Aircraft Wiring and Bonding Regulations

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Questions and Answers

What is the primary consideration when testing electrical bonding in aircraft?

The specific requirements detailed in aircraft or component publications (correct)

The length of the braid used in bonding

The resistance of the bonding jumper

The type of paint used on the aircraft

What should be removed or pierced before testing electrical bonding?

RF components

Cadmium and tin plate

Protective treatments such as priming and finishing paints (correct)

Bonding jumpers

What is the maximum resistance required for general electrical bonding?

0.05 Ω

0.025 Ω

0.1 Ω (correct)

0.0025 Ω

What is the reference standard for bonding of RF components?

MIL-STD-464 Signup and view all the answers

What is the maximum length of braid used in bonding to moving parts?

12 in. Signup and view all the answers

What is the purpose of forming a leak-proof joint at the end connections of flexible fuel pipes?

To give a good electrical bond and resistance Signup and view all the answers

What is the maximum resistance allowed for bonding between components and main earth?

0.05 Ω Signup and view all the answers

What is the maximum resistance allowed for bonding between extremities of the aircraft?

0.05 Ω Signup and view all the answers

What is the purpose of the colour-coding on pre-insulated terminals?

To indicate the wire size range that can be terminated Signup and view all the answers

What is the minimum wire gauge size that can be terminated with a terminal having yellow insulation?

12 Signup and view all the answers

What is the purpose of the self-locking ratchet mechanism in approved hand crimping tools?

To prevent the tool from opening during crimping Signup and view all the answers

What is the range of wire sizes that can be crimped using the M22520/5 tool?

26 through 10 Signup and view all the answers

What is the purpose of the removable dies in the M22520/5-01 and M22520/10-01 tools?

To crimp wires of different sizes Signup and view all the answers

How are the crimping dies retained in the tool frame?

By internal spring clips Signup and view all the answers

What is the purpose of the hexagonal crimp dies?

To offer a variety of crimping combinations Signup and view all the answers

Why should the self-locking ratchet mechanism never be disassembled?

To ensure proper crimping closure Signup and view all the answers

What is a common feature among all MIL-DTL-22520 hand-operated tools?

cycle control through a ratchet mechanism Signup and view all the answers

What is the primary function of the indenters in the M22520/1-01 crimping tool?

to create four sets of double impressions on the contact Signup and view all the answers

What is the purpose of the provision for selecting the proper depth of crimp in the M22520/1-01 crimping tool?

to ensure consistent crimp quality Signup and view all the answers

What is unique about the M22520/4-01 crimping tool?

it is used only with the M22520/4-02 single positioner head Signup and view all the answers

What type of contacts can be crimped using the M22520/2-01 crimping tool?

contacts with wire barrel sizes 20 through 28 Signup and view all the answers

What is the primary application of the M22520/4 crimping tool?

crimping outer pin and socket coaxial contacts to shielded cables Signup and view all the answers

What is a characteristic of the indenters in the M22520/1-01 crimping tool?

they close to create four sets of double impressions Signup and view all the answers

What is a common aspect of the M22520/1-01 and M22520/2-01 crimping tools?

they have provisions for selecting the proper depth of crimp Signup and view all the answers

What does a larger AWG number represent in an aircraft wire?

A smaller wire diameter Signup and view all the answers

What is the cross-sectional area of a round conductor measured in?

Circular mils Signup and view all the answers

What is the unit of measure for square or rectangular conductors?

Square mils Signup and view all the answers

How is the cross-sectional area of a round conductor calculated?

By squaring the conductor's diameter Signup and view all the answers

What is the purpose of a wire gauge?

To determine the wire size of conductors Signup and view all the answers

What is the smallest size wire normally used in aircraft?

22-gauge wire Signup and view all the answers

What is the purpose of the white end of the rear-release connector contact insertion/removal tool?

To slips around the contact and release the locking device Signup and view all the answers

What is a characteristic of rear-release connectors?

They have a blue band around the shell of the connector Signup and view all the answers

What is the diameter of a 22-gauge wire?

0.025 in. Signup and view all the answers

What is the relationship between 1 circular mil and 1 square mil?

1 cmil is equal to 0.7854 sq mil Signup and view all the answers

What is the benefit of using rear-release connectors?

They reduce contact bend damage during servicing Signup and view all the answers

What is the purpose of the conductor channel and serrations in the insertion/removal tool?

To aid in conductor/contact support Signup and view all the answers

What is the colour coding typically used for in rear-release connectors?

To reflect AWG sizing Signup and view all the answers

What is the correct sequence of actions to remove a contact from a rear-release connector?

Put the tool over the wire, then insert the tool through the insert and pull the wire together Signup and view all the answers

What is the advantage of using plastic insertion and removal tools?

They are less expensive than metal/plastic tools Signup and view all the answers

What is the purpose of the red end of the rear-release connector contact insertion/removal tool?

To secure the locking device with forward pressure Signup and view all the answers

Study Notes

Aircraft Electromagnetic Bonding and Wiring Practices

Remove or pierce protective treatments (e.g. priming and finishing paints, varnishes, chromic, anodic, and phosphate coatings) before testing, except for cadmium and tin plate.
Connect the single-prong probe of the 60-ft static lead to an airframe earth point.

Electrical Bonding Requirements

The resistance across a bonding or grounding jumper should be 0.1 Ω or less for general electrical bonding.
For RF components, the resistance should be a maximum of 0.0025 Ω (2.5 mΩ).

Bonding Resistance Checks

Check the resistance between cleaned areas of the object and the structure after mechanical connection is completed.
Ensure bonding resistance between extremities of the aircraft is within the manufacturer’s limits (not to exceed 0.05 Ω [50 mΩ] on all-metal aircraft).
When checking bonding between components and main earth, the resistance should not exceed 0.05 Ω (mid-scale deflection).

Bonding Jumpers and Flexible Fuel Pipes

Bonds to moving parts should be made of braid (maximum length 12 in.) connected by bolts or clamps with only sufficient slack for working purposes.
Flexible fuel pipes are bonded internally, and the resistance should not exceed 0.025 Ω/ft length or 0.05 Ω (50 mΩ), whichever is greater.

Crimping Tools and Terminal Lugs

Use only tools qualified to MIL-DTL-22520 for crimping terminal lugs.
Colour-coded terminal lugs or splices are used to identify wire sizes.
Examples of crimping tools include M22520/5, M22520/10, and M22520/1-01.

Rear Release Connectors

Rear release connectors have a blue band around the shell (body) of the connector and utilise insert lock retention.
Removal tools must be put over the wire and inserted through an insert (grommet) to release the contact.
Rear release pins and sockets are widely used in aircraft connectors.

Wire Size and Measurement

Aircraft wire is measured by the AWG system, with larger numbers representing smaller wires.
The smallest size wire normally used in aircraft is 22-gauge wire, with a diameter of about 0.025 in.
Circular mil (cmil) is the standard measurement of a round conductor’s cross-sectional area.
Square mil is the unit of measure for square or rectangular conductors such as bus bars.

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Description

This quiz covers the specific regulations and guidelines for aircraft wiring and bonding, including procedures for testing and safety protocols. It references AC 21-99 Aircraft Wiring and Bonding Sect 2 Chapter 13. Topics include removing protective treatments and connecting static leads to airframe earth points.