An electrical wiring interconnect system (EWIS) is the

wiring Electrical wiring is an electrical installation of cabling and associated devices such as switches, distribution boards, sockets, and light fittings in a structure. Wiring is subject to safety standards for design and installation. Allowable ...

system and components (such as bundle clamps, wire splices, etc.) for a complex

system A system is a group of Interaction, interacting or interrelated elements that act according to a set of rules to form a unified whole. A system, surrounded and influenced by its environment (systems), environment, is described by its boundaries, ...

. The term originated in the

aviation Aviation includes the activities surrounding mechanical flight and the aircraft industry. ''Aircraft'' includes fixed-wing and rotary-wing types, morphable wings, wing-less lifting bodies, as well as lighter-than-air craft such as hot air ...

industry Industry may refer to: Economics * Industry (economics), a generally categorized branch of economic activity * Industry (manufacturing), a specific branch of economic activity, typically in factories with machinery * The wider industrial sector ...

but was originally designated as Electrical Interconnection Systems (EIS). The change from EIS to EWIS was done to emphasize the focus on the actual wires and wiring of the systems throughout

aircraft An aircraft is a vehicle that is able to fly by gaining support from the air. It counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines ...

Background

Prior to the aviation accidents of

TWA Flight 800 Trans World Airlines Flight 800 (TWA800) was a Boeing 747-100 that exploded and crashed into the Atlantic Ocean near East Moriches, New York, on July 17, 1996, at about 8:31pm. Eastern Daylight Time, EDT, 12 minutes after takeoff from John F. K ...

and SwissAir 111, the wiring on aircraft was a 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. The committee included a number of key organizations and businesses including ATA,

NASA The National Aeronautics and Space Administration (NASA ) is an independent agency of the US federal government responsible for the civil space program, aeronautics research, and space research. NASA was established in 1958, succeeding t ...

Northwest Airlines Northwest Airlines Corp. (NWA) was a major American airline founded in 1926 and absorbed into Delta Air Lines, Inc. by a merger. The merger, approved on October 29, 2008, made Delta the largest airline in the world until the American Airlines ...

Boeing The Boeing Company () is an American multinational corporation that designs, manufactures, and sells airplanes, rotorcraft, rockets, satellites, telecommunications equipment, and missiles worldwide. The company also provides leasing and product ...

Airbus Airbus SE (; ; ; ) is a European Multinational corporation, multinational aerospace corporation. Airbus designs, manufactures and sells civil and military aerospace manufacturer, aerospace products worldwide and manufactures aircraft througho ...

FAA The Federal Aviation Administration (FAA) is the largest transportation agency of the U.S. government and regulates all aspects of civil aviation in the country as well as over surrounding international waters. Its powers include air traffic m ...

, and Electromechanical 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 excerpt 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 ( Swissair Flight 111) airplane crashed into the
Atlantic Ocean The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth's surface and about 29% of its water surface area. It is known to separate the " Old World" of Africa, Europe ...
, killing all 229 people aboard. Although an exact cause could not be determined, the presence of re-solidified
copper Copper is a chemical element with the symbol Cu (from la, cuprum) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkis ...
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 Corrosion is a natural process that converts a refined metal into a more chemically stable oxide. It is the gradual deterioration of materials (usually a metal) by chemical or electrochemical reaction with their environment. Corrosion engine ...
, improper wire installation and repairs, and contamination of wire bundles with metal shavings,
dust Dust is made of fine particles of solid matter. On Earth, it generally consists of particles in the atmosphere that come from various sources such as soil lifted by wind (an aeolian process), volcanic eruptions, and pollution. Dust in homes ...
, and
fluids In physics, a fluid is a liquid, gas, or other material that continuously deforms (''flows'') under an applied shear stress, or external force. They have zero shear modulus, or, in simpler terms, are substances which cannot resist any shear ...
(which would provide fuel for fire) were common conditions in representative examples of the ‘‘aging fleet of transport airplanes.’’ "

The FAA funded a number of studies involving the analysis of the current state of wiring on aircraft, the

deterioration Deterioration may refer to: * Worsening of health * Physical wear See also * Decadence (disambiguation) * Degeneracy (disambiguation) * ''Deteriorata'', a parody of ''Desiderata'' * Decay * Decline Decline may refer to: *Decadence, involves a ...

processes of wiring systems, tools to detect wire failure, and ways of quantifying and mitigating the damage from an electrical arc. In 2009 the European Aviation Safety Agency issued 3 "Acceptable Means of Compliance", AMC 20-21, AMC 20-22 and AMC 20-23 dealing in turn with the maintenance procedures, the training and the documentation that had to be introduced by Maintenance and Repair Organisations to reduce the probability of serious incidents or accidents caused by wiring failure. AMC 20-22 is almost exactly similar to the US FAA Airworthiness Circular 120-94.

EWIS Aircraft Electrical Systems Reliability

The term electrical system refers to those parts on the aircraft that generate, distribute and use electrical energy, including their supports and attachments. The satisfactory performance of an aircraft is dependent upon the continued reliability of the electrical system. Reliability of the electrical system is proportional to the quality of maintenance received, the correct independent part selection and the supervised installation of each electrical component in the aircraft as explained in the FAA advisory circular 43.13-1B - Acceptable Methods, Techniques, and Practices Chapter 11. Electrical component selection is a critical step to ensure the correct operation in any aircraft electrical system. Components need to be selected for their electrical specifications and properties as well as for the extreme conditions these components could be exposed. Inspection and testing of every single component plays a major role in the EWIS regulations to guarantee the safety and reliability of the system. Correct engineering design, planning and coordination with the manufacturers of each electrical component will secure the proper installation of each component. The correct installation of the components in the aircraft and the manufacturing procedures are requirements of the EWIS regulations. Once the aircraft has an airworthiness certificate and has reached an entry into service status, the maintenance of the aircraft’s electrical systems will play a key role to guarantee the reliability of the systems and the safety of flight.

References

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