7.7 Electrical Wiring Interconnection Flashcards
What is required for aircraft defects outside of a component/LRU failure?
Wiring checks must be carried out to troubleshoot or locate faults in the system.
What must be done when new wiring circuits are installed?
Installations must be inspected and undergo circuit tests to ensure system integrity and reliability.
What are the normal wiring checks?
Visual inspection, continuity testing, insulation resistance testing, bonding testing.
What must be done after completing all tests on wiring?
Installations must be inspected to ensure all connections are secured and that test equipment has been removed.
What does continuity testing verify?
It verifies that electrical connections are configured according to the wiring diagram.
How is a continuity test typically performed?
Using a multi-meter set to the ohms range or a simple lamp and battery.
What information does a continuity test provide?
- There is an electrical link between designated points. 2. The resistance of that link is within a specified value.
What is a warning associated with continuity testing?
Never apply power to a circuit when using continuity test equipment to avoid damage and injury.
What is the purpose of insulation testing?
To measure the resistance within wires and motor windings to identify current leakage and faulty insulation.
What is the typical resistance value allowed for single wires during insulation testing?
A minimum of 5 megohms.
What must be done before performing an insulation test?
All switches in the circuit must be ‘ON’ and all ancillary equipment must be disconnected.
What is the difference between bonding and grounding?
Bonding eliminates potential differences between components, while grounding provides a path for discharging static electricity.
What are the three main types of bonding?
Equipment bonding, metallic surface bonding, static bonding.
What is the resistance requirement for static bonding on larger objects?
A resistance of less than 1 ohm when clean and dry.
What should be inspected during bonding inspection?
Arcing, conduit bond, corrosion, freedom of movement.
What dimensions are subjected to appreciable electrostatic charging?
3 in² and a linear dimension over 3 in.
What is required for objects subjected to electrostatic charging?
They must have a mechanically secure electrical connection to the aircraft structure of sufficient conductivity to dissipate possible static charges.
What resistance ensures dissipation of static charges on larger objects?
A resistance of less than 1 ohm when clean and dry.
What is permissible for connecting smaller objects to airframe structures?
Higher resistances are permissible.
What should be inspected for bonding?
Arcing, conduit bond, corrosion, freedom of movement.
What should be checked if there is evidence of electrical arcing?
Check for intermittent electrical contact between conducting surfaces.
How must metallic conduits be bonded?
Must be bonded to the aircraft structure at each terminating and breakpoint.
What must bond connections be free from?
Corrosion.
How should bonding jumpers be installed?
In a manner that does not interfere with the operation of movable components.
What type of screws must not be used for bonding?
Self-tapping screws.
What is the maximum resistance for exposed conducting frames or parts?
Less than 2.5 mΩ to the structure.
Where must bonds be attached?
Directly to the basic aircraft structure.
What must bonds ensure?
That the structure and equipment are electrically stable and free from hazards.
What must electrical bonding conform to?
The manufacturer’s specifications.
What should be used when bonding aluminium or copper to dissimilar metallic structures?
Appropriate washers.
What must be performed after grounding and bonding mechanical connections?
Measurements to determine if resistance values meet basic requirements.
What is the purpose of a bonding tester?
To measure low resistance and the resistance of bonding or earthing systems on aircraft.
What is Class A in aircraft electrical bonds?
Refers to antenna installation with resistance less than 2.5 mΩ.
What does Class C describe?
The current path return ensuring no excessive voltage drop.
What does Class H protect against?
Shock hazard with resistance less than 100 mΩ.
What is the resistance requirement for Class L bonds?
Must be less than 0.05 Ω for lightning protection.
What does Class R ensure?
A low-impedance path (less than 2.5 mΩ) from equipment to aircraft structure.
What is the resistance requirement for Class S bonds?
Must be less than 1.0 Ω for static discharge.
What is the four wire method used for?
Measuring low resistance values.
What does a bonding tester measure?
Current and voltage drop to calculate resistance.
What is the importance of the four wire method?
It measures voltage drop independently of test lead resistance.
What must be checked before carrying out a bonding test?
The state of the battery of the tester.
What must be removed before testing?
Protective treatments on the points to be tested.
What is the maximum resistance for bonding resistance between aircraft extremities?
Must not exceed 0.05 Ω on all-metal aircraft.
What must bonds to moving parts be made of?
Braid connected by bolts or clamps.
What is the maximum resistance for flexible fuel pipes?
Must not exceed 0.025 Ω per foot length or 0.05 Ω, whichever is greater.
What are grounding and earth points?
Places where AC and DC electrical systems find their respective earth return paths.
What must not be connected to the same earth post?
AC neutral wires and DC earth wires.
What tests must be done when earth posts or terminal blocks are fitted or replaced?
A bonding test and a millivolt drop test.
What is the purpose of the corrosion tag or plate in earth post assemblies?
To prevent electrolytic action between the base of the assembly and the airframe structure.
What is the purpose of crimps and crimping tools?
The purpose of crimps and crimping tools is to ensure a consistent crimp and to test the crimp strength and the strength of the seated contact within the connector.
What is wire stripping?
Wire stripping is a critical primary process associated with crimping, involving the removal of insulation from wires to prepare them for crimping.
What are the types of wire stripping tools?
The types of wire stripping tools include Single Blade, Double Blade, and Thermal tools.
What is the preferred wire stripping tool?
The preferred wire stripping tool is the Double Blade.
What are the common hand crimping tools?
Common hand crimping tools include M22520 series crimp tools, Aircraft Marine Products AMP PIDG Crimp Tool, and AD1377 In-Line Sealed Splice Crimp Tool.
What is a crimped connection?
A crimped connection is one in which a cable conductor is secured by compression to a termination, ensuring close contact between the metals.
What are the steps in the crimping process?
The steps in the crimping process include selecting the correct tools, stripping the wire, crimping the contact, and inspecting the connection.
What is the function of the self-locking ratchet in crimping tools?
The self-locking ratchet prevents the tool from opening until the crimp sequence is complete.
What happens if the wrong stripping tool is used?
Using the wrong stripping tool can lead to a reduction in current-carrying capacity, insulation protection, and unacceptable mechanical or electrical characteristics.
What are the types of wire strippers commonly used in aviation?
The commonly used wire strippers in aviation are Single Blade and Double Blade.
What is the function of the M22520 series crimp tools?
The M22520 series crimp tools are high precision hand-operated tools used for crimping a wide range of contacts.
What is the significance of the turret head on crimping tools?
The turret head positions the contact correctly for crimping and accommodates different sizes of contacts.
What wire barrel sizes does the M22520/2-01 Crimping Tool accommodate?
The M22520/2-01 Crimping Tool accommodates contacts with wire barrel sizes 20 through 32.
How is the contact crimped using the M22520/2-01 Crimping Tool?
The contact is crimped by the creation of four sets of double impressions caused by the closure of the four indenters.
What type of positioner does the M22520/2-01 Crimp Tool use?
The M22520/2-01 Crimp Tool uses a bayonet quick release lock positioner.
What is a key difference between the M22520/2-01 and M22520/1-01 Crimp Tools?
The main difference is the turret head, which is now called a positioner in the M22520/2-01.
What should you not do with crimping tools?
Do not disassemble any crimping tools or attempt to adjust them.
What is the purpose of a ‘GO/NO-GO’ gauge?
The ‘GO/NO-GO’ gauge checks for proper calibration of the crimping jaws.
What color indicates the ‘NO-GO’ end of the gauge?
The ‘NO-GO’ end of the gauge is colored red.
What color indicates the ‘GO’ area of the gauge?
The ‘GO’ area of the gauge is colored green.
What must be checked before using any crimping tool?
The calibration tag must be checked to ensure it is still in date.
What is the significance of the diameter size in contacts?
Diameter sizes are standard and follow the same thickness measurement as wire ‘American Wire Gauge’ (AWG).
What is crimping?
Crimping is a process where deliberate distortion of the terminal shank is used to secure the terminal to the conductor.
What are PIDG terminal lugs?
PIDG terminal lugs are manufactured by Aircraft Marine Products (AMP) and are usually of the Pre-Insulated Diamond Grip type.
What is the function of the Certi-crimp ratchet?
The Certi-crimp ratchet ensures the bottoming of the die jaws before they can be opened again.
What does the insulation adjusting pins feature allow?
It allows for variation in insulation diameter and wear in the tool.
What does the colour coding on AMP crimping tools indicate?
The colour coding indicates the size range of the wire gauge.
What is the procedure for crimping AMP terminal lugs?
Select the correct terminal, check the tool, insert the wire, and squeeze the handles until the ratchet releases.
What is the importance of the inspection window in crimping?
The inspection window allows visibility of the conductor strands to ensure proper insertion.
What is a dual crimp?
A dual crimp refers to the crimping of both ends of a splice.
What is the AMP 59250/59275 Portable Crimping Tool used for?
It is used for crimping terminal lugs and in-line splices onto the wire.
What does the insulation crimp adjustment indicator do?
It controls the crimp height of the insulation barrel.
What are the features of the Certi-Crimp hand crimping tool?
The Certi-Crimp hand crimping tool features a ratchet control for complete and consistent crimping, a locator, a quick take-up trigger, and colour-code information.
What happens when the ratchet is engaged on the Certi-Crimp tool?
Once engaged, the ratchet will not release until the tool has fully cycled.
What is the design feature of the Certi-Crimp tool’s ratchet?
The crimping dies bottom before the ratchet releases, ensuring maximum electrical and tensile performance of the crimp.
How do you adjust the insulation crimp on the tool?
Loosen the insulation adjustment locking screw, turn the indicator to Position 4, and perform a crimp.
What should you do if the wire pulls out after crimping?
Set the insulation adjustment indicator to the next tighter position and repeat the crimping process.
What is the procedure for using the crimping tool?
Open crimping dies, place the terminal lug in the dies, insert stripped wire, press the quick take-up trigger, and close handles until the ratchet releases.
What should you visually inspect on the crimping tool?
Check for missing parts, the return action of the spring-loaded handles, and the condition of die closure surfaces.
What is the purpose of the AD1377 crimp tool?
The AD1377 crimp tool is designed for environmental sealed splices, providing optimum tensile strength and insulation integrity.
What should you observe when positioning the wire in the butt splice?
Ensure the end of the conductor is visible in the inspection hole, does not overlap the wire stop, and the insulation is not in the crimp barrel.
What is the procedure for crimping with the M22520 series tools?
Strip wire insulation, check tool calibration, insert terminal lug, squeeze handles, insert stripped wire, and squeeze until the ratchet releases.
What types of dies are available for the M22520 series crimp tools?
Hexagonal crimp dies in various combinations for insulated and uninsulated terminal lugs, wire splices, and end caps.
What is the purpose of Hydraulic hand tool PN 59974-1?
It is designed for crimping the terminals and splices for wire sizes from AWG 2 to 8 with different dies fitted.
What is an example of usage for the Hydraulic hand tool PN 59974-1?
Main generator cables, although these generally come supplied with terminal lugs fitted.
What are the main components of the Hydraulic hand tool PN 59974-1?
It has a stationary lever and a movable lever.
How does the crimping process work with the Hydraulic hand tool PN 59974-1?
The levers are compressed to pump hydraulic fluid behind the ram, moving it forward to close the dies.
What happens after the crimping is complete?
The movable lever is turned to depress the plunger, and the moving die retracts to its original position.
What is the part number of the crimping die used with the tool?
Each die has its own part number, for example, 48755-1.
What is the first step in die insertion for the crimping tool?
Pull out the latch pin and open the yoke.
What should be done before inserting dies into the crimping tool?
Loosen the socket head cap screws holding the insulation crimping section of dies in place.
How do you insert the stationary die into the crimping tool?
Insert the stationary die (with large shank) into the yoke and tighten the setscrew.
What is the adjustment process for insulation crimping?
Adjustments are made by moving a pin key to set the insulation crimping section of the die to loose, medium, or tight positions.
What should be done if the insulation crimp does not grip or support wire insulation?
Loosen the socket head cap screws and set the pin keys to the medium position, then repeat the crimping process.
What is the first step in the crimping procedure?
Strip the wire to dimensions as per SWPM or ESPM.
How should the terminal be positioned in the dies?
The bottom of the terminal tongue must face the stationary die and the terminal wire barrel must rest against a spring-loaded locator.
What should be done after placing the terminal in the dies?
Close the yoke and insert the latch pin.
What indicates that the crimp is complete?
An audible ‘pop’ when the dies have bottomed.
What should be done if the terminal sticks in the die after crimping?
Apply a rocking motion to remove the die.
What should be visually inspected after crimping?
Verify that all retaining pins are in place and inspect the head assembly for any damage.
What are typical die damages to look for?
Inspect for flattened, broken, pitted, or chipped conditions on the die closure surfaces.
What is the purpose of the AMP 69120 Series electric hydraulic pump?
It provides the power needed for crimping terminals and splices onto large wire sizes.
What are the voltage specifications for AMP 69120-1 and AMP 69120-2?
AMP 69120-1 is for 115 VAC and AMP 69120-2 is for 220 VAC.
What is the function of the multi-directional valve in the hydraulic crimp kit?
It allows for more than one crimping head to be operated from the pump.
What is the first step to use the handle control?
Attach the hose assembly to the pump.
What should be done before crimping a terminal or splice?
Plug the power cord of the pump into a properly grounded outlet.
What is the function of the hydraulic crimp head 1752787-1?
It accepts interchangeable die sets for a variety of heavy-duty terminals and splices.
What are the main components of the hydraulic crimp head 1752787-1?
A yoke, a removable latch pin, a cylinder, and a quick connect/disconnect coupler.
What should be verified before die insertion in the crimping head?
Ensure that the matched die set, terminal, and wire size are correct and compatible.
What is the last step in die removal from the crimping head?
Loosen the setscrew in the yoke and remove the stationary die.
What factors determine the quality of a crimp?
The quality of a crimp depends on its mechanical strength and electrical conductivity.
What methods are used to check and test crimped joints?
Methods include Visual Inspection, Tensile Test or ‘Pull Test’, and Volt Drop Test.
Why are crimped joints important in aircraft systems?
Crimped joints need to be structurally strong to extend and preserve the airworthiness of the aircraft.
What is the first step in ensuring a proper crimp?
A visual inspection is carried out to verify that the correct crimp procedure has been followed.
What does a tensile test ensure?
A tensile test ensures that the terminal meets required test criteria and that the contact is properly seated.
What checks are performed after crimping?
Continuity and insulation resistance checks are conducted prior to re-connection and installation.
What must be ensured during a visual inspection?
The crimp must be integral to the wire with no obvious defects or faults.
What is the consequence of over-crimping?
Over-crimping reduces the circular area of the conductor and increases electrical resistance.
What are the rules for inspecting a crimp?
The crimp must have a depth mark, the conductor must be fully inside the barrel, and the insulation must be outside.
What is a Volt Drop Test?
A Volt Drop Test measures the resistance within the crimped joint using a voltmeter.
What is the purpose of calibration for crimping tools?
Calibration ensures the tool meets specific manufacturer requirements and is safe to use.
What is the Pull and Break test method?
The Pull and Break test applies increasing axial force until the terminal and wire separate or the wire breaks.
What should be checked during the visual inspection of contacts?
Check that crimp indentations are in the correct location and that the insulation is properly stripped.
What is the inspection criteria for PIDG Terminal Lug/Splice?
Ensure crimp indent is centered, terminal lug is not cracked, and conductor extends beyond the barrel.
What should be done if a connection is found defective?
Cut off the defective connection and remake it using a new terminal lug.
What are electric connectors designed for?
Electric connectors are designed in many sizes and shapes to facilitate the installation and maintenance of electric circuits and equipment in aircraft.
What are the main parts of a connector assembly?
A connector assembly consists of two main parts: the plug and the receptacle.
What do contacts in a connector consist of?
Contacts consist of pins and sockets.
What is preserved within a connector when no contacts are fitted?
An environmental seal is preserved within the connector, using fillers or blanking fillers.
How are the plug and receptacle configured in terms of contacts?
Depending on the installation configurations, the plug has sockets and the receptacle has pins.
What is the function of pins and sockets in connectors?
Pins and sockets, known as contacts, connect to individual wires that make up the circuit.
What design feature helps prevent shorting of contacts during reassembly?
The receptacles are of a scoop proof design.
What are the two basic types of contact retention in aircraft connectors?
The two basic types are front release and rear release.
How are front release contacts removed?
Front release contacts are removed using an extracting tool inserted from the front, which pushes the pin or socket out the back.
What is the procedure for removing rear release contacts?
The contact removal tool is inserted from the back to release the contact retention clip.
What is the purpose of the removal and insert tools being colour coded?
The tools are colour coded for size, typically: yellow for AWG 12, blue for AWG 16, and red for AWG 20.
What is a typical feature of front release connectors?
They usually have a contact position identification on the mating end.
What is the procedure for front release contact insertion?
Slip the insertion tool over the wire, align it with the grommet, and guide the contact through the grommet hole.
How are rear release connectors typically identified?
They are usually identified with a blue band around the shell or a blue line on the back shell.
What is the advantage of rear release connectors?
The contacts are less susceptible to damage during removal.
What is the procedure for rear release contact removal?
Slip the white removal tool around the wire and gently insert it into the grommet to release the retaining clip.
What is the procedure for rear release contact insertion?
Press the wire into the coloured slot, hold the connector, and insert the contact into its cavity.
How is the retention of inserted contacts tested?
By gently pulling on the wire or checking with a retention test tool.
What tool is used for unwired contact extraction?
An unwired contact removal tool is used.
What is the procedure for terminal block contact insertion?
Start the wired contacts into the appropriate sockets by hand, then use the approved tool to insert them.
What is the procedure for terminal block contact removal?
Remove any support ties, use the approved extraction tool, and slide it into the cavity over the rear of the contact.
What is the purpose of aircraft co-axial cables?
Aircraft co-axial cables are used for the same purpose as that of a waveguide, but operate at lower frequencies.
What can happen if there is damage to co-axial cables in RF applications?
Cable damage can be catastrophic due to reflected waves that can return to the transmitter if a short circuit or open circuit exists.
How does the analogy of a rope relate to co-axial cables?
A wave passes along the rope to the attachment point and then back to the source, similar to how waves travel in co-axial cables.
What happens if the characteristic impedance of a co-axial cable is not matched?
Reflected waves can return to the source, and any corrosion or damage can cause changes to the impedance, affecting the Voltage Standing Wave Ratio (VSWR).
What type of cable is widely used in ‘New Generation’ aircraft?
Fibre-optic cable is widely used, enabling high-speed data transfer rather than SHF/EHF radar frequency.
What is the frequency range for co-axial cables in aircraft applications?
Co-axial cables are used for frequencies below 5000 MHz (5 GHz); above 5 GHz, waveguides are used.
What is the dielectric material in modern flexible co-axial cables?
Flexible co-axial cables use foam or polyethylene as the dielectric material.
What are the four types of transmission line losses?
Transmission line losses can be of four types: copper, dielectric, radiation, and induction losses.
What are copper losses in co-axial cables?
Copper losses are power losses (I²R) due to the resistance of the copper conductor and the skin effect.
What causes dielectric losses in co-axial cables?
Dielectric losses result from heating the dielectric material due to disturbances in electron orbits caused by potential differences.
What are radiation losses in co-axial cables?
Radiation losses occur when some electromagnetic energy escapes the cable, leading to signal attenuation and potential interference.
How can induction losses be minimized in co-axial cables?
Induction losses can be minimized through effective shielding between the inner and outer conductors.
Why is correct termination important in co-axial cables?
Correct termination is vital to avoid conditions that increase losses or produce reflected or standing waves in the cable.
What materials are used for the inner conductor of co-axial cables?
The inner conductor can be solid or stranded copper wire, and may be plain, tinned, silver plated, or gold plated.
What is the structure of a co-axial cable?
A co-axial cable consists of an inner conductor, dielectric insulation, an outer conductor, and a protective insulator jacket.
What precautions should be taken when installing co-axial cables?
Care must be taken to avoid clamping too tightly, bending sharply, or causing damage during maintenance.
What is the minimum bend radius for co-axial cables?
The minimum bend radius must be six times the diameter of the cable to prevent kinking.
What types of connectors are used with co-axial cables?
Co-axial cables are typically connected using Bayonet Nut Coupling (BNC) and Threaded Nut Coupling (TNC) connectors.
What tools are used for crimping co-axial connectors?
Co-axial connectors are typically crimped using Open Frame crimping tools M22520/5-01 (HX4) and M22520/10-01 (HX3).
What are the stages of co-axial cable preparation?
The stages include removal of the outer jacket, braid cut to length, dielectric cut to length, and inner conductor cut to length.
What should be inspected before crimping a co-axial connector?
Inspect the cable for dents, nicks, and crush damage, and ensure all components are at hand.
What is the importance of following assembly directions for co-axial connectors?
Following assembly directions is crucial to avoid trouble and ensure proper connections.
What visual confirmations are important when examining a co-axial crimped end?
Check for correct crimp form, no loose strands of braiding, no exposed conductor strands, and no damage to the dielectric or inner conductor pin.
What is the first step in crimping a co-axial cable?
Crimp the Centre Pin onto the Centre Conductor.
What is the second step in crimping a co-axial cable?
Crimp the Full length of the Ferrule.
What should be visually confirmed when examining a co-axial crimped end?
Correct form of the HEX crimp, no loose strands of braiding, no exposed conductor strands, no obvious damage or mis-shaping to the di-electric, no obvious damage to the inner ferrule, no obvious damage to the inner conductor pin, the inner conductor pin is straight, no obvious damage to the Threaded Portion (TNC), no obvious damage to the Bayonet (BNC), and no obvious damage to the outer sheath.
What are the co-axial cable testing procedures upon installation?
Continuity for each of the two conductors, insulation resistance checks, Time Domain Reflectometer (TDR) testing, characteristic impedance, open circuit conditions, and short circuit conditions.
What is the purpose of the Time-Domain Reflectometer (TDR)?
To characterize and locate faults on a transmission line including co-axial cables.
How does the TDR detect problems in the cable?
It is sensitive to impedance changes and displays these changes as variations in impedance along the cable.
What should you do before using the TDR?
Familiarize yourself with the test set, read the operating manual and AMM procedure fully, set up the required pulse width, ensure proper connection to the cable under test, and disconnect the other end of the co-axial cable.
What does a consistent pulse energy throughout the cable indicate?
The cable is in good condition, identified as being open at the end of the cable.
What happens if the TDR detects changes in impedance?
The pulse is reflected to the TDR, which can be seen as different waveforms.
What must be ensured for the electric wiring in an aircraft?
The electric wiring must be properly selected, installed, and maintained to ensure the safety of the aircraft.
What conditions affect the selection of aircraft electric wire?
Design temperature, flexibility requirements, abrasion resistance, strength, insulation, electrical resistance, weight, applied voltage, and current flow.
What is typically referred to as a ‘wire’ in aircraft wiring?
Any type of single conductor surrounded by insulation.
What type of conductor is most commonly used in aircraft wire?
Most aircraft wire is made with a stranded copper conductor.
What is the advantage of using stranded or twisted wire?
It increases the flexibility of the conductor, thus decreasing the chance of fatigue failure.
What is the primary disadvantage of using a cable in aircraft wiring?
The inability to repair or replace a single wire.
What are ‘Airframe’ cables designed for?
‘Airframe’ cables are intended to be robust enough for ‘Open’ airframe wiring and general wiring of power plants.
What is the term used in the USA for cables that can be used in protected areas of wiring?
‘Hook Up’ is commonly used in the USA for such cables.
What is the purpose of thin wall cables in aircraft?
To reduce weight while still meeting required current carrying capability and environmental protection.
What is the difference between fire-resistant and fireproof cables?
Fire-resistant cables retain insulation for five minutes in fire, while fireproof cables operate for fifteen minutes in designated fire zones.
What are multicore screened and jacketed cables?
Cables that can be supplied in a multicore form, twisted together, and can be jacketed or screened.
What is the purpose of shielded cables?
To minimize interference with aircraft instrumentation caused by magnetic fields.
What is a data bus cable designed for?
Data bus cables are designed to specific requirements that do not generally allow for replacement by any other type.
What do power feeder cables provide?
They provide high load outputs from the aircraft’s generators to the electrical distribution system.
What is the purpose of a wire identification system?
To identify wires and cables in modern aircraft for easy tracking and maintenance.
What is ‘series coding’ in cable coding?
A method of coding wires and cables that conforms to the ATA 100 specification.
What must be done to cables that have been hot-stamped?
They must undergo stringent insulation testing.
What does the circuit function letter in wire coding identify?
It identifies the wire with a particular system function, such as D for General instruments or G for Landing gear.
What do the first four digits of the wire code represent?
The first four digits of the code is the wire number prefix, identifying the aircraft system to which the cable is connected.
How is a wire number structured?
A wire number consists of a maximum of five digits, separated from the ATA number prefix by a dash.
What is the purpose of the wire segment letter?
A letter is used to differentiate between two wires that are permanently connected, with segments lettered in alphabetical sequence.
What letters are not used for wire segment identification?
The letters ‘I’ and ‘O’ are not used.
How are double letters used in wire segment identification?
Double letters such as ‘AA’, ‘AB’, ‘AC’, etc., are used when more than 24 segments are required.
What does the wire gauge indicate?
The wire gauge indicates the American Wire Gauge (AWG) size of the wire or cable.
What suffix identifies a ground wire?
The letter ‘N’ is used as a suffix to identify a segment of a wire or cable that is part of the ground network.
What suffixes are used for three-phase AC power?
The phase letters ‘A’, ‘B’, and ‘C’ are used as suffixes for wire segments carrying three-phase AC power.
What is the significance of the Boeing Wiring Diagram Manual (WDM)?
The WDM is a collection of diagrams, drawings, and wire lists that define the wiring and hook-up of associated equipment installed on Boeing aeroplanes.
How is a wire bundle number formatted?
Each wire bundle is given an item number beginning with ‘W’, derived from the wire bundle drawing number.
What does the ‘TY’ field represent in wire identification?
The ‘TY’ field is a two-character identifier for the type of wire used.
What is the purpose of the family code in wire identification?
The family code denotes that some wires are physically related to each other, such as being twisted together.
What is the maximum permissible bend radius for a wire bundle?
The minimum bend radius of a bundle is five times the outside diameter.
What precautions should be taken for cable support?
Wires and cables must be supported by suitable clamps or grommets at intervals of not more than 61 cm (24 in).
What should be done with unused wires?
Unused wires must be dead-ended, tied into a bundle, and secured to a permanent structure.
What is the requirement for the breakout from the parent bundle?
The breakout must curve smoothly from the bundle in the same plane as the parent bundle centreline.
What should the breakout not do when exiting the parent bundle?
The breakout must not lay across any wires when exiting the parent bundle or loom, as vibration can cause chaffing of the wires, which could lead to a system failure.
How must the loom be tied around the breakout?
The loom must be tied no more than 2.5 cm (1 in) on either side of the breakout to give full support and additional strengthening to both loom and breakout.
What should be done with unused wires?
Ensure that unused wires are dead-ended, tied into a bundle, and secured to a permanent structure.
How should each wire be prepared?
Each wire must have strands cut even with the insulation and a pre-insulated closed-end connector, or a 2.5 cm (1 in) piece of insulating tubing placed over the wire, with its end folded back and tied.
What is the identification requirement for wires and cables?
Ensure that all wires and cables are identified properly at intervals of not more than 38 cm (15 in).
How should co-axial cables be identified?
Co-axial cables are identified at both equipment ends.
What materials should not be used for primary support?
Do not use tape, tie straps, or cord for primary support.
What types of tape should not be used?
Do not use tapes that dries out in service or that produce chemical reactions with wire or cable insulation or absorb moisture.
What should not be used as a fill for clamps or adapters?
Do not use moisture-absorbent material as a ‘fill’ for clamps or adapters.
What is the guideline for continuous lacing?
Continuous lacing (15 cm (6 in apart)) is not used, except in panels and junction boxes where this practice is optional.
What should be done before replacing a wire?
When a repair or modification requires the replacement of a wire, the maintenance manual for that aircraft must first be reviewed to determine if the Original Aircraft Manufacturer (OAM) has approved any substitution.
What conditions require wiring replacement?
Wiring must be replaced with equivalent wire when it has defects such as chafing, fraying, brittle insulation, weather-cracked insulation, exposure to electrolyte, overheating, saturation with lubricants, crushing, or evidence of breaks.
What should be checked for wiring that shows evidence of overheating?
Check wiring that shows evidence of overheating to find the reason for the increased temperatures.
What is the requirement for splices in wiring?
Sections of wire in which splices occur at less than 3 meter (10 ft) intervals unless specifically authorised due to parallel connections, locations, or inaccessibility.
How should wiring or co-axial cables be identified when replacing them?
When replacing wiring or co-axial cables, identify them properly at both equipment power source ends.
