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CFR 25.1717 – Circuit Protection and EWIS
Circuit protective devices are circuit components whose purpose is to disconnect power to the circuit in the event of a fault condition. The fault conditions vary based on the circuit type, attached equipment, and power capacity of the attached circuit. Some common fault conditions include overheating, overcurrent, and electrical arcing.
To meet the diverse needs of varying circuit designs and functions across electrical systems, several types of circuit protection are available. Each type has benefits and drawbacks, and it is important to evaluate each to determine the best option for a given electrical system. Read more
Are New EWIS Regulations Needed for High Voltage EWIS?
Fluid Immersion Testing of EWIS Components
From fuel to hydraulic oil to sodas, aircraft wires and cables are exposed to a wide range of fluids and, generally, the insulations must not show degradation that would impact their airworthiness. Material compatibility is important for all parts of the aircraft and the wiring system is no exception. The means to assess material compatibility between fluids and wires/cables is done with fluid immersion testing.
Fluid immersion testing is straightforward but requires a lot of materials, a lot of prep work, and a lot of hands-on attention to detail. The fundamental idea of fluid immersion testing is for components to be submerged in the fluid and observed for any changes to the material or components. Some test details and the impacts of the test results are covered here.
Read moreEWIS High Voltage Certification
Integrating EWIS into Fleet Sustainment and MECSIP
EWIS and Aircraft Maintainability
The maintainability of the electrical wiring interconnection system (EWIS) is integral to the longevity of an aircraft. EWIS maintainability affects not only the EWIS itself, but any nearby system whose maintenance access is restricted by the location or function of the EWIS. Thus, high maintainability of the EWIS allows for faster, more efficient, and more precise maintenance of surrounding equipment and systems.
Original aircraft design must comply with EWIS regulations in the development stage to ensure long-term maintainability. It is important to know which regulations apply and which standards to follow when designing an aircraft to determine the appropriate maintenance requirements.
Here we will explore the requirements of some of the more common standards for EWIS maintainability in aircraft design.
Read moreEWIS Yule Log
Review of EWIS for Sustainment
EWIS Physical Hazard Assessment
Aircraft system safety assessments are not a new concept. These safety assessments have a defined process for evaluating an aircraft which involve identifying its failure modes, top-level events, and eventual means to achieve an unsafe condition. Documents such as the SAE ARP4761 provide guidelines and methods for conducting the safety assessment process on civil airborne systems and equipment.
To follow the typical development cycle, the aircraft failure hazard assessment (FHA) is followed by the system failure hazard assessment and performed in parallel with the preliminary system safety assessments (PSSAs). This then evolves into the system safety assessments (SSA) and common cause analyses (CCAs). For those with a systems reliability background, this should all be second nature. For the rest of the community, these are often terms that we come across because of our work in this field.
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