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CAT B- Mod 6 Materials and Hardware > 6.11 Electrical Cables > Flashcards

6.11 Electrical Cables Flashcards

1
Q

What considerations have to be taken in the design of wires?

A

Non-flammability
Operating temps
Resistance to abrasion
Wet arc tracking

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2
Q

What is wet arcing?

A

Failure of cables when a combination of insulation damage and fluid contamination.

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3
Q

What are the typical nominal voltages?

A

14,28,115

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4
Q

Where are cable ratings stamped on an older cable?

A

Outer sheath or colour ident

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5
Q

Modern wires have what stamped on them?

A

The AWG gauge number

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6
Q

What is a good replacement for aluminium cable?

A

Copper

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7
Q

What is a cable?

A

Two or more wires that are insulated separately in the same outer insulation.

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8
Q

What is a twisted cable?

A

Two or more separately insulated conductors that are then twisted together into strands.

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9
Q

What is a shielded cable?

A

One or more insulated strands that are overlaid with a metallic braided shield.

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10
Q

What is the main difference between pressurised and unpressurised cables?

A

Unpressurised generally has thicker and stiffer insulation.

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11
Q

When was Nyvin no longer used?

A

1990s

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12
Q

What was the most common form of nyvin and what was it replaced by?

A

Uninyvin replaced by raychem 44a

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13
Q

Where was Uninyvin-Metsheath used?

A

A screened cable used in ratio and fuel quantity.

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14
Q

What is a SWAMP area?

A

Severe Weather and Moisture Prone areas.

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15
Q

What areas would be considered SWAMP?

A

Wheel wells
Leading/trailing edge
Engine Pylons

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16
Q

What is an interconnect wire?

A

Used in protected areas, generally thinner insulation and more flexible.

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17
Q

What is the ultimate life of fire cable?

A

Five minutes at 1100 degrees c

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18
Q

What are the operating temps of fire wire?

A

-55 to 190 degrees c

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19
Q

What is Efglas?

A

A high-temperature resistant cable required in some engine circuits. The exterior finish is white. Generally used on older engines.

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20
Q

What type of cable has pretty much replaced nyvin and minyvin?

A

Thin wall cables

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21
Q

What is KP150?

A

A modern general-purpose cable. Has large saving in weight and space over Nyvin.

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22
Q

What colour gradings of BMS 13-13 is there?

A

Single cables are coloured white and doubles are red and blue. Triples are red, yellow, and blue.

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23
Q

How do you prevent a data bus cable from its signal being affected?

A

Screen it.

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24
Q

What is the voltage resistance for insulation?

A

Up to 600v

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25
Q

What are the categories of temp ranges?

A

Up to 100c Normal
Up to 260c high temp
Up to 1093c fire res

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26
Q

What is verdigris?

A

Blue green deposit on copper

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27
Q

What is the most preferred coating?

A

Nickel coating.

28
Q

What other factors are important in the selection of insulation?

A

Insulation resistance and dielectric strength.

29
Q

How is insulation resistance testing carried out?

A

Megohmmeter

30
Q

What is dielectric resistance?

A

The ability of a material to withstand high potential difference. Expressed as the voltage at which the material fails and breaks down due to electrostatic stress.

31
Q

What are new aircraft design cable insulation made of?

A

Tefzel

32
Q

In the context of magnetic interference, what is the benefit of using a twisted cable?

A

Because they are twisted the two fields cancel each other out.

33
Q

How are cables that carry AC or pulsating DC prevented from causing interference?

A

Shielded

34
Q

What is a coaxial cable?

A

A special type of shielded cable used to connect most of the radio receivers and transmitters.

35
Q

What is critical for the efficiency of energy transfer in coaxial cable?

A

The spacing and concentricity of the two conductors.

36
Q

What does EMI stand for?

A

Electromagnetic interference

37
Q

What causes EMI?

A

Electromagnetic fields inducing high voltage.

38
Q

What percentage of wires should be covered with shielding?

A

85%

39
Q

How many grounds should a 50khz cable have?

A

1

40
Q

When installing a data bus cable what must be avoided?

A

Pinching or bending and the correct length is used.

41
Q

What must substitutions be made in accordance with?

A

Guidance detail in the manufacturers electrical manuals.

42
Q

In the AWG what is a larger number representing?

A

Smaller wires

43
Q

Typically what is the smallest wire size used on aircraft?

A

22 or 24

44
Q

What is the approx. diameter of 18 gauge wire?

A

1mm

45
Q

What is the approx. diameter of 24 gauge wire?

A

0.5mm

46
Q

What can not be measured on the wire gauge?

A

Stranded wire.

47
Q

What allows you to identify metric cross section wires?

A

Dashed green line down the outside of the insulation.

48
Q

What are the two different markings on wires and cables?

A

Manufacturer part number
Installation functionality

49
Q

If insulation could be damaged by being marked how else can it be identified?

A

Printed sleeve at regular intervals of around 1.8m.

50
Q

With direct marking how far apart should it be?

A

Within 3 inch of the end of the wire
Every 15 inches along the wire

51
Q

At what distance should markings be easy to read?

A

40cm and have minimum contrast of 55%

52
Q

What will happen in a thermocouple when the two junctions are at different temps?

A

The current will flow

53
Q

What are EGT thermocouples made of?

A

Chromel and Alumel

54
Q

What are twin core insulation colours?

A

Red/Blue

55
Q

How can you repair alumel wires?

A

Only with alumel splices.

56
Q

What colour is the insulation for a chromel thermocouple wire?

A

White

57
Q

What colour is the insulation for a Alumel thermocouple wire?

A

Green or red

58
Q

What colour is the insulation for a copper thermocouple wire?

A

Red

59
Q

What colour is the insulation for a constantan thermocouple wire?

A

Yellow

60
Q

What is the ‘general purpose’ thermocouple wire?

A

Type K (Chromel/Alumel)

61
Q

Is Alumel magnetic?

A

Yes

62
Q

In Chromel and Alumel what is the main alloy?

A

Nickel

63
Q

What is constantan?

A

The proprietary name for copper-nickel alloy also known as eureka.

64
Q

What mil spec must fire warning systems conform too?

A

MIL-W-25038

65
Q

When replacing a coaxial cable what must not be used as a replacement under any circumstances?

A

Solid centre coax

CAT B- Mod 6 Materials and Hardware (14 decks)

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