Progress in the use of automatic flight controls in safety critical applications

Extract

High authority automatic flight control systems are now in wide use in both transport and combat aircraft. These have required the development of failure survival system architectures, and techniques in safety assessment to ensure that the risk of fatal accidents attributable to the automatic control aspect is acceptably remote.

Most of the current systems are analogue in nature, and employ sufficient redundancy to survive at least one failure during operation. Future systems will employ quadruplex or triplex-monitored architectures, capable of surviving at least two failures, and will be mainly digital in concept. The design and safety assessment techniques developed for analogue systems have been adequate for current systems, but the new digital technology and more extensive use of systems in safety critical applications will demand further development of the various aspects involved.

A major contribution to the design and safety assessment of safety critical systems was made during the past two decades in the programmes for the development of automatic landing for civil aircraft, culminating in the system in the Anglo-French Concorde.