2/2 Chapters 7-9 & 11: Aircraft Materials, Hardware, and Processes (Includes Hand tools and Measuring Devices)

What is indicated by the markings on the heads of solid shank rivets?

The material they are made of, and indirectly, their strength

How can you keep heat treated aluminum alloy rivets soft enough to install after the quenching process?

If the rivets are stored in a freezer they will remain soft for several days

What is the grip length of a bolt?

The length of the unthreaded portion

In what way are AN standard steel bolts identified?

By the code markings on the bolt heads

What is the difference between a close tolerance bolt and a general purpose bolt?

Close tolerance bolts are machined to more accurate dimensions

For what types of applications are self-locking nuts not allowed?

Self-locking nuts may not be used when either the bolt or the nut is subject to rotation

If the maintenance procedures do not specify a torque value for a bolt or nut, how can you determine the proper values?

Consult a standard torque table such as found in AC 43.13-1B

What is the most commonly used type of aircraft control cable?

Extra flexible 7x19 stainless steel cable

What type of precision measuring instruments can be used to measure the outside dimensions of aircraft parts?

Outside micrometers and vernier calipers

For what reasons should a micrometer be periodically calibrated?

1. If dropped, its accuracy may be affected

2. If the spindle is over-tightened, the frame may be sprung

3. Continually sliding objects between the anvil and the spindle may wear the surfaces

Describe the steps involved in a dye-penetrant inspection

The surface is cleaned, and then a penetrant is applied and allowed to dwell for a specified time. The penetrant is them removed with an emulsifier or cleaner. Once removed, the part is dried and then developer is applied. The results are then inspected and interpreted

Name some tools that are commonly used to assist in making visual inspections of welds

A magnifying glass, flashlight, mirror and possibly a borescope

What are some of the non-destructive testing methods that may be used on aluminum parts?

visual, dye penetrant, eddy current, ultrasonic testing and radiography

What process occurs during the preparation stage of a dye penetrant inspection when the penetrating liquid is applied, and then removed from a cracked part?

The penetrant enters the crack by capillary action and remains there until made visible by the developer

A correctly made butt weld will have what bead width and how much penetration?

The bead width should be 3-5 times the thickness of the base metal and there must be 100% penetration

What telltale characteristics are evidence of a cold weld?

A cold weld has rough, irregular edges that are not feathered into the base metal and has variations in penetration amounts

The penetration of a fillet weld should be what percentage of the thickness of the base metal?

25-50%

Describe the basic steps for conducting a magnetic particle inspection

Magnetize the part, then coat the surface with ferromagnetic particles. If a defect or discontinuity is present, the particles align with the discontinuity forming a visible pattern

Describe the procedure for performing a magnetic particle inspection

Thoroughly clean all grease, oil, and dirt from the metal part which must be of ferrous material such as iron or steel. Magnetize the part and then apply the ferromagnetic particles, either held in liquid suspension or in dry powder form, to the area to be inspected. If a discontinuity is present, the magnetized particles will form a grip length pattern in the approximate shape of the discontinuity

What are two types of self-locking nuts?

All metal, fiber-lock, or elastic stop nuts

What is the general rule for using self-locking nuts?

Do not use self-locking nuts at joints which are subject to rotation

How can the correct grip length of a bolt be determined?

The grip length should equal the total thickness of the materials being joined together. The grip of a bolt is the unthreaded portion of the bolt shank

The length of AN standard bolts are measured in what fraction?

1/8 of an inch

What does the triangle mean on the head of a steel bolt?

That it is a close tolerance bolt

What numbers are used for close tolerance bolts?

AN-173 through AN-186 for hex-head bolts, and NAS-80 through NAS-86 for countersunk

A solid rivet diameter is always measured in what fraction?

1/32 of an inch

Describe a rivnut

It is a threaded body that is expanded to the aircraft structure

What is the purpose of a channel nut and nutplate?

Both nuts allow a screw or bolt to be installed without needing to hold the nut with a wrench

What are common materials for cotter pins to be made out of?

Low carbon steel and stainless steel

What term is used to describe a metal that is iron-based?

Ferrous alloy

What system is used to identify AN type aircraft bolts?

Aircraft bolts have code markings on the bolt heads for identification. Bolt diameter is measured in 1/16ths of an inch and length is measured in 1/8ths of an inch

What is the difference between a close-tolerance and regular AN bolt?

Close-tolerance bolts are used in applications where the bolted joint is subjected to severe vibrations and load reversals. Also, close-tolerance bolts are machined to more precise standards and must be driven in by a hammer

What is done to prevent certain aluminum alloy rivets (D and DD) from becoming hard after heat treating and quenching?

The rivets are stored in a refrigerator at a temperature lower than 32 degrees F. The rivets will remain soft for several days. They are also called "ice box rivets"

What do rivet head markings indicate?

The alloy of the rivet

Why is alloy steel that is responsive to heat treatment usually less suitable for welding?

Because of its tendency to become brittle and lose its ductility around the weld

Why should steel be normalized after welding or machining?

To remove internal stress of the metal, thereby reducing brittleness

What are two methods of case hardening?

Carburizing and nitriding

What should be used to make a visual inspection of a weld?

A magnifying glass of at least 10x

Name some types of non-destructive testing used on non-ferrous materials

Eddy current, dye penetrant, x-ray, coin tap, and visual inspection

Which NDT method can be performed without removing the surface coatings such as primer, paint, and anodized films and is effective in detecting surface and subsurface corrosion?

Eddy current inspection method

What is the most common type of corrosion?

Surface corrosion

Why should a micrometer be periodically calibrated?

To ensure micrometer accuracy

A solid rivet length is measured in what fractional increments?

1/16"

What are some types of washers used on aircraft?

Spring lock washer, flat washer, lock tooth washer, tab washer, and finishing washer

What is an MSDS?

Material Safety Data Sheet (This is an old term, the new term is SDS - Safety Data Sheet)

What class bolts are used on aircraft?

Class 3 bolts

What do the markings on the heads of solid shank rivets indicate?

The material they are made from and their strength

Which steel alloy is noted for its toughness and is most used for aircraft tubular structure, such as frame members, engine mounts, landing gear parts, and other structural parts?

Chrome-Molybdenum Steel

What portable hardness tester is commonly used for testing aluminum alloys, copper, brass, or other relatively soft materials?

Barcol tester

Name the types of materials commonly used as the reinforcing component in structural composite laminates

Kevlar, fiberglass, or graphite

Name the substances commonly used as the matrix material in structural composite laminates

Polyester resin and epoxy resin

Name one advantage of using pre-impregnated materials over non-preimpregnated materials in the construction or repair of composite components

1. Pre-impregnated fabric contains the proper amount of matrix

2. The reinforcing fibers are completely and evenly permeated with matrix

3. The matrix has the correct proportions of resin and hardener

What is a plug used to repair threads?

Helicoil

Name two measurement systems used for aircraft hardware

SAE and metric

How would you repair a thread which is damaged?

Helicoil

Why is Tig welding preferred over flux welding?

It produces the highest quality of weld

What are the three differences between aluminum and copper wire?

Size, weight and price

What kind of bolts are used in landing gear?

Steel

What are engine mounts made of?

Steel

Risk management: What are the common personal protection equipment (PPE) items that an aviation mechanic should have access to?

Hearing protection, eye protection, gloves, aprons, dust masks, and respirators

Risk management: What are some of the dangers that could be caused by improper torque?

Too low of torque could cause components to loosen and come apart. Too high of torque could cause failure of the bolt or component or cause a rotating component to seize and not function as designed. All of these failures could cause loss of a system, or even loss of an aircraft and potential loss of life.

Risk management: Why is the use of used hardware or suspected unapproved parts (SUPS) undesireable?

In addition to creating an unairworthy condition, the risk of failure increases, which could cause damage to a system or the aircraft

Risk management: Where would an aviation mechanic find the proper procedure for torquing critical, highly stressed fasteners?

In the aircraft manufacturer's maintenance manual

Risk management: What is the proper technique when using a torque wrench?

Pull the wrench assembly with a smooth, steady motion until the proper torque is reached. A fast or jerky motion will result in an improper torque