Guardians of India's Maritime Frontiers
A recent report highlighted the Nilgiri, Sandhayak and Arnala classes of warships as representing three distinct pillars of India's naval combat capability: frontline surface combat, hydrographic survey, and coastal anti-submarine warfare.
The Nilgiri class (Project 17A) comprises stealth guided-missile frigates built to succeed the older Shivalik-class (Project 17) frigates.
The Sandhayak class consists of large hydrographic survey vessels tasked with mapping the seabed and generating navigational charts.
The Arnala class consists of shallow-water anti-submarine warfare (ASW) craft designed for coastal underwater surveillance and mine-laying support.
All three classes are designed by the Indian Navy's in-house Warship Design Bureau and built at domestic shipyards, reflecting the indigenous shipbuilding push under the Aatmanirbhar Bharat framework.
Project 17A — Nilgiri-Class Stealth Frigates
Project 17A is the Indian Navy's follow-on programme to Project 17 (Shivalik class), producing seven stealth guided-missile frigates with reduced radar, thermal and acoustic signatures. The class is being built jointly by Mazagon Dock Shipbuilders Limited (MDL), Mumbai and Garden Reach Shipbuilders & Engineers (GRSE), Kolkata, split four ships to MDL and three to GRSE.
Key Details
- Displacement approximately 6,670 tonnes; length about 149 metres; CODAG (Combined Diesel and Gas) propulsion giving a top speed of around 28 knots.
- Armament includes 8 BrahMos supersonic cruise missiles, 32 Barak-8/MRSAM surface-to-air missiles, a 76 mm main gun, AK-630 close-in weapon system, torpedoes, and indigenous anti-submarine rocket launchers.
- Over 75% indigenous content, involving more than 200 MSMEs, built using Integrated Modular Construction — cited as a flagship example of the Aatmanirbhar Bharat (self-reliance) push in defence production.
- Lead ship INS Nilgiri; the class name follows the Navy's tradition of naming frigates after mountain ranges (as with the earlier Nilgiri and Shivalik classes).
The Nilgiri class represents the Navy's principal indigenous frontline surface combatant, replacing an earlier generation of imported/part-imported frigate designs and demonstrating the maturity of India's warship design and construction ecosystem.
Sandhayak-Class Survey Vessels (Large)
The Sandhayak class is a four-ship series of Survey Vessel (Large) — SVL — built to replace the Navy's earlier hydrographic survey fleet. These vessels conduct coastal and deep-water hydrographic surveys, oceanographic data collection, and search-and-rescue operations, and are essential to producing the nautical charts used for safe navigation and maritime boundary delimitation.
Key Details
- Approximately 110 metres in length; the class comprises INS Sandhayak, INS Nirdeshak, INS Ikshak and INS Sanshodhak.
- Equipped with autonomous underwater vehicles (AUVs) and remotely operated vehicles (ROVs) for seabed mapping.
- Designed by the Warship Design Bureau and built domestically, continuing the Navy's self-reliance in specialised, non-combatant vessel classes.
Hydrographic survey capability underpins India's maritime domain awareness, EEZ (Exclusive Economic Zone) charting, and support to both naval operations and commercial shipping — a "force multiplier" role distinct from combat frigates.
Arnala-Class Anti-Submarine Warfare Shallow Water Craft
The Arnala class is a series of shallow-water ASW craft intended to replace the ageing Abhay-class corvettes, filling the gap in littoral (coastal) anti-submarine and anti-mine warfare that larger frigates and destroyers are not optimised for.
Key Details
- Approximately 77–78 metres in length, displacing around 900 tonnes; propelled by waterjets for shallow-water manoeuvrability.
- Equipped with lightweight torpedoes, rocket launchers, mines, naval guns, and shallow-water sonar; capable of surveillance and search-and-attack missions up to 200 nautical miles from shore.
- Lead ship INS Arnala; designed for low-intensity maritime operations, coastal ASW, and mine warfare — roles critical to countering sub-surface threats near India's coastline.
Coastal ASW craft such as the Arnala class address a distinct internal/coastal security requirement — detecting and neutralising submarine or underwater threats close to shore, complementing the blue-water role of Nilgiri-class frigates.
- Nilgiri class (Project 17A): 7 ships planned; ~6,670 tonnes displacement; ~149 m length; over 75% indigenous content.
- Sandhayak class: 4 survey vessels; ~110 m length.
- Arnala class: shallow-water ASW craft; ~900 tonnes displacement; ~77–78 m length; operational range up to 200 nautical miles from shore.
- All three classes are designed by the Indian Navy's Warship Design Bureau and built at Indian shipyards (including Mazagon Dock and GRSE), reflecting the indigenous defence shipbuilding programme.