The System Forty is a single-axis roll stabilization autopilot which includes heading pre-select, turn command (which will give up to 90% standard rate turn), VOR / LOC tracking, back course tracking, and a gain enhancement feature for tracking GPS Navigation analog left / right deviation signals.
To utilize GPS roll steering (GPSS) commands, an additional ST-901 GPSS converter may be required to feed the autopilot with compatible steering signals. The ST-901 GPSS converter is not required for GPSS when integrating to an Aspen EFD system or Garmin G500/600 EFIS.
A compatible DG or HSI is required for the heading pre-select function or when adding the optional ST-901 GPSS converter.
Building block concept allows upgrading to a System Fifty or FiftyFiveX two-axis system.