Sigma-class design

The Sigma-class is a Dutch-built family of modular naval vessels, of either corvette or frigate size.

Modular design
The basic design of the Sigma Patrol Series can vary as the hull segments are designed as components. Ships can vary in the number of hull segments and in the order in which they are placed. Sigma stands for Ship Integrated Geometrical Modularity Approach. The ship's main dimensions are named in the types itself, SIGMA 9113 stands for 91 m long and with a beam of 13 m. Likewise, the SIGMA 10513, is 105 m in length with a beam of 13 meters.

The design was derived from the earlier High Speed Displacement hull form by MARIN Teknikk AS in the 1970s.

Users

 * Indonesia (TNI-AL) has four SIGMA 9113 Diponegoro-class corvettes in active service from 2009. In August 2010, Indonesia signed a deal to build s based on the SIGMA 10514 in PT PAL Shipyard at Surabaya, Indonesia. A second contract was signed in February 2013. Eventually six ships will be built. The first ship, KRI Raden Eddy Martadinata (331), was commissioned on 7 April 2017 at Tanjung Priok. The second ship, KRI I Gusti Ngurah Rai (332), was launched in September 2016.
 * Morocco has ordered two 9813 class heavy corvettes (with VLS) and a light 10513 class frigate based on a modified design.

Under construction

 * Indonesia has ordered 2 Sigma 10514 class, these ships will be built by the Indonesian shipyard PT PAL with the first ship KRI 331 Raden Eddy Martadinata was laid down in January 2014 and as of January 2016 the first ship is almost complete. On 18 January 2016 the ship was launched and is scheduled to be delivered to the Indonesian Navy in January 2017. The second ship, KRI 332 I Gusti Ngurah Rai, is under construction by PT PAL and the modules for the ship arrived in Surabaya in January 2016.


 * Mexico has ordered 1 Sigma 10514 LRP based upon the Indonesian variant with different weapon systems and different role. The Mexican navy will use its sigma corvette as a long range patrol vessel. The keel was laid on 17 August 2017, the ship will enter service in 2020, launch is planned for 2018. The ship will be built in six modules with two amongst these modules built by Damen Schelde Naval Shipbuilding in Vlissingen, in the Netherands and remaining four by the shipyard of the Mexican Navy in Salina Cruz under supervision of Damen Schelde Naval Shipbuilding. The Sigma will replace the four Allende class (ex-USN ), and two Bravo class (ex-USN ) of frigates so, as many as six may be built.


 * Romania has ordered four Sigma light frigates for a total of 1.6 billion euro. All ships will be build at Damen Galati. Specifications on model and delivery were not published.

Potential operators

 * Poland Damen Schelde submitted its SIGMA PL 10514 in two variants for the competition to supply the Polish Navy with options for their Miecznik & Czapla programmes. Miecznik will be a coastal defense ship and Czapla a patrol ship.

Failed bids

 * Malaysia Damen Schelde participated in the competition to supply the Royal Malaysian Navy with six frigates under the Second Generation Patrol Vessel program. It lost to the French Gowind class. The other competitor was the MEKO A200.
 * Egypt Damen Schelde was in competition for four Sigma corvettes (+ two options) for the Egyptian Navy. The French Gowind-class corvette won this bid. The other competitor was TKMS MEKO A200.
 * Philippines Damen Schelde bought bidding documents but did not submit an offer.
 * United Arab Emirates Damen had submitted an offer (likely the Sigma 9813 or Sigma 9814) for the s. It lost to a corvette based on the Italian Comandanti class.
 * Oman had an interest in buying four SIGMA corvettes/frigates in March 2011. The Dutch queen Beatrix planned a state visit to Oman, one of the reasons for the visit was the sale of the ships to the Royal Navy of Oman.The official visit was cancelled due to the unrest in Oman at the time, she did go to an unofficial dinner with the Sultan of Oman. The official visit took place later in January 2012. During the first visit to Oman the Royal Netherlands Navy sent its air defence warfare frigate HNLMS De Ruyter (F804) to Muscat. In April 2012 it was announced that they lost to the Singaporean by ST Engineering. Damen had offered the Sigma 7513.

SIGMA 9113
The Indonesian variant is based on the Sigma 9113 design. Work on the first of the class, KRI Diponegoro, began with the first steel cutting conducted in October 2004. The ship was christened on 16 September 2006 and commissioned on 2 July 2007 by Admiral Slamet Soebijanto, Indonesian Navy Chief of Staff.

Options for two other units were exercised in January 2006 with the first steel cut commenced on 3 April 2006 in Damen's Schelde Naval Shipbuilding yard, Vlissingen-Oost yard and not in Surabaya stated earlier.

On 28 August 2007, Jane's Missiles and Rockets reported that Indonesia was having problems securing the export license for the MM-40 Exocet block II and are considering Chinese made C-802 anti-ship missiles as alternatives. However, the ships have already been delivered with the Exocet missiles.

SIGMA 10514
On the 16 August 2010, Indonesia Defense Department, signed a deal with PT PAL Indonesia and Damen Schelde to build a 105-meter frigate in Indonesia based on Damen Schelde Sigma 10514 design. For the first ship, five modules for the ship will be built in Indonesia and the Dutch manufacturer Damen Schelde will build 2 modules while for the second ship the Indonesians will build six modules and Damen Schelde will build one module. The first hull will only be equipped with guns (without major weapons) and the second hull is complete with major weapons such as 76 mm main cannon, 12 MICA vertical launch air defence missile, MM-40 Exocet block III, Torpedo, and SMART-S MK2 radar system. Though the Indonesian Navy announced that it will build two destroyer escorts referring to the SIGMA 10514. On the Indo Defence 2012 exposition a model was revealed showing the phalanx and ASW mortar replaced by a single 35 mm Oerlikon Millennium Gun system, also the 76 mm had a stealth cupola. Some reported that the VLS missiles will be Aster-15 instead of MICA, due to these changes the ships role also changed from ASW to AAW.

On 1 February 2013 it was announced that a second unit will be built by Damen Schelde Naval Shipbuilding and PT PAL Surabaya, the second contract includes torpedo tubes, combat control room and a couple of surface weapons. As of December 2015, the first ship, KRI Raden Eddy Martadinata (331), was 85% complete and the ship was launched on 18 January 2016.

Moroccan Navy variants
On 6 February 2008, Morocco signed a USD$1.2 billion contract with Schelde Naval Shipbuilding for two Light frigate SIGMA 9813 and one Light frigate SIGMA 10145 which are modified versions of the existing Sigma-class design.

A subsequent contract was signed on 1 April 2008 with Thales Nederland for the supply and installation of the command and control and sensor package for the ships. The package included TACTICOS combat management system, SMART-S Mk2 surveillance radar, LIROD Mk2 tracking radar, Thales KINGKLIP sonar system, IFF system, Integrated communication system comprising external communication system and FOCON internal communication system, two Target Designation Sights, VIGILE ESM system, SCORPION ECM system, and the integrated navigation system.

The first frigate for Morocco, Tarik ben Ziyad, was launched in July 2010, began sea trials on 6 May 2011 and was delivered on 12 September 2011. The second ship was launched on 2 February 2011, with sea trials planned for late in the year. The third ship was planned to be launched in September 2011.

Romanian Navy variant
In November 2016 the Romanian Navy indicated that Damen Shipyard's Sigma-class design had been selected to supply four vessels, to be locally constructed at the Damen Shipyard in Galati. Romania will order four multi-role corvettes for a total of 1.6 billion euro's including training, spare parts and ammunition. The first ship is planned to be delivered within 2.5 years after contract signing.

The Romanian Navy has studied the SIGMA 9813 and SIGMA 10514 with the 10514 meeting most of the requirements. No official confirmation has been given on what variant of SIGMA will be ordered.

Mexican Navy variant
On 18 August 2017, Damen announced the keel laying for one SIGMA 10514 Long Range Patrol (SIGMA 10514 LRP/ SIGMA 10514 POLA) at Damen Schelde Naval Shipyard in Vlissingen for the Mexican Navy. The vessel will be constructed modularly in six modules, two modules are to be constructed in Vlissingen and the other four modules in Mexico. According to a SEMAR computer generated depiction of the vessel, a Bofors 57 mm gun (Mk. 3 variant) may be used instead of the OTO Melara unit, and a Raytheon RIM-116 Rolling Airframe Missile or SeaRAM may be used instead of the Mica VLS. This missile unit was depicted in the image being aft of the main stacks above the helicopter hanger. No detailed information yet on what the anti-shipping system will be or what the embarked helicopter type will be.

Ships of class
Indonesian Navy / Sigma 9113 design

Indonesian Navy / Sigma 10514 design

Moroccan Navy / Sigma 9813 & 10513 design

Note: 613 now shows on AIS as Sultan Moulay Ismail.

Mexican Navy / Sigma 10514 LRP design

Sigma versions
There are three types of Sigma combatants
 * Sigma frigate
 * Sigma corvette
 * Sigma fast attack corvette

Simplified comparisons between the different Sigma models.

There are multiple new Sigma designs released in early 2015 of which little is known, these are the:

Sigma 8313 / Sigma 8011 / Sigma 7613 / Sigma 6610

They are likely to be part of the Compact SIGMA series, a new series small sized combatants with shorter range and up to 2 weeks mission endurance with the same combat systems as the larger Sigmas.