I have a G500 going in a jet with altitude preselect enabled and it's going to be connected to a S-tec 55X. When the owner sent me all the autopilot components, he included an ST-645 annunciator which, correct me if I'm wrong, has to be there for the FD to work. He also sent me an ST-360 altitude selector with the 55X. If I have the altitude preselect enabled in the G500, do I still need the ST-360? If I did need the S-tec item for preselect, wouldn't it be the SA-200 which is an altitude preselector and not the ST-360 which is an altitude selector?
