A Fail-Operative Stability Augmentation System with Self-Test Capability

A fail-operative stability augmentation system for the C141 jet transport aircraft yaw control axis is described. Triple-redundant sensors and signalling are used in conjunction with a dual-output, monitored servo system. Majority-rule voting logic, comprised of digital logic gates, operates directly upon conventional 400 cps suppressedcarrier data-modulated signals for fault rejection.

Self-contained means for semi-automatic preflight checkout as well as operational failure warning and disconnect provisions are described.

It is shown that the effect of redundancy is to reduce by several orders of magnitude the probability of a hardover failure occurrence.