Overview
ISO 2156:1974 - Aircraft - Fire-resisting electrical cables - Methods of test defines laboratory test methods used to verify that aircraft electrical cables meet the performance requirements given in ISO 2155. The standard is a test-methods reference for national test specifications and classifies tests by application: type tests, type + routine production tests, and type + production quality tests. It covers mechanical, electrical, environmental and fire-related durability checks specific to fire‑resisting aviation cables.
Key topics and requirements
ISO 2156 specifies practical test procedures and measurable acceptance criteria, including:
- Hot cutting test - evaluates resistance to sharp metallic contact. Uses a square‑edged knife (edge radius ≈ 0.40 mm) and progressive weight application; performed six times with 75 mm indexing between tests.
- Ageing + immersion dielectric test - oven ageing (e.g., 168 h at 280 ± 5 °C for certain tests) followed by immersion and electrical insulation checks to confirm no cracking and retained marking legibility.
- Humidity cycling - repeated cycles at 71 ± 2 °C and 95 ± 5% RH (24 h cycles repeated 15 times) with subsequent water immersion and electrical verification.
- Resistance to aircraft fluids - immersion of samples in fuels, lubricants, hydraulic and de‑icing fluids for service‑representative durations and temperatures; samples cooled to −20 ± 5 °C and inspected for splitting, cracking and marking retention.
- Abrasion test (Annex A) - running a “garnet” abrasive belt at ~1 520 ± 80 mm/min beneath the cable with graphite bands to indicate conductor exposure.
- Spark tests - two spark test types to detect insulation perforation: selection and sizing of fault detectors; artificial‑fault calibration; and a water‑immersion AC test at 1 500 V r.m.s. for 1 minute.
- Electrical & mechanical checks - conductor resistance per unit length (per ISO 1967), conductor diameter and lay (Annex B), wire elongation and breakage, insulation thickness, finished cable mass per length, cold coiling at −55 ± 2 °C, capillary/water uptake and accelerated ageing (e.g., 350 ± 5 °C for production quality tests).
Applications and users
ISO 2156 is used by:
- Aircraft component manufacturers and cable suppliers specifying and validating fire‑resisting electrical cables.
- Test laboratories performing aviation cable qualification and production verification.
- Regulatory bodies and certification authorities referencing standardized test methods for airworthiness.
- Engineers writing national standards or procurement specs that require consistent, repeatable cable testing.
Practical benefits include consistent safety verification against fire, abrasion, fluid exposure and environmental aging - critical for aircraft electrical system reliability.
Related standards
- ISO 2155 - Aircraft - Fire-resisting electrical cables - Performance requirements (normative reference)
- ISO 1967 - Aircraft - Electrical cables - Dimensions, conductor resistance and mass
Keywords: ISO 2156, fire-resisting electrical cables, aircraft cable tests, abrasion test, spark test, humidity cycling, hot cutting test, aviation cable testing.
