Blog

Principles of EWIS System Safety (25.1709)

June 4, 2019 Michael Traskos

Of the regulations encapsulating the 25.17XX EWIS group, none is more complicated than 25.1709. This regulation, consisting of only 31 words, can be the result of thousands of hours of labor, hundreds of pages of documentation, and requiring inputs from just about every system group working on the vehicle. If you step back from the regulation and ask, “What is necessary to show compliance?” it comes down to several factors. Here, we review some of the basic principles of 25.1709, where it impacts and interacts with other systems in the vehicle. Read more

Impact of Wires Used as Ladders

May 22, 2019 Devon Gonteski

Ideally, an aircraft’s EWIS aging is considered and monitored over time, but something as simple as gripping and pulling a wire or cable can change its electrical performance, specifically conductivity and resistance. Read more

Latest Developments in Wire and Cable (Spring 2019)

May 14, 2019 Michael Traskos

Wire and cable standards are never proactive, but reactive to industry needs, and as the aviation world moves to high power systems, wire and cable must catch up to ensure the products are available for long reliable service life. Twice a year the SAE wire/cable community comes together to slowly push the standards and industry guidance forward; this year, New Orleans was the setting.

During this three-day meeting, several topics were discussed impacting the next generation of aircraft designs. Here, we cover a couple of these developments.

Thermal Life of Wires and Cables

April 22, 2019 Michael Traskos

While there is a wide range of products from which to choose, across many of these specifications there is a common element: maximum temperature rating. Here, we walk through a couple of the methods for assessing a wire/cable’s maximum temperature rating. At the end of this article, we delve into weaknesses of this assessment method and elements that should be considered when selecting a wire for your high temperature application. Read more

Where EWIS Stops

April 8, 2019 Michael Traskos

Having well-defined and recognized system boundaries is the best means to ensure an analysis of that system is robust and does not leave any analysis gaps. Without an established limit and assigned responsibilities, arguments will ensue as to who is the responsible party and time/effort will be wasted with duplicated analysis.

Because an aircraft’s wiring touches nearly all of the systems, it can be confusing to understand where the system starts and stops, and this has led to confusion as to the responsible party for the wiring system design and/or maintenance. Some organizations have seen the responsibility fall on the electrical power systems teams, others, avionics. Regardless of who takes up the responsibility, a clear definition of the wiring system’s physical and logical boundaries must be agreed upon. Thankfully, there are several industry documents that can be relied upon.

High Voltage Impact the Aircraft Wiring System

March 18, 2019 Michael Traskos

For aerospace applications, high-voltage power is a rapidly growing interest and being addressed across several industry technical committees. The basic idea is that the power generation is increasing the supplied voltage and creating a need for the electrical wiring interconnects systems (EWIS) to have components designed to sustain these higher voltages for the entire length of the aircraft life. Just as it should not be expected for a connector to operate in a 300°C environment if it is only rated to 150°C, a connector should not be expected to perform perfectly with voltages exceeding its voltage rating. Read more

How Much Does the Aircraft Environment Impact Wire Life?

March 1, 2019 Michael Traskos

When looking to select any aircraft component, typically the first means of down selecting from the wide variety of components that exists is based on the component’s performance characteristics i.e. can it perform the function to support the system. Next, the question then evolves to selecting those components that are best suited for the environmental conditions. This last part is more than just selecting the parts that are rated for the environmental conditions but also those that will have a long service life in those conditions. Ideally, the part will be reliable the entire service life of the aircraft and not require any replacement or additional maintenance; however, that usually is not the case (see Lectromec’s article on the immortal wire/cable). Read more

SwissAir 111 Incident

February 16, 2019 Devon Gonteski

The year of 2018 was yet again another substantial year in commercial air travel. The first quarter of 2018 saw commercial flights carry over 202 million passengers in the US, approximately 8 million more than in the first quarter of 2017. Air travel remains increasingly popular, accessible to the public, and statistically the safest way to travel. This level of safety has been earned through decades of groundbreaking innovation, sometimes undeniably spurred by the desire to avoid repeating past tragedy.

An impactful and memorable incident that caused the industry to reevaluate its processes and procedures was the crash of Swissair Flight 111. Occurring almost two years after the Trans World Airlines Flight 800 (TWA800), the Swissair Flight 111 and TWA800 shared a common issue: wiring system failure.

Is my aircraft wiring serviceable?

January 29, 2019 Michael Traskos

A concept employed in the civil engineering field is that of serviceability. At its core, a structure should only remain in-service as long as it is serviceable. A serviceability limit should be based on measurable performance criterion that, if exceeded, remove it from service. In limit state design, the structure fails its serviceability if the criteria of the serviceability limit state are not met during the service life with the required reliability. Read more

International Test Standards for Aircraft Wire Tests

January 15, 2019 Michael Traskos

Frequently, Lectromec’s articles have focused on wire and cable testing from US-focused standards such as the SAE and US military (MIL) documents. While these are standards frequently cited, there are other standards organizations that support the aerospace wiring community. Thankfully, many of the standards share a common base and, as is the case with many of the SAE standards, these have been harmonized with European standards. In this article, we will review some of the European wire/cable test standards, variation from similar test methods, and their availability in Lectromec’s lab. Read more