Anti-Submarine Warfare Shallow Water Craft

In December 2013, the Defence Acquisition Council (DAC) –- the main acquisition panel subordinate to India's Ministry of Defence (MoD), approved the procurement of sixteen anti-submarine warfare (ASW) vessels capable of operating in shallow waters, at a cost of ₹13,440 crore, to replace the ageing Abhay-class corvettes of the Indian Navy – which were commissioned between 1989 and 1991.[13][14]

In June 2014, the MoD issued a tender, worth USD2.25 billion under the 'Buy and Make India' category to private-shipyards – including Larsen & Toubro (L&T), ABG Shipyard, Pipavav Defense and Offshore Engineering (R-Naval), Goa Shipyard (GSL) and Garden Reach Shipbuilders & Engineers (GRSE), for the procurement of the 16 anti-submarine vessels.[15]

In October 2017, Cochin Shipyard (CSL) and Garden Reach Shipbuilders & Engineers (GRSE) emerged as the first and the second-lowest bidder in the tender, respectively.[16]

On 29 April 2019, the MoD and GRSE signed a contract valued at ₹6,311 crore (US$790 million) for eight anti-submarine vessels, to be delivered between 2022 and 2026.[17] The contract stipulated that the first vessel had to be delivered within 42 months of the date of signing, with the remaining seven vessels delivered at regular intervals.[18][19]

On 30 April 2019, the MoD and CSL signed a similar contract, valued at ₹6,311 crore (US$790 million) for the construction of the remaining eight vessels – within a deadline of 84 months.[20] Under this contract, the first ship was also expected to be delivered within a span of 42 months, with subsequent deliveries of two ships per year.[21][22]

On 1 December 2020, CSL initiated the project's construction, with the steel-cutting of the first ASW-SWC vessel, Mahe (BY 523) at Kochi.[23]

On 31 December 2020, GRSE initiated the construction of the stipulated vessels under its agreement, with the steel-cutting ceremony of the first of the eight vessels it had been assigned with, at L&T's shipyard at Kattupalli, near Chennai.[24][25]

In July 2021, GRSE initiated the construction of two more vessels under its contract, with their respective steel-cutting ceremonies, while the keel of the first vessels (which had begun construction in December, 2020) was laid on 6 August 2021.[26]

CSL initiated the steel-cutting of the fourth and fifth vessels of the series, on 1 December 2021.[27]

The ASW-SWC vessels are equipped with one RBU-6000 anti-submarine rocket launcher and two sets of light-weight torpedo-tube launchers for launching anti-submarine torpedoes, (presumably the Advanced Light Weight Torpedo (ALWT)), for neutralizing enemy submarines.[7] The vessels are also equipped with mine rails, which enables the vessel to lay anti-submarine mines along the seabed.[2]

Aside from its primary anti-submarine weaponry, the vessels are also equipped with one small-calibre cannon (presumably the CRN-91 30 mm naval gun) and two 12.7 mm M2 "Stabilised Remote Controlled Gun" remote-weapon stations (RWS), equipped with optronic control systems.[2]

For detecting and intercepting hostile submarines, the ASW-SWC vessels are equipped with sophisticated sonar equipment, including a hull-mounted sonar (HMS) and towed low-frequency variable-depth sonar (LFVDS).[2]

INS Arnala launch

Being vessels primed for anti-submarine warfare (ASW), the ASW-SWC vessels were conceived to undertake multiple missions, including "search-and-attack-unit" (SAU) roles, low-intensity maritime operations (LIMO), subsurface surveillance in littoral-waters and coordinated ASW operations with maritime-patrol aircraft (MPA).[2] In addition, the vessels also possess the capability to interdict and destroy subsurface targets, within the vicinity coastal waters.[30] The vessels can also be deployed for search-and-rescue (SAR) missions in littoral waters.[31]

In their secondary role, the vessels will be able to lay mines, to protect domains of crucial importance, such as naval bases and commercial ports, from enemy submarines.[32]