Feature: Avionics
Electromagnetic compatibility (EMC) in avionics equipment
By Andrew Lawson, EMC chief engineer, TÜV SÜD E
lectromagnetic interference (EMI) affects all electrical and electronic devices, and managing it is especially when designing systems.
Interference ranges from poor-quality TV/radio reception, to computers crashing and onboard equipment failure. Sources of EMI can be natural, like static and lightning, or manmade intentional transmission and unintentional interference, emanating from electronics, electric power, communications, tools, machines, appliances, ignition systems, and many more. Avionics platforms and installations
have intentional high power transmitting sources, as well as other sources of interference. T ey must therefore be designed to ensure electromagnetic compatibility (EMC) with the natural and manmade electric, magnetic and electromagnetic environments in which they are to operate.
EMC standards Manufacturers must ensure their products meet safety legislation for their products and use in safety-related applications, and EMC standards contribute to ensuring the equipment’s functional safety. However, EMC testing alone does not provide safety assurance, since it’s not practical to test for all conditions. This means it does not consider all faults, misuse, ageing, production tolerances, environmental factors, full range of EM phenomena and levels over lifecycle, and testing uncertainty. Therefore, the focus should be on design and risk analysis, to identify how EMC susceptibility can cause the product to fail and the consequences (does it fail safe/unsafe?), in addition to any other design mitigations. Unfortunately, all avionics
electromagnetic phenomena are not covered by a single standard. RTCA DO-160 is an avionics environmental standard that includes a wide range
36 September 2024
www.electronicsworld.co.uk
of non-EMC phenomena, EMC test methods and limits for equipment. RTCA DO-357 is the User Guide to DO- 160, providing additional information to DO-160, for the associated test procedures and requirements. It also includes the rationale behind these requirements, guidance in applying them, complementing comments, possible troubleshooting techniques and lessons learnt from laboratory experience.
DO-160 Section 1 -Purpose and Applicability RTCA DO-160 Section 1 requires equipment performance standards to be specifi ed, which defi ne the minimum functional performance of diff erent categories of equipment. T e manufacturer can either adopt an RTCA or EuroCAEMOPS, or specify its own equipment specifi cation. T ese equipment performance standards are required during susceptibility testing, to ensure that the equipment continues to function correctly.
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