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 D2671 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-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-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 Shrinkage 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 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 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

Aircraft wire systems: Bent pin analysis

Testing & Assessment

Previous Lectromec articles have focused on certain parts of system design such as the physical separation between systems. In particular, the articles have focused on the wiring. In this article, we will switch our attention to a different, but no less important, area: the Electrical Wiring Interconnect Systems (EWIS) connector assessment. Specifically, we will examine bent pin analysis for aircraft wire systems.

aircraft wire systems
Review of each connector can be a time consuming process, but a necesary one as part of a thorough EWIS risk assessment. The top figure shows a representative 16-pin connector. When performing a bend pin analysis on this configuration, the simulation found the potential for 6 pin-to-pin shorts from the center pin. No multiple pin shorts were possible from the center pin location.

The connector designs today do an excellent job of handling operational environments on aircraft and maintenance actions as well as providing long-term reliability. But part of the process of ensuring reliable system performance is to be able to identify and mitigate issues that may come up during installation or maintenance. Here we look at one of the more challenging assessments for connectors: the Bent Pin Analysis (BPA).

The basic idea of the BPA is that during routine maintenance actions and disconnecting/connecting connectors, one or more pins may not line up correctly and may be bent/damaged during connector mating. This pin, now bent and compressed in the connector, may make contact with other pins within the same connector.

Gathering the data

When performing a bent pin analysis (which may be part of 25.1709 analysis), a lot of data must be gathered. This means that the functional characteristics and the electric characteristics must be assembled for each pin. For those looking to perform a comprehensive assessment, it is recommended that these descriptions are as thorough as possible. They can be catalogued in a matrix with the following information:

  • Pin ID
  • Connected System/Circuit Information: Identify the system and the support function for the wire. If this pin is powered, identify the type of power and circuit protection.
  • Circuit State: If the pin has multiple operational modes, then each of them should be identified.
  • System Effect: What is the impact on the system in case of failure?
  • Hazard Level: Is this a threat to the safety of the aircraft?
  • Additional Comments: Are there other areas that should be noted that have not been covered?
aircraft wire systems

Considerations

When performing a BPA, there are several factors that should be considered throughout the analysis:

  1. Physical Failures: The BPA looks at the functional failures, with less emphasis being placed on physical failures. That, in part, is due to the fact that under FAA EWIS Regulation 25.1709, the loss of a wire harness must also be considered. As such, physical failures should already have been covered during the EWIS analysis. If the BPA is performed outside of a new aircraft certification process, understanding the physical failure impact may need to be considered for connectors near critical systems (e.g. fuel tanks).
  2. Pin Length: One key aspect often overlooked is the pin length. The bent pins can make contact with the nearest neighbors, but depending on the pin length, these pins might extend further and make contact with multiple pins. Naturally, this not only may cause a problem for one system but for multiple systems.
  3. Pin to Connector Shell: The bent pin analysis does not only examine the pin-to-pin failures but also the pin to connector shell failures.
  4. Functional Failure: The analysis should also evaluate whether it is possible that a bent pin may create a connection and a scenario of potentially hazardous or misleading information.

What Is the Output of a Bent Pin Analysis?

The result of a BPA should be a comprehensive assessment of the aircraft’s connectors and should include recommendations that pinpoint the changes that need to be made. These changes may include a change of pin positioning, selecting a different connector, and/or splitting the wires into one or more connectors. The recommendations will need to be evaluated to determine change feasibility and risk to the aircraft and system reliability. After final consideration, some bent pin issues may be deemed as limited risk as they only impact some non-critical systems/functions.

Summary

Gathering all of this information early in a design process can be difficult, but can help to avoid significant changes later in the design/certification process.

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.