4/2009:
There are several GPSS systems available as of this time. The STEC ST-901 and the Icarus SAM are the most popular retrofit GPSS systems for GA. If the customer has an STEC autopilot, we recommend going with the STEC ST-901 system which is about $2400.00 installed. If the customer has a non-STEC autopilot we recommend the Icarus SAM GPSS system which is about $3200.00 installed.
I had a chance to spend some time flying with the various GPSS product over the last few years. GPSS truly brings "heavy iron" autopilot features to the GA aircraft at a reasonable cost. GPSS has got to be one of the best avionics values today. With all existing autopilots the pilot must manipulate the heading bug or course pointer to intercept and track a nav course. The process must be repeated at each waypoint change. GPSS automates this entire process. Pilots with nav-track only systems (i.e. STEC 20,30,40,50) will enjoy nav capture benefits with the installation of a GPSS computer.
With the GPSS installed the pilot simply presses the GPSS button then sits back and watches the magic. It does not matter what the heading of the aircraft is, or the bearing to the waypoint. It doesn't matter where the heading bug or course pointer is placed. Once the GPSS is engaged the aircraft will enter a standard rate turn toward the waypoint in the GPS. The GPSS will calculate the wind correction and track to the waypoint. If a flight plan is entered into the GPS, the autopilot will fly the flight plan waypoint sequence. If you have a WAAS GPSS such as the Garmin GNS-480, 530W, or 430W, the GPSS will fly the holding patters and curved approaches.
FOR IMMEDIATE RELEASE
July 28, 1999
S-TEC Offers Affordable Roll Steering With GPSS by S-TEC
S-TEC Corporation of Mineral Wells, Texas announced today that for the first time in the General Aviation aftermarket, aircraft owners will have affordable, integrated navigation and flight-control capabilities at their disposal with the introduction of
GPSS. GPSS or GPS Steering by S-TEC flies the 429 digital composite roll steering commands output by many of the newer GPS navigators. Most autopilots typically track a course using heading data and course deviation, which is shown as CDI or HSI needle deflection.
The GPS unit knows its position and, based on a flight plan programmed by the pilot, knows where it is going as well. GPS systems equipped with 429 digital composite roll steering can output right and left steering commands. GPSS can interpret these commands and fly multiple waypoint courses and complex steering maneuvers defined by these waypoints, automatically.
GPSS reduces pilot workload since the pilot will no longer have to set the course arrow or heading bug at leg changes. However, most pilots will make these changes to maintain situational awareness.
Right now, some GPS systems output composite roll steering commands for enroute navigation, and a few GPS overlays of DME Arc approach transitions are currently available. In the future, databases should be expanded to include full procedure approaches, transitions to approaches, procedure turns, published holding patterns, and missed approach maneuvering.