View Latest Blog Entries
Close
Categories
Testing & Assessment Certification Aging Wires & Systems Standard & Regulation Management Maintenance & Sustainment Conference & Report Research Protection & Prevention Arcing Miscellaneous
Popular Tags
Visual Inspection AS50881 MIL-HDBK MIL-HDBK-525 High Voltage FAR Electromagnetic Interference (EMI) FAR 25.1707 AS4373 Maintenance Wire System Arcing Damage
All Tags in Alphabetical Order
2021 25.1701 25.1703 abrasion AC 33.4-3 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 AS4373 AS4373 Method 704 AS50881 AS5692 AS6019 AS83519 AS85049 AS85485 AS85485 Wire Standard ASTM D150 ASTM D8355 ASTM F2696 ASTM F2799 ASTM F3230 ASTM F3309 ATSRAC Attenuation Automated Wire Testing System (AWTS) Automotive backshell batteries Bent Pin Analysis Best of Lectromec Best Practice bonding Cable Cable Bend cable testing Carbon Nanotube (CNT) Certification Chafing Chemical Testing Circuit Breaker circuit design Circuit Protection Coaxial cable cold bend collision comparative analysis Compliance Component Selection Condition Based Maintenance Conductor conductors conduit Connector connector selection connectors contacts Corona Corrosion Corrosion Preventing Compound (CPC) Cracking 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 Electrical Aircraft Electrical Component Electrical Power Electrical Testing Electromagnetic Interference (EMI) Electromagnetic Vulnerability (EMV) 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 tree Fixturing Flammability fleet reliability Flex Testing fluid exposure Forced Hydrolysis fuel system fuel tank ignition Functional Hazard Assessment functional testing Fundamental Articles Future Tech galvanic corrosion Glycol Gold Gold plating Green Taxiing Grounding hand sanitizer handbook Harness Design Hazard Analysis health monitoring heat shrink heat shrink tubing high current high Frequency high speed data cable High Voltage HIRF History Hot Stamping Humidity Variation HV system ICAs IEC60172 IEEE 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 liquid nitrogen lunar 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-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-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 polyimdie Polyimide-PTFE Power over Ethernet power system Power systems predictive maintenance Presentation 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 Requirements Series Arcing Service Life Extension Severe Wind and Moisture-Prone (SWAMP) Severity of Failure shelf life Shield Shielding 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 supportability Sustainment System Voltage Temperature Rating Temperature Variation Test methods Test Pricing Testing 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 vw-1 wet arc white paper whitelisting 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

High-speed footage of wire failure near fuel line

Arcing Certification

Introduction

As with most fields, the more we learn about a particular topic, the better our understanding of its complexity and the finer details involved. One area Lectromec has done extensive research in is the potential impact of wire failure and electrical arcing (you can find several blog posts and white papers here). In this article, we would like to share recent research conducted by Lectromec on an area that received little attention in the past.

Background

The FAA regulations on Electrical Wiring Interconnection System (EWIS) separation are defined in FAA regulation Part 25.1707 and physical failure risk assessment in 25.1709. According to the regulations, wire failure should not impact the aircraft’s airworthiness. To show compliance, the first level is to determine the loss of function (such as with a broken/loose conductor), then the physical impact (arcing).

Aerospace Wire Testing

Lectromec’s first video describing the arc plume was released in 2008. It highlighted the wire failure arc energy and the potential damage to nearby components resulting from the hot ionized gas released from the event.

However, the video did not address a particular consequence of arc damage: the potential damage of molten metal. When the molten metal leaves the arc area, it departs at a velocity that can carry it several feet from the arc initiation site. The concern is that the molten metal from the event may come to rest on a target and create an unsafe condition.

Test Setup

For this test, a representative wire harness (115VAC, 3-phase power, 400Hz) was routed above a representative fuel line (this is good standard practice following AS50881 recommendations). The separation distance between the arcing wire harness and the representative fuel tube was 2.0 inches (more than the recommended minimum safe distance identified in AS50881). The failure mode tested is one where the clamp grommet has worn down and has abraded through the wire harness insulation.

With everything in place, the power was turned on and the arcing began.

Results

There are two things that should be kept in mind when viewing the video. #1: The direction of the arc plume (see the article discussing arc plumes) and #2 the molten metal that comes from the wire arc location and makes contact with the representative fuel tube. Both of these can potentially cause an unsafe condition.

Aircraft wire harness arcing failure captured through UV filtered lens at 300fps. A significant amount of copper was transfered from the arcing wires to the fuel tube.
Aircraft wire harness arcing failure captured through UV filtered lens at 300fps. A significant amount of copper was transferred from the arcing wires to the fuel tube.

As can be seen in the photo to the left, it is clear that the arc plume from the event is large enough to envelop the tube. In this test, even though the tube was electrically grounded, there was no direct arcing (this would have quickly resulted in a tube wall breach). What can be further seen from the still image and video is that most of the molten metal that struck the tube was deflected away from the event. However, the post-test analysis found that there were several bits of molten metal that adhered to the fuel tube. The molten metal ranged in size from 0.1mm to 4mm in diameter.

How much damage the molten metal can do is entirely dependent on the tube size (or fuel tank wall), the material, and several other key parameters. Several simulations were run with Lectromec’s Arc Damage Modeling Tool (ADMT). The simulations results suggest that it is entirely possible for some of these larger molten metal pieces to heat the target and cause the inside wall to rise above the autoignition temperature of fuel vapor. Other simulations showed that it is possible to cause pressurized tube rupture with the molten metal from the arcing events.

Comparison with the Previous Testing

Some of the work that Lectromec performed with the FAA in 2006 suggested that the molten metal may not have been much of a concern (report). But with further research, it appears that the conclusion may have been made too early. Testing carried out for the FAA, primarily focused on the potential arcing and damage caused by 20AWG wires. The molten metal produced by the smaller wires had less energy and was not considered a concern. The results of these recent tests however, suggest that the molten metal from such events must be considered as part of an EWIS failure impact analysis and risk assessment.

Need Testing

Lectromec’s laboratory is equipped to perform the high power tests needed for arc damage assessment. We can make sure that the tests generate the test data necessary for EWIS certification. Even if your aircraft are not subject to Part 25 EWIS regulations, these tests can provide you with the data you need for improved wire system design.

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. In September 2014, Michael was appointed as an FAA DER with a delegated authority covering EWIS certification.