AS23053 Dimensional Life of Heat Shrink Tubing

December 15, 2021 Laura Wishart

We are told that low humidity and cool temperatures are the best way to extend component life, but even in such conditions not all components can sit on a warehouse shelf indefinitely awaiting the day of installation. One of the more susceptible EWIS components to aging on the warehouse shelf are heat shrink tubing. Here, we examine concept of dimensional life of heat shrink tubing.

Addressing the Big Questions of Partial Discharge

June 11, 2021 Michael Traskos

In this high-voltage present, wires and cables must address new challenges, perhaps the most notable is partial discharge (also referred to as corona). This article discusses the fundamentals of partial discharge, its impacts on wiring design, and test methods used to assess a component’s partial discharge performance. The PD may occur between (1) the conductor and insulation, (2) within void in the insulation, (3) between insulation layers, or (4) between the insulation surface and shield. Read more

Detailed Discussion of MIL-STD-1353 (Part 1): Tin Plating

April 21, 2021 Laura Wishart

The mating of the electrical wiring interconnect system (EWIS) is a non-trivial task. Between the functional requirements (the correct number of pins, sizing of contacts, etc.), there are also the performance requirements (operational environment, corrosion resistance, impedance matching, etc.). This is then further complicated by installation requirements (sizing), maintenance requirements (mating/demating cycles), and regulatory requirements (limitations of materials that can be used). Obviously, adding a connector to a wire harness is not a five-second activity. This article looks at the MIL-STD-1353 specific requirements for tin usage in aircraft connectors. Read more

Axial Stability (Longitudinal Change) After Thermal Exposure

The Axial Stability test evaluates the ability of wire/ cable insulation to resist longitudinal dimensional change while cycling between high and low temperatures. A test sample undergoes five cycles of exposure to heat, cold, and room temperature, remaining at each temperature for the amount of time it takes for the sample to reach thermal equilibrium […] Read more

EN2235 Review and Comparison to NEMA 27500

February 4, 2021 Laura Wishart

Cables are complicated engineered products. They range from the simple twisted pair (simple but requiring precise twists per foot) to the complicated signal and data cables used in many applications. Just as the NEMA 27500 cable standard is the go-to cable for many aerospace applications in the US, the EN2235 shares the same status in the EU. The requirements for these cables are outlined in this article. Further, we examine the differences between the EN2235 cables and the NEMA 27500 cables. Read more

Contamination

The contamination test measures the quality factor (Q) of a test sample. The specimen length for the contamination test ranges between 2-4 feet of PVC type jacket, depending upon the diameter of the cable being tested. One end of the specimen is cut square, while the other end is prepared to provide the shortest possible […] Read more

Impacts of Sanitizing Fluids on Wiring

December 8, 2020 Michael Traskos

Key Takeaways COVID-19 has resulted in a higher concentration of sanitizing products being used on aircraft. The FAA has released special airworthiness information bulletins highlighting the concerns with the application of sanitizers on aircraft. An internal Lectromec study was performed to determine effects of sanitizing fluids on wires. Wire and cable are exposed to a […] Read more

WPAFB Wire Study

October 14, 2020 Michael Traskos

Key Takeaways Publicly available recorded data compares many of the commonly used aerospace wire types. Corona extinction and inception voltages of cables decrease drastically with an increase of elevation. Many insulation types display a significant decrease in mechanical durability at increased temperatures. Modern wires of the AS22759 family are incapable of stopping 270 voltage DC […] Read more

Conductor Resistance ASTM B193

August 13, 2020 Michael Traskos

The measurement of resistance seems to be a trivial task. Hook up a standard handheld multimeter with two probes and attach the probes to either side of the device or component that you want to measure. For the most part, this process works well. More correctly, for devices with resistances between 2 Ohms and 1M Ohm, this is a good technique, however, once the resistance values get really high or really low, the process becomes a little more complicated. While the basic physics remains the same (Voltage = Current * Resistance), getting the setup to correctly measure the component requires attention to detail. Read more

The Impact of a Short Circuit on Conductor Performance

March 17, 2020 Laura Wishart

Over-current and shorting are an ever-present risk to power wires and cables. The hope is that circuit protection can quickly respond to over-current conditions fast enough to prevent any damage to the circuit components. Wire conductors have a temperature rating, limited by the plating, because that is the established temperature for long-term reliability. But what happens when a single wire is exposed to repeat over-current conditions? Does the latest generation of circuit protection sufficiently protect the wiring? Read more

Search