I have an STEC 30 coupled to a GTN 650 and an Aspen pfd. I realize the STEC 30 alone can't do intercepts for approaches but can track a VOR or localizer signal in trk-lo or trk-hi mode. I also understand that having GPSS via the Aspen allows the STEC to use GTN 650 data to intercept. I'm trying to figure out how to make the most of this setup during training and real world IFR flying. After poring through the STEC 30 and Aspen manuals, I'm left with two unanswered questions:
1. After intercepting an LPV final approach course, the STEC manual says to use trk-hi mode to follow the course. But if I use GPSS to intercept, why not just leave it in heading mode with GPSS? In the real world, I imagine one would even prefer to use GPSS to fly an ILS approach after switching the nav signal display to the ILS? The STEC 30 autopilot's ability to track the localizer directly in trk-hi sounds more finicky than heading mode with GPSS.
2. What am I left with if the Aspen fails? This failure will likely be simulated on the check ride. Obviously GPSS function and flying in heading mode will be gone. But will the STEC 30 still be able to track a VOR or localizer in trk-lo or trk-hi mode based on the NAV signal from my GTN 650 or SL30? I suspect not, but couldn't figure this out definitively from the manuals. I'd like to have some clue what the answer should be before I try it.