Corvettes steaming ahead: the yardstick of surface naval power was once the realm of destroyers and frigates, but this has been expanded in the post 9/11 world to include the addition of the corvette. At one time these were used only by small navies, but are now being seen even by major naval powers as multi-role platforms that are suitable for asymmetric/littoral operations.

But what is a corvette? A major problem defining warships is that designations often appear to be applied arbitrarily; at one time France's 6100-tonne Tourville and 5000-tonne Cassard classes were classified as corvettes; they are both destroyers although officially rated by the French Navy as fregates.

The corvette and the offshore patrol vessel have much in common, as they are usually sea-going vessels of between 55 and 100 metres in length with a displacement of 490 to 2500 tonnes, although there are exceptions. Both will be armed with a medium (57 to 76 mm) calibre gun and often with lighter (12.7 to 40 mm) weapons. A surface search radar is an essential tool and most will have the ability to carry, or to operate, a light-to-medium (four to ten-tonne) helicopter. Navies today call for an offshore patrol vessel but want a ship capable of using surface-to-surface and surface-to-air missile systems, possibly underwater warfare systems and sensors, with these sensors, weapons and communications integrated through a sophisticated combat management system. The ships that meet these general requirements are true corvettes.

Three decades ago smaller navies acquired fast attack craft, high-speed vessels with a maximum length of 55 metres, maximum displacement of 500 tons and armed with surface-to-surface missiles. But experience, notably in Operation 'Desert Storm' in 1991, cruelly demonstrated their vulnerability to stand-off attack due to their limited radar range (a function of short masts) and inadequate air defences and they were so compact that a single missile or bomb hit rendered them non-operational.

Many fast attack craft users are beginning to replace these ships with corvettes. The greater sophistication of the corvette is reflected in its unit cost of $300 to $400 million, but it provides a platform far more capable of protecting national interests at far greater distances. Indeed Swedish and German corvettes may well operate in the Middle East--a long way from the icy Baltic.

The corvette can conduct anti-surface and anti-submarine warfare operations as well as the wide range of missions ranging from 'operations-short-of-war' to 'showing the flag.' They can operate in more severe sea conditions than a fast attack craft, are better equipped in terms of sensors and communications to work with allied/coalition forces and they are big enough to absorb battle damage.

There are currently some 15 corvette programmes worldwide, as every major European yard is offering both corvette and offshore patrol vessel designs, sometimes in the same hull. Within Europe there are four corvette construction programmes underway in Germany, Poland, Russia and Sweden.

The German Braunschweig (K130) programme is typical of the modern corvette with a ship designed to have reduced radar, infrared and acoustic signatures through shaping the design to reduce reflective surfaces, the use of underwater exhaust systems and rafting machinery. Five 1662-tonne MTU diesel-powered K130s are being built by a consortium consisting of Blohm & Voss, Larssen and ThyssenNordseewerke. Each yard is producing modules and will assemble some of the 88.3-metre-long ships; Blohm & Voss is responsible for the superstructure as well as the first and fourth ships, Lurssen is producing the stern section module as well as the second and fifth ship while Nordseewerke will produce the bow sections and the third ship. Plans for a second batch of five have now been scrapped.

The ships will feature a Thales Nederland combat management system and an Eads TRS-3D air/surface search radar augmented by Thales Nederland Mirador electro-optical sensors. The surface-to-surface missiles will be Saab RBS-15s with a limited land-attack capability. One unusual feature is that these ships are designed to operate not only a helicopter but also two vertical take-off unmanned aerial vehicles.

Europe's other active corvette programme is Sweden's Visby class, being built by Karlskronavarvet. The fifth, and last, of these 72-metre-long ships with a displacement of 620 tonnes is scheduled for launching in November.

The Visby's are the 'stealthiest' ships under construction today, and their reduced signatures are achieved through careful design--even their Bofors 57 mm guns are stealthy. The Saab RBS 15 surface-to-surface missile launchers are within the superstructure, and an integrated mast includes the Ericsson Sea Giraffe AMB 3D search radar plus communications and electronic warfare antennas.

The Visbys have a Saab Systems 9LV Mk 3 Cetris combat management system, one that is also used for anti-submarine warfare through a CDC Canada Hydra sonar suite. Uniquely, the corvettes also have a mine countermeasures role with Saab Double Eagle unmanned underwater vehicles.

In 2005 the Russian Navy was scheduled to receive the first of ten Scorpion (Project 12.300) class corvettes designed by Almaz and built by the Vympal yard at Rybinsk. The 56.8-metre-long, 470-tonne displacement ships have a 'stealthy' hull which is compromised by three sensor positions; for Postiv Ml air/surface search radar, Garpun B fire control radar and Puma electro-optical director augmented by an A190 100m and Kashtan gun/missile mountings.

The Scorpions will replace the widely used (and exported) Tarantul (Project 1241.1) class and, like them, feature codag (combined diesel and gas turbine) propulsion. Vietnam plans to acquire up to ten Tarantuls, most of which will be built in country, and has reportedly acquired the gas turbines for them. However, the status of this programme remains unclear.

The much-delayed Polish Gawron (Project 621) corvette programme is about to begin again although the original plan for five ships, with an option on another five, appears to have been restricted to two hulls. Gawron is based on the highly versatile Blohm & Voss Meko 100 designs available in 69 to 80-metre versions of this highly modular concept that is available with a wide range of propulsion options.

The Polish version will be a 95.2-metre-long, 2035-tonne ship with codag propulsion. Most of the sensors and weapon systems will come from western or northern Europe, including RBS 15 surface-to-surface missiles, but she will also carry the Evolved SeaSparrow Missile (ESSM) surface-to-air missile system.

The Middle East market is also growing for corvettes and Iran is known to have recently produced a 1200 tonne corvette, the IS Mowj, but few details are available apart from the fact it is 88 metres long. The only active programme is the United Arab Emirates' Al Baynunah and work is already underway on the first of four 70-metre-long ships at CMN Cherbourg with the first ship to be delivered in 2008.

The remainder will be built by Abu Dhabi Shipbuilding, which will have an option on a further two hulls. The diesel-powered (MTU 12V 595TE 90) corvettes are based upon the French company's BR 67 design and will have a displacement of 630 tonnes.

They will feature a Selex Sistemi Integrati IPN-S combat management system, an Ericsson Sea Giraffe air/surface search radar augmented by a Terma Scanter 2001. The missile systems will be the MBDA Exocet MM 40 Block 3 surface-to-surface missiles and the ESSM, which will be supported by a Selex NA-25 weapon control radar. The 76 mm Oto Melara Super Rapid gun will be supported by a Sagem Vigy-Eoms electro-optical director.

Three corvette programmes are underway for the Asian market. In India steel is being cut for the first of four Project 28 corvettes that will be 90 metres long and have a displacement of 2000 tonnes. These ships will be built by Garden Reach Shipbuilders and Engineers and will primarily be anti-submarine platforms with some reports suggesting they will be improved Kora class ships.

Malaysia's ambitious Kedah 'New Generation Patrol Vessel' appears to be in very serious trouble. The concept was to use a 91.1-metre-long Meko 100 design with Atlas Elektronik Cosys combat management system, Eads TRS-3D air/surface search radar and an L-3 Brashear Lseos MK IIB electro-optical director. The ships have an Oto Melara 76 mm Super Rapid gun and will be capable of carrying both surface-to-surface and surface-to-air missiles later, but initially they would operate as offshore patrol vessels.

The first two ships, KD Kedah and Pahang, were built in Hamburg and delivered to Penang Shipbuilding and Construction Naval Dockyard (PSCND), who was to complete the outfitting and be responsible for integration trials. PSCND was also to build the next four ships with options on another 21.

Unfortunately, the system integration trials have been prolonged and the programme has encountered funding problems. Although modules for the next two ships, KD Parak and KD Terengganu, have been produced, western industrial observers are sceptical that the programme will develop much further and it may well be curtailed at four hulls.

Neighbouring Indonesia's programme is more successful. Two diesel-powered Sigma designs were ordered from Royal Schelde in January 2004 with delivery from 2008. At the recent Imdex Asia it was announced that Jakarta had taken up options on another two hulls. The Sigma (Ship Integrated Geometrical Modularity Approach) concept, first revealed at Imdex Asia 2003, calls for a range of ships of 52 to 98 metres and displacing 440 to 1930 tonnes. Usually with diesel engines and water jets, the mission options range from police to full littoral warfare.

The Indonesian Sigmas will be 90.5 metres long and have a displacement of 1650 tonnes. Much of the electronic fit will be from Thales Nederland, including the Tacticos combat management system, MW 08 surface search radar and Lirod Mk 2 electro-optical tracker. A hull-mounted sonar will be fitted but no con tract appears to have been awarded and the supplier of the navigation radar has also still to be announced.

The OtoMelara Super Rapid gun will be augmented by two Giat 20 mm weapons but the ships' 'punch' will be from MBDA Exocet MM 40 Block 2 missiles. The defence will include MBDA Mistral point defence missiles with two Tetral launchers. The ships' primary role will be coastal protection and their antisubmarine weapon suite will include two triple 324 mm torpedo tubes.

The Indonesians operate 19 corvettes; three Dutch-built Fatahillah class and 16 former East German Parchim Is (as Kapitan Patimura class), of which six are to receive new diesel engines to replace the Russian-built M504A. The Dutch Iv-Nesbru organisation is offering the Falcon, an 87.4-metre-long, 1700-tonne design based on the Fatahillah class corvettes.

The Latin American market for corvettes is developing, although the only active programme on the continent is in Brazil, where the Naval Arsenal is building the 2350-tonne Barroso, a 103.4-metre codog (GE LM 2500/MTU 20V 1163 TB83) ship. The ship is a development of the Inhauma class but has been beset by funding problems and even if completed on schedule in 2008 she is unlikely to have any sister ships.

She will have a domestically produced Siconta II combat management system, Selex RAN-20S surface search and RTN-30 weapon control radars as well as an Edo 997 hull-mounted sonar. The weapon fit will be Exocet MM 40, BAE Systems' Mk8 114-mm (4.5-inch) gun and a 40 mm Bofors Mk 3 together with two triple 324 mm torpedo tubes.

Greece has a corvette requirement and in 2003 Vosper Thornycroft (now the VT group) was selected to partner Elefsis in building these ships. Few details are available, apart from the fact that the ship will be about 100 metres long and the first of an initial two is expected to be delivered in 2009.

Across the Aegean the long-delayed $1.2 billion Mil Gem programme has recently been authorised in Ankara. This programme envisages seven general-purpose and anti-submarine ships being built in local yards with Aselsan and Havelsan providing the combat management system. The first-of-class is likely to be built at the Istanbul Naval Shipyard and it is reported the ships will be 95 metres long with a displacement of 1700 tonnes.

The Royal Navy is seeking a corvette-type ship to meet is future surface combatant requirements, but the Versatile Surface Combatant (VSC) is not required until 2023. This ship would be a multi-role vessel capable of ASuW, ASW and mine countermeasures roles. This would help permit a restructuring of the Royal Navy, which might see the total number of surface combatants rise up to 36 hulls (destroyers, frigates and VSC).

Spain has begun work on the Buque de Accion Maritima (Barn) offshore patrol vessels which reveal the difficulties which may be encountered in distinguishing between corvettes and offshore patrol vessels. They will have a displacement of 2600 tonnes and will be 95-metres-long with a 76 mm gun and two 25 mm guns as well as a helicopter up to nine tonnes. However, they will also have a combat management system of the Scomba family, which will make them, in theory, capable of carrying more advanced weapon systems. The first of four Barns will enter service in 2009.

The Netherlands is considering acquiring new vessels, primarily for policing roles. Up to four ships are being considered but it is unclear whether or not these will actually be corvettes.

In the Middle East there are at least three corvette requirements. Israel is seeking two ships to augment the four Eilat (Sa'ar 5) class ships, of which the latest is scheduled to be commissioned at the Northrop Grumman Ship Systems' Pascagoula yard during this year.

Kuwait has a requirement for what is officially described as a Fast Missile Strike Craft. Few details are available apart from the fact that it is to be between 57 and 70 metres long and is likely to be a corvette-type ship. Kuwait did begin an offshore missile vessel programme for up to three corvette types several years ago but the programme was abandoned due to funding problems. Unlike many of its oil-producing neighbours Kuwait does not have access to overland pipelines and must export its oil by sea and, for this reason, has a requirement for sea-going ships.

The Oman Project Khareef (Monsoon) programme is now down to a shortlist of three; Daewoo, Royal Schelde and the VT Group. Officially for offshore patrol ships this requirement looks at 100-metre vessels, however, industrial sources indicate that despite the name, the requirement is for two or three corvette-type ships and that a decision is anticipated by the time these lines are printed.

In Latin America Venezuela is ordering two or three large vessels that will certainly be corvettes and have been described as such by some official sources. They will have a displacement of some 1800 tonnes and will be 92 metres long and it is known that Caracas has begun negotiations with MBDA to acquire Exocet MM 40 Block 3 antiship/land-attack missiles.

Navantia will certainly provide these ships but a contract has still to be placed. It is unclear which design Navantia will supply but there are several contenders, including a 63-metre (formerly 58 metres) 'missile vessel'. The most likely candidates are the development of the 1542-tonne Descubierta OPV, which was first shown at Euronaval in 2004. This is an 88.8-metre-long diesel-powered design that can be extended into a full corvette, although the company also offer a 625-tonne Corvette 60 design.

A wide variety of designs are available and new ones are appearing every year. HDW revealed its 91-metre Hybrid Corvette in Hamburg last year and Lurssen is offering a radical design in the Advanced Lurssen Combat Craft with a displacement of 2800 to 3500 tonnes with all electric propulsion and an emergency system with a rudder in the forward compartment.

DCN revealed a new range of corvettes, the Gowind, at last year's Euronaval. These are sophisticated and well shaped diesel-engined or codag designs ranging from the Gowind 120, an 80-metre 1250-tonne ship to the Gowind 200, a 103-metre design with a displacement of 1950 tonnes.