Just watched a great FAA WINGS seminar on flying approaches with the Garmin GNS430/GNS530. It is part of a series by Mike Jesch and Brian Schiff, which I highly recommend.
There was a short discussion about why the navigator doesn’t sequence past the missed approach point, and I wanted to give the real answer. It is not up to Garmin engineers to make this decision. It is specified in the RTCA DO-229D document which is called out by FAA TSO-C145. This standard was developed by a committee consisting of people from aviation regulators, avionics manufacturers, and industry groups from around the world. In fact, almost all of the navigation related behaviors of the G430/530 are specified in that document.
Here are the relevant sections from DO-229D which indicates that it must be a manual process and that FROM guidance must be given:
The FROM guidance is important when crossing the MAP since it means correct left/right guidance is still shown when landing instead of showing a turn to a MAP that isn’t aligned with the runway, which could lead to pilot confusion.
So don’t forget to press OBS to un-suspend when executing a missed approach, but thank the RTCA committee for ensuring navigators give useful guidance when crossing the MAP and continuing to land. This standard also makes it easier to transition between aircraft with different navigators since they are all based on the same standard, even though the “knobology” might be a little different.