Commercial protocols in aerospace applications present designers with challenges of balancing the standard against special needs of the application. In the physical layer, the cables used for Gigabit and 10 Gigabit Ethernet, USB, IEEE 1394 and others are a prime example of this balancing act. The standards for these protocols detail electrical and structural requirements for the cables. One goal of standards is to characterize cables with enough specificity that they can be confidently plugged into the application.
For commercial applications, this approach works admirably. The additional concerns for aerospace applications lead designers to reconsider this convenient plug-and-play approach. Their primary driver is reducing size and weight at every opportunity in the aircraft. As the amount of data in both aircraft operation and passenger services increases dramatically, so does the number of conductors needed to carry the data. In aggregate, commercial cables make an attractive target for size and weight reductions. At the same time, industry-standard cables may not possess the desired mechanical or environmental performance, especially the demanding requirements for low smoke generation, toxicity and flammability in closed spaces where safe exit may be difficult or impossible. Republished from Design News (August 2014)