The Bell Company’s HSL was one of the world’s first helicopters developed specifically for the antisubmarine role. Although the Germans employed helicopters from ships to search for submarines during World War II, it was an ad hoc effort using available aircraft, as were the few subsequent U.S. and British navy trials in this field.
Bell won the Navy competition to develop a helicopter specifically for antisubmarine warfare (ASW) in June 1950. The HSL was produced in relatively large numbers for its time—three XHSL-1 prototypes and 50 HSL-1 production helicopters, completed from 1953 to 1956. The U.S. Navy had ordered more, and the Royal Navy had contracted for 18, but problems with the helicopter in the ASW role led to U.S. cutbacks and cancellation of the British order.
The HSL was a tandem-rotor helicopter designed to carry dipping sonar and to attack submerged submarines with acoustic homing torpedoes and surfaced submarines with the AUM-N-2 Petrel missile (actually a modified Mk 21 aerial torpedo). With a gross weight of 26,500 pounds, it was the largest helicopter ordered in quantity up to that time, requiring a 1,900-horsepower engine.