This paper presents a description and treats the integration of a new triple channel multi-rate Digital Automatic Flight and Inlet Control System (DAFICS) into the SR-71 aircraft. Predicted airframe longevity to the year 2000 and aging automatic flight control/air inlet control analog systems dictated a modernization program to insure supportability over the life span of the aircraft. Aerodynamic consideration and development rationale is provided. A functional system description identifies the systems being replaced. Simulation, hardware/software development, redundancy management and flight experience is presented. Finally, digital and analog control comparisons are made and improvements discussed.