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NCATT AET Volume 2 > 5-1) Aircraft Wiring > Flashcards

5-1) Aircraft Wiring Flashcards

1
Q

What are some characteristics of aircraft wiring?

A

lighter weight, corrosion resistant, consistent construction, don’t product dangerous fumes when burned, better able to withstand vibration/motion without breaking

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2
Q

What types of wires are used on cars vs. aircraft?

A

Cars and trailers typically use solid core wire. Aircraft typically use stranded core wire, which accept solder and crimp better.

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2
Q

What types of wires are used on cars vs. aircraft?

A

Cars and trailers typically use solid core wire. Aircraft typically use stranded core wire, which accept solder and crimp better.

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3
Q

What are the two best metal conductors?

A

Gold and silver

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4
Q

What are the two best insulators?

A

Neon and helium

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5
Q

Why do aircraft use stranded copper wire?

A

flexibility and resistance to vibration damage

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6
Q

Why aren’t solid core wires used in aircraft?

A

They are susceptible to work hardening from movement and vibration that can cause cracking and stress fractures.

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7
Q

What two quantities of strands in an aircraft wire are typically used?

A

7-strand and 19-strand

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8
Q

What process to aircraft wires undergo to prevent oxidation and promote solderability?

A

Coating / pre-tinning with a protective coating

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9
Q

How are coating materials rated?

A

According to their ability to withstand heat

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10
Q

What is the key source of heat in question that the wire needs protection against?

A

Heat generated by flow of current in the wire, not by heat around the wire in the aircraft

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10
Q

What is the key source of heat in question that the wire needs protection against?

A

Heat generated by flow of current in the wire, not by heat around the wire in the aircraft

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11
Q

What temperature can tin-lead coating protect up to?

A

105°C

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12
Q

What temperature can silver coating protect up to?

A

200°C

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13
Q

What temperature range can nickel coating protect up to?

A

200-260°C

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14
Q

What atomic properties do good insulators have?

A

They have more than 4 valance electrons. Insulators will not accept the extra electrons from current flow easily, therefore they are considered to have high resistance.

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14
Q

What atomic properties do good insulators have?

A

They have more than 4 valance electrons. Insulators will not accept the extra electrons from current flow easily, therefore they are considered to have high resistance.

15
Q

What are general physical properties of insulation material?

A

operating temperature, insulation resistance, abrasion resistance, chemical resistance, strength

16
Q

What is a particular kind of wire insulation that was a total failure that technicians needs to be aware of?

A

Kapton

17
Q

What hazards does Kapton insulation pose?

A

Does not age well. Prone to extreme arcing and flashover. Recognized by its woven cover and metallic shield.

18
Q

What kind of insulated wire is this?

A

Kapton

19
Q

Under what circumstances can Kapton insulated wire be used even though its dangers are well known?

A

Manufacturer requires its use.

20
Q

Why do some wires/cables come with shielding?

A

Shielding is for protection from radio frequency interference (RFI) both from the wire itself and from outside sources getting into the wire.

21
Q

Does wire shielding totally nullify electromagnetic interference?

A

No, but it can redirect that energy into the ground to minimize the introduction of noice/interference into the wire

22
Q

What are coaxial cables designed to do?

A

They are designed to pass on high-frequency signals from a source to an antenna.

23
Q

What is the typical impedance of coaxial cable on an aircraft?

A

50Ω

24
Q

What makes aluminum wire desirable for some aircraft applications?

A

Lighter weight than copper wire

25
Q

What is the minimum wire gauge size for aluminum wire in an aircraft?

A

6AWH

26
Q

What precautions must be made when using aluminum wiring?

A

Aluminum wire is more susceptible to work hardening than copper wire. Terminations must be made for the aluminum wire to prevent galvanic corrosion that would be present when two dissimilar metals are attached. Hardware must be compatible to avoid electronic corrosion.

27
Q

What standard is used to specify wire diameters?

A

American Wire Gauge (AWG)

28
Q

What is the proportional relationship between wire diameter and wire gauge?

A

Wire diameter doubles (or halves) for every 3 wire gauge sizes.

29
Q

What is the diameter of #20 AWG wire?

A

0.032 inches

30
Q

What is the diameter of #0 AWG wire?

A

0.325 inches

31
Q

What unit is used to specify a wire’s cross-sectional area?

A

Circular mil area

32
Q

How is circular mil area calculated?

A

Wire diameter (in inches) is squared

Example: #20 AWG is 0.032” diamater

0.0322=1024 circular mils

33
Q

What are the characteristics of MIL-W-5086 Type I wire?

A

Type I is an unshielded aircraft wire. MIL-spec wire is constructed of a stranded tinned copper conductor, white polyvinyl chloride insulation, and a clear nylon outer jacket. MIL-spec wire may be used in electronic or electrical applications.

34
Q

What are the characteristics of MIL-W-5086 Type II wire?

A

Also an unshielded aircraft wire. #22 AWG through #12 AWG are constructed of stranded tinned copper conductor with a white PVC insulation and a white class yarn braid. MIL-spec wire has a clear nylon outer jacket.

Gauges #10 AWG through #0000 AWG are constructed of stranded tinned copper conductor with a white PVC insulation and a white class yarn braid.

Wire has a flame retardant nylon lacquered glass with yarn braid overall. MIL-W-5086 Type II may be used as airframe wire at temperatures within the range of -55°C to +105°C.

35
Q

What is the voltage rating for MIL-spec wire?

A

600 volts

36
Q

What are common physical properties for both Type I and II MIL-W-5086 wire?

A

Resistant to: water, aircraft fuels, hydraulic fluids, oils, Skydrol (fire resistant aviation hydraulic fluid), dilute acids, ethylene glycol, alkalis, alcohol, fungus, abrasion.

37
Q

Under was extreme conditions may MIL-spec wires be used?

A

Any application where it may be exposed to abrasion, high impact loads or chemical abuse

37
Q

Under was extreme conditions may MIL-spec wires be used?

A

Any application where it may be exposed to abrasion, high impact loads or chemical abuse

38
Q

Explain the steps to take to use this wire selection chart.

A
  1. Select column for circuit voltage on the left
  2. Select the length of wire from the correct circuit voltage column
  3. Look to the right and find the correct diagonal line corresponding to the current (amperes) to be used
  4. Find the intersection of that current rating with the wire size from the X-axis
  5. Based on the use “Continuous Rating-Cables in a Bundle,” “Continuous Rating-Wire in Free Air,” “Intermittent Rating” etc., make sure that the point of intersection of length, amperes and wire gauge is ABOVE the selected curve for the wire’s use.
  6. If the point of intersection is not ABOVE the curve, move up in wire gauge size (larger wire, lower AWG number to the right).
    1. If the determined point for length and current falls between two wire gauge sizes, always move up to the next larger wire size.

NCATT AET Volume 2 (10 decks)

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