Primary flight computers for the Boeing 777

Abstract This paper follows one on the Boeing 777 primary flight computers, which was presented at ERA's 1992 Avionics Conference. The current paper focuses on the system requirements software implementation, and operational consequences of a fault-tolerant system. Beginning with the reasons for fly-by-wire, the paper goes on to describe the overall architecture of the Boeing 777 primary flight computer system. Particular emphasis is placed on the control modes and the way in which envelope protection functions are implemented. After a brief description of the hardware, the paper describes the software life-cycle process, including design, coding and test, highlighting the way in which the integrity of the software has been achieved. The fault-tolerant aspects of the design, and the advantages that these provide to operators, conclude the paper