Aircraft Materials, Hardware, and Processes practice questions

Answer: A) To protect the steel against corrosion, especially in salt-laden air

Cadmium plating is used mainly to protect steel hardware from corrosion, especially in marine (salty) environments. It does not raise strength, and it limits the hardware to about 450°F or below.

• ACorrect. Cadmium is an electrolytically deposited plating that gives very good corrosion protection, particularly in a salty atmosphere.
• BIncorrect. Cadmium-plated hardware is restricted to 450°F or below. Above that, the cadmium diffuses into the steel and makes it brittle.
• CIncorrect. A thin plating adds no structural strength. Strength comes from the base alloy and its heat treatment.
• DIncorrect. Cadmium is a conductive metal, not an insulator. It is a protective coating, not an electrical barrier.

Answer: D) Toughness and impact resistance at low weight

• AIncorrect. Aramid is difficult to cut and sand.
• BIncorrect. Aramid is non-conductive.
• CIncorrect. Aramid is weak in compression.
• DCorrect. Aramid resists impact and penetration.

Answer: A) About 1.5D wide and 0.5D high

• ACorrect. The standard shop head is 1.5D wide and 0.5D high.
• BIncorrect. That head would be overdriven.
• CIncorrect. An unspread shank does not hold the joint.
• DIncorrect. Shop head size is checked against standard dimensions.

Answer: C) When the installation is exposed to temperatures above about 250°F

Fiber and nylon insert locknuts are limited to about 250°F, so all-metal self-locking nuts are used in higher-temperature locations. Bolts that rotate in service and cotter-pin installations need castellated nuts instead.

• AIncorrect. No self-locking nut should be used on a bolt that rotates in service. A castellated nut with a cotter pin is used there instead.
• BIncorrect. Cotter-pin safetying calls for a castellated or castle nut, not a self-locking nut of either type.
• CCorrect. Fiber and nylon inserts are limited to about 250°F, so all-metal locknuts are used in hot areas such as near engines and exhausts.
• DIncorrect. All-metal locknuts must still meet minimum prevailing torque before reuse. Frequent removal is not the reason to choose them.

Answer: D) Only one side is reachable

• AIncorrect. They are structural fasteners.
• BIncorrect. Solid rivets are usually preferred then.
• CIncorrect. They are used on metal structures.
• DCorrect. Blind rivets are installed from one side when the back is inaccessible.

Answer: A) Internal stresses are relieved and the grain structure is refined

Normalizing heats steel above its upper critical temperature and cools it in still air. This relieves internal stresses from welding, forging or machining and refines the grain. It is not the same as hardening, tempering or case hardening.

• ACorrect. Heating above the upper critical temperature turns the structure into austenite. Cooling slowly in still air then forms a uniform, fine-grained structure, which relieves the stresses left by welding, forging or machining.
• BIncorrect. Maximum hardness comes from hardening, which means heating and then quenching quickly in water, oil or brine. Normalizing cools slowly in still air, so it does not produce maximum hardness.
• CIncorrect. This describes tempering, which is done after hardening at a temperature below the critical range. Normalizing heats the steel above the upper critical temperature.
• DIncorrect. This describes case hardening, such as carburizing or nitriding. Normalizing treats the whole part evenly rather than creating a separate surface layer.

Answer: D) Quick-access cowlings and inspection panels

• AIncorrect. Terminals use screws or studs.
• BIncorrect. Primary structure uses bolts and rivets.
• CIncorrect. Lines use AN and MS fittings.
• DCorrect. A quarter turn locks or releases the panel.

Answer: C) A cotter pin through a drilled bolt

• AIncorrect. Castle nuts are used on bolts.
• BIncorrect. Castle nuts rely on a cotter pin, not an insert.
• CCorrect. The cotter pin passes through the nut's slots and the bolt hole.
• DIncorrect. A cotter pin provides the safetying.

Answer: B) Two rivet diameters

• AIncorrect. This is too close to the edge.
• BCorrect. Minimum edge distance is generally 2D for protruding-head rivets.
• CIncorrect. This is far more than the minimum.
• DIncorrect. Edge distance is based on diameter.

Answer: A) 2117-T4 (AD)

• ACorrect. A dimpled head identifies a 2117-T4 (AD) rivet.
• BIncorrect. 1100 rivets have a plain head.
• CIncorrect. D rivets have a raised dot.
• DIncorrect. B rivets have a raised cross.