SAS, I think the origination started with Siegfried Hoffman, a test pilot at MBB. By 1982 at the Hanover airshow, world aerobatic ( helicopters ) champion Hauptman Karl Zimmerman* was doing the most impressive and choreographed aerobatic displays in the BO-105. Had the pleasure of watching him daily, and then giving he, his spouse and children a ride in our UH-60A, chaperoned by Sergei Sikorsky. Siegfried Hoffman was also there,with his new BK-117 ( with SAS, no less ) and was invited to trade rides with him. ( having done a flight evaluation of the BO-105 in the days prior to the UTTAS fly-off, the BK was certainly a step forward, not to take anything away from the maneuver capability of the 105 in the right hands ).
*Karl told us that back in his anti-tank helicopter unit he practiced the aerobatics daily, and his show certainly reflected that resulting excellence.