the sikorsky s-58 (ff 8 mar 1954) entered usn service late 1955 as the hss-1. this looked a good bet for the uk admiralty, which had been searching for a machine with sufficient power and endurance to be able to complete all three phases of anti-submarine warfare; hunt for, find and then destroy submarines. westland obtained a licence to build the s-58 in 1956. one s-58 was bought and modified with a 1100shp napier gazelle turbine engine, which ff 17 may 1957. 2 pre-production airframes built, ff 20 jun 1958 which became the wessex has.1.
the has.3 (a 1600shp gazelle mk 165 engine) and hu.5 (twin couled gnome turbine engines) were improved has.1s for the rn.
westland also produced the mk.31 for the ran (27), the mk.52 for iraq (12), mk.53 for ghana (2), the mk.54 for brunei (2) and the mk.60 as a civilian version of the raf hc.2 for bristow helicopters to serve offshore platforms in the north sea.