December 2025: Essential Updates to Aircraft Electrical Contacts and Fiber Optic Cable Standards

In December 2025, the aircraft and space vehicle engineering sector witnessed the publication of two critical new standards designed to strengthen quality, reliability, and connectivity in aerospace electrical and optical systems. These fresh releases—FprEN 3155-075 for quadrax electrical contacts and FprEN 4641-001 for 125 µm cladding optical cables—signal significant advances in how aerospace systems are designed, implemented, and maintained. Whether you oversee compliance, design, or procurement, understanding these latest requirements will be key to ensuring your operations meet the highest international benchmarks.

Overview / Introduction

The aircraft and space vehicle engineering industry continually evolves to address emerging technology, increasing complexity, and absolute safety requirements. International standards serve as the backbone for harmonized practices, facilitating interoperability, quality assurance, and regulatory compliance. This month’s updates introduce robust new specifications for both electrical connection systems—vital for signal integrity and safety—and high-precision optical cables, increasingly critical in modern avionics and data transmission.

This article highlights:

• What’s new in the December 2025 standards
• Technical requirements and changes
• Practical impacts for implementation and compliance

Detailed Standards Coverage

FprEN 3155-075 – Quadrax Electrical Contacts for Aerospace Connections

Aerospace series - Electrical contacts used in elements of connection - Part 075: Contacts, electrical, quadrax, size 8, female, type E, crimp, classes P, R and S - Product standard

This newly published standard provides the definitive product specifications for female quadrax electrical contacts, shielded, size 8, type E, with a 100 Ω characteristic impedance for aerospace connection systems. Applicable to crimp-style terminations in classes P, R, and S (with particular details for class R), these quadrax contacts directly connect to critical systems where high-frequency signals must be transmitted with minimal loss or impedance mismatch.

Key requirements covered include:

• Physical characteristics, dimensions, and identification
• Allowed materials and surface treatments for long-term reliability
• Tooling and wiring best practices
• Precise crimp and installation procedures
• Required tests for insertion loss and impedance (with references to EN 2591-222 and EN 2591-223)

This standard is used in tandem with EN 3155-001 and references male contacts in EN 3155-074. Aerospace OEMs, electrical systems integrators, and component suppliers engaged in digital data and signal transmission (e.g., fly-by-wire and Ethernet systems) must comply.

Practical implications:

• Guarantees compatibility and performance in mission-critical aerial and spaceborne environments
• Mandates specific gauge checks, qualification tests, and approved crimp tools (including SAE AS22520 and AS81969)
• Requires robust marking practices for traceability and maintainability
• Supersedes EN 3155-075:2022 with clarified test sequences, alternative design options, and updated references

Key highlights:

• Comprehensive physical, material, and performance requirements for quadrax contacts
• Enhanced testing—now including mandatory insertion loss and impedance tests
• Broader design acceptance, allowing updated front-area hood geometry

Access the full standard:View FprEN 3155-075 on iTeh Standards

FprEN 4641-001 – Technical Specification for 125 µm Fiber Optic Cables

Aerospace series - Cables, optical, 125 µm diameter cladding - Part 001: Technical specification

FprEN 4641-001 establishes the essential general characteristics, qualification processes, quality assurance protocols, and standardized test methods for optical fiber cables with 125 µm cladding, tailored for aircraft and aerospace applications. The standard emphasizes cable reliability and high-performance data transmission in harsh environments, reflecting modern avionics’ demands for lightweight, noise-immune, high-bandwidth communication.

Covers key areas such as:

• Cables’ physical and constructional requirements (materials, configuration, color coding, mass)
• Single and multi-fiber structures: tight, semi-loose, and loose constructions
• Performance and endurance tests (in line with EN 3745-100, IEC/EN 60793 series)
• Robust QA, qualification, and acceptance requirements
• Storage, marking, delivery, and packaging conditions

Aerospace manufacturers, cable assemblers, and avionics designers deploying optical networks must implement these specifications when selecting or certifying fiber optic cables.

Practical implications:

• Ensures consistent quality and traceability across all fiber optic cabling used in aerospace systems
• Mandates compliance with stringent environmental and mechanical testing
• Facilitates qualification and batch acceptance, minimizing risk of in-field failures
• Supersedes EN 4641-001:2018 with updated references, expanded test groups, and new definitions

Key highlights:

• Defines and distinguishes tight, semi-loose, and loose fiber cable designs
• Detailed test method requirements (mechanical, optical, and environmental)
• Qualification and production quality control processes enable streamlined certification

Access the full standard:View FprEN 4641-001 on iTeh Standards

Industry Impact & Compliance

Adoption of these updated standards across the aircraft and space vehicle engineering sector will:

• Ensure interoperability between OEMs, integrators, and suppliers
• Reduce risk of system incompatibility and signal integrity failure
• Support compliance with both regional (European) and international regulations
• Drive supply chain confidence through clear qualification and quality benchmarks

Compliance considerations:

• All new projects after publication must specify these standards for relevant components and cable assemblies
• Existing long-term programs should assess gaps and plan for phased compliance
• Suppliers must immediately update production and test protocols to reflect new test sequences and qualification procedures

Risks of non-compliance:

• Elevated potential for system failures, grounding, or rework costs
• Legal and contractual liability with regulatory authorities or major airframers
• Reduced competitiveness in international tendering and supply partnerships

Technical Insights

Across both standards, several technical themes emerge:

• Rigorous qualification and acceptance testing: Organizations must invest in equipment and processes for impedance, insertion loss, and environmental testing
• Standardized materials and configurations: Mandated use of specified metals, coatings, and construction for connectors and cables reduces variability
• Traceable marking and documentation: Requirements for clear identification enhance maintenance, auditing, and field support
• Best practices for implementation:
  • Regular training for engineers and technicians on crimping, fiber handling, and test procedures
  • Detailed audits of supplied goods against standard clause checklists
  • Use of only accredited laboratories for qualification and acceptance testing

Testing and certification tips:

1. Develop a compliance matrix cross-referencing each clause for procurement and quality checks
2. Maintain calibration and validation records for all required test tools, including electrical and fiber-optic apparatus
3. Liaise with notified bodies or recognized certification services to streamline qualification

Conclusion / Next Steps

The December 2025 standards for aircraft electrical contacts and optical cables mark a decisive enhancement in aerospace system reliability and safety. FprEN 3155-075 and FprEN 4641-001 deliver comprehensive, actionable requirements for engineering, quality, and procurement teams.

Key takeaways:

• Immediate adoption strengthens competitive positioning and compliance
• Robust engineering and QA practices are essential for successful implementation
• Staying informed about evolving standards maximizes operational resilience and safety

We recommend:

• Reviewing and updating your internal specifications
• Sharing these standards with engineering, quality, and supply chain stakeholders
• Visiting iTeh Standards for complete and authoritative standard documents and continued updates

Stay proactive—ensure your teams and partners are aligned with the latest in international aerospace standards. Explore these documents in full on iTeh Standards and reinforce your commitment to quality, safety, and innovation.