Project 641 (NATO "FOXTROT") conventional attack submarines

58 (75 with other countries) submarines (1957-2014), B-series (random numbers). [wpcode id="47472"]

Development

To replace the first post-war ocean-going boats of Project 611 (NATO Zulu), in the late 1950s, TsKB-18 developed a new project, designated 641. The chief designer of the project was S. A. Egorov, then this post was occupied by Z. A. Deribin from 1958, with 1974 Yu. N. Kormilitsin. Project 641 was intended for the same tasks as Project 611: combat operations on long-range communications, mine laying, reconnaissance, anti-submarine operations. During their service, the boats earned high combat ratings, including four boats of the project (B-4 Chelyabinsk Komsomolets, B-36, B-59 and B-130) participated in Operation Kama during the Cuban Missile Crisis.

❮❮❮❮❮❮❮❮❮❮❮ ⚠ Note: This post is in writing. Completion expected later in 2024. ❯❯❯❯❯❯❯❯❯❯❯ The 'Foxtrot class' as known in NATO reporting name were a continuation of 1949 diesel-electric patrol submarines, a straithfoward design to replace not the already ageing "Whiskey" (Project 613) but the Zulu class which production was cut short as they suffered from structural weaknesses and harmonic vibration issues limited their operational depth as well as their submerged speed. The first keel was laid down in 1957, the lead boat B-94 being commissioned in 1958, last was completed in 1983, making these the longest-running conventional submarine production in USSR, before Project 877 (NATO "KILO") replaced them. A total of 58 were built for the Soviet Navy alone, all at Sudomekh, Admiralty Shipyard in Saint Petersburg. Additional ones were exported, plus Vjina made its own, for a grand total of 75 hulls, making it the second largest submarine class in the world after Project 613 boats.

Design of the class

Hull and general design

These subs were relatively large, more than Project 613 but and to Project 611 (Zulu class) boats, at 1,952 long tons (1,983 t) surfaced and 2,475 long tons (2,515 t) submerged versus 1,875 tons surfaced, 2,387 tons submerged. They measured also 89.9 m (294 ft 11 in) overall for a Beam of 7.4 m (24 ft 3 in) and a draft of 5.9 m (19 ft 4 in), versus 90 x 7.5 x 5.14m (295 ft) so they were slightly shorter, but broader and deeper, also much reinforced. The boat was divided by bulkheads into 7 compartments: 1st compartment: torpedo chamber, tubes and spares. Second Compartment: living compartment, with a wardroom. Below decks are batteries. third compartment - central post. 4th compartment - living compartment, with galley. Below decks are batteries. 5th compartment - diesel. 6th compartment - electric motor. 7th compartment - torpedo compartment. Framing: When designing the hull contours, great importance was attached to seaworthiness on the surface, which led to the presence of a pointed stem and sheerness in the middle part. The sonar and noise direction finder, located in the bow, were covered with fairings. The crew comprised 12 officers, 10 warrants, 56 seamen.

Powerplant

These submarines had three shafts, each with 6-bladed propellers, driven by three Kolomna 2D42M 2,000 hp (1,500 kW) diesel engines lated two three Electric motors, two 1,350 hp (1,010 kW) units and one 2,700 hp (2,000 kW) plus a 180 hp (130 kW) emergency backup auxiliary motor. As for performances, they were still average, at 16 knots (30 km/h) surfaced at best, 15 knots (28 km/h) submerged or 9 knots (17 km/h) when snorkeling. Range however was up to 20,000 nmi (37,000 km) at 8 kn (15 km/h) surfaced and 11,000 nmi (20,000 km) snorkeling or 380 nmi (700 km) at 2 knots (3.7 km/h) submerged with an endurance of 3-5 days submerged. Test depth was 246–296 m (807–971 ft). So they were the most capable submarines for oceanic missions outside SSNs, far cheaper and more reliable than Project 627 "kit" (November) boats

Armament

They were armed with ten torpedo tubes, as usual six in the bow, four in the stern for 22 torpedoes and unlike all previous classes, the Whidkey, Zulu and Quebec, were never designed to have deck guns, only torpedoes. The I641K for export differed in having six bow tubes with the same, but four stern tubes with 400 mm models, for export.

Sensors

763 to 264 had the "Flag" radar, MG-200 Arktika-M, Tuloma, MG-10 Kola, Svet-M sonars, Nakat ECM suite and the remainder the Kola-M as only upgrade. Same for the export I641K projects.

⚙ specifications
Displacement	1952/2475 tons
Dimensions	91.3 x 7.50 x 5.09
Propulsion	3 shafts 37D diesels/1 PG-102+2 PG-101 EM or 2D42 diesels, PG-101/102 EM 6000/5400 hp
Speed	16.8/16 kts
Range	30000 nm (8.1 kts)/400 nm (2 kts)
Armament	10x 533 TT (6 bow, 4 stern, 22-32 mines) or 6x533, 4x 400mm TT stern
Test Depth	250
Sensors	Flag radar, MG-200 Arktika-M, Tuloma, MG-10 Kola, Svet-M sonars, Nakat ECM suite
Crew	77

Gallery

Libyan Foxtrot, 1980s

RIAN archives, Project 641 boat berthed at anchorage

Ukrainian Foxtrot Zaporizhya

USS Charles P Cecil DD-835 shadowing B-36 off cuba, with a SP-5B Marlin flying above.

Preserved sub, berthed in Strood UK.

B-101 Regul

Current status

The cabin of the diesel-electric submarine B-107 of Project 641 is installed in the exposition of the Museum of the Russian Submarine Forces in St. Petersburg. B-413 was installed off the coast of Pregolya in the Museum of the World Ocean in Kaliningrad, its interiors have been preserved in their original form. The interiors were also preserved on the decommissioned INS Kursura S20, which is located in Visakhapatnam and turned into a museum. The decommissioned B-427 was sold in 1995 to Australia, and 3 years later it took its place as a museum in Long Beach, USA, and the B-440 - in Vytegra, Vologda region. The decommissioned B-39 is now an exhibit at the Maritime Museum of San Diego, USA. Submarine "Zaporozhye" - a submarine that was the only submarine of the Ukrainian Navy, after the annexation of Crimea by the Russian Federation in 2014, came under the temporary control of the Black Sea Fleet and is the only submarine of Project 641 that is still operational[2]. In March 2020, it was transferred to Inzhenernaya Bay and is being prepared for transfer to storage on Lake Donuzlav. The Sevastopol Military Historical Museum of Fortifications is ready to turn the boat into a museum exhibit.

Also, since they cured all the defects of the previous Project 611 boats, they were produced in mass without variants, the former were denied service for the most and instead used as tests boats for many experiments, leading to the Zulu I to Zulu V designs. Still, there was a sub-class, called Project I641 and I641K, not leading NATO to any denomination such as "FOXTROT II/III". So it was merely only soviet classification, for export subs to India, Libya and Cuba. Also, Project 641 led to 641B ASW submarine (NATO Tango class) improvised with the same components and surplus Project 651 (NATO JULIETT SSG) hull sections to gain about 50% more internal volume, hull diameter growing to 9m to accomodate a new larger sonar and plotting facilities for the equally new wire-guided torpedoes and three systems in all, bow array, sonar intercept set, underwater communications set. The Project 641 hull was also used as base for the Hotel class SSBNs, combining elements from Pr.627 (November) like the propulsion.

Exports

Wilk class (Project 641)

To Poland 1960: Wilk, Dzik

ORP Wilk and Dzik Two Project 647 boats, built in Sudomekh of Leningrad, pennant 292, 293, acquired in 1987-88 after the cancellation of more Kilo class orders to make up for a three subs fleet at alower cost. The clas comprised Wilk and Dzik. The former was fully upgraded in 1993. She also travelled 47000 nautical miles and dived 626 times. She was stricken in 2003. Dzik was scrapped in May 2005, but her conning tower was preserved at Gdynia.

Kalvari class (Project I641)

To India 1967-69: Kalvari, Kandhera, Karanj, Kursura

Soviet built Foxtrot-class boats, in Sudomekh from December 1967. Identical to the original boats. Four in service from 1967 to 2001. Four additional variants, later Foxtrot type as Vela class (see below). INS Kursura has been preserved museum on Ramakrishna Mission Beach, Visakhapatnam, and the sails of INS Kalvari is on display at the Visakhapatnam city museum. The one from Khanderi is also on display. Specs as the original Foxtrot class: Displacement 1,957t/2484t for 91.3 x 7.5 x 6 m, 3 shafts diesels 6,000 hp 16.6/15.9 Knots, 250-280 m dive, Radar Nakat M, Sonar Feniks M, Artika, hercules, interceptor sonar, 10 x 533 mm TTs (6 bow, 4 stern).

Vela class (Project I641K)

To India 1973-74 Vela, Vagir, Vagli, Vagsheer

First started on early 1972, the last completed on 26 December 1974. Specifically they had 22 SET-65E/SAET-60 torpedoes or 44 mines in lieu of torpedoes. In service until 1997 for INS Vagsheer, 2001 for INS Vagir and 2010 for the remainder. One is waited to be converted as museum ship.

Al Fateh class (Project I641K)

To Libya 1976-82: Al Fateh, Al Ahad, Al Hunain, Al Mitraga, Al Badr, Al Khyber

Info to come

725 class (Project I641K)

To Cuba 1982-84: 725, 727, 729