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

Aircraft EWIS failure investigation

Aging Wires & Systems

When systems fail, it is often necessary to identify the fault source in order to know where to assign the blame (legal), determine if a maintenance action is necessary (customer support), or improve a product (development). When it comes to aerospace incident investigation, it can be difficult to isolate the cause of faults occurring in-flight.

The NTSB’s Office of Research and Engineering has developed a presentation for the purpose of illustrating patterns and indicators of in-flight and post-crash fires on aircraft. Important for the EWIS community is that the presentation contains information linking EWIS failure directly to electrical fires. The signatures of electrical fires and fires from explosions are described verbally and through photographs of post-crash aircrafts along with their telltale signs of each. Of the examples used, all electrical fires were said to be wires damage by poor EWIS maintenance.

The following is a summary of a typical EWIS failure investigation.

Electrical Fires

Electrical fires are born when the wire diameter is reduced by being bent, rubbed, and/or pinched, thereby increasing the local resistance and increasing the temperature of the area. Depending on the attached equipment, this localized ‘hot spot’ may reach a safe equilibrium, but by no means should this be considered a safe condition. The NTSB reports that electrical fires can be caused by sharp bends in wires, eroded conductors, ripped or brittle insulation, and loose connections. Beeding on the broken ends of wires is also an indicator of a possible electrical fire (examples are shown below).

Case Study #1 – Ruptured Pneumatic Tube

aircraft EWIS failure investigation
Bend in Wire
aircraft EWIS failure investigation
Ripped Insulation
EWIS failure
Wire Beeding

The NTSB presentation includes case studies about in-flight fires due to wire failures. One incident involved a Beech 58P aircraft and occurred when the pilot was conducting a test flight. The left engine burst into flames immediately after takeoff. During the post-incident aircraft inspection, engineers found an alternator wire and a pneumatic line towards the left wing’s trailing edge. An area of insulation was missing in the middle of the alternator wire; the surrounding alternator wire insulation was intact but charred and melted. The exposed conductor had areas where the tin coating was missing and the copper wire underneath was visible (the melting point of tin is 232°C). The NTSB’s investigation concluded that the wire had arced and melted the pneumatic tube causing a fire.

Case Study #2 – Fuel Ignition

Another case study documented a Beech 36 crash in Oregon. During takeoff, the pilot heard a loud explosion and the airplane violently yawed to the left and off the runway where it crashed. The post-crash investigation found, near the right side of the aircraft, a wire harness that was installed incorrectly. This harness showed signs of chaffing and discoloration. Cut insulation was also found. The investigation also discovered a leak from the fuel bladder. The investigation report concluded that a wire in the damaged harness arced and ignited the fuel leak that caused the explosion.

EWIS Investigation Tools

As shown in the case studies above as well as many other well-known incidents, electrical fires can be incredibly deadly and result in loss of life and aircraft. When the aircraft is in takeoff, touchdown, or flight, a fire will always cause irreplaceable damage. If the aircraft is thousands of feet off the ground, lives are certainly lost. Damage to EWIS can dramatically impact an aircraft’s airworthiness. Regular EWIS inspection and maintenance is essential to prevent these horrible disasters from happening again.

Emma Schwoerer

Emma Schwoerer

Emma is a full time engineering student at The George Washington University. She works at Lectromec as a junior engineer on a variety of projects including wire testing, aged platform assessment, and arc damage modeling.