SIST EN 3475-407:2009

Overview

EN 3475-407:2009 is a CEN aerospace series standard that defines two test methods to determine the flammability characteristics of finished electrical cables for aircraft use. The standard is intended to be used together with EN 3475-100 (general test procedures) and supports regulatory considerations including FAR 25 / JAR 25 requirements for transport-category aeroplanes. It focuses on practical flammability evaluation to inform product acceptance, certification and safety engineering decisions.

Key Topics

• Scope and purpose: Specifies two distinct flammability test methods for finished cables and references EN 3475-100 for general requirements.
• Test chamber and burner: Requires a draught-free test chamber (minimum dimensions given) and a Bunsen-type gas burner with adjustable flame characteristics.
• Specimen preparation: Conditioning of specimens at (50 ± 5) % RH and (21 ± 3) °C for at least 24 hours; specific specimen lengths and end stripping are defined for each method.
• Method 1 (mounted, inclined test): Flame applied to 900 mm specimens at two exposure durations (15 s and 30 s) with a specified burner/wire arrangement to set the flame temperature. Acceptance includes no flaming droplets and cessation of flaming within product-standard times and a maximum burnt length of 50 mm.
• Method 2 (vertical, stripped end test): Uses 450 mm specimens with 50 mm of insulation removed and a 38 mm soft yellow flame applied for 15 s. Acceptance requires no flaming droplets, cessation of flaming within 10 s after removal of the burner, and a maximum burnt/charred length of 75 mm.
• Measurement and criteria: After each test the time to flame extinction and the burnt length are recorded; acceptance is based on absence of flaming droplets and specific length/time limits.

Applications

• Product qualification: Use the tests to demonstrate cable resistance to ignition and limited flame propagation for aircraft wiring harnesses.
• Design validation: Inform material selection and insulation designs to meet flammability performance targets.
• Regulatory compliance: Provide test evidence to support compliance with airworthiness standards and product standards that reference EN 3475-407:2009.
• Quality control: Integrate into manufacturing or incoming inspection protocols for finished cable batches.

Related Standards

• EN 3475-100 - General test methods for aerospace cables (to be used in conjunction with this part).
• FAR 25 / JAR 25 - Airworthiness standards referenced for transport-category aeroplanes.

For engineers and compliance teams, EN 3475-407:2009 provides a clear, reproducible framework to assess the ignitability and burning behaviour of finished aircraft cables, enabling consistent evaluation of flammability performance and safer aircraft electrical installations.