7. Background

Over the years there have been a number of in-flight smoke and fire events where contamination sustained and caused the fire to spread. TCCA and TSB together with the FAA, NTSB and the JAA have conducted aircraft inspections and found wiring contaminated with items such as dust, dirt, metal shavings, lavatory waste water, coffee, soft drinks, and napkins. In some cases dust has been found completely covering wire bundles and the surrounding area.

Research has also demonstrated that wiring can be harmed by collateral damage when maintenance is being performed on other aircraft systems. For example a person performing an inspection of an electrical power center or avionics compartment may inadvertently cause damage to wiring in an adjacent area.

In recent years the regulatory authorities and industry groups have come to the realization that current maintenance practices may not be adequate to address aging non-structural systems. While age is not the sole cause of wire degradation, the probability that inadequate maintenance, contamination, improper repair, or mechanical damage has caused degradation to a particular EWIS increases over time. Studies by industry and government agency working groups have found that although EWIS management is an important safety issue, there has been a tendency to be complacent about EWIS. These working groups have concluded that there is a need to manage EWIS so that they continue to function safely.