pprune fan#1 is right, here is a site that says the HUP-2 in the late 40's had a full asw autopilot! That is darn early, and just might qualify as the earliest "sas"
http://www.dvhaa.org/hup-2.html
"Early into production, an autopilot and dipping sonar were incorporated into the design, making the HUP the Navy's first Anti- Submarine Warfare helicopter. ASW technology was in it's infancy at the time, and in 1952 production shifted to non-ASW capable HUP-2's, or "Retrievers", as they were now nick named."
This site says it was a Sperry Autopilot, fitted to tame the tandem's very unstable characteristics:
http://www.helis.com/UpTo50s/h_h25.php