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Military


Visby korvetter

The Swedish Armed Forces' five Visby corvettes belong to the world's most modern ships in their class. The stealth technology that gives ships their characteristic appearance is developed to make it harder for the opponent to detect, whether the reconnaissance is using radar, infrared technology (heat radiation) or hydroacoustics (sound). Their tasks are surface combat, submarine hunting, escorting and demining. The ships belong to the Third and Fourth Naval Battalions.

Many of the ships' sensors are hidden in the hull when not in use. The weapon systems are also the ones hidden behind gaps. The exhaust gases from the vessel's water jet unit are diverted through hidden outlets near the waterline to provide as small a heat signature as possible. The Visby corvettes must be able to solve tasks in three dimensions, in the air, on the surface and under the surface. Their operational tasks are surface combat, submarine hunting, escorting and air defense. Possibility to land a helicopter on board is available on three of five corvettes.

The Visby Class corvette is the first vessel in the world to have fully developed stealth technology, combined with high operational versatility. The outstanding stealth properties fundamentally change the ship's survivability and improve its mission effectiveness. Visby is a flexible surface combatant, designed for a wide range of roles: anti-surface warfare (ASuW), anti-submarine warfare (ASW), mine countermeasures (MCM), patrol and much more.

About 1160 the Hanse seized the Swedish island of Gotland and developed Visby as a base and bastion for the Baltic trade. At its height in the fourteenth century the League bound fifty-two towns. It controlled the trade of northern Europe from Rouen to Novgorod. For a long time it monopolized the herring fisheries of the Baltic and the trade of the Continent with England. It established courts for the settlemen of disputes among is members, defended its members against law suits from without, and at times waged war as an independent power.

The Visby corvettes were built at Kockumsvarvet in Karlskrona between 2000 and 2009. Much of the technology was developed in Sweden, in a collaboration between FMV, Kockumsvarvet and the Royal Institute of Technology. The Visby Project was the largest surface vessel project ever conducted by Kockums. The project, which had been in progress for more than a decade, evolved steadily, attracting considerable attention for its stealth technology. The vessels are built in plastic laminate, a material that makes the ship very strong and resilient in relation to their weight. The material is one of the factors that gives the vessels very low signature levels, in terms of radar, magnetic and hydro-acoustic. This makes them difficult to detect on radar and infrared camera. At the same time the vessels can withstand shock effects very well and they can also take a big load.

In 1986 the Swedish Defence Material Administration (FMV) initiated the development of a stealth test platform, HMS Smyge. It was launched in 1991 and used for testing stealth characteristics in all possible aspects. This formed the basis for the YS 2000 project - the Visby Class corvette.

The corvettes are built in carbon fiber composite, a material that makes the ships very strong and resistant in relation to their weight. The material and construction technology were developed in Sweden, in a collaboration between FMV, Kockums and the Royal Institute of Technology. The engines drive water jet propulsion units, also called water jets, which despite their size make the ship quiet and easy to maneuver.

Signatures and signals have been minimized, partly to increase the effect of own sensors and antidotes to avoid being hit and to make it difficult or prevent detection and identification, both in the air and in water. Hull and hull material have been optimized and equipment, weapons and sensors have been specially designed or placed behind hatches. Low hydroacoustic signature has been achieved through silent water jet propulsion units, low-speed machinery and generator sets that are double-elastic arranged under noise-reducing hoods.

The magnetic signature has been minimized by choosing hull material and non-magnetic equipment as far as possible. Visibility in standard cameras and thermal cameras has been minimized through the choice of hull material and color, hidden exhaust and ventilation emissions, water spray and masking. Through passive sensors, directional transmission and tactical adaptation, revealing signals have been minimized.

At the very beginning it was thought that there would be 10 ships – two versions with different specialties. Circumstances resulted in five ships with all functions - plans for an anti-air warfare capability fell victim to financial restrictions. The corvettes are some of the "stealthiest" ever developed but they are extremely costly [possibly $200 million each] and of the six ordered between 1995 and 1999 only five were completed. Kockums built the five Visby corvettes and delivered them to the customer, FMV (the Swedish Defence Matériel Administration), which conducted a program of trials and tests.

In 2002, FMV conducted the first real tests with Visby. The first two vessels, Helsingborg and Härnösand, handed over FMV to the Armed Forces in 2009. Until 2013, three more vessels, Visby, Nyköping and Karlstad, were handed over. By then, FMV had delivered all the corvettes in the Visby class. HMS Helsingborg and HMS Härnösand were then upgraded to the latest version, version 5, with final delivery of HMS Härnösand in early 2015.

There is some mystery as to when some of the units were commissioned. They had been operated by the procurement agency, Forsvarets Materielverk (FMV), which had conducted extensive testing and trials and continued to do so until the corvettes joined the fleet between 2012 and 2014.

Five years behind schedule, the first of the Visby class corvettes to be commissioned was HSwMS Helsingborg, in April 2006, closely followed by three sister ships with HSwMS Karlstad scheduled to join them two years later. The fifth of series, HMS Karlstad, remained under construction in 2008. HMS Helsingborg and HMS Härnösand were the first two corvettes in the Visby series delivered to the Swedish Armed Forces to be included in the organization and ready for missions. FMV handed over the two ships to the Armed Forces at a ceremony in Karlskrona on 16 December 2009. The two ships which were equipped with over-water and underwater sensors and were in this version (version four) able to be operational in a number of national and international tasks.

With these the ships reached their initial operational capability (the so-called Version Four) and they entered a "Special Period" which addressed signature, sensor as well as weapon integration and safety issues. This would bring the ships to full operational (Version Five) status. When the first Visby corvettes were delivered in version five in 2012, there were trained crews available. In 2012 FMV delivered two corvettes of Visby class to the Swedish Armed Forces. This meant that there were two Visby corvettes which can hunt submarines with torpedoes, depth charges and sonar. They can both deploy and clear mines, and fire anti-ship missiles. They also have an airport function for takeoff and landing helicopters. The ships have been supplemented by including mine clearance systems, helicopter landing capability, anti-surface ship missile and additional stealth adaption. Two were delivered in the second half of 2013, followed by the last in 2014.

In January 2020, HMS Härnösand launched from Örlogshamnen in Karlskrona for the last time in the Third Naval Battle Squadron's organization. She goes to Stockholm and her colleagues on the Fourth Naval Battle Squadron where she is exchanged for HMS Visby. In the past, when the fleet's ship numbers were larger, ship changes between flotillas were common, while nowadays it is relatively uncommon.

The reason for the change is that we now get all three Visby corvettes with helicopter decks on the Third Naval Battle Flotilla. The proximity to the helicopter squadron in Kallinge makes joint exercises much easier down here in the south, says Per Edling who is commander of the Third Naval Battle Squadron. Shipmaster Gustav Reimfelt and crew have worked for some time to make the change of ship as smooth as possible: "HMS Härnösand has had Karlskrona as its home port since it was launched just over 15 years ago, 2004. Now we wish our colleagues good luck. Härnösand is a good ship in the excellent ship class that the Visby corvettes constitute. We are now looking forward to taking over HMS Visby".

The five corvettes have been tested in both the Mediterranean and Arctic environments in northern Norway. But the corvettes are adapted to Swedish conditions and that is where they are best. When they perform together with international partners in various exercises, they add an ability that is lacking in them.

After 2020 some new weapons will replace old ones. Some examples are a new naval target robot with a longer range, a new submarine hunting torpedo and hopefully an air defense robot. At the same time, a mid-term modification was approaching. In the deteriorating world situation, the navy's ships have worked hard with exercises, operations and not least the constant maritime surveillance. With few ships and many tasks, the equipment wears out and it begins to be felt.






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Page last modified: 30-06-2021 12:04:42 ZULU