Heads Up

Electrical Wiring Interconnection System (EWIS)

Electrical Wiring Interconnection System or commonly known in our industry as EWIS includes wiring systems and components such as harness bundles, clamps and connectors found throughout an aeroplane.

Historically, EWIS came to the forefront of public attention after the tragic in-service event involving a Boeing 747 midair explosion in 1996.

Shortly after, another event occurred with a MD-11 crashing into the ocean off the coast of Nova-Scotia.

Both of these unfortunate events involved a wiring fault of some kind and through other investigations of similar aircraft, a common concern towards the deterioration of aeroplane wiring was evident.

Conclusive regulatory changes followed through the Canadian Aviation Regulation (CAR) standard 525.1729 requirement for aeroplane manufacturer Instructions for Continuing Airworthiness (ICAs) documents to better inspect, repair and maintain aeroplane wiring.

With this edition of Feedback Magazine and in-line with the EWIS theme, you will notice 5 articles written to emphasize the importance of good maintenance practices and awareness towards this critical system.

Articles 20120308003 and 20120207004 defines the importance to follow all manual instructions when maintaining aeroplane wiring systems.

Article 20120302001 describes a scenario where system failure was imminent and the importance for thorough inspections.

Article 20120323002 describes an in-service snag which involved an unsuccessful resetting of a Circuit Breaker (CB) due to harness arcing.

Article 20120306008 captured an event involving extensive trouble-shooting and aeroplane downtime with several major component replacements upon which the findings were determined to be an error from previously performed maintenance.

These examples provide valuable lessons for maintainers on the importance of proper wiring maintenance practices in order to support the continued safe operation of our aeroplanes.

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