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 Bendix Model K prototype initially flew with an uncovered fuselage and later with a fully enclosed, egg-shaped fuselage. By January 1947 it was in this form, with an open cockpit. Oddly the Model K and the larger Model J were apparently both named Whirlaway. Bendix Helicopter closed its doors in 1949. NX41817 then went to NACA for rotor research work according to a NASA document. An end date for this is not known to us. Photo from: NASA Langley