EXPLAINED: How P17A frigate INS Nilgiri make Indian Navy more formidable

This achievement is the result of years of hard work by the Indian Navy, the Ministry of Defence and the Mazagon Dock Shipbuilders Limited, earlier called Mazagon Dock Limited (MDL).

The successful completion of the sea trial is a crucial step towards the incorporation of the INS Nilgiri into the Indian Navy. More trials will follow to ensure that the ship is operationally ready before it is officially commissioned into the navy.

The sea trial took place 80 months after the block erection started at MDL. This outstanding accomplishment places the INS Nilgiri as the quickest-built lead ship among the navy’s large, modern warships.

P17A frigates, also known as the Shivalik-class frigates, are a series of versatile stealth frigates being built for the Indian Navy. They are fitted with sophisticated weaponry, sensors and communication systems, turning them into a formidable asset for the navy to rule the waves.

Frigates and destroyers are two types of warships commonly found in a navy’s fleet. They are built to be agile and can be used to escort, and safeguard, larger ships from threats in the air, on the surface and under water.

A frigate is a smaller and lighter warship compared to a destroyer. Frigates are equipped with fewer weapons and ammunition compared to the larger and heavier destroyers, which have a wider range of firepower.

In terms of availability, frigates are more common globally. Almost every navy in the world has them. On the other hand, destroyers are less common, with only 14 countries possessing them, as indicated by the Global Fire Power Index, 2024.

Destroyers usually measure between 150 m and 160 m in length, while frigates are usually 130 m to 150 m long. Frigates are designed to be fast and highly manoeuvrable, with speeds generally exceeding those of destroyers. Frigates typically have a speed of around 30 knots (56 km/hr), whereas destroyers can reach speeds ranging from 20-30 knots (37-56 km/hr).

However, it is important to note that advancements in naval technology have reduced the speed gap between frigates and destroyers.

For instance, the Indian Navy’s Shivalik-class frigate is one of the fastest among its kind, capable of reaching speeds of up to 32 knots (59 km/hr). Other modern frigates can comfortably travel at speeds ranging from 26-30 knots (48-56 km/hr).

The agility of frigates allows them to quickly position themselves for attack, or evade potential threats when necessary. While destroyers have robust engines and sturdy hulls, they are not as nimble as frigates and cannot match their speed and manoeuvrability.

Frigates and destroyers are armed with advanced weaponry and defence systems. Frigates typically carry surface-to-air missiles (SAMs) for air defence, anti-submarine warfare (ASW) torpedoes to counter underwater threats and guns for surface combat.

Some frigates may also have vertical launch systems (VLSes) to launch long-range, anti-ship missiles (AShMs). These weapons ensure that frigates are well-equipped to handle various types of combat scenarios.

The P17A-Class Frigate project is a major investment in modernizing the Indian Navy. With a cost of approximately Rs 45,000 crore ($6 billion) for seven frigates, this collaborative effort involves Mazagon Dock Shipbuilders Limited in Mumbai constructing four frigates and Garden Reach Shipbuilders & Engineers (GRSE) in Kolkata building three.

As reported by Bharat Shakti, all frigates within the Nilgiri class are set to be commissioned by 2027.

The Nilgiri-class frigates are set to revolutionize the Indian Navy’s air defence capabilities, acting as the primary line of defence alongside the larger Kolkata and Visakhapatnam-class destroyers.

These frigates are equipped with the MF-STAR multi-function digital radar, known for its exceptional long-range detection and tracking abilities. With this advanced radar system, multiple targets can be simultaneously detected and tracked, providing early warning and engagement options against incoming threats.

While existing Indian Navy frigates and Delhi-class destroyers are armed with the Russian Shtil-1 surface-to-air missile (SAM) system, which has a range of 50 km, the Nilgiri-class frigates will carry the Barak 8 long-range SAMs.

Developed in collaboration with Israel, the Barak 8 system has a range of up to 100 km and can effectively engage various aerial threats, including aircraft, helicopters, anti-ship missiles and UAVs.

This elevates the Nilgiri-class frigates to the level of frontline destroyers in the Indian Navy, serving as the first line of defence within the Carrier Battle Group (CBG).

The state-of-the-art Shakti electronic warfare (EW) system, present in both the Visakhapatnam-class destroyers and the new Nilgiri-class frigates, plays a crucial role in enhancing their defence capabilities. The system operates in several steps to detect, intercept and neutralize electronic threats.

By effectively countering electronic threats, the Shakti EW system provides an extra layer of protection for the frigate. It helps safeguard the ship against guided munitions and enemy sensors, significantly reducing the risks posed by electronic-based attacks.

The Shakti system uses various sensors and equipment to identify the presence of electronic signals emitted by enemy sources. These signals can come from radar emissions, communication systems, or other electronic transmissions

Once detected, the system analyses the characteristics of these electronic signals to determine the type of threat and its location. This analysis provides valuable information for the next step in the process

The Shakti system can then employ a range of counter-measures to neutralize the identified threats. This may involve jamming techniques, which disrupt, or overwhelm, enemy electronic systems, preventing them from effectively tracking or targeting the frigate.

The Nilgiri-class frigates of the Indian Navy showcase remarkable technological advancements that enhance their operational capabilities.

With a focus on stealth design, these vessels utilize angular hulls and superstructures to reduce radar visibility, ensuring their survival in hostile maritime environments.

Powered by a sophisticated, combined diesel-and-gas propulsion system, these warships can reach speeds of up to 28 knots, enabling them to seamlessly integrate into Carrier Battle Groups and manoeuvre effectively in various naval scenarios.

Equipped with the BrahMos supersonic cruise missile system, these frigates possess formidable offensive capabilities, allowing them to conduct precise, and potent, strikes against both land and sea targets.

In terms of anti-submarine warfare (ASW), Nilgiri-class frigates are equipped with the indigenous HUMSA NG hull-mounted sonar system, enhancing their ability to detect and track submarines. They are also armed with torpedo launchers and ASW rocket launchers, further strengthening their capability to effectively counter underwater threats.

The author of this article is a Defence, Aerospace & Political Analyst based in Bengaluru.