Hey LML gang,

We’re not sure how best to implement shielded wiring out to components in our airplane.  We’re wanting to ensure we don’t have a bunch of electromagnetic interference (EMI) that might mess with sensitive components like the ADHARS magnetometer.  Examples of EMI sources would be power lines running to motors (flaps, hydraulic pump, AC fans, AC compressor) and components with rapidly changing electrical current (strobe lights, HID lights).

My understanding is that Twisted Shielded Pair (TSP) cables are ideal for DC power transmission since the magnetic fields mostly cancel each other out and shield absorbs what’s left.  I’m not sure, though, how best to implement their termination at the ground/negative bus  and positive bus -- at the switch in most cases, then line running to the circuit breakers or fuse.  At some point, the separate conductors have to leave the shielded jacket and run to these separate connections which seems to defeat the benefits of the TSP.

Considering this, would it be better to use two individually shielded Tefzel jacketed wires and twist them together for the part of the path where they run together and then they each have their individual shields as they separate and run to their connections?

What are the best practices on actually implementing shielded wiring for power and signal transmission in our airplanes…?

Thanks,

Valin Thorn

Legacy Project

Boulder, Colorado