View Latest Blog Entries
Testing & Assessment Certification Aging Wires & Systems Standard & Regulation Management Conference & Report Maintenance & Sustainment Protection & Prevention Research Arcing Miscellaneous
Popular Tags
Visual Inspection MIL-HDBK MIL-HDBK-525 AS50881 FAR High Voltage FAR 25.1707 Electromagnetic Interference (EMI) Maintenance Wire System Arcing Damage AS4373
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 AS83519 AS85485 AS85485 Wire Standard ASTM D150 ASTM F2799 ATSRAC Attenuation Automated Wire Testing System (AWTS) batteries 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 conductors 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 dynamic cut through 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 IEEE 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 measurement 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 Resistance 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 Splice standards 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 USAF verification Visual Inspection voltage white paper whitelisting Wire Ampacity Wire Certification Wire Comparison wire damage wire failure wire performance wire properties Wire System wire testing Wire Verification wiring components work unit code

Notch Testing and the Impact of 1000 Cuts

Testing & Assessment

Key Takeaways
  • Notch testing examines the impact of a small cut on a wire.
  • Methods vary on the wire/cable performance assessment but relay on three parts: cut the wire insulation, mechanical stressing, and assessing the cut site.
  • The notch test is a good way to screen wires/cables and identify their susceptibility to damage.

How much damage can a single wire take? Does the failure of a wire’s insulation require one large trauma (think of dropping a hammer on it), or is it possible for the insulation to fail due to 1,000 small cuts? That has been a question plaguing wire system sustainment for decades. Identifying one large trauma can be easy, but to catalog all the minor traumas is impossible.

There is at least a means to determine if a wire’s insulation can withstand at least one cut. The means to do this is with the notch propagation test.

Test overview

In this test, a razor blade is set in a test fixture such that only 1 – 5 mils (0.0254 – 0.127 mm) of the blade is above the fixture. This limits the penetration to the blade height.

The blade is then run across the wire (perpendicular to the wire length) to create the notch in the wire insulation. After the cut is made, the wire is then subjected to a bend test in which the wire is wrapped around a mandrel. This wrapping action is indented to mechanically stress the insulation, and the notch location, such that the notch expands and potentially propagates to the wire conductor.

Test Method

The most common standards for aerospace notch propagation are the AS4373 and the EN3475. At the core, they both seek to apply a notch; the two standards differ in what happens after the notch is created.

Summary of notch propagation testing.

In the AS4373 test procedure, the post-notch wrapping and unwrapping continue until either the conductor is exposed, or 100 cycles have been completed (whichever is first). If the specimen passes the 100 wrap cycles, it is again visually examined for an exposed conductor. A specimen has passed the test if no conductor is exposed.

In the EN3475 test procedure, the post-notch wrapping is done only once, but the sample is then subjected to a wet dielectric test.

Both test methods have merit in the test performance. The AS4373 method examines the case where the wire/cable is in a flex application or if near a disconnect. The EN3473 method considers a common case of stationary wire and dielectric breakdown with the application of voltage. The selection of the test method should be done to best reflect the application.

Tests on Cables

This test may also be performed on cables. When this is done, the same procedures are followed except the objective is to determine if there is a breach of the jacket to the cable shield. The same pass/fail criteria used for wires may be used for cables.

In Application

In application, the notch propagation test would eliminate any aerospace wire construction that is identified as ‘lightweight’. Lightweight wire constructions (such as AS22759/91) have a wall thickness minimum of 5.8 mils. While it is possible that a 5 mil cut would not cut through to the conductor, it is likely that a breach would propagate during the bend test or a hole would be created when voltage is applied in the dielectric test.

Organizations that place value on the notch propagation test will often mitigate the risk of insulation damage by either

  1. Requiring all lightweight wires be in wire harnesses with additional sleeving/protection, or
  2. Require lightweight wires to be in a jacketed cable.

[Side Note: naturally, the value of lightweight constructions often comes up when factoring in additional protection requirements. This will be addressed in a future Lectromec article].

By adding this additional layer of protection, the wires are protected from small cuts.


The notch propagation test is one of many tests to evaluate a wire/cable’s insulation performance. By creating a little insulation damage then mechanically stressing the wire, it is possible to see if the insulation is likely to tear after a small cut. The test itself is straight forward, but the application of the results is not. The results are pass/fail, so it does not provide much information when comparing different wire/cable constructions. A means to augment the test is to progressively increase the blade penetration to see when the sample fails. In doing so, additional value can be gained from the testing.

As always, Lectromec’s ISO 17025 accredited lab is available to perform this or any other wire/cable test you need. Contact us to find out how we can help your wire/cable test project.

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. Michael is an FAA DER with a delegated authority covering EWIS certification and the chairman of the SAE AE-8A EWIS installation committee.