State-of-the-art avionics achieves very good reliability, and the electronics in the current generation of communication and navigation satellites is sufficiently good to allow a design-life of around 10 years. Nevertheless, failures will arise. The purpose of failure analysis is to identify the consequences if a particular module does encounter a failure, and to ensure that, by system redundancy or through operational procedures, the effect and/or its probability of occurrence will be acceptably safe. This paper is a contribution to the discussion on the strength and weakness of redundancy in satellite-based Communication, Navigation and Surveillance (CNS) systems as envisaged by the International Civil Aviation Organization (ICAO) to be an integral part of the future air navigation system. This particular paper makes a comparison with today's terrestrial-based systems.
