When using the autopilot in conjunction with the GPS530 to track a “Direct to” course (not a flight plan course), it will be necessary for you to use “HDG” mode on the autopilot, not “NAV” mode. While this operation is authentic, it may catch some of you by surprise! You will also need to be sure that the CDI button on the GPS530 is pressed so that “GPS” appears in green on the display. See page 3-44 of the GPS 530 manual for further information.
The following quote comes directly from the programmer of the autopilot and GPS530, DreamFleet's Nick Jacobs, who programmed these units for both our 310, and the Flight One Cessna 421 product (they are essentially the same units on both aircraft):
"Direct to won't delete any flightplan waypoints, that functionality doesn't exist in FS2002, at least not with the interface Microsoft supplies - we can read but not modify flightplan data.
However, to fly a direct-to on autopilot, you need to engage HDG mode, click the NAV/GPS button on the GPS (CDI button) to show GPS in green text.
To return to flightplan tracking, switch the autopilot to NAV mode and make sure the NAV/GPS switch on the PANEL is set to GPS, just like any default aircraft."