Tide-class tanker

The Tide-class tanker is a class of four fast fleet tankers that entered service with the British Royal Fleet Auxiliary from 2017. The 37,000 t ships provide fuel, food, fresh water, ammunition and other supplies to Royal Navy vessels around the world. Norway ordered a similar 26,000 t version with a 48-bed hospital and greater solid stores capacity, but reduced liquid capacity; it was delivered in November 2018 as HNoMS Maud two years after originally planned. The two classes are very similar but are not directly comparable due to large variance in capabilities delivered.

The two variants are both based on the AEGIR design from Britain's BMT Defence Services but were built by Daewoo Shipbuilding & Marine Engineering (DSME) in South Korea with final outfitting in the UK and Norway respectively. Britain ordered four ships in February 2012, originally at a cost of £452m for the building of the hulls however, the final cost was £550m. The Royal Norwegian Navy ordered HNoMS Maud in June 2013 for NOK1,320m (~£140m).

On 22 February 2012 an order for four tankers was placed with Daewoo Shipbuilding & Marine Engineering (now Hanwha Ocean) at a contract cost of £452m, plus an additional £150m to be spent in Britain, making a total cost for the four ships slightly over £600 million net, not gross. Building ships in South Korea caused controversy in Britain, but no British yards tendered for the order because it was made clear to them that no UK yards would be welcomed or successful, way before the contract was given away. On 14 November 2012 it was announced that the new class would revive names from the Cold War Tide-class oilers - Tidespring (A136), Tiderace (A137), Tidesurge (A138), and the new name Tideforce (A139). The previous Tidespring earned a battle honour in 1982 for her service during the Falklands War, which included transporting a company of Royal Marines to recapture South Georgia. The board carrying the honour and the ship's badge were both taken to Korea for installation in the new Tidespring.

The Tide class are a 200.9 m (659 ft 1 in), 39,000 t derivative of BMT Defence Services' AEGIR-26 design, whose origins lie in a civilian tanker from Skipskonsulent of Norway. They are double-hulled to reduce or prevent oil being lost by damage to the outer hull, in line with the MARPOL regulations for civilian tankers (from which military tankers are partially exempt). As well as being safer, this means that Tides can go to places that discouraged their single-hulled predecessors - the recently decommissioned Rover-class vessels and Leaf-class tankers.

There are three stations for replenishment at sea (RAS) abeam, of diesel oil, aviation fuel and fresh water. There is also a rig for astern replenishment. The flight deck and helicopter hangar allow for replenishment by air - "vertical RAS". The flight deck is large and strong enough for a Chinook helicopter to land on. Propulsion uses medium-speed diesel engines driving twin shafts in a hybrid combined diesel-electric or diesel (CODELOD) arrangement designed for fuel efficiency across a wide range of speeds.

All four ships can be armed with two 30 mm cannons and two Phalanx CIWS. The 30 mm cannons are fitted aft, directed starboard, and port. One of the CIWS mounts is located forward, and the other aft. Only when a vessel is on a high-risk deployment are Phalanx CIWS and 30 mm fixtures likely to be fitted. This policy is common among RFA vessels and follows that when a ship is deployed to more dangerous theatres, such as east of Suez, heavy dedicated armament is warranted. When in home waters and carrying out more superficial tasks such as FOST, there is little need for the vessels to be equipped with heavy armaments. For instance, as of June 2021, RFA Tidespring has currently been fitted with her fore and aft Phalanx CIWS fixtures and both 30 mm cannons whilst deployed worldwide with CSG21.

BMT offer the AEGIR fleet tanker in three sizes. The AEGIR-10, AEGIR-18 and AEGIR-26 are 18,000 DWT and 26,000 DWT respectively, and can carry 8,000 m³ (2,100,000 US gal), 16,000 m³ (4,200,000 US gal) and 24,000 m³ (6,300,000 US gal) of fuel. The AEGIR-18R replenishment ship trades a third of its fuel capacity for 1,350 m³ (48,000 cu ft) of dry stores in an extended superstructure. The standard AEGIR-18 has less range (10,000 nautical miles, 19,000 km, 12,000 mi) and is slower (18 knots, 33 km/h, 21 mph) than the British version.

The design has been entered in a number of competitions, but as of March 2016^[update] the only foreign order has been for an AEGIR-18R derivative from the Royal Norwegian Navy in 2013 (see below). The AEGIR-18A, a derivative of the AEGIR-18R like the Norwegian ship but with among other things better air-conditioning, was offered to Australia for Project SEA 1654 Phase 3, a requirement for two supply ships to replace HMAS Success and HMAS Sirius. In June 2014 it was shortlisted along with the Buque de Aprovisionamiento en Combate, which would be built in Spain by Navantia, who have built most of Australia's recent warships. In March 2016 Australia announced it would be buying the Spanish ship. In March 2016 DSME also lost out to Hyundai Heavy Industries in a competition to supply New Zealand with a tanker. A 2014 DSME presentation points out that India, Singapore and Brazil all need new supply ships in the near future.