View Latest Blog Entries
Close
Categories
Testing & Assessment Certification Standard & Regulation Aging Wires & Systems Maintenance & Sustainment Protection & Prevention Management Conference & Report Research Miscellaneous Arcing
Popular Tags
Visual Inspection High Voltage AS50881 MIL-HDBK MIL-HDBK-525 FAR Electromagnetic Interference (EMI) AS4373 Maintenance FAR 25.1707 Wire System Circuit Protection
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 Aluminum arc damage Arc Damage Modeling Tool Arc Fault (AF) Arc Fault Circuit Breaker (AFCB) Arc Resistance 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 B230 ASTM B355 ASTM B470 ASTM D150 ASTM D2671 ASTM D495 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 EMI 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 Filter Line Cable 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-F-5372 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

Principles of aircraft wiring system safety

Protection & Prevention

Principles of Aircraft Wiring System Safety

System safety supports risk management with the ultimate goal of optimizing safety on aircraft systems. Risk management is a vital aspect of system development that takes effect during the design phase; however it also remains important during the implementation and sustainment phases of an aircraft lifecycle. Optimizing safety is implemented through risk identification as well as implementing proper designs and/or procedures to mitigate risk.

According to FAA’s System Safety Handbook, system safety is a “balanced program [that attempts] to optimize safety, performance, and cost.” This is a challenging balance to achieve when designing any system because too much emphasis on one factor can lead to sacrificing another vital factor, which can then cause an unbalance. However system safety is interdependent with performance and cost through defining acceptable risk tolerances that can satisfy cost and performance requirements. The graph below illustrates the tradeoff between system safety and cost, schedule and performance. As the safety effort increases, the cost on optimizing safety should also increase while the probability of a hazardous event decreases.

Aerospace Wiring System Safety
Source: FAA System Safety Handbook, Chapter 3: Principles of System Safety

When applying the principle illustrated in the graph to EWIS, the following factors impact systems safety: weight, volume, and cost. For instance, interference can occur when a system signal wire is routed in a harness near another component that produces Electromagnetic Interference (EMI). The following options can be considered for optimizing safety and decreasing the likelihood of system interference.

  1. Redesign harness routing: This can be a possible solution to reduce EMI interference. However it may lead to susceptibility to EMI generated by other components.
  2. Increase shielding of wire/cable: This would either add weight and volume (using a double shield cable option) or cost (using advanced shielding option like a Carbon Nanotube shield). This will also increase the installation complexity.
  3. Apply shielding to the harness: This will add weight, volume, and cost, and may make repair of the system harness difficult while in service.
  4. Component redesign: Redesign the EMI producing component to make it produce less EMI.This would likely cause a delay for implementation.
  5. Modify the system to be more fault tolerant: Modify the hardware/software of the system to handle lower data fidelity. Similar to #4, this would likely cause a delay for implementation.

From a system safety perspective, each of the five options will achieve the desired airworthiness result, and therefore it is necessary to evaluate other factors. Each viable option would have their merit depending on what part of the lifecycle the issue was discovered. If the issue was discovered early in the design, then component redesign (#4) may be a viable option as the generated EMI will likely impact other systems and could lead to the lowest weight and most cost effective way to address the issue. If the issue was discovered while the aircraft was in-service, then wrapping the harness with shielded harness sleeving (#3), might be the most cost effective way to address the issue until the next D-check when the system wire can be replaced (#2).

RISK CLASSIFICATIONS: ACCORDING TO THE FAA

Risk is characterized by the severity of the hazard and likelihood of occurrence (this is similar to MIL-STD-882).

According to the FAA, severity can be categorized four ways

  • Catastrophic (results in multiple fatalities and total system failure)
  • Critical (results in serious injuries to multiple people and partial system failure that significantly reduces the safety of the aircraft)
  • Marginal (results in discomfort to multiple occupants on an aircraft and minor systems damage)
  • Negligible (Has no effect on safety)

Likelihood or probability is categorized into five categories

  • Frequent (highly likely to occur)
  • Probable (will occur several times)
  • Occasional (will occur once or twice)
  • Remote (unlikely to occur)
  • Improbable (highly unlikely to occur)

A comparative safety assessment is a common method that can be performed to quantify the identified risks in a particular system. This tool allows identified risks to be categorized through their severity and likelihood of occurrence in order to prioritize and allocate money to prevent hazardous events. Tools like the Lectromec’s EWIS RAT can help with defining the risk to an aircraft’s EWIS.

Carina Cannon

Carina Cannon

Engineer, Lectromec

Carina is a systems engineer with experience in quality management systems, EWIS component degradation modeling, and test equipment design. Carina’s work has focused on Service Life Extension Programs (SLEP) and preparing Lectromec’s lab for formal lab certification.