View Latest Blog Entries
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 Maintenance Electromagnetic Interference (EMI) 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 accessibility 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 installation 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 distance 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

Importance of aircraft electrical wiring interconnection system (EWIS) analysis


ewis analysis

A United Airlines B767-300 on a Jan. 9, 1998 flight, from Zurich to Washington DC, was forced to execute an emergency landing at London’s Heathrow airport because of a food chiller unit improperly installed in the electronic and equipment bay. A jagged edge on the chiller scraped wire insulation as the chiller was pushed into position. The result was wholesale arcing damage. This is just one of several events that highlighted the need for more attention to be paid to the maintenance of aircraft EWIS analysis and wiring systems on an aircraft and illustrated that inattention to these details can affect the airworthiness of an entire airplane.

A Risk Analysis Tool (RAT™) has been developed for the Federal Aviation Administration (FAA) to aid aircraft manufactures and maintenance personnel in the continued airworthiness of their aircraft. This tool introduces a fresh perspective to the maintenance and upkeep of Electrical Wire Interconnect System (EWIS). Problems and malfunctions of the wiring systems are broken down into categories, each identifying specific levels on which malfunctions can occur and to what degree of severity. Implementation of the RAT™ requires us to introduce three types of EWIS failures: wire level, bundle level, and zonal level.

Electrical Wire Interconnection System (EWIS) analysis

At the wire level, insulation breaches can have effects ranging from degraded function to eroded safety margins. Because most wires are routed in groups, or bundles, adjacent wires in a bundle are often subjected to similar types of environmental and mechanical strains. Consequently, these adjacent breaks may increase the likelihood of cascading damage.

At the bundle level, an insulation break can lead to arcing, and failure of many wires in the bundle. Depending on the number of systems to which the wires are connected, this type of spreading damage can wipe out functions and force the aircrew into emergency procedures. If not already tripped, circuit breakers may have to be pulled, smoke evacuation and fire fighting equipment put into action. The repair effort involves time, expertise and cost to return the airplane to airworthy condition.

At the zonal level, or damage that extends across multiple bundles, the problems are worse. Failures at the zonal level can completely negate fail-safe design and built in redundancy features. The electronics and equipment bay, typically located below the cockpit, is a notable case in point. The sheer concentration of power feeder cables, signal wires and the end-use components to which they are connected makes the E&E bay particularly vulnerable.

Electrical Wire Interconnection System (EWIS) analysis

The RAT™ facilitates evaluation of a particular wiring layout. Evaluation can be done during original design to assure adequate separation and segregation of aircraft wiring, thereby minimizing the potential for single point failure. The tool can also be used for assessing the safety of modifications to the original layout, as might be the case in the supplemental type certificate (STC) process.

By identifying the function, length and type of every wire on the airplane, its proximity to potentially volatile fixtures (fuel tanks and hydraulic lines), and its exposure to the elements, the RAT™ can calculate the failure rate per foot of wire per flight hour. This metric will prove extremely useful in choosing the wire installation procedure that will satisfy the planned service life of an aircraft.

By identifying EWIS failures at the wire, bundle and zonal level, we can change the way we think about the continued airworthiness of an aircraft. Implementation of the RAT™ tool requires that all personnel understand the importance of wiring maintenance and the circumstances that contribute to EWIS failure.

Michael Traskos

This article was written by the Lectromec technical team. Aircraft wiring is our passion and we strive to make a contribution to the field by sharing our expertise through blogs, podcasts, and videos. We hope you find this information helpful. We also encourage you to submit comments and spur discussions.