Work on a larger Soviet torpedo boat began in 1935, with specifications issued in 1937 to improve on the G-5's endurance and armament. The wooden D-2 had poor stability, while the steel SM-3 developed hull cracks at speed. Neither entered series production, but both went into Black Sea service. The D-3 prototype was completed in 1939, with production ordered before launch and trials. Three GAM-34FN engines drove three shafts, but their unreliability led to substitution of the less powerful GAM-34BS. Stated top speed fell from 48 knots to 32. The 31-ton boat had a crew of nine, two 21-inch torpedoes, four depth charges, and 12.7 mm machine guns. Crews later fitted available 20 mm Oerlikon or 25 mm weapons to increase gun armament.
Chapter · 2:28:12-2:44:11
The D-3 and the cost of unproven propulsion
Soviet D-3 development sought a larger, better-armed boat, but prototype weaknesses and unreliable engines sharply reduced its intended performance.