Chromium is a strong carbide-former, so adding it to steel raises hardness and wear resistance (and corrosion resistance at higher percentages). It does not improve ductility, and toughness is not its primary contribution. This is why chromium steels are favored for hard, wear-resistant components. See FAA-H-8083-30, Aircraft Materials, Hardware, and Processes.· FAA-H-8083-30 — Aircraft Materials, Hardware, and Processes
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Chromium added to plain carbon steel
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Answer: increases its resistance to corrosion.
Why: Chromium added to plain carbon steel forms a thin, self-healing oxide film that greatly increases resistance to corrosion, which is the basis of stainless steel. It remains a ferrous alloy because iron is still the major element, and it makes the steel harder rather than softer. See FAA-H-8083-30, Aircraft Materials, Hardware, and Processes.· FAA-H-8083-30 — Aircraft Materials, Hardware, and Processes
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The purpose of case hardening is to
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Answer: produce a hard case over a tough core.
Why: Case hardening is used where a component needs a hard, wear-resistant surface but a tough, shock-absorbing interior. Carbon is diffused into the surface of a low-carbon steel so the case can be hardened while the low-carbon core stays tough. It therefore adds carbon to the surface rather than removing it. See FAA-H-8083-30, Aircraft Materials, Hardware, and Processes.· FAA-H-8083-30 — Aircraft Materials, Hardware, and Processes
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At normal temperatures, high-carbon steel is harder than low-carbon steel because
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Answer: of the higher percentage of carbon in the steel.
Why: The hardness obtainable in plain carbon steel rises with its carbon content, because carbon allows hard constituents such as cementite and martensite to form. A high-carbon steel is therefore harder than a low-carbon one. Retained austenite actually lowers hardness, so it is not the reason. See FAA-H-8083-30, Aircraft Materials, Hardware, and Processes.· FAA-H-8083-30 — Aircraft Materials, Hardware, and Processes
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Nitriding is a form of
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Answer: case hardening.
Why: Nitriding is a case-hardening process in which nitrogen is diffused into the surface of a suitable alloy steel to form hard nitrides, giving a very hard, wear-resistant skin without a final quench. It is not tempering (a stress-relieving reheat) nor anodizing (an electro-chemical oxide treatment for aluminum). See FAA-H-8083-30, Aircraft Materials, Hardware, and Processes.· FAA-H-8083-30 — Aircraft Materials, Hardware, and Processes
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Medium-carbon steel has a carbon content of approximately
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Answer: 0.3 to 0.5 percent.
Why: Plain carbon steels are graded by carbon content: low (mild) up to about 0.3 percent, medium roughly 0.3 to 0.5 percent, and high carbon above about 0.5 percent. Medium-carbon steel therefore falls in the 0.3 to 0.5 percent band, offering a balance of strength and toughness. See FAA-H-8083-30, Aircraft Materials, Hardware, and Processes.· FAA-H-8083-30 — Aircraft Materials, Hardware, and Processes
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A ferrous metal contains
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Answer: iron.
Why: By definition a ferrous metal is one in which iron is the principal element, the word ferrous deriving from ferrum (iron). Aluminum and magnesium are the basis of non-ferrous light alloys and contain no iron. This is the fundamental division between ferrous and non-ferrous metals. See FAA-H-8083-30, Aircraft Materials, Hardware, and Processes.· FAA-H-8083-30 — Aircraft Materials, Hardware, and Processes
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With respect to ferrous metals, which of the following is true?
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Answer: Iron is a main element, and most ferrous metals are magnetic.
Why: Ferrous metals have iron as their main constituent, and because iron is ferromagnetic most ferrous metals are magnetic, which is a useful quick identification check. The exception is austenitic stainless steel, which is non-magnetic, so the statement is correctly qualified as most rather than all. See FAA-H-8083-30, Aircraft Materials, Hardware, and Processes.· FAA-H-8083-30 — Aircraft Materials, Hardware, and Processes
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The annealing of steel is sometimes required because it
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Answer: relieves internal stress caused by engineering processes.
Why: Annealing heats steel and cools it very slowly to soften it, refine the grain, and relieve internal stresses introduced by machining, forming, or welding. It does not increase load-carrying capacity or form a corrosion-resistant layer; if anything it lowers strength while improving ductility and workability. See FAA-H-8083-30, Aircraft Materials, Hardware, and Processes.· FAA-H-8083-30 — Aircraft Materials, Hardware, and Processes
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On the Brinell hardness scale, a hardened cobalt tool or high-speed steel would have a Brinell hardness number (BHN) in approximately what range?
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Answer: 600 to 700 BHN
Why: Cobalt is used in very hard tool and high-speed steels, which sit high on the Brinell scale, in the region of 600 to 700 BHN. This is far above soft annealed steels (roughly 100 to 175 BHN). The lower ranges correspond to mild or medium carbon steels rather than a hardened cobalt tool steel.· FAA-H-8083-30 — Aircraft Materials, Hardware, and Processes
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If a metal component is found to be in the tertiary (third) stage of creep, what is the correct action?
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Answer: Replace the component immediately
Why: Creep occurs in three stages, and the tertiary stage is one of rapidly accelerating, irreversible strain that leads quickly to rupture. Crack-arrest or condition-monitoring measures are inadequate once tertiary creep is reached, so the only safe action is to remove and replace the component immediately before it fails.· FAA-H-8083-30 — Aircraft Materials, Hardware, and Processes
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Phosphate conversion coating of steel is produced by immersing the steel in a solution of
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Answer: phosphoric acid and metal phosphates
Why: Phosphating produces a corrosion-inhibiting, paint-keying conversion coating by immersing the steel in a solution of phosphoric acid and metal phosphates, which react with the surface to form an integral phosphate layer. Nitric and sulfuric acid baths are used for other treatments such as pickling and are not the phosphating solution.· FAA-H-8083-30 — Aircraft Materials, Hardware, and Processes
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Tempering of a hardened steel involves
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Answer: reheating below the critical point and cooling slowly
Why: Tempering reheats hardened steel to a temperature below the critical point, holds it, then cools it slowly to relieve quench stresses and reduce brittleness. Because the steel stays below the critical point, it is not re-austenitized. Heating above the critical point would be a hardening or normalizing operation, not tempering.· FAA-H-8083-30 — Aircraft Materials, Hardware, and Processes
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Austenitic stainless steels are best described as
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Answer: essentially non-magnetic
Why: Austenitic stainless steels retain a face-centered-cubic austenite structure at room temperature, which makes them essentially non-magnetic. That same structure means they cannot be hardened by conventional heat treatment and are strengthened only by cold working. Their non-magnetic response distinguishes them from ferritic and martensitic stainless grades.· FAA-H-8083-30 — Aircraft Materials, Hardware, and Processes
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The desirable properties of normal carbon steel depend largely on the transformation, during slow cooling, of
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Answer: austenite into pearlite
Why: When carbon steel is heated it becomes austenite, and on slow cooling that austenite transforms into pearlite, the layered ferrite-cementite structure that gives normal carbon steel its properties. The reverse change, pearlite to austenite, occurs only on heating, not cooling.· FAA-H-8083-30 — Aircraft Materials, Hardware, and Processes
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What is the principal difference between annealing and normalizing of steel?
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Answer: Both are heated above the critical temperature; annealing cools slowly in the furnace while normalizing cools in still air
Why: Both annealing and normalizing start by heating above the upper critical temperature to form austenite; the difference is the cooling rate. Annealing cools very slowly in the furnace to give the softest, most ductile result, while normalizing cools in still air, giving a slightly harder, finer-grained, stress-relieved structure.· FAA-H-8083-30 — Aircraft Materials, Hardware, and Processes
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Normalizing of steel is performed primarily to
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Answer: relieve the residual stresses left by manufacturing processes
Why: Normalizing reheats steel above its upper critical point and air-cools it to refine the grain and relieve the residual stresses left by forging, rolling, or machining, producing a uniform structure. It is not primarily a softening process like full annealing, and heat treatment cannot restore fatigue life already consumed.· FAA-H-8083-30 — Aircraft Materials, Hardware, and Processes
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During the normalizing process, after heating above the upper critical point the steel is
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Answer: allowed to cool in still air at room temperature
Why: Normalizing is defined by cooling in still air at room temperature after heating above the upper critical point, which is faster than furnace annealing but slower than a quench. Immediate quenching would harden the steel, and very slow furnace cooling would be annealing, so still-air cooling is what makes the process normalizing.· FAA-H-8083-30 — Aircraft Materials, Hardware, and Processes
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Cast iron is best characterized as a material that is
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Answer: heavy and brittle
Why: Cast iron has a high carbon content, much of it as graphite flakes, which makes it heavy and brittle with little ability to deform before fracture. It is therefore good in compression but poor under tension or shock. Because it is neither tough nor malleable, it is not used for highly stressed aircraft structure.· FAA-H-8083-30 — Aircraft Materials, Hardware, and Processes
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Exhaust systems are commonly made from stainless steel, which when held at high temperature is susceptible to
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Answer: intergranular corrosion
Why: When austenitic stainless steel is held in a high-temperature range, as around exhaust systems and welds, chromium combines with carbon at the grain boundaries (sensitization), leaving those boundaries depleted of chromium and prone to intergranular corrosion. Filiform and general surface corrosion are more typical of coated or aluminum surfaces rather than this grain-boundary attack.· FAA-H-8083-30 — Aircraft Materials, Hardware, and Processes
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In the heat treatment of steel, tempering is performed
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Answer: after the hardening operation
Why: Tempering is always performed after hardening, because its purpose is to relieve the stresses and reduce the brittleness left by the quench while retaining most of the gained hardness. Carried out before hardening it would have no effect, and it reduces rather than increases hardness, so it is not used to increase hardness.· FAA-H-8083-30 — Aircraft Materials, Hardware, and Processes
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If a steel component is operated below its fatigue (endurance) limit, the fatigue life is
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Answer: theoretically infinite
Why: Steels exhibit a true fatigue (endurance) limit: if the cyclic stress stays below this limit, the material can theoretically endure an unlimited number of cycles, giving an effectively infinite fatigue life. Above the limit the life becomes finite and falls sharply as stress rises. The fatigue limit, not the proof stress, governs this behavior.· FAA-H-8083-30 — Aircraft Materials, Hardware, and Processes
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A low-carbon steel that does not contain enough carbon to harden directly would normally be case hardened using
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Answer: pack or gas carburizing
Why: A low-carbon steel lacks the carbon needed to harden, so its surface is first enriched with carbon by pack or gas carburizing before quenching, giving a hard case over a tough core. Nitriding suits special alloy steels, and flame or induction hardening requires a steel that already has enough carbon to respond to localized heating.· FAA-H-8083-30 — Aircraft Materials, Hardware, and Processes
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The stress that remains locked within a component after manufacture and all heat treatment, with no external load applied, is called
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Answer: residual stress
Why: Stress that remains within a component after manufacture and all heat treatment, with no external load applied, is termed residual stress. Working or applied stress, by contrast, exists only while the part is actually carrying a load in service. Excessive residual stress is undesirable, which is why stress-relieving treatments are used.· FAA-H-8083-30 — Aircraft Materials, Hardware, and Processes
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Annealing of steel is performed primarily to
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Answer: make the metal malleable and easier to work.
Why: Annealing softens steel and increases its ductility and malleability, relieving internal stresses so the metal is easier to form and machine. It does not increase strength or toughness, and it does not make the metal brittle; brittleness is associated with hardening.· FAA-H-8083-30 — Aircraft Materials, Hardware, and Processes
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Tempering of hardened steel is performed to
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Answer: significantly reduce brittleness without a major loss of strength.
Why: Tempering reheats fully hardened steel to a moderate temperature so it loses much of its excessive brittleness while retaining most of its strength and hardness, producing a usable balance of properties throughout the section rather than selectively in the core or surface.· FAA-H-8083-30 — Aircraft Materials, Hardware, and Processes
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High-speed steel relies chiefly on which alloying element for its ability to cut other metals even when heated to a dull red color?
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Answer: Tungsten.
Why: High-speed steel owes its red-hardness — the ability to hold a cutting edge even when heated to a dull red — mainly to tungsten, which forms stable carbides that resist softening at high temperature. Nickel adds toughness and vanadium is a secondary carbide-former, so tungsten is the key element.· FAA-H-8083-30 — Aircraft Materials, Hardware, and Processes
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When a low-carbon steel bolt is stretched beyond its elastic limit without breaking, it will
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Answer: deform permanently.
Why: The elastic limit marks the boundary of recoverable deformation. Once a low-carbon steel bolt is stretched beyond it, the strain becomes plastic and the bolt deforms permanently rather than springing back; such a bolt must be replaced. It does not recover its length, nor does stretching make it more ductile.· FAA-H-8083-30 — Aircraft Materials, Hardware, and Processes
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Fatigue failure of a metal is best defined as
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Answer: a reduction in strength caused by repeated or alternating loads.
Why: Fatigue is the progressive weakening and eventual cracking of a material under repeated or alternating loads, even when each load is well below the ultimate tensile strength. It is therefore best defined as a reduction in strength caused by cyclic loading, distinct from a single overload or a one-time impact fracture.· FAA-H-8083-30 — Aircraft Materials, Hardware, and Processes
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Cast iron is best described as
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Answer: heavy and brittle.
Why: Cast iron contains a high proportion of carbon, largely as graphite flakes, making it heavy and brittle with very little ductility, so it fractures rather than bends under shock or tension. It is strong in compression but is neither tough nor malleable.· FAA-H-8083-30 — Aircraft Materials, Hardware, and Processes
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Steel is produced by refining pig iron, blowing air or oxygen through the molten material primarily to remove excess
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Answer: carbon.
Why: Pig iron from the blast furnace has too much carbon to be useful, so steelmaking refines it by blowing air or oxygen through the molten metal to oxidize and remove the excess carbon to the required level. Controlling final carbon content in this way converts brittle pig iron into steel.· FAA-H-8083-30 — Aircraft Materials, Hardware, and Processes
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In a tensile strength test, the specimen is
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Answer: pulled in tension until it breaks.
Why: A tensile strength test loads a specimen in tension and continues to pull it until it fractures, recording load and extension all the way to failure. This allows properties such as ultimate tensile strength and elongation at fracture to be determined; stopping at the elastic limit or at the UTS would not produce the complete curve to rupture.· FAA-H-8083-30 — Aircraft Materials, Hardware, and Processes
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An impact test, such as the Izod or Charpy test, is used to measure a material's
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Answer: toughness.
Why: Impact tests such as Izod and Charpy measure the energy a material absorbs in fracturing under a sudden blow, a direct measure of its toughness — the ability to resist shock without breaking. Hardness and ductility are assessed by separate tests (indentation and elongation) and are not what an impact test quantifies.· FAA-H-8083-30 — Aircraft Materials, Hardware, and Processes
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The Charpy test is used to measure a material's
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Answer: impact energy.
Why: The Charpy test is an impact test: a weighted pendulum strikes a notched specimen and the energy absorbed in fracturing it is read from the swing. That absorbed impact energy measures the material's toughness, or resistance to shock loading. Strain and the modulus of elasticity are obtained from a tensile test, not an impact test.· FAA-H-8083-30 — Aircraft Materials, Hardware, and Processes
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For most steels, the fatigue (endurance) limit is generally in the region of which percentage of the static ultimate tensile strength?
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Answer: 40 to 60 percent.
Why: For most steels the fatigue (endurance) limit lies roughly at one-half of the static ultimate tensile strength, so the 40 to 60 percent band is the accepted figure. Higher ranges overstate fatigue strength, which is why repeated-load design stresses are kept well below the static ultimate tensile strength.· FAA-H-8083-30 — Aircraft Materials, Hardware, and Processes
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The ability of mild steel to carry additional load after the yield point is reached is due to
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Answer: strain hardening.
Why: Beyond the yield point mild steel deforms plastically, and the dislocation movement that produces this deformation tangles and multiplies the dislocations, so the metal grows harder and carries more load. This work or strain hardening continues up to the ultimate strength. Necking is the local thinning that occurs afterward, not the strengthening mechanism.· FAA-H-8083-30 — Aircraft Materials, Hardware, and Processes
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A Rockwell tester is used to perform what type of materials test?
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Answer: Hardness testing.
Why: A Rockwell tester measures hardness by pressing a ball or diamond indenter into the surface under a set load and reading the depth of penetration directly as a hardness number. It does not pull or cyclically load the specimen, so it performs neither tensile nor fatigue testing.· FAA-H-8083-30 — Aircraft Materials, Hardware, and Processes
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What type of materials test uses a weighted pendulum to strike a specimen until it fractures?
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Answer: An impact test.
Why: A weighted pendulum swung to strike and fracture a specimen describes an impact, or toughness, test such as the Charpy or Izod, which measures the energy absorbed at fracture. A hardness test uses a static indenter and a fatigue test applies many repeated load cycles, so neither involves a single pendulum blow.· FAA-H-8083-30 — Aircraft Materials, Hardware, and Processes
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Frequently asked questions
- What does the T mean in an aluminum designation like 2024-T3?
- T means the alloy has been thermally treated, and the digit says how. T3 is solution heat treated and then cold worked, T4 is solution heat treated and naturally aged, and T6 is solution heat treated and then artificially aged. An O suffix means annealed, and an H suffix means strain hardened, which applies to the alloys that cannot be strengthened by heat treatment.
- How do you read an AN bolt part number?
- The number following AN gives the shank diameter in sixteenths of an inch, so an AN4 bolt is four sixteenths, or one quarter inch. The dash number that follows encodes the length, and a letter suffix records material and drilling. An A after the dash number means the shank is not drilled for a cotter pin. Head markings identify the bolt's material and type separately.
- Which way does safety wire go on two bolts?
- It is routed so that the tension in the wire pulls each fastener in the tightening direction. Using the double-twist method, the wire leaves the first bolt on the side that would tighten it, runs to the second bolt, and enters it the same way, so a fastener that starts to back off puts the wire in tension. Wire is single use and is discarded once removed.
- Can magnetic particle inspection be used on aluminum parts?
- No. Magnetic particle inspection requires a ferromagnetic material, so it works on steel and iron parts but not on aluminum, magnesium, titanium or austenitic stainless. For those, use dye penetrant for defects that break the surface, or eddy current, ultrasonic or radiographic methods for subsurface indications. Choosing a method that suits the material is a common written question.
All 40 ACS areas
General
- Fundamentals of Electricity and Electronics
- Aircraft Drawings
- Weight and Balance
- Fluid Lines and Fittings
- Aircraft Materials, Hardware, and Processes
- Ground Operations and Servicing
- Cleaning and Corrosion Control
- Mathematics
- Regulations, Maintenance Forms, Records, and Publications
- Physics for Aviation
- Inspection Concepts and Techniques
- Human Factors
Airframe
- Metallic Structures
- Non-Metallic Structures
- Flight Controls
- Airframe Inspection
- Landing Gear Systems
- Hydraulic and Pneumatic Systems
- Environmental Systems
- Aircraft Instrument Systems
- Communications, Light Signals, and Runway Lighting Systems
- Aircraft Fuel Systems
- Aircraft Electrical Systems
- Ice and Rain Control Systems
- Airframe Fire Protection Systems
- Rotorcraft Fundamentals
- Water and Waste Systems
Powerplant
- Reciprocating Engines
- Turbine Engines
- Engine Inspection
- Engine Instrument Systems
- Engine Fire Protection Systems
- Engine Electrical Systems
- Engine Lubrication Systems
- Ignition and Starting Systems
- Engine Fuel and Fuel Metering Systems
- Reciprocating Engine Induction and Cooling Systems
- Turbine Engine Air Systems
- Engine Exhaust and Reverser Systems
- Propellers
Primary sources
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