40 Questions
What is the recommended insulating sleeve length for a 2 AWG wire splice?
2-13/32 inches
Why should splicing of electrical wire be kept to a minimum?
It is subject to extreme vibrations
What type of splice connector is preferred for use in aircraft?
Self-insulated splice connector
What is the maximum number of splices allowed in one wire segment between connectors?
One splice
What is the purpose of covering a non-insulated splice connector with plastic sleeving?
To insulate the splice
Why should splicing of individual wires in a group or bundle require engineering approval?
To ensure the splice is located for periodic inspection
When is it acceptable to have multiple splices in one wire segment?
All of the above
What is the recommended approach to splicing electrical wires in aircraft?
Minimize splicing and avoid it in locations subject to extreme vibrations
What is the characteristic of splice pre-insulation?
It extends over the wire insulation
What is the purpose of the colour-coding on splices?
To match the colour-coding of insulated copper terminal lugs
What is the approved tool for crimping M81824 environmental splices?
M22520/5 and M22520/10 crimp tools with appropriate dies
How many times must the crimping operation be performed for M81824 environmental splices?
Twice
Where should mount cable clamps be directly attached to?
Z members of the structure
What is the purpose of the inspection hole in the splice?
To check the wire ends after crimping
What type of bracket should be used when the structural member is angled?
An angle bracket with two mounting screws
What is the stripping length for #26 and #24 wires?
5/32
What is used to provide electrical and mechanical protection to uninsulated splices?
Heat-shrink tubing or transparent flexible sleeving
What is the primary consideration when selecting clamps for wire bundles?
A snug fit without pinching wires
What is the recommended test to ensure the clamp is secure on RF cables?
Apply a slight axial pull
What is the characteristic of uninsulated splices?
They are used for large copper wires
Why should metal clamps be avoided on coaxial RF cables?
They may distort the RF cable's original cross-section
What should be installed when there is less than 1 cm clearance between the bulkhead cut-out and the wire bundle?
A suitable grommet
Why should the attachment hardware of cable clamps be positioned above them?
To prevent the clamp from rotating due to wire bundle weight or chafing
What can be used to achieve a snug fit on wire bundles when required?
Electrical tape
What is a major concern when installing and maintaining coaxial cable?
Erroneous electronic equipment indications and interference
What is the recommended practice for routing coaxial cable around corners?
Use a minimum bend radius of 6 times the diameter of the cable
Why should cable ties not be used with coaxial cable?
They can crush the dielectric and damage the cable
What is the purpose of grounding the braided outer conductor of coaxial cable?
To protect electronic circuitry
Why is it important to support coaxial cable at regular intervals?
To prevent damage from being stepped on
What can happen if a coaxial cable becomes kinked or dented?
Electrical interference may occur
What should be done when installing coaxial cable?
Route the cable as directly and as short as possible
What can happen if the length of a coaxial cable is changed during maintenance?
The cable may malfunction or cause interference
At what maximum interval should wires and cables be supported by suitable clamps or devices?
24 in.
Why must metal stand-offs be used to maintain clearance between wires and structure?
To prevent damage to equipment shock mounts
What is the purpose of insulating tubing?
To protect wires and cables from abrasion
Why should wires and cables be routed carefully?
To prevent chafing against the airframe
What is the recommended way to secure insulating tubing?
Tying, tie straps or clamps
What is prohibited in place of stand-offs for maintaining clearance?
Insulating tubing
Why is it important to properly support wires and cables?
To prevent excessive movement in areas of high vibration
What should be done with wires and cables in junction boxes, panels, and bundles?
Properly support and lace them
Study Notes
Mounting Cable Clamps
- Mount cable clamps directly to Z members of the structure.
- Use an angle bracket with two mounting screws if the structural member is angled.
Cable Clamps on Wire Bundles
- Select clamps to achieve a snug fit without pinching wires.
- Ensure clamps do not allow the bundle to move through the clamp when a slight axial pull is applied.
Cable Clamps on RF Cables
- Ensure clamps fit without crushing the cable.
- Select clamps that are snug enough to prevent the cable from moving freely through the clamp but allow the cable to slide through the clamp when a light axial pull is applied.
Wire Bundles Near Bulkheads
- Install a suitable grommet if there is less than 1 cm (3/8 of an inch) clearance between the bulkhead cut-out and the wire bundle.
Clamp Installation
- Install clamps with their attachment hardware positioned above them, wherever practicable, to prevent rotation due to wire bundle weight or chafing.
Splicing
Splicing Procedure for M81824 Environmental Splices
- Crimp twice, once for each end of the splice.
- Strip wires according to the table below:
- #26 and #24: 5/32 inches
- #22 - #14: 7/32 inches
- #12 - #10: 5/16 inches
- Check that wire ends are visible through the inspection hole after crimping.
Splicing Large Copper Wires
- Use uninsulated splices for large copper wires (No. 8 through No. 4/0).
- Insulate splices with either heat-shrink tubing or transparent flexible sleeving after assembly.
General Requirements for Splicing
- Keep splicing to a minimum and avoid splicing in locations subject to extreme vibrations.
- Avoid splicing individual wires in a group or bundle without engineering approval.
- Use self-insulated splice connectors or non-insulated splice connectors with plastic sleeving.
Coaxial Cable Installation Precautions
- Install coaxial cables directly and as short as possible to minimize radio frequency interference (RFI) hazards.
- Ground the braided outer conductor at one or both ends to protect electronic circuitry.
- Avoid using cable ties, which can crush the dielectric and damage the cable.
- Route cables with a minimum bend radius of 6 times the diameter of the cable to prevent kinking.
Wire Support
- Support wires and cables at intervals of not more than 24 in. with suitable clamps, grommets, or other devices.
- Ensure supports do not restrict wires or cables in a manner that interferes with equipment operation.
- Use metal stand-offs to maintain clearance between wires and structure.
- Insulating tubing is secured by tying, tie straps, or clamps, but not used as an alternative to stand-offs for maintaining clearance.
Protection
- Route wires and cables to prevent chafing against the airframe or other components.
Learn about the proper installation and selection of cable clamps, including mounting considerations and wire bundle fitting. Ensure secure and damage-free connections.
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