AS4372 – Building a Wire/Cable Specification
While it is possible to start from scratch and develop an independent set of tests and performance requirements, there are existing standards that can be used to expedite the process. Read more
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Results for: wire system certification
Light Weight and Normal Weight Wire Constructions
Saving weight is a large part of any aircraft design. Naturally, the electrical system is not exempt from the goal of shaving off a couple of pounds. This often comes in the form of looking for lighter connectors, lighter clamps, and also lighter wire constructions. Those that have done this have undoubtedly come across two classifications of wire construction: “Normal weight” and “light weight”. Of course, if the EWIS has to go on a diet, then the “light weight” construction looks like a good substitute for the “normal weight”… after all, why would the wire be called “light weight” if not for satisfying weight requirements. Read more
Impact of Secondary Wire Harness Protection on Heating
If you are standing outside on a cold winter day, would you be warmer in a T-shirt or in a jacket? The answer is obvious, but somehow that ‘obvious answer’ is obscured when thinking of aircraft wire harness design. A common question of OEMs and aftermarket modifiers is: how much of an impact (if any) does secondary harness protection have on wire harness heating?
Lectromec took time this last week to put together a representative harness and run tests to generate data on the thermal impact of three secondary wire harness protection schemes. While this data is not representative of every wire harness configuration, it does provide a basis for determining if additional testing (or simulation) are needed for your application.
Read moreSAE Wire and Cable Committee Meeting Update – Fall 2019
The SAE wire and cable committee held their fall 2019 meeting in San Diego this year. As with every committee meeting, a lot of technical areas were discussed, progress was made, and some new ideas/problems are emerged. As we do after all these meetings, we put together a highlight of some of the talking points from the meeting.
Read moreWire Diagnostic Equipment
Finding wire faults/damage is not an easy task; now consider that problem across an entire aircraft. In-situ testing of wires/cables has always been viewed as something of a challenge to the industry. Given the branching that most harnesses undergo, the various wire lengths, splices, and numerous termination conditions, it can be difficult. Attempts to automate some of the testing has come to the development of Automatic Wire Test Sets (AWTS [pronounced “Eh-Wits”]).
Because there are so many ways to test a wire harness, the US military sought to create a performance standard to cover the general ideas and best practices of this equipment. Here, we review the standard and some of the performance features that can be expected when using equipment in compliance with the standard
Read moreWires and Fuel Compatibility
Whether by design or by accident, some wires in an aircraft will be exposed to jet fuel. Because of this, it is necessary to be prepared and select wires/cable types that will not suffer adverse effects of the exposure. Considering the impact of fuel on wiring is not idle musing about wiring systems; to quote the FAA AC120-97A, “Since 1959, there have been 18 fuel tank explosions on transport category airplanes”. Read more
New Guidance for Wiring System Inspection
Back in November 2018, the US Navy released the second revision to the military handbook on “Guidelines for inspection of aircraft electrical wiring interconnect systems” (MIL-HDBK-522). This handbook is a guide for the aircraft EWIS inspection and provides a lot of detailed examples of wiring evaluation from beginning to end of the EWIS. Read more
Common Questions About Kapton® Wire
Love it or hate it, the fact is that Kapton® insulated wires will be on aircraft for at least another couple of decades, and because of this, we should learn to live with the insulation type. Part of living with it is understanding it.
If you have questions that you would like to see answered, please send them to Lectromec or add them to the comments section below. We plan to add to this article as the questions arise. Read more
Principles of EWIS System Safety (25.1709)
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
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