Design of transient voltage suppressors for digital inputs of avionics devices in indirect lightning tests according to ED-14/DO-160

Transients due to lightning strikes on an aircraft's fuselage impose stress on the input filters of electronic equipment. Permanent damage can occur if the voltage handling capabilities of components are exceeded. In ED-14/DO-160, section 22, a number of waveforms and levels are defined that are used to check the airworthiness of avionics equipment. Depending on procedure and level, Y-capacitors are stressed by transient voltages that exceed their dielectric strength. The design engineer's task is to properly select the type and voltage rating of capacitors. With moderate simplifications, an equivalent LCR-series network can be justified which enabled the calculation of maximum current and energy into the suppression element.