Task four of military handbook MIL-HDBK-525 (also incorporated into the mechanical subsystems integrity program standard MIL-STD-1798) outlines a set of considerations and procedures for the assessment of an aircraft electrical system specifically for the service life extension program (SLEP). The important factor is to ensure that resources are not wasted on this effort and that the outputs from this assessment provide actionable value to your organization, maintenance of the aircraft, and the long-term sustainment of the fleet. With that as a preface, this article covers values of wire system degradation analysis and what you can expect to get as output.
Current Component Health Assessment
Look at historical data, particularly maintenance data from Electrical Wiring Interconnection System (EWIS) failures, provides a partial view into the wiring systems health. While it is certainly possible to build trends and analysis on the maintenance data, it is difficult to ascertain the current state of the components. By performing selective tests on a limited number of aircraft electrical system parts, it is possible to identify the level of degradation for those components.
For example, if a component that has degraded 30% in its electrical properties, should this remain on an aircraft? What if the component performance has degraded 30% but still exceeds the part’s minimum performance requirements?
Just because something has degraded does not mean that it should be thrown away and replaced. By understanding the current health of your wiring system, it is possible to identify what areas of the aircraft have undergone greater stress and if immediate actions are needed. This can help to support decisions made during heavy maintenance cycles or aircraft retirement.
The next helpful step is to determine how well your aircraft is performing against other aircraft of a similar type and construction.
One of the insights Lectromec has from performing so many EWIS assessments is our body of knowledge on the performance and degradation speed for a variety of platforms with a variety of service histories. Combined with our knowledge of wire system degradation and degradation models, this makes it possible for health assessments to be compared to similar aircraft. Furthermore, this experience and tool set generates expected EWIS component performance results thereby identifying if an aircraft or fleet is performing better or worse than similar aircraft. Long-term, this can have positive impacts in directed maintenance, reduced in-service incidents, and potential resale value of the aircraft.
The acceleration of EWIS component degradation is never constant. It is based on the maintenance, service history, and operational conditions in which the EWIS exists. The degradation models and current health of the EWIS components make it possible to predict future performance.
If you had data showing that your wiring system would start to experience rapid degradation in eight years and would likely require a full aircraft rewiring, how likely is it that you undergo heavy maintenance for that aircraft in year six? Certainly, many factors come into play as part of that decision, but knowing there is a cost and potential impact to aircraft reliability because of wire system degradation should not be ignored.
Using the right models and degradation analysis as part of EWIS assessment can generate the data necessary for making just those type of decisions. Degradation models for EWIS components used by Lectromec make it possible to predict the reliability up to 20 years from the test date. Dozens of platforms have used this technology and degradation assessment to direct their EWIS sustainment.
Getting the Most Value from your EWIS
MIL-HDBK-525 task four outlines a set of considerations for EWIS component degradation and assessment. The outputs from this work are not just data but information that can be used for the sustainment of the aircraft and improve the aircraft reliability. Also, the information can be used to direct future business decisions and fleet sustainment needs.
If you are interested in finding out more about EWIS degradation and how to implement it within your own fleet, contact Lectromec.