Introduction to Electrical Wiring Interconnect System (EWIS) EASA Driven Requirements

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SofemaOnline (SOL) considers the regulations driving EWIS compliance within the European EASA jurisdiction.


The origins of EASA's focus on EWIS can be traced back to various incidents in the aviation industry that highlighted the risks associated with electrical faults leading to in-flight smoke and fire events. These incidents underscored the need for rigorous maintenance and training practices to prevent similar occurrences in the future.

As the global aircraft fleet aged, the aviation industry faced challenges related to the deterioration of electrical wiring. This deterioration could lead to electrical failures, short circuits, and even in-flight fires.

Complexity of Modern Aircraft Systems: The increasing complexity of aircraft systems, coupled with more demanding performance requirements, placed additional stress on EWIS components, necessitating advanced maintenance and monitoring techniques.

Notable Accidents and Incidents: High-profile accidents, such as the TWA Flight 800 explosion in 1996, highlighted the potential risks associated with faulty electrical wiring. Investigations into such incidents often pointed to EWIS as a critical factor.

EWIS Developments

The development of measures to address the Aviation Electrical Wiring Interconnect System (EWIS) within the European Union Aviation Safety Agency (EASA) framework has been guided by a series of regulations and guidelines focused on ensuring the safety and reliability of aircraft electrical systems.

EASA's approach to EWIS is comprehensive, covering various aspects of design, maintenance, and training. The agency emphasizes the importance of organizational responsibility in managing compliance with these regulatory requirements. This includes adhering to established working practices and procedures for EWIS, as well as specific training mandates detailed in AMC 20-22.

A key component of EASA's requirements is the Enhanced Zonal Analysis Procedure (EZAP), which is essential for ensuring the continued airworthiness of EWIS components. EZAP focuses on a detailed examination of the aircraft's zones to identify potential risks and degradation factors affecting the wiring systems. This approach is outlined in AMC 20-21, which serves as a program to enhance airplane EWIS maintenance.

Furthermore, EASA mandates that all large airplanes covered by CS-25 shall demonstrate compliance with EWIS regulations without exception, as stated in the CS-25 Amdt 5 (or later) according to part 21A.101. This includes a broad range of aircraft, emphasizing the universal applicability of these safety standards.

Training is another critical aspect under EASA's EWIS requirements. It is mandatory for maintenance staff to undergo specific EWIS training to maintain competence standards, as outlined in AMC 20-22. This training program is crucial for ensuring that personnel are equipped with the necessary knowledge and skills to effectively manage and maintain aircraft EWIS.

In summary, EASA's requirements for EWIS encompass a range of measures designed to ensure the safety and reliability of aircraft electrical systems. These include stringent maintenance procedures, comprehensive training programs, and a commitment to upholding high standards across the industry. Through these measures, EASA aims to address the challenges posed by the complex and critical nature of EWIS in modern aircraft operations.

Next Steps

Sofema Aviation Services ( and Sofema Online ( provide both initial and recurrent EASA compliant regulatory training. – Please see the websites or email [email protected]



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