Automatic flight control system with operatively monitored digital

Abstract

A dual channel, fail-operative automatic flight control system is disclosed in which each channel includes a totally monitored digital computer for operating upon sensor input data to provide command signals to the aircraft surface control actuators. The operative program for each computer is repetitively executed to effectively provide continuous control. The program is organized into a plurality of tasks to be performed by the computer with program segments associated with the respective tasks and a program routine for determining that all of the tasks have been completed for each program iteration. If non-completion of a task is detected, the program enters a failure routine which stops execution of the program. The program also includes a routine for generating a dynamically varying pattern in accordance with the continuously reiterated execution of the program. The system includes a detector for determining that the correct pattern is being generated and shuts down the system upon detecting a failure of the computer to generate the correct pattern. All of the instructions of the computer instruction repertoire operatively utilized in the system are employed to control the program flow whereby failure of an instruction to operate properly will cause the program to flow into an abnormal path thus causing the task completion program routine to indicate failure and stop the computer. Additionally, the system utilizes further techniques such as dual data and program memory banks to perform redundant computations, all of the techniques in combination providing an automatic flight control system with two autonomous fail-passive channels, the two channels providing a fail-operative system.