CORROSION
What corrosion involves only the metal surface, and appears over a wide area?
Uniform surface corrosion
Rationale: General surface corrosion (also referred to as uniform etch or uniform attack corrosion) is the most common form of corrosion. Surface corrosion appears as a general roughening, etching, or pitting of the surface of the metal, frequently accompanied by a powdery deposit of corrosion products.
Why is it critical for an AMT to verify the revision block before starting work on a component?
It confirms the drawing is current and accurate for work
Rationale: It makes sure they are using the current approved drawing for accurate work.
Which tool is used to create or repair threads inside a hole?
Tap
Rationale: Taps are designed to cut or repair internal threads.
Which part number designation identifies a universal head rivet?
AN470
Rationale: AN470 identifies a universal head shape rivet.
Which material is known to damage anodized aluminum surfaces?
Steel wool
Rationale: Steel wool is too abrasive and can scratch the protective anodized layer on aluminum. It can also leave behind particles that may rust, compromising both appearance and corrosion resistance.
What is the primary purpose of aircraft paint?
To protect the aircraft from corrosion.
Rationale: Paint acts as a protective layer, preventing corrosion
What document provides safety and handling information for chemicals used in corrosion control?
Safety Data Sheet (SDS)
Rationale: The SDS outlines hazards, handling procedures, PPE requirements, and emergency measures for chemicals.
This is the allowable plus or minus variation from the dimension given on the drawing?
Tolerance
Which of these materials is most anodic?
Magnesium
Rationale: Magnesium is the most anodic of these materials. Some of the common metals in the order of their electrochemical activity are: Magnesium, Zinc, Cadmium, 7075 Aluminum alloy, 2024 Aluminum alloy, Mild Steel, Copper, Stainless Steel, Chromium, Gold.
Why are exploded views helpful for AMTs?
They show parts separated to see how they fit together.
Rationale: Exploded views visually show how parts relate to each other and how they fit together, helping AMTs put them together accurately. This helps AMTs understand part relationships during assembly.
You are tasked with measuring the outside diameter of a shaft that must fit within a specific tolerance. You have a steel ruler, a caliper, and a micrometer available. Which tool should you select, and why?
Use the micrometer because it provides the highest level of precision needed for tight tolerance measurements.
Rationale: Micrometers provide thousandths of an inch precision, critical for tight tolerance components.
Where is an AN clevis bolt used in an airplane?
Only in shear load applications
Rationale: A clevis bolt should be used only where the load to which the bolt is applied is a shear load. A clevis bolt is not designed to take any type of tensile load. The threaded portion of a clevis bolt is short and there is a groove between the threads and the shank. The head of a clevis bolt has a screwdriver slot rather than flats for the use of a wrench.
What is Alclad aluminum?
Pure aluminum layered over an aluminum alloy core for corrosion resistance.
Rationale: Alclad consists of a pure aluminum layer bonded to an aluminum alloy for corrosion resistance and strength.
What is a “fisheye” defect in aircraft paint?
Small round spots where paint pulls away, exposing the surface
Rationale: This is the standard description of a “fisheye” defect, often caused by surface contamination like oil or silicone.
What is the most significant reason for using Alclad instead of pure aluminum when forming aircraft skins?
It provides a corrosion-resistant layer while maintaining the strength of the aluminum alloy core.
Rationale: Alclad uses a thin, pure aluminum layer to resist corrosion while maintaining the alloy’s strength inside.
What type of diagram would a mechanic use for troubleshooting?
Schematic Diagram
What type of corrosion is "smoking rivets" associated with?
Fretting corrosion
Rationale: The most common example of fretting corrosion is the smoking rivet found on engine cowling and wing skins.
What does a Half Section drawing help an AMT see?
Both the inside and outside of a symmetrical part
Rationale: A Half Section drawing is used for symmetrical parts and shows both the inside and outside. This helps an AMT understand the full structure without needing multiple views.
Which measuring tool is best suited for checking the diameter of a small aircraft shaft?
Caliper
Rationale: Calipers (vernier/digital) provide precise diameter measurements.
Aircraft bolt diameters are measured in?
1/16
Rationale: Aircraft bolt diameters are measured in 16ths.
Why is it important for an AMT to understand the properties of non-ferrous metals like, aluminum and titanium during aircraft inspections and repairs?
These metals require unique handling, repair methods, and prevent corrosion while maintaining aircraft performance.
Rationale: Knowledge of non-ferrous metals’ corrosion resistance, weight, and repair considerations ensures proper maintenance practices and safety.
A primary reason why ordinary or otherwise non-approved cleaning compounds should not be used when washing aircraft is because their use can result in:
Hydrogen embrittlement in metal structures
Rationale: Some nonapproved commercial cleaning compounds can cause a chemical reaction with some of the metals used in aircraft structure. This reaction releases hydrogen gas that can be absorbed into the metal and cause hydrogen.
Which property does hardness testing evaluate in a metal?
The metal’s resistance to being dented
Rationale: Hardness testing measures resistance to denting and deformation.
In what type of electrical diagram are images of components used instead of conventional electrical symbols?
Pictorial Diagram
As electrons pass from the Anode to the Cathode, which one corrodes?
Anode
Rationale: As electrons are passed from the anode to the cathode, the anode deteriorates as its electrons are diminished.
Which type of diagram shows a simplified system overview?
Block diagram
Rationale: Block diagrams give a simplified overview of a system. They help you understand the basic functions of connected parts.
What is the purpose of the vernier scale on calipers and micrometers?
To allow for more precise readings
Rationale: The vernier scale provides fine measurement subdivisions, allowing readings to be taken with greater accuracy than the main scale alone.
Why is it important for an AMT to inspect O-rings on hydraulic lines for cracks and hardening during routine maintenance?
It can allow hydraulic fluid leaks, leading to system failures or loss of control.
Rationale: Cracked or hardened O-rings can leak, causing hydraulic system failures,which can lead to serious safety issues.
Which letter designates a metal is in its annealed condition?
-O
Rationale: In the temper designations used with aluminum alloy, “O” means the metal has been annealed.
After cleaning a metal surface on the aircraft, what should the AMT do next to ensure proper paint adhesion and corrosion protection?
Clean the surface well and check for dust, oil, or water before painting.
Rationale: Proper cleaning removes contaminants that prevent paint from bonding effectively and protects against corrosion.
The side clearances of piston rings are measured with a:
Thickness gauge
Rationale: A thickness gauge is used to measure gaps/clearances/distances between surfaces
A hydraulic system schematic drawing typically indicates the what?
The direction of fluid flow through the system.
Which type of corrosion occurs when two dissimilar metals are in contact with each other in the presence of an electrolyte?
Galvanic corrosion
Rationale: Galvanic corrosion occurs when dissimilar metals touch in moisture.
What type of line is used to show exposed surfaces?
Sectioning Line
Rationale: Sectioning lines (also called crosshatch lines) are used in drawings to indicate exposed surfaces in a sectional view, showing where material has been “Cut through.”
What tool is used to mark precise, fine lines on metal surfaces before cutting or drilling?
Scriber
Rationale: Scribers are pointed tools used to create fine, permanent lines on metal surfaces to guide accurate cutting or drilling.
Aircraft solid rivet diameters are measured in
1/32
Rationale: Rivet diameters are measured in 32nds
Which heat-treated aluminum alloy is most commonly used for aircraft skin?
2024
Rationale: 2024 is commonly used for stringers, bulkheads, skin, rivets, and extruded sections.
Which two types of paint are most commonly used on aircraft?
Polyurethane and epoxy
Rationale: These types are most commonly used in aviation due to their durability, resistance to chemicals, and ability to protect against corrosion and environmental stress.
While working on an aircraft windshield replacement, you find light scratches on the new acrylic transparent panel. What is the best course of action before installation?
Polish out the scratches using an approved plastic polish to restore visibility and prevent crack propagation.
Rationale: Approved polishing restores optical clarity, maintains safety, and prevents stress crack propagation in acrylic windows.
What type of diagram shows the wire size required for a particular installation?
A Wiring Diagram
While cleaning corrosion from an aluminum component, you observe localized pitting after removing the surface corrosion. What is the appropriate next step before applying alodine?
Ensure all corrosion is removed and inspect the area for remaining pitting.
Rationale: Before applying alodine, the surface must be free of corrosion and cleaned thoroughly. Pitting indicates deeper corrosion, which must be fully removed to prevent structural degradation and ensure proper bonding of chemical treatments.
Why are the notes included on maintenance drawings important to a technician?
They provide additional instructions not easily shown graphically.
Rationale: Notes give instructions, tolerances, and references critical for safe, compliant work.
Why is it important for an AMT to use the ratchet feature on a micrometer instead of turning the thimble directly when measuring engine components?
The ratchet allows consistent measuring pressure, ensuring repeatable and accurate measurements.
Rationale: The ratchet applies consistent pressure to prevent overtightening, avoiding part deformation and ensuring measurement accuracy across users.
Aircraft bolt threads are what fit?
Class 3
Rationale: Aircraft bolt threads are a class 3 fit (medium fit).
Which property of metals describes how much a material expands when heated?
Thermal expansion
Rationale: Thermal expansion describes size changes with temperature.
What is plastic media blasting (PMB) used for during surface preparation?
To gently remove paint and rust without damaging surfaces.
Rationale: PMB uses soft plastic particles to safely strip paint and light corrosion from aircraft skins and delicate surfaces without damaging underlying material
(especially aluminum).
The letter “A” appearing at the end of a part number for a bolt indicates?
Undrilled shank
Rationale: The letter “A” after the dash number in a bolt part number indicates “no hole in the shank”
Working drawings may be divided into three classes. They are:
Detail drawings, assembly drawings, and installation drawings.
What is the main difference between aluminum oxide and iron oxide?
Aluminum oxide forms a stable protective layer, while iron oxide flakes away, exposing more metal.
Rationale: Aluminum oxide creates a stable layer preventing further corrosion, while iron oxide flakes off, allowing corrosion to continue.
What is the function of phantom lines in aircraft drawings?
They show where a part might move or where a missing part would.
Rationale: Phantom lines (long dash, short dash, short dash) indicate alternate positions of moving parts or related parts not shown.
When removing a stuck fastener or trimming a metal edge, which tool is most appropriate to use?
Chisel
Rationale: A chisel is the proper tool to cut, shear, or chip away metal. It can be used to remove a stuck fastener head or trim excess metal edges when precision cutting tools are not appropriate.
How would you identify an aluminum alloy bolt?
A double dash on the head
Rationale: A double dash on the head of a bolt indicates an aluminum alloy bolt.
The letter T indicates a metal is in what condition?
Heat treated
Rationale: In aircraft metals, the letter “T” indicates the metal has undergone specific heat treatments (like quenching, cooling, and aging) to achieve desired mechanical strength and stability.
During a post-paint inspection, an AMT notices a cloudy, milky finish on the surface of a newly painted aircraft panel. What is the most likely cause of this defect?
The humidity in the paint booth was too high during application.
Rationale: High humidity can cause blushing, where moisture gets trapped in the paint as it flashes off, creating a cloudy appearance
What grade aluminum alloy is the “field rivet”?
AD- 2117
Rationale: The 2117-T rivet, known as the field rivet, is used more than any other for riveting aluminum alloy structures.
A drawing in which the subassemblies or parts are shown as brought together on the aircraft is called a what?
Installation Drawing.
How is corrosion commonly described in aviation?
Metal returning to its natural state.
Rationale: Aluminum oxide does not evaporate, and iron oxide does not remain protective.
Which type of pictorial drawing shows a 3D object with combined views?
Isometric
Rationale: Isometric drawings show multiple sides of an object tilted at equal angles, giving a 3D-like view without perspective distortion.
Convert 480 inch-lbs. to foot-lbs.
40 ft-lbs
Rationale: Divide 480 inch-lbs. by 12 to convert to foot-lbs. = 40 ft. lbs.
A rivet with a dimple on the head is made of:
2117
Rationale: A rivet made of 2117 is identified by a dimple or recessed dot head marking.
What is the property, which enables a metal to carry heat or electricity?
Conductivity
Rationale: Conductivity is the property that enables a metal to carry heat or electricity.
An AMT has just finished painting a wing panel and observes an orange peel texture on the surface. What should the AMT do before attempting to repaint the panel to ensure a smooth finish?
Check and adjust the paint viscosity, thinner ratio, and spray technique according to specifications.
Rationale: These are the appropriate procedural adjustments to address and prevent orange peel after identifying a surface defect.
If it is necessary to accurately measure the diameter of a hole approximately ¼ inch in diameter, the mechanic should use a:
Small-hole gauge and determine the size of the hole by taking a micrometer reading of the ball end of the gauge
Rationale: A small hole gauge is a precision measuring tool used with an outside micrometer to find the internal diameter of small holes (up to ¼”), acting as a transfer gauge by expanding to fit snugly inside the bore and then being measured externally for an indirect reading, ideal for parts like valve guides where standard inside micrometers or telescoping gauges won't fit.
What is the class of working drawing that describes or depicts a single part?
Detail Drawing
What form of corrosion appears as “worm-like” lines under paint due to trapped moisture?
Filiform corrosion
Rationale: Filiform corrosion shows as lines under paint.
What is the primary purpose of a nomogram in aviation maintenance?
Calculate approximate values without a calculator
Rationale: Nomograms are used for quick calculations (weight & balance, conversions) in the field.
Which tool is used to measure the clearance between a surface plate and a relatively narrow surface being checked for flatness?
Thickness gauge
Rationale: A thickness gauge is used to measure gaps/clearances/distances between surfaces.
Which type of aircraft cable is constructed of seven strands and 19 wires in each strand
7 x 19 cable
Rationale: The 7 × 19 cable is made up of seven strands of 19 wires each. Six of these strands are laid around the center strand. This cable is extra flexible and is used in primary control systems and in other places where operation over pulleys is frequent.
What is the purpose of tempering after hardening steel during heat treatment?
To reduce brittleness and improve toughness.
Rationale: Tempering is a post-hardening process used to relieve internal stresses, reduce brittleness, and increase toughness while still maintaining most of the hardness.
Which chemical treatment is specifically noted as a milder option for treating aluminum parts with complex shapes?
Sodium dichromate solution
Rationale: Sodium dichromate solution is recognized as a milder and safer chemical treatment for aluminum parts, especially those with complex geometries. It effectively treats corrosion while minimizing damage or aggressive chemical action, making it suitable for delicate or intricate components.
Why would a topcoat begin to peel if it is applied several days after an epoxy primer has been applied to a composite panel without additional surface preparation?
The primer cured fully and needed sanding for proper bonding.
Rationale: After full cure, epoxy primer loses chemical bonding ability. Re-sanding is required to create a surface the topcoat can adhere to mechanically.
In a sectional view drawing, what sections illustrate particular parts of an object?
Removed Sections.
What type of corrosion is typically indicated by white/gray powder deposits on aluminum surfaces?
Aluminum corrosion
Rationale: Corrosion of aluminum often produces white, powdery or puffy deposits which are a known visual indicator specific to this metal.
A solid line with one arrowhead is called a:
Leader line
Rationale: Leader lines are solid lines with one arrowhead.
Find the torque wrench indication required to torque a bolt to 700 foot-pounds with a torque wrench 66.5 inches long and an extension of 7 inches long. Use the formula (T x L / L + E)
633.3 in-lbs
Rationale: Substitute the values in the formula: 700 in-lbs x 66.5 inches / 66.5 inches + 7 inches = 633.33 in. lbs
What does the “H” signify in the following part number? AN6H34
The head is drilled for safety wire
Rationale: The letter “H” between the diameter and length indicates a hole in the head, used for safety wire.
Why is annealing used on aluminum alloys before forming complex aircraft components?
To soften the aluminum, restoring ductility and reducing cracking during forming.
Rationale: Annealing relieves internal stresses, restores ductility, and allows aluminum to be formed into complex shapes without cracking.
What is the primary purpose of using sandwich panels in aircraft construction?
To increase strength while minimizing weight
Rationale: These panels consist of two strong outer layers (face sheets) and a lightweight core, providing excellent strength-to-weight performance, which is ideal for aircraft structures.
You are tasked with priming a bare, aluminum part on an aircraft before painting. Which primer should you use to ensure corrosion resistance and proper topcoat adhesion?
Epoxy Primer
Rationale: Epoxy primers are widely used on aircraft aluminum due to their strong adhesion, corrosion resistance, and chemical durability. They are ideal under most topcoats.
Objects of uniform thickness, gaskets, shims, and plates might be represented by what type of drawing?
One-View Drawings