Russian Navy's Kilo class submarine B-871 Alrosa completes trials.

According to information published by Tass on July 11, 2022, the Alrosa submarine of the Black Sea fleet returned to Sevastopol after the first stage of running trials held after an overhaul and upgrade.
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Russian Project 877 submarine Alrosa (Picture source: lenta)

The Russian submarine B-871 Alrosa is a diesel-electric Kilo-class submarine that joined the Soviet Navy in 1990 and was active with the Russian Navy's Black Sea Fleet.

B-871 Alrosa was laid down on 17 May 1988 at the Gorky shipyard. The submarine was launched on 10 September 1989 and commissioned on 1 December 1990.

The submarine was undergoing maintenance as of 2021. It is now the only original Kilo-class boat (Project 877) remaining with the Black Sea Fleet with all other traditional Kilos in the fleet having been replaced by the more modern "Improved Kilo" (Project 636.3) variant.

Alrosa has a length of 76.2 meters (250 ft 0 in), and a draught of 6.5 meters (21 ft 4 in). She can displace 2,300 tons surfaced and 3,040 tons full load submerged.

The Kilo-class submarine can reach an underwater speed of 20 knots (37 km/h), submerge to 300 meters, and have a cruising capacity of 45 days. The crew comprises 52 men, the underwater displacement is close to four thousand tons.

The class carries up to four Kalibr cruise missiles to strike at the surface (3M-54 and 3M-541) and ground targets (cruise missiles 3M-14) and has new electronic equipment.