Aircraft EWIS Testing Guide

This guide explains what the electrical wiring interconnection system (EWIS) includes and which tests MRO and harness shops use to prove it, citing the FAA and test-equipment manufacturers.

What EWIS is

• 14 CFR 25.1701 defines EWIS as wires, connectors, terminals, splices, clamps and other devices used to carry electrical energy between two or more termination points ^[1].
• FAA AC 25.1701-1 gives guidance on EWIS design, installation, maintenance and inspection ^[2].

Core tests

• Continuity and shorts, often with 4-wire Kelvin resistance ^[3][4].
• Insulation resistance and dielectric withstand (hi-pot) ^[3][5].
• Function tests of relays, sensors and actuators ^[4].
• Bond and loop resistance; on fuelled aircraft only with intrinsically safe tools ^[6].

Choosing a tester

• Point count, test voltage and format (bench, mobile, distributed) ^[5].
• Data import from harness wire lists ^[3].
• AMM-specified tools for particular tasks ^[7].
• Crimp and termination quality: see the crimp tool guide and DMC tools ^[8].

Products referenced in this guide

• DMC – Daniels Manufacturing CorporationAircraft Wiring & Connector ToolsRFQ

  

  DMC AF8 8-Indent Crimp Tool (M22520/1-01)

  Model: AF8

  • 8-impression crimp for maximum tensile strength on closed-barrel contacts
  • Ratchet controls the cycle in both handle directions
  • 8-position selector knob, lockable with pin or safety wire
  • Over a thousand turret heads available

  Status: Request a quote · calibration certificate on request

Related category

Aircraft Electrical & EWIS Testing · All aviation guides

Frequently asked questions

Is hi-pot testing safe on installed wiring?

Only within the voltage limits in the aircraft or component manual; testers like Automeg offer selectable ranges ^[5].

What is loop resistance testing?

A check of the resistance of shield and bond loops; MK's ExLRT does it intrinsically safely ^[6].

This guide is general information. It does not replace the aircraft maintenance manual, the operator's approved procedures or the rules of the competent civil aviation authority.

Request a quote

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Sources

1. 14 CFR 25.1701 – EWIS definition (eCFR)
2. FAA AC 25.1701-1 – Certification of EWIS on Transport Category Airplanes
3. Cirris – Automated wire harness testing for the aerospace industry
4. MK Test Systems – Automeg brochure (PDF)
5. MK Test Systems – Automeg
6. MK Test Systems – Global Intrinsic Safety certification awarded to ExLRT
7. MK Test Systems – Aerospace automatic test equipment
8. DMC (Daniels Manufacturing Corporation) – Mil-spec crimp tools