Redundant Flight-Critical Control System Evaluation. Analog and Digital Systems Performance Comparison

The U.S. SST prototype commercial airliner under development from 1967 to 1971 employed redundant flight-critical control systems as an essential part of the airplane's airworthiness. The flight control system electronics were analog for the flight-critical stability augmentation functions and digital for the automatic flight control functions. The digital system, through an automated preflight test function, also served to establish the integrity of the flight- critical elements. The SST program was terminated before these systems became operational. This study deals with the mechanization of redundant electronic systems. Specifically, the study evaluates analog and digital electronic designs for implementing a triplex fail-operational flight-critical control system. The primary subjects studied were analog and digital systems' multiple failure fail-operational capabilities and preflight integrity check requirements. This document deals with analytical and laboratory performance evaluations of the systems studied. Specific areas covered include basic filter processing, closed loop operation, fault tolerant performance, sensor signal selection/failure detection, and digital computer timing and memory relationships.
Report on SST Technology Follow-On Program. See also AD0913365 and ADB000281.