By: Michael Traskos

Wire Diagnostic Equipment

September 17, 2019 Michael Traskos

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

Checking a Coaxial Cable for Damage with a Multimeter – Part II

September 11, 2019 Michael Traskos

In the last article, Lectromec introduced a damaged coaxial cable and tried three techniques to distinguish it from an undamaged cable. The standard multimeter tests (capacitance, inductance, and resistance measurements) found no appreciable difference.

The idea of this evaluation was to demonstrate that the classic multimeter, while a great tool, is not suitable for detecting damage to coaxial cables.

But we cannot run an article and leave it without a solution. In this article, we continue the testing of a damaged coax cable to see what technology, if any, can identify and perhaps locate the damaged section of cable.

Checking a Coaxial Cable for Damage with a Multimeter

August 23, 2019 Michael Traskos

The electronic multimeter is a great tool; invented in the 1920s, the multimeter has been used by millions of technicians and engineers seeking to measure circuits and troubleshoot electrical issues. So common are these tools now that it is almost impossible to consider a toolbox complete without one.

While these are great tools and can be employed in a million situations, they are not the magic tool that can diagnose every circuit. If only one thing is remembered from this article: multimeters are not the tool to use for coaxial cables

EWIS Physical Hazard Assessment

August 14, 2019 Michael Traskos

Aircraft system safety assessments are not a new concept. These safety assessments have a defined process for evaluating an aircraft which involve identifying its failure modes, top-level events, and eventual means to achieve an unsafe condition. Documents such as the SAE ARP4761 provide guidelines and methods for conducting the safety assessment process on civil airborne systems and equipment.

To follow the typical development cycle, the aircraft failure hazard assessment (FHA) is followed by the system failure hazard assessment and performed in parallel with the preliminary system safety assessments (PSSAs). This then evolves into the system safety assessments (SSA) and common cause analyses (CCAs). For those with a systems reliability background, this should all be second nature. For the rest of the community, these are often terms that we come across because of our work in this field.

Wires and Fuel Compatibility

August 7, 2019 Michael Traskos

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

Consequences of EWIS Implementation

July 24, 2019 Michael Traskos

In June 2019, Lectromec was asked to present at the USAF Mechanical Equipment and Subsystems Integrity Program (MESCIP) conference. With the electrical wiring interconnect system (EWIS) working its way into fleet sustainment activities, fleets now must take and apply the EWIS lessons learned.

Since the commercial segment has been subject to the 25.17XX EWIS regulations for more than a decade, the presentation examined the intended and unintended consequences of these regulations. For those seeking to integrate EWIS concepts into their fleet maintenance practices, this presentation gives an overview of the factors to be considered for your fleet.

The Potential 270VDC EWIS Component Failure Impact

June 27, 2019 Michael Traskos

The More Electric Aircraft (MEA) design concept has placed, and will continue to place, a greater importance on aircraft electrical power and the supporting Electrical Wiring Interconnection System (EWIS) to accomplish flight critical tasks. To take the greatest advantage of weight savings from using electrically powered components, higher voltages have been brought into the aircraft power architecture.

The goal of Lectromec’s research was to generate data of the potential impact of EWIS component failure. Even with high voltage systems having been fielded for a couple decades, much of the published research provides information on the failure of 115VAC and 28VDC power systems. This research performed by Lectromec sought to fill in that gap.

New Guidance for Wiring System Inspection

June 21, 2019 Michael Traskos

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

June 12, 2019 Michael Traskos

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)

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