When first delivered to the Coast Guard Air Station at Floyd Bennett Field, New York, in late-1943, the two-seat HNS was intended to serve only in the training role, which it did admirably by serving as the platform for the successful instruction of 102 men in rotary wing flight during World War II. However, events would place the Sikorsky design at the forefront of the effort to demonstrate the value of the helicopter. Between 1943 and 1945, the HNS demonstrated the capabilities of using a hoist for air-sea rescue. It also performed naval aviation's first helicopter missions of mercy, on one occasion delivering blood plasma to aid survivors of an explosion aboard the Navy destroyer Turner (DD 648) in January 1945. The following year, Coast Guardsman Lieutenant August Kleisch rescued eleven Canadian airmen stranded after their aircraft crashed in the snowy landscape of northern Labrador. In both instances weather conditions prevented all aircraft but the helicopter from performing the missions.

The HNS also served as the platform for evaluating shipboard operation of helicopters, with Coast Guard HNSs logging 98 landings on a platform mounted on the deck of the transport James Parker in 1943. In early 1944, Lieutenant (junior grade) Stewart R. Graham deployed with an HNS on board the British freighter Daghestan for a sixteen-day voyage across the Atlantic to Great Britain. During the cruise, Graham successfully operated the helicopter in 40-knot winds, foreshadowing the regular employment of rotary-wing aircraft aboard ship for antisubmarine warfare.

The HNS-l will forever grace the history of military aviation as the Navy's first helicopter, the first designed specifically for military use, and the first United States rotary-wing aircraft to be mass-produced.