Barrow has a long and proud history of building submarines for the Royal Navy. The first of a new class of seven, nuclear powered, hunter-killer submarines, HMS Astute, emerged from BAE Systems’ Devonshire Dock Hall and onto the ship lift in 2007. After over two years at the fitting out berth she sailed for Faslane and acceptance trials in November 2009.  HMS Ambush followed in September 2012

Planning for the Astute “exit” (never referred to as departure or sailing) was well under way when I arrived in Barrow (ex-Humber, ex-Liverpool) in 2003. It is difficult to grasp, let alone describe, the vastness of the whole project and all the issues involved. I should also explain that my role here in Barrow is that of Assistant Harbour Master as well as Pilot, so that there was involvement in a wide range of preparations including a huge dredging programme. PEC tripping on various dredgers and the inevitable delays to normal commercial trade caused by restrictions on the use of dock/lock gates to satisfy the nuclear safety case stretched our marine and pilotage resources to the limit. There were countless other tasks.

Vessel Information

The submarines are 98m (LOA) x 17m beam at the aft hydroplanes which are always submerged and, being very important bits of kit, are marked for the dock passage by flags on poles. The submarine is conned from on top of the “fin” since visibility is restricted from the normal Control, Room navigation position. Thermal underwear is therefore an absolute requirement!

My first involvement with Astute as a pilot was to attend the simulator at the MARIN Institute in Holland in early 2007. This was a simple set of exercises, using minimum personnel, just to prove that the Barrow Channel was adequate to deal with the vessel. It also introduced us to the Dutch “designed” pilotage/tug strategy for the exit from Ramsden Dock Basin and the Channel passage, using four Voith tugs. The many subsequent visits to MARIN, for both Astute and Ambush were always attended by a full RN navigation crew, tug skippers, BAE Systems staff and two pilots. My understudy for both ships was Mark Bray, a former Barrow Pilot now at Southampton.

Pilots were also involved at the launch of each boat, using local work boats to shift them from the ship lift to the fitting-out berth, and from the fitting-out berth to the basin dive hole (c.20m deep) in Devonshire Dock for trim/dive trials.

The Dock Transit (Draught 9.3m)

A critical moment as the AMBUSH transits from the old Buccleuch Dock passage into the Ramsden Dock. Graham is the red spot on top of the conning tower or “fin”.          Photo: ABP

With Astute (Boat 1) the larger (Svitzer) Voith tugs planned for use in the exit from Ramsden Basin and the Channel passage, were also used in the dock – but solely as a rehearsal for making fast and letting go in the Channel. The tie-up for these is quite complicated, with each tug having four lines up to the submarine, all of which have to be capable of being released in the correct sequence.  Since the channel configuration does not permit tugs to be permanently secured to the submarine, for the first dock transit each tug had to make fast three times and let go twice, and none was involved at the critical points. As a result of lessons learnt from Astute this procedure was not repeated for the Ambush (Boat 2) exit.  Also for Ambush, two of the larger tugs were used purely to stand by in case of emergency.

The Channel Transit (Draught 10.3m)

The sea channel is 8 miles long with a width of 90m at the inner and increasing to 140m at the outer end. The minimum required tide height is 8.5m; and subsequent tides must be rising; and weather criteria must be satisfied. A definitive graph (about 180 pages of it) covers all possibilities of tide and wind, and a Met Office man is on site for a week before sailing. Wave effect (pitch and heave) is a major consideration in the Outer Channel.

There is normally a planned delay of about 24 hours between arriving in Ramsden Basin and sailing to allow for various tasks, such as final storing and trim adjustments for the sea passage.  However, owing to adverse weather forecasts, Ambush had to do it all in one day. This was a huge achievement by the shipyard staff.

The south side of the Basin and the dock entrance (36m wide) are lined with neatly tessellating fenders, a job that can only be completed when the outer gate is opened at about an hour before High Water (HW).  Only then, and after a diving inspection to check that the gate (a “flap” gate which lowers to lie flush on the bottom) is locked in position, can the submarine proceed to sea at around 40 minutes before HW

This manoeuvre, and the tug disposition, was designed by Pieta Kluytenaar, a Dutch ship-handling consultant, in conjunction with MARIN. Essentially four Voith tugs are strapped alongside, two each side between the hydroplanes (a very tight fit). Then the whole job is moved ahead using the port side tugs to slide along the fendering. The after tugs are used to give headway and the forward boats for stopping/sternway.

Once clear of the entrance the submarine’s own power can be engaged but since she needs about three knots for steerage way, the initial turn to port (2 kts) is controlled by the stern tugs “pushing on” to steer since the forward tugs are effectively on the pivot point. The forward tugs are let go after the first turn is completed and the speed is increased to about four knots. The two remaining tugs are let go  at about 1.5 miles from the dock entrance, once everyone is happy that all is well! The speed is then increased to eight knots for the remainder of the channel passage with all the tugs remaining in close escort. The Commanding Officer takes control once the tugs are let go.

For Astute departure, Svitzer supplied the four Voith tugs. These came from various ports round the country and a fortnight’s bad weather resulted in some late changes. This made life difficult since the tugs had to be fitted with temporary fendering (diving job) to protect the submarine’s sonar arrays.  A further problem with the Astute was encountered when letting the stern tugs go in the Channel which resulted in the last ropes from both tugs having to be cut since an unwanted sheer had been imparted to the submarine, which caused some anxious moments!

This problem was rectified for Ambush, but the tug provider was changed to Serco as Svitzer could no longer guarantee to support the project. This switch also resulted in a change in tug types since regrettably, excellent as they are, nobody is building new Voith tugs and those that remain are ageing. As a consequence, “the plan” was modified to use two AFDs forward and two ASDs aft. The Serco tugs are also now permanently fendered for use on these submarines, which is saving  a lot of bother.

Boat No.3, HMS Artful, is programmed to launch in 2013 and sail in 2014, by which time I shall have retired. I wish my successor all the luck and satisfaction that I have enjoyed when his turn comes round.