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Areplenishment oiler orreplenishment tanker is a navalauxiliary ship withfuel tanks and drycargo holds which can supply both fuel and dry stores duringunderway replenishment (UNREP) at sea. Many countries have used replenishment oilers.
TheUnited States Navy's hull classification symbol for this type of ship was 'AOR' (Auxiliary Oil Replenishment). Replenishment oilers are slower and carry fewer dry stores than the US Navy's modernfast combat support ships, which carry the classification 'AOE'. In 2020 the US Navy began to develop a new type of ship, the 'AOL' orlight replenishment oiler; construction of the first is planned for 2026.[1]
The development of the "oiler" paralleled the change from coal- to oil-fired boilers in warships. Prior to the adoption of oil fired machinery, navies could extend the range of their ships either by maintainingcoaling stations or for warships to raft together withcolliers and for coal to be manhandled aboard. Though arguments related to fuel security were made against such a change, the ease with which liquid fuel could be transferred led in part to its adoption by navies worldwide.
One of the first generation of "blue-water" navy oiler support vessels was the British RFAKharki, active 1911 in the run-up to theFirst World War. Such vessels heralded the transition from coal to oil as the fuel ofwarships and removed the need to rely on, and operate within range of coaling stations. During theSecond World War, the United States Navy's dramatically enlarged fleets, especially those in thePacific Theater, required massive quantities of black oil,diesel oil,avgas, and other fuels and lubricants to support American land, sea, and air operations against remote, widely dispersed Japanese forces. Those supply demands resulted in U.S. Navy personnel refining many established practices for oilers and creating new procedures for replenishing warships whileunderway and for transporting highly combustible materials with increased effectiveness through hostile waters and over vast ocean distances.[2][3]
Modern examples of thefast combat support ship include the large British Fort class, displacing 31,066long tons (31,565 t) and measuring 669 feet (204 m) in length and the United States'Supply-classUSNS Arctic, which displaces 48,800 long tons (49,600 t) and has anoverall length of 754 feet (230 m).
For all but the largest navies, replenishment oilers are typically one of the largest ships in the fleet. Such ships are designed to carry large amounts of fuel and dry stores for the support of naval operations far away from port. Replenishment oilers are also equipped with more extensive medical and dental facilities than smaller ships can provide.
Such ships are equipped with multiple refueling gantries to refuel and resupply multiple ships at a time. The process of refueling and supplying ships at sea is calledunderway replenishment. Furthermore, such ships often are designed with helicopter decks and hangars. This allows the operation of rotary-wing aircraft, which allows the resupply of ships by helicopter. This process is calledvertical replenishment. These ships, when operating in concert with surface groups, can act as an aviation maintenance platform where helicopters receive more extensive maintenance than can be provided by the smaller hangars of the escorting ships.
Their size, additional facilities, and ability to support the operation of other vessels, means that replenishment oilers have been used ascommand ships, with some ships, such as the FrenchDurance class, this capability being built into the vessels from the start.
Because the replenishment oiler is not a combat unit, but rather a support vessel, such ships are often lightly armed, usually with self-defense systems (such as thePhalanx CIWS close-in weapons systems), small arms, machine guns and/or light automatic cannons. They may also carryman-portable air-defense systems for additional air defense capability.
Argentine Navy operatesARAPatagonia
Royal Australian Navy operates twoSupply-class replenishment oilers.
Brazilian Navy operatesAlmirante Gastão Motta
Royal Canadian Navy operatesMV Asterix.
Chilean Navy operatesAlmirante Montt andAraucano
People's Liberation Army Navy operates twoFuyu-class fast combat support ships, fourDayun-class general stores issue ships, nineFuchi-class replenishment ships, and a singleFusu-class replenishment ship.
Republic of China Navy operatesROCS Wu Yi andROCSPanshih
Colombian National Navy operates twoLüneburg-class replenishment ships, purchased from Germany.
Egyptian Navy operates a singleLüneburg-class replenishment ship, purchased from Germany (being supplemented or replaced by twoFort Rosalie-class replenishment ships, purchased from the United Kingdom).
French Navy operates oneJacques Chevallier-class and twoDurance-class tankers
German Navy operates sixElbe-class replenishment ships, twoRhön-class tankers, and threeBerlin-class replenishment ships.
Hellenic Navy operates a singleEtna-class replenishment oiler and twoLüneburg-class replenishment ships, purchased from Germany.
Indian Navy operates twoDeepak-class fleet tankers, oneAditya-class auxiliary ship, and a singleKomandarm Fedko-class oiler.
Indonesian Navy operates a singleRover-class tanker purchased from the United Kingdom, twoTarakan-class tankers and more on order.
Italian Navy operates oneVulcano-class logistic support ship, a singleEtna-class replenishment oiler and twoStromboli-class replenishment oilers.
Islamic Republic of Iran Navy operates twoBandar Abbas-class replenishment ships.
Japan Maritime Self-Defense Force operates threeTowada-class replenishment ships and twoMashū-class replenishment ships.
Republic of Korea Navy operates threeCheonji-class fast combat support ships, andROKS Soyang
Royal Netherlands Navy operatesHNLMS Karel Doorman
Royal New Zealand Navy operatesHMNZS Aotearoa
Royal Norwegian Navy operatesHNoMS Maud
Pakistan Navy operatesPNSNasr andPNS Moawin
Peruvian Navy operatesBAPTacna
Polish Navy operatesORP Bałtyk
Russian Navy operates threeBoris Chilikin-class fleet oilers, oneDora-class tanker, twoUda-class tankers, oneIman-class tanker, fourAltay-class tankers, threeDubna-class tankers, twoKaliningradneft-class tankers, and a singleProject 23130 replenishment oiler.
Royal Saudi Navy operates twoDurance-class tankers.
South African Navy operatesSAS Drakensberg
Spanish Navy operatesPatiño andCantabria.
Royal Thai Navy operatesHTMS Similan
Turkish Navy operates twoAkar-class replenishment oilers and oneDerya class.
BritishRoyal Fleet Auxiliary operates oneFort Victoria-class replenishment oiler, fourTide-class tankers and twoWave-class tankers (maintained in reserve).
United States Military Sealift Command operates twoJohn Lewis-class replenishment oilers, fifteenHenry J. Kaiser-class replenishment oilers, fourteenLewis and Clark-class dry cargo ships, and twoSupply-class fast combat support ships.
National Navy of Uruguay operates a singleLüneburg-class replenishment ship purchased from Germany
Bolivarian Navy of Venezuela operatesRBNV Ciudad Bolívar
Vietnam People's Navy operates the replenishment oilerHQ-905
Philippine Navy decommissionedBRP Lake Caliraya in 2020.
Portuguese Navy decommissionedNRP Bérrio in 2020. Two new replenishment oilers were ordered in 2024.[4]
Ukrainian Navy decommissioned its onlyBoris Chilikin-class fleet oiler in 2001.
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In theUnited States Navy, anOiler is a Combat Logistics ship that replenishes other ships with fuel and in some cases food, mail, ammunition and other necessities while at sea, in a process calledUnderway Replenishment or UNREP.[5] Up through theSecond World War Navy oilers used commercial tanker hulls, with the addition of UNREP gear, defensive guns, and military electronic and damage-control equipment; since the 1950s however they have been built from the keel up as specialized naval auxiliaries. They were previously classified asFleet Oilers[6] in the 20th century; under the currentMSC operation their full classification is listed asFleet Replenishment Oilers.[7] Since the 1960s the classificationTransport Oiler (AOT) has applied to tankers which ship petroleum products to depots around the world, but do not engage in UNREP.
The first fleet oilers[8] were identified by the hull designation AO, which is still in use.[7] Large, fast multifunction oilers which also provide ammunition and dry stores are identified asFast Combat Support Ships (AOE),[9] and mid-size ones Replenishment Oilers (AOR). The AOR designation is no longer in use. All of these oilers provide the combined services of the AO, AE, AFS and AK.
The style "USNS" and prefix "T" identify a ship as being operated by a civilian crew under theMilitary Sealift Command (known as theMilitary Sea Transportation Service until 1970).
There are three classes of vessels currently in commissioned service:
Both theHenry J. Kaiser andSupply classes will be replaced by theJohn Lewis-class ships.
