An HSL-1 from NATC at Patuxent River. This airframe does not or no longer wear a Ship number, but just the last three of its serial and ST for Service Test. Photo by: Howard Levy

'Armament tow attitude test' near the Bell factory. The rig could be tilted up to 45 degrees. Similar photos released in January 1955. The purpose, minesweeping, was not revealed. Ship 9 conducted airborne towing tests at Corpus Christi, Texas in February. The US Navy cancelled the HSL in July 1955. Of 233 serial numbers assigned, the last 180 airframes were cancelled. Two airframes between BuNo 129155 / 5 and 129161 did not apparently receive a Ship number; perhaps these were never made airworthy? Photo from: Bell

Ship 4, the first HSL-1 series aircraft. Construction number 4 according to helis.com, but we think it should be c/n 5. Photo from: Bell

Ship 5, the second Bell HSL-1 production aircraft, is seen 'hovering over Hicks Field, Fort Worth, with Bell pilots Joseph Dunne and William Quinlan at the controls, before 700-mile flight to Eglin Field, Florida, for extensive climatic tests.' Elsewhere we found this flight took place in January 1954. Note the dorsal fin, fitted to a couple of early airframes. Photo from: Bell

The last of 50 production HSL helicopters 'was kept at Bell until 1959, when it was used on a small Navy contract to test stability improvements.' Photo probably taken at Bell in Texas since an early Huey is seen. Dorsal fins had already been added to HSLs in 1953. 129877 is claimed to have become N74018, but that seems to have been a Bell 47. Photo from: San Diego Air & Space Museum

Another early shot of the first prototype Bell HSL, most probably during its maiden flight at Amon Carter Field. The only tandem rotor helicopter attempted by Bell, the HSL was almost too big for aircraft carrier elevators and high noise and vibration levels interfered with sonar work in the intended ASW role. A few airframes used in minesweeping trials. Photo from: Bell

Built to an urgent requirement for an anti-submarine warfare helicopter, the Bell 61, US Navy designation HSL, was a failure that never went into operational service although 53 airframes were completed. The photo shows the first prototype on its maiden flight, which took place at then Amon Carter Field. That site opened for passengers as the short-lived Greater Southwest International Airport one month later. Photo from: Bell