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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
What are the categories of temp ranges?
Up to 100c Normal Up to 260c high temp Up to 1093c fire res
26
What is verdigris?
Blue green deposit on copper
27
What is the most preferred coating?
Nickel coating.
28
What other factors are important in the selection of insulation?
Insulation resistance and dielectric strength.
29
How is insulation resistance testing carried out?
Megohmmeter
30
What is dielectric resistance?
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
What are new aircraft design cable insulation made of?
Tefzel
32
In the context of magnetic interference, what is the benefit of using a twisted cable?
Because they are twisted the two fields cancel each other out.
33
How are cables that carry AC or pulsating DC prevented from causing interference?
Shielded
34
What is a coaxial cable?
A special type of shielded cable used to connect most of the radio receivers and transmitters.
35
What is critical for the efficiency of energy transfer in coaxial cable?
The spacing and concentricity of the two conductors.
36
What does EMI stand for?
Electromagnetic interference
37
What causes EMI?
Electromagnetic fields inducing high voltage.
38
What percentage of wires should be covered with shielding?
85%
39
How many grounds should a 50khz cable have?
1
40
When installing a data bus cable what must be avoided?
Pinching or bending and the correct length is used.
41
What must substitutions be made in accordance with?
Guidance detail in the manufacturers electrical manuals.
42
In the AWG what is a larger number representing?
Smaller wires
43
Typically what is the smallest wire size used on aircraft?
22 or 24
44
What is the approx. diameter of 18 gauge wire?
1mm
45
What is the approx. diameter of 24 gauge wire?
0.5mm
46
What can not be measured on the wire gauge?
Stranded wire.
47
What allows you to identify metric cross section wires?
Dashed green line down the outside of the insulation.
48
What are the two different markings on wires and cables?
Manufacturer part number Installation functionality
49
If insulation could be damaged by being marked how else can it be identified?
Printed sleeve at regular intervals of around 1.8m.
50
With direct marking how far apart should it be?
Within 3 inch of the end of the wire Every 15 inches along the wire
51
At what distance should markings be easy to read?
40cm and have minimum contrast of 55%
52
What will happen in a thermocouple when the two junctions are at different temps?
The current will flow
53
What are EGT thermocouples made of?
Chromel and Alumel
54
What are twin core insulation colours?
Red/Blue
55
How can you repair alumel wires?
Only with alumel splices.
56
What colour is the insulation for a chromel thermocouple wire?
White
57
What colour is the insulation for a Alumel thermocouple wire?
Green or red
58
What colour is the insulation for a copper thermocouple wire?
Red
59
What colour is the insulation for a constantan thermocouple wire?
Yellow
60
What is the 'general purpose' thermocouple wire?
Type K (Chromel/Alumel)
61
Is Alumel magnetic?
Yes
62
In Chromel and Alumel what is the main alloy?
Nickel
63
What is constantan?
The proprietary name for copper-nickel alloy also known as eureka.
64
What mil spec must fire warning systems conform too?
MIL-W-25038
65
When replacing a coaxial cable what must not be used as a replacement under any circumstances?
Solid centre coax

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

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