Whitepaper
Experiences with level 5 requirements for indirect lightning tests to RTCA DO-160
This whitepaper from EMC Partner examines the practical challenges of conducting indirect lightning tests to RTCA DO-160 Section 22 at the highest severity level — Level 5. It begins by distinguishing between DO-160's two lightning-related sections: Section 22, which covers lightning-induced transient susceptibility tested at the equipment (LRU) level, and Section 23, which addresses direct lightning strikes on whole aircraft. The document explains how equipment location within an aircraft determines which of four protection zones applies and, consequently, which waveform sets and test levels are required — ranging from Level 1 for well-protected cabin environments to Level 4 or 5 for landing gear and propulsion controls in composite-heavy airframes. A key technical focus is the distinction between PIN injection and cable bundle tests, clarifying that generator impedance is defined solely by PIN injection parameters and that "Test" and "Limit" values for cable bundle tests are frequently misunderstood. The paper works through the generator output voltage demands of Waveform 3 at 1MHz and 10MHz, demonstrating how cable inductance can cause voltages to reach tens of kilovolts under certain conditions, making simultaneous achievement of both voltage and current test levels difficult. For longer, higher-energy waveforms (WF1, WF4, WF5), the paper notes that Level 5 single-stroke generators must deliver twice the output of Level 4 equipment, and that separate generator designs are typically needed for single-stroke versus multiple-stroke testing. The document concludes by recommending a modular, scalable approach to test equipment investment: rather than purchasing a dedicated Level 5 system for occasional use, laboratories are better served by expanding an existing Level 3 or 4 platform, which reduces costs, avoids retraining, and preserves flexibility for future requirements.