The hull design was based on that of the RRS Discovery and the Hecla class were built to commercial standards costing £1.25 million each. They carried two small survey craft, a launch, a Land Rover and a Wasp helicopter, for which there was a flight deck and hangar. They were chiefly funded from the Polaris Submarine Ballistic Nuclear Missile programme, with their major task to carry out regular oceanographic observations essential for the Polaris submarines to hide in thermal layers.
Besides the strengthened hull for work in ice and the provision of air conditioning necessary for work in all climates, they had modifications particular for a scientific vessel: wet and dry laboratories; a survey chartroom and photographic darkroom; oceanographic winches for deep seawater analysis and coring; stabilisers and a bow thruster, which enabled the ship to maintain her position when stopped for scientific observations.All 4 Royal Navy vessels were fitted with an Inertial Navigation System for mid-Ocean positioning. 'Drift' was corrected by taking satellite fixes from the Transit Doppler Sat Nav. Each vessel, due to their requirement to operate mid-Ocean, was equipped with a sick bay with a 2-bed ward and an operating theatre with X-Ray machine. Every vessel carried a Surgeon-Lieutenant and Leading Medical Assistant.In the 80's and 90's, 'Hecla' and 'Hecate' were equipped to make Gravity Free Air Anomaly observations over the mid-Atlantic ridge for the US Department of Defence 'Nav Star' GPS constellation of satellites.
| Name | Pennant No. | Builder | Laid down | Launched | Commissioned | Status | |
|---|---|---|---|---|---|---|---|
| A133 | Blythswood Shipbuilding, Scotstoun | 6 May 1964 | 21 December 1964 | 9 September 1965 | Sold to private interests and renamed SV Bligh, 1997 | ||
| A137 | Yarrow Shipbuilders, Scotstoun | 26 October 1964 | 31 March 1965 | 20 October 1965 | Broken up at Pipavav, 1994 | ||
| A144 | 14 May 1964 | 14 July 1965 | 4 May 1966 | Sold to Indonesian Navy in 1986 and renamed KRI Dewa Kembar | |||
| A138 | Robb Caledon, Leith | 9 November 1972 | 4 October 1973 | 22 November 1974 | Sold to private interests and renamed SV Somerville, 2001 Broken up at Alang, 2004 | ||
| SAS Protea | A324 | Yarrow Shipbuilders, Scotstoun | 20 July 1970 | 14 July 1971 | 23 May 1972 | Active in service | |
The first three ships,, and, were ordered in the early 1960s to replace the aging survey ships and .
A fourth ship, was ordered in the early 1970s. Apart from HMS Hecate, they all saw service as hospital ships in the Falklands War, while Herald and Hecla also served in the Gulf War and the former as a temporary Antarctic Patrol Ship in 1991 and 1992. Hecate saw service as the temporary Antarctic Patrol Ship in 1982 after being painted grey and fitted with AA guns in Gibraltar. Hecate was the first Royal Navy vessel to visit South America following the Falklands conflict. During the conflict, Hecla, commanded by Captain Geoffrey Hope RN, with Lt. Cdr. Ward as XO, ferried Argentinian prisoners of war to Montevideo. Being the first vessel of the conflict to be in the glare of the world media, she gained a high public profile out of proportion to her ambulance ship role. Hydra was also outfitted as an ambulance ship whereas Herald was equipped as a casualty reception station on a par with SS Uganda.
A fifth Hecla-class vessel, SAS Protea (A324) was ordered by the South African Navy and commissioned on 23 May 1972. As of 2017, Protea remains in service.[1]
Hydra was sold to Indonesia Navy in 1986 and renamed KRI Dewa Kembar-932. As of 2017, Dewa Kembar remains in service.
Hecate decommissioned in 1990 and was broken up, while Herald was finally decommissioned in 2001, and was replaced the same year by .
Hecla was paid off in 1997 and sold to an Irish private company, renamed MV Blythe, to be replaced by . In 1969, commanded by Captain David Haslam (who retired after 10 years as Hydrographer in 1985), she landed a party who hoisted the Union Flag on Rockall, which significantly extended the UK's territory.
The first three ships in the class were named for the three paddle-wheel Hydra-class sloops, two of which (and) were fitted out as survey ships from around 1860.