6.11 Electrical Cables and Connectors Flashcards by Joshua McDonnell

Explain what is meant by the expression “the aircraft electrical installation is of the single wire type”?

This means only one wire is used to support the supply of electric current to the user.

The return path is established via the metallic structure of the aircraft

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Explain what is meant by the term “standard”?

A standard is an accepted or approved example of something against which others are judged or measured.

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What are the characteristics of aircraft cables?

Minimum Weight and dimensions

Resistant to fluids

Non-flammable

Resistance to abrasion

Deterioration

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What temperature are aircraft cables fire resistant up to?

400 ^C for fire resistant cables

Up to 1100 ^C for 5 minutes

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What standards are aircraft wiring manufactured to?

MIL-W

Military spec cables

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What material is tinned for general service wire?

Copper

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What material is silver or nickel plated for use in high temperature areas?

Copper

Done to prevent oxidation and to facilitate soldering

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Define current handling capacity?

In some instances, the wire may be capable of carrying more current than is recommended for the contacts of the related connector.

In this instance, it is the contact rating that dictates the maximum current to be handled by the wire

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Give a list of high vibration areas on an aircraft?

Engine

Pylon or Apron

APU compartment

Wheel Well

Wing

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How would you provide flexibility to a cable?

Both copper and aluminium wires are stranded for protection against breakage from vibration and to offer more flexibility

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What determines the type of insulation in a cable?

Operating environment e.g Abrasive, arc, corrosion resistance

Cut-through strength

dielectric strength

Flame resistance

mechanical strength

smoke emission

fluid resistance and heat distortion

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What type of wires would you use in high temperature areas?

Some form of glass braid or fluorocarbon insulation

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What type of wires would you use in general aircraft wiring?

Kapton WIring

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Describe the type of tools that would be used to remove and install the contacts on a rear release system?

Crimp tool and a rear accessory backshell

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What type of wire would you use in cold areas and give a reason why?

normal temperature type wire

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What type of wire would you use in circuits that would be required to function after a fire?

Fire Resistant Wire

(Contains Silicon)

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What are the two basic methods of applying insulation material to conductors?

Extrusion

Wrapping

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What is the registered trade name for “Kapton” wiring?

‘Kapton’ is Aromatic polyamide produced by Dupoint

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Give a brief explanation of the problem(s) associated with “Kapton” wiring?

Short Circuit arc tracking (flashover)

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How is the problem associated with “Kapton” wiring overcome?

Hybrid wire

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Give a brief explanation of how flashover occurs in “Kapton” wiring?

Repeated exposure to moisture and tiny pinholes also occur due to excessive flexing and chafing

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What does TKT stand for?

PTFE / Kapton /PTFE

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List the characteristics of TKT?

Lightweight

Arc-track resistant

abrasion resistant

superb insulation protection

high heat tolerance (260^C)

Resists smoking when burning

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What is the purpose of shielding aircraft wiring?

Screening or shielding is carried out ot protect against electromagnetic interference (EMI) or ‘noise’

List some examples of shielded wires?

Data bus cables carrying digital data Microphone wires

What would you say about shielded wiring operating below 50 kHz?

The shields of shielded wires should be grounded at only one end to prevent earth loops. Shielded wires operate in circuits below 50kHz

Where would you use thermocouple cables?

These cables are used for the connection of cylinder head temperature indicators (HTI), Turbine engine exhaust gas **temperature indicators and other temperature indicating systems.**

What precaution should you take with thermocouple cables?

The wiring between the temperature junction probe and the indicating system should be the same material over its entire length or errors in temperature indication will be the result.

List the two most common types of thermocouples and their application?

Copper and Constantan- Cylinder head temperature Chromel and alumel used for exhaust gas temperature, oil and brake temperature indication

What type of insulating material is used on thermocouple cables?

Silicone rubber or PTFE impregnated fibreglass

What is the purpose of high tension cables?

(Ignition cables) These are used for the transmission of high tension (high voltage) in both piston and turbine engine ignition systems

Why are ignition cables screened?

To prevent interference (noise)

What is the colour code for an aircraft three phase circuit? Phase A Phase B Phase C

Phase A = Red Phase B = Yellow Phase C = Blue

What are the common uses of co-axial cables?

Co-axial cables are used for the transmission of low power signals, with the signal line (the inner conductor) protected from unwanted signals (noise) by the outer wire braid. Radio equipment, transceivers Fuel quantity indicating systems

What would you say about the grounding of co-axial cables?

Coaxial cables are grounded at both ends

What is the spacing interval of the manufacturer’s number on a wire?

150mm to 500mm in indelible ink Manufacturer's code number contains: Country of origin Wire type (spec) Year of manufacture

What is the voltage rating of the insulation of general aircraft wiring?

600V

What information is contained on the manufacturer’s number of a wire?

Type of cable (spec) Country of origin manufacturer's code number Year of manufacture Wire size gauge (AWG)

What is the spacing interval of a wire identification number?

Each end of the wire and at 15 inch (38cm) max intervals along the length of the wire

Which wires should not be stamped?

Wires less than 3 inches in length need not be identified

What are the allowable voltage drops for 14, 28, 115, and 200 volts supply systems on both continuous and intermittent operation?

For continuous operation 14V = 0.5V 28V = 1V 115V = 4V 200V = 7V For intermittent operation, multiply each value by 2

What do you understand by the term “circular mil”?

Area of a circle having diameter of 0.001 inch

What are the two types of terminal used on aircraft installations?

Crimped Type Soldered Type

Why are terminal lugs colour coded?

To indicate the wire sizes that they can accommodate

Discuss the use of copper or aluminium terminals?

Aluminium wire shall only be terminated with an aluminium terminal Same for copper as otherwise Galvanic corrosion will occur (Corrosion of dissimilar metals)

Name the two main manufacturers of terminal lugs?

AMP and Burndy

In a cross section, how would a copper conductor differ from an aluminium conductor of the same current rating compare?

Aluminium would be thicker as has lower conductivity property than copper

What would you look for after crimping an AMP terminal?

The number of dots to confirm if job done correctly White and blue are 2 dots Rest are 1

Having correctly crimped a white terminal using an AMP hand tool, how many dots will be indented on the terminal?

What does the ratcheting mechanism in a hand operated crimp tool ensure?

The crimp tool if of the ratchet type, meaning once the crimping action is started, the tool cannot be opened until completion of the crimping operation

What factors determine the choice of connector on an aircraft?

Weight and dimensions Resistant to fluids Flammability Abrasion Deterioration

What is the purpose of strain relief backshells?

Strain relief backshells have very small size wiring, requiring frequent maintenance and in high vibration areas

What factors must you consider when choosing a particular backshell?

Wire Quantity and types Shield material gauge number and type jacket material and thickness

List the three types of plug receptacle used on aircraft?

Threaded coupling Bayonet coupling Push/pull slide type coupling

In high vibration areas what type of connector coupling would you use?

Threaded connector

What is the purpose of stone keys?

This is a groove in the connector housing to provide for the correct mating of the connectors

What is copper and constantan thermocoupling used for:

Cylinder head temperature

What is chromel and alumel thermocoupling used for:

Exhaust Gas temperature (EGT) oil and brake temperature indication