Electrical Wiring Interconnect System: Zone-by-Zone Design Guide
A “Systems Approach” to Aircraft Interconnect Cabling Commercial aircraft manufacturers treat large, interdependent equipment sets as systems: avionics, galleys, cabin
lighting, HVAC, IFE, navigation, and so on. The systems are designed with performance benchmarks tied to the environmental stress factors of the different zones of the aircraft where they are used. The cables and harnesses that interconnect these equipment sets, the Electrical Wiring Interconnect System (EWIS), is also now treated as a discrete system within the aircraft, subject to different requirements and specifications depending on the zones where it is located. In the past, the EWIS was treated more as an afterthought, with insufficient consideration given to best-practice design and zone-by-zone performance standards. The FAA, with the support of the principal aircraft manufacturers, has over the last several decades taken steps to change how interconnect technology is specified and managed. The key element of this effort was the move to treat wiring and associated interconnect components as a discrete system in its own right. The Electrical Wiring Interconnection System is now defined as: any wire, wiring device, or combination, including termination devices, installed in any area of the airplane, used to transmit electrical energy between two or more intended termination points. EWIS Performance
Historically, wiring and interconnect components were installed in aircraft in a “fit and forget” manner—without sufficient thought given to different aging and degradation impacts on a zone-by-zone basis. While the FAA has always outlined the top-level variables in EWIS degradation including aging, physical properties, installation and environment, and maintenance, cleaning and repair, it is only recently that these environmental stress factors have been exactingly evaluated according to aircraft zones. Service history shows it is not just the manner by which EWIS is installed that directly affects degradation, but more importantly material choices, environmental sealing components, EMC shielding technologies and so on that are geared for the unique stress factors found throughout the aircraft. Today’s EWIS
designers use DO-160 Environmental Conditions and Test Procedures for Airborne Equipment to ensure every element of the Electrical Wiring Interconnect
System meets or exceeds requirements for vibration, shock, ground survival temperature, pressure differential, operating temperature, and moisture in each specific zone of the aircraft.
Designing, Installing and Repairing EWIS
Many factors identified by the FAA must be considered when designing, installing or repairing an Electrical Wire Interconnect System, as follows:
Qwik Connect • April 2019
2
Powered by FlippingBook