View Latest Blog Entries
Close
Categories
Testing & Assessment Certification Standard & Regulation Aging Wires & Systems Maintenance & Sustainment Management Conference & Report Protection & Prevention Research Miscellaneous Arcing
Popular Tags
Visual Inspection High Voltage AS50881 MIL-HDBK MIL-HDBK-525 FAR AS4373 Electromagnetic Interference (EMI) Maintenance FAR 25.1707 Wire System Arcing Damage
All Tags in Alphabetical Order
2021 25.1701 25.1703 abrasion AC 33.4-3 AC 43 Accelerated Aging ADMT Aging Systems AIR6808 AIR7502 Aircraft Power System aircraft safety Aircraft Service Life Extension Program (SLEP) altitude arc damage Arc Damage Modeling Tool Arc Fault (AF) Arc Fault Circuit Breaker (AFCB) Arc Track Resistance Arcing Arcing Damage AS22759 AS22759/87 AS23053 AS29606 AS4373 AS4373 Method 704 AS50881 AS5692 AS6019 AS6324 AS81824 AS83519 AS85049 AS85485 AS85485 Wire Standard ASTM B355 ASTM B470 ASTM D150 ASTM D2671 ASTM D8355 ASTM D876 ASTM F2639 ASTM F2696 ASTM F2799 ASTM F3230 ASTM F3309 ATSRAC Attenuation Automated Wire Testing System (AWTS) Automotive Avionics backshell batteries bend radius Bent Pin Analysis Best of Lectromec Best Practice bonding Cable Cable Bend cable testing Carbon Nanotube (CNT) Certification cfr 25.1717 Chafing Chemical Testing Circuit Breaker circuit design Circuit Protection cleaning clearance Coaxial cable cold bend collision comparative analysis Compliance Component Selection Condition Based Maintenance Conductor Conductor Testing conductors conduit Connector Connector rating connector selection connector testing connectors contacts Corona Corrosion Corrosion Preventing Compound (CPC) corrosion prevention Cracking creepage D-sub data analysis data cables degradat Degradation Delamination Derating design safety development diagnostic Dielectric breakdown dielectric constant Dimensional Life disinfectant Distributed Power System DO-160 dry arc dynamic cut through E-CFR electric aircraft Electrical Aircraft Electrical Component Electrical Power Electrical Testing Electrified Vehicles Electromagnetic Interference (EMI) Electromagnetic Vulnerability (EMV) Electrostatic Discharge EMC EMF EN2235 EN3197 EN3475 EN6059 End of Service Life End of Year Energy Storage engines Environmental Environmental Cycling environmental stress ethernet eVTOL EWIS certification EWIS Component EWIS Design EWIS Failure EWIS sustainment EWIS Thermal Management EZAP FAA FAA AC 25.27 FAA AC 25.981-1C FAA Meeting failure conditions Failure Database Failure Modes and Effects Analysis (FMEA) FAQs FAR FAR 25.1703 FAR 25.1707 FAR 25.1709 Fault fault tree Fixturing Flammability fleet reliability Flex Testing fluid exposure Fluid Immersion Forced Hydrolysis fuel system fuel tank ignition Functional Hazard Assessment functional testing Fundamental Articles Fuse Future Tech galvanic corrosion Glycol Gold Gold plating Green Taxiing Grounding hand sanitizer handbook Harness Design harness protection hazard Hazard Analysis health monitoring heat shrink heat shrink tubing high current high Frequency high speed data cable High Voltage High Voltage Degradation HIRF History Hot Stamping Humidity Variation HV connector HV system ICAs IEC 60851 IEC60172 IEEE immersion insertion loss Inspection installation installation safety Instructions for Continued Airworthiness insulating material insulating tape Insulation insulation breakdown insulation resistance insulation testing interchangeability IPC-D-620 ISO 17025 Certified Lab ISO 9000 J1673 Kapton Laser Marking life limit life limited parts Life prediction life projection Lightning lightning protection liquid nitrogen lithium battery lunar Magnet wire maintainability Maintenance Maintenance costs Mandrel mean free path measurement mechanical stress Mechanical Testing MECSIP MIL-C-38999 MIL-C-85485 MIL-DTL-17 MIL-DTL-23053E MIL-DTL-3885G MIL-DTL-38999 MIL-E-25499 MIL-HDBK MIL-HDBK-1646 MIL-HDBK-217 MIL-HDBK-454 MIL-HDBK-516 MIL-HDBK-522 MIL-HDBK-525 MIL-HDBK-683 MIL-STD-1353 MIL-STD-1560 MIL-STD-1798 MIL-STD-464 MIL-T-7928 MIL-T-7928/5 MIL-T-81490 MIL-W-22759/87 MIL-W-5088 MIL–STD–5088 Military 5088 modeling moon MS3320 NASA NEMA27500 Nickel nickel plating No Fault Found OEM off gassing Outgassing Over current Overheating of Wire Harness Parallel Arcing part selection Partial Discharge partial discharge at altitude Performance physical hazard assessment Physical Testing polyamide polyimdie Polyimide-PTFE Power over Ethernet power system Power systems predictive maintenance Presentation Preventative Maintenance Program Probability of Failure Product Quality PTFE pull through Radiation Red Plague Corrosion Reduction of Hazardous Substances (RoHS) regulations relays Reliability Research Resistance Revision C Rewiring Project Risk Assessment S&T Meeting SAE SAE Committee Sanitizing Fluids Secondary Harness Protection separation Separation Requirements Series Arcing Service Life Extension Severe Wind and Moisture-Prone (SWAMP) Severity of Failure shelf life Shield Shielding Shrinkage signal signal cable Silver silver plated wire silver-plating skin depth skin effect Small aircraft smoke Solid State Circuit Breaker Space Certified Wires Splice standards Storage stored energy superconductor supportability Sustainment System Voltage Temperature Rating Temperature Variation Test methods Test Pricing Testing testing standard Thermal Circuit Breaker Thermal Endurance Thermal Index Thermal Runaway Thermal Shock Thermal Testing tin Tin plated conductors tin plating tin solder tin whiskering tin whiskers top 5 Transient Troubleshooting TWA800 UAVs UL94 USAF validation verification video Visual Inspection voltage voltage differential Voltage Tolerance volume resistivity vw-1 wet arc white paper whitelisting Winding wire Wire Ampacity Wire Bend Wire Certification Wire Comparison wire damage wire failure wire performance wire properties Wire System wire testing Wire Verification wiring components work unit code

7 tenets of aircraft wire systems installation

Protection & Prevention

There are a number of considerations when designing the installation of EWIS on aircraft wire systems. They include part selection, system integration, routing, safety and separation, regulation considerations, operational environments, maintenance, and obsolesces planning. In other words, a lot to consider. Back in 2004, Lectromec released, Ten commandments of Wire Maintenance. Below, Lectromec lists, the 7 tenets of wire system installation:

1. Above all else, prevent chaffing

This is one of the largest drivers for EWIS maintenance. The methods for preventing chaffing include proper separation distance from other components (particularly corners and edges) and use of primary and secondary harness support to prevent a single point failure from causing problems. Identifying and reducing chaffing locations is a good starting point for maximizing EWIS reliability.

2. Harnesses are not handholds nor should they be used as support for personal equipment

wire systems
Example of harness in wire systems

If a harness is in an area where maintenance is common, the harness should be covered and/or protected from human hands and equipment. Use of harnesses as grips and handholds, places strain on the harness and causes any number of problems including:

  • Breaking the conductor
  • Pulling the pin from the connector
  • Misalignment of clamps
  • Moving harnesses from identified critical clamp marker locations

3. Beyond handholds, keep harnesses away from humans

During normal operations, wiring should be routed and protected in such a way as to minimize the chance of accidental damage. This may mean that harnesses need to be routed in rigid conduits in some areas where other physical separation techniques are not available. There are obvious drawbacks to the use of conduits (e.g. difficult for maintenance to examine, concerns about chaffing at the ends, etc.), but they can provide the needed protection from personnel.

4. Moving parts are not your friend

Moving parts can pinch, crush, chafe, and cut wires. The moveable parts to consider include doors, landing gears, flight control surfaces, and mechanical cables. If the harnesses are routed nearby, it is necessary to maintain positive physical separation via standoffs or clamps. If the harnesses are attached to the moving component, it is necessary to include slack in the system and to design the flex points such that the harnesses are not pinched. Also, for all the parts of the mechanical movement range, consideration should be given to the minimum harness radius.

5. Hide from fluids

Electricity and fluids do not mix. Potential problems from exposure to fluids include:

  • Degradation of insulation
  • Shorting/arcing between damaged wires or wire to ground
  • Shorting/arcing at connectors
  • Contamination of connectors

It is important that the EWIS is protected along its length from exposure to fluids. These sources of fluids may come from leaking fuel or hydraulic lines, plumbing, or spillage from passengers/crew. If routed above these sources, the potential for exposure is limited. Where it is necessary to be routed below a potential fluid leak location, drip shields or umbrellas can be used to protect the wiring. Molded harnesses should be considered in areas that are regularly exposed to fluid and cannot be protected through other means. Additionally, addressing problems caused by fluids should include harness drip loops before connectors. This helps to prevent the ingress of fluids into the connector (see Lectromec’s In aerospace wire systems, how much slack should I give a wire? article for more information).

6. Hide from random physical damage

In areas of the aircraft where physical damage from debris is possible, such as in wheel wells, there needs to be a physical barrier for the EWIS components. The rocks and ice thrown into the wheel wells can damage unprotected EWIS.

7. Treat fiber optic cables carefully

When designing the installation of fiber optics cables, they should be routed in such a way as to prevent any loads (including stretching) on the cable or the terminations. Further, additional care should be taken to prevent flexing or crushing of the cable during the fabrication and installation process. This may require modification to procedures for shipping, storage, identification, and finally the installation/securing of the components in the aircraft. It should also be noted that additional support and routing considerations must be made for fiber optic cables. Ideally, fiber optic cables should be installed and routed such that movement is not necessary during the installation or removal of LRUs (Line Replaceable Units).

Again, this is to minimize stresses to the fiber optic cable and extend the component service life. An additional note from Dennis Jettun on Fiber Optics: “There have been occasions on the F-16 Optics FBO test program where cycling of the heat (hot-cold) caused the optics to age much faster in the sense of brittleness. This becomes a big issue with maintenance, not necessarily to the cable, but to equipment that may be nearby that requires loosening of a cable/bundle clamp to get to the component. If enough hot/cold cycles are seen by a fiber optic, it is most likely to crack if trying to be moved.” In other words, if you know you will never move the cable, then it is possible there will be no issues. However, if you must move a harness with a fiber optic cable, it is important to be prepared.

In summary

EWIS installation comes down to the following basic principles: keep it dry, keep it protected, and keep treating it nicely. Following each of these will minimize rollout problems for the aircraft and maximize service life.

Michael Traskos

Michael Traskos

President, Lectromec

Michael has been involved in wire degradation and failure assessments for more than a decade. He has worked on dozens of projects assessing the reliability and qualification of EWIS components.