In the sim session, T. was flying an IFR flight from Anoka (KANE) to
T. loaded the approach into the Garmin 430 in the sim and activated it, with CORDY as the IAF. Unfortunately none of the Garmin 400/500 series downloadable simulators have a database current enough to contain the GPS-13/RST approach, so I will have to instead describe as best I can what happened. After T. loaded and activated the approach, FPL0 looked like this.
Approach GPS 13
RWY 13 (MA)
I had thoughtfully set the ceiling so he would be forced to fly the missed approach, holding at the Rochester VOR (RST). As usual, T. flew it perfectly, executing the missed approach and entering the hold at the Rochester VOR, using the SUSP feature of the Garmin 430 to bring up the holding waypoint, RST in this case.
What happened next caught both of us by surprise. I told him to anticipate the ILS-13 approach into Rochester and was planning on having him do the transition from the VOR to ELLIE.
While still in the hold at the Rochester VOR, T. decided to load the ILS-13/RST approach. So he loaded it, using ELLIE as the IAF, but did not activate it since he was still holding around RST. As soon as he did this, RST disappeared as the active waypoint. This left him in a hold without an active holding waypoint.
In discussing it later, he explained his logic was to simply load the ILS approach, the logic being that he would not activate it since he was still in the hold at RST. However, as soon as he loaded the ILS approach in the Garmin, all of the waypoints from the previous approach promptly disappeared. Since RST was not a waypoint in the loaded approach, T. was left without his holding waypoint. Had he chosen RST as the starting point when he loaded the approach, he would have still had RST in the set of FPL waypoints.
It was an unexpected scenario to both of us. The bottom line is that you should not replace an approach in the Garmin 430 if you are depending on a waypoint in the current approach for navigation. Unless you are very careful, doing so can cause you to suddenly be navigating to an unintended waypoint. I think this would be a case of being up the well known creek without a proper waypoint!