Electrical wire interconnection system

EWIS, or Electrical Wire Interconnection Systems, refers to the wiring system and components (such and bundle clamps, wire splices, etc.) for a complex system. The term originated in the aviation industry but was originally part EIS, or Electrical Interconnection Systems [http://www.tc.faa.gov/its/worldpac/techrpt/artn06-17.pdf] . The change from EIS to EWIS was done to emphasize the focus on the actual wires and wiring of the systems throughout aircraft [ [http://www.aerohabitat.org/link/2006/24-03-2006%20-%20Aavv,%20Risk%20assessment%20for%20aircraft%20EWIS%20(0.8MB).pdf] ] .

Background

Prior to the aviation accidents of TWA800 [ [http://en.wikipedia.org/wiki/TWA_Flight_800] TWA Flight 800 Wikipedia article] and SwissAir 111 [ [http://en.wikipedia.org/wiki/Swiss_Air_111] SwissAir 111 Wikipedia article] , the wiring on aircraft was an issue minor concern. In response to these accidents, the Aging Transport Systems Rulemaking Advisory Committee (ATSRAC) was chartered to gather industry leaders examine the current state of aging aircraft systems; one of the main areas examined included EWIS [ [http://www.caasd.org/atsrac/] ATSRAC committee homepage] . The committee included a number of key organizations and businesses including ATA, NASA, Northwest Airlines, Boeing, Airbus, FAA, and Lectromechanical Design Company. Many of the results from the ATSRAC committee shaped the FAA's regulatory reaction to the handling and certification of EWIS. The following is an except from the FAA’s regulations released November 8, 2007 governing aspects of EWIS on aircraft as to the reason for the increased concerns regarding EWIS:

“Safety concerns about wiring systems in airplanes were brought to the forefront of public attention by a midair explosion in 1996 involving a 747 airplane. Ignition of flammable vapors in the fuel tank was the probable cause of that fatal accident, and the most likely source was a wiring failure that allowed a spark to enter the fuel tank. All 230 people aboard the airplane were killed. Two years later, an MD–11 airplane crashed into the Atlantic Ocean, killing all 229 people aboard. Although an exact cause could not be determined, the presence of re-solidified copper on a portion of a wire of the in-flight entertainment system cable indicated that wire arcing had occurred in the area where the fire most likely originated.

Investigations of those accidents and later examinations of other airplanes showed a collection of common problems. Deteriorated wiring, corrosion, improper wire installation and repairs, and contamination of wire bundles with metal shavings, dust, and fluids (which would provide fuel for fire) were common conditions in representative examples of the ‘‘aging fleet of transport airplanes.’’ " [ [http://edocket.access.gpo.gov/2007/E7-21434.htm] FAA Regulations on the certification and maintenance of aircraft wiring systems ]

To developed the research to reach the conclusions, the FAA funded an number of studies involving the analysis of the current state of wiring on aircraft, the deterioration processes of wiring systems [ [http://www.mitrecaasd.org/atsrac/meeting_minutes/2002/2002_04_FAA_Wire_Degradation_Study.pdf] Presentation describing the goals of the Wire Degradation Project] , tools to detect wire failure, and ways of quantifying and mitigating the damage from an electrical arc. [ [http://www.lectromec.org/Lectromec%20ADMT%202007Paper.pdf] Description of FAA project to predict the potential damage caused by wire failure.] .

References