The SAE is holding their 8D committee meeting this week in Louisville, KY. For those unfamiliar with the SAE 8A/D, this group develops, reviews, and updates modern aerospace wire standards. It is a committee filled with aircraft OEMS, military personnel engaged in maintenance, certification, and testing of wiring, chemical manufacturers, and wire constructors.

Among the tasks that have been taken up by this group include developing new arc damage assessment methods. The goal of these methods is to provide a standard method for assessing the damage from electrical arcing events. The reason for this is that, as of today, there has not been industry guidance on how to determine what an acceptable (safe) separation distance between wiring harnesses and other components (e.g. other wiring, structure, hydraulic lines, fuel tanks).

The work is still in the initial development phases, but the working group seems to be directing the effort toward guidance to those seeking FAA certification of their Electrical Wire Interconnection System (EWIS) with FAA regulation 25.1709. In particular, provide guidance and recommendation to those seeking the physical damage assessment described in AC 25.1701.

It might be years until the final test methods are released, but progress is being made. We will provide updates here as the method comes closer to final release.

Lectromec has been performing arc damage assessments for more than 20 years and has the facilities to perform arc damage assessments simulating most aerospace configuration. If you are looking to gather data on the electrical arc damage possible of your platform, whether for design validation or certification, contact Lectromec.

Recently when going through our file servers, we came across this old video of tests performed by Lectromec for the NTSB showing the properties of arc track testing of aromatic polyimide wire (often called Kapton®). It provides a good overview of arc track testing, the dangers of damaged wires.

Two things should be noted when viewing this video:

1) Although polyimide wires were used in these tests, it is possible to do damage to wires in the harness with more modern wire insulations.

2) In these tests, a 10kVA generator was used. Modern aircraft typically have larger generators making it possible to create significantly more damage than seen in this video.

To find out more about arc track testing and damage assessment, visit www.lectromec.com

During a recent SAE meeting, the topic was brought up regarding the standard voltage rating on much of aerospace wire currently available.  As of right now, most of the wire is rated to 600volts, yet there is no test in the specifications to qualify wires to this level.  This has not been much of a concern in the past, because most systems operated at 115V/208V.  But, as the systems are starting to use high voltage for distribution through the aircraft and start pushing the rating for the wire, this can become more of a concern. 

The SAE committee is forming a task group and will to investigate this issue further.