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 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 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

Effects of SFAR-88 on aircraft wire maintenance




The acronym stands for Special Federal Aviation Regulation 88. It deals with fuel system safety, to include aircraft wire maintenance, aircraft wire and electrical components (pumps, fuel quantity indicators, etc.), not only inside the tanks, but circuitry and items located outside the tanks including adjacent dry bays. By December 2004, operators must include Federal Aviation Administration (FAA)-approved provisions in their inspection and maintenance programs to assure the safety of their aircraft fuel systems. SFAR 88 requirements for continued airworthiness of fuel systems may be the single biggest maintenance change in many years, and for years to come.

The Airplanes and Organizations Affected

All turbine-powered aircraft with a capacity of 30 or more passengers or a payload capacity of 7,500 pounds or more. SFAR 88 affects manufacturers (the type certificate, or TC, holders), those companies holding supplemental type certificates (STCs) involving modifications and installations affecting fuel systems (mostly manufacturers), operators, repair stations and FAA inspectors. The number of STCs affected by SFAR 88 is more than 120. The genesis: SFAR 88 results from a tragedy, the fatal July 1996 explosion of the center wing tank (CWT) of a TWA B747. In its investigation of the TWA Flight 800 tragedy, the National Transportation Safety Board (NTSB) ultimately determined that a short circuit caused flammable vapors in the tank to ignite. Since the TWA tragedy, improved fuel system safety has been on the NTSB’s “Most Wanted” list of aviation safety improvements.

The March 2001 CWT explosion of a Thai Airways International B737 on the tarmac at Bangkok added impetus to the effort. SFAR 88 was issued for industry comment just two months after the Bangkok accident. The package: SFAR 88 requires a massive fuel system safety review and analysis, with three outputs: (1) regulatory changes to ensure that ignition sources in fuel systems are prevented by design, (2) changes to existing fuel systems to eliminate potential ignition sources identified by the safety analysis, and (3) maintenance and inspection changes to ensure “continued airworthiness” of fuel systems.

A selective listing of what to expect:

  • Fuel pumps: Ground fault interrupters (GFI) for all tanks, replacing existing pump power relays. GFIs and automatic shutoff at low fuel levels may be required.
  • Fuel quantity indication systems (FQIS): Since 115 volt AC current could potentially short to FQIS signal wiring, barrier device protection may be required for all CWTs.
  • Lightning protection: Improved bonding of fasteners, clamps and pipes attached to (or in) the tank structure will be necessary.
  • Fault current protection: “K” type fasteners are deemed an unreliable bond and in-tank bonding jumpers may have to be installed in some aircraft.
  • Wire harnesses over the CWT: Insufficient clearance on some aircraft, such that wires could touch the tank surface. Engineering changes have been developed.
SFAR88 – what does it mean?

The concept: SFAR 88 effort involves a new term, critical design configuration and control limitations, or CDCCL. TC and STC holders define CDCCLs. Under this concept, all fuel pumps become critical items, as are fuel pump wiring and fuel pump circuit protection devices.

These critical items (CDCCLs) can be subject to mandatory inspection and maintenance tasks. CDCCLs involve design aspects such as wire separation, explosion proof features of a fuel pump, maintenance intervals for transient suppression devices, fuel quantity indication system (FQIS) wiring, minimum bonding jumper resistance levels, and so forth. Any maintenance actions or subsequent changes to the design must not degrade the safety level of the original design over the operational life of the airplane. STC wiring installed adjacent to original design wiring may well be categorized as safety critical under the CDCCL aegis.

SFAR88 – what does it mean? SFAR88 – what does it mean?
Fuel tank hazards the SFAR-88 Safety assessments are intended to prevent (Photos: FAA)

If you are interested in wire maintenance, you may want to read Lectromec’s The 7 Tenets of Wire Systems Installation article.

A new division of risk: The FAA recently outlined four criteria by which system safety assessments will be approved:

  1. single failures, all tanks,
  2. combinations of failures,
  3. unacceptable service experience, all tanks, and
  4. flammability exposure time of all tanks. Tanks will be divided into low and high exposure, with flammable vapors present in the tank more than seven percent of the time dividing the two.

If an inerting system or flame retardant metal mesh is installed, SFAR 88 requirements need not be carried out on high exposure tanks.


  • SFAR 88 is here to stay and is likely to have a big impact, including on aircraft life extension programs.
  • Expect numerous airworthiness directives (ADs), coming soon, with varying compliance times.
  • Development of an inerting system is likely to continue at a fast pace.
  • In the meantime, SFAR 88 requires a whole range of wiring and related fuel/electrical system inspection and maintenance activity

For those interested in further reading on the topic, FAA regulation 25.981 goes into further details on fuel tank ignition prevention and the factors that must be considered for aircraft design. Discussion of this regulation can be found here.

Michael Traskos

This article was written by the Lectromec technical team. Aircraft wiring is our passion and we strive to make a contribution to the field by sharing our expertise through blogs, podcasts, and videos. We hope you find this information helpful. We also encourage you to submit comments and spur discussions.