What is mean Ewis:
Definition, [Ref. § 25.1701 (a)] EWIS is: Any wire, wiring device, or combination of these, including termination devices, installed in any area of the airplane for the purpose of transmitting electrical energy between two or more intended termination points…
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 amount 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.
Prior to the aviation accidents of TWA Flight 800 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, Northwest Airlines, Boeing, Airbus, FAA, 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, 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.