ISO 2155:1974

Overview

ISO 2155:1974 specifies performance requirements for fire‑resisting electrical cables used in aircraft wiring. It applies to single‑conductor cables with an electrolytic copper core covered with nickel or an equivalent material, designed for rated voltages up to 600 V and frequencies up to 2 000 Hz. The standard addresses cables intended to survive elevated temperatures (continuous service up to 280 °C, short‑term up to 400 °C) and to retain dielectric strength when exposed to flame (1 100 °C for 5 minutes). It also requires suitability for fixed aircraft wiring at temperatures down to −75 °C.

Key topics and technical requirements

• Conductor construction
  • Electrolytic copper core with nickel (or equivalent) covering.
  • Wire geometry, strand/bunch lay, limits on joints (not more than one joint per 50 m).
• Insulation and sheath
  • Primary insulation must form a close circular profile around the core without undue adhesion; must limit corona, blistering and corrosion risks.
  • Protective sheath definitions and material resistance requirements.
• Electrical and dimensional properties
  • Resistance per unit length and conductor dimensions per referenced ISO documents.
  • Spark tests (two types) for primary insulation - Spark Test No. 2 requires 1 500 V AC, 50–60 Hz, applied for at least 1 minute between core and water.
• Thermal and fire performance
  • Continuous service up to 280 °C; short exposure up to 400 °C.
  • Retention of dielectric strength after exposure to specified flame conditions.
• Environmental resilience
  • Non‑hygroscopic, fluid‑resistant (aircraft fluids), mildew‑resistant, light and moisture fastness after tropical storage.
  • Operating temperature down to −75 °C.
• Testing regime
  • Type tests: continuity, fire‑resistance, hot cutting, ageing, fluid resistance, humidity cycling, capillary attraction, abrasion.
  • Production/routine tests: spark tests, resistance per unit length, conductor geometry, weight, insulation thickness, outer diameter, cold coiling, fire‑resistance, accelerated ageing.
• Marking and traceability
  • Marking per ISO 2574; reel/coil labels include manufacturer, standard number, conductor composition, date/place of manufacture, inspector reference and lengths.

Applications and users

ISO 2155 is intended for:

• Aircraft electrical system designers and integrators specifying fire‑resisting cables for fixed wiring.
• Cable manufacturers producing aircraft‑grade, high‑temperature, fire‑resistant cables.
• Certification authorities, procurement specialists, and maintenance engineers responsible for compliance, testing and replacement of aircraft wiring in engine bays, APU compartments and other high‑temperature zones.

Related standards

• ISO 1967 - Dimensions, conductor resistance and mass for aircraft fire‑resisting cables
• ISO 2156 - Methods of test for aircraft fire‑resisting electrical cables
• ISO 2574 - Identification of aircraft electrical cables
• ISO 1467 - (referenced for dimensions and conductor resistance of finished cables)

Keywords: ISO 2155, fire‑resisting electrical cables, aircraft wiring, fire‑resistant cables, nickel‑covered copper conductor, aircraft electrical cables, high‑temperature cable.