G-5-class motor torpedo boat
The G-5 was a Soviet motor torpedo boat design built before and during World War II. Approximately 300 were built, of which 73 were lost during the war. Four were exported to the Spanish Republican Navy during the Spanish Civil War and others were transferred to North Korea after the war. Three were captured by the Finns, but only two were used before all three had to be returned to the Soviets after the Moscow Armistice in 1944. Design and development. The G-5 class was an improved and enlarged version of the s which were  derived from a design by Andrei Tupolev, a noted aircraft designer. It was intended to use Soviet-built engines and carry larger torpedoes than its predecessor. A prototype was designed and built by TsAGI ( or "Tsentralniy Aerogidrodinamicheskiy Institut", the Central Aerohydrodynamic Institute) in 1932–33. As its intended engines were not yet available two Isotta Fraschini engines were imported from Italy. Unarmed, and with a partial fuel load, it achieved a maximum speed of during its trials in the Black Sea during 1933 and the decision was made to place it into production. The G-5 was a single-step, hydroplaning design  with a whaleback upper hull. It was mainly built from duralumin which saved a significant amount of weight, but greatly complicated its use in service because of duralumin's susceptibility to galvanic corrosion in salt water. One captured Soviet torpedo boat commander said that G-5s could only be kept in the water for 5–7 days during the summer and 10–15 days during the winter before it had to be removed from the water and treated with anti-corrosion measures. The hull was divided into three compartments by two transverse bulkheads. The superstructure was very small to reduce top-heaviness, and  crewmembers could not stand up inside it. The G-5 was designed to use a version of the Mikulin AM-34 aircraft engine adapted for maritime use as the GAM-34. The two engines were fitted in the forward compartment of the hull. Each engine had its own transmission and drove a bronze propeller in diameter. The initial version of the GAM-34 was less powerful than planned at only and the initial Series 7 boats could only reach . However the minimum speed was which caused a great deal of trouble when trying to moor and when maneuvering in close proximity. The two torpedoes  were carried in troughs set into the rear deck in a manner derived from that used by the British WW I-era coastal motor boats captured by the Soviets during Russian Civil War. The torpedoes were shoved out the back of the trough by an arbor with a bell-shaped head that was activated by an explosive charge, but the torpedo motor was not activated until a wire trailing from the boat snapped, giving the boat time to turn away from the target. This launching system was very light, but it required additional training to properly aim the torpedo and  prior coordination when making massed torpedo attacks to prevent the boats from ramming each other or the torpedoes. The gun armament initially consisted of a single machine gun, but this was upgraded to a DShK machine gun in later models. Some later boats carried two DShKs although the mounts varied; some were placed in a tub in the forecastle, but others carried theirs in a rotating turret behind the superstructure, above the torpedoes. Some boats carried ROFS-82 or ROFS-132 rocket launchers in fixed mounts above and behind the wheelhouse. Production. Approximately 300 G-5s were built. 152 of the Series 7 , 8 and 9 boats were built between 1934 and 1936. 20 Series 10 boats were built in 1937, another 76 in 1938–39 and five in 1939–40. 39 Series 11 boats were built beginning in 1941 and production may have continued during the war. Variants. Series 7 Series 8 Series 9 Series 10 Series 11 Service history. On 22 June 1941, the day that the Germans invaded the Soviet Union, 254 G-5s were in service. The Baltic Fleet had 60, the Black Sea Fleet had 92, the Pacific Fleet had 135 and the Caspian Flotilla had six. During the war 73  were lost in action and 31 were scrapped after becoming unserviceable. By the end of the war in 1945 24 were in service with the Baltic Fleet, 134 were with the Pacific Fleet and six were still with the Caspian Flotilla. Many of the Soviet G-5s were used for different roles (landing units, transports, escorts, etc..) and saw a relatively low numbers of torpedo attacks against enemy targets. In Baltic Sea "TK-94" scored the locally significant sinking of Finnish minelayer . The only other known sinking caused by G-5s in Baltic Sea was the German minesweeper "M37". Likewise, few victories were  scored in Black Sea. During the Crimean Offensive, on the night of 27 April, three G-5s attacked and crippled the German submarine hunter "UJ-104" near Sevastopol. The Romanian gunboat opened fire with tracer rounds, enabling several more warships to locate the three boats and begin firing, resulting in one of the G-5s being sunk. "UJ-104" was towed to Sevastopol and later sunk by Soviet aircraft. Later, some G-5s sank the already damaged and abandoned Romanian minelayer "Romania". On 18 November 1942 the Finnish motor torpedo boat "Syöksy", the captured G-5 boats "Vinha" and "Vihuri", as well as a minelaying KM -boat, attacked Soviet ships in the harbour of Lavansaari. "Syöksy" sank the , although she was later raised and put back into service. Exports. Four boats were transferred to the Spanish Republican Navy during the Spanish Civil War, two continue in service after the war in the Spanish Nationalist navy until 1946. A number were transferred by the Soviet Union to North Korea after the end of the war.