Aircraft Maintenance: Joggle Joint with Doubler

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Questions and Answers

What is the purpose of a joggle joint with a doubler?

To allow the two pieces of metal to be on the same plane (correct)

To increase the strength of the joint

To reduce the weight of the structure

To pull the doubler against the skin with rivets

What is the primary factor that governs the strength of a joint?

Plate specification (correct)

Material thickness

Rivet spacing

Rivet specification

What is the recommended diameter of a rivet relative to the thickness of the plate?

4 times the thickness of the plate

1.5 times the thickness of the plate

3 times the thickness of the plate

2.5 times the thickness of the plate (correct)

What is the purpose of the sphere of influence of a rivet?

To maintain the plates in close proximity Signup and view all the answers

What is the approximate area of the sphere of influence of a rivet?

5 times the diameter of the fastener Signup and view all the answers

Why is it important to consider the position of rivets relative to the edge of the sheet material?

To prevent tearing through the material under load Signup and view all the answers

What happens when the pitch of rivets is 4D?

The sphere of influence of each rivet overlaps Signup and view all the answers

Why is it important to determine the rivet spacing and pattern?

To prevent leakage in pressurized areas Signup and view all the answers

What is the required air pressure to operate the hammers in a rivet gun?

80 lb/in2 Signup and view all the answers

What type of spring is used to hold the rivet snaps in a rivet gun?

Spiral retaining spring Signup and view all the answers

Why is it important to handle rivet guns with care?

To avoid injury to persons or damage to equipment Signup and view all the answers

Why should a rivet be driven with as few blows as possible?

To minimize work hardening of the rivet Signup and view all the answers

What is the purpose of a slow, hard-hitting, long-stroke gun?

For larger rivets that are relatively accessible Signup and view all the answers

What is the purpose of a light, fast-hitting rivet gun?

For small rivets in thin skins Signup and view all the answers

What method is used to install large quantities of rivets along an easily accessible edge?

Squeeze riveting Signup and view all the answers

What is a potential danger associated with compressed air and pneumatic tools?

Serious injury to persons or damage to equipment Signup and view all the answers

What is the minimum distance between the rivet centre and the edge of the material?

2D Signup and view all the answers

What is the diameter of a circle that is determined by the pitch of a number of rivets of a given size?

Pitch circle diameter Signup and view all the answers

What type of rivet layout is commonly used in watertight joints and high-stress areas?

Multiple row Signup and view all the answers

What is the percentage of the rivet pitch that staggered riveting is equal to?

75% Signup and view all the answers

What can happen if the hole is too small for the rivet?

The rivet will be shaved off its shank Signup and view all the answers

What is the minimum distance between adjacent rows of rivets?

3-4D Signup and view all the answers

What is the purpose of the pitch circle diameter?

To determine the diameter of circular repairs Signup and view all the answers

What is a common consequence of countersinking too deep?

Holes become out of line Signup and view all the answers

What type of rivet layout is used chiefly on attachment and lightly stressed joints?

Single row Signup and view all the answers

What is indicated by a clinched shop head?

The bucking bar was held at an angle Signup and view all the answers

What can cause a skin to bulge?

Holes that are not lined up Signup and view all the answers

What is the result of a rivet being hammered too hard for thin skin?

A skin bulge Signup and view all the answers

What can cause swelling between sheets?

Both A and B Signup and view all the answers

What is the result of a rivet snap not being held straight?

An open head Signup and view all the answers

What happens if the shank of a rivet is too long?

A flash forms around the rivet head Signup and view all the answers

What can cause a rivet head to crack?

Snap heads forming on the tail of the rivet Signup and view all the answers

What is the consequence of using a snap that is too small for the rivet?

It will mark the rivet head. Signup and view all the answers

What should be inspected after the rivets have been closed?

The rivets to ensure they are tight and fully formed. Signup and view all the answers

Why might replacing rivets that are only slightly below standard do more harm than leaving them in position?

It may cause further damage to the surrounding material. Signup and view all the answers

When is the flushness tolerance for countersunk rivets normally checked?

Before riveting is commenced. Signup and view all the answers

What should be applied after milling solid rivet heads to obtain a uniform protrusion?

A protective treatment. Signup and view all the answers

What is a characteristic of a good countersunk rivet?

The manufactured head is flat against the metal. Signup and view all the answers

What should be uniform in height with adjacent rivets?

The rivet. Signup and view all the answers

What should be concentric in a good rivet?

The shop heads. Signup and view all the answers

Study Notes

Joggle Joint with Doubler

A joggle is formed to allow two pieces of metal to be on the same plane, rather than pulling the doubler against the skin with rivets.

Strength of Joints

The strength of a joint is governed by plate specification, rivet specification, and rivet spacing.
Plate specification involves selecting a material and gauge that can withstand tensile and bearing loads.
Rivet specification involves selecting a rivet that can withstand shear loads, with a diameter 2.5 times the thickness of the plate.
Rivet spacing is determined to give the joint optimum strength characteristics.

Rivet Sphere of Influence

The sphere of influence of a rivet is the area in which the closed rivet maintains the plates in close proximity, approximately 5D (5 times the diameter of the fastener).
When the pitch of rivets is 4D, the sphere of influence of each rivet overlaps, providing a fluid-tight joint.

Rivet Positions

The position of rivets relative to each other and the edge of the sheet material is important.
Rivets must not be too close together, as an excessive number of holes weakens the joint.
Rivets must not be too far apart, as there are too few to take the load, causing leakage in pressurized areas.
Rivets must not be too near the edge of the sheet, as they tear through the material when the joint is under load.

Pitch Circle Diameter (PCD)

Pitch circle diameter is the diameter of a circle dictated by the pitch of a number of rivets of a given size.
It is used to determine the diameter of circular repairs.

Rivet Layout

Single-row layout is used chiefly on attachment and lightly stressed joints.
Multiple-row layout is common for watertight joints and in places of high stress where thick gauge plate is used.
Staggered layout is used as an alternative to multiple rows in watertight joints, circular patches, etc.

Riveting Tools and Procedures

Clearance is important to avoid shaving off the protective oxide coating on the rivet or buckling the sheet metal.
Air pressure required to operate rivet guns is around 80 lb/in2.
Retaining springs are used to hold the snap in the gun, but can fail to hold the snap, resulting in serious injury or damage.
Rivet guns must be handled with care, and the rule is to never play with rivet guns.

Squeeze Riveting

The squeeze method is used to install large quantities of rivets along an easily accessible edge.

Rivet Sets (Snaps)

Ensure that the snap used is the correct size for the rivet to avoid marking the rivet head or skin.

Rivet Inspection

Rivets should be inspected to ensure they are tight and fully formed.
Rivet heads must not be deformed or cracked, and the surrounding area should be free from distortion and undamaged by the riveting tools.
Rivets that are obviously not performing their function should be replaced, but replacing rivets that are only slightly below standard might do more harm than leaving them in position.

Faults

Cracks in the rivet head are not normally acceptable.
Snap heads formed on the tail of the rivet can result in faults such as a ‘flash’ round the rivet head or small head, accompanied by snap marks on the skin.
Countersinking too deep, holes out of line, high shop head, clinched shop head, flattened shop head, uneven shop head, skin bulged, swelling between sheets, and open head are all faults that can occur during riveting.

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Description

Learn about the strength of joints and factors affecting joint strength in aircraft maintenance, including the use of joggles and doublers.