The Indian Navy has deployed the sixth and final submarine of the P-75 Scorpene Project, alongside a stealth frigate and a guided missile destroyer. While this marks a significant achievement, the Indian Navy’s submarine fleet still lacks the Air Independent Propulsion (AIP) technology. In contrast, the Chinese-manufactured Hangor class submarine is on track to be integrated into the Pakistan Navy as planned.

Currently, the Indian Navy does not possess any AIP-equipped submarines, whereas the Pakistan Navy operates three French Agosta-90B submarines (PNS Khalid, Saad, and Hamza) that utilize AIP technology.

According to the latest developments, the Hangor submarines are anticipated to be commissioned into the Pakistan Navy by the late 2020s to early 2030s. Once operational, these submarines will enhance the Pakistan Navy’s capabilities, bringing its total of AIP-equipped vessels to 11.

Despite financial constraints, Pakistan is striving to keep pace with the Indian Navy’s capabilities, ship for ship. As the Indian Navy’s sole operational port in the region is being developed into the largest naval base east of the Suez Canal, Pakistan is also intensifying its efforts to establish one of Asia’s largest naval fleets. This includes expanding its surface fleet to 50 warships and a subsurface fleet of 11 submarines. Among the 50 surface vessels, 20 are projected to be significant assets such as frigates and corvettes.

Admiral Naveed Ashraf, the Chief of the Naval Staff of the Pakistan Navy, informed Chinese state media that the development of four submarines is on track according to the established schedule.

He emphasized that the Hangor-class submarines will greatly bolster Pakistan’s naval capabilities through enhanced stealth, maneuverability, and firepower, enabling the Navy to conduct a diverse array of operations effectively.

“The project is advancing as planned. We anticipate that these submarines will soon be integrated into the Pakistan Navy fleet,” Ashraf stated.

In December 2021, the steel cutting ceremony for the fifth Hangor-class conventional submarine took place, marking the first such submarine to be constructed in Pakistan. This initiative will provide Pakistan with critical experience in the production of advanced modern submarines.

The Hangor submarines are variants of the S-26, which are based on the Chinese Yuan class but modified for export purposes. Several design alterations have been implemented compared to the standard S-26 model.

The Hangor class submarine has a larger displacement of 2,800 tons, compared to the S-26’s 2,550 tons, although it features a slightly shorter hull (76 m versus the S-26’s 77.7 m). Both classes share the same payload capacity of six torpedo tubes and utilize a Stirling-based Air-Independent Propulsion (AIP) system.

Initially, the S-26 submarines were equipped with the German MTU 12V 396 SE84 diesel engine; however, the German government reportedly restricted export licenses for this engine. Consequently, the Pakistan Navy opted for the Chinese CHD-620 diesel engine, which resulted in delays to the program.

These submarines feature cutting-edge sensors and contemporary weaponry, which marginally shifts the tactical advantage towards Pakistan. The diesel attack submarines are in line with the Pakistan Navy’s strategy of offensive sea denial, emphasizing the use of submarines and missile-equipped maritime patrol aircraft in naval engagements.

AIP-equipped conventional diesel-electric submarines (SSK) represent a middle ground between nuclear-powered vessels and non-AIP SSKs. This technology enables an SSK to remain submerged for 10 to 14 days without surfacing to recharge its batteries, thereby minimizing the risk of detection. In contrast, other SSKs typically can operate underwater for about 48 hours. The fuel-cell-based AIP system is distinctive as it produces its hydrogen supply onboard.

The AIP significantly extends a submarine’s underwater endurance between battery charges by three to four times, thereby decreasing its chances of being detected.

Slow Advancement of Indian Submarine Fleets Towards AIP

With the addition of INS Vaghsheer, the Indian submarine fleet now comprises 17 conventional submarines. The Scorpene Class submarines are set to be upgraded with a domestically developed AIP system during the major refit of the first submarine in this class, INS Kalvari.

This retrofitting process will involve splitting the operational submarine in half to incorporate a new AIP section, which will increase both its length and weight. The French shipbuilder Naval Group will provide support for this intricate operation.

The technology will undergo additional testing before being integrated into the remaining Scorpene-class submarines. Experts have indicated that incorporating new technology into a weapons platform may hinder operational readiness, as repairs are expected to take a minimum of one year.

In addition to the six newly constructed submarines, the others are over 30 years old and nearing their decommissioning timeline. India’s older Shishumar (HDW) class and Sindughosh (Kilo) class submarines are experiencing challenges with spare parts due to the ongoing conflict in Ukraine.

The Indian Navy is actively seeking a foreign partner to develop AIP-equipped submarines under Project-75I. Field evaluations have already been conducted on systems proposed by Germany and Spain, but a final decision on the contract has yet to be made.

Given that it took 11 years for the first Scorpene-class submarine to join the Indian Navy after the agreement was signed, the submarines under Project-75I are projected to take at least a decade before they become operational.

Pakistan-China Cooperation

Encouraged by China, Pakistan has recognized the significance of the Western Indian Ocean, leading to an emphasis on naval modernization.

In addition to the Hangor-class submarine, Admiral highlighted the acquisition of four Type 054A/P frigates from China, which have significantly enhanced the country’s combat capabilities.

“The addition of Type 054A/P frigates to the Pakistan Navy has strengthened our combat capabilities and improved operational flexibility, ensuring these vessels will be central to the Pakistan Navy’s fleet in the years ahead.”

The final two frigates were handed over in May 2023. The Type 054A/P represents one of the most advanced multi-role frigates from China, featuring cutting-edge weaponry and sensors, including CM-302 surface-to-surface missiles and LY-80 surface-to-air missiles. Additionally, it is equipped with an Advanced Anti-Submarine Warfare suite and a Combat Management System, allowing vessels of this class to function effectively in multi-threat environments. The Pakistan Navy is the inaugural customer for these frigates.

According to the Chief of the Pakistan Navy, the Type 054A/P vessels are designed to operate in complex threat scenarios and have been seamlessly integrated into the operations of the Pakistan Navy. The F-22P guided missile frigate, constructed in China and renamed PNS Zulfiquar by the Pakistan Navy, executed Operation Himalayan Spirit in the North Arabian Sea in October 2024, resulting in the seizure of 1.3 tons of narcotics.