Evolution from analog to digital integration in aircraft avionics - a time of transition

Abstract

In the late 1960 and early 1970s the U.S. Air Force was undergoing major growing pains as airborne digital computers became available, but the sensors were still all analog. The introduction of digital computers and software as a central avionics integration tool forced the need of complex high-speed analog-to-digital and digital-to-analog converters. These A/D converters were a major contributor to reliability problems and were a bottleneck for future upgrades and modifications. The future of digital integration was in jeopardy if a viable solution could not be found. The introduction of the digital multiplexed data bus provided both the needed flexibility and modularity that allowed digital integration to move forward. The digital time-division multiplex data bus is a tool to aid in system integration. Originally introduced to save avionic hardware interconnect wiring weight and ease computer interface requirements, it was considered the cornerstone of digital avionics. Through the use of the multiplexing technique many other benefits can be reaped. The resultant standard electronic interface permitted a building block approach to systems architecting and integration. Retrofits became easier, standard interchangeable sensors became a reality, and maintenance was greatly improved. Flexibility was probably the data bus' greatest attribute; reliability, built-in-test, redundancy and graceful degradation were added benefits