6.11- Electrical Cables and Connectors Flashcards
What is a wire?
An isolated single copper conductor surrounded by insulation.
What is a cable? (Electrical)
Group of two or more conductors separately insulated and grouped together by an outer sleeve.
What is a stranded copper conductor normally used for and what are the strands often coated in?
Maximum wire flexibility
Tin, nickel or silver.
What are wires with aluminium conductors used for?
Large loads like galleys to save weight.
What are the requirements for materials used as insulation?
Voltage resistant up to 600V Resistant to aircraft fluids Flexible Strong Lightweight
What are the bands of temperature that wire types are categorised into (Normal, high and very high)?
100/150°c
250°c
400°c
What are shielded wire types used for?
To protect against erratic signals or magnetic interference.
In signal circuits operating below 50KHz how is maximum shielding protection provided?
By grounding the shield on one side only, this prevents back-flow of current.
What is different about the grounding of the shield on ARINC 429 data bus?
Its grounded at both ends instead of just one.
What is coaxial cable used for?
To transport high frequency signals.
Which sides of coaxial cable are grounded for best transmission?
Both sides.
For Boeing wire type codes what should you refer to?
SWPM 20.
For Airbus wire type codes what should you refer to?
ESPM 20.
What does BMS stand for?
Boeing Material Specification.
What is BMS 13-28 equal to in MIL spec?
MIL-W 7139
What is Boeing Type 1 Wire?
Insulated wire with one conductor
What is Boeing Type 2 Wire?
Type 1 with shield.
What is Boeing Type 3 Wire?
Type 2 with yet another shield.
What is Boeing Class 1 wire?
Single insulated wire.
What is Boeing Class 2 wire?
Two insulated wires.
How does the Boeing wire size numbering system work?
Its a reverse numbering system to represent the current carrying capacity.
All single wires and multi conductors (red wire only) should have what?
A manufacturers legend in a contrasting colour at intervals of 100-150mm.
What should the manufacturers legend on a wire include?
Spec Manufacturer Country of origin Year of manufacture Wire size (AWG)
How can wires be marked?
Mechanical printing
Ink-jet
Co2 laser
UV laser.
What are the boeing rules for wire marking?
Must be marked at each end within 10cm. Biggest marking interval is 72in Upper case easily read at 15in Minimum contrast of 55%
In system wire coding what does the second letter provide?
A more detailed description of the system.
What system does the letter coding SA represent?
Radio Altimeter.
If there is more than one system then how are numbers used before the system code?
A number is placed before the letters e.g. 1 SA or 2 SA
Radio altimeter system #1
Common use for system wiring is identified using what system?
ATA 100.
What is a WDM?
Wiring diagram manual.
How is wire size denoted?
Through the use of the American wire gauge (AWG), it is reverse numbered.
In the Wire code W104-G-299-22R what do the separate parts represent?
W104- Wire bundle G- System code 299- Wire no. 22- Wire size R- Colour code.
What is the difference between an even bundle no. and an odd bundle no.?
An even no. is electrical system and an odd is an electronic system.
In airbus system coding what do the first two and third/fourth digits refer too?
First two= ATA Chapter
Third/fourth= ATA sub chapter
If the number of wires in which 100% current is flowing is lower, then what will happen to the maximum current flow?
It will increase.
What is one of the main advantages of aromatic polymide?
Saves 50% weight and 30% space.
At what temperature does Aromatic polymide smoulder at?
815°C
What phenomena is known to destroy Aromatic Polymide?
Carbon arc tracking.
What two categories are there of carbon arc tracking?
Dry and wet.
What is dry carbon arc tracking?
Wire to wire or wire to ground, carbon build up.
What is wet carbon arc tracking?
Fluid build up instead of carbon in dry arc.
What are Exhaust gas temperature cable conductors made from?
Chromel and Alumel.
What makes the identification of a thermocouple wire different to a standard wire?
The colours are different, often white/green.
For fire warning wires what is the maximum fire resistance?
1093°C for 5 minutes.
What must fire warning wire conform too?
MIL-W-25038
What are electrical connectors used for?
To allow maintenance where frequent disconnection is required.
What is a more modern and common way of connecting a contact to a connector? Solder or crimping?
Crimping.
What must be used to terminate aluminium cables?
Aluminium or bimetal (AlCu) terminations.
Which side of the connector will have a socket instead of the pins?
The ‘hot’ side as it avoids the risk of electric shock.
What two basic groups of connector are there?
Split shell (disassembled) Assembled construction.
How are split shell connectors identified?
By AN numbers.
How many types of AN connector are there in how many classes?
Six types in 5 classes.
What is a Class A AN connector?
General purpose, one piece back shell.
What is a Class B AN connector?
Back shell is two parts.
What is a Class C AN connector?
Pressurised connector.
What is a Class D AN connector?
Moisture and vibration resistant.
What is a Class K AN connector?
Fireproof connector. Made of steel.
What are the most common connector type?
Assembled connector.
What does an assembled connector consist of?
Insert locking mechanism and insulator. The backing clamp is a separate part and has a different part number.
For circular connectors, the master keyway is always positioned in which direction?
Either top dead or facing forward to the aircraft.
How is shell size denoted?
1/16 inch, and the letter S is used to denote a short housing.
For a plug to be environmentally sealed what must be done with any unused contact holes?
Fitted with nylon or tTeflon seal plugs.
For crimped contact connectors outside the pressurised area what must be fitted?
Unwired contacts in conjunction with seal plugs.
Where can you find alternative part numbers and manufacturers?
In the standard practices manual.
What is a polarisation key?
Prevents the wrong computer being inserted into a shelf.
What must be done to to non-self locking threaded coupling connectors located in high vibration areas?
They must be lockwired.
