Dynon added an HSI function to their EFIS systems a few months ago. I would really like to have an HSI, as they provide a much more intuitive display than the CDI that I currently have. But, the Dynon HSI is only capable of displaying GPS information from the Garmin GNS 430, not VOR or ILS information.

Two days ago Dynon stated on their forum that they are working on a solution to allow the HSI to display VOR and ILS information from the GNS 430. Yeah!! Assuming their new implementation works properly, I will almost certainly eventually replace the CDI with a second Dynon D-10A. The lower D-10A will normally be used as an HSI, but it would also provide a backup attitude display, in case the upper D-10A fails. In that case, I would use the CDI display on the GNS 430 for navigation.

This picture shows the HSI in VOR mode.

Here it is in GPS mode.