Replenishment oiler

A replenishment oiler at work

A replenishment oiler is a naval auxiliary ship with fuel tanks and dry stores capability, which can replenish other ships underway. The US Navy hull classification symbol for this type of ship is AOR. Classes include the Wichita-class ships of the US Navy, the Soviet/Russian Boris Chilikin type, and the Canadian Protecteur class. They are slower and carry fewer dry stores than Fast Combat Support Ship (AOE) ships.

The US Wichita class of AORs comprises seven ships: USS Wichita (AOR-1), USS Milwaukee (AOR-2), USS Kansas City (AOR-3), USS Savannah (AOR-4), USS Wabash (AOR-5), USS Kalamazoo (AOR-6), and USS Roanoke (AOR-7). The class ship (first ship in the class), USS Wichita, was commissioned in 1966. The last of this class, the USS Roanoke, was commissioned in 1976. These ships are typically named after smaller US cities. All ships of this class have been retired from service, and are being held by MARAD in the inactive ("mothball") fleet (National Defense Reserve Fleet, a.k.a. NDRF).

The forerunner of this design was a Kriegsmarine (German Navy) ship, the Dithmarschen, which was built in 1938. The Dithmarschen was designed to provide fuel and stores (including munitions) in a "One Stop Shopping At Sea" context to the German fleet. After the war she was claimed by the United States as a war prize and commissioned into the United States Navy as the USS Cohecuh (AOR-110). She proved the feasibility of this sort of vessel in supporting task forces at sea. She was decommissioned in 1956. The Wichita class was one variant on this concept later developed by the U.S. Navy, the other variant being the larger and faster AOE class of fleet replenishment oiler.

The modern US AOR-1 class of ships was designed primarily to support anti-submarine task forces. These ships gross just under 40,000 tons, have a length of 651 feet (198 m), a beam of 96 feet (29 m), and a draft of about 35 feet (10.7 m) fully loaded. They are powered by three Foster-Wheeler D-type steam generators operating at 600 PSI, driving two engines with a combined power output of 33,000 SHP (shaft horsepower), giving them a maximum sustained speed of about 22 knots. They are equipped with twin rudders. They are equipped with highly automated fuel and cargo handling systems, and are capable of underway replenishment (UNREP in navy terminology) from both port and starboard sides simultaneously, and also can transfer stores and munitions by helicopter (vertical replenishment or VERTREP). The US Navy will as a matter of policy neither confirm nor deny that these ships are equipped for the storage and transfer of nuclear weapons.

Navies other than the U.S. Navy are actively designing and building fleet replenishment oilers of the AOR class. These navies, including the Royal Australian Navy and the Spanish Navy, have requirements that do not include high speed and high capacity; thus an AOR design meets the logistics needs of these navies better than would a larger, faster AOE design.