Fault Tolerant Computer System for the A129 Helicopter

The A129 integrated multiplex system (IMS) is a highly reliable computer system designed to implement automatic flight control, navigation, system monitoring, and other flight-critical and mission related tasks. The reliability of the IMS has been achieved through the development of hardware-implemented and software implemented fault-tolerance techniques which exploit several unique architectural and hardware characteristics. This paper describes the fault-tolerance design philosophy, the IMS architecture, the fault detection and fault recovery techniques, and the hardware and software structures. Also presented is a Markov reliability analysis which was used to quantify the reliability of the system.