Voltage stress on Y capacitors from indirect lightning pulses 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 when exceeding the voltage handling capacity of filter components causing a short circuit to ground. In ED-14/DO-160, section 22, a number of waveforms and levels are defined which are used to check the airworthiness of avionics equipment. Depending on procedure and level, Y-capacitors are stressed by transient voltages which exceed their dielectric strength. The design engineer´s task is a properly select the type and voltage rating of capacitors. With moderate simplifications, a LCR-series network is justified to calculate the peak voltage dependent on the capacitance.