The Bendix K prototype in its second form, an unreal-looking egg shape. A print of this picture seems to be dated 27 November 1945. By January 1947 NX41817 was in its third form, with an open cockpit.

Bendix Helicopter was formed in 1943. The single-seat, coaxial Model K prototype, NX41817, first flew on 30 June 1945. NX41817 flew as a fully enclosed egg-shape apparently by November 1945 to aid the development of the bigger Model J. Although Bendix Helicopter based itself in Stratford, Connecticut, test-flying seems to have been done at Hadley Field in New Jersey.

The story of Hadley Field says the Bendix helicopters were tested there. The factory was at Stratford, Connecticut. Photo by Bendix Helicopter Inc. Photo from: Civil Aviation Historical Society, Melbourne, Australia