Piloting the UK’s new Aircraft Carrier : Keith McLean

July 7th, 2015 by JCB
Posted in Articles, Technical and Training | No Comments »

 

HMS Queen Elizabeth, the first of UK’s two new aircraft carriers, was named by Her Majesty the Queen at Babcock’s Rosyth dockyard in Scotland on 4 July 2014, and manoeuvred out of the building dock to her fitting out berth on 17 July. She is the largest warship ever to be constructed in the UK.

 

There will be further high profile, high stress movements in the years to come, including the sea trials of HMS Queen Elizabeth in 2016, HMS Prince of Wales following approximately two years later, in terms of construction and delivery. The move from the building dock to the fitting out berth completed the first chapter of Forth Pilots’ involvement in the £6 billion aircraft carrier project.

The Queen Elizabeth class carriers will be 65,000 tonnes displacement on delivery, which places them in terms of size somewhere between the French carrier Charles de Gaulle (42,000 tonnes) and the US Nimitz class (100,000 tonnes). LOA = 285m, with a beam at the waterline of 39.6m and flight deck beam of 76m.

The contract to build the two carriers at Rosyth was signed in 2008, and the Forth Pilots became involved in the planning in 2009. In order to ensure continuity in the pilotage aspects of operations four pilots, from our district of 27 pilots, were assigned to the aircraft carrier project. All stakeholders in the movement and construction of the Queen Elizabeth class carriers have worked closely together on this highly unusual project – shipyard, transportation, tug masters and pilots. The ship simulator at South Tyneside College was heavily utilised to simulate and fine-tune the movement of the completed aircraft carriers and the arrival of the large block sections at Rosyth.

 

All aircraft carrier movements present challenges to pilots: there is no visibility of the ship’s side and a lack of a centre conning position. The Invincible class of aircraft carriers have been fairly regular visitors to the Forth over the past 30 years and as pilots we were well aware of the challenges they presented, but the new Queen Elizabeth class represents a considerable upward step. The vessels are being assembled in Rosyth from modules fabricated at shipyards throughout the UK. Final assembly is in a dock completed during World War One that required extensive improvements in preparation for the carrier programme. A large civil engineering project was necessary to extend the dock and widen the direct entrance to the enclosed basin.

After construction in the building dock there was only a clearance of 135mm between the bilge keel and the dock wall. Even a small angle on departure from the dock would have resulted in damage to the bilge keel. An additional problem was that the building dock does not have shore winches to control the position of the vessel, and stern movement, on exit.

After several simulation sessions and many meetings involving the shipyard and tug operators it was clear that leaving the dock presented many marine challenges. A controlled exit was proving difficult. Exiting the dock in a conventional manner represented an unacceptably high risk of damage. A solution had to be found. The solutions arrived at were imaginative and successful. To control the heading when exiting the dock a large pontoon was moored at the dock exit, in line with the dock wall and therefore effectively extending the length of the dock. The vessel could slide out of the dock and rest on the well-fendered pontoon, minimizing the possibility of bilge keel damage.

With the absence of shore winches, and in order to control the speed on exit, a 30 tonne bollard pull tug was lifted out of the water by the largest crane in Britain (see Pilot, June 2011) and placed in the dock ahead of Queen Elizabeth.

Strict wind criteria were agreed for the move, for simulations had shown that in winds exceeding 10/12 knots the carrier could not be held in line with the building dock. A total of nine tugs were utilised for the move from the building dock. Four of the tugs, with a combined bollard pull of 310 tonnes, were from the nearby BP crude oil terminal at Hound Point. Total bollard pull available for the move was in excess of 400 tonnes. To ensure there would be no problem with making tugs fast there were pre-rigged messengers secured to the ship’s side, which were numbered to ensure there would be no confusion. The fairleads were also numbered.

The main pilot conning position was under the forward end of the forward aircraft lift. A scaffold platform had to be built to give the pilot a view along the ship’s side, but this gave only a limited view of the bow area. Another pilot was therefore placed forward on the anchor observation platform. This was so that accurate visual information on the position of the bulbous bow was always available to the lead pilot.

A portable pilot unit (PPU) was essential to give accurate speed, rate of turn and lateral movement information. The system chosen was the Marimatech system with real time kinematic (RTK) capability, giving centimetre-accurate positioning.

Due to the complex nature of the operation, the number of tugs utilised, and the high level of communication required, the fourpilots involved in the operation were paired up, one pilot in each pair operating a PPU. Overall control remained with the lead pilot, who was under the forward aircraft lift, but if visibility became an issue a contingency was in place to hand over the lead to the pilot at the anchor observing platform. Additionally, there were dual communications, utilising one vhf channel for pilot/tug commands and a separate vhf channel for all of the other communications associated with the operation.

The critical part of the operation was over once Queen Elizabeth cleared the building dock. However, the swing in the basin was tight. The 285m carrier, with tugs at bow and stern, had to be turned dead ship in a 440m square, taking into account an exclusion zone around the nuclear submarines in one corner of the enclosed basin. The PPU again proved invaluable, allowing the turn to be monitored throughout and made in a controlled manner.

 

This high profile move was a complete success, and an example of what careful planning and pilots working together as a team with the shipyard and tug masters can achieve.

A time lapse video of the operation can be viewed here

Pilots assigned to the project were Jerry Purvis, Paul Wibberley, Fred Whitaker and Andy Blance. Article by Keith McLean

All images courtesy of BAE.