Replenishment at Sea (RAS)
Replenishment at Sea (RAS) involves warships and auxiliaries sailing in very close proximity, sometimes only around 30 meters apart, while connected by a tensioned steel wire rope called a jackstay. The jackstay is then used to support fuel/water hoses or a traveller block to pass solid stores from one ship to another.
Replenishment at Sea (RAS) was initially carried out using a system of ropes and pulley blocks from the stern of the supply ship to the bow of the receiving ship. At this time only stores and bags of coal were passed to the receiving ship.
Later techniques developed for the transfer of fuel oil pumped over to the receiving ship through flexible bronze hoses.
Not until the Second World War did the replenishment at sea became well established. At this time rubber hoses started to be used, which after gaining experience led to the abeam method of fuel replenishment and the heavy jackstay method of transferring stores.
Replenishment at sea is now a routine operation, carried out by the Royal Fleet Auxiliary (RFA) around the world.
Why do we conduct Replenishments at Sea?
The warships of the Royal Navy must remain at sea for long periods of time while not relying on friendly ports to re-supply them with food, fuel, ammunition or stores. Instead Royal Navy ships rely on Replenishment at Sea by the tanker and stores ships of the Royal Fleet Auxiliary (RFA) and other Allied auxiliaries far from friendly ports.
The Two Sides of a RAS
Replenishment at Sea systems consist of specialist Delivery and Receiving equipment.
The Receiving equipment is normally fairly compact and is installed on all of the ships (Royal Navy and Royal Fleet Auxiliary), sometimes the RFA need to be replenished! The Receiving equipment normally consists of a fixed pad-eye, stump mast, or a movable high point which provides a connection point for the Delivery ships jackstay.
The Delivery equipment required for a RAS is normally only installed on the auxiliary ships as the equipment requires a large amount of deck space for the drives, winches, and associated pulleys and metalwork.
Replenishment at Sea Liquid (RAS(L))
RAS(L) is the replenishment of bulk fluids such as Dieso (Marine Diesel), AVCAT (Aviation Fuel), Lub Oil, and Fresh Water.
The main methods used in RAS(L) depend on the size of ship, and sea state which are Large Derrick, Jackstay, Crane Rig and Hudson Reel.
Replenishment at Sea Stores (RAS(S))
The S in RAS(S) stands for “Stores” which are transferred by either Heavy or Light jackstay.
What happens during a Replenishment At Sea (RAS)
...replenishment at sea (RAS)is now a routine but complex procedure involving precise ship handling....
A replenishment at sea (RAS) is now a routine but complex procedure involving precise ship handling, as the two (or even three) ships will be within 30 yards of each other. In a typical RAS the supply ship will come to the planned course and speed (normally about 12-13knots), and then the receiving ship will take station astern. When the supply ship is ready, she will signal the receiving ship who will then increase speed and move to the alongside position.
This is more difficult than it sounds as the receiving ship will have to make minor course changes of one or two degrees, and also minor speed adjustments in 1/10 of a knot increments to maintain the exact station keeping position.
When the captain is happy with the ship’s station keeping the RAS can commence. Unlike filling your car, you can’t simply reach over and connect the fuel nozzle and start pumping. The first thing that happens is a projectile with a “gun-line” attached will be fired across between ships (normally from the receiving ship). Once the line is in hand on the other side, it will be tied to a heavier line, which will then be attached to a heavier one (called a heavy messenger) to be pulled across first by hand and then by a winch, to the receiving ship.
A steel cable called a heavy jackstay will come over connected to the heavy messenger, which is then attached to the receiving ship and brought up under tension by an auto tensioning winch (ATW) on the supply ship. The jackstay wire will normally sit at about a 45-degree angle from the supply ship, so the fuel hose can be lowered down the jackstay to the receiving ship using runner winches. Only after the hose is connected can refuelling begin.
Stores, food, and ammunition can be transferred in a similar way, with a traveller block moving back and forth between ships on inhaul and outhaul cables.