Reliability Through Redundancy

As requirements for automaticity cause airborne electronic systems to grow in complexity, reliability tends to become a limiting factor to system success. Because of the small probability that a large number of components will all operate successfully at once, even though individual reliabilities are high, complex systems are inherently unreliable. Efforts to better system reliability through improvement of component reliability rapidly reach the point of diminishing returns. A more fruitful solution to the problem is the redundant use of parts of the system in such a way that the function of a malfunctioning assembly is assumed by another assembly. The ``probability of no failure'' barrier is by-passed by this method, and a large improvement of in-flight reliability can be obtained with relatively small increase of system complexity. The potential of method is illustrated by a reliability analysis of a theoretical system, its application in design of a system is outlined, and techniques of detecting system failures and initiating corrective action are discussed.