Soldering And EWIS Installation

Question 1

What are the two types of solder?

Answer 1

Tin lead alloy

Silver

Question 2

When would silver solder be used?

Answer 2

Where stronger joins are required

Question 3

What would tin lead alloy solder be used for?

Answer 3

Lower soldering temperatures, usually for electrical or electronic joints

Question 4

What is a flux and is it always needed in addition to the solder when soldering?

Answer 4

A flux is used to remove oxide from the contact surfaces and to promote good solder flow.
No, in most cases a flux is built into the solder itself

Question 5

What are the recommendations for soldering concerning the contacts?

Answer 5

Arrange contacts so solder bucket is facing upwards
Clean contacts with spirit, let them dry
Place tip of iron below contact and place conductor into the bucket

Question 6

What are the soldering recommendations concerning dry joints?

Answer 6

Hold conductor in place- movement causes dry joints

Check for a shiny appearance- dull is dry joint

Question 7

What are some other misc. recommendations for soldering?

Answer 7

Flow solder into bucket until level is correct
Check as possible that solder has flowed into conductor
Ensure no strands are outside the bucket
Ensure no excess solder is on outside of bucket

Question 8

What should be done if a dry joint occurs and why?

Answer 8

Remake it

Dry joints have a high resistance and are fragile

Question 9

What is a solder sleeve pigtail a common method for?

Answer 9

Attaching a shield ground wire to a shielded cable

Question 10

What is included on the sleeve of a pigtail?

Answer 10

Two Sealing rings on either end and a band of solder in the middle

Question 11

What preparation is required for solder sleeve pigtails?

Answer 11

Ground wire and cable shield are stripped to the correct length

Question 12

How is the pigtail installed?

Answer 12

Positioned with the solder band over the stripped areas of the wire and cable
Heat gun is used to shrink, seal and flow the solder in the pigtail to create the electrical join and a good pigtail.

Question 13

What should be looked for when inspecting pigtails?

Answer 13

Discolouration- only acceptable if solder can be inspected and if sleeve has not split
Seal rings created an environmental seal
Solder band has fully melted around wire and shield braid

Question 14

What range does a wire failures impact have

Answer 14

Minor inconveniences to major catastrophes

Question 15

Why has wiring been made a critical safety of flight system?

Answer 15

Increasing complexity
High density
Critical interference between electrical and electronic systems

Question 16

What changes the question of if a wire will fail to when it will fail?

Answer 16

Effects of aeging

Question 17

What approach is required for dealing with wires?

Answer 17

A proactive approach to mitigate the problems caused by faulty wiring, and detecting the issues before they occur.

Question 18

What could indicate wiring problems?

Answer 18

Un-commanded inputs
Transient or intermittent failures
CND write ups
Ticking faults

Question 19

What could be the cause of wires failing?

Answer 19

Age
Poor maintenance
Material properties
Exposure (elements, dangerous solutions, etc.)

Question 20

What are the main conductors in wires?

Answer 20

Copper
Copper alloy
Aluminium

Question 21

What plate coatings are typically used for wires?

Answer 21

Silver or nickel

Question 22

What type of material is used for insulation?

Answer 22

Dielectric

Question 23

How could polyvinyl chloride insulation be identified and what are its issues?

Answer 23

Identified by being thick and heavy

Easily chafes, highly flammable, produces dangerous amounts of smoke when burnt

Question 24

Why was Kapton better than polyvinyl chloride?

Answer 24

Lighter, thinner, better dielectric properties?

Question 25

What issues did Kapton have?

Answer 25

Hard
Rapidly ages
Abraded other wire types
Once inner wires were exposed, moisture induced arcing

Question 26

What was the benefit of MIL-W-81044?

Answer 26

Better fluid resistance

Question 27

What was the problem facing MIL-W-81044?

Answer 27

Premature breakdown

Question 28

What were the problems for Tefzel?

Answer 28

Became soft at high temperatures, easily burned, and produced large amounts of smoke.

Question 29

What materials make up TKT?

Answer 29

Composite of Teflon and Kapton

Question 30

What are the main benefits of TKT?

Answer 30

Resistance to high heat
Little smoke produced when burned
Superb abrasion and insulation protection
Lightweight

Question 31

What standard is TKT the only product to meet?

Answer 31

FAA standard FAR25

Question 32

What happens when insulation dries out?

Answer 32

Becomes brittle forming cracks exposing the conductor

Hairline fractures

Question 33

What environmental factors can affect wire deterioration?

Answer 33

Extreme temps (hot and cold)
Water, salt and other marine environmental damage
Contamination from aircraft fluids
Chafing caused by aircraft vibration

Question 34

What makes the wire chafing worse?

Answer 34

Hard wires like Kapton to soft wires

Question 35

What can hairline fractures in insulation lead to?

Answer 35

Ingress of water and other fluids that could lead to micro discharges of current through the cracks to surrounding wires or structure.
Also known as a ticking fault

Question 36

Why are wire groups and bundles tied up?

Answer 36

To make installation, inspection, and maintenance easier

Question 37

What sort of wire damage does tying avoid?

Answer 37

Chafing

Equipment operation

Question 38

What is used for tying wire looms together?

Answer 38

Nylon
Waxed cotton
Fibreglass lacing cord

Question 39

What precautions must be heeded when tying wire looms together?

Answer 39

8 inch intervals between ties, 2 inch in high vibration areas
Tight but not crushing or deforming wires
1 foot intervals between clamp and ties
New wires must be at least supported by the clamps
No ties on conduit wires

Question 40

What area would wire ties not be used?

Answer 40

Fuel tanks

Question 41

What method is there to tie looms?

Answer 41

Clove hitch and square knot
Optional tie
Clove hitch and square knot to secure

Question 42

What is allowed for tying wire looms?

Answer 42

Single tying closed with two counter twisted knots

Optional tie for sloppy areas by passing loop through bundle before making the clove hitch

Question 43

How many layers of tape is required when tying wires to a single leg connector clamp

Answer 43

2

Question 44

How could you protect against breakouts and chafing?

Answer 44

Installing additional ties with either sleeping or tape to keep any break outs smooth before clamping

Question 45

What areas can plastic ties not me used?

Answer 45

Unpressurised
High vibration
High temperature

Question 46

Can plastic ties be used on fly by wire aircraft?

Answer 46

No

Question 47

What types of wires and cables can’t have plastic ties?

Answer 47

Wires larger than 10 AWG
With aromatic polyamide (Kapton) unless tape is on first
With coaxial cables

Question 48

Can plastic ties be installed by hand, if not what is used then?

Answer 48

No

A hand tool needs to be used.