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Certification

Have we Reached the End of Aging Aircraft Wiring Systems? – Part II

At the start of the last article, the question was posed, “Is it possible that aircraft wiring reached a point where aging/degradation is a thing of the past?” In that article, four elements were identified that must be satisfied for wires/cables to be considered as age-free. The insulation and conductor aging factors were examined in the last article, and here we consider the remaining two: Design limits and random shocks. Read more

25.981 is Not a Barrier – Part 2

FAA regulation 25.981 covers the requirements of fuel tank ignition prevention. While there are numerous elements that must be considered as part of the 25.981 regulation, this is a Lectromec series of articles, and here we focus on the electrical hazards that must be identified and mitigated as part of certification. Read more

25.981 is Not a Barrier

One area of aircraft certification where electrical energy and risk have always been considered is the fuel system. While it is obvious that limiting the exposure of fuel to electrical energy is advantageous, how this gets addressed from a safety and certification perspective is far from obvious. Read more

Testing the Performance of AFCBs

Arc Fault Circuit Protection has been a technology that dates back to the 1990s. Despite this not being a new technology, the breath of its implementation is still limited. The device owes its inception to arcing events that occurred on in-service aircraft. Because of these events, the wiring community sought to create wiring that was arc track resistant, and the circuit protection community sought to cut off the arcing event before too much energy was released. This has been captured in the requirements of AS5692 for AC circuit protection, and AS6019 for DC protection Read more

Maximum Harness Ampacity

The fundamental concept here is harness ampacity: the maximum amount of current transferred down a wire harness without exceeding the temperature rating for any component. Read more

Circuit Protection Selection Guidance

Circuit protection devices have existed since 1864; one would think that selection of circuit protection would be a straight forward task. However, it is not. NASA developed a seven-step process for circuit protection selection and both EN3179 and AS50881 provide some guidance. In a past article, Lectromec began to consider the differences between two major […] Read more

What is an EWIS Qualified Wire?

This is a question that Lectromec regularly receives. The reason for this question is that a parts-supplier or system-integrator is looking to find wires in compliance with EWIS requirements. Since there are so many ways to evaluate any component, the important question to consider is if a defined requirements list for aerospace wire exists? Here, […] Read more

Connector Failure Rates – Part #2

In Lectromec’s previous article, we introduced a basis for estimating connector failure rates. The framework utilized the failure information available from military handbook MIL-HDBK-217. In this article, we continue to review the parameters of the failure rate function and implications on how slight changes in the environment can have a dramatic impact on a connectors […] Read more

Connector Failure Rates – Part #1

Coming up with failure rates of electrical components is always a difficult task. Historically, when failure modes and effects analyses were created for aircraft systems, the level of detail of EWIS component failures were severely lacking. Some organizations would create a single failure number for an entire circuit, regardless of the wires or connections made […] Read more

Designing for Relays

Power transfer through aircraft or any electrical system requires components that have the capability to turn on and off. These switches, contactors, transistors, and electrical relays that route power through the aircraft are life limited parts. Whether from a design or sustainment view, understanding how these components degrade over time and what to look for […] Read more