S-3A avionics - Software revolution forerunner

Abstract

A review of the S-3A Project as the forerunner of software-inte grated avionics systems leads the author to conclude that the guideposts of technical change are signalling a revolutionary change in the system development process itself. Advanced avionics systems are viewed as software rather than hardware based, requiring a development process which takes advantage of the greatly in- creased flexibilities offered for designing to a fixed cost and schedule. Examples are cited from the successful S-3A program of software-fir st influences which have a highly beneficial impact on total system design and method of implementation. FOR two decades the avionics industry has witnessed the significant and steady-growing influence of digital com- puters and associated software in the design and develop- ment of advanced aerospace systems. Thus far, computer hardware (both analog and digital) for avionics applica- tions has established an excellent record in terms of per- formance, reliability, and over-all cost effectiveness. Av- ionics systems designers today, therefore, do not hesitate to draw liberally upon the cornucopia of digital computer hardware which now characterizes the electronics industry around the world. Curiously though, when the avionics re- quirement almost demands a centralized multiple proces- sor system whose resources are flexibly allocated in real time by a common executive program, red flags of deep concern are thrown up from nearly every quarter to steer the design in some other direction. Despite the obvious and closely associated progress in avionics software devel- opment, it remains the great inhibiting factor in integrat- ed avionics. Somehow, the U.S. Navy's S-3A Air Vehicle for ASW rose to challenge all the red Hags and to successfully inte- grate a complex array of electronics using a prodigious amount of central software. To those who, like the author, have seen a number of large-scale real-time software ef- forts begin in the same direction only to fall back after great expense to a simpler or distributed approach, the S-3A software development clearly represents a significant breakthrough. To the extent that the S-3A approach and basic archi- tecture are representative of where things are headed in integrated avionics, the author foresees a rapid and dras- tic change in the avionics development process for future systems. A simple projection of the growing influence of software on avionics development says that software will inevitably become pivotal for both the design and devel- opment of future systems. In observing what others are doing and saying along parallel lines, one finds an increasing number of responsi- ble people (and technical papers) in the field of avionics recognizing similar trends; however, it is not clear that a concensus exists as to what these trends mean. A paper by B. List1 of the Air Force Avionics Laborato- ry at Wright Field described these trends more broadly, yet succinctly, and with impressive insight. Emphasis is given here to the larger effects of what Mr. List referred to as the Software Revolution upon what must be an at- tendant revolution in our approach to avionics systems design and development.