25.981 is Not a Barrier – Part 2

September 18, 2018 Michael Traskos

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

September 8, 2018 Michael Traskos

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

High Current Testing

August 14, 2018 Tristan Epp Schmidt

Several things can go wrong when a wire or cable is subjected to an electrical current exceeding its design limitation and none of them are good. These include, but are not limited to, melting of the insulation, smoking, insulation degradation, promotion of intermetallic growth between the plating and conductor, melting of the conductor, melting of the conductor plating, and conductor embrittlement. Thankfully, if the wire/cable is being used within its temperature and current ratings, the wire should experience very little of the above phenomena. Read more

DO-160, EWIS, and EMI

August 6, 2018 Michael Traskos

Designing a circuit diagram for a system comprised of Line Replaceable Units (LRUs) is usually a straightforward process: identify the inputs and outputs of the system and connect them with wires and cables. Taking that simple high-level circuit diagram and implementing the physical design into an application can be quite difficult. This requires the proper connectors, optimized the physical routing, and ensuring negligible impact from electromagnetic interference (EMI). From an implementation perspective, it cannot be understated how much EMI can impact system performance ranging from degraded performance to make a system completely inoperable. Thankfully, there are test methods to evaluate the susceptibility of electromagnetic interference of a wire harness design. Read more

Selecting Aircraft for Inspection and Work Unit Codes

July 24, 2018 Michael Traskos

What documents and standards are there for justifying the evaluation of an aircraft’s EWIS? There are actually several. Read more

Testing the Performance of AFCBs

July 16, 2018 Michael Traskos

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

Galvanic Corrosion and Red Plague

July 7, 2018 Devon Gonteski

Some have brushed the issue aside saying that they have never seen it, thus it is not a problem. To put the issue of red plague into perspective, a worst-case estimate suggests as much as 3% of braided silver-plated copper shields have some degree of red plague. Across the aerospace industry, this equates to millions of dollars each year in scraped products, rewiring, and maintenance actions. Read more

Condition Based Maintenance and Risk Quantification

June 29, 2018 Michael Traskos

Aircraft maintenance is usually broken down one of two ways: by physical zones or by systems. The mechanical equipment and subsystems integrity program, also known as MECSIP, is the US Air Force’s approach to addressing aircraft sustainment and maintenance through focused system evaluation. Last week, MECSIP managers from many of the Air Force fleets gathered in Dayton, Ohio to discuss the latest developments, procedures, and technologies for addressing the MECSIP needs of their fleets. Read more

Unwanted Energy Storage in Cables – Dielectric Constant

June 22, 2018 Tristan Epp Schmidt

A good wire insulation is more than just preventing electrical energy from leaving the conductor; there are dozens of properties that are important to its performance and usability. One of these that is easy to overlook is the wire’s dielectric constant. Read more

Maximum Harness Ampacity

June 15, 2018 Michael Traskos

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

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