SKJOLD Class Fast Attack Craft [FAC] Part I

The six SKJOLD Class FAC were built by Kvaerner/Umoe Mandal incorporating the SENIT 2000 combat management system as a joint development of DCNS (now Naval Group) and Kongsberg.

A view of Skjold, Gnist, Storm and Skudd operating together whilst on exercise in the Kristiansund at the end of January 2014. Skjold acted as the pre-production trials ship for the class design between 1999 and 2003, undertaking a lengthy deployment to the United States. She had only recently returned to operational fleet when this image was taken.

Kongsberg‘s new generation Naval Strike Missile [NSM] has been selected to equip the NANSEN and SKJOLD Class vessels of the RNoN as an anti-ship and land-attack missile. Future operators include Poland, Malaysia, the US and Germany.

With the re-delivery of the HNoMS Skjold on 29 April 2013, the Norwegian Navy finally has all six of its Skjold class fast attack craft in service. The Royal Norwegian Navy (RNN) has a long history of operating fast patrol boats, going back as far as 1873 when the steam-powered, Thornycroft-built Rap was commissioned into the fleet, placing the RNN in the forefront of fast patrol boat operators. Ever since then, fast patrol boats have been an integral element in Norway’s defence structure and the RNN has kept on refining the design of these vessels over time. However, they have never previously adopted a design as radical in so many ways as these latest ships.

The prototype Skjold class vessel has now been rebuilt to the standards of the production series. Most notably, she has acquired the revised COGAG propulsion system of two Pratt & Whitney ST18M and two Pratt & Whitney STM40 gas turbines fitted in the series-built vessels in replacement for her original CODOG propulsion system. A full outfit of weapons and sensors has also been installed. Re-commissioned in the Spring of 2013, this view shows her participating in the NATO Cold Response 2014 training exercise.

GENESIS: EVOLUTION OF THE SKJOLD CLASS

The origins of the Skjold programme date back to the mid-1980s, when the Norwegian Defence Research Establishment (NDRE) began to study a replacement for the Storm and, ultimately, the Hauk class fast attack craft, which were, respectively, commissioned into the fleet between 1965 and 1967 and between 1977 and 1980. The emerging programme for the new units, which ultimately came to be known as Project SMP 6081, required them to be survivable, stable weapons platforms capable of operating at speeds of 45 knots in Sea State 3, to have a range of at least 800 nautical miles at 40 knots, and to be able to operate outside coastal waters in a variety of scenarios, including NATO operations. In addition, the project office undertook a wide range of studies designed to reduce the vessels’ radar cross-section (RCS) and infrared (IR) signatures.

The Norwegian Navy Material Command (NAVMATCOM), together with Commander Sea Training (COMSEATRAIN), ran several analyses to balance the operational requirements with the likely available budget. For the platform system, no fewer than ten different platforms concepts were initially taken into consideration. Having examined this wide range of replacement options, the study was subsequently narrowed down to a shortlist of three concepts, viz. a conventional mono-hull, a catamaran-hull and an air-cushion catamaran/surface effect ship (ACC/SES).

The studies carried out by NAVMATCOM indicated that shock levels experienced by the SES were only one-third of that of a mono-hull.3 Similarly, the maximum displacement of structural members when subjected to shock was around half that of a comparable mono-hull. These advantages were a direct result of the SES’s elevated position in the water and its low draught. In spite of this, there was some hesitation in adopting the new hull form and a SES passenger vessel was even hired to uncover operational limitations of an SES when compared with the mono-hulled Storm and Hauk classes. Additional confidence was provided through experience gained designing and constructing the Oksøy and Alta class minehunters and minesweepers, which demonstrated the stability and large deck area inherent in the SES-catamaran hull form. Ultimately, the combination of improved resistance to shock and survivability, superior sea-keeping, greater internal volume and high speed-to-power ratio that the ACC/SES provided proved decisive in its selection.

By 1994 all staff requirements were defined and, in July 1995, a Request for Proposals [RfP] was issued. Three yards ultimately submitted bids: the Norwegian shipyards Umoe Mandal and Mjellem & Karlsen and Lürssen Werft in Germany. On 30 August 1996 Umoe Mandal was awarded a c. US$36m equivalent contract to build a pre-production unit, to be named Skjold. Following approval of construction specifications by NAVMATCOM, construction commenced in 1997. The prototype vessel was launched on 22 September 1998 and turned over to the Royal Norwegian Navy on 17 April 1999. At this stage weapons, sensors and combat management systems were not installed and 46 tons of sand ballast was subsequently provided to simulate their wight.

The pre-series vessel underwent comprehensive testing with focus on speed, sea-keeping, EMI/EMC, signatures and functionality, as well as the operational reliability tests – mainly in northern Norway during autumn and winter. There was also a year-long deployment to North America on loan to the US Navy. This initial trials programme had an important bearing on whether to proceed with the series production order and was to result in several changes to the production specification.

In spite of emerging doubts about the value of the programme in the post-Cold War naval environment, a new defence white paper approved by the Norwegian parliament in June 2001 envisaged the construction of five additional units. This decision was subsequently confirmed in October 2003 once terms and pricing for the programme had been provisionally agreed. Subsequently, on 28 November that year, the Material Investment Branch of Norway’s Defence Logistics Organisation (NDLO) awarded the Skjold Prime Consortium (SPC) a NOK3.7bn (c.US$550m) contract to build and equip the five new ships, whilst upgrading the prototype to the same standard. The SPC was an industrial alliance that brought together three partner companies to share responsibility for the delivery of the Skjold platform. It comprised Umoe Mandal (responsible for detailed design, systems integration, construction, testing and integrated logistic support); the Armaris joint venture between France’s DCN and Thales, now merged into DCNS (combat system design authority); and Kongsberg Defence & Aerospace (responsible for delivering and integrating the combat system in cooperation with Armaris). Umoe Mandal’s share of the programme consisted of about NOK2bn; Armaris received approximately NOK1bn; whilst Kongsberg Defence & Aerospace’s (KDA’s) share was valued at NOK750m. The construction of the first of the five standard production units, Storm, began in October 2005

In spite of further challenges to the class’s value and a number of project delays, commissioning of the new ships in operational configuration commenced in September 2010, with the re-delivery of the upgraded Skjold in April 2013 completing the programme. All units will achieve full operational capability by early 2015. It is the RNN’s plan to have four units available at any time, while two undergo maintenance and further upgrades.

DESIGN DETAILS: STRUCTURE AND STEALTH

The most distinctive feature of the Skjold class design is undoubtedly its innovative twin ACC hull form. The 47.5m long, catamaran SES-hull is made of a fibre reinforced plastic (FRP) sandwich construction, which reduces the overall weight of the ship. This material is capable of absorbing high levels of impact and, as such, minimising the extent of damage to the ship’s structure, as well as the cost of repairs. FRP also gives the ship so much buoyancy in itself that it can hardly sink. Moreover, its use enables most types of damage – from a surface scratch in the laminate through to major damage to a panel and its underlying structure – to be repaired quickly by using specially developed techniques. Another noteworthy feature is the provision of under-deck heating to prevent build-up of ice on the deck. Umoe Mandal was licensed to use the Seemann Composites Resin Infusion Moulding Process (SCRIMP) technique in constructing the class. This consists of a resin transfer moulding process that uses a vacuum to pull liquid resin into a dry lay-up. It is used for making very high quality, repeatable composite parts with almost zero VOC (volatile organic compound) emissions.

Stealth was a major preoccupation within the project office since the programme’s inception. The class has been designed to minimise all observable signatures. Controlled shaping of the ship above the waterline is evident in the absence of 90º corners and the inclination of the hull and superstructure at a small angle in order to deflect radar. The super-structure exhibits low and sleek characteristics, topside equipment is arranged to maximise concealment and there is extensive use of anechoic coatings. The air intakes to the gas turbines and lift fans are covered with a radar-absorbing mesh, the windows on the bridge incorporate a radar-absorbing material and all hatches are flush in order to reduce their RCS signatures. A similar consideration mandated the stealthy cupola provided for the Oto Melara 76mm/62 gun. The 9.6m-high main mast is constructed entirely from carbon fibre and the material is also used in beam flanges and frames.

Infra-red (IR) signature is kept to a minimum by the use of seawater cooling for the gas turbine exhausts; the water outlets are ducted into the air cushion between the two hulls and through the stern of the vessel. Similarly, the acoustic signature is decreased thanks to the fibre-reinforced plastic materials, which provide better structure-borne noise damping qualities. In addition, the water-jet propulsion generates lower hydro-acoustic signatures. The material composition in the wetted area of the twin hulls has been modified in order to produce a ‘smoother’ finish thus reducing hydrodynamic friction.

Operating in the littoral environment of fjords and archipelagos has also helped the Nordic navies become leaders in the application of present-day visual stealth and protective colourings. The Skjolds feature a camouflage scheme which is the result of the thorough study and testing of the hues and tones found in the Norwegian topography; scientists actually travelled around various areas and measured the colourings at different times of the year. The resulting paint scheme, which also incorporates high infra-red absorption properties, greatly reduces the ships’ electro-optical and visual signatures. As such, the Skjolds are hard to detect when lurking close to the coastline and are able to engage hostile forces from close range while remaining undetected. Another important asset is the class’s capability to access very shallow waters denied to other vessels. With about 75 per cent of their displacement being ‘carried on air’, a shallow draught of as little as 0.9m allows the ships to operate safely in shallow coastal waters whilst still maintaining excellent sea-keeping qualities.

A detailed view of Skudd’s bridge structure. A MASS decoy launcher is pictured in front of the bridge’s face, with the Saab CEROS-200 radar and optronic fire-control director mounted on the bridge roof. The carbon-fibre mast supports the Thales MRR-3D-NG multi-role radar on the lower platform, with a navigation radar above. The top of the mast houses the Sagem VIGY-20 electro-optical fire-control system with a pole for the ES-3701 ESM antenna immediately behind

PLATFORM MANAGEMENT SYSTEMS

The ships have been equipped with an advanced L-3 MAPPS integrated platform management system (IMPS) featuring multi-functional consoles with high-resolution colour monitors that display ergonomically designed graphical pages of the ship’s machinery and systems. This highly automated system incorporates an integrated bridge system (IBS) supplied by Kongsberg; a digital gas turbine control system; an integrated battle damage-control system (IBDCS); an equipment monitoring system (inclusive of a vibration monitoring capability); and a digital CCTV system. The overall system’s modular design, which combines widely distributed but intelligent and interconnected electronics, enables the crew to control, monitor and operate all platform machinery, electrical and emergency systems from several shipboard locations

The cockpit-style bridge, featuring a Kongsberg Maritime IBS, provides the pilot and navigator with full control over the bridge display consoles. It incorporates a K-Bridge autopilot, a voyage data recorder, a Kongsberg Seatex AIS 100 automatic identification system, an AGI electromagnetic log, a meteorological station, a Sagem 40 inertial navigation system, a Sperry Marine NAVIGAT 2100/SR 2100 fibre-optic gyro compass, a Trimble Navstar GPS/PPS receiver, JRC NAVTEX, a Skipper GDS 101 echo sounder and a Brudeseth optical bearing device. The bridge consoles display chart data from an Electronic Chart Display & Information System (ECDIS), radar and electro-optical (EO) data, as well as weapons system functionality.

Damage control is an important issue, with fire a principal concern. The RNN learned a lot of lessons from a catastrophic fire on board the Oksøy class minehunter Orkla in November 2002 and many of these have been incorporated into the Skjold class design. The ship is divided into six gas- and water-tight sections and features two engine rooms, one in each hull. The ship can continue to operate with one engine room out of action. Both are encapsulated with fire-retardant insulation material and incorporate Halotron and Hi-Fog water-mist fire-extinguishing systems. There is both a primary and secondary damage control station, both of which can access the IBDCS embodied in the L-3 MAPPS IPMS. This provides an instant overview of all aspects of the ship’s status and provides the opportunity to react in a very tight timeframe.