Now you can fly an entire flight plan hands-free with the cutting edge technology of the GDC31 Roll Steering Converter. This autopilot accessory produces a Roll Sum Steering (RSS) signal from the RS-232 or ARINC 429 data available from your GPS receiver. The GDC31 implements the same steering law used for years in Inertial Navigation Systems to guide air transport aircraft around the world. Using the GDC31 annunciator/selector switch, simply select between heading mode and GPS mode. In GPS mode, the GDC31 couples to the autopilot's heading channel, calculating the correct enroute flight path and intercept angles from the GPS course data. In heading mode, the autopilot operates as always, tracking the heading bug. The GDC31 interfaces with S-TEC, King, Century, and other autopilots, and provides DAC customers with an affordable way to retrofit existing aircraft systems with state of the art capability.