EN 3475-704:2007

Overview

EN 3475-704:2007 - "Aerospace series - Cables, electrical, aircraft use - Test methods - Part 704: Flexibility" is a CEN/ASD‑STAN European standard that specifies two laboratory methods to assess the flexibility and bending aptitude of completed aircraft electrical cables. The standard sets different procedures depending on cable cross‑section: Method 1 for cables ≥ 5 mm2 and Method 2 for cables ≤ 5 mm2 (10 AWG). Unless a product standard states otherwise, Method 1 applies. EN 3475-704:2007 is intended for use together with EN 3475-100 (General test methods).

Key topics and technical requirements

• Scope and applicability:
  • Two flexibility test methods keyed to cable cross‑section (5 mm2 / 10 AWG threshold).
  • Applies to completed aircraft electrical cables; used for qualification, acceptance and comparison.
• Method 1 (larger cables, ≥ 5 mm2):
  • Prepare a loop from the cable with diameter = 40 × maximum cable diameter (loop formed in normal winding direction).
  • Two ends stripped over 5 mm and soldered or spliced.
  • A compression/crushing device crushes the loop by 25% of its diameter (vertical crush preferred).
  • Crush stroke = 10 × maximum cable diameter; crush speed 100 mm/min.
  • Test performed at ambient temperature and recorded; the applied force F to achieve 25% crush must be below the value defined in the product standard.
• Method 2 (smaller cables, ≤ 5 mm2 / 10 AWG):
  • Specimens ~200 mm long; straightened by hand or by hanging with a specified mass in an oven (temperature per product spec, not exceeding rated max).
  • Test performed within 1 hour at ambient (20 °C ± 5 °C).
  • Use a mandrel/bend rig (mandrel diameters and straightening loads given in the standard’s Table 1 - e.g., AWG 10 uses 50 mm mandrel and 50 N).
  • Apply mass to bend the cable downward through 90° ±10°, hold 5 min, record mass; after removal, record recoil after 5 min.
  • The mass and recoil angle must not exceed values in the individual cable specification.

Practical applications and users

• Who uses EN 3475-704:2007:
  • Aerospace cable manufacturers and suppliers for product qualification and design verification.
  • Test laboratories and quality assurance teams performing routine acceptance or type tests.
  • Aircraft OEMs and systems integrators specifying cable performance in procurement and installation.
  • Certification bodies evaluating compliance with aerospace electrical requirements.
• Typical uses:
  • Comparing flexibility across cable designs or materials.
  • Ensuring cable bend performance meets installation and maintenance needs (routing in tight bundles, primary/secondary structures).
  • Defining pass/fail criteria in product specifications and supplier contracts.

Related standards

• EN 3475-100 - Aerospace series - Cables, electrical, aircraft use - Test methods - Part 100: General (mandatory companion standard).
• EN 3475 series - other parts cover electrical, environmental and mechanical test methods for aircraft cables.

Keywords: EN 3475-704:2007, aerospace cable flexibility test, aircraft electrical cables, flexibility test methods, Method 1, Method 2, EN 3475-100, cable bending aptitude, mandrel test, compression crushing test.