Redundant Flight-Critical Control System Evaluation: Analog and Digital Systems Failure Analyses and Preflight Test Designs

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 failure modes and effects analysis, and preflight test requirements of the systems studied. Report on SST Technology Follow-On Program. See also ADB000281 and ADB000284.