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

Do I Need to Replace My 15/20/30/40 years Old Aircraft Wiring?

December 27, 2018 Michael Traskos

As aircraft age, it is natural to contemplate the aircraft condition as to how much longer the equipment can be maintained. Typically, after the engines, structures, environmental control system (ECS), navigation, landing gear, interiors, flight controls, and fuel system are considered, the question will ultimately appear, “do I need to replace my wires that are 15/20/25/30 years old?” While it would be nice if there were a simple answer, like all engineering, it comes down to the evaluation of the system. Here, we answer this question. Read more

Use of MIL-T-81490 cable in place of a MIL-DTL-17 cable

December 20, 2018 Michael Traskos

A common ‘go-to’ cable for RF applications is the MIL-DTL-17 cable. Many of the MIL-DTL-17 cables are rated to 1 GHz, some to 12.4 GHz (like M17/128), and only a couple at 20GHz (e.g. M17/130 and M17/133 – a word of caution with the /130 and /133 constructions: these are unjacketed cables with an exposed external conductor/shield). There is the M17/205 construction that is spec’d for up to 50GHz, but that comes with a caveat: attenuation. The accompanying figure shows the attenuation per 100ft of M17/205 cable; while the attenuation does rise quickly with higher frequencies, the specification does not provide any attenuation limits beyond 10 GHz. Read more

EWIS Instructions for Continued Airworthiness

November 27, 2018 Michael Traskos

Here we look at the last 95% of an aircraft life: operation and maintenance. In this, we review the regulatory requirements around EWIS instructions for continued airworthiness (ICA) and some of the resources that can be used to ensure a smooth certification process for your wiring system. Read more

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

November 5, 2018 Michael Traskos

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

Have we Reached the End of Aging Aircraft Wiring Systems?

October 17, 2018 Michael Traskos

The way some in the aerospace industry maintain their aircraft wiring system can only lead an external observer to reason that aircraft wiring is impervious to damage with a life-span greater than the sun. When considering this thought, the question arose, “It is possible that aircraft wiring reached a point where aging/degradation is a thing of the past?” Read more

Mechanical Performance of Cables at Low Temperatures

October 5, 2018 Michael Traskos

The environmental extremes under which wiring exists in aircraft can rapidly degrade materials that are not prepared or designed for those conditions. Without a doubt, high-temperature ranges that are typically considered for aircraft wiring eliminate most wire insulation types that are suitable for ground-based home applications. Lectromec has covered several types of high-temperature tests in past articles. But at low temperatures, what tests exist to help identify which wires are ideally or adequately suited for aerospace applications? One of the tests that investigates the performance of wires in cold conditions is known as the cold bend test. Read more

Should Polyimide Insulated Wire be Trusted?

September 25, 2018 Michael Traskos

The history of polyimide insulated wire is one that has numerous opinions and a lot of misconceptions. After several incidents involving polyimide wire on aircraft in both military and commercial, many within the aerospace industry refused to put any polyimide insulated wire/cable onto the aircraft they design/maintain. As is often the case with components involved in incidents, a lot of facts and myths get jumbled together. Read more

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