Like flying into Auburn Muni S50 and I just can't find any info on what the purpose of RNAV(GPS)-A is.

the purpose is to get an IFR pilot down to minimums while avoiding obstacles/mountains and if possible (depending on the weather) land at S50.

The -A  (no specific runway) means its can be for any runway as it is a circling approach.

Short enough?

 

 

It’s a non-precision approach designed to be flown with an IFR-certified GPS system. In a GA aircraft it could be done using something like a Garmin GNS-430/530 or the newer Garmin GTN 650/750.

The waypoints that make up the approach, CIDUG, ORTIN, JISTA and CAXAM will be contained the the GPS navigation database. Each waypoint corresponds to a specific latitude/longitude, which the GPS can navigate to.

The GPS will provide headings to fly to each named waypoint is sequence, beginning with CIDUG. The pilot’s responsibility is to insure that aircraft remains at the altitude shown on the profile view. No lower than 3000 feet at CIDUG, no lower than 2,100 feet at JISTA etc. The lowest altitude you can descend to is 920 feet after passing CAXAM. If you don’t see the airport visually by the time you arrive at the last waypoint UGUYE, you would have to fly a missed approach.

These kinds of approaches are very common. Dozens of new RNAV/GPS approaches come out every month. They permit instrument approaches to smaller airports that have no ground-based navaids like ILS, VOR or NDB.

Reality XP and F1 make very accurate Garmin GPS add ons with real world navigation databases that can be easily added to almost any FSX or P3D aircraft. These simulated Garmin GPS units can be used to fly these approaches in the sim just as you would in a real aircraft.

The FSX/P3D GPS can fly these approaches too - but the default navigation database it uses is so old, that most newer RNAV approaches won’t be found.

Almost any FMS-equipped airliner add-on with a current database can fly these kind of approaches as well.