View Latest Blog Entries
Close
Categories
Testing & Assessment Certification Aging Wires & Systems Management Standard & Regulation Conference & Report Maintenance & Sustainment Protection & Prevention Research Arcing Miscellaneous
Popular Tags
Visual Inspection MIL-HDBK MIL-HDBK-525 FAR AS50881 FAR 25.1707 High Voltage Electromagnetic Interference (EMI) Wire System Maintenance Arcing Damage FAR 25.1709
All Tags in Alphabetical Order
25.1701 25.1703 Accelerated Aging ADMT Aging Systems Aircraft Power System Aircraft Service Life Extension Program (SLEP) arc damage Arc Fault (AF) Arc Fault Circuit Breaker (AFCB) Arc Track Resistance Arcing Arcing Damage AS22759 AS22759/87 AS4373 AS4373 Method 704 AS50881 AS5692 AS6019 AS85485 AS85485 Wire Standard ASTM F2799 ATSRAC Attenuation Automated Wire Testing System (AWTS) Bent Pin Analysis Best of Lectromec Best Practice bonding Cable cable testing Carbon Nanotube (CNT) Certification Chafing Chemical Testing Circuit Breaker circuit design Circuit Protection Coaxial cable cold bend comparative analysis Compliance Component Selection Condition Based Maintenance Conductor conduit Connector connectors contacts Corona Corrosion Corrosion Preventing Compound (CPC) Cracking D-sub data analysis data cables degradat Degradation Delamination Derating diagnostic dielectric constant Distributed Power System DO-160 Electrical Aircraft Electrical Component Electrical Testing Electromagnetic Interference (EMI) Electromagnetic Vulnerability (EMV) EMC EMF EN3197 EN3475 EN6059 End of Service Life End of Year Energy Storage engines Environmental Environmental Cycling ethernet EWIS Component EWIS Design EWIS Failure EWIS Thermal Management EZAP FAA AC 25.27 FAA AC 25.981-1C 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 testing Fundamental Articles Future Tech Green Taxiing Grounding Harness Design Hazard Analysis health monitoring heat shrink tubing high current high Frequency high speed data cable High Voltage History Hot Stamping Humidity Variation ICAs IEC60172 Instructions for Continued Airworthiness Insulation insulation resistance IPC-D-620 ISO 17025 Certified Lab Kapton Laser Marking life limited parts life projection Lightning Maintenance Maintenance costs Mandrel 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-1560 MIL-STD-1798 MIL-STD-464 MIL-T-7928 MIL-T-81490 MIL-W-22759/87 MIL-W-5088 Military 5088 modeling MS3320 NASA NEMA27500 No Fault Found off gassing Outgassing Overheating of Wire Harness Parallel Arcing part selection Performance physical hazard assessment Physical Testing polyimdie Polyimide-PTFE Power over Ethernet Power systems predictive maintenance Presentation Probability of Failure Product Quality Radiation Red Plague Corrosion Reduction of Hazardous Substances (RoHS) regulations relays Reliability Research Rewiring Project Risk Assessment SAE Secondary Harness Protection Separation Requirements Series Arcing Service Life Extension Severe Wind and Moisture-Prone (SWAMP) Severity of Failure Shield Shielding signal cable silver plated wire smoke Solid State Circuit Breaker Space Certified Wires stored energy supportability Sustainment Temperature Rating Temperature Variation Test methods Test Pricing Testing Thermal Circuit Breaker Thermal Endurance Thermal Index Thermal Shock Thermal Testing Tin plated conductors Troubleshooting TWA800 UAVs verification Visual Inspection voltage white paper whitelisting Wire Ampacity Wire Certification Wire Comparison wire damage wire failure wire properties Wire System wire testing Wire Verification work unit code

Lessons learned from NASA: Wire identification, harness clamping, and more

Protection & Prevention

Learning from the mistakes of the past is critical for ensuring reliability of systems created today. These lessons may be contained in industry standards documents with little or no explanation as to why the requirements were created (such as AS50881). This lack of historical knowledge and the loss of the answer to ‘why’ can leave newcomers and veteran system designers handicapped, being forced to blindly comply with a requirement that is not well understood. To maintain institutional application knowledge gained from space bound and ground support systems, NASA has developed an online resource. This NASA site provides a large repository of lessons learned and decades of experience in a searchable system. The following is a select review and explanation of each of the lessons learned.

Wire Identification

  • Recommendation: Individual wire identification should be used on space flight vehicles.
  • Benefit #1: Originally, the thought behind not identifying wires was that maintenance was unnecessary after launch. However, during the construction of the ARES I-X problems were found in long wire harnesses after installation. Significant challenges were faced by the repair crews in identifying the wire in need of replacement.
  • Benefit #2: During harness construction, there were, “many cases where the wires were improperly pinned”. Had the wires been identified, reworking the connectors would have been easier as to identify those in the incorrect locations.
wire identification
Wire identification can be challenging

Handing Small Gauge Wires

  • Recommendation: Stripping of small gauge wires (sizes smaller than 30AWG), regardless of application, should avoid mechanical methods. This is particularly recommended for transformer and inductors designed with coil wire between 38 and 32 AWG.
  • Benefit: Mechanical processed for stripping wires of these sizes have been shown to damage the wire. Examination of transformers found with mechanical stripping of small gauge wires reveled breaks and damage at solder locations to larger terminals.

Harness Clamping

  • Recommendation: Procedures should include tying of wire bundles before clamping and using totally insulated clamps.
  • Benefit #1: After maintenance is performed on wire harnesses that require opening of clamps, it may be possible for a wire to become pinched into the clamp when tightened. Tying wires before clamping will help to reduce the likelihood of this occurring.
  • Benefit #2: The use of totally insulated clamps will also reduce the chance of a damage wire shorting or arcing to the clamp.

Crimped Contacts

  • Recommendation: When crimped contacts are to be used in spacecraft or ground support equipment cable harness assemblies, a requirement should be imposed on the fabricators, that color coded contacts and pull tests be incorporated into acceptance test procedures.
  • Benefit: Visual inspections and not able to identify the laying and compression of the wires strands, integrity of the mating surface, and the physical strength of the connection.

These are just four of the nearly 100 lesson learned that NASA has with regard to wiring. This resource maintains the knowledge gained from the manufacture, testing, and launch of space bound platforms. Many of the recommendations and lessons learned can be applied to aircraft.

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.