Abstract: A hybrid analog/digital autopilot utilizing analog inner loops in each control axis of the aircraft and a digital processor for providing outer loop commands and inner loop gain augmentation commands to the inner loops. The command from the processor to each inner loop is buffered by an adaptive rate limit circuit that initially transmits high frequency commands and over a predetermined time interval limits the command rate to a safe low value. Alternatively, the adaptive rate limit buffer transmits the high frequency command up to a predetermined attitude limit and thereafter transmits a command limited to a low safe rate.

Abstract: A circuit for overcoming variations in the output signals from a synchro device resulting from a.c. supply voltage variations includes means to provide a pulse train in which the pulse widths are modulated in accordance with supply voltage variations. A signal derived from a pair of synchro output terminals is applied to a rectifier/filter which is intermittently actuated by the pulse width modulated signal. The resultant d.c. signal is effectively divided by a factor proportional to the supply voltage so as to be independent of variations in that voltage.