Aircraft Electrical Circuit Testing

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Questions and Answers

What type of BNC connector is used as an example for assembling coaxial cable?

Push-type connector

Clamp-type connector (correct)

Twist-type connector

Screw-type connector

Why is it important to comb out the shield carefully?

To remove the outer jacket

To avoid nicking the shield (correct)

To avoid breaking the centre conductor

To strip the dielectric

What is the purpose of wrapping thin pressure tape around the shielding?

To strip the dielectric

To expose the centre conductor

To remove the outer jacket

To form a cone with the narrow end towards the conductor (correct)

What is the recommended trim length for the shield?

3/32 in. Signup and view all the answers

What is the purpose of the sleeve clamp in the assembly process?

To make a tight seal with the grooved gasket Signup and view all the answers

What is added when assembling to RC-62/U or 71/U coaxial cables?

Insulation bushing Signup and view all the answers

What is the primary purpose of bonding in an aircraft?

To protect aircraft and personnel against hazards from lightning discharge Signup and view all the answers

What is the main difference between bonding and grounding?

Bonding is used for return of current, while grounding is used for static charge prevention Signup and view all the answers

What type of testing is used to check for electrical connections between conducting objects?

Bonding testing Signup and view all the answers

What is the purpose of functional testing in circuit testing?

To check the functionality of the system Signup and view all the answers

What is the purpose of insulation resistance testing in circuit testing?

To check the insulation resistance of the system Signup and view all the answers

What should be done after completion of all circuit tests?

The installations should be inspected to ensure that all connections have been re-made and secured Signup and view all the answers

What is the purpose of the petroleum-based abrasive compound in the aluminium terminal lugs?

To remove the oxide film from the aluminium and prevent oxide from reforming Signup and view all the answers

What should be used to install MS aluminium terminal lugs?

MS25441 tool Signup and view all the answers

What is the purpose of insulating the aluminium terminal lugs after assembly?

To provide mechanical and electrical protection at the connection Signup and view all the answers

What is the primary difference between uninsulated splices and insulated splices?

Uninsulated splices are used for larger wire sizes Signup and view all the answers

What should be done if a defective connection is found during a visual inspection?

Cut off the defective connection and remake it using a new terminal lug Signup and view all the answers

What is the purpose of the inspection hole in the M81824 environmental splice?

To check if the wire is visible Signup and view all the answers

What is the recommended stripping length for #22 to #14 wires?

7/32 inches Signup and view all the answers

What type of wire sizes are used for environmental permanent splices conforming to MIL-S-81824?

Small copper wire sizes No. 26 through No. 10 Signup and view all the answers

What should be examined during the inspection of crimped terminations?

The crimp indent centred on the terminal lug barrel Signup and view all the answers

What is used to insulate uninsulated splices after assembly?

Heat-shrink tubing or transparent flexible sleeving Signup and view all the answers

What is the significance of the color-coding of splices?

It is similar to the color-coding of insulated copper terminal lugs Signup and view all the answers

How many times must the crimping operation be performed for M81824 environmental splices?

Twice Signup and view all the answers

What is the main benefit of using stranded copper conductors in aircraft wiring?

Improved flexibility and reduced fatigue failure Signup and view all the answers

What is the primary purpose of coating aircraft wire with tin, silver, or nickel?

To prevent oxidation Signup and view all the answers

What is the main advantage of using aluminium wire in aircraft wiring?

Ability to carry large amounts of current for long distances Signup and view all the answers

What is the primary consideration when selecting wire insulation for an aircraft?

All of the above Signup and view all the answers

What is the main disadvantage of using cables in aircraft wiring?

Inability to repair or replace a single wire Signup and view all the answers

What is the term used to describe any group of two or more conductors separately insulated and grouped together by an outer sleeve?

Cable Signup and view all the answers

Study Notes

Circuit Testing

Circuit tests are essential for ensuring system reliability and include bonding testing, continuity testing, insulation resistance testing, and functional testing.
After completing all tests, the installations should be inspected to ensure that all connections have been re-made and secured, and that test equipment, tools, etc., have been removed.

Bonding and Grounding

Bonding means electrically connecting two or more conducting objects not otherwise adequately connected.
Grounding means electrically connecting a conducting object to a primary structure or earth electrode for return of current.
Bonding and grounding connections are made in aircraft for various purposes, including:
- Protecting aircraft and personnel against hazards from lightning discharge.
- Providing power current return paths.
- Preventing development of RF potentials.
- Protecting personnel from shock hazard.
- Providing stability and consistency of radio transmission and reception.
- Preventing accumulation of static charge.
- Providing fault current return paths.

Bonding of Aircraft Components

The main types of bonding are used to connect conducting objects and prevent electrical hazards.

Coaxial Cable Assembly Procedures

Remove 5/16 in. of the outer jacket, exposing the shield, and comb out the shield carefully to avoid breaking shield strands.
Strip dielectric to 3/16 in. from the edge of the jacket, exposing the centre conductor.
Disassemble the nut, grooved gasket, and sleeve clamp from the plug or jack body.
Taper the shield towards the centre conductor and wrap a piece of thin pressure tape around the shielding, forming a cone.
Slide the nut and gasket (V-groove away from nut) in that order over the tapered shield and onto the jacket.
Slide the sleeve clamp over the tapered shield until the inside shoulder of the clamp butts flush against the cut end of the jacket.

Inspection of Crimped Terminations

Examine the crimped connection carefully for:
- Crimp indent centred on the terminal lug barrel
- Indent in line with the barrel
- Terminal lug not cracked
- Terminal lug insulation not cracked
- Insulation grip crimped

EWIS Splicing Procedures

Environmental permanent splices conforming to MIL-S-81824 are used to join small copper wire sizes No. 26 through No. 10.
Splices are colour-coded in the same manner as insulated copper terminal lugs.
The M22520/5 and M22520/10 crimp tools with appropriate dies are the approved tools for crimping these splice sizes.

Aircraft Electrical Wiring

Several conditions must be considered when choosing an aircraft electrical wire, including design temperature, flexibility requirements, abrasion resistance, strength, insulation, electrical resistance, weight, and applied voltage and current flow.
The type of conductor and insulation necessary for a given installation is determined by these factors.
Aircraft wire is made with a stranded copper conductor, either seven or 19 strands for small wire and 19 or more for larger wire.
The use of stranded wire increases the flexibility of the conductor, thus decreasing the chance of fatigue failure.

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Description

Learn about the importance of circuit testing in ensuring system reliability in aircraft electrical circuits, including bonding, continuity, and insulation resistance tests.