ABSTRACT
Fault-tolerant designs are required to ensure safe operation of digital avionics systems performing flight-critical functions. This chapter discusses the motivation for fault-tolerant designs, and the many different design practices that are evolving to implement a fault-tolerant system. The designer needs to make sure the fault tolerance requirements are fully defined to select the design concept to be implemented from the alternatives available. The requirements for a fault-tolerant system include performance, dependability, and the methods of assuring that the design, when implemented, meets all requirements. The requirements must be documented in a specification of the intended behavior of a system, specifying the tolerances imposed on the various outputs from the system [Anderson and Lee, 1981].
