6.11 Electrical Cables and Connectors Flashcards
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
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.
What are the characteristics of aircraft cables?
Minimum Weight and dimensions
Resistant to fluids
Non-flammable
Resistance to abrasion
Deterioration
What temperature are aircraft cables fire resistant up to?
400 ^C for fire resistant cables
Up to 1100 ^C for 5 minutes
What standards are aircraft wiring manufactured to?
MIL-W
Military spec cables
What material is tinned for general service wire?
Copper
What material is silver or nickel plated for use in high temperature areas?
Copper
Done to prevent oxidation and to facilitate soldering
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
Give a list of high vibration areas on an aircraft?
Engine
Pylon or Apron
APU compartment
Wheel Well
Wing
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
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
What type of wires would you use in high temperature areas?
Some form of glass braid or fluorocarbon insulation
What type of wires would you use in general aircraft wiring?
Kapton WIring
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
What type of wire would you use in cold areas and give a reason why?
normal temperature type wire
What type of wire would you use in circuits that would be required to function after a fire?
Fire Resistant Wire
(Contains Silicon)
What are the two basic methods of applying insulation material to conductors?
Extrusion
Wrapping
What is the registered trade name for “Kapton” wiring?
‘Kapton’ is Aromatic polyamide produced by Dupoint
Give a brief explanation of the problem(s) associated with “Kapton” wiring?
Short Circuit arc tracking (flashover)
How is the problem associated with “Kapton” wiring overcome?
Hybrid wire
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
What does TKT stand for?
PTFE / Kapton /PTFE
List the characteristics of TKT?
Lightweight
Arc-track resistant
abrasion resistant
superb insulation protection
high heat tolerance (260^C)
Resists smoking when burning
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?
2
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
