The XHSL-1 was an antisubmarine warfare (ASW) aircraft operated by the U.S. Navy. The aircraft was twice as big as any helicopter that Bell had created to date at the time, and it was Bell's first tandem design. 52 were flown and demonstrated use as a mine-sweeper.

Source: 2019 VTOL History Calendar, VFS; The Forgotten Bell HSL, Tommy H. Thomason