The Sigma-class is a modular warship design originating from Damen Schelde Naval Shipbuilding of the Netherlands and is intended primarily for export sale. The class is currently in inventory with the Indonesian Navy, the Mexican Navy, and the Royal Moroccan Navy. Eighteen of the type were originally planned with ten having been completed and one being cancelled (Vietnamese Navy). Building began in 2005 and the first vessels were commissioned in 2007.
Indonesia vessels are KRI Diponegoro (365), KRI Sultan Hasanuddin (366), KRI Sultan Iskandar Muda (367), and KRI Frans Kaisiepo (368). Mexico operates ARM Reformador (101). Morocco has access to RMNS Tarik Ben Ziyad (613), RMNS Sultan Moulay Ismail (614), and RMNS Allal Ben Abdellah (615). All are in active service as of this writing (2019).
At the heart of the Sigma-class design is a modular approach - the vessel can be built to suit the needs of a particular customer and the end-product can cover such types as fast-attack corvette, standard ocean-going corvette, off-shore patrol vessel, or basic frigate fighting forms. Inherent stealth features include an enclosed, low-profile smoke funnel, enclosed/integrated main mast, and slab-sided hull superstructure.
A turreted deck gun is set over the forecastle in the "A" position. Aft of this is a stepped hull superstructure which runs up to the integrated bridge section which hosts the integrated main mast mounting various communications and sensor fits. Beyond this is a collection of Surface-to-Air Missile (SAM) launchers and, aft of these installations, is the low-profile smoke funnel arrangement over midships. The aft section of the superstructure can accommodate a full-service helicopter hangar to go along with the stern-based helicopter pad (servicing a single navalized helicopter aircraft).
Structural dimensions include a running length of 297.6 feet, a beam of 42.8 feet and a draught of 11.9 feet. Displacement reaches 1,700 tons depending on overall configuration. The ships can serve a crew of up to 80 personnel.
Sonar is mounted in the bow, giving the warship an advantage against enemy submarines. Other installed systems include the Thales Group TACTICOS, MW08 3D surveillance / search radar, Sperry Marine BridgeMasterE ARPA radar, and LIROD Mk.2 tracking fire control radar. An ESM (Thales DR3000), ECM (Racal Scorpion 2L), and decoy (TERMA SKWS, DLT-12T) suite are all part of the ship's makeup.
Armament includes the 76mm OTO-Melara turreted deck gun, 2 x 20mm Denel GI-2 (GIAT M693/F2) autocannons, 2 x MBDA Mistral TETRAL surface-to-air quad missile launchers, 4 x MBDA Exocet MM.40 Block II anti-ship missiles and 2 x Triple torpedo tubes supporting the EuroTorp 3A 244S Model II/MU-90 torpedo families.
Installed armament is made up of 2 x SEMT-Pielstick 20PA6B STC engines with 4 x Caterpillar 3406C TA generators driving 2 x Rolls-Royce propellers at the stern. Maximum speed in ideal conditions reaches 28 knots though cruising is generally at 18 knots. Range is out to 5,500 miles.