Sofema Online (SOL) presents this analysis to emphasise why early-stage prioritisation of EWIS is vital—not just for certification success, but for long-term operational safety, reliability, and maintainability.
Modern aircraft are tightly packed with overlapping systems, hydraulics, fuel, air conditioning, data cabling, high-voltage lines, and more. This high-density environment creates a risk that wiring systems will be compromised if not addressed early in the design process.
In modern aviation, prioritising EWIS during the design phase is not optional; it’s essential. To avoid introducing risks that may only emerge after years in service, with consequences that can range from minor maintenance issues to catastrophic failure
Why Prioritise EWIS Early:
• Poor routing compromises safety and increases electromagnetic interference (EMI) risks. Once systems are fixed in place, redesign becomes expensive and complex.
• Failure to design for compliance triggers redesigns, delaying certification.
• EWIS compliance covers insulation integrity, flammability resistance, labelling, separation distances, and more. These cannot be retrofitted efficiently.
Note of Concern If EWIS routing is deferred, it ends up being forced into suboptimal paths, increasing the risk of interference, mechanical wear, or even fire exposure. (Rerouting becomes disruptive and costly, often requiring removal of insulation blankets or disassembly of key structures.)
• Safety and EMI Exposure Poor routing leads to close proximity between wiring and high-risk systems (fuel, hydraulics, oxygen).
>> EMI risks include interference with flight controls, degraded data signals, and sensor malfunction.
>> Rerouting becomes disruptive and costly, often requiring removal of insulation blankets or disassembly of key structures.
• Human Factors and Maintainability Wiring must be accessible, traceable, and serviceable for the life of the aircraft.
>> Wiring must be inspected and maintained throughout the aircraft lifecycle.
>> Enables accessible routing, minimising technician error and damage during maintenance.
>> Supports safer troubleshooting, reduces downtime, and lowers long-term costs.
• Compliance and Certification Risk, Non-compliance in areas such as:
>> Insulation integrity
>> Flammability resistance
>> Wire labelling and separation
>> Clamp spacing and installation quality
>> Can result in any of the following:
• Redesigns
• Delays in certification
• Additional tests and documentation revisions
• Regulatory non-acceptance, even late in the program
• Holistic Integration with SMS and Safety Culture - With the introduction of SMS into EASA Part 21J (via Regulation 2022/201), EWIS design must now consider:
>> Hazard identification specific to wiring degradation
>> Design risk assessments incorporating past service data
>> Feedback loops from in-service experience and safety occurrence reports
Important Note - Wiring design is not just an engineering task, but a safety-critical decision process.
• Lifecycle Cost and Reliability - EWIS design choices directly influence:
>> Aircraft dispatch reliability
>> Long-term MRO costs
>> Exposure to unscheduled maintenance events
>> Poor routing or component selection may result in:
• Bending-induced failures
• Environmental degradation
• Moisture ingress or arc tracking
Summary – Design engineers must prioritise EWIS design because:
• It ensures compliance with EASA/FAA regulations and avoids certification delays
• It allows optimised routing and segregation within tight spaces
• It reduces EMI risk and enhances system integration
• It facilitates maintainability and reduces lifecycle costs
• It aligns with SMS principles and safety culture expectations
For EWIS Classroom, Webinar or Online Training please see Sofema Aviation Services and Sofema Online or email team@sassofia.com.
